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THE SOUTH AFRICAN MECHANICAL ENGINEER

VOL 61

June 2011

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THE SOUTH AFRICAN MECHANICAL ENGINEER

VOL 61

June 2011


AN ENGINEER’S VIEW

Managing SAIMechE as a Business Members will have recently received their invoices for the subscriptions to the Institution for 2011-2012 financial year. You may wonder how the rates are created for these. I have been on Council for many years primarily on the communications committee and specialist group roles and have also been very involved in training issues being the CPD functions and the new Professional Development Programme (PDP). I thought it worthwhile to reflect on the challenges that have faced the role of Council over this time.

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or as far back as I remember the debate as to whether the Institution should appoint a CEO or Director has taken place. Could we afford to have one or could we afford to continue without one? Well, as you all know, in mid 2007 Council decided to take the bold and calculated step and seek a CEO, and in October 2007, Vaughan was appointed. So we have sufficient experience now to evaluate whether the decision was worthwhile.

In my own view, and this would I am certain be supported by the current Council Chris Reay and many members, it is quite amazing Chairman of the Working Committee: Communications that it took so long to have this function (SA Institution of Mechanical established. How we managed on the Engineering) voluntary basis alone is only now showing. Continuity of objectives and projects were always in jeopardy. Appointing a full time CEO to drive and manage the administration and the projects that have been decided by Council was the best decision Council have made in 109 years!

Critical issues

Council is now using its limited time to address and debate and decide on critical issues. We can see and feel the active participation in important matters of mechanical engineering. We have a very pleasant office that works efficiently and happily and boardroom in Bruma opposite the ECSA office (Anisa and Lynn) and where any member is always welcome. The based Events Department and Branch office (Linda and Carey) are set up in the offices in Kloof, Durban, and the Western Cape activities are in the capable hands of Bev. The recent Mpumalanga Branch is starting to show how it made sense to establish this entity.

The best decision Council have made in 109 years! However, where we are seeing the impact of the proper structuring of the administration is in the involvement and visibility of SAIMechE in critical issues such as Identification of Engineering Work (IDoEW), the PDP, the strategies to address the scarce skills dilemma

and the participation in various committees and conferences that affect the engineering profession, and in particular the new ECSA Candidate Phase Training committee. Then there is the much improved control and financial management of all the administrative functions including the expanding training events schedule and validation of CPD courses, Let’s come back then to the issue of subscription rates. Council has formulated a budget model that ensures that the strategies, objectives and operations must run properly and can only be done with a balanced and competent set of office bearers. Accordingly this budget ensures that the cost of running this structure is covered by the members’ subscriptions and with these all operating to plan, the Institution will accrue surplus funds from the various activities that are designed to benefit the members.

Each one get one

Every member will be affected by the era of IDoEW and many by the revised Candidate Phase requirements for registration. The Institution will be seeking Mentors who can be drawn from our semi or retired group on a paid basis. There are plans in place to have industry recall many of the older engineering resources to assist with the scarce skills and mentoring issues. The CEO is keeping a close eye on the changing SETA situation. If you are registered with ECSA, you can become a member of SAIMechE at almost the same fee due to the discount given by ECSA to registered members of the voluntary associations. Registration will soon become the norm for any defined work type. Think about this: if every existing member recruited one new member, we could virtually halve the subscriptions rate. So the message is : Each one get one. Hopefully none of the targets will have the philosophy of Groucho Marx who once said he would not join a club that would have him as a member!

THE SOUTH AFRICAN MECHANICAL ENGINEER

VOL 61

June 2011

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VOL 61

June 2011


June 2011  VOLUME 61  NUMBER 6

Featured on the cover: Bearing Man Group, Telephone: (031) 576 6288, Fax (031) 576 6581, Email : rouffe@bmgworld.net, Website : www.bmgworld.net

Contents Monthly Column

27 Power Generation News

8 Making Waves

Bearings and Lubrication

Cover Story

29 Special Lubricants 31 Optimizing Bearing Performance

11 Heavy Duty Bearings

Copyright

All rights reserved. No editorial matter published in “SA Mechanical Engineer” may be reproduced in any form or language without written permission of the publishers. While every effort is made to ensure accurate reproduction, the editor, authors, publishers and their employees or agents shall not be responsible or in any way liable for any errors, omissions or inaccuracies in the publication, whether arising from negligence or otherwise or for any consequences arising therefrom. The inclusion or exclusion of any product does not mean that the publisher or editorial board advocates or rejects its use either generally or in any particular field or fields.

Pipes, Pumps and Valves

Regulars

13 Inside the Dome Valve 15 The Thick Stuff

6 Institution News

Computers in Engineering 17 Wheel Force Transducer 21 Let FEA Work for You

POWER GENERATION TODAY

3 An Engineer’s View 20 SAINT 28 Nuclear Institute (SA Branch) 36 Market Forum 46 On the Move

23 PVB Film: The Alternatives to Ethylene-Vinyl Acetate (EVA)

The monthly circulation is 4 242

Official Publication of THE SA INSTITUTION OF MECHANICAL ENGINEERING

Produced by: PROMECH PUBLISHING, P O Box 373, Pinegowrie, 2123 Republic of South Africa Tel: (011) 781-1401, Fax: (011) 781-1403 Email: editorial@promech.co.za Website: www.promech.co.za

and endorsed by:

Managing Editor Susan Custers Editor Kowie Hamman Advertising Louise Taylor Circulation Catherine Macdiva DTP Zinobia Docrat, Yolanda Flowerday, Lilian Kemp Disclaimer PROMECH Publishing and The South African Institution of Mechanical Engineering as well as any other body do not take responsibility for the opinions expressed by individuals. Printed by: Typo Colour Printing, Tel: (011) 402-3468/9

 CORROSION INSTITUTE OF SA  SA PUMP MANUFACTURERS ASSOCIATION  SA VALVE AND ACTUATORS MANUFACTURERS ASSOCIATION  THE SA INSTITUTE OF TRIBOLOGY  NUCLEAR INSTITUTE  SA INSTITUTE FOR NON-DESTRUCTIVE TESTING  NATIONAL SOCIETY OF BLACK ENGINEERS  INSTITUTE FOR CERTIFICATED MECHANICAL AND ELECTRICAL ENGINEERS  SOUTH AFRICAN ASSOCIATION OF CONSULTING ENGINEERS  ASSOCIATION OF SOCIETIES FOR OCCUPATIONAL SAFETY AND HEALTH

THE SOUTH AFRICAN MECHANICAL ENGINEER

VOL 61

June 2011

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THE SA INSTITUTION OF MECHANICAL ENGINEERING

Council 2010/2011 Office Bearers

President .................................................. G Barbic (George) Vice President .............................................. D Findeis (Dirk) National Treasurer ............................... KK Nyangoni (Kudzai)

Branch Chairpersons

Central ...................................................... M Cramer (Mike) Eastern Cape ................................................ W Rall (William) KwaZulu/Natal ......................................... M Black (Malcolm) Mpumalanga Highveld.............................. L Odendaal (Louis) Western Cape ......................... Prof B Collier-Reed (Brandon)

Portfolios:

Communications/Strategic Planning/ Specialist Group..................................................CD Reay (Chris) Education - Universities................Prof B Collier-Reed (Brandon) Education: Universities of Technology............... E Zawilska (Ewa) Membership .................................................... E Zawilska (Ewa) Professional Development Programme..........M Black (Malcolm) Technology Programme ................................. SZ Hrabar (Steve) To be confirmed....................................................A Roos (Andre) To be confirmed.........................................G Bartholomew (Bart)

Chief Executive Officer: Vaughan Rimbault National Office Manager: Anisa Nanabhay

PO Box 511, Bruma, 2026 Tel: (011) 615-5660, Fax: (011) 388-5356 Email: info@saimeche.org.za Website: www.saimeche.org.za Membership: Central, Eastern Cape & KZN: membership@saimeche.org.za Membership: Western Cape: saimeche.wc@vodamail.co.za

Company Affiliates Alstom Power Service SA Babcock Africa Limited Bateman Engineered Technologies Bosch Projects Fluor SA GEA Air-cooled Systems Hansen Transmissions SA Hatch Africa Howden Power Howden Projects Industrial Water Cooling

Osborn Engineered Products SA Rotek Engineering RSD a division of DCD-Dorbyl S.A.M.E Water Sasol Technologies SEW Eurodrive Siemens SNC-Lavalin SA Spicer Axle SA Spirax Sarco SA Thyssenkrupp Engineering Transvaal Pressed Nuts & Bolts Ultra-Flow Engineering Services

MBE Minerals (SA) (Pty) Ltd (previously KHD Humboldt Vital Engineering Wedag SA) Weir Minerals Africa Megchem Eng & Drafting Services

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Winder Controls

THE SOUTH AFRICAN MECHANICAL ENGINEER

VOL 61

SAIMechE & IMechE Working Together

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wo great institutions have once again rekindled an old flame in order to work together in promoting mechanical engineering at both a local and international level.

The Institution of Mechanical Engineers (IMechE) and the South African Institution of Mechanical Engineering (SAIMechE) have held an agreement of co-operation between each other for a number of years – this agreement was last signed in October 1999 but remains in operation today. And for some time very little interaction has taken place……until now. We are therefore pleased to announce that all IMechE members residing in South Africa can now participate in joint SAIMechE branch events across the country, which include technical presentations, cocktail functions and year-end dinners. There is no better reason to get involved in order to network with other engineers and discuss mechanical engineering on an international level. A homepage for IMechE members residing in South Africa has been created on SAIMechE’s web platform (www. saimeche.org.za), and IMechE members are encouraged to register on the site and joint the IMechE group and use the facilities. Credit must be given to Vaughan Rimbault (CEO of SAIMechE) and David Blackwood (IMechE Middle East & Africa YM Representative & SAIMechE member) for getting this initiative off the ground. Speaking to both of them, they share the opinion that only good things can come from utilising the mutual agreements between the two institutions. The next step is to review, update if necessary and re-sign the agreement of co-operation which lapses in 2013. And for all our SAIMechE members who are visiting London on business – why not pop in to IMechE HQ at 1 Birdcage Walk, Westminster, to visit the library or to make use of Vaughan Rimbault its facilities?

June 2011


THE SA INSTITUTION OF MECHANICAL ENGINEERING

IPUC 2011 - International Pump User Conference 13-14 September 2011, MTN Expo Centre

Conference Theme: Adapting pumping systems for an era of limited and expensive power In the past pumping systems were designed around abundant and cheap electricity - now the power supply is limited, unreliable and increasingly expensive. IPUC 2011 brings together leading local and international experts to present the latest developments from around the world and show how to modify existing systems without incurring a crippling financial burden. Keynote speakers this year include: • Andrew Etzinger: Eskom IDM. The situation in South Africa, how big is the crisis, and what is currently being done about it • Steve Schofield: Technical director BPMA. Standards and directives being developed Europe and USA • Larry Bachus: ‘The Pump Guy’. Common pumping problems he has encountered in his travels around the world • Harry Rosen: National Expert UNIDO Industrial Efficiency project. Impact of the pump efficiency project in this country Technical papers and case studies on the following topics: • Various funding mechanisms available in South Africa • Latest developments in water and slurry pump design • Sustained pumping systems efficiency in wastewater pumping • Motor efficiency testing • Pumping issues around acid mine drainage • System assessment of a cooling water system in an industrial plant • Energy efficiency opportunities in coal washing plants • Optimising a bulk water supply pump station • Savings opportunities in agriculture Post Conference Workshop - Pumping System Assessment - 15 September Delegates will learn how to carry out a detailed assessment of the efficiency of the pumping systems at their own plant. The workshop will be led by a panel of visiting and local experts and will consider both assessment techniques and funding options. For further information and sponsorship opportunities contact: Veriza Smith: 011 325 0686 / 083 553 9895 or info@ipuc.co.za

SAIMechE SEMINAR EVENTS Due to recent requests, SAIMechE has decided to reintroduce its former popular Seminars at which several experts will speak on various sub-topics at each event. Thus we have pleasure in announcing the following forthcoming events. East Rand

Durban

Cape Town

Title

Code

Date

Code

Date

Code

Date

Mechanical Power Transmission

EMT11

19 Jul 11

AMT11

12 Jul 11

CMT11

5 Jul 11

Bearings

EBE11

16 Aug 11

ABE11

3 Aug 11

CBE11

30 Aug 11

Electricity, Water & Effluent

EEW11

6 Sep 11

AEW11

13 Sep 11

CEW11

27 Sep 11

A registration form and full terms and conditions may be obtained from Carey Evans on E-mail: carey@saimeche.org.za or Tel. 031 764 7136. Also, detailed individual event programmes are available from Carey.

Notice of SAIMechE Annual General Meetings (2011) 120th National AGM Note date changed!!! Wednesday, 3 August 2011 Time: 18h00 Venue: Engineering Council, Waterview Building South, Bruma, Johannesburg RSVP: Register online at www.saimeche.org. za (then go to the Calendar) or email: info@saimeche.org.za.

Central Branch AGM The Central Branch AGM will be held on Tuesday 28 June 2011. The keynote speaker is Andy Crowe, Chairman of the Smoke Ventilation Association with the topic: “Are we playing with fire? Smoke Control and the new SA Building Regulations” Time: 18h00 for 18h15 Venue: Engineering Council, Waterview Building, 2 Ernest Oppenheimer Ave, Bruma RSVP: Register online at www.saimeche. org.za (then go to the Calendar) or email central@saimeche.org.za.

Western Cape Branch AGM and Dinner Thursday, 30 June 2011 Time: 18h00 Venue: TBA saimeche.wc@vodamail.co.za

Technology Olympiad AGM Will be held on Tuesday 28 June 2011 (before the Central Branch AGM). Time: 18h00 for 18h15 Venue: Engineering Council, Waterview Building - 2 Ernest Oppenheimer Ave, Bruma, Johannesburg olympiad@saimeche.org.za .

Eastern Cape Branch AGM Will be held on Thursday, 23 June 2011. Full details to be communicated to members of that branch shortly.

Mpumalanga Highveld Branch AGM Wednesday, 20 July 2011 Time: 18h00 Venue: Lake Umuzi, Boesies Conference Centre mhbranch@saimeche.org.za

Invitations with full details of the above AGMs will be distributed to members shortly, including presentations and guest speakers, where applicable. Please contact the relevant office directly for more information. Alternatively contact the National office. Snacks and refreshments will be served at each of the above AGMs.

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June 2011

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MONTHLY COLUMN

A new diving fin, designed and entirely made in South Africa is making waves around the world, not only in terms of its looks, but also because it’s a comfortable fit delivering efficient power from military to leisure diving. And all this with only one pair of fins.

Making Waves

T

here are only two pieces of equipment that are ‘must haves’ for any diver; a good mask that fits well and a pair of fins that suits the diving style as well as the diver’s anatomy. Just like golf clubs, a pair of fins should be tailored to the diver and the diving conditions and so, one set of fins is not always perfect for all divers on every type of dive.

Shortcomings

The new diving fin, designed and entirely made in South Africa

The new fins that are kicking up a storm in diving circles across the globe come close to being ideal for all people under all diving conditions. “SA Mechanical Engineer” visits inventor Rhys Couzyn of Scuba Equipment Africa in Sandton to see for themselves. “Conventional fins come in a variety of types so that divers can choose fins that are suitable for their own personal type and style of diving,” says Rhys. “However, each type has certain drawbacks. If you choose a stiff fin, it requires harder work, but you get more speed and power. If you take a soft split fin, for instance, you’re sacrificing power, but have far better comfort and efficiency.”

Has won several design awards locally and overseas with diving magazine reviews praising it as revolutionary

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Rhys Couzyn of Scuba Equipment Africa

Blood, sweat and tears

Rhys has been involved in the diving business since his youth and the fact that each set of fins has a shortcoming has always bugged him, so he started delving into the physical requirements of the ‘perfect’ fin. Today his Seawing Nova fins are on everyone’s lips and the design, marketed under the international brand Scubapro, has won several design awards locally and overseas with diving magazine reviews praising it as revolutionary. Developing the new design wasn’t easy though. It cost six years of blood, sweat and tears to consider

June 2011


MONTHLY COLUMN

It cost six years of blood, sweat and tears to consider the hydrodynamics of a fin that would mechanically deliver optimum power in all diving conditions

the hydrodynamics of a fin that would mechanically deliver optimum power in all diving conditions. “The original concept considered all the shortcomings of fins available on the market, but when I presented the design to an Italian fin engineer he shot it down as too revolutionary and not marketable,” Rhys says with a wry smile. “We then started developing it locally anyway because we were confident that the design had merit.

Design criteria

“Main considerations were to improve on speed, acceleration, efficiency in terms of thrust to effort ratio and manoeuvrability, but at the same time it had to be comfortable and not too stiff, tiring the average diver too quickly,” elaborates Rhys. “We also had to look at durability and ergonomics, to make sure it would last a lifetime and be simple to put on, take off and pack. Because the fin actually works differently from other fins, we wanted something that looked different from everything else on the market. It’s hard to sell a radical new technology if your product looks just like every other fin on the shelf!

The Seawing Nova has an articulated joint, much like the tail joint of a whale or dolphin “We incorporated modern materials and the latest innovations in hydro-dynamic design to achieve the power, acceleration and manoeuvrability of traditional paddle fins, while still having the comfort, efficiency and effortless speed of conventional split fins,” adds Rhys. “Instead of the gradual curve of a traditional fin, the Seawing Nova has an articulated joint, much like the tail joint of a whale or dolphin which allows the blade to pivot. The entire blade is now able to generate thrust with less drag compared with other fins.

It’s all in the blade

“With traditional paddle fins, the harder you kick, the more the blade bends. The result is that soft fins achieve the ideal 45° angle when kicked gently, but they tend to over-bend and lose thrust when kicked hard. Stiff fins achieve the desired 45° angle when kicked hard but remain too flat and therefore

The final mould for the fin now manufactured in South Africa

inefficient when kicked gently. Both require the diver to compromise. “The ‘dead’ section between the foot pocket and the blade of a traditional fin generates drag but not thrust,” explains Rhys. “We removed it which means that water is free to flow cleanly onto the working section of the blade thereby reducing drag while increasing thrust. Even the aerodynamics of aircraft were researched which led to the ‘Dihedral’ design on the Seawing Nova. “As the diver kicks harder, our fin’s wings arc upwards. It’s similar to what you would see on a passenger aircraft with upswept (dihedral) wings as this design automatically ‘self-rights’ itself. On the Seawing Nova, this increases high-speed stability while also reducing drag,” explains Rhys.

The team

While Rhys’s brother Nolan, a CAD designer, helped translate Rhys’s early sketches and models into a 3D computer model, Rhys then enlisted the services of industrial designer and qualified Dive Master, Glyn Ogden, to help make the working concept a reality. Rhys, Glyn and another industrial designer, Mark Trevethan worked together over the last few years of the project to fine-tune the performance and aesthetics of the design.

A variation of the new fin

The fins are now manufactured in Johannesburg for the world market. “I took a chance by moulding Scubapro’s logo onto the first prototypes before they had even seen it, but fortunately they liked the design and immediately took it on as a new product,” Rhys says in conclusion. “Since we could manufacture the product in South Africa at a competitive price against the company’s other international manufacturers, we also landed the manufacturing contract.” Rhys Couzyn, Scuba Equipment Africa. Tel: (011) 444-6563, Email: rhys@scubapro.o.za

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June 2011

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THE SOUTH AFRICAN MECHANICAL ENGINEER

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June 2011


COVER STORY

Heavy Duty Bearings For the last seven years BMG – Bearing Man Group – has been the exclusive distributors of QM Bearings and couplings throughout Southern Africa. BMG supplies the full range of QM Blue Brute spherical roller housed units and Quick Flex couplings to diverse industries.

A

North American based manufacturer of housed bearings, QM has over 40 years experience in the supply of housed bearings for demanding applications in heavy process industries like paper, forestry, mining and steel.

Missing segment

In the last quarter of 2010, QM was acquired by the Timken Company. This transaction has enabled the Timken Company to diversify and broaden its product range by offering an established quality product, with an impeccable reputation. The Timken Company now distributes a ball, spherical and tapered roller housed bearing product range in both metric and imperial dimensions.

Not simply a supplier of product, which many housed bearing suppliers have become “These imperial housed tapered roller bearing units were the missing segment from BMG’s housed bearing product portfolio,” says Rouff Essop, divisional

manager, bearings division, BMG. “The addition of this product range by one of our key supply partners allows BMG to better satisfy customer demands. “The investment made by the Timken Company in QM will ensure that this product line will continue to be developed. This acquisition also means Timken will maintain its position as a solutions provider of housed bearing units and not simply a supplier of product, which many housed bearing suppliers have become.” The introduction of the Timken branded QM product is some way off, which means a delay in the introduction of these housed tapered roller bearing units to the South African market. In the interim, BMG will continue to support the QM product range from its own extensive inventory. The bearings division has expanded its product offering by introducing and now stocking the Timken housed tapered roller bearing product range.

Support

Extensive inventory planning and stock profiling will enable BMG to adequately support the new Timken branded QM product range once it has been launched locally. The company intends to distribute the full range of housed spherical and tapered roller bearings throughout Southern Africa. Typical applications for these units include aggregate and mining operations, steel industries, oil and gas, automotive, agriculture and power generation. This range is also used in treatment facilities, saw mills, food and beverage, as well as pulp and paper. The QMSN series, which is designed for efficient performance and extended service life in demanding environments, is manufactured with cast steel housings that have three times the tensile strength of cast iron housings. This is an important advantage in applications where there are heavy loads and vibration. The robustness of these spherical roller housed units means that the bearing can be replaced into the same housing many times, which offers substantial cost savings.

Running hot

There are three standard sealing options available – the triple lip nitrile rubber series, the triple lip viton rubber series and teflon labyrinth seals.

BMG supplies the full range of QM Blue Brute spherical roller housed units and Quick Flex couplings to diverse industries

Triple lip nitrile rubber units have a standard sealing arrangement to offer maximum protection for most conditions, including moisture and dirt. The seal has a light to medium contact pressure, which allows excess grease to purge under the lips, preventing the housing from becoming over packed with grease. Over packing is a common problem which results in the bearing running hot. The steel backing plate of the seal is completely covered in

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COVER STORY

rubber to improve corrosion resistance.

Sealing

Triple lip viton rubber units have the same design as the standard rubber seal, but the viton material improves chemical and temperature resistance. The teflon seal consists of a teflon ring that floats between two steel plates and ensures highly efficient sealing. The material is impervious to most chemicals and because of its low coefficient of friction, these units have a high speed capability. External urethane seal covers, with triple lip nitrile or viton contact seals, can be snapped onto locating holes on the face of the housings for extra protection. The cavity between the cover and the housing can be filled with grease to act as a further seal if necessary.

Vibration

The standard locking method for these units is the eccentric collar. Unlike eccentric collars on ball bear-

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THE SOUTH AFRICAN MECHANICAL ENGINEER

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ing housed units, this QMSN collar has a shallow ramp when the collar is rotated to the inner ring. This ensures adequate grip even in applications where there is vibration. In addition, the angle of the axial contact area between the collar and inner ring is larger than normal. These two features prevent the locking mechanism from loosening. Alternative locking methods include a grub screw lock, a tapered sleeve lock using a standard adaptor sleeve arrangement and the new V lock method which encompasses a double taper locking method. Spare components for this series include bearings, seals and clamping nuts.

Interchangeable

QMSN Blue Brute spherical roller housed units are dimensionally interchangeable with other leading brands and standard split housings of the SN range. The Timken and QM range of imperial dimensioned housed units are interchangeable with other American produced units. This range is available nationally from BMG’s branch network of over 100 outlets. A technical advisory and 24 hour support service is offered. Rouff Essop, Divisional Manager, Bearings Division, BMG – Bearing Man Group, Telephone: (031) 576 6288, Fax (031) 576 6581, Email : rouffe@bmgworld.net, Website : www.bmgworld.net

June 2011


PIPES, PUMPS AND VALVES

Inside the Dome Valve A ball valve consists of a ball with an opening. As the ball turns in a tight fitting enclosure it aligns the opening with an inlet on one side and an outlet on the other, controlling the flow of material through the valve.

Jeremy Kirsch, director of Clyde Bergemann Africa

developing this product as the original developers, Macawber Engineering, was the original company which transformed into part of the Bergemann group of companies worldwide. They had a presence in South Africa at the time. “SA Mechanical Engineer” speaks to Jeremy Kirsch, director of Clyde Bergemann Africa, about this remarkable valve. It is no surprise that it has now firmly found its place in pneumatic conveying applications across the globe. “Originally patented in the late ‘70s, the Dome Valve is unique in its ability to open and close with a tight pressure seal in an environment where abrasive materials are used,” he explains. “No other valve can achieve a life as long as this in harsh materials handling environments. The unique closing and sealing action of the inflatable seal enables continuous reliable operation where conventional valves have always failed to perform.”

The search

The Dome Valve fitted onto a vessel

T

his, in principle, is how a dome valve works. The dome, however, is a partial section of a ball and when it turns the inlet opens and the substance flows through to the outlet. In the closed position, the dome valve turns against the flow of material forming an airtight seal. Although the procedure seems rather simple, developing the valve incorporated years of research and progressive development as a solution to find a suitable valve able to withstand the abrasiveness of materials conveyed in dense phase pneumatic conveying systems was explored.

No other valve can achieve a life as long as this Development

Clyde Bergemann has been intimately involved in

Dense phase pneumatic conveying, technology has always had a large footprint in South Africa and rapidly gained popularity. However, at the time dome valve technology was introduced, the majority of systems in use were utilising ordinary, commercially-available valves which seemed to hamper technology growth. “Macawber, using empirical research, persevered,” says Jeremy, “and set up test facilities, got various types of materials from clients and discovered what needed to be done in order to move the increasing quantity of materials through a dense phase pneumatic conveying system. “With dense phase pneumatic conveying a pressure vessel is literally filled with a specific material and pressurised using compressed air varying between 2 to 4 bars,” explains Jeremy. “The valve function, therefore, is not only to either allow or discontinue the flow of material from the vessel, but also to seal the vessel so that there is no compressed air leakage. Standard valves allowed this to a certain degree, but only with easily conveyable materials. Unfortunately, as more abrasive materials were experimented with, the system began losing its industrial integrity as the valves were unable to withstand the duty and deteriorated prematurely. The patented Dome Valve solved this problem and pneumatic conveying regained its earlier popularity.

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PIPES, PUMPS AND VALVES

between the seat and the closing member - the dome. Material is allowed to pass through or enter the controlled gap if, due to its characteristics, it is pulled in as the dome component closes position. In the closed position, high pressure air or other gas enters the space between the back of the seal face and the insert ring causing the seal face to expand both onto and around the periphery of the dome component. The seal then traps material particles against the dome surface, irrespective of particle size or shape. Before opening the valve, the seat is relaxed and the controlled gap re-established before the dome component moves to its open position. The seal itself is a loose component clamped into place by a spigot piece and external fasteners which hold the top plate assembly to the body. This allows for easy removal and inspection.

Inflatable seats

The valve that changed dense phase conveying for the better

It has now grown to maturity and is associated with this form of conveying.”

How it works

The dome component closes beneath the seat when the seal is relaxed, allowing a controlled gap

Inflatable flexible seats entrap particles that normally cause seat erosion by inducing them to move across valve seats under the influence of pressure differentials on either side of the closing member. Entrapping particles within a flexible face during valve closure prevents particle movement and considerably reduces valve seat wear. Inflatable seats allow automatic wear compensation.

Flexible seats entrap particles that normally cause seat erosion Today dome valves come in a wide range of standard sizes but uncommon sizes of up to 800mm in diameter have been made for special applications.

Special valves

Other unique features include high temperature valves with a number of different standard cooling methods enabling the valve to handle temperatures between 200ºC and 450ºC. Special valves have been designed to operate at temperatures up to 800 ºC in the direct reduced iron making environment in Korea improving the operation between reducing and oxidizing stages of the process. “More than 100 000 Dome Valves are in operation in almost every country, providing long life and operating reliability where conventional valves have failed,” Jeremy says in conclusion. “Having been involved with dome valve technology since its inception, it is in our culture. We have vast experience in this area and see it as a product line that plays a vital aspect in materials handling, be it in our pneumatic conveying systems or any other application. It is important for end-users to note that it is an excellent product when applied correctly and, most importantly, when it’s supported correctly.” Jeremy Kirsch, Clyde Bergemann Africa, Tel: (011) 704-0580; E-mail: jeremyk@cbz.co.za

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PIPES, PUMPS AND VALVES

The Thick Stuff We all know how tough denim is. Now imagine a pair of jeans getting into a pump. The likelihood of the pump seizing up and the jeans causing an impassable blockage is just about guaranteed, never mind the damage caused to the pump.

T

hen along comes the Vaughan chopper pump. “SA Mechanical Engineer” watches a video which shows a pair of jeans being fed into a pump. Split seconds later it comes out the other end through a transparent plastic outlet pipe, shredded to bits to the point that it appears to be clear water!

Grant Orsmond

,d ire

cto

r

This pump has an integral cutter blade on the impeller that cuts all solids, especially stringy materials This chopper pump is a unique pump design from Vaughan in Seattle, USA, distributed in South Africa by Monitor Engineering. To learn more, “SA Mechanical Engineer” speaks to Grant Orsngineering E mond, director of Monitor Engineering r o nit o based in Benrose, Johannesburg. M of “There are possibly only one or two other companies in the world that make a similar pump,” he says. “Ours is not a traditional cutter pump. This pump has an integral cutter blade on the impeller that cuts all solids, especially stringy materials as it enters into the impeller cavity.An external cutter breaks up any large solids before entering the volute.

containing bones and it’s also used extensively to pump and chop fruit while steel mills, petrochemical plants and paper mills use them too. The pumps are also used extensively in the wastewater industry.”

Mixing system

Vaughan also makes a Rotomix process mixing system used on digesters. Here, the chopper pump plays a key role in ensuring the nozzles aren’t blocked, says Grant, “Of the 600 of these systems installed the world, 12 are in South Africa and we’ve not had a single nozzle blockage in any of them. Using CFD software, we design a complete mixing system for each individual application in terms of placing the nozzles strategically in the tank for optimum efficiency.” Another offering from Monitor is a heavy duty industrial pump with unique interchangeability features that makes it one of the most versatile pump systems available on the market. “The Hydra-Cell pump range has just been extended to include pumps that can do up to 350 bar,” Grant says. “They are very specialised and can pump anything from water, to highly aggressive chemicals or oils as hot as 120ºC, and slurries or wastewater containing particles of up to 1mm in size.

Shears all solids

“The blade literally shears all solid materials against a cutting edge on the body of the inlet of the pump,” elaborates Grant. “This allows us to offer a non-clog guarantee on this pump, especially if we select it for a specific duty. The installed base in South Africa includes applications such as airports where they pump all the rubbish that comes off aircraft. Many abattoirs use it to pump offal An installation in a gas plant THE SOUTH AFRICAN MECHANICAL ENGINEER

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PIPES, PUMPS AND VALVES

Inside the pump

“The beauty is that all these fluids are pumped with the same basic pump, you simply change the wet-end components over for specific applications,” clarifies Grant. “For example, for one application you’d have a front end made of Buna diaphragms, brass head and stainless valves and seats, but for another application which may chemically be more aggressive, you simply change these components over to Teflon,and Hastelloy. We offer a whole range of mix and match front end components made of different materials in order to suit all the different fluids that need to be pumped.

Using CFD software, we design a complete mixing system for each individual application “The design of the pump is unique in that it does not have any mechanical seals,cups or packings,” explains Grant. “It has a back end which is filled with oil and which is separated from the wet end which contains a set of diaphragms that acts as a barrier. There is no stress across the diaphragm because it is hydraulically balanced, meaning the pump can run dry and rotate in any direction. This makes it possible to pump difficult materials like hot oils, chemicals and abrasive slurries at pressures of up to 350 bar,at flows up to 130l/min”

The Hydracell pump

Different duties

Originally this pump was designed for reverse osmosis applications and it is still widely used today in navy ships around the world. “Locally the petrochemical industry is increasingly using this pump, not only because of its versatility in terms of having one basic base pump for a wide range of applications, but also because of its energy efficiency,” Grant elaborates. “Until now, energy efficiency has not really been a factor, but energy-conscious engineers have started to notice this pump’s performance which, depending on the duty, is on average 20 to 30% lower than normal multistage centrifugal pumps.” The Hydra-Cell is a positive displacement pump with a front end that is changeable within a couple of minutes to suit a specific duty. “The same pump can be used for five different duties, you simply have to keep spares for the specific wet end kit for the different applications,” Grant says in conclusion. “Both these pumps are highly specialised and therefore relatively expensive, but in the long run it’s the only answer when coping with challenging materials that call for high maintenance costs on ordinary pumps. We don’t do a lot of business in spares because these pumps last a lifetime. Users who have converted to our product never go back to conventional pumps.” Grant Orsmond, Monitor Engineering, Tel: (011) 618-3860, Email: grant@monitorpumps.co.za

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The inside of the Hydracell

A Vaughan chopper pump installation

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Wheel Force Transducer Any analysis, modelling or simulation of off-road vehicle dynamics must include a thorough understanding of the forces developed between the terrain and the tyres. From a vehicle dynamics point of view, these forces are important for ride comfort, handling as well as acceleration and braking. They are also extremely important for proper design of suspension and chassis components for strength, stiffness and fatigue life.

I

n order to measure these forces, a concept wheel force transducer has been developed that can measure the forces and moments between a tyre and a road under off-road conditions. This transducer could ensure better testing of off-road vehicles. This work was done by P.S. Els of the University of Pretoria, South Africa for the US Army International Technology Center-Atlantic. The proposed wheel force transducer is an important step in correcting the gap in current tyre testing and modelling knowledge to ensure that future off-road vehicle models and simulation efforts are conducted with confidence. In order to obtain tyre characteristics over off-road terrain, cost-effective field test equipment was required.

ences in mass, but the current wheel load cell was designed for a gross vehicle weight of 5.5 tons. The first important step in the concept design was to determine the space envelope, and therefore basic dimensions available to fit the transducer. Due to the suspension components on the inside

To obtain tyre characteristics over off-road terrain, costeffective field test equipment was required The initial design of the wheel force transducer was done for typical sports utility vehicles where the static wheel load is around 500 kg. The transducer can however be used on larger vehicles such as the High Mobility Multipurpose Wheeled Vehicle (HMMWV or Humvee) of the US Army. There are many derivatives of the HMMWV, with large differ-

Standard HMMWV rim dimensions

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COMPUTERS IN ENGINEERING

Force transducer mounted to modified rim

Standard and modified rim

Six load cells

Some of these projects involve autonomous vehicles, controllable suspensions and the development of offroad tyre models of the wheel, the transducer had to be mounted to the outside of the standard rim. The wheel force transducer had to replace part of the rim so that the rim was connected to the hub via the force transducer.

The load cell outer ring was mounted to the hub using the hub mounting adapter, which connected the load cell outer ring to the vehicle’s hub with the existing hub bolts and nuts. The hub mounting adapter was also bolted to the load cell outer ring. The load cell inner ring and outer ring were connected to each other via six individual tension-compression load cells. The load cells were mounted such that the three tyre forces and three tyre moments could

Individual tension-compression load cells

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COMPUTERS IN ENGINEERING

field testing as well as component durability testing that will be performed in the University of Pretoria’s Sasol Laboratory for Structural Dynamics.

Local training

MSC.Adams, MSC.Nastran, MicroStrain and KMT are supplied and supported locally by Esteq Engineering. Esteq provides training courses to university students on campus in using these various technologies to prepare them for industry where these tools are indispensible. Esteq Engineering focuses on supplying technology solutions to local and global manufacturers, technology companies, research institutions and universities.

Future designs will transmit data wirelessly via a KMT telemetry system to a receiver on-board the test vehicle

be calculated form the six tension-compression forces measure with the individual load cells and the geometry. The possibility exists to mount the wheel force transducer to different rim sizes and designs. The exact possibilities depend on the geometry of the different rims, but basically entail designing and manufacturing adapters to connect the load cell inner ring to the rim, and the load cell outer ring to the hub. This can also be turned around so that the load cell inner ring is mounted to the hub, and the load cell outer ring is mounted to the rim. The smallest rim size that can be accommodated with the current design is 14 inches. Plans are also in process to develop a load cell for much larger rims.

The company has been actively promoting technology solutions in the simulation and testing industries for more than 15 years. Simulation is the use of virtual computer models, to understand and predict the performance of a system without physically building and testing the design. This facilitates much deeper insight into the system, which in turn enables the engineer to understand and optimise the design, prior to manufacture. Testing involves the measurement of the physical performance and behaviour of a system. These tools in turn empower the product designer to make educated engineering decisions. LislĂŠ Hansen, Esteq Engineering, Tel: +27 (0)12 809 9500, Fax: +27 (0)86 645 3686 | Cell:+27 (0)83 554 3441, Email: lisleh@esteq.com, Website: www.esteq.com

Software

MSC.Adams software was used to verify the relationships between the various force transducers’ force components to ensure the correct results representing the actual input forces were obtained during post processing. MSC.Adams is also used in various other projects of the University of Pretoria involving vehicle dynamic simulations. Some of these projects involve autonomous vehicles, controllable suspensions and the development of off-road tyre models. The strength of the transducer was evaluated by performing a Finite Element Analysis (FEM) using MSC.Nastran on multiple load cases that are considered to be important. One of these considered a case where the vehicle could land with the full vehicle weight on one wheel with only one of the six load cells in the wheel force transducer carrying the entire load. This was calibrated and validated against other force measurements under laboratory test conditions and excellent results were achieved. The first prototypes used MicroStrain V-links to record and transmit data. Future designs will transmit data wirelessly via a KMT telemetry system to a receiver on-board the test vehicle. The next step is THE SOUTH AFRICAN MECHANICAL ENGINEER

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SA INSTITUTE FOR NON-DESTRUCTIVE TESTING

Role of NDT in Petro-Chemical Although NDT has a wide ranging role petrochemical industry, this editorial will concentrate on the lifecycle of petrochemical pressure equipment.

T

he first phase is the fabrication of the pressure equipment. This is typically the rolling, forming and welding of various components and configurations to produce the final product. During every step of the process, NDT is used in different methods either as a quality control (QC) tool or a quality assurance (QA) tool. Typical forms of NDT performed in this phase include visual testing, (VT), magnetic particle (MT) testing, penetrant testing (PT), ultrasonic testing (UT), radiographic testing (RT) and pressure/leak testing. In the fabrication of pressure equipment there is an old adage that rings true: “You don’t get what you expect; you get what you inspect”.

Once the fabrication of the pressure equipment is completed and delivered to the owner, it is installed and ready to be commissioned. Part of the commission phase is a pre-commission inspection that relies on a variety of NDT methods to certify the pressure equipment as safe to put into operation. The third phase is the in-service operation of

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pressure equipment. During this phase, pressure equipment is put into operation by the owner to perform what it has been designed to do. The owner is required to establish a frequency at which inservice inspections will be conducted. The purpose of these inspections is to determine the integrity of the equipment. In this case, the integrity being referred to is its fitness for continued safe operation in its process environment. The NDT methods used in this phase are therefore selected to detect defects that may be caused by the operating parameters and/or process environment.

Not be underestimated

Here, a wide variety of specialised techniques are available that have been designed and developed to detect specific defects or to focus on certain areas where certain defects can be expected. This cycle of operation - in service inspection-operation will continue until the integrity is deemed to be unfit for operation or the owner has made a business decision to remove the equipment from service. At this stage the equipment may be scrapped and the material recycled. So, to return to the role of NDT in the petro-chemical industry, this can be summarised as it being a tool to determine the integrity of pressure equipment. Most important is that the integrity can be seen to be the safe construction and operation of equipment – safe to man, the environment and the owner’s investment. Therefore, the value of NDT should not be underestimated.

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COMPUTERS IN ENGINEERING

Let FEA Work for You Storage tanks, pressure vessels and heat exchangers, in their multitude of shapes and sizes, are used for storing and treating liquids and gases. In order to control substance flow, each is an integrated system comprising nozzles and valves connected to pipe networks.

FE/Pipe is a template-driven Finite Element software package

T

o design and test all elements of such an integrated system, there are several internationally accepted standards. These include the WRC 107 and WRC 297 guidelines, and a method developed by LP Zick, to analyse the design. However, the standard methods used to analyse pressure vessel and piping systems were developed nearly 50 years ago using limited test data. Design methods presented in WRC 107, WRC 297 and by Zick have served the industry well, but have severe limitations.

Graphical and tabular results that clearly describe the situation at hand Engineers often apply these methods far beyond the intended boundaries and it becomes akin to putting square pegs in round holes. For instance, Zick’s method never addressed axial loads on saddles, a considerable concern for seismic or offshore applications. And neither WRC’s 107 nor 297 provide analyses for the most common element-reinforcing pads.

Software does the job

Durban-based company, Chempute Software, offers a wide range of software solutions for mechanical engineers to cover the design and analysis of tanks, pipes and nozzles. “SA Mechanical Engineer” speaks to Andrew Taylor, sales director at Chempute, to learn more. “Finite element technology moves beyond the limitations of standard methods allowing engineers to design safer equipment more efficiently and cost-effectively,” he says. “NozzlePro, for example, allows you to build WRC and Zick geometries with just a few clicks on the keypad. Considering that

the program provides finite element results from the exact same amount of information needed to run a WRC or Zick analysis, the advantage is clear. “NozzlepPro is straight forward and easy to use,” Andrew says. “Interactive window displays provide graphical input instructions, taking the guesswork out of geometry design and allowing the user to quickly plot a model for visual verification. It generates graphical and tabular results that clearly describe the situation at hand. The graphics can be viewed with DirectX and vividly display the results of pressure moments, temperature and loads while the interactive toolbox allows users to dissect and manipulate models.

Info exchange

The tabular results give flexibilities and stress intensity factors (SIFs) that can be put back into a piping or pressure vessel design package, adding greater accuracy and better results. “NozzlePro is designed to quickly and easily evaluate nozzles, saddles, pipe shoes and clips,” Andrew explains. “A variety of head types, including spherical, elliptical, ASME dished, cylindrical and conical, are allowed. Engineers are able to include thermal, weight, operating, occasional, pressure, wind and earthquake loads.”

Other packages

There are some 25 different software packages available from Chempute to cover specific mechanical engineering aspects. These include, among others: Finite Element Analysis of Flanges, Steady State and Transient Fluid Simulator, Pipe Stress Analysis, Non-Pressurised Tank and Mixer Design Vessel,

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FE/Pipe includes several stand-alone modules

material databases, corroded nozzles, corroded hydro test, corroded wind girder calculations, and wind pressures. A material database editor is provided so the software can address additional materials not included in the code.

Screen shot of DirectX 3-D Viewer

Heat Exchanger & Piping Component Analysis and API 650/653 Oil Storage Tank Design and Analysis. “Tank, for example, is a comprehensive engineering software programme that designs and analyses oil storage tanks according to the latest API-650 and API-653 codes,” says Andrew. “For much less than it would cost to build an in-house spreadsheet application, this programme delivers the features and stability typical of an Intergraph software product, including immediate technical support.

More than the computerisation of a time-consuming engineering task

“It is much more than the computerisation of a time consuming engineering task,” he adds. “Its development was shaped by the input of many ‘API650/653 expert’ engineers whose influence ensured that Tank performs the required tasks effectively and efficiently. A menu-driven scroll-and-select interface provides logical options when and where expected. Context sensitive help provides instant technical assistance for each data field, with code references as often as possible.” Tank also provides control options for everything from calculations to screen colours, allowing the work environment customisation on a directory basis. Options affecting computations include THE SOUTH AFRICAN MECHANICAL ENGINEER

“Program revisions incorporate additional capabilities addressing both technical and operational items,” explains Andrew. “Users are encouraged to suggest improvements that would help their dayto-day usage of the software. The latest version of Tank includes the most recent addendum to the 9th edition of API-650 as well as the up-to-date addendum to the 2nd edition of API-653.”

Services

Saving time

22

“The programme also provides several standard units files which, if insufficient, can be used to generate other, custom unit files,” says Andrew. “Completed jobs can be converted to other unit systems as client requirements dictate, without rerunning the analysis. The program is continuously maintained by Intergraph engineering staff, the original programme developers, and now an Intergraph company.

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“Software products available cover all aspects of engineering design in chemical and gas processing, power generation, and oil refining industries,” Andrew says in conclusion. We provide a full service to industry, giving advice on suitable hardware configurations, installing the software where requested, providing training in software use, and extending full technical backup on all programs. We also offer training courses for several of our software programmes – FEPipe, NozzlePro, ChemCAD, Caesar, Tank, PVElite/Codecalc, AFT Fathom/Arrow and CADWorx. These can be arranged at the client’s site if required.” Andrew Taylor, Chempute Software, Tel: (031) 764-6840, E-mail: ataylor@chempute.com Website: www.chempute.co.za

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POWER GENERATION

Produced by: PROMECH PUBLISHING, P O Box 373, Pinegowrie, 2123 Republic of South Africa Tel: (011) 781-1401 Fax: (011) 781-1403 Email: editorial@promech.co.za Website: www.promech.co.za Managing Editor Susan Custers Editor Kowie Hamman Advertising Louise Taylor Circulation Catherine Macdiva DTP Zinobia Docrat/ Yolanda Flowerday Disclaimer PROMECH Publishing does not take responsibility for the opinions expressed by individuals. Printed by: Typo Colour Printing Tel: (011) 402-3468/9

PVB Film: The Alternatives to Ethylene-Vinyl Acetate (EVA) PVB is increasingly assuming the leading role among alternative encapsulation materials for solar cells.

R Copyright All rights reserved. No editorial matter published in “Power Generation Today” may be reproduced in any form or language without written permission of the publishers. While every effort is made to ensure accurate reproduction, the editor, authors, publishers and their employees or agents shall not be responsible or in any way liable for any errors, omissions or inaccuracies in the publication, whether arising from negligence or otherwise or for any consequences arising therefrom. The inclusion or exclusion of any product does not mean that the publisher or editorial board advocates or rejects its use either generally or in any particular field or fields.

eliable and long-term protection of solar cells from external influences is a must for solar modules. This is where transparent plastic encapsulation materials make a crucial contribution to the durability of photovoltaic modules and to the long-term generation of electricity from sunlight. This article explains in broad terms which plastics are suitable and why. Special attention is focused on polyvinyl butyral (PVB), a plastic best-known so far for its use as the interlayer in laminated safety glass.

tovoltaic Institute and the Fraunhofer ISE Institute in Freiburg since the beginning of the 80’s. Kuraray is currently working on the market launch of a second generation of films which is designed for all conventional photovoltaic module production processes and will extend the uses of the current range of films to include special applications.

EVA as a cell encapsulation material

Ethylene-vinyl acetate (EVA) is still the market leader and standard encapsulation material for solar cells. EVA’s widespread use

The first manufacturer worldwide to develop a special PVB film for use in solar modules the Trosifol brand - was Kuraray Europe GmbH. Solar modules using Trosifol PVB films have been successfully undergoing outdoor weathering tests on the module test rigs of the Berlin Pho- Principle of a crystalline module assembly THE SOUTH AFRICAN MECHANICAL ENGINEER

Front glass

Eg. TROSIFOL SOLAR (PVB) Arrangement of crystalline cells Eg. TROSIFOL SOLAR (PVB) Backing glass

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• Barrier to oxygen and water vapour • Prevention of cell corrosion • Adapted adhesion to other module components (glass, cell, backing film, contacts etc.) Glass ply

• High transparency and high UV protection (to prevent degradation of the plastic) There are few plastics that display all of these properties reliably in practice. Classical solar modules using crystalline Si wafers were joined almost a decade ago by thin-film PV modules on which the semiconductor is applied directly to (rigid) substrates - preferably glass in this case - and then mostly sealed at the rear with another ply of glass or alternatively with a multiple-ply barrier plastic.

Eg. TROSIFOL SOLAR (PVB) Glass ply with photoactive layer

Because of the way the cell is applied to the glass (high-vacuum deposition at temperatures up to 630°C), few materials are suitable as substrates for thin-film modules, although flexible substrates made of copper or stainless steel are possible as well as glass.

Principle of a thin-film module assembly

is explained by its favourable processing properties as a cross-linking rubber-elastic material in vacuum laminators, its adapted technical product features and, by no means least, its low price.

Overview of possible cell encapsulation materials

For a long time there have been no alternatives on the horizon, as finished modules produced since the 90’s have a service life of at least 20 years and all series products have to be certified. It is therefore difficult for other plastics to gain a foothold on the market as the points in their favour are rarely measurable.

Table 1 gives an overview of the encapsulation products industrially used today. A distinction is made between elastomer cross-linking and thermoplastic materials. The elastomer cross-linking products include the most frequently used EVA, TPU and acrylate encapsulation resins, and two-component silicones that cross-link on exposure to heat and/or UV light to form a rubber-elastic material and thus firmly embed the solar cell.

Requirement profile for encapsulation materials

To ensure module durability and long-term power generation, cell encapsulation materials have to display certain important features:

These contrast with thermoplastic products that melt without cross-linking on exposure to heat, thus retaining their original chemical composition. These include above all polyvinyl butyral, the most frequently used material after EVA, particularly for thin-film solar modules.

• Mechanical protection of the cell • Protection from weathering • Electrical insulation • External impact resistance

All the other products such as thermoplastic polyurethane (TPU), ionoplastics, modified polyolefins and the abovementioned elastomers are currently of only secondary importance.

Encapsulation materials

Polyvinyl butyral (PVB) Elastomers (cross-linking)

Thermoplastics (non cross-linking)

Ethylene-vinyl acetate (EVA)

Polyvinyl butyral (PVB)

Polyurethane encapsulation resins (TPU)

Thermoplastic polyurethane (TPU)

Polyacrylate encapsulation resins

Ionoplastics

Silicones (2K)

Modified polyolefines (EPDM, DMP ...)

Overview of conventional encapsulation materials

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The plastic polyvinyl butyral (PVB) has been in use as the interlayer for laminated safety glass since the 1940’s. Its main applications are in windscreens in vehicles and safety glazing in architectural applications, eg, modern glass façades. Since 2005, efforts have been afoot in the PV module industry and the glass industry to replace EVA with PVB film in double-glazing elements with integrated solar cells in order to significantly enhance the standard of


POWER GENERATION

safety of laminated module glass in Building-Integrated Photovoltaics (BIPV).

Today’s cell and module technologies and associated encapsulation methods

Furthermore, thin-film solar modules consisting of two plies of glass sandwiching a PVB interlayer can be inexpensively manufactured with the lamination process successfully used for the production of laminated safety glass. In view of the already evident and fast-growing demand for thin-film solar modules - forecasts anticipate 40 percent of total module output by 2020 - the use of PVB film will continue to grow accordingly with a considerable expansion of its market share.

Module technology

Crystalline technology 88%

Glass/ backing film 90%

Vacuum laminator

Vacuum laminator

TPU, silicones and other encapsulation materials

The reason for the low market share of other plastics is mainly due to their lack of experience with the products of the solar industry, their inadequate technical properties and their excessively high cost. It is also essential that such products perform impeccably in the solar module for 20-25 years, which is only possible if they comply with the relevant electrical standards (electrical function tests conforming to IEC).

Glass/ backing film 20%

Glass/glass 10%

Thin-film technology 12%

Glass/glass 80%

Vacuum bag/ autoklave

Vacuum laminator

Vacuum laminator

 Roller laminator/ autoklave

automated module production plants possible, thus reducing production costs significantly. This process technology is also of benefit to thermoplastic encapsulation materials such as PVB film, TPU and others, as the much accelerated throughput lowers costs substantially. At the same time, thin-film solar modules can also be produced in a single cycle in a roll laminator with subsequent autoclaving. This method has been

As a result of pressure from manufacturers on the system costs of modules, more expensive products such as TPU and ionoplastics usually drop out of the running. New plastics have to overcome high technical and commercial barriers if they are to gain recognition and pull through as encapsulation materials for solar cells.

Processes for the encapsulation of solar cells

The single-opening vacuum laminator has been the preferred production method for the encapsulation of solar cells for several decades now. For crosslinking plastics, it permits rapid throughput and high production efficiency. For other products, such as thermoplastics, the process has to be adapted, as the higher melting temperatures of thermoplastics make the lamination process more energy- and time-consuming, and the cycle times are slightly longer.

Cut the costs

The development and availability of so called multiopening or stack laminators have accelerated module throughput at the encapsulation stage and cut the cost of module production considerably. These laminators have made significantly larger and fully

BPIV in China

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successfully employed for decades for the production of laminated safety glass with PVB films and is at least as efficient as the vacuum laminator (Table 2).

Module applications and their effect on materials

Solar modules are usually preferably installed either on roofs or on open ground as photovoltaic power plants. These two forms of installation account for the lion’s share of commercially-installed solar modules. In addition, there is also the possibility of integrating solar cells in buildings (BIPV) – for instance, on facades or in solar glass roof elements. Even if the market for this is still small today, a big future has been forecast for BIPV. The current market share is less than 1 percent of installed modules because the systems are still very cost-intensive and building wiring systems are still underdeveloped and lack standardisation.

A fine example

A fine example of BIPV is New York’s Stillwell Avenue subway station, the world’s biggest rapid transit terminal with the world’s biggest buildingintegrated photovoltaic system - using thin-film solar modules containing Trosifol PVB films. In Europe in particular, building integrated photovoltaic installations are subject to the same high safety standards as all other glazing on façades or in overhead applications.

BPIV in the Netherlands (photo courtesy Scheuten Solar Glass)

In Germany, in the official technical specifications for building materials, laminated safety glass with an interlayer of PVB film is stipulated for overhead glazing. If these elements are replaced with solar modules, the same standards apply. This means that EVA and other plastics in PV modules in such applications can only be used after an elaborate process to obtain permission. For Building-Integrated Photovoltaics, experts are forecasting a sharp rise in commercial applications in the next ten years.

Conclusion

Until just a few years ago, photovoltaics was confined to classical applications such as systems installed on roofs and power plant configurations, and preference was given to modules containing crystalline cells. EVA was the top choice as the encapsulation material. Recent years have seen the extension of the range of cells and modules to include thin-film alternatives, new and improved processes for the production of modules, and new applications such as BuildingIntegrated Photovoltaics. Encapsulation materials for solar cells will adapt to these new conditions. A very important alternative is Trosifol PVB film, which is by far the most widely used film in laminated safety glass. By Dr. Bernhard Koll Hennie du Preez, Leobeck Sales International, Representative for Trosifol PVB Films, Tel: (011) 234-5175, Email: hennie@leobeck.co.za, www.trosifol.com

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POWER GENERATION NEWS

Two strong partners

With Guodian and LEC, Voith Turbo has managed to find two strong partners in China for its drive concept WinDrive: China Guodian Corporation is China's largest energy producer, and Lanzhou Electric Corporation (LEC) is one of the leading manufacturers of electric drives and generators. Both have decided to use the Voith WinDrive for 2 and 3-MW wind turbines. LEC, which is based in Lanzhou, holds a stake in the 10GW wind park in Jiuquan (Province Gansu), the first of six planned wind parks in the northwest of the country. The region is not only home to China's largest wind power plant, but also the world's biggest onshore wind park. By 2015, 10 GW of electricity will be generated here. This is sufficient to cover the power requirements of approximately 6 million households. LEC has opted for the WinDrive as sole drive solution.

For this purpose, Voith has co-developed a new 2-MW turbine, and a series contract has already been signed and sealed. The series envisages over 100 WinDrives per year. Alongside LEC, the Chinese energy producer Guodian, too, has decided in favour of the Voith solution. The company plans to use the WinDrive in the driveline of wind turbines for on and offshore wind parks. For these wind parks, Guodian United Power Technology - a subsidiary company established especially for the renewable energy segment - is developing a new 3-MW turbine. Series production of the high-performance wind turbine with Voith drive technology begins in 2012; initial production plans aim at 100 units per year. Voith Turbo, Roy Webster, Tel: 011 418 4036 (direct)/ 011 418 4000, Fax: 011 418 4080, Email: roy.webster@voith.com, Website: www.voith.com / www.rsa.voithturbo.com

Bunded fuel tanks

These robust fuel tanks, which have robot welded seams for enhanced strength and extended service life, are available in six different models with a fuel capacity up to 3 000 litres. To alleviate storage space problems, these tanks can be stored two high when full and three high when empty.

“Because dangerous pollution is caused by the leakage of damaging fuels and phosphates, current legislation in South Africa makes it illegal to store or transport fuels without an inner bunded tank,” says Arnold Retief, a director of Ai-Tec. “Ai-Tec AutoTank bunded fuel tanks have been designed, tested and manufactured to comply with Pollution Protection Guidelines.”

AutoTank fuel tanks are fabricated from high grade mild steel. The inner tank contains the initial volume of fuel and in the unlikely event of a leak, the outer tank prevents fuel from escaping into the environment. The bunded tank has a capacity of 110% of volume. A steel inner tank is easily removable for maintenance and inspection.

Advanced Industrial Technology (Ai-Tec), manufactures a range of industrial bunded fuel tanks that meet stringent quality and environmental standards required for safe fuel storage and transportation.

Special fittings include AC and DC fuel transfer pumps, hand pumps with a 900 cm³ cycle, automatic nozzles and electronic meters for precise control and measurement. A range of cartridge, foot and line filters, with varying filter capacities and flow rates is also available. A full range of accessories is designed to enhance operation in different environments and applications, including diesel and petrol engines for fuel dispensing. These bunded tanks can be mounted on trailer units with options for safe and efficient site tow applications. Detachment takes less than five minutes if the tank is required for general use. This range of trailers is manufactured in heavy duty steel are hot dipped galvanised to prevent rust. Ai-Tec specialises in the design, manufacture, installation and maintenance of an extensive range of industrial and commercial equipment, which encompasses heat generation, waste management and energy production products. Ai-Tec also offers kitchen and laundry services to factories, the mines, hospitals and the commercial sector. Arnold Retief, Tel: 0861 248 320, Email: arnold@zsteam.co.za, Web: www.ai-tec.co.za

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NUCLEAR INSTITUTE (SA BRANCH)

Rutherford Revisited Perhaps we should begin with a nod towards the late great Ernest Rutherford or, to show proper respect, to Baron Rutherford of Nelson. May 2011 marked the centenary of his announcement of the discovery of the nucleus.

R

utherford did pretty well. He was born in 1871, fourth of twelve children of a New Zealand wheelwright cum farmer of Scottish descent. He died in 1937 after a distinguished academic career at Cambridge and elsewhere, a revered physicist and member of the House of Lords. In 1908 he won the Nobel Prize (for chemistry yet) and spent the £7000 on presents for his parents and numerous siblings and on a motor car for himself and his wife.

Baron Rutherford

Becquerel discovered radioactivity in 1896. The Curies isolated radium two years later and Rutherford identified alpha and beta particle radiation. He studied radioactivity in Canada and introduced the idea of half-life. He set Geiger and Marsden to bombard gold foil with a well defined beam of alphas and, noticing a slight degree of scattering around the edges of the transmitted beam, got them to set up the equipment to look for particles which actually bounced back by the foil. To his enormous surprise he found them and deduced the existence of a minute but massive positively-charged ‘nucleus’ surrounded by JJ Thompson’s recently discovered electrons.

More than any other country, Germany panicked after Chernobyl It had to be fission

He subsequently discovered protons by knocking them out of nitrogen nuclei with alpha particles and, to explain the relatively great mass of the nucleus, deduced that it must also contain neutral particles that he called ‘neutrons’. James Chadwick demonstrated their existence in 1932. Fermi and others began irradiating everything in sight with these new-fangled neutrons and in 1938 Germans Hahn and Strassman found traces of barium in irradiated uranium. All the other fission products must have been there also but barium was the one they identified. Incredibly, it had to be fission. With momentous timing in 1939 Joliot-Curie in France demonstrated that, as expected, fission was accompanied by ‘spare’ neutrons and that a chain reaction was indeed conceivable. Einstein had already pointed out that, given a chain reaction, massive energy could be released and was now

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persuaded to write his celebrated warning letter to President Roosevelt. So it all began. As a matter of interest, the Director of the Geological Survey wrote about radioactive minerals in South Africa in 1915 and one RA Cooper reported uraninite ore in gold mines in 1923. An urgent Manhattan Project literature search exposed all this in 1944 and pitch-forked South Africa into the nuclear business. Let’s hope we stay in it. As I write, the German Government has announced, again, that it will phase out nuclear power. More than any other country, Germany panicked after Chernobyl and, inter alia, shut down nuclear research activity and its two operating pebble bed reactors. The Green Party / Social Democrat ‘water-melon’ alliance later announced that all nukes would be shut down. They were to have on average nineteen years to operate. Angela Merkel’s alliance extended that fairly recently by an average of twelve years; the ‘windfall’ to the power companies was to be taxed to finance the introduction of renewables. Now, post-Fukushima, the Germans have decided once again to phase out nuclear this time by 2022. It will be interesting, in the light of the recent damning report by the John Muir Foundation on the dismal performance of UK wind energy, to see how they get on.

Wrong-headed reports

I’m convinced that thinking people will not endorse nuclear power, especially after Fukushima, while they believe that renewables can do the job. There must clearly be devious nuclear interests at work. We have, after all, the recent WWF report assuring us that the world can be 100% renewable for total energy by 2050. Greenpeace is admittedly more restrained and talks of just 94%. Wind-turbine suppliers like Suzlon of India, who presumably have no vested interests at all, tell us (Business Report 26 May) that we can feed 25% of renewable electricity into the grid ‘without any adaptations’. I remain despairingly critical of the public relations efforts, or lack thereof, of the nuclear industry. It astonishes me that we choose to ignore all such statements. It seems entirely obvious that we should analyse idealistic but wrong-headed reports and vigorously expose the flaws – like WWF’s basic assumption that world energy demand will be 15% less in 2050 than in 2005. I have to accept that so far our non-technical political leaders have been with us and I guess that attests to behind the scenes lobbying. But we may risk losing them if we do not respond to instructions like that recently from Minister Dipuo Peters to do better with the public. John Walmsley

June 2011


BEARINGS AND LUBRICATION

Special Lubricants Lubrication is key in controlling wear between moving parts, be it inside a bearing, on a shaft, interlocking gears or simply when two surfaces slide over each other. Just as there are many possible wear scenarios, so there are lubrication solutions. Therefore choosing the correct lubrication, appropriate to the material and the application, is an absolutely necessity. our bearings to fail prematurely. Kobus stresses, “Our range of special lubricants considers external influences such humidity, dirt, dust, temperature, speed, load and particularly the regulations concerning cleanliness and hygiene as required in the food and packaging industry.”

Bearings

Kobus gives us an example with mechanical seals which are also made by Depac and one of Pactor’s main lines of business. “To ensure the long life of the bearing inside the mechanical seal, we use a special grease made by DuPont,” he explains. “It’s a metal free lubricant that can withstand high temperatures and doesn’t break down in composition when exposed to aggressive chemicals.” A lubricant rapidly gaining ground in South Africa is an inside-bearing lubricant. “This lubricant doesn’t look like a grease at first sight, but once you spray it into the bearing it thickens into a long-lasting

Kobus Swanepoel, director of Pactor

A

whole range of specialised lubricants for a wide range of application comes from Depac based in Liechtenstein, Europe. Represented in South Africa by sole distributor, Pactor in Pretoria, “SA Mechanical Engineer” speaks to director, Kobus Swanepoel.

Choose right

“Whether it is oil or grease, mineral based or synthetic oil, the correct choice of lubricant will provide the user with a considerably longer service life and will lower production and operating costs by preventing unexpected downtime and an interruption of production,” he says. “Depac offer a large number of highly specialised lubricants for a wide range of applications including industrial, sewage treatment, food processing and chemical processing plants.”

The mechanical seal unit fitted on a pump refurbishment

The wrong selection and application of lubricants causes 64 % of all bearings to fail prematurely A study by a leading bearing manufacturer on bearing lubrications shows that the wrong selection and application of lubricants causes 64 % of all

The anti-seize Kobus uses on bearings, bolts and gasketsinall the work they do

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BEARINGS AND LUBRICATION

The components that make up a mechanical seal

grease,” explains Kobus. “This is a lubricant specially developed for the lubrication of the insidebearings of chains. It is mineral oil based with penetrating and load bearing

The bearing inside a mechanical seal is fitted with a special lubricant

characteristics. As the result of special additives, a long lasting, pressure resistant lubricating film is formed within tight tolerances. The service life of chains is measurably increased while the energy consumption and noise levels are noticeably reduced.”

Only anti-seize product on the market that is nuclear approved ISO approved

A product widely used in South Africa in power stations, the mines and general engineering workshops is an anti-seize product from Depac. “This product eases the mechanical assembly of bolts, screws, flanges, gaskets, bushings, studs and bearings,” explains Kobus. “Apart from allowing for more accurate torque it makes for easy disassembly by preventing rust and corrosion and seizure up to 1400° C. This permits the reuse of threads and parts by preventing breakage when bolts are loosened. “It is the only anti-seize product on the market that is nuclear approved and carries ISO 14001 environmental approval,” adds Kobus. “It can be applied on steel, stainless steel, aluminium, copper, brass, iron, titanium and many other metals. Stainless on stainless tends to fuse together after a time, but when we apply the 505 metal-free anti-seize I’ve never had a problem in loosening a stainless steel bolt or nut.” Kobus Swanepoel, Pactor, Tel: (012) 804-6979, Email: kobus@pactor.co.za

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BEARINGS AND LUBRICATION

Optimizing Bearing Performance

C

haracteristics such as stiffness or allowable deflection, lubrication requirements, static and dynamic misalignment, speed capability, load capability, and desired service life or durability all factor into choosing the best bearing for the application. In any given system, rolling element bearings inherently manage broad ranges of speed and many combinations of radial and axial loads. However, surrounding environmental conditions such as low and/or high temperature, dust and dirt,

It is important for engineers to understand why certain bearings are suitable for heavy load applications

To accomplish reliable equipment operation and associated bearing performance, it is essential to select the proper bearing for an application and its environment. The most challenging bearing applications, which are subject to heat generation, include power generation, wind turbines, gear drives, and rolling mills. These applications demand a bearing with engineered characteristics that can accommodate dynamic misalignment and slide-roll relationships, all while maintaining a lower operating temperature (see Fig. 1).

moisture, and unusual mounting conditions can adversely affect a bearing’s performance. Therefore, it is important to consider both the power transmission system mechanical and environmental factors that may significantly impact the bearing choice and its performance.

The first step

The first step in bearing selection is identifying the proper roller element type, whether it is a ball, needle, cylindrical, spherical, or tapered roller bearing. Each bearing type has advantages and disadvantages that are design-specific and will affect such things as the load and speed the bearing can tolerate in the application, as well as the predicted durability and service life. The size constraints of the bearing envelope or available space must then be addressed in the second step of the bearing selection process. This is done by considering the minimum shaft diameter, maximum housing bore, and available width in the bearing application. After the bearing envelope is defined, the selection options should be limited to bearings with bores, outer diameters, and widths that will fit in the bearing envelope.

Defined and satisfied

Fig 1: Bearing selection matrix often serves as a guide to bearing selection, but thorough and proper analysis can ensure proper bearing performance

There may be several bearings with different load-carrying capacities available that fit in the envelope. Once the suitable bearing choices are defined according to the parameters required for installation, the third step is to determine which of these bearings is best able to produce the desired predicted-service life in the application by performing a bearing-system-life analysis (see Figs. 2-3). The key contributors to high performance and bearing life in industrial applications include ability to carry combination radial and axial loads, high load capacity, speed, and

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BEARINGS AND LUBRICATION

Fig 2 and 3: Bearing manufacturers can complete a bearing-system-life analysis through application modeling and performance prediction

misalignment capability; SRBs (spherical roller bearings) are specifically engineered to handle such conditions.

- sole supplier of

A gear application

Gear applications often place great demands on a bearing system. However, spherical roller bearings are best suited to applications that carry significant

197693

Finally, the bearing selection is completed once the bearing design options are defined and satisfied. Bearing design options include cage type, bearing flange configurations (cylindrical and tapered roller bearings), radial internal clearance (RIC) or setting,

and precision level and lubrication. These options are selected based on the application’s speed, temperature, mounting and loading conditions, and will help achieve optimum bearing performance and life.

lubricants

Keep your business running smoothly with Mobil Synthetic Lubricants. Mobil’s range of top tier synthetic lubricants can lower operating costs by reducing power consumption, extending machine life and increasing equipment reliability and productivity. For enquiries please call the Engen Customer Service Centre on 08600 36436 or visit www. engen.co.za

197693 Mobil Synthetic Industrial Lubricants (Cogs) 130x210.indd 1

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BEARINGS AND LUBRICATION

Fig 4 and 5: Pressed steel cages offer general-purpose design and high-strength characteristics while a machined brass cage provides geometry for a better advantage with roller interaction.

radial or axial load, such as spursingle and double-helical geared systems that generate combined loads. They also offer a comparable speed capability compared with other bearings such as tapered roller bearings. Typically there are two cage types to consider when defining the bearing design options for an SRB in a gear drive (see Figs. 4-5). The pressed steel cage offers general-purpose design with high-strength characteristics that are often suitable for use in small to medium horsepower gear systems. For applications that are more aggressive from a marginal lubrication or inertial perspective, a machined brass cage provides geometry for a better advantage with roller interaction. Such applications include large horsepower gear systems, or systems that operate in extreme conditions. In addition, the design aspects of the brass cage and its positive impact on lubrication may make the bearing more favorable in high temperature environments and in applications where the potential for contamination is high.

Bearing RIC selection

SRBs selected for a gear-drive system require specific features that must be considered in the installation and mounting arrangement. After determining a suitable cage, a second bearing design option or specific feature that must be determined is the optimum radial internal clearance. Defining the RIC is particularly important in an SRB system because an SRB is a unitised design for which the outer ring is easily misaligned relative to the inner ring, cage, and roller assembly. Only one component (either inner ring or outer ring) can be interference-fit with either the shaft or housing to prevent relative motion, fretting wear particles, or additional heat in operation. Typically, the bearing component experiencing relative rotation or a rotating load zone is interference fitted to its supporting surface. The majority of applications have a rotating shaft with a rotating inner-ring load zone, so the inner ring is interference fitted with the shaft OD. Other applications, particularly planetary gear, may have either rotating outer rings or

rotating iner tial forces which dictate that the outer ring should have an interference fit. The interaction of inner ring or outer ring with this interference fit is to produce a reduction in the bearing RIC as mounted, versus the RIC which was purchased in the unmounted assembly.

Runaway situation

When the correct component has been identified for an interference fit, the other should be installed with a transition or positive loose fit. This is to facilitate ease of installation, and also for axial float in applications which employ multiple bearings on a shaft in a fixedfloat arrangement. Sufficient provision for displacement or float must be provided, otherwise the generation of parasitic axial loading of one bearing against the other may occur. If the

Surrounding environmental conditions such as low and/or high temperature, dust and dirt, moisture, and unusual mounting conditions can adversely affect a bearing’s performance float bearing cannot adjust and move axially to relieve this condition, the operating temperatures could increase and can continue to amplify this condition, possibly producing premature bearing damage or a thermal runaway situation. The unmounted RIC selected for an SRB is dependent on the mounting (interference fits), the operating loads, operating speeds, and the lubrication employed. These combine to directly affect the system heat generation. Generally, the greater the predicted or confirmed heat generation, the larger the selected unmounted RIC. The heat generated and associated thermal gradients present in most applications produce inner-ring operating temperatures which are greater than outer-ring operating temperatures. This differential is usually significant enough that the net impact is a reduction in bearing operating RIC versus the installed or mounted RIC.

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BEARINGS AND LUBRICATION

Best balance SRBs do not achieve thermally stable conditions if operating with a negative RIC or radial preload, unless a very controlled lubrication system is utilised to remove all excess heat generated. Consequently, the normal SRB unmounted RIC will be selected so that it is greater than the sum of RIC lost due Fig 6: In any power transmission system where mo- to interference fits tion is involved, the friction generated translates into and thermal gradiheat flux, producing a change in temperature or a ents for all combined thermal gradient operating conditions.

These options are selected based on the application’s speed, temperature, mounting and loading conditions This will help ensure that the operating RIC will have a value which is greater than or equal to zero in the thermally stable condition, producing the best

balance of rolling element load zone for stiffness and load capability in a thermally stable environment.

The Influences of temperature

As previously stated, simply choosing the right bearing is not enough. It is equally important to maintain a bearing’s performance with proper lubrication and monitoring. In any power transmission system where motion is involved, the friction generated translates into heat flux, producing a change in temperature or a thermal gradient. The gear contacts and bearings generate heat, which affects not only the mechanical elements of the systems, but also interacts with the lubrication scheme and the surrounding environment to create a stable, thermally balanced system. The resultant stabilised operating temperatures for the gear and bearing positions determine the effectiveness of the lubrication and the impact on bearing and gear function, whether positive or negative (see Fig. 6).

Negative impact

Successful bearing and gear performance is dependent upon generation of sufficient lubricant film thickness to separate the rolling/sliding contact surfaces. The film thickness, which can develop in these contacts, is an exponential function of

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THE SOUTH AFRICAN MECHANICAL ENGINEER

Food industry Sine pumps Masosine pumps combine low shear with high suction lift and are ideal for food processing applications.

Watson-Marlow \ Bredel \ Alitea \ Flexicon \ MasoSine VOL 61

June 2011


BEARINGS AND LUBRICATION

the lubricant viscosity at the contact operating temperature. As the operating temperature increases, the viscosity decreases, having a negative impact on the lubrication film thickness - making it thinner. Operating temperatures that generate lubrication films less than the minimum required will have a negative impact on performance by allowing surface asperity contact or interaction. This condition can result in an operating system that is unstable, and may operate at elevated temperatures. In this situation the result is a performance that is below predictions. The choice of lubricant for a bearing system greatly impacts the operating temperature.

Not excessive

A significant proportion of bearing heat generation during operation is produced by viscous interaction of the cage and rolling elements with the lubricant. The magnitude of this component of heat generation is dependent upon the lubricant viscosity and the operating speed. Both combine to have exponential impact on heat generation. Care should be taken to ensure the lubricant viscosity is sufficient to produce the desired minimum lubricant film thickness at the bearing operating temperature, but is not excessive. In general, more viscosity is good, but too much viscosity will produce substantial increases in heat generation and result in increased operating temperature, which cancels any positive benefits. If a bearing temperature issue is identified, it is important to review the original equipment manufacturer’s lubrication specifications to confirm they are being followed and are appropriate for the current equipment operating conditions.

its surrounding environment. The system seeks to establish thermal equilibrium with stabilized component operating temperatures. The greater the system complexity, the increased importance to assess the operating application characteristics, select the proper bearing type and features, and optimize the lubricant type, selection, and system.

Too much viscosity will produce substantial increases in heat generation and result in increased operating temperature, which cancels any positive benefits When a bearing system is selected, installed, and maintained to run at lower operating temperatures, the results should be lower operating costs, improved reliability, increased uptime, and less energy loss. The time and resources spent assessing application needs, selecting the correct bearing types and modifications, and determining the impact of surrounding environments can lead to enhanced system performance and total cost savings. Lynda Krebs, Timken South Africa, Tel:(011) 741-3877, Email: lynda.krebs@timken.com

By John Rhodes and Jim Madsen of The Timken Company.

Excessive interactions

The environmental temperature around the power transmission system is equally important since it establishes the stabilized base temperature for the system. As the environmental temperature increases, the system operating temperatures may have to increase to maintain a thermal balance. As previously noted, increases in operating temperature have negative impacts on lubricant viscosity and film thickness. Conversely, extreme reductions in ambient environmental temperatures may produce dramatic increases in lubricant viscosity and associated heat generation from excessive viscous interactions. This can lead to excessive lubricant film thickness, increased sliding and potential operating temperatures that are excessive.

Well worthwhile

Each bearing type has unique geometric and manufactured features that influence the amount of friction occurring during application operation. This, combined with prior discussions about application influences on heat generation, underscores the fact that a power transmission system is a complex assembly that has an interactive relationship with THE SOUTH AFRICAN MECHANICAL ENGINEER

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Market Forum A small, but high performer

HBM is introducing a new USB-based measuring amplifier to the market with their espressoDAQ amplifier series. Despite their small size, the modules developed by the metrology technology specialist HBM offer the usual high quality and performance capability, e.g. carrier frequency technology and A/D converter with a resolution of 24 bit. Individual modules can be directly supplied with voltage via the USB interface. In this case, a separate power pack is not necessary. Several measuring amplifiers can be operated via one USB hub and thereby also enable fully synchronized measurement systems. The amplifiers work with the "plug & measure" principle. The user can therefore obtain measurement results extremely rapidly. This is also supported by the RJ45 connector for transducer connection, which can be produced directly on site. In addition, the espressoDAQ measuring amplifiers support TEDS (Transducer Electronic Data Sheet), enabling simple and rapid configuration of a wide range of transducer types. The modules are supplied together with a simple to operate software, specially tailored to espressoDAQ, for configuration, data acquisition and visualization. The user requires just a few steps to obtain a measurement result. The measured data can also be exported using the most current formats. "The espressoDAQ platform takes full advantage of the bandwidth of USB High Speed technology. Portable applications can be implemented through direct operation with a measuring amplifier. A measurement system with the usual HBM quality is available to the user with espressoDAQ," says Marc Zürn, product manager at Hottinger Baldwin Messtechnik. Elton Murison. Tel: 012 809 9500; e-mail: e.murison@esteq.com

Earle Warne left, with father Colin Warne (centre), and Owen Warne

diversity of compressed air market requirements and recognised the importance of meeting these varied industry needs. In order to broaden market share, Atlas Copco acquired Ceccato Aria Compressa SpA in 1998 and in 2004 established the Multibrand Division with the main objective to complement and enhance the well entrenched and highly recognisable premium Atlas Copco brand. Headquartered in Brendola (Vicenza), Ceccato has more than 60 years experience in compressed air technology and offers a complete range of piston and screw compressors, dryers and ancillary equipment.

Growing the family

Warne’s Compressors, based in Jeppe, Johannesburg, is the latest addition to the Ceccato distributor family, part of Atlas Copco Compressor Technique’s Multibrand Division.

Warne’s Compressors is not entirely new to the Multibrand family. It was previously responsible for selling Creemers compressors; in 1996 Warne’s Compressors also started dealing another of Atlas Copco Multibrand companies – Balma.

Atlas Copco Compressor Technique identified the wide

Ian Wild. E-mail: ian.wild@za.atlascopco.com

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Market Forum Automated system on show

Accurate and reliable sample preparation is one of the most important prerequisites for quality assurance in the primary industry and many other industrial sectors.

Agreement for increased product range

Eqstra Industrial Equipment recently entered into an agreement with Atlas Copco South Africa’s Multibrand division to distribute the ABAC compressor range. Eqstra Industrial Equipment is an integrated capital equipment and leasing provider of value-added services in industrial, agricultural and materials handling equipment on the African continent and in the UK. Mariana Pretorius, Director, Eqstra Industrial Power, explains: “The ABAC range of compressors complements Eqstra Industrial Equipment’s current product range and supports our philosophy of providing best in class brands. Atlas Copco’s reputation for marketing superior quality branded compressed air products is in tandem with our philosophy of delivering first class products and value added services. The Eqstra Industrial Equipment strategy is to double in size every five years and we grow organically through selective acquisitions within the industrial equipment and materials handling sector. Through diversification of products and services we provide a complete solution to our customers. Our customers are accustomed to service excellence and we are confident that Atlas Copco Multibrand will meet our product demands on time every time as we share the same service ethic.” The Atlas Copco Multibrand portfolio presents an extensive product range including professional and industrial reciprocating piston compressors, oil lubricated screw compressors (either fixed or variable speed technology), oil-free units, compressor management systems, quality air products (including dryers and air receivers), spares, etc, to satisfy air demands as well as many and varied applications.

The Polab APM Plus is claimed to be the most compact and flexible sample preparation module in the world. This Polysius system offers fully automatic sample preparation, a high sample throughput rate, clear and simple operation, easy installation and compatibility with existing systems.

The products feature industry-leading low noise levels, reliable, cost effective, energy efficient, easy to install compressed air solutions. Strong, long term business relationships with reputable compressed air companies with solid coverage across the continent, ensure unequalled, round the clock after sales and technical services inline with Atlas Copco’s well known service ethic. Mariana Pretorius. E-mail: marianap@sie.co.za

Polysius is a German global specialist in the design and supply of complete plants including grinding and other processing and automation equipment to the cement and minerals industries. Polysius has led the minerals and cement industries with innovative AG, SAG, ball mill and scrubber designs and its designs and technology have set industry benchmarks for many new developments. The Polycom High Pressure Grinding Roll is the company’s answer to equipment with high energy and environmental efficiency. Following the installation of the first unit in the cement industry 25 years ago, more than 270 Polycoms are now in operation worldwide, with the minerals industry having also successfully adapted this technology.

From left to right: Paul Combe, Technical Sales Manager and Mariana Pretorius, Director - Eqstra Industrial Power with Ian Wild, Atlas Copco SA Regional Manager Multibrand – Sub Saharan Africa

Pia Guertler. Tel: 011 236 1218; e-mail: pia.guertler@thyssenkrupp.com

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Market Forum Saving energy

Magnet has played a major role in the Sappi Tugela River pump station upgrade project on KZN’s North Coast. “Magnet is involved with Eskom’s demand side management programme aimed at alleviating the country’s electrical energy shortage. The company was commissioned by Sappi to undertake an audit of the plant, with a view to possibly upgrading one of the pumps,” says Brian Howarth,

Magnet has played a major role in the Sappi Tugela River pump station upgrade project on KZN’s North Coast. This project has delivered high levels of energy savings, as well as reducing the peak time load on Eskom’s electricity grid

Magnet’s managing director. “At the same time, Eskom was looking for ways to reduce the load on its grid during peak hours. The size and scope of the project increased from the initial focus on a single pump upgrade, to a comprehensive turnkey energy efficiency project, involving the installation of seven new pumps at the plant, new control valves and a new control system and control philosophy.” The Tugela Mill’s pump station is now capable of pumping the mill’s daily requirement of water in less than 20 hours. There is also a shift in load from peak periods to off-peak periods, using existing water storage capacity without impacting on the supply of water to the mill. The upgrade allows for an average shift of 1,85 MW away from the peak demand periods during the day and an average 0,185 MW energy saving throughout the rest of the day. A critical feature of this project is that in addition to moving load out of the peak demand periods, the overall plant demand is always lower than the previous baseline. Overall, the plant’s kWh consumption has been reduced by around 25 %. Brian Howarth, Tel: (031) 274 1096; e-mail: brianh@magnetgroup.co.za

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Market Forum A scientific and structured approach

Monitoring for maintenance

Condition monitoring is a key element in planned maintenance, allowing remedial action to be taken to avoid the high cost and lost time consequences of component failure. Condition monitoring of plant and equipment is based on trend analysis and regular sampling.

Multotec’s CY-i suite of cyclone sizing and selection software has been upgraded to include the sizing of DMS and classification cyclones and incorporates several other programme enhancements. The software suite was developed to equip Multotec customers with a scientific and structured approach to making the initial selection of a DMS or classification cyclone solution, by using variables within their own plant configuration to determine cyclone configuration. Ian du Plessis, product manager (classification cyclones) at Multotec, says: “The latest enhancements have laid an excellent foundation for the development of an even more sophisticated version of CY-i which will provide engineering companies with a greater depth of information with which to make fully informed decisions. The CY-i software allows for a spectrum of data to be selected and then calculates a mass and water balance. After using the initial selection software, customers have the option of automatically generating an e-mail communicating this data to Multotec’s cyclone specialists. These engineers refine the data, using a greater selection of variables to provide the best solution for specific applications together with a technical and commercial proposal.

Concor Plant has close to four hundred major items being monitored on the WearCheck system

Concor Plant has close to four hundred major items being monitored on the WearCheck system. “Condition monitoring plays a primary role in maintaining our extensive fleet of construction plant and equipment,” says Eric Baker, Concor Plant’s technical manager. “This proactive approach has paid significant dividends in terms of eliminating mechanical failures and generally optimising our fleet’s operational efficiency and performance. Since we engaged oil and fuel analysis specialists WearCheck to initiate a continuous programme of oil and wear particle analysis on our plant in 2009, the savings have been substantial.” All large frontline machines fitted with hour meters are monitored at regular intervals at site level to flag potential problems. The WearCheck system has been implemented at all Concor Plant sites, where samples of diesel, oil and coolant are taken from equipment at predetermined times. For example, engine oil is sampled every 250 hours. Each piece of equipment has a unique plant number and each component is tested and flagged separately. Samples are analysed at a central WearCheck laboratory and where these tests flag a potential problem, additional testing is carried out to identify the root cause. At least 90% of all samples are processed within 24 hours. Concor Plant sites have internet access to the data on their specific machines, while the company’s head office can access the data for the entire fleet. The system also allows managers and directors to receive critical and urgent data. Francis Berner, Wearcheck, Tel: 031 700-5460

The MAX 1450 ceramic lined dense medium cyclone

The software also provides access to detailed product information on the Multotec range of cyclones, which further enables an informed decision. The new DMS software is similar to that of the classification selection software, but goes even further to provide guided inputs for the selected industry. Ian says this eliminates a lot of guesswork and makes the process much simpler. Ian du Plessis. Tel: 011 928 4132; e-mail: ianp@multotec.co.za

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Market Forum Efficiency and reliability

German multinational, Voith Turbo, is renowned for the design and manufacture of class leading hydrodynamic variable speed drives (VSDs).

The VSDs operate 24/7 and meet industry expectations for equipment that delivers maximum economy and reliability in upstream applications such as gas lift, gas pipelines, offshore platforms, oil pipelines etc, as well as downstream applications including chemical and refrigeration processes, hydrogen recycling processes, wet gas units and refineries. Compact and robust, with integrated lube oil system supplying oil to the driver and the driven machine, Voith VSDs are easy to maintain and offer excellent control accuracy and control dynamics. With power of 100 to 50 000kw, Voith hydro-dynamic VSDs are capable of transmitting speeds of 100 to 20 000 rpm and present numerous other industry advantages including: 99.9% reliability; 99.8% availability; optimum price/performance ratio; application in explosive, dusty, extreme temperature environments; long, reliable operating periods (MTBF); and vibration damping.

Voith VSDs have been engineered to efficiently and reliably control pumps and compressors to reduce operating costs and increase profitability and in upstream and downstream production processes.

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In a gas lift application, Voith drives prevent oil and gas being pushed to the surface by providing stepless control of the required injection flow and pressure. Pump lines, and pump stations must accommodate transporting multiple products, pressure losses, different altitudes, and VSDs’ stepless control reduces energy consumption, increases motor and pump service lives and provides tortional vibration damping. In loading pump applications, Voith VSDs allow the pump to be switched off while the motor is still running and a stepless flow rate control, irrespective of back or suction pressure. Roy Webster. Tel: 011 418 4000; e-mail: roy.webster@voith.com

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Market Forum Making weighing easy

An automated plant-wide weigh batching system engineered by Flexicon Corporation simultaneously weighs up to seven major ingredients received in bulk bags and unlimited minor ingredients received in 23kg sacks, pails or boxes, and conveys weighed batches to a downstream blender that feeds a bulk bag filler and a paper sack filling machine. System components supplied by Flexicon include: five lossof-weight Bulk-Out bulk bag dischargers with large surge hoppers and rotary airlock valves; two loss-of-weight bulk-out bulk bag dischargers with small surge hoppers and flexible screw conveyors; two loss-of-weight bag dump stations with flexible screw conveyors; a check-weighing hopper; a Twin-Centrepost bulk bag filler; a Pneumati-con dilute-phase pneumatic conveying system including blower, filter receiver and conveying lines; and a programmable controls package. Each of the large surge hoppers accommodates the entire contents of a bulk bag containing a major ingredient, affording operators sufficient time to load full bags into the frame as material is removed at high rates through a common pneumatic line terminating at the filter receiver.

Up to seven major ingredients and unlimited minor ingredients are weigh batched simultaneously, check-weighed, and conveyed mechanically and pneumatically for delivery through a filter receiver to a blender that feeds a bulk bag filler and a paper sack filler

The smaller surge hoppers on the loss-of-weight bulk-out bulk bag dischargers provide sufficient capacity to allow reloading of major ingredients conveyed at lower rates by small diameter flexible screw conveyors, providing higher accuracy than possible with large rotary airlocks. Also conveyed by loss-of-weight flexible screw conveyors are minor ingredients, which are tipped manually at either of two tipping stations equipped with vacuum filtration systems to contain airborne dust. All flexible screw conveyors discharge into a common check-weighing transition hopper mounted on load cells that confirms batch accuracy before feeding the material through a rotary airlock into the aforementioned pneumatic line. Flexicon Africa: Tel: 041 453 1871; e-mail: sales@flexicon.co.za

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Market Forum High impact

EnviroServ has introduced a powerful and technologicallyadvanced new hammer to the South African market. The Fractum Breaker is the most powerful hammer in the world, and is capable of delivering up to 400 000 joules of energy per stroke, compared with just 6 000 joules from a conventional hydraulic hammer. The kinetically-powered machine was imported from Swiss-based manufacturer Fractum GmbH in August 2010 by EnviroServ Plant & Equipment, a division of the EnviroServ Group, which provides a complete range of earthmoving equipment to all EnviroServ operations. EnviroServ Plant & Equipment director Detlef Klapthor points out that the fractum breaker is attached to a 50-ton Hyundai R500LC-7 excavator, supplied by HPE Africa. “In order to provide the best all-round service, the state-of-the-art fractum breaker has been attached to a powerful and rugged Hyundai excavator, which has proven to be highly-reliable when transporting and operating the breaker.” The fractum breaker consists of a stainless steel tube, which is 70cm in diameter and 8,5m tall. Inside the tube are a coupler, and a steel-tipped weighted hammer, known as a ‘bullet’. The entire 10-second cycle of the breaker begins when the coupler is lowered down the tube, before engaging with a fitting on the upper surface of the bullet. A cable attached to the coupler raises it up the tube, in turn lifting the bullet. The bottom of the tube is placed on top of the selected material that needs to be broken, before gravity accelerates the 5-ton bullet downwards onto the target material. According to Detlef, the operational costs of the fractum breaker work out to less than R10 per ton broken. Kirsty Denholm. Tel: (011) 397 4670; e-mail: kirsty@hpeafrica.co.za

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Market Forum A simple philosophy Understanding diagnosis

The new SKF Microlog Adviser Pro is a ‘standalone’ device and doesn’t rely on prior measurement data or require advanced analytical software. It is ideal for ser vice, maintenance, inspection, and diagnostic applications. It comprises an intuitive user interface, simple wizard-driven measurement instructions, and an automated analysis system based on pre-programmed ISO standards. Green, yellow and red colourcodes quickly and clearly indicate test status, invalid or abnormal measurements, and machinery condition. The SKF Microlog Advisor Pro features an easy-to-read, 25 600-line resolution colour display, an advanced computing engine, high-performance data acquisition hardware and documented solutions programme technology, and a 40 kHz Fmax. The unit also features extended battery life for up to eight hours of continuous use, as well as easy memory upgrades via SD card. It can be provided with a PC-based Analysis and Reporting module. Once data is uploaded, it is automatically shown in the application’s main window, and a single mouse click is all that is needed to view the data in a powerful, interactive graphical plot. The analysis and reporting module provides a range of post-processing features and a full range of SKF Microlog accessories are available. A range of application modules are available, allowing users to create a custom device that suits their individual requirements. . Samantha Joubert, SKF SA. Tel: 011 821 3500; e-mail: Samantha.joubert@skf.com, www.skf.com/cm/microlog

Bearings International operates with a simple philosophy; if the client has a problem, the company wishes to be part of the solution. A recent example of offering solutions was for a local engineering company, which was contracted by a steel mill, manufacturing tubes, to design a transfer roller table facility taking the product directly from the cooling beds to the non destructive testing inspection and product marking and identification lines.

The old method, using standard plummer block arrangements, proved unreliable, when the tubes fell onto the roller tables. Invariably it meant a movement of the bearings within the housing assembly, creating a stoppage to relocate the units which, in turn, required opening the assemblies and having to realign, measure clearances, relubrication and reassemble before the process could return to full production. This procedure proved to be not only time consuming, but very costly, while creating obvious delays to the specified delivery schedules. The Bearings International solution offering was in the form of the Dodge ISN units offering real benefits: solid steel cast housing; compatible with SN/SNU dimensions; comes complete with clearance set and greased; seals sit on the outside of the inner ring (no shaft wear); patented ISN “push/ pull” adapter mounting design; eliminates the need for feeler gauge measurement; and has triple labyrinth seals for wet or dry conditions and non contact sealing. Ian Robertson. Tel: 011 345 8011; e-mail: ianr@bearings.co.za

GSC Workshop Going green is no longer a choice, it’s a business imperative! The Green Supply Chain Workshop is a joint initiative between CILTSA (Chartered Institute of Logistics & Transport), the CGCSA (Consumer Goods Council of SA) and “Supply Chain Today” magazine. Come and hear how it’s done at the Green Supply Chain Workshop held on Sunday afternoon, 26 June 2011 If you would like to attend the workshop and / or the SAPICS Exhibition and Conference, please go to www.upavon.co.za.

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Market Forum Reusing wastewater

Water and wastewater company Veolia Water Solutions and Technologies South Africa has partnered with KV3 Civil Engineers in a R100-million project to make the Tubatse Ferrochrome smelter in Steelpoort a zero effluent plant. The partnership is aimed at conserving the water in the Steelpoort River by assisting the reuse of wastewater without the risk of salinating process water. This was accomplished through the use of novel process designs and equipment supplied by Veolia Water Solutions & Technologies South Africa. The plant treats all water outflow on the smelter’s site, including industrial storm water, contaminated groundwater, treated sewage water and industrial effluent containing a high concentration of dissolved salts.

BE REMEMBERED BEFORE, DURING AND AFTER AFRIMOLD

T

he organisers has got together with “Advanced Materials Today” to make this year’s Afrimold Exhibition one to remember.

We are preparing a Visitors Catalogue which will feature a floor plan, a list of exhibitors and sponsor details. The catalogue will be in all the delegate bags and will be given out from our stand at Afrimold. We are all hard at work publicising the Exhibition and your presence in the Afrimold Catalogue will serve as a permanent record of your company’s products and services, before, during and after Afrimold. Get in touch with us to place your advertising and/ or to buy editorial in this prestigious issue.

Limpopo MEC for Agriculture, Mme Dipuo Letsatsi-Duba, officially opened the zero effluent plant on 19 November 2010

According to Frank Rosslee, Engineering Manager, Tubatse Ferrochrome, the true value of this plant lies in the fact that by treating the contaminated groundwater and other wastewater sources, a large volume of water is re-used, without releasing anything harmful into the surrounding environment. “The added environmental gain from the project is that the volume of water that the smelter needs to extract from the Steelpoort River is reduced, which translates into more fresh water for the residents in the fast developing rural areas downstream,” he says. “The plant is evidence of Samancor Chrome’s unfailing commitment to environmental conservation and the future well-being of its surrounding communities.” He notes that the added advantage to the smelter is that its process water quality has improved considerably, which assists in enhancing the life expectancy of all its major process equipment. Gunter Eencken. Tel: 011 663 3600; e-mail: info.vwsenvig@veoliawater.com

To advertise in “The Annual Mechanical Engineering Buyers Guide”, contact Louise Taylor on 011 781 1401, editorial@promech.co.za

Advertising Contact: LOUISE TAYLOR, “ADVANCED MATERIALS TODAY” on Tel: (011) 781-1401, Cell: 082 898 3073 Email: editorial@promech.co.za

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Market Forum A preferred company

Bateman Engineered Technologies (BET) has been given an order for a semi-autogenous grinding (SAG) mill to be used in the primary grinding circuit of a 9 400 t/d iron ore concentrator at CML Metals Corporation’s Iron Mountain Project located near Cedar City, Utah, USA. BET comminution manager, Robin Melville says the mill, which is 8.53m in diameter, has an effective grinding length (EGL) of 3.678m, is powered by a 6.5MW drive, and will process up to 9 400 tons per day. “It is designed to work in cooperation with an existing ball mill and will thus produce a particularly fine grind of the Magnetite product,” he says. One of the more salient features of the project is the global manufacturing process being instituted. This means that various aspects of the mill are being manufactured in several different countries, under the supervision of BET. “Our experience and expertise in these circumstances will ensure that all the parts come together to our very demanding standards,” says Robin.

Model of the SAG mill for the Iron Mountain Project.

Johnathan Weber, Project Procurement Manager of USbased Samuel Engineering which placed the order on BET, says that BET was preferred because of its renowned track record, competitive pricing and excellent service delivery. “Bateman has an excellent reputation, which it has more than justified in this project. To date they have met all project deadlines and will no doubt meet the exceptional time frame of 11-12 months for completion,” says Jonathan. Robin Melville on +27 11 201 1327 or email robin.meliville@ bateman-bet.com

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Market Forum Key to success

“Our main activity is abrasive blasting, coating, hull cleaning and tank cleaning of the ships, offshore supply vessels and oil rigs, brought into the dry dock at the Port of Cape Town for repair and refurbishment, ” says owner of South East Marine Services, Hans Petring. “When we first started out we hired equipment from another compressor hire company but Rand-Air continued to visit us so we decided to give them a chance in 1985 and there was no turning back.” Hans explains that his company hires the occasional small generator from Rand-Air but that their core interest lies in the range of compressors from 140 cfm up to 1000 cfm. “A few years ago I told Rand-Air that I needed a higher capacity compressor for some of the larger jobs I was undertaking. They listened to my needs and promptly ordered an Atlas Copco 1000 cfm machine – the first of its kind to be used by a compressor hire company in South Africa. This willingness to please its customers is inherent in all of Rand-Air’s staff and is one of the main reasons we have such a strong, enduring relationship.” “Besides the obvious convenience factors and the high levels of service provided by Rand-Air’s team, there is another benefit to hiring these well-maintained and high-quality Atlas Copco compressors. The machines are designed and engineered to operate at the constant pressures so crucial to the superior sandblasting finish required to achieve the desired profiles needed for painting,” Hans explains. “At the end of the day, delivering the correct pressure and volume in this industry is imperative. If this is not achieved, there is a waste of grit during this process, which leads to loss of production, time and ultimately money,” he adds.

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On the Move

Index to Advertisers Bill Muller

Francois Sieberhagen and Kenneth Dougan have been appointed Electronics Support Engineers, Johannesburg and Pinetown, respectively. AJ Coetsee has been appointed technical trainer at SEW Eurodrive Johannesburg. Francois Sieberhagen

Kenneth Dougan

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AST Pyroshield Inside Front Cover Atlas Copco 12 Bearings International 38 BMG Outide Front Cover Busch 42 Engen 32 Engineer Placements 44 Esteq 20 ILS 45 KSB Pumps and Valves Outside Back Cover Multi Alloys 30 Monitor Engineering 35 26 Producut Sigma 14 SKF 18 Timken Inside Back Cover Watson Marlow 34 WEIR 10 40 Zest

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SA Mech Eng June 11 small linked