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T H O M A S S E N C O M P R E S S I O N S Y S T E M S

Free Floating Piston™


Free Floating Piston ™ Revolutionary reciprocating It is now more than a century ago that Mr Thomassen first began to make gas engines. He soon extended his activities to include the design and production of reciprocating compressors and what started out as a small, local company has grown into a major compressor supplier with sales outlets and service at strategic points around the globe.

Thomassen Compression Systems (TCS) supplies heavy-duty reciprocating and oil-flooded screw compressor packages as well as rerated/rebuilt centrifugal compressors. In addition, we offer full service, installation, spare parts and repairs, maintenance and troubleshooting, round the clock, all over the world. Exports currently account for more than 80% of sales and our customers include oil refineries, gas & oil exploration and production companies, and petrochemical plants.

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The weakest point becomes the strongest

compressor design Rider ring wear

An elegant solution

Due to ever more stringent environmental regulations,

TCS has come up with an extremely elegant solution.

there is a trend towards the use of non-lubricated com-

A design that virtually eliminates rider ring wear

pressors. Such machines, however, require increased

by allowing the piston to float freely on process gas.

maintenance because rider ring wear is unpredictable.

The advantage of this revolutionary idea is that wear

Indeed, certain process and gas conditions accelerate

only takes place for very short periods during startups

wear so drastically that running time can be reduced to

and stops.

as little as a few hundred hours. Given today’s commercial pressures - that dictate running times of three

This development removes in one stroke the weakest

years or more - this situation clearly presents owners

link in the chain as far as compressor component failure

of compression systems with a problem….

is concerned. What’s more, the full benefits of increased lifetime of other parts that are subject to wear can now be realized. The industry’s requirement for at least three years of uninterrupted running time with nonlubricated cylinders is finally within reach. 3


To l u b r i c a t e o r n o t t o l u b r i c a t e

Environmental constraints

process gas or environmental regulations dictates that

The design of Thomassen’s reciprocating compressors

the piston must be supplied non-lubricated, wear

- which are custom-built and meet or exceed API 618 -

increases dramatically. In some cases this action is

is based on the horizontal balanced opposed type. If

similar to that of an eraser. So non-lubricated compres-

the moving parts are lubricated with oil, then wear is,

sors need regular maintenance and a second back up

in general, acceptable. However, when the type of

machine is usually essential to ensure the levels of availability required in today’s production processes.

Research-led results One approach was to attempt to improve the properties of the rider ring/liner materials. However, so far this has only produced marginal improvements. Thomassen took another approach - one that was Pressure vs time measurement

much more fundamental - to rethink the basic principles of compressor design. A feasibility study covering the full range of construction principles led to the creation

Top view measured pressure distribution

of a revolutionary new design, which equips the piston with a gas bearing:

Top view calculated pressure distribution

Side view measured pressure distribution

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The Free Floating Piston™


How does it work? The principle of the Free Floating Piston™ technique is that the weight of the

piston is carried by the process gas itself. During the compression stroke, the interior of the piston is filled with process gas at high pressure.

No change in capacity The bearing layer between the rider rings and the cylinder liner is in the order of 10 to 50 microns, and the flow required to lift the piston is less than one percent of the compressor’s capacity. The new construction compensates for this, so net compressor capacity is the same.

Due to the pressure difference, the process gas flows out at the bottom of the piston, ensuring that there is no physical contact between rider rings and cylinder liner.

No friction

Rigorous testing The system has been subjected to rigorous static and dynamic testing on Thomassen’s in-house heavy-duty test air compressor. This was followed by a successful pilot test in a heavy-duty production hydrogen compressor at a customer’s site.

Actual Experience

As a result, rider ring wear is reduced to practically zero, resulting in substantial increased rider ring lifetime.

The first compressor to be fitted with our Free Floating Piston™ has meanwhile clocked up more than 60.000 hours of trouble free operation.

The design of the piston itself has been adapted as follows: • to create constant pressure, the rider rings have been relocated between the piston rings • regular compressor valves that react to differences in gas pressure have been installed in the piston faces, enabling gas to enter the interior of the piston flow nozzles have been integrated in the rider rings and a profile machined • on their lower surface to create a bearing layer under the piston

Fail-safe


Key advantages of the F r e e F l o a t i n g P i s t o n™

practically no rider ring wear

increased lifetime of piston rings and stuffing box elements, due to the piston maintaining its centralized position

no lube oil pollution of process and valves, no cylinder lubrication system, no lubrication costs

reduced preventive maintenance costs (time and materials)

reduced production losses

increased reliability and availability

a major reason for having a spare compressor is eliminated

suitable for all kinds of process gases

the design can be applied to existing compressors

no risk (fail-safe)

lower power requirement

lower sound levels

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Putting the principle into practice: Thomassen Compression Systems’ Free Floating Piston ™ technology


T H O M A S S E N C O M P R E S S I O N S Y S T E M S

Head Office Thomassen Compression Systems Havelandseweg 8-a PO BOX 99 6990 AB Rheden

Tel: + 31 26 4975200 Fax: + 31 26 4975201 E-mail: tcs@thomassen.com For Service Operating Companies, Sales Offices & Agencies, please visit our website.

www.thomassen.com

TCS-4-04/08-2940

The Netherlands


Free Floating Piston