Autumn 2012
Issue 01
Cairns Regional Council improves redundancy of its wastewater system by partnering with Hydro Innovations One of the constant challenges of maintaining wastewater systems in cyclone prone areas is ensuring that your equipment is always operational in the face of adverse conditions so that public health and environmental disasters are averted. As part of this requirement, Grahame Dunstan, Co-ordinator for Wastewater Services for Cairns Regional Council (CRC), explored the options for emergency pumping during power outages at the White Rock #1 pump station. The solution had to help ensure that CRC's wastewater services in the greater Cairns area remained operational and effective during tropical storms and in emergency situations.
'Experience has taught us that during extreme weather conditions and in emergencies not all your equipment may perform the way you would expect. So it's important to try to implement mechanisms that will help safeguard against poor performance and make a system as failsafe as possible,' explained Grahame. The council currently has numerous emergency generators to help maintain wastewater services in the event of loss of mains power. 'Our generators are not always one hundred percent reliable. We have had situations where an emergency generator has failed to kick in when it was most needed. So for us, generators can be a liability in an emergency,' he said. Grahame undertook some research, comparing pumps, associated costs and their benefits before deciding that an emergency stand-by pump was a viable alternative to installing another generator and would help improve redundancy of the system. Already familiar with the Gorman-Rupp name he looked closely at the company's (continued on page 2)
The Gorman-Rupp V6-SCP stand-by pump.
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Energy Efficiency in Wastewater Pumps With increasing energy costs and emerging carbon dioxide taxes, engineers and designers are carefully scrutinising the energy efficiency of wastewater pumps. In doing so, the responsibility to reduce energy consumption needs to be carefully weighed against any ramifications this “improved” efficiency may cause. The McNally Institute says ... ”High efficiency is desirable, but it will be a maintenance nightmare. High efficiency means tight tolerances and smooth passages ... you will spend a lot of downtime and money trying to maintain those two requirements”. There are many aspects that need to be assessed when evaluating sewage pump efficiency. Consideration needs to be given to the pump's non-choking capability and the ease with which a choke can be removed. It makes no sense to install the most hydraulically efficient pump, only to have to have it serviced daily to remove blockages. Ensure the pump is easy to access and maintain. If accessing and maintaining the pump is not a simple process, removing a blockage or troubleshooting could prove to be a major and costly operation.
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Cairns Regional Council improves redundancy of its wastewater system by partnering with Hydro Innovations (continued from page 1)
emergency stand-by pumps and chose to partner with Hydro Innovations, Gorman Rupp's authorised distributor in Australia. 'We were already using other Gorman-Rupp equipment and their track record to date was excellent. Their products are very reliable and robust. We searched for a local supplier and found Hydro Innovations. They were very professional and helpful in meeting our needs for an emergency stand-by pump,' explained Grahame. To meet their requirements, Hydro Innovations installed a self-priming, centrifugal, diesel pump with auto-start. Called a Gorman-Rupp V6-SCP, the above-ground pump has a suction line that goes down into the wet well and a float switch that activates the auto-start. The unit only runs when required and remains silent at all other times. The V6 provides superior solids-handling and increased pressure capabilities. It delivers higher pressures and flows than any other self-priming sewage pump on the market and is also the most efficient pump in its class. As with other Gorman-Rupp sewage pumps, the V6 is fitted as standard with a unique and patented self-cleaning wear plate system that enables the pump to handle stringy materials and rags that would block other pumps. Enclosed in a sound-attenuated metal canopy, the V6 emits low noise levels. Lockable doors prevent unauthorised personnel from tampering with the pump, fuel, engine or controls. Fuel capacity allows for a minimum 24 hours of continuous operation. According to Grahame the cost to purchase the V6 was comparable with the cost of buying another generator. In addition, it also eliminated the need to have to install variable speed drives in the switchboard to make the generator operational. Since having the stand-by pump installed in early 2010, Grahame and his team have seen the V6 perform under emergency conditions. 'During Cyclone Yasi, we had to make use of the pump and it performed outstandingly. It kicked in straight away and did what it was meant to effectively,' said Grahame. Apart from reliability Grahame also found that the Gormann-Rupp V6 required less fuel to keep it operational.
Maintaining Centrifugal Pumps
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'Each of our generators is eight times more expensive to run when compared to the V6 and the maintenance costs associated with the generators are far higher than those of the V6. The generators are also people intensive to maintain. Whereas the V6 requires less maintenance and uses up less of our people's time. 'The V6 pump has helped reinforce the operational capability and efficiency of our wastewater system during an emergency situation. It's reassuring to know that we have the V6 in place,' explained Grahame. 'Choosing to partner with Hydro Innovations was also the right decision. They grasped what was required immediately, have a very good understanding of their products and their backup service has been excellent,' said Grahame.
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Safety is always the number one priority. Electrical pumps come with the risk of electrocution. So always make sure the pump is switched off and be vigilant of live wires. Choose pumps that are easy to access and maintain. Always refer to the pump's operational and maintenance manual when performing any routine work. If your centrifugal pump is a self primer, select a suction line that is large enough to avoid NPSH problems, but small enough to keep priming times reasonable. Always use good quality gauges on your pumps. Gauges are your “window” to a pump's performance and your number one troubleshooting tool. A good pump will have oil sight glasses for bearing oil or seal oil if pertinent. Keep regular checks on these to ensure that correct oil levels are maintained and that the oil remains free of impurities. Remember to check the belts of any vee-belt driven pump regularly and re-tension when necessary.
Do quarterly shut-head readings to ensure the pump is delivering the desired performance. Keeping pump clearances “tight” has several advantages: a. Energy use is kept to a minimum. b. Parts wear slower as less abrasive material is passing wearing surfaces. c. Solids handling pumps choke less if clearances are at their factory settings. Keep a spare rotating assembly for emergency break-down.
VFDs on Pumps Over the past few years the use of Variable Frequency Drives (VFDs) in pumping applications has increased. There are many reasons for their rising popularity. Not only do they allow operators to vary pump speeds to match in-flows or maintain constant pressures, they can also improve equipment life by soft starting and stopping, reducing shock on start-up as well as water hammer when stopping.
New Emergency Sewage Bypass Units Released Hydro Innovations would like to introduce the latest range of acoustically rated, diesel driven sewage pumping bypass units. Working in collaboration with our customers and our supplier, Gorman-Rupp, these units have been purposely designed to meet the needs of Australian water authorities and councils.
The price of VFDs has also been falling steadily over time, making them a very affordable and attractive option. In some instances where power cable lengths are long, savings in capital costs are possible as less current is required to travel through the cables to start equipment.
V6-SCP
The Gorman-Rupp XXXXXX
At the heart of these units are the Gorman-Rupp Ultra V and Super T series sewage pumps. Driven by the latest in diesel engine technology, these pumps feature unique controls and ancillary equipment. The new units are all equipped with non-return valves, air release valves and casing drain kits. The drain lines from the air release valves and casing drain kits are piped to threaded connections in the canopy walls to make it easy for operators to attach lines back to the wet well. Once connected, the units are fully operational. Example of typical VFD unit.
In particular, VFDs are proving invaluable when coupled with self-priming pumps. Self-priming pumps are on the ascent in both municipal and industrial wastewater applications as well as in mining and even water transfer applications. They deliver true life cycle cost benefits, easy access as well as tangible OH&S advantages. When combined with a VFD, the operator is provided with greater control over the speed of the self-priming pump's motor and therefore, its overall performance.
The controls have been specified to suit the needs of Australian operators. They feature all the usual safety shut-down features, as well as the ability to convey this information via telemetry systems. In addition, the controls detect “no-flow� situations and low fuel conditions. Other standard features of these units include self-contained, bunded fuel tanks; rain caps for the exhaust; a polycarbonate panel on one door to view the controls and sound attenuation of 67dB(A) at 7 metres. The new diesel driven sewage pumps can deliver flows from just a few l/s through to 200 l/s and with heads to 100 metres. For more information on these units please call Hydro Innovations on (02) 9647 2700 or email info@HydroInnovations.com.au
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VFDs on Pumps
Energy Efficiency in Wastewater Pumps
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pump. Items that “hide” during scrutiny are discharge connection losses, and the lowering of delivered efficiency during the periods between wear ring renewal and wear ring replacement time. Efficiencies can quickly dissipate when clearances start to “open up” with wear.
A self-priming pump needs to run fast enough to prime, but sometimes this is faster than the pump needs to run to provide the pumping duty. A self-priming pump may also be required to pump deep into a wet well. Two factors that affect the Net Positive Suction Head (NPSH) safety margin are the friction losses through the suction line and the NPSH required by the pump. In both cases, a VFD can help negate these elements.
For instance, in the case of submersible pumps that rely on radial clearances, the only way to change their wearing rings is to open the wet well lids, hoist the pump from the pit and then send it to the workshop where the wearing rings are chiselled out.The process is arduous, time consuming and far from efficient.
Where the pump needs to run fast to prime (say 1800rpm), but has a slower duty speed (say 1400rpm), a VFD can eliminate the problem. The VFD simply drives the
Submersibles that use axial clearances are slightly more efficient but they still need to be pulled from the pit, cleaned and their clearances adjusted via jacking screws.
pump at 1800rpm till it primes (a limit switch on the non-return valve can send an “I'm pumping” signal to the VFD), and then it helps the pump drop back to 1400rpm. Where a very high suction lift is required, a pump's “off level” can be “reached” by slowing the pump down at the end of a “pump-down” cycle to reduce both suction line friction losses and the NPSHr of the pump. As can be seen, the benefits of VFDs in pumping applications are numerous and in some cases, they can be critical in being able to satisfy the duty completely.
The hydraulic efficiency of the pump and its ability to maintain its hydraulic performance also needs to be examined. There are also some hidden inefficiencies that need to be considered when evaluating pump efficiency. This is particularly the case with the most commonly used pump in the sewage system - the submersible
Hydro Innovations
Assessing the efficiency of a sewage pump is complex. The subject is covered in great detail in a white paper entitled Selecting the Right Sewage Pump, Don't Lose the Pump Efficiency Game. Contact Hydro Innovations to obtain a free copy.
Sewage Pump Efficiency When considering the efficiency of a sewage pump remember to asses the following key criteria:
Hydro Innovations Unit 1, 26 Day Street Silverwater NSW 2128
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The non-choking capability of the pump
Telephone: (02) 9647 2700 Fax: (02) 9647 2709 www.HydroInnovations.com.au
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How easy it is to remove a choke
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How easy it is to maintain the sewage pump
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The hydraulic efficiency of the pump
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The ability of the pump to maintain its hydraulic efficiency
Disclaimer Any representation, statement, opinion or advice, expressed or implied, in this publication is made in good faith but on the basis that Hydro Innovations, its agents and employees are not liable (whether by reason of negligence, lack of care or otherwise) to any person for any damage or loss whatsoever which has or may occur in relation to that person taking or not taking (as the case may be) action in respect of any representation, statement or advice referred to in this newsletter.
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