ECS Engineering Services is to install a replacement screw pump at Wessex Water’s Avonmouth Sewage Treatment Works (STW), helping secure the capabilities of the facility for decades to come.
Avonmouth STW serves a population of about 1,000,000 people in Bristol and the surrounding towns and villages. One of its key pieces of process plant is a very large screw pump which has been in operation for around 40 years. However, it had become badly worn and effectively reached the end of its useful service life.
ECS was asked to inspect the screw pump and make some proposals for its overhaul or replacement. Jake Laughton, the ECS engineer who led the inspection says: “Much of the pump is in a serviceable condition and can be retained, however, the screw itself has reached the end of its life and needs to be replaced.”
At 21 tonnes, 20 metres long, 3.1 metres in diameter and able to pump 3,645 litres of water a second, the screw is simply enormous. ECS has arranged to have a new screw fabricated in Holland by long-standing partner company, Landustrie. Made in mild steel, a high-performance, corrosion resistant coating will give it a working life measured in decades.
“We have incorporated some important innovations,” says Jake, “including a stainless steel lower bearing, again made by Landustrie. This does not need an oil or grease feed, so is both ecologically sound and reduces the maintenance requirements – features that will pay dividends in the long run.”
The design team has evaluated the loading on the pump when it is in use and optimised all the new parts to lengthen the pump’s working life and maximise its efficiency and reliability.
Jamie Wesley, Operations Director at ECS states, “To be involved with machines of this size showcases the excellent capabilities available here at ECS, our screw pump experts have given the existing motor, gearbox and upper bearing a clean bill of health, which has helped to reduce the overall cost of the project for Wessex Water.”
New pump bearings save €28,970 per annum at energy plant
Faced with frequent failures on its centrifugal pumps for water recirculation, a large CHP (combined heat and power) plant in Romania asked NSK and its local distributor to perform an on-site pump bearings investigation. The outcome identified poor lubrication of the pump bearings as the source of the failures, with NSK recommending the adoption of sealed-for-life bearings featuring DDU seals and high-temperature grease. In total, the move has led to annual cost savings of €28,970, while simultaneously offering a significant improvement in performance.
Dreamstime Prior to switching to the NSK solution, the CHP plant was suffering bearing failures on its centrifugal pumps every three months. Analysis by NSK showed that oil was leaking from the bearings as a result of poor seal condition. With 30 pumps on site, the facility was spending a significant amount on replacement bearings, oil replenishment and maintenance. When adding the cost of downtime, it became clear that a new strategy was required.
The CHP plant asked NSK´s local distributor to assess the potential for improving the lifetime of the bearings. Considering the age of the equipment and the poor condition of the seals, a design modification to avoid the oil leaks was not considered. Instead, a trial using NSK DDU Sealed Deep Groove Ball Bearings filled with high-temperature grease was performed on three pumps. With no failures occurring after six months of operation, the decision was taken to adopt the NSK solution on all pumps. Following 12 months in service, zero failures have been recorded.
NSK´s DDU Sealed Deep Groove Ball Bearings feature high-quality, ultra-clean steel that is known to extend bearing life by up to 80%. Super-finished raceways are specially honed to minimise noise and improve lubricant distribution and life, while patented seals provide resistance to contamination in the toughest environments. Another advantage of this type of bearing is the pressed steel cage, where close-coined cage pockets and tightly controlled clearances reduce friction and ensure even distribution of the lubricant. The grease offers high temperature resistance and speed capability, with good resistance to water and contamination.
Ultimately, it is the elimination of downtime, maintenance and oil replenishment costs, as well as lower bearing costs, which have led to the calculated annual cost savings at the CHP plant.
Mark Water Pumps leads the way on the aftermarket
While virtually all automotive components are modelled using CAD, computer testing can only take you so far. To really gauge how suitable a component is for a vehicle, physical endurance testing is the only sure-fire way to prove a component or assembly can function properly in the real world. This is why businesses such as Mark Water Pumps Limited (MWPL) operate in-house automotive testing facilities, offering the aftermarket industry an opportunity to independently prove component performance.
MWPL has invested in its Automotive Testing Centre in Colwyn Bay, Wales, to help prove the performance of external products, as well as its own range of OEM equivalent PROFLOW water pumps. The dedicated testing centre has the capability to test water pumps, expansion tanks, thermostats, cooling systems, clutches, clutch bearings, brakes, oil pumps, timing belts, wheel bearings and belt tensioners as well as a host of associated components. Endurance and destruction testing is equally available, ensuring that customers have the means to prove quality, operational suitability and performance of products.
Such a breadth of testing facilities can be invaluable when introducing a new product to the aftermarket. While a product or component may pass computer simulations, nobody really knows how a component will perform until it is subjected to real-world operating conditions. It’s a vital part of product development, ensuring that when a new component is released to market, the risk of recalls or premature component failure is effectively minimised.
Conversely, physical testing is another important part of failure analysis. Being able to accurately replicate failure conditions for a component can provide manufacturers with greater data when carrying out fault analysis. Again, it can serve to identify design or operational limitations to allow further development of the component or product in question.
Either way, a customer can gain from greater quality assurance, as David Lewis, Plant Manager at MWPL explains: “When you buy an OEM component, you can be sure that the manufacturer has carried out physical endurance testing before it was released to market as part of the original vehicle. However, in the aftermarket this is not always the case, as manufacturing and testing standards can vary. In this case, importers and distributors can also ensure the replacement component they are buying meets the standard of components they are expecting”
“Utilising independent testing facilities such as the Mark Automotive Testing Centre means you can get this all-important assurance. It should be at the forefront of product development activity for aftermarket manufacturers and distributors, and this is something consumers in the aftermarket should be looking out for.”
Glasgow’s new screw pumps secure long-term sewage treatment
ECS Engineering Services has recently commenced works as part of the latest phase of Scottish Water’s £250m city-wide programme to improve sewage management in the Glasgow area. Over the next eight months ECS, in association with Landustrie, will be installing and commissioning 14 new screw pumps at the Shieldhall water treatment works, which serves most of the centre of the city.
Shieldhall is the largest of the Glasgow area’s waste water treatment works and serves a population of about 600,000 in the south of Glasgow, Newton Mearns and Renfrew areas.
The Shieldhall site has been modernised several times over the years to meet the growing demand of an ever-expanding population in Scotland’s largest city. As part of the current programme it was realised that the 14 large Archimedes screw pumps that drive the process were getting towards the end of their service lives and needed replacing.
There are four low level and six high level screw pumps, each weighing 13 tonnes, being 16m long and 2.4m in diameter and capable of pumping 960 litres/sec. There are also four larger RAS (return activated sludge) pumps, each 16m by 2.6m with a flow capacity of 1580 litres/sec.
The recent contract award was to provide like-for-like pump replacements, but ECS realised that this would have meant service engineers working in the original concrete troughs, hand screeding the screw pumps for several weeks to create the formed pumping troughs. This process exposes the engineers to unnecessary risks, so in conjunction with Landustrie in the Netherlands the design team looked closely at the design of the equipment to eliminate as much of this as possible, whilst ensuring the client still received the best standard of equipment currently available on the market.
In conjunction with ESD, Scottish Water’s supply partner, several design upgrades were made, the most significant being the alleviation of the requirement to hand screed the new machines into the concrete trough. The pumps were assembled in the factory complete with the new steel coated troughs, these can be moved into position relatively easily, without the fitters having to work in confined and potentially dangerous spaces. Upon successful installation of the new pump and troughs the whole machine will be backfilled with concrete giving both strength and durability far better than the original installations for many years to come. This design upgrade was a major health and safety gain that both Scottish Water, its main contractor ESD and ECS were keen to embrace.
Scottish Water specifications stated that a v-belt drive system should be used, with a direct-on-line drive configuration. This simple but efficient arrangement is appropriate because the slowly rotating pumps run continuously so there are no regular start-up impulses or shock loadings. To compliment this further, ECS has installed new high efficiency motors, which over the course of their long working life will save a considerable amount of energy.
ECS has also delivered further long-term savings thanks to the installation of Landustrie stainless steel ECO, sealed-for-life bottom bearings that are maintenance free for the lifetime of the bearing. Together, the complete installation will provide long-term reliability and efficiency for the treatment works for many years to come.
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