4 minute read
Energy Efficiency: Pump and motor overhaul pays off
Following the renewal of the lock gates at Sluis Zemst in the Brussels-Scheldt Sea Canal, two pump installations were recently replaced. Accounting for a total flow rate of 18,000m 3 /hr, a 5% improvement in efficiency was achieved by clever coordination of the pumps with the motors. The custom-made pumps and motors were developed by pump supplier KSB and motor specialist WEG, as the companies explained to flow.
The Brussels-Scheldt Sea Canal, popularly known as the Willebroek Canal, is one of the oldest canals in Europe. Today, it remains of great economic importance to Belgium. The airport of Zaventem is entirely dependent on a good throughput of the route for kerosene. Four locks manage the 14m drop in level along the route. The canal also plays a significant role in supplying Brussels itself, and in maintaining the water level of the local area.
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To guarantee the reliability of this important artery, the Zemst lock needed an overhaul. The lock gates were replaced, followed by pump installations to maintain the water level of the upper part of the lock.
Jan van Laer, Senior Expert Water & Waste Water at KSB, explained how the decision to install completely new pumps had both technical and practical reasons: “Sluis Zemst had a total of five Ensival AGV15 pumps installed in the 1970s, which were no longer achieving their specified flow rate of 9600m 3 /hr. Three of the five pumps were in use and two in reserve, so that they could be switched on if necessary. But of course, you need to be able to rely on them all to perform so good maintenance is essential. However, Vlaamse Waterwerg NV, the manager of the lock complex, faced a challenge. Firstly, some spare parts had to be rebuilt; secondly, every maintenance request had to be put out to tender. So each time you had to deal with different parties. What’s more, when requests are put out to tender, the best technical solution does not always win, so the pumps sometimes ended up with poorer performance than they went in with.”
NEW PUMPS
Vlaamse Waterweg NV, therefore, decided to replace the pumps. This was also a tender, which was won by the engineering firm Agidens. Based on past experience, Agidens called in KSB as supplier of the pumps. They, in turn, chose WEG as their motor supplier.
Jan continued: “For our proposal, we compared various motors based on price, quality and efficiency. WEG came out on top here. Moreover, we know WEG and their motors well from other projects.”
When asked about the pump characteristics that convinced Agidens to work with KSB, Jan initially mentioned their high efficiency. “Because in this application the pump only has one operating area – the fluctuations in water level are negligible – we could count on a fixed flow of 9000m 3 /hr and a fixed delivery head of 10m. We were then able to optimise the design for this. In this case, this resulted in an SEZ 1500 centrifugal pump with a semi-axial impeller with optimised blade angle, with high hydraulic efficiency of 85.1%. And because a relatively low speed of 500rpm is sufficient for these values, we were able to work with a 6kV medium-voltage motor.
“This motor, specially built by WEG for this application, brings the total efficiency of the entire pumping installation to 82%. This is an improvement of at least 5% on the previous setup. With this proven efficiency improvement you can save a lot of energy: each motor has a power of 670kW, so during the life of the pump – about 50 years – that’s a big advantage.”
James Jonckers, Sales Manager at WEG Benelux, explained the role the motors played in the overall efficiency figures: “Although in the past we have mainly produced low-voltage motors, in recent years we have also successfully focused on the medium and high-voltage segment. We now supply motors up to 15mW. The expertise we have built up in this area is bearing fruit: at full load, the HGF630 motors used for Sluis Zemst have an efficiency of 96.2%, with a power factor of 0.8. This last figure was also an important requirement because too low a value can result in penalties for the user for the reactive power supplied”.
The motors’ bearings were also unusual in this project. Because of the vertical arrangement of the motors, they are lubricated with grease instead of oil. The torque is 12900Nm at the specified low speed of 500rpm, which has a positive impact on the life of the engine.
Both KSB and WEG are currently working on the construction of a third pump and motor to replace another of the old pump installations. Whether this will be followed by pumps four and five is not yet certain: in principle, with the three new pumps, there is more than enough reliable capacity available to maintain the water level. Moreover, if the level during planned maintenance is too low, the old pumps could also temporarily assist. Add to this the fact that the maintenance for the first five years does not have to be put out to tender but is done by KSB Service Belgium, and the future of the Zemst Sluis and a smooth flow of the Brussels-ScheldtSea Canal seems to be secured.
This future-proofing also applies to the cooperation between KSB and WEG as James explained: “Like us, KSB likes to sit around the table with partners at an early stage to fully identify the customer’s needs and to make the best possible offer. If you can understand each other during the early planning stage, it underpins smooth collaboration on future projects.”
