Case
Grundfos SE helps municipal water utility reduce vibrations and increase agility
Testing Grundfos SE to the limit
As part of the launch of new products, Grundfos carries out field tests to verify that pumps live up to the expectations and perform as promised outside of the controlled testing facilities.
In the summer of 2023, such a field test was initiated at Aalborg Forsyning, a municipal water utility in Denmark, to test the limits of the new Grundfos SE Range 56 wastewater pumps.
“Aalborg Forsyning is an interesting installation for us, because the wastewater in their network contains high levels of sand. Overall, I would consider the wastewater conditions at Aalborg Forsyning quite challenging and thereby perfect to really test the limits of our new product,” explains Silvia Sáenz Gómez, Market Development Manager Municipal WU – Europe, Grundfos.
In addition to sand in the installation, Aalborg Forsyning deals with challenging seasonal changes in demand which can vary from a base flow of 300 m3/h during the dry season to upwards of 1,000 m3/h during the wet season.
“Because of the challenges Aalborg Forsyning faces on a daily basis, it was the perfect installation to test the Grundfos SE with a cast iron Open S-tube® impeller. The cast iron impeller is the standard impeller, and in sandy installations we would usually recommend opting for a more wear-resistant material. However, in this field test, we wanted to test the pump to its limits, and while we know that the pump and impeller perform extremely well with fibres, we were eager to see how they would perform in these challenging conditions. The results will give us valuable insights to base future recommendations for spare parts and customisations as well as estimates of component lifetimes on,” Sáenz Gómez explains.
The 37 kW Grundfos SE is operated by a controller based on water levels in the inflow station. The test will be running for a year while Grundfos and Aalborg Forsyning collect data about its performance, energy consumption and signs of wear and tear.
For us, this was a great way to test what a Grundfos pump has to offer in an installation like ours. We are always looking for the most robust and reliable solutions on the market because that is the alpha and omega in our field of business.
“We already knew and trusted Grundfos because they carry out service jobs at our facility, so we agreed to participate in this field test and removed one of our existing pumps. Grundfos replaced it with a new SE pump using the same controls and the same installation as before, the only adjustment needed was a piece of pipe that had to be fitted for the new pump,” Sejdijevic explains.
A small pump with a large potential
For Aalborg Forsyning, the experience has been positive from start to finish:
“We were very eager to see if there are other submersible pumps out there able to handle the conditions in our wastewater network, and the Grundfos SE definitely is able to do that. I don’t have to give the pump much thought on a daily basis – it just works,” Sejdijevic says.
For Aalborg Forsyning, the main benefits of Grundfos SE are its adaptability, its reliability and its low vibration level.
“Our old pump had been running for 13 years without mentionable issues, but what we found interesting about the Grundfos SE is that we are able to lower its speed duringtimes of low demand and similarly raise the speed during peak demand. This is a capability we usually only see in multi-stage pumps, so the fact that the single-stage pump can do it, and do it so well, is pretty unique,” Sejdijevic explains end elaborates: “We are used to pumps vibrating quite significantly when operating at very high or very low speed, but this pump is very stable at all speeds, which is a significant benefit.”
For Grundfos, the test has been a success as well:
“We are very happy with the way the pump has performed in this field test so far. Despite the challenging conditions, it has been operating efficiently and reliably for five months now. We have seen a loss in efficiency from 570 m3/h at 43 Hz to to 430 m3/h at 43 Hz, and while that does indicate wear on the impeller, it is important to note that this is the standard impeller, which we wouldn’t normally recommend in a sandy installation. But the fact that it has withstood such challenging conditions that well bodes very well for its capabilities in less challenging installations,” Sáenz Gómez explains and continues:
“The Grundfos SE comes with a SmartTrim feature that allows us to restore the gap between the impeller and suction cover to its factory setting to regain maximum efficiency which has not been done at Aalborg Forsyning. All it takes is a 10-15 minute trim of the impeller that doesn't require dismantling the pump or installation. I would expect that we can restore factory efficiency in this pump 2-3 times before having to replace the impeller, so it still has a long life ahead.”
Looking ahead, Aalborg Forsyning sees a distinct potential in the enhanced capabilities that the Grundfos SE introduces to their pumping station:
“Once the field test is over, it is very possible that we will replace the impeller with one in a more suitable material and continue to use the pump, because it is a great benefit for us that this pump is able to alternate between operating as a large and a small pump, respectively, without causing excessive vibration. And we expect it to have a long product life which is of course a benefit too.”