Prior to the release of the new S-tube, Grundfos approached a water company in the north of England with a view to involving them in the development and testing of this new impeller technology. A combined sewage and storm-water pumping station was selected that had a history of pump blockages. The pre-trial pumps were tripping on a regular basis due to excessive ragging

The pumps were controlled from a brick control house in front of the pump well, however there was no automatic duty pump rotation, so the duty pump ran until it tripped or failed, at which time the standby pump will become the duty pump.

Field trial

The S-tube impeller started its field trial in 2010. During the whole pre-trial, trial and post-trial period, Grundfos worked closely with the client to develop and optimise the S-tube impeller design based on operator feedback during the test period, helping to perfect the hydraulic performance.

After a year of trouble-free operation, the trial pump was lifted and the pump was then closely examined to see what suggestions for improvements could be gleaned from it. This feedback contributed to revising the impeller design and the pump.

The operators at the water company were very satisfied with the outcome, and the pump was left in situ after the test period was over and continues to perform well.