Modern overhaul to historic site aids environment and efficiency

Islington Pumping Station is a historic pumping station located in Kings Lynn, Norfolk. Owned and operated by Kings Lynn Internal Drainage Board. it pumps water from the IDB’s drain to the tidal salt marshes of The Wash. 

The pumping station provides protection to almost 6000 hectares, making it the largest single catchment within the Board’s district.  The catchment is largely fenland so consequently water is drawn to the station through the action of the pumps rather than gravity fed.

Pumping up the volume

The existing pumping station at Islington was constructed in 1959 and operated with three diesel engine powered pumps rated at 2,800 l/s each.  Work on a new station began last year and will run till March 2021, providing a total pumping capacity of 16,000 l/s and designed around four concrete casing pumps; running at full capacity the pumping station would be capable of pumping 1.4 billion litres of water per day.

The pump casing is of a concrete cast construction and is designed to operate with a formed suction intake specifically designed by Bedford Pumps Ltd.  The vast suction intake was scale model tested and optimised at Hydrotec Consultants Ltd.’s laboratory, operating at a total station capacity of 20,000 litres per second, thus proving the infrastructure future proof. The results were uniform flow patterns at the impeller inlet. free from pre-swirl, entrained air and surface and submerged vortices. The model test showed that the intake design allowed for incredibly low minimum operating water levels.

The Bedford Pumps intake design offers significant advantages over a standard ANSI ‘type 10’ intake such as a significant reduction in the overall footprint and allowing the water levels to be drawn down to half the minimum submergence when compared to the type 10 design. 

At full capacity the pumping station would be capable of pumping 1.4 billion litres of water per day

The unique combined design of the pumps and the intake provides a very low footprint and will significantly reduce the excavation costs on site by allowing the pipework to be much closer to the surface. The formed suction intake will be constructed on site using very precise 3D printed polyform formers, allowing the civils contractor to accurately create the concrete intake.

Nature watched

The four pumpsets also fulfil the requirement for Islington P.S. to be ‘Fish Friendly’.  Although ill-defined, the term ‘Fish Friendly’ implies a machine which avoids or minimises damage to aquatic fauna.  In order for fish (and migratory eels) to pass through any form of rotodynamic pump, it is recognised that conventional pump designs require substantial modification and the range and extent to which a pump can be utilised is in fact relatively narrow.

To achieve a Fish-Friendly status, the essential elements for pumps include relatively low impeller peripheral speed, high hydraulic efficiency, substantially Increased spatial clearances between the impeller and guide-vane casing and avoidance of internal areas which might trap debris are to be avoided.

As part of the wider scope of the specific application, the designs have been optimised to have a wide band of stable operation,  while inflow to the station and intake positioning should minimise head-loss and invoke gradual transition into the pump inlet without adverse pre-swirl, uneven velocity distribution or air entrainment, all of which could result in obstacles to safe passage.

Pipework and outlet designs were also considered to optimise velocity and trajectory,while pump start and stop sequences to be evaluated and parameters adjustable to suit site and seasonal particulars.