Case study: shipshape revamp for Grimsby pumping station

Grimsby’s Freshney pumping station is a key element of the town’s flood defences.

When the pumping station was first built more than half a century ago it was equipped with three large Archimedes screw pumps. These were replaced some years later, but time and exposure to the elements resulted in corrosion and wear.

So, in 2016, a major refurbishment programme was implemented in respect of the No.3 pump.

Over the years, the pumping station had been called into action on several occasions, but it had been more than five decades since all three screws were operated simultaneously to prevent flooding.

It’s a pretty impressive piece of kit when it is running. It is simple to use and runs the same as a ship’s propeller

Grimsby dockmaster Phil Christy

Almost a decade had passed since the last time that two of the screws had run simultaneously, indicating that should circumstances arise the station had adequate capacity to cope.

In the words of Grimsby dockmaster Phil Christy: “It’s a pretty impressive piece of kit when it is running. It is simple to use and runs the same as a ship’s propeller.”

Each of the three screws weighs seven tonnes and the station has the pumping capacity to shift 6,000 lt/sec.

Like all pumps, wear and tear eventually takes its toll, and in the case of the No.3 pump, AxFlow’s Huddersfield service base was contracted to undertake extensive and essential remedial work.

Closer look

Although the condition of the pump could be seen before removal of the screw itself, extensive examination undertaken once the pump was removed from service revealed serious corrosion of the deflector plates and all the cover grids were completely rotten. Plus some fairly major work was required to replace two of the gears within the gearbox.

“The extent of our tender for the No.3 pump included removing the screw, the cover grids, deflector plates, top and bottom bearings, motor and hand railing”, says Mark Redgrove, AxFlow’s technical support manager.

“The screw was shot-blasted and coated with a polyurethane coating to a thickness of 2mm to provide the 10-year life requested by the customer. The deflector plates, cover grids and handrails were all badly corroded and replaced with new items in galvanised 3mm steel plate.”

AxFlow also took the opportunity to make repairs to the No.2 pump. In this case, repairs were made to the bottom bearing which had failed prematurely after just three years of service.

Given the size of the seven tonne screw, at 5m long and 3m in diameter, it was necessary to bring in a 100 tonne crane with a reach from crane to lift of 20m for the removal and re-installation tasks

Mark Redgrove, technical support manager, AxFlow

Fortunately this job did not involve having to remove the entire pump and was completed before the No.3 pump was re-installed.

All the work was undertaken at AxFlow’s Huddersfield service base where there are specialised pump repair facilities capable of taking pumps up to 50 tonnes in weight.

However, the job of removing and re-installing the No.3 pump screw required the company to draw on its logistics capabilities.

“Given the size of the seven tonne screw, at 5m long and 3m in diameter, it was necessary to bring in a 100 tonne crane with a reach from crane to lift of 20m for the removal and re-installation tasks,” says Redgrove.

“We also had to bring in a diving team and smaller 50 tonne crane for installing the dam board, which performs the same job as stop logs in allowing the bottom bearing area to be pumped out.”

The various engineering jobs undertaken by AxFlow were part of a rolling programme of refurbishment to the pumping station.