Stormwater project is underground success

www.worldpumps.com

WORLD PUMPS April 2009Applications 17

In December 2008, Northern Ireland

Water’s £100 million Belfast sewers

project reached another landmark stage

with the delivery of six 15 tonne storm

water pumps from Bedford Pumps Ltd, a

manufacturer of large, bespoke water and

wastewater pumps.

The pumps, which are among the largest in

Northern Ireland, are being installed 40 m

below ground level at Duncrue Street at

the base of the project’s terminal pumping

station (TPS).

The station itself lies at the end of the

10 km network of new storm tunnels

currently under construction below Belfast.

The pumps are crucial elements to the

whole project, and when operational, will

work to alleviate storm conditions and

reduce the risk of flooding in the city.

Each pump has the capacity to deliver

around 3,500 l/s, which means that when

all six pumps are installed, together, they

could empty an Olympic sized swimming

pool in less than two minutes. They are

driven by 950 kW, 3.3 kV immersible, flame-

proof motors.

In addition to the six large storm pumps, the

station also includes two smaller FFT pumps

which will be used to discharge the lower

flows to the treatment works. NI Water had

to take the following design consideration

into account when selecting the FFT pumps.

constant flow of 750 l/s over the static

head range of 10 m to 36 m while

remaining hydraulically stable and

operating efficiently.

pipework was greater than 1.8 m/sec to

maintain a self cleansing velocity.

strategic positioning the NRV.

withstanding severe abrasion due to the

high levels of grit present in the pumpage.

protection in the event of flooding.

Brian Henderson, project manager, NI Water

welcomed the arrival of the pumps in Belfast;

"The arrival of these six storm pumps marks

another significant landmark in the project.

We have undoubtedly benefited from the

expertise of the team at Bedford Pumps.”

Ltd, explains how the design specifica-

tion influenced the selection process: “The

arrangement used at this site is a depar-

ture from the norm for deep well pumping

stations in that traditionally the drive motor

is situated at ground floor level thereby

ensuring it is kept dry in the event of a

flood. The pump is then driven via flexible

drive shafting. To support the shafts inter-

mediate plumber type bearings are required

at approximately three metre intervals. These

bearings in turn require support beams and

access for lubrication all of which add to

the cost of the installation and present an

ongoing maintenance requirement.”

Frank adds; “The alternative is to install dry

well submersible pumps. Whilst this over-

comes the drive shaft problem the integ-

rity of the pumpset is dependant on the

performance of the primary mechanical seal

of the pump.

“The solution for NI Water’s Belfast sewers

project was to use a conventional mixed

flow volute pump fitted with a packed

gland. This shaft sealing method is tried

and tested but also economic to maintain.

To protect the motor in the event of a flood

Bedford Pumps manufactured an IP68 flame-

proof machine which was close coupled

to the pump. As a result the arrangement

minimised the overall cost of the installation

whilst ensuring optimum reliability.”

The TPS and tunnel system remain on

schedule to become operational in early

2010.

www.niwater.com

Water & wastewater

Stormwater project is

underground successPart of a massive sewers project in Northern Ireland requires the installation of dry well

submersible pumps below ground. As the integrity of these depends on the performance of the

primary mechanical seal, the solution uses a conventional mixed flow volute pump fitted with a

packed gland.

Pump delivered 40 m below ground Level. Each of the six

15 tonne stormwater Belfast sewers project pumps has

the capacity to deliver around 3,500 l/s.