An ABB low voltage AC drive has cut pump maintenance costs for a local authority by €1,000 a week.
The water services department of Laois County Council in the Republic of Ireland had problems with the sewage pump at its Connolly Street Pumping Station in Mountmellick, a town of around 5,000 residents. The foul sewer submersible pump is housed in a building at a road junction in the town and is six metres below the surface level. The location is the second largest of eight pumping stations in the area.
The pump was prone to ragging, which is caused when rags foul the pump inlet and prevent the pump from operating normally. The pump therefore needed to be lifted and cleared three to four times a week. As the gradient of the sewer is very shallow, extra debris would accumulate in very wet weather, resulting in the pump having to be raised even more often, up to four or five times a week. Each lift cost €270 and took around six man hours to complete. It also meant that the town was relying on one standby pump while the main pump was being cleaned.
Laois County Council contacted ACS Drives and Control Systems, an ABB Drives Alliance member, for a solution. Larry Gittens is Sanitary Services Supervisor for Laois County Council’s water services department: “We had met ACS at an ABB drives and motors road show and thought that the solutions they provide could help us with the problem at Connolly Road.”
ACS’s Seamus Butler installed a 15 kW ABB industrial drive for water and wastewater. This comes with a series of intelligent pump functions, one of which is an anti-jam module.
The anti-jam function enables the drive to perform preventive maintenance on the pump. When the function is triggered, the pump is run at high speed and either reversed or stopped in a number of user-defined cleaning cycles. This helps to prevent congestion through the build-up of particles, as well as avoiding rusting in “sleeping” pumps.
The ABB drive was installed for a two month trial, during which no blockages were experienced and there was no reduction in flow. Following this, a permanent installation has been in place for four months and the water services department has not had to lift the pump once.
With a purchase cost of €2,500 and an average saving of €1,000 a week, the payback time is two and a half weeks, giving Laois County Council an excellent return on investment.
