SELECTING the right dewatering pump means being clear on what duty it is expected to perform, explains Justin Bawden, internal sales consultant at Integrated Pump Technology – SADC distributor of Grindex Pumps.
“Users need to ask a number of important questions when selecting a dewatering pump,” says Bawden. “This starts with the flow and pressure (head) requirements – which can be measured in litres per second or cubic metres per hour.”
Then the total dynamic head must be calculated. This is a function of the static head, which refers to the metres of vertical elevation, and the friction losses in the hose. To work out these friction losses, the user must estimate the ‘run length’ to the discharge point. The diameter of the hose, and its material of construction, must also be considered.
“The pump’s kilowatt rating and impeller type can then be suited to the flow rate and the total dynamic head on the pipeline discharge point,” he says.
Another key consideration is the size, percentage and specific gravity of the solids in the liquid to be pumped.
This will affect the design of the impeller required, as well as the material of construction for the pump or wear parts. Abrasive material, for instance, will demand that the pump’s wear parts are made with suitably abrasion-resistant metals or compounds.
“Users must consider the acidity of the liquid, as this will cause corrosion if the wear parts are not constructed or coated with the right material,” he warns. The dimensions of the sump should then be examined – in terms of its depth and the size of its opening.
The site itself may present challenges, including the type and quality of power available.
Bawden advises users – especially contractors moving onto a new site – to check the voltage and phase of the power being supplied. He urges pump users to get expert advice in confirming their choice of pumps.