Southern African Pump Systems Devel-opment Association (Sapsda) chairperson Mathys Wehmeyer advises the mining industry and other users of submerged pumps to take into account the actual cost incurred when buying these pumps.

“When buying a submersible pump, like any other piece of capital equipment, the main consideration should be the total cost of ownership, the total cost of power usage, maintenance, as well as the cost involved in the loss of use, and not just the purchase price of the pump,” he explains.

Wehmeyer highlights that this is especially important for the mining industry, where one-day work stoppages, owing to equipment maintenance, means a loss in production and profits.

A restructured version of the South African Pump Manufacturers Association, Sapsda was founded in 2008 with the aim of developing a strong pumps industry in all Southern African countries. The association offers training courses to member companies in a number of Southern African countries.

Wehmeyer highlights several factors that influence the life expectancy of a submersible pump and mentions that, if pumps are not maintained properly, it results in unnecessary costs that could otherwise have been avoided.

One of the factors is the importance of knowing the composition of the liquid that needs to be pumped. Wehmeyer says it is important to establish if there are any solids present in the liquid, explaining that this will help the user to determine the chemical composition of what needs to be pumped, as well as which type of pump will be appropriate for the application.

“The major cause of submersible pump failure is the overheating of the electrical windings. It is essential that the heat is dissipated away from the electrical windings. Most submersible pumps rely on the product being pumped to dissipate the heat from the windings and mechanical seals and, when the pumps run dry, it will build heat and the electrical winding, as well as the seals, will fail,” elaborates Wehmeyer.

He further advises that, to improve the heat dissipation, the motor housing must be filled with oil, which will effectively dissipate the heat away from the electrical windings and seals, even if the pump runs dry. This will ensure that the electrical windings do not overheat and burn out.

Wehmeyer highlights that damage to the electrical cables also frequently occurs. He says it is essential that the pump is fitted with a good-quality trailing cable with screened conductors.

He concludes that all electrical submersible pumps require an electrical control panel that has been specifically designed to protect the pump, should the pump be overloaded.