Most tender specifications for local raw sewage pumpstations tend not to be sufficient to cope with the harsh conditions in which they have to operate. Therefore, local pumps designer and manufacturer Fluid Pumps has developed the VX range of submersible pumps.

“South Africa’s wastewater treatment standards are Third World. Very little, if any, attention is given to what is flushed down a cistern,” says Fluid Pumps technical manager Blackie Swart.

He adds that most imported raw sewage pumping equipment from Europe is designed to meet much stricter standards than those in South Africa, and are, therefore, not suited to local conditions.

Swart tells Engineering News that no channel impeller – whether it be single-, two- or three-vane, or screw impeller – functions as it should in local sewage conditions, resulting in clogged-up pumps and sewage spill into the water systems.

In response to these challenges, the VX submersible pumps can handle raw, unscreened sewage, which often contains foreign items, including rags, plastic and sand, without clogging.

“Having the submersible pump installed on the sump floor rids the pumpstation of all these foreign objects. This is unlike self-priming pumps that have a channel impeller fitted with a suction liner, which forms a closed impeller that pumps mid-water, leaving crust build-up at the top, and settled sand and sludge on the sump floor,” Swart explains.

To handle South African wastewater conditions, the VX pumps are fitted with an open vortex impeller and have a solid through-let with a diameter of 80 mm to 200 mm.

“The most important part of a submersible pump is the mechanical shaft seal. Therefore, Fluid Pumps designed and patented the Quatro mechanical shaft seal,” he says.

The Quatro mechanical shaft seal is oil-submerged in an oil chamber for lubrication and cooling purposes. This allows for limited dry running without damage to the seal. No stringy materials can build up around the seal, which causes failure.

A replaceable back cover is in place for easy access to the Quatro mechanical shaft seal.

“This is a cost saver, as it protects the bearing or oil housing, which wear down, from pumped products. A large angular contact bearing and large shaft diameter prolong the service life of the pump,” Swart notes.

These design features, along with explosionproof spigots and tolerances, ensure a submersible pump that can withstand harsh wastewater conditions.

The VX range is supported by a fully equipped Fluid Pumps workshop and testing facility, in Boksburg, with all parts being available off the shelf.