Submersible pump that can run dry a safer option

15th September 2017 By: Victor Moolman - Creamer Media Writer

Submersible pump that can run dry a safer option

LARGE PLAYER Hazleton has supplied some of the largest submersible pumps in the world

The Hippo submersible pumps range from Centurion-based slurry pumping solutions provider Hazleton Pumps can operate without water for an unlimited amount of time, explains Hazleton Pumps MD Thys Wehmeyer.

Some submersible pumps are designed to use water as a coolant, overheating when they run dry and eventually burning out, resulting in mining companies having to incur costly repairs or buy new equipment, and deal with production losses. The overheating of a pump’s motor winding in a mining situation, says Wehmeyer, can also be a safety issue, where submersible pumps are used to pump slurry in the presence of methane gas.

However, he points out that the motor chambers of the Hippo submersible pumps are filled with oil, which dissipates heat from the electrical motor winding that drives the pump system. This feature ensures that the pumps cannot cause explosions when dangerous gas is present and the water level has dropped significantly.

Wehmeyer explains that submersible pumps are used in mining operations to remove pockets of water – owing to heavy rainfall, underground runoff water or the presence of dykes – that hinder mining operations. “Water needs to be constantly removed to ensure underground mining operations can continue.”

“Water containing solids constitutes a slurry and the specific gravity of the slurry will determine the type of submersible pump specified,” Wehmeyer highlights.

The materials used to manufacture the pumps also depend on user-specific requirements, with specialised duplex stainless steels required when pumping acidic liquids.

“Double mechanical seals fitted with leak detection are used to measure the conductivity of the oil in the motor chamber and the lower seal chamber. If the oil is contaminated, in case of mechanical seal failure, the pump will be automatically switched off to prevent damage to the electrical windings,” he states.

Further, the pump’s motor chamber is fitted with a vacuum pressure detector and, in case of a leak, the loss of vacuum pressure will cause the pump to switch off automatically. Wehmeyer states that no constant monitoring of the Hippo submersible slurry pumps is required when all the safety controls have been installed.

Vibration sensors fitted to the pumps will also detect when the shaft is vibrating, which can be caused by a damaged impeller or the impeller channel being blocked. He states that, when further mechanical problems occur, owing to the shaft being damaged or impeller being jammed, the thermistors on the electrical winding will detect a rise in temperature, causing the pump to switch off.

“The pump can be controlled and restarted remotely from the surface and, in the event of a power failure, this also prevents delays in getting the mine back into operation. During commissioning of the pumps, Hazleton’s technical staff, or a certified representative, will confirm that all the safety controls are properly installed and connected,” Wehmeyer highlights.

The Hippo pumps range’s slurry pumping capacity is limited to the power supply available at the point of installation. “At this stage, the maximum head of the 1 500 kW Hippo high-volume, high-head, medium-/high-voltage submersible slurry pump is 275 m.” These pumps are also flameproof and manufactured to comply with IEC 60097/1: 2005 standards.

As Hazleton Pumps sells pumping systems and not pumps, the price of the Hippo pumps range depends on the pumping system being installed, with all the pumps supplied by Hazleton Pumps built to order, according to the specifications set out by the company’s clients.

The Hippo pumps range does not require regular maintenance on the same level as other submersible pumps. If a pump does fail, says Wehmeyer, it needs to be removed and sent to Hazleton for evaluation and repair.

“The protection measures installed will indicate the cause of the failure and determine the extent of the repair. Since the cost of rewinding an electrical winding could account for as much as 40% of the price of a new pump, the protective measures taken will shut down the pump, which means that the winding will not burn out,” he adds.

Initial Markets
Wehmeyer explains that Hazleton started by supplying the South African market with a standard range of pumping systems and submersible pumps.

“Only once enquiries were received from international customers did we start to develop and manufacture larger pumps and tailor our pumps to meet specific requirements. The world’s largest vertical spindle froth slurry pump was specially designed, developed and manufactured by Hazleton Pumps for the Apatit phosphate plant, in northern Russia, in 2001.”

He points out that the largest Hippo medium-voltage submersible slurry pump in the world was designed, developed and manufactured by Hazleton Pumps for a platinum mine in South Africa, also in 2001.

Hippo pumps have also been exported to an oil sands operation in Fort McMurray’s, Canada, since 2006, with the company’s success in Canada leading to an order to supply pumps this year to the Koidu kimberlite project, in Sierra Leone, Wehmeyer highlights.