How to reduce sediment in your dewatering system?

Pumped liquids in mines and tunnel construction sites often contain solids of varying degrees which can cause wear on the pump, valves and associated dewatering equipment. Chris Molloy, Pump Manager at Fitt Resources explains the two main ways of reducing sedimentation damage on your equipment.

According to Mr Molloy, gravel, mud and sand are the main solids present in dewatering applications. When pumping water with these solids present, there is a risk of sedimentation ending up in the system.

“A typical symptom of a build-up in sedimentation is the pipe and hose becoming partially blocked. This results in capacity losses of the pump and an overall inefficient system.

“As the amount of solid matter passing through the system increases, so too does the wear on the pump. Overtime, and if not properly managed, this can lead to opening up of critical clearances which can cause reticulation and premature pump failure.”

Sedimentation tank

A sedimentation tank is a good option when it comes to reducing the risk of solids entering your dewatering system.

According to Mr Molloy, a simple steel tank with a dividing plate can be used.

“This set up allows solids to settle on one side prior to the liquid progressing to the pump side of the tank.

“Tanks can also be custom designed to suit spacing requirements, especially in narrow tunnels and restricted areas in mines. The location of the tank is also flexible depending on the system and pumps being used.

“A tank with a large surface area will increase the system’s effectiveness as there is reduced agitation of the liquid as it is absorbed across the area.  Turbulence is therefore also reduced, allowing sediment to settle more easily.

“The more solid matter present in the water, the more careful the design of the sedimentation system required to create a suitable ratio of water to sediment,” says Mr Molloy.

How FITT can help

FITT Resources’ sound knowledge base and industry experience means that we can help clients construct correct sedimentation tanks to reduce wear and associated life cycle costs of the pump.

“Depending on your site’s requirements, FITT can help you design the very best solution to ensure that your pump system is well placed for a long life of effective mine or tunnel dewatering.

“As we are the sole distributor of Grindex Pumps in Australia, FITT Resources can offer fast turnaround times with full testing capabilities, while also having the ability to provide high quality reports and recommendations to each of our clients.

“Grindex pumps also have a 2 year dry burn-out guarantee with the unique ability to run dry without experiencing pump failure.  They can withstand very abrasive and harsh environments so are a fantastic choice when it comes to dewatering in harsh mine or tunnel construction sites.”

Velocity changes

For applications where solids cannot be avoided, such as those involving sand and gravel,  there are recommendations for the velocity of the medium in the discharge line:

Mixture		Min. velocity in discharge line
1.	Water + coarse gravel	4 m/s (13.1 ft/s)
2.	Water + gravel	3 m/s (11.5 ft/s)
3.	Water + sand:
	Sand particles < 0.1mm (0.004 in)	1.5 m/s (8.2 ft/s)
	Sand particles < 0.6mm (0.024 in)	2.5 m/s (4.9 ft/s)

“By altering the velocity of the pump, solids pass through the system with a reduced impact on the interior of the pump,” says Mr Molloy.

“Naturally, this reduces wear on the inside of the pump and extends the overall lifespan of the equipment.”

The Grindex advantage in reducing sedimentation

The Grindex range has the unique advantage of pump cooling jackets allowing them to operate at low levels without the motor overheating. This enables full use of the sedimentation tank due to minimal disruption of the water.

This, coupled with FITT Resources’ expertise, equates to a quality solution that will help keep your pump pumping no matter the harsh environment.

Contact Chris Molloy on 0404 483 998 to find out more about the Grindex range of dewatering, sludge and slurry equipment.