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Dewatering pump maintenance: Keep moving

Maintaining your dewatering pumps goes a long way, writes Joe Moser, pump product manager, Atlas Copco Construction Equipment

Submersible dewatering pumps have one clear goal – to move water, whether it’s to another location for reuse or to simply remove water from a low-lying area. For the most part they require minimal maintenance.

But before you set and forget your submersible dewatering pumps, there are some preventative maintenance practices you should follow to keep them operating day in and day out, so that productivity keeps flowing in the right direction. And some of the most important practices start long before your submersible pumps hit the job site.

A pump that sizes up

Electric submersible pumps are the most commonly used pumps for dewatering construction sites because they are small and lightweight. When it comes to maintaining pumps, choosing the right one for the application is one of the most important decisions you’ll make. Using a pump that isn’t sized appropriately for an application can lead to problems later on, such as a broken shaft, dislodged seal or thrown impeller, any of which will result in costly downtime.

To avoid this, there are three things to consider: the material you are pumping; how far you need to pump it; and the elevation to which it will be pumped. If the pump will be moving materials such as sand, gravel or clay, rather than just water, you’ll need a model that is rated for that application and is equipped with impellers made of a durable material, for example cast iron. Other materials, such as polyurethane, can handle water, but abrasive materials can cause them to wear out quickly. Electric submersible pumps rated for these applications can typically move materials as large as 25mm in diameter with minimal wear to components.

From there you will want to confirm the pump can move water as far as you need it to go. Generally, the farther the pump is from the water site, the more power it will need to move the water to or from that location. And if the water has to travel uphill, the pump also will need more head capacity – in other words, how high the pump can raise water. Electric submersible pumps operate with as much as 5,300 gallons/min and can pump water as high as 85m. Outputs can be as wide as 250mm in diameter for even greater flow capacities. 

Get immersed in the details

Once you’ve determined the right size, make sure the pump is built from durable materials and has features that will withstand long runtimes and the harsh conditions of construction applications. The pump’s wear plates and seals play an important role in this because they help to protect the internal components. Choose pumps with double mechanical seals, which provide a consistent, watertight interface. Some manufacturers offer stainless steel seals, which are more durable than rubber seals. Also look for mechanisms that stop the unit if it overheats or the electric current overloads the pump. On most models the pump will automatically restart after it has cooled. This helps to protect the motor from damage and extends the life of the pump.

If your pump will be unattended, consider installing a float that automatically shuts off the pump when the water level becomes too low, then restarts it as the level rises. This avoids damage to the seal and premature motor failure.

In addition to pump components that prevent damage from occurring, there are others that make maintenance faster and easier on site. For example, the interior of some pumps can be easily accessed with the removal of just three bolts.

Some pumps also don’t require users to remove additional components, such as the seal, to access the interior. For even faster maintenance on site, many manufacturers offer a complete replacement package that includes a seal, shaft and impeller and everything users need to install them. Also consider where you can get parts and how long you might have to wait for them.

Now you’re ready to get things moving. But once you have your pump in place, don’t forget to pay it a visit once in a while.

A little goes a long way

While every piece of equipment with moving parts needs regular, preventative maintenance, this is particularly important for equipment used in rugged applications such as dewatering construction sites.

Electric submersible pumps have three main wear parts: the impeller, seal and shaft. A drop of preventative maintenance goes a long way with all of them.

The seal is one of the most critical parts of a pump so it’s important to check the seal oil as often as once a week in heavy-use applications and to refill it as needed. This will ensure the seal remains properly lubricated and watertight.

Inspecting hoses and cables for damage should be on your weekly checklist too, especially if they are exposed to the elements or in areas where traffic could cause damage. Typically a damaged pump hose is easy to spot because you’ll see water flowing from it. A damaged cord, on the other hand, might not be as noticeable, and could pose a danger to personnel or short the motor.

If your pumps will be in use for extended periods, it is advisable to take them out of service every four months or so to inspect thoroughly internal components such as the impeller and shaft. Damage to these areas can allow water to leak into the pump and harm its components. This also is a good time to change the seal oil, which can become thick and gummy over time and cause the pump to burn out. Don’t forget to shut down the power supply before performing any maintenance to eliminate the risk of injuries.

Finally, have a back-up pump on hand to keep water flowing if your pump needs maintenance or when you take it out of service.

Go with the flow

The longevity and performance of your pump trickle down from the preventative maintenance practices you perform. From the time you purchase a pump to the last day it is on site, a clear preventative maintenance plan will keep water moving and productivity flowing in the right direction. 

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