This Operator Takes Action When Screw Pump Shows Signs Of Failure

Author: Eric Finnila | February 19, 2015 | Category: Equipment Maintenance, Wastewater Treatment

Before_Screw_PumpTiny flakes of metal and paint float to the top of a small screw pump at a wastewater treatment plant in upper Michigan. Over time, the gear box has become louder, the capacity of the pump has reduced, and the bearings need replacing yearly. The operator knows the signs the mid-70s era pump is demonstrating are key indicators of performance and efficiency loss. To protect the municipality’s investment from further degradation, he decides to take action.

Screw pumps are one of the oldest and most dependable modes of fluid transfer. Originally designed by Archimedes to move water uphill in 3rd century B.C., the screw pump works by rotating and taking water in through the bottom of the screw, transferring it from one thread to the next until it exits at the top of the screw.

Archimedes-screw one-screw-threads with-ball 3D-view animated small.gif

Over time, especially in wastewater applications, the metal screw, lower bearing, upper bearing, gear reducer and the trough wear. Chemicals, abrasive materials, and other environmental conditions exacerbate the issue. Clearances open up and the pump is unable to deliver the same efficiency due to slippage and increased friction.

To protect the municipality’s investment from further degradation, the wastewater operator called Crane Engineering in to take a look and make a plan. Further inspection revealed the pump was out of tolerance and demonstrating indicators catastrophic failure.  Rather than replace the entire pump, Crane’s account manager suggested rehabilitating the pump, saving the municipality 50% of the cost of new.  The operator agreed that the decision was clear. Let’s rehab it.

After_Screw_PumpThe screw and its components were removed. It was sent back to the Crane Engineering Service Center.  The screw was sandblasted and recoated with a coating system tougher than it ever had. The Crane Engineering Corrosion Resistance Team mobilized to the site, sandblasted the trough, filled the voids, and installed a liner with a 5 year warranty.

Back at the Crane Engineering Service Center the lower bearing is converted from grease lubrication to oil lubrication. This is done to help the wastewater treatment plant lower electrical cost, and make the pump easier to maintain for the operator. The clearances are returned to the manufacturer’s specifications, the upper bearing and gear reducer are replaced, as well as the motor. 

After just a few short weeks, the screw was ready to go back into commission. Crane Engineering’s Service Team re-installed the screw and placed it back into service. Maintenance practices are simplified and the screw operates better than ever. Restored to like-new condition with a 3 year warranty, the wastewater treatment plant can expect the pump to deliver wastewater at higher efficiency for at least another 20-30 years if not longer.

If it’s time to rehabilitate your screw pump, ask us about it! We gladly provide no obligation consultations to businesses and municipalities in Wisconsin and upper Michigan.

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Eric Finnila

Eric Finnila

Eric Finnila is the Field Sales Manager for the Water and Wastewater group at Crane Engineering. Eric has extensive knowledge in wastewater treatment processes, and managing large wastewater asset rehabilitations, like lift stations and clarifiers.

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