Concrete Volute Pumps - A Situation Averted

CONCRETE VOLUTE PUMP (CVP)

DALLAS ABLE CONCRETE VOLUTE PUMPS
A SITUATION AVERTED


   The Dallas Able Pump Station houses 4 concrete volute pumps for flood control along the Trinity River.  Each pump is rated for 220,000 gallons per minute. In June of 2018 the pumps were field performance and endurance tested.  These field tests were performed to confirm that the pumps met their design regarding flow, head, speed, efficiency, vibration and noise. Field tests of this type are necessary as there are no test labs large enough for pumps like this.  The pumps had been installed and in operation for over a year now when a potential issue was discovered. One pump unit had grease leaking from the bearing housing, and upon closer inspection we found a cut o-ring and rust on the bearing grease pack. 

The possibility that these pumps could have an issue with their bearings was alarming. A bearing of this size can be expensive and difficult to replace. The gearbox weighs approximately 17,000lbs and the motor, 39,250lbs. If the motor and gearbox must be removed to access the pump bearings, the inspection would become quite a task. So, we looked for another way to remove the pump bearings.

AERIAL PHOTO OF THE DALLAS ABLE PUMP
STATION DURING PERFORMANCE TESTING

 

Flowserve developed the first concrete volute pump in the 1930s and today they are used worldwide in applications for drainage, irrigation, flood control, dry dock dewatering, cooling water, and seawater intake.

The unique design of a concrete volute pump allows for the volute housing and intake suction bell to be prefabricated during civil construction to reduce installation costs. Utilizing concrete in these components not only reduces costs but also provides reduced vibrations and improved corrosion/erosion resistance.  The expected equipment life is also extended when building the volute and suction bell from concrete.
BEARING DESIGN

The bearing design of the CVP consists of a spherical roller thrust bearing and a radial roller bearing. The spherical roller thrust bearing is oil lubricated and is provided with an oil level gauge. Both radial bearings are grease lubricated.

OUR NEXT ACTION

Flowserve arranged for a service engineer familiar with these pumps to travel from the Netherlands and provide further inspection. Due to the massive size of these pumps, the process of inspecting the bearings is not a simple task.
We started by inspecting all 4 pumps by removing their guards and opening the bearing housing covers to confirm this was an issue with each unit.
CVP BEARING HOUSING
The next plan of action was to remove the bearings and thoroughly inspect to determine if they had been damaged. With the use of rigging we were able to find a way to pull the bearings without removing the motor and gearbox. 
CVP BEARING HOUSING
 We removed the drive shafts and then used the rigging to remove the shaft-couplings, and the bearing housing covers. 
BEARING CARTRIDGE
COMES OFF NEXT
The bearing cartridges were then removed to inspect the rust observed on the grease pack.
DURING REMOVAL
After the bearing cartridge were removed, we could see that the rust-like substance was not coming from the bearings. Rust was forming outside the housing and had slipped past the bearing housing cover seal. The bearings were thoroughly inspected both in the field and in our shop to verify that there was no internal damage.  The o-ring was cut allowing grease to leave the housing and rust to enter.
GREASE PACKING THE BEARING
Now that we knew the problem, a plan of action was set up to clean and correct the issue with each pump. We proceeded by replacing the O-rings and reassembling each bearing housing cover. The housing was secured tightly for a proper seal to prevent potential rust from forming on the mating surfaces in the future.
It is important to Smith Pump Company that Flowserve products are operating properly after they have been installed, and it is our goal to continually focus on providing quality service to meet our customer's needs. It was quite fortunate that the rust was not from the bearing, and the cost to repair was minimal.  Unfortunately, not all rotating equipment problems result in such a simple repair.  We hope you found this article interesting.
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