SUBJECT: Pump modifications you can make to increase the life of mechanical seals and centrifugal pump bearings. 11-1

If you learn that you have the wrong pump in your application, and your company will not buy you the correct pump because it costs too much, you may still have the option of modifying the pump you have to increase its performance, and increase the life of the seal and bearings.

Here are a few modifications you can make to your centrifugal pump to extend the life of both the bearings and seals :

Stabilize the pump shaft. Any time you reduce shaft deflection you will increase both seal and bearing life.

Install an oversize bore stuffing box to give the mechanical seal more room.

Replace the stuffing box discharge recirculation line with a suction recirculation line connected from the bottom of the stuffing box to the suction side of the pump, or any other low pressure point in the system. Needless to say this will not work all the time. Here are four instances where suction recirculation would not be a good idea:

Go to a centerline design wet end any time the pumpage exceeds 200°F (100°C).

Use a "C" or "D" frame adapter to insure the best alignment between the pump and the motor.

Install a sight glass in the bearing housing.

Replace the bearing grease or lip seals that damage the shaft and allow moisture o penetrate into the bearing housing.

Install a better thrust bearing retention method.

Check to be sure that the pump's suction specific speed number is less than 8500 (5200 in the metric system)

Install an impeller inducer if you do not have enough NPSH available to prevent the pump from cavitating.

Install a split mechanical seal to fix a leaking pump. It doesn't make any sense to remove and disassemble a pump just to fix a leak.

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