BB2 Pump Mechanical Seal Installation

[Rafael Dos Santos]

Greeting everyone.

Before do any mechanical seal installation, there are steps that need to be followed. One of the step is to check radial movement of shaft or shaft deflection. How are we gonna do this check on between bearing pump type?? is this step only applicable for overhung pump only?

Thank you.

 

[TugboatEng]

In your case radial play is quantitative. It's the sum of the housing to bearing clearance, the bearing internal clearance, and the bearing to shaft clearance (this one should be zero). It's not practical to measure after assembly so it must be determined before assembly.

 

[LittleInch]

Lift the shaft end and check for movement?

Bearing failure or wear or poor fitting could cause shaft movement.

If the bearings are good the there should be no movement. Check completed.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[JJPellin]

We no longer consider this as a valid check on any ball bearing pump. As noted above, you have already verified bearing to shaft fit and bearing to housing fit. You are installing a new ball bearing. No lift check is needed.

Johnny Pellin

 

[JS_]

Maybe the instructions are referring to play / clearance between the Plain bearings I.e. wear rings and wear sleeves?

Excessive clearances will affect the pump while running.

 

[TugboatEng]

When doing big gearbox work the old timers love to say, "if it rattles it rolls." Afte the build you grab the input shaft and bang it back and forth a few times. You're not taking any backlash measurements, you're just verifying the backlash is still present to rule out assembly errors. Perhaps this is a similar case?

 

[Rafael Dos Santos]

Thank you guys.

Here I attached the guideline from flowserve. For overhung, we have the leverage to lift the shaft in order to get the radial value, but for BB type, I dont think it can. Thats why Im asking.
JJPelin, so for you, you do not consider this is a valid check? It doesnt matter if it is a BB type or overhung??

 

[JJPellin]

We found that we were failing this test too often. We would disassemble the bearing housing and find no problem. A new bearing with shaft and housing fits that are within specifications can fail this test. It really tells you nothing.

If you just rebuilt the bearing housing, you know all of these measurements are good. If you are trying to decide if you need to include a bearing replacement when replacing the mechanical seal, it is a poor indicator. Vibration data and history drive this decision, not a lift check.

I do not see any value in this test. And, it will certainly drive you to do extra work and replace bearings that were perfectly fine.

Johnny Pellin