Displacement (prox) probes

have a pipeline pump in Ethane service that is outfitted with prox probes... pump trips after an hour in service.... trying to get to the bottom of that now. 

My question is this..... on the drive end of the pump, one prod probe trips the pump at 4.2 mils while its sister probe is only reading 1.5 mils displacement. 

Is there a rule of thumb as to how close in amplitude a set of prox probes should measure to one another? It just struck me as odd to see this high amplitude "difference" between the two probes. 

Would appreciate any advice or experience on this one. 

Thanks 

KB

Original Post

What you describe could be perfectly normal

Mile High_PumpFE posted:

have a pipeline pump in Ethane service that is outfitted with prox probes... pump trips after an hour in service.... trying to get to the bottom of that now. 

My question is this..... on the drive end of the pump, one prod probe trips the pump at 4.2 mils while its sister probe is only reading 1.5 mils displacement. 

Is there a rule of thumb as to how close in amplitude a set of prox probes should measure to one another? It just struck me as odd to see this high amplitude "difference" between the two probes. 

Would appreciate any advice or experience on this one. 

Thanks 

KB

If the 4.2 mils is a reasonable limit for the pump the situation certainly deserves investigation so you might want to add some data to this thread.  What is the history of this machine?  Is this something in the way of a recent change?  Has any work been done on the pump recently?

As to a rule of thumb normally the readings are close, something like a ratio of 2:3 would be expected.  As they differ by a larger number the orbit becomes more elliptical.  Causes can range from something as simple as a bad probe to a wiped bearing, locked up coupling, misalignment...the list goes on!

 

 

 

 

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