Vertical Shaft Pump Runout

[aadell]

Hi there.
I have problem with this shaft runout. Could you explain how to measure runout?
Should I put V-block on line bearing?

 

[Artisi]

How do you know you have shaft runout?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[Tmoose]

As Artisi said, please describe the runout "problem" you have identified.

Is the pump assembled and in service?
OR, is the pump dis-assembled?

The pump manual/documentation should have overhaul procedures, including shaft straightness checking and tolerances.

It will likely say something like this -

"Check shafts for straightness and excessive wear on bearing surfaces. Check
deflection of shafts; average total runout shall not exceed 0.003” T.I.R "

 

[aadell]

Shaft is dis-assembled and customer want to check this value before service. I have no documentation.
My problem is should I put vblock at two ends of shaft or line spider bearing too?
That doesn’t make sense put v blocks at ends of shaft.
Length=4300 mm
Max Diameter= 37 mm

 

[EdStainless]

We used to put V blocks at each bearing location and then check in between.
We would also take out the bearing support locations one at a time and check at that location.
Different style pumps have different procedures.
Find a shop manual for this pump, you can't re-build it correctly without it as it will also guide you on positions and axial clearances.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[mfgenggear]

Does the shaft have centers on both ends, if so it can be verified between centers. Most shafts are fabricated between centers. Bearing diameters generally are held .0005 inch max run out. Blocks have to be extra precision. And will have to locate on two diameters that are the same size. Concentricity and or true position can be verified on a CMM.

 

[TheTick]

V-blocks are absolutely not the right tool. They may be "good enough" for some purposes, but definitely not right.

A shape can have constant "diameter" and not be circular. Famously discussed by Richard Feynman's memoir of the Challenger investigation in What Do You Care What Other People Think? (It's killing me that I can't find the relevant illustration online.)

 

[Tmoose]

If using v-blocks, indicating the entire length of each journal every .25 inch or so can paint a more complete picture of the journal roundness than diameter measurements. Shaft "straightness" as well.

https://encrypted-tbn0.gstatic.com/...KU0qGAPw523x6tIFpbz5sgtRsD1AZlyOQFhU&usqp=CAU

The angle of the V determines which of the "lobed" shapes will be masked using the indicator ointing into the V.

For many applications precision v-blocks are not necessary.
If the journal is cylindrical and the shaft is straight Wooden v-blocks can provide good results.

 

[JS_]

So what is going on with your pump, that caused you to want to measure shaft run out?

Pump Bowl shafting is .002 per foot TIR

line shafting is .005 per foot TIR

You might as well tell us spider spacing, HP, RPM..... Etc....

 

[Artisi]

JS, customer request.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[JS_]

Obviously, is it just a paper trail issue? or did something actually happen to the shafting?

I would suggest some reading material.....[:

https://en.m.wikipedia.org/wiki/Airy_points

:]

And some V blocks, in the absence of a granite plate a large milling machine table would work.

A lathe with a flat way of proper length could work as a "make shift table" for the v blocks.

If you worried about roundness a "V" Anvil Micrometer would allow for some measurements...

 

[BSMEclassof2012]

aadell:

Here is how you should measure runouts on such a long shaft.

-Mark the bearing journals on shaft (also called bearing fits) with sharpie.
-Place V blocks under those bearing journals (not on the ends). If the bearing spacing is too much, you may need to install more spiders (also called bearing retainers) in your pump. There is a spec for bearing spacing in vertical pumps.
-Put a dial indicator on shaft OD, measure and record the runouts on shaft at different locations.

Usually there are inspection templates that you can fill. Hope this helps. Good luck!