Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


VS4 pump having high vibration possibly due to wrong bush clearances

VS4 pump having high vibration possibly due to wrong bush clearances

VS4 pump having high vibration possibly due to wrong bush clearances

Hi, a VS4 type vertical pump is having high vibration though the pump was recently overhauled. The pump bushes were replaced during the overhaul and the sleeve-bush clearance was 0.28 mm. The issue was that the pump manufacturer did not provide any design range for the bush clearances therefore we set between 0.25 - 0.30 mm. The sleeve diameter is 40 mm.
Soon after the overhaul, the pump was run and the horizontal value of vibration seems to be on the higher side at the motor D.E side. The motor bearings were also replaced.

What do you guys think could be the issue? Also, API 610 does not provide the recommended values for the bush clearances in a VS4 pumps. Is there an authentic journal or standard that can be followed to set the bush clearances in vertical pumps.


RE: VS4 pump having high vibration possibly due to wrong bush clearances

What's the coupling design?

Assume it was all aligned OK in static condition?

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

RE: VS4 pump having high vibration possibly due to wrong bush clearances

Was the clearance when pump was removed prior to overhaul 0.28 mm? Were the same high vibrations present then? What wear was indicated on the shaft journal and bushing/bearing?


RE: VS4 pump having high vibration possibly due to wrong bush clearances

I built pumps for over nine years.

Usually default to Mark's handbook to figure clearances...

I'm assuming Bronze bushing and Stainless Steel sleeves.

If pumping water, these are the clearances that I used for shafting turning 1800 rpm .010" - .015" or roughly .25mm to .38mm

What type of impeller? open? closed?

I have seen these problems with short coupled pumps:

wrong rotation which causes the threaded couplings to unscrew. This causes a side loading and whip action of shafting.

misalignment of motor to shafting

incorrect balance of impeller or impellers

shafting incorrectly straightened or not straightened, IF shaft is one piece and turned it may have relieved internal stresses and is bent.

wrong clearances

and my favorite one: severe Cavitation blamed as a balance issue......

RE: VS4 pump having high vibration possibly due to wrong bush clearances

For that shaft size, I would specify the clearance as 0.006 inch to 0.009 inch on the diameter for a bronze bushing over a stainless steel shaft or sleeve. I am assuming 3600 rpm or 1800 rpm. Your bushing clearance may be a little bit on the high side. I would add to the excellent list that JS provided:

Shaft run-out caused by a threaded coupler where the shaft ends but up against one another
A bent shaft caused by buckling after running at excessively high flow rate, resulting in upthrust.

It would be easier for us to make good suggestions if you provided the number of stages, the bushing material, the sleeve material, the rotational speed and the fluid being pumped.

Johnny Pellin

RE: VS4 pump having high vibration possibly due to wrong bush clearances

In addition to checking alignment at the coupling, also check run-outs on coupling hub to to shaft. On some occasions you could have a severely off center bore in your coupling. That could add significant vibration depending on coupling style and size.

When it comes to couplings we are always here to help.

RE: VS4 pump having high vibration possibly due to wrong bush clearances

Thanks guys,

The coupling is a jaw coupling.

The pump was initially overhauled due to the same reason, high vibrations. When our vibration analyst performed the analysis, he found high bush clearances to be the reason. We removed the pump and replaced the bushings with new ones as a lot of scoring was observed in the bushings though the sleeve was found to be good and smooth. The bushings are not bronze but polymer based. The clearance values of the old bushings could not be measured accurately due to heavy scoring but these were within the range of 0.30 to 0.35.

We also checked the runout of all the shaft and a maximum value of 0.05 mm was found.

Any imbalance in the impeller was not checked though.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


White Paper - The State of Product Development and Hardware Design 2019
The most successful companies are usually the ones that never rest. They are always striving to get better, to deliver more innovative products and get them to market faster. Onshape surveyed 850 product design and manufacturing pros to learn what techniques and strategies they’ve employed to keep ahead of their competition and in this white paper their answers are distilled. Download Now
Research Report - Mass Customization Placing Design in the Customers Hands
Products come in all shapes and sizes, and customers demand solutions tailored to their needs. With mass customization software, these two facts can be reconciled in an automated, customer-facing experience called a product configurator. In this engineering.com research report, we examine the different levels of mass customization with the pyramid of product configurators. Taking a look at real-world case studies, we discover how the highest level of the pyramid can enable true engineering automation, saving time and increasing customer satisfaction. Download Now
Research Report - Test and Simulation Survey
We at engineering.com continually hear how engineers and designers will be doing simulation, such as FEA and CFD, and that they will be doing it early in the design cycle. Is this wishful thinking? We found out what it is really like in industry. Read more now. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close