Identical Boiler D.M.Water Pumps Bearings repeted Failure

Dear Members ,

We have two Identical Boiler D.M.Water Pumps in one of our customer plant ,Theirs Bearings failure happening repeatedly ,

SULZER 80*65-200 Model Pump

6 impeller vanes ,EN -8 Shaft Material .

Pump bearings no 6306 zz ,

Please refer below shared data & share Your opinions .

 

Attachments

Files (3)
DMWP 1 SPECTRUM
DMWP 2 SPECTRUM
DMWP 2 Thernal Image
Original Post

Vibration velocity values and temperature values are all acceptable so I would expect to record some PeakVue and acceleration data. However bearings/bearing seats on the first pump seem to have some looseness as seen from the spectrum. I can't see your thermal image for the first pump. The temperature on the 2nd pump coupling is higher from the pump side, but this is something usual and does not neccessary show the bearings failure. Have you checked the alignment?

Kishore kumar,

What is your resolution in the spectrums? Appears a little low.

And why are the waveforms displayed or collected in velocity instead of Gs acceleration? Just asking.

Can you display your spectrums in either Hz or orders and your Waveforms in rpm's rather than time?

I know none of these questions are related to your concern of "Why".

Another question or two.

. Are they running in oil or grease?

Why are they using bearings that are shielded on both sides? Very difficult to get oil or grease in them with both sides shielded and running at 3,000 rpm, IMO.

Thanks and Have a Great Day,

Ralph

Pump bearings are oil bath lubricated,initial vibration readings are normal when the new bearings are installed .Then after vibration readings are gradually increasing along with bearings damage.

Load on bearings observed ,since installation ,even though vibration readings are low.

normally, shielded bearing are having grease inside, that's what my foundation knowledge, it seems your using shielded bearing subsequently the pump are oil bath? is that the OEM type of bearing for that pump. 

Refer to the process side, how long the discharge pipe from the header? what is the your so called bearing damage? from both side bearing is damage? 

Im tryin to figure out what the damages on the bearing.

It is not obvious to me why double shielded bearings are used with oil bath lubrication as indicated. Single and double shielded ball bearings are typically used with grease lubrication. One of the corrective actions for repeated premature bearing failure should be to evaluate for correct bearings, correct installation and correct lubrication for the application. Check pump thrust bearing for correct gap or preload, depending on design and OEM specification.

Walt

Sulzer is a very reputable pump, if you are having repeated failures as others have stated you have to know what is failing first and how? Do bearings look like the got hot, pump noisy during operation, wrong oil viscosity, and so on....did a search for your model and came up with nothing, Do you have a Model number for the pump

Dave 

Which bearing is this in the pictures, the coupling end or the NDE Bearing?

The picture seems to show the bearing is basically loaded 360 degrees, but more in the load zone. Am I correct in what I think I see?

It does not appear to be failing from lack of lubrication, at least I do not see any "burn" marks.

Thanks and Have a Great Day,

Ralph

 

It's a D.E side bearing , pump and motor coupled with jaw coupling.Fitter aligned the pump and motor after bearings replacement..But  not with dials or lease ,rough alignment done.

They didn't have any such alignment tools and experience.Alrady I insisted about tolerance and fits along with proper dial alignment and thermal growth check.Because water temperature at 50 to 70 °c.

You should not be using shielded bearings inside a pump bearing housing with an oil bath. I would guess that someone thought this would be a good idea after a failure. It is not and could very well impede proper lubrication. Looks like a standard wear pattern on your bearing except not prevalent in one load zone. Bearing may have been turning in the housing. If the bearing is in an oil bath ditch the shielded version to an open version. Check your shaft and housing dimensions to ensure they are proper and always do a proper laser alignment. If you are not doing a proper alignment you are wasting time and resources chasing your tail as they say.

When the new bearings installed,there is no sound and vibration but in the spectrum we found load in bearings and the values are with in the limits.

Last time bearings are ran up to a month with out  increase ,then increased vibration and noise with increasing trend .Some times this trend happen with in two or three days after new bearings installation.

These pumps pumping condensed hot water temperature ranging from 45°c to 70 °c .But the pump designed to withstand uptown 90 °c.

Kishore,

How hot do they have to heat the bearings to install them on the shaft?

How tight are the outer race fits to the bearing housing?

If the shaft and housing fits are ok, then,

(1) You recommended a C3 fit bearing and the problem still continues.

(2) Try the,  high temperature, tight fit, and large clearance C5 fit. Just a suggestion.

Quote: "Radial clearance is classified on a C1, C2, CN, C3, C4 and C5 scale, with clearance increasing toward the highest number, which is C5. When noise or vibration is an issue, internal clearance is reduced, typically to the C1 or C2 range depending on the application.Larger clearance classes of C4 or C5 are used in applications requiring a heavy interference fit or experience high operating temperatures."

Worth a test trial based on the constant reoccurring failures.

Thanks and Have a Great Day,

Ralph

Kishore if what you say is true and you are not using precision maintenance practices then you will not solve these issues long term. Until rigor is put into the process of proper lubrication and rebuilds and repairs you will not and cannot change anything long term with PdM and root cause (only observe the same failures occurring). Generally I would suggest building standard operating procedures and sign off check sheets for repairs and installation however you may be best served by buying a new spare and using an OEM rebuild shop for the repairs in the future. OEM rebuild shops will usually have the right tools, parts, training and OEM documentation to perform these repairs to take the units to an "as new" condition everytime. This will allow you to concentrate on precision installation (including laser alignment, soft foot, piping strain etc...) and should provide better reliability. My two cents.

Punching and rough handling appears to be installation marks on the inner race that I see. The pump appears to have been in service for many years, the pump nameplate does not call out any special tolerances for your 6306 bearings. So if the pump has just recently seen rapid failures, what changed.

No bearing will survive a steel hammer and steel punch to install bearings. The images of your bearings show no lack of lubrication, shaft fits, just from the image, appear to be good, there is not "brown" stuff on the bearing races? Your images do not show the outside/housing side of the bearing.

Again the markings on the inner race indicate poor installation techniques as others have stated on this post

http://www.mx.nsk.com/download...ngDoctor_for_web.pdf

page/item 6.17 mounting flaws

Dave

Kishore kumar posted:

Dear Ralph ,

In this plant they don't have even drawing and manufacturer manuals. All the maintenance do with a rough tolerance and alignment..

Bearings are installed by punching and rough handling.All the things done on trial and error basis.

Well it is quite sad that they have no more pride in their workmanship and management has no desire to give the mechanics the proper tools to do a better job, and then they might as well accept the fact that this problem will probably never change for the better.

Surely they have something they could heat the bearing with? A bearing as small as this pumps bearings could be heated by laying it on the rake in the oven of a kitchen stove,  with the use of careful handling so as not to burn one's self. I have done this at home on some home projects. Just my opinion so do not do it on my advice.

DISCLAIMER:

I am merely saying "where there is a will there is usually a way" and am in no way responsible for the results if one tries this.

Another concern or question of mine is, " how are the other machines in the plant surviving and these can not? I assume the same type installation procedure is performed on the others also, huh?"

A hammer is the worse tool in a mechanic's toolbox when it comes to proper maintenance of equipment. I have seen mechanics trying to drive parts on a pump, fan, etc. and can not do it, so the solution is a "bigger hammer". A hammer has it a purpose but it is not to drive a cold bearing on an interference fit application.

You seem to not have answered the question about the outer race being or showing, on the failed bearing, to be "loaded" full circle of the outer race, or did I miss it?

Just my opinion and I could be totally wrong

  1. The bearings on the pump name plate is 6306 Z C3 & you are installing 6306 ZZ C3. ZZ bearings makes your oil bath useless. Please go for correct bearings. however it doesn't look like a lubrication failure.
  2. RPM of the machine is 2950 as per pump name plate & doing rough alignment on this is not at all a good practice. Does the coupling spider also fails?
  3. Spectrum attached DMWP1 indicates towards some looseness. You need to measure housing & shaft tolerances if you want to investigate & find the cause.

For some reason many industrial managers and supervisors have the belief that by spending money on condition monitoring (CM) that their equipment failure rates will drop. The disconnect seems to be not understanding that CM is reconnaissance for the planning department to allow them extra time to plan for interventions instead of reacting to them. It in no way changes failure rates unless proactive maintenance (PrM) measures are employed and acted upon as an extension of the findings of CM. In order to change failure rates we need to change machine design, operational practices, maintenance practices or a combination of these utilizing the outcome of PrM. The key word here is change. If nothing is changed, nothing changes.

Just reading this now and I concur with what the majority are saying, Kishore you are doing an exemplary job, just your client seems to think pdm alone will help, it is so very frustrating to have recommendations you make go on deaf ears when you know a few simple culture changes could improve reliability. 

I wish you luck as unfortunately modern times it seems to be harder and harder to establish this ethic in modern factories and the skilled workforce is dwindling.

 

 

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