Motor bearing replacement - cost data

[gmorin]

I have a 650 hp motor on a vertical pump. The thrust bearing is located in the motor housing. The proposed thrust bearing is rated for 50,000 hrs - so I'd need to count on changing it out once every 5 years or so.

Can anyone provide some budgetary cost data on a bearing replacement of a motor of this size? I'm trying to evaluate the capiatal cost of this bearing vs. another type.

Thanks

Greg

 

[Skogsgurra]

The 50 k hours are a minimum life. You should get a lot more hours out of the bearing. The number given is the so-called L10 lifetime. It is defined so that 90 percent of all bearings in a batch survive the 50 000 hours when carrying rated load at rated speed. It is not unusual to get many times that life out of a bearing.

There is one exception, though. And that is when the motor is fed from a frequency inverter. If precautions like filters, hybrid bearings or shaft grounding are not taken, you will end up with a very short life - total failure after a couple of months or half a year is not uncommon.

There is a newly started forum (forum1119 and thread1119-110832) where these things are discussed - or will be discussed.

 

[gmorin]

Thanks.

I'm starting with the L-10 life to do a rough cost justification. It's conservative, so I(hopefully) get no arguments.

I can get a bearing cost off a spare parts sheet, I just have no way of estimating the labor / subcontract price to replace the bearing.

No inverter - just a medium voltage constant speed AC motor.

 

[Skogsgurra]

The labour cost will be highly dependent on how easy it is to dismantle the motor - and that cost depends on how accessible the end-bell and bearing is. The motor probably needs to be lifted and an installed beam above the motor will reduce cost considerably. It is almost impossible to estimate this cost without knowing what the installation looks like. I think that you should get some quotations from a couple of engineering companies.

 

[gmorin]

Problem is that I'm at an engineering company...

It'll be located in a pump bay with a bridge crane overhead, so I don't have to figure in too much wrestling with the motor. I was anticipating disconnecting the motor and sending it off-site

I can take a stab at the cost to remove / reinstall the motor. What I'm really looking for is an idea of the subcontract price for a shop to swap out the bearing.

 

[Skogsgurra]

That job usually can be done in a couple of hours. I have no clue as to what the shops cost in your part of the world. Let's say somewhere around USD 100 for the replacement. You will probably need to test spin the motor as well - add another USD 100 for putting the motor on a test bed, connecting it and running it.

 

[electricpete]

I was thinking quite a bit higher than $200. Maybe $1,000 - $2,000 for the labor for replacement upper bearing plus unloaded test run. Also add materials for the bearings. Also, depending on who is involved with the project there may be request for some extra scope: might as well replace lower bearing... What about balance? cleaning? Extra stuff that gets noticed while we're in there.

I would ask for a quick and dirty estimate from a motor repair shop - they should be more than happy, especially if a possibility the work might eventually come to them.

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[electricpete]

skogsgurra - it might not be a bad idea to post a separate thread in the motor forum and the bearing forum to announce that new forum.

It does seem to be an extremely narrow focus for a forum. Is there a vfd forum?

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[Skogsgurra]

Pete,

I assumed that removal, transport as well as re-installation should be made by gmorin's engineering company. He also states that he can get the price for the bearing from his spare parts list. The cost for the actual replacement shouldn't be very high. But I think that you are right that my estimate is on the low side. I tend to forget that equipment also cost - and that companies need a decent return on their investments.