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Old 04-24-2019, 06:39 PM   #1
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Default Motor bearing replacement

I went to look at a 10 hp base mounted fire pump today.

The complaint was that it was "sparking and smoking". First thought was that the motor was done. When I got there, the sparking and smoke was actually coming from the pump itself, and the motor was OK. The pump bearings are drier than an Alberta winter, the whole thing and all the attached sprinkler piping was vibrating, so it sounded like a 3600 rpm rock tumbler. I told the client(a very large landlord) the pump will have to be looked at by one of our sprinklerfitters, but most likely is going to have to be rebuilt. It's from 1973.

Now, getting to my point - I also told them this is a good time to get the motor serviced and the bearings replaced. Thing is, I don't know a whole lot about bearings. I know the motor shop will probably just replace like for like, but what I want to know is, can you just slap sealed bearings into a motor that previously didn't have them?

I'm asking because, I service gazillions of fire pumps and fire pump controllers, mostly for this one client, and these things are not like motors in a regular industrial environment where someone following a PM program will periodically grease them. Most are ancient, live in a wet environment, only operate sporadically, and except for me, nobody I've ever seen does any maintenance on these motors until they blow up, at which point the building has to be on fire watch until a replacement comes in. If we can get sealed bearings in there, that completely removes greasing from the equation, and could save the client a lot of money.
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Old 04-24-2019, 06:45 PM   #2
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What about auto greasers? The only reason I suggest that is because it is fire fighting equipment... you know that if there is an issue someone will say there is non-spec bearing in the motor...

While auto greasers will need maintenance also, you might be able to increase your PM cycle to quarterly verses monthly...

Cheers
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Old 04-24-2019, 07:15 PM   #3
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I’ve mixed matched bearings before but not on a fire pump. The number will end in a 2-RS for a double sealed bearing or ZZ for double metal shields. For example a 6208 2RS is a double sealed bearing. A 6208 ZZ has double shields. I routinely rebearing motors when I have some slowish time. I’ve grabbed a motor off my spare shelf and gotten a down plant back together several times because I repair motors with bearing sets when noisy rather than run them to destruction like my co workers will.
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Old 04-24-2019, 07:45 PM   #4
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If you do go with sealed bearings, I'd remove the grease zerk and put a plug in it. That way the next guy would stand a fighting chance that they won't try and pump a crap ton of grease into a sealed bearing.

The only issue I can see with an auto luber is if the motor doesn't run often, you are putting grease in, and it's gotta go somewhere. Even if the bottle is set for the longest duration (12 months) it may be too much if the motor doesn't run.
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Old 04-24-2019, 09:06 PM   #5
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Bearings have tolerances and those must be adhered to when replacing them.
You shouldn't just replace without checking all the tolerances.
Inner race. Outer race. End bells and shaft tolerances.
A bad bearing replacement can cause more harm than good. So if you have a machine shop in house, go for it. If not use a machine shop.
Bushing end bells and shaft work is not always possible in house.

Oh...like said above. When changing to a sealed bearing from an open bearing, remove the grease fitting "Zerk" and plug hole.

When I comes to pump assemblies I tried to never separate the motor from the pump.
I found sending the complete motor and pump into the shop is the best bet. This way you get a rebuilt pump while you are at it. New seals and gaskets.
Besides. It can be hard to reassemble in house. Sometimes it never gets reassembled.

When I pulled these things I tried to install unions so the whole assembly can be removed by loosening two union fittings.
Then when it comes back, its two unions, mounting bolts, electrical connections and done.

Last edited by John Valdes; 04-24-2019 at 09:10 PM.
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Old 04-24-2019, 10:23 PM   #6
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Have you ever used flexible couplings for the drive shaft?
https://www.mscdirect.com/browse/tn/...vid=4287923716


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Old 04-25-2019, 12:20 AM   #7
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Quote:
Originally Posted by Bird dog View Post
Have you ever used flexible couplings for the drive shaft?
https://www.mscdirect.com/browse/tn/...vid=4287923716


Yup quite often. We run quite a few fractional horse pumps and that's what they use..
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Old 04-25-2019, 05:35 AM   #8
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Quote:
Originally Posted by Navyguy View Post
What about auto greasers? The only reason I suggest that is because it is fire fighting equipment... you know that if there is an issue someone will say there is non-spec bearing in the motor...

While auto greasers will need maintenance also, you might be able to increase your PM cycle to quarterly verses monthly...

Cheers
John
Quote:
Originally Posted by glen1971 View Post
If you do go with sealed bearings, I'd remove the grease zerk and put a plug in it. That way the next guy would stand a fighting chance that they won't try and pump a crap ton of grease into a sealed bearing.

The only issue I can see with an auto luber is if the motor doesn't run often, you are putting grease in, and it's gotta go somewhere. Even if the bottle is set for the longest duration (12 months) it may be too much if the motor doesn't run.
The auto greaser is a neat idea but I still don’t see it working out. Nobody will maintain the greaser and I seem to be the only one who understands that these things need grease at all. These people own hundreds of buildings. When these pumps get tested annually, the only thing they care about is whether it makes the rated GPM. And yeah, the grease will pile up eventually too from not running that much. I also don’t want to be responsible for making sure a particular grease is used.


Quote:
Originally Posted by John Valdes View Post
Bearings have tolerances and those must be adhered to when replacing them.
You shouldn't just replace without checking all the tolerances.
Inner race. Outer race. End bells and shaft tolerances.
A bad bearing replacement can cause more harm than good. So if you have a machine shop in house, go for it. If not use a machine shop.
Bushing end bells and shaft work is not always possible in house.

Oh...like said above. When changing to a sealed bearing from an open bearing, remove the grease fitting "Zerk" and plug hole.

When I comes to pump assemblies I tried to never separate the motor from the pump.
I found sending the complete motor and pump into the shop is the best bet. This way you get a rebuilt pump while you are at it. New seals and gaskets.
Besides. It can be hard to reassemble in house. Sometimes it never gets reassembled.

When I pulled these things I tried to install unions so the whole assembly can be removed by loosening two union fittings.
Then when it comes back, its two unions, mounting bolts, electrical connections and done.
I certainly won’t be doing any bearing jobs personally. The plan was to send both pump and motor to a motor/pump specialist shop that presumably is equipped to check all of these things and do a complete rebuild. I’m just trying to understand if it’s possible/a good idea to request sealed bearings when they do it.

Quote:
Originally Posted by Bird dog View Post
Have you ever used flexible couplings for the drive shaft?
https://www.mscdirect.com/browse/tn/...vid=4287923716


Yes, this pump already has one actually.
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Old 04-25-2019, 07:54 AM   #9
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Quote:
Originally Posted by Vintage Sounds View Post
The auto greaser is a neat idea but I still don’t see it working out. Nobody will maintain the greaser and I seem to be the only one who understands that these things need grease at all. These people own hundreds of buildings. When these pumps get tested annually, the only thing they care about is whether it makes the rated GPM. And yeah, the grease will pile up eventually too from not running that much. I also don’t want to be responsible for making sure a particular grease is used.
Can you suggest that during their annual test, you come by and check the amperage of the motor, and properly grease each one? I would outline the risks of an auto luber and over greasing the motor, which will lead to premature failures. Do the pumps have sealed bearings, or are they greasable too?
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Old 04-25-2019, 12:32 PM   #10
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Quote:
Originally Posted by Bird dog View Post
I certainly won’t be doing any bearing jobs personally. The plan was to send both pump and motor to a motor/pump specialist shop that presumably is equipped to check all of these things and do a complete rebuild. I’m just trying to understand if it’s possible/a good idea to request sealed bearings when they do it.
Depends on the application. Bearings come in three configurations. Open, shielded and sealed.
Clearly sealed is for the most demanding applications and environment.
I would ask the shop where you are sending the motor and pump to. See what they say?
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Old 04-25-2019, 05:28 PM   #11
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Quote:
Originally Posted by John Valdes View Post
Bearings have tolerances and those must be adhered to when replacing them.
You shouldn't just replace without checking all the tolerances.
Inner race. Outer race. End bells and shaft tolerances.
A bad bearing replacement can cause more harm than good. So if you have a machine shop in house, go for it. If not use a machine shop.
Bushing end bells and shaft work is not always possible in house.

Oh...like said above. When changing to a sealed bearing from an open bearing, remove the grease fitting "Zerk" and plug hole.

When I comes to pump assemblies I tried to never separate the motor from the pump.
I found sending the complete motor and pump into the shop is the best bet. This way you get a rebuilt pump while you are at it. New seals and gaskets.
Besides. It can be hard to reassemble in house. Sometimes it never gets reassembled.

When I pulled these things I tried to install unions so the whole assembly can be removed by loosening two union fittings.
Then when it comes back, its two unions, mounting bolts, electrical connections and done.
Are you suggesting a loaner pump while its out for repair?

I would suggest buying a complete new pump and have the old one serviced and brought back as a spare if at all practical.
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Old 04-25-2019, 06:30 PM   #12
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Is re-building a 10 Hp motor economically sensible vs a new motor? I guess they're not rewinding it. I'm curious to know what they charge and for what.
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Old 04-25-2019, 06:31 PM   #13
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Also, nice to hear you landed on your feet back in the center of the universe, uh, I mean TO.
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Old 04-25-2019, 06:47 PM   #14
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New bearings? Should be. They aren't that expensive. I think rewinding is a different story though.

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Old 04-25-2019, 08:54 PM   #15
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I just did a bearing job on a 213T 7 1/2 hp and a 254T 15 hp. About $50 bucks for the 213T and a little more than a $100 for the 254T. A couple hours labor a piece, and all is well.
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Old 04-26-2019, 10:48 AM   #16
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The thing with bearing changes you need the right equipment to do them yourself.

You need a good quality press may be two (one small and one large), tons of shims, lots of dies, etc. If you are doing them on a regular basis or doing other millwright work such as pumps, gearboxes, etc then it can be a good investment.

I quite liked doing that sort of work, but never did it as a job. I have not done any of that stuff in a while now... kind of miss it actually.

Cheers
John
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Old 04-26-2019, 11:47 AM   #17
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Quote:
Originally Posted by Southeast Power View Post
Are you suggesting a loaner pump while its out for repair?
No.

Quote:
I would suggest buying a complete new pump and have the old one serviced and brought back as a spare if at all practical.
Exactly. My point was to let the shop take the complete pump and motor assembly.
This way when you get it back, its ready to be installed.
I have seen way to many pump assemblies never put back together for some reason or another.

Quote:
Originally Posted by stuiec View Post
Is re-building a 10 Hp motor economically sensible vs a new motor? I guess they're not rewinding it. I'm curious to know what they charge and for what.
Depends if its a stock motor that is easily sourced and on a shelf near you.
Most pump motors are not not everyday stock and most have shaft modifications. But then they can still be a stock motor.
It really depends on the motor and how it attaches to the pump.

Generally a 10 HP motor that needs work is best replaced. A good shop will quote the new vs the repair.
When I left the motor shop, more than 60% of motors coming in got replaced. I would bet that figure has risen.
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Old 04-26-2019, 11:55 AM   #18
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Replacement beats repair. It's strictly a case of the $$$$.

We're talking fire pumps here.

Keep the insurance man happy.
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Old 04-27-2019, 01:29 PM   #19
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If you do go with sealed bearings, I'd remove the grease zerk and put a plug in it. That way the next guy would stand a fighting chance that they won't try and pump a crap ton of grease into a sealed bearing.

The only issue I can see with an auto luber is if the motor doesn't run often, you are putting grease in, and it's gotta go somewhere. Even if the bottle is set for the longest duration (12 months) it may be too much if the motor doesn't run.
Fire pumps are supposed to be tested monthly according to Code ...usually loosen shaft packing a bit and have pressure reg set to drain for minimum flow for 5 min test.
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Old 04-27-2019, 04:50 PM   #20
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Fire pumps are supposed to be tested monthly according to Code ...usually loosen shaft packing a bit and have pressure reg set to drain for minimum flow for 5 min test.
At 60 minutes of run time a year, that wouldn't even need to be greased and would be horribly over-greased if using an auto luber..
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