Bearing oil sightglass venting question 7

[electricpete]

This is an indoor 4kv vertical motor manufactured by Westinghouse with oil-lubricated upper and lower bearings (picture below)

http://home.houston.rr.com/electricpete/VertMotor1.jpg

The lower bearing housing has a pipe that extends outward to the bottom of a sightglass chamber. The sightglass chamber has a fill plug on top and a drain plug near the bottom (at the same elevation as the pipe to the bearing housing).

The motor is identified with a static fill level.

The sightglass chamber is not vented. After adding oil when we screw the fill plug back in, we have noticed that the indicated oil level decreases, as if the screwing of the plug creates a positive pressure in the sightglass chamber which pushes down on the oil in the sightglass chamber and displaces into the bearing.

Questions:
Would you consider this behavior normal?
Is it safe to assume that the bearing itself breathes to atmosphere (even though the sightglass design obviously doesn’t).
Would it be a problem to drill a hole in the vent plug to eliminate this phenomenon? If not, should we shoot to have the level at the static mark before or after screwing in the fill plug.

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[electricpete]

Another concern with the existing setup is that the bearing oil level in the sightglass may not represent bearing oil level in the bearing under conditions of heatup or cooldown or other changes which can create a slight pressure or vacuum in the air volume trapped above the oil in the sightglass.

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[itsmoked]

Hi electricpete.

I would think that is abnormal. I have not heard of a sight glass EVER being vented. BUT! I have always seen the tank that the sight glass depicts vented. Partly this is to prevent exploding sight glasses and the loss of everything in the tank out the failed sight glass. (this is bad) Picture a ruptured sight glass on an engine room fuel tank. (evil)

I would certainly believe the sight glass is not properly depicting the reservoir in your case.

Now your case is strange in that you have a single sight glass connection. It MUST be vented in this case or you have a barrometer/thermometer NOT a level guage.

If this thing isn't a complete bungle, another words you can remove the cap while the unit is running and not have it void everything due to pressure/horrible-design aspects then I would certainly drill out a small hole in the cap.

 

[edison123]

pete,

You can drill a hole on the plug to vent the air. I suggest a fine-size metal filter over the vent hole to prevent ambient dust/debris getting inside the oil.

How did you the upload this picture ?

 

[electricpete]

"I have not heard of a sight glass EVER being vented"

I always see one of two setups:
A - The sightglass is vented to atmosphere at the top.
B - The sightglass top is vented back to the bearing cavity at the top.

B is a little better since vacuum or positive pressure at the bearing doesn't affect level indiction.

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[itsmoked]

I meant directly vented... I don't consider hooking back into the tank "vented".

 

[rmw]

You did not state what size the plug is, but someone out there makes a pipe plug with a sintered metal core that 'breathes' which would allow your barometric leg in order to indicate true level.

Short of that, you should put a goose neck on top of the gage to prevent dust, etc. from entering the sight glass.

It may have been the mfg'r's intention that the resorvoir would be filled using the open sight glass, and then checked periodically by removing the plug. That is to say that the sight glass is only for verifying the initial charge of the oil, not continual monitering.

Many oil resorvoirs have only a pipe plug that has to be removed to check the level, as you know.

rmw

 

[electricpete]

rmw - for electric motor bearing oil reservoirs I have always seen a live level indication (an exception may be motor/pump supplied by large 100+gallon sump with oil pumps - but that has oil pressure alarms).

edison - you can get a free website to post your pictures etc (up to 25MB) at

http://www.tripod.com

It is surprisingly easy. You can upload files through your internet explorer using ftp. I just put the file here in about 30 seconds:

http://electricpete1.tripod.com/VertMotor1.jpg

If you give it a try and have any difficulties - let me know - I'd be glad to help.

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[electricpete]

Hmmm. It looks like tripod has some restrictions on hot-linking (directly to files).

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[edison123]

Thx pete. I will try it out, I had always wanted to post some pics on eng-tips.

 

[electricpete]

Ok, it takes a little more work on tripod. You need to create an html file to link your picture so they can get their advertising in to pay for the free service.

Using notepad or word (with word save as type txt or html), create a file VertMotor1.html with the following contents
<html>

<head>
<title>kumar's link page</title>
</head>

<body>
<p><a href="VertMotor1.jpg">VertMotor1.jpg</a></p>
</body>

</html>

Save that file as VertMotor1.html (text or html format).
Then upload that file to tripod as well. The result is here:

http://electricpete1.tripod.com/VertMotor1.htm

The website I originally used is provided by my internet service provider which is roadrunner. They give a free website which doesn't have these restrictions like tripod.

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[electricpete]

Tripod probably has some tools that make it a little easier to create the html page but I haven't tried them.

A discussion of free websites is here

http://www.freewebspace.net/forums/showthread.php?t=26552

I would avoid the ones identified with an asterisk (*) since they don't have ftp.

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[itsmoked]

electricpete, edison123;


There is NO easier site for picture hosting then:

http://www.tinypic.com/

No registering, no passwords, no pages to work thru, nada! Not even a home page! Just hit the url above. Hit browse. Select your picture. You are done. It then spits out all possible routes and hot links. Pick the one you want. Paste into here.

Done.

 

[electricpete]

Let's see if we can get the motor....

http://tinypic.com/dlm03o.jpg

How long does it stay there?


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[electricpete]

It worked. I guess I'll check back in a week to see if it's still there. Most things I post are only of interest for a week or so.

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[itsmoked]

electricpete; I presume at least a month probably a year.

That graph in thread248-133430 is on "tinypic".

Don't make the mistake of tinypic"s"

Demo: Bad day at the office...

 

[edison123]

Thx itsmoked. tinypic was easy and simple.

 

[quark]

I don't find any reason to think that screwing the plug creates the positive pressure and pushing the oil level down. The depth of the plug can't create that pressur to push down the oil level. Further, breathers(or vents) are provided to push out hot vapor. One possibility may be that entrapped air slowly coming up.

What is another level indicator shown on top?

Most of the fill caps come with an annular empty space to breath out the air and vapors. Is there any chance that the original plug was replaced?

 

[motorman]

I apologize for the long winded answer and the repeating of your original questions but felt it was the best way to respond and not forcing everybody to have to scroll up and down.

“This is an indoor 4kv vertical motor manufactured by Westinghouse with oil-lubricated upper and lower bearings “

yes, it looks like one of their 5000, 5800 or 6800 frame size drip proof machines. Is it a 4 pole?
Have you been having any problems with oil leaks [the reason for the questions will be seen later in this post]

“The motor is identified with a static fill level.”

It should also have a scribe line for running level. They would put is mark on the glass when the motor was tested. Perhaps with such an old machine, someone has been working on it and replaced some parts.

“The sightglass chamber is not vented.”

Well, this is proof that the original parts on this machine have been replaced with non-Westinghouse parts. I assure you that when that motor shipped from the Westinghouse factory in Buffalo NY, it had a vented plug in the top of the sight gage.

“After adding oil when we screw the fill plug back in, we have noticed that the indicated oil level decreases, as if the screwing of the plug creates a positive pressure in the sightglass chamber which pushes down on the oil in the sightglass chamber and displaces into the bearing.”

Are you adding oil while the motor is running or static? The photo shows what looks like is the proper oil level [in both top and bottom gages BTW] for static conditions. Proper static level is near the bottom of the gage.

“Questions:
Would you consider this behavior normal?
Is it safe to assume that the bearing itself breathes to atmosphere (even though the sightglass design obviously doesn’t).”

The sightglass should be vented to atmosphere just like the pressure above the oil level is atmosphere inside the oil pot. The bearing itself will breathes atmosphere via the shaft seal clearance.

“Would it be a problem to drill a hole in the vent plug to eliminate this phenomenon? If not, should we shoot to have the level at the static mark before or after screwing in the fill plug. “

This whole design will not work properly without ALL the parts being original with a vented top plug and the bottom of the sight glass should be attached to the bottom-side of the oil pot via a hose. This arrangement means that the level shown in the glass is the oil level on the side of the oil pot, not the level of the oil inside the bearing when the motor is running.
So yes, drill two holes at right angles to each other in the cap. The size of the hole depends on the size of the machine but would be either 1/8 or 1/16 inches in diameter.
Then there should be a “metering plate” resting inside the oil pot just below the bearing. Also, there should be a flinger attached to the shaft just above the inboard seal.

You might want to contact service@tecowestinghouse.com for more assistance.

 

[electricpete]

Thanks motorman

”yes, it looks like one of their 5000, 5800 or 6800 frame size drip proof machines. Is it a 4 pole?”

Yes, it is a 5800 series frame (5810-P39). Lifeline D, Type “LAC”, Model VSW6, 2-pole, Westinghouse Outline Drawing 8976D94, nuclear safety-related. Westinghouse shop order 76F52942,3,4. There is also a designation on some paperwork “G.O. LA18823-L7”

”Have you been having any problems with oil leaks”
No.

”It should also have a scribe line for running level. They would put is mark on the glass when the motor was tested. Perhaps with such an old machine, someone has been working on it and replaced some parts.”
There is a metal plate permanently affixed to the motor to identify static level. Nothing to identify running level. We have discussed running level with Westinghouse before and they told us there is no identification of running level but it should be within approx ¼” of static level mark.

“[The sightglass chamber is not vented.] - Well, this is proof that the original parts on this machine have been replaced with non-Westinghouse parts. I assure you that when that motor shipped from the Westinghouse factory in Buffalo NY, it had a vented plug in the top of the sight gage.”

I don’t know where it was manufactured. Do you know if all Westinghouse does it the same.

”Are you adding oil while the motor is running or static?”
Static.

I will try to keep an open mind to investigate the possibility that this motor may be different than it’s sisters or different than the original OEM configuration, but it doesn’t look that way to me at this point in time. Also have not got any clarifcation from the vendor yet.

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