motor regreasing (need to open discharge vent port?)

In our facility it is procedure to always open the drain ports when greasing motors. The reason for this is to (as you mentioned) purge the old grease and to ensure the grease cavity does not get pressurized and force grease through the seals into the windings. Out manual grease guns are rated at a maximum of 11000psi, so this is an issue we do not want to happen.

Some of our motors (200hp plus) are actually designed with a large drain port that is always open (with some sort of flapper seal, I believe) to allow grease to be released. It is approximately 2cm x 6cm and resembles a chute of sorts.

hi, have seen those chutetype discharge vent. but mine are those about quater inch rounded vent at the bearing housing. we are concern that the old grease will not be able to discharge from this small vent. do your facility have such motors? any pics to share? appreciate if u can send to me.. glennchanky@yahoo.com ...if u have..

by the way, what do u mean by, <<ensure the grease cavity does not get pressurized and force grease through the seals into the windings>>>? hw can this prevent grease from entering the stator?? tks

Glenncjy,

I can get back to you later with some pictures, but for now I can try to answer some of your questions.

We do also have many motors that have drain ports on them that are basically 1/4 or 1/2 inch pipes. They are usually mounted to the bearing housings (drive end and opposite drive end) at 120-180 degrees around the shaft from the grease fitting. They are in place already from the manufacturer.
When we grease them (while running), we remove the drain fitting plug and slowly add grease at no more than 1 shot every 2 seconds. After greasing we leave the drain port open for a few minutes to allow for any excess/old grease to exit.
The main way that I know of to ensure that grease is not forced past the seals into the stator is to have a free drain opening. Grease guns generate a lot of pressure and it has to go somewhere.
One thing to watch for that has caught us before is the bearing type. A motor may have ports to have grease fittings installed, but the bearings were sealed/shielded on both sides and could not allow grease to enter. Check the nameplate data or with your motor rebuilder/manufacturer to be sure.
I hope this clarifies some things for you. Let me know if you have other questions. I am sure there are others here that can chip in as well.

Hi Gold luber,thank you for the reply. yes, i understand what you mean as we do have motors with grease nipple on but the bearings are of seal for life type (ZZ or 2RS type). the guys from my reliability and equpt specialist dept are not convinced that the old grease can be discharge from the small vent port. with your advise, i am mindful now that it needs to be open for a while after greasing, to allow the old grease to be discharged. thanks alot! appreciate the photo if possible..tks

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