proper lube before start up after extended rest

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I have a few questions if someone could make some insightful suggestions. and the current lubrication oil that is being used is mobil teresstic 46.
With plain bearings lubricated by dipper rings, what is the best approach to assure adequate lubrication during startup? We recently experienced a case whereby we wiped a bearing on an 850 horsepower MG set. Since this equipment is not used on a daily basis, it is possible for the lubricant to drain back into the reservoir allowing the journal and babbitt to rest in contact. When the machine starts, there may be little to no lubricant available until the shaft comes up to speed (1800 rpm) and the dipper rings begin to rotate picking up the oil and delivering it to the bearing. During this interval, we have essentially no lubrication and the babbitt material becomes hot.

Some additional questions are as follows:

1. Should we be adding a solid lubricant to the oil such as graphite or molybdenum disulfide to aid in the initial lubrication?
2. Are there any special lubricants developed for this situation where the machinery is shut down for extended periods?
3. Would it be advisable to remove the bearing caps and manually lubricate the bearing (at least the upper half) prior to starting?
4. Since a heavy journal resting in one spot for an extended period of time may distort the babbitt lining and cause it to assume an egg shaped pattern, should we be starting the machine and running it for a short while on a periodic basis? If so, how frequently?

1/24/1310:10 AM

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jmorganMember

It's never advisable to add components. You change the chemistry which the lubricant was designed to operate. There are hydraulic fluids specifically engineered with moly built into the formulation so you know the chemistry is right. Schaeffer's 112, 254 and 158 are all designed to work in the environment you've described. E-mail me at schaefferoiltexas@gmail.com I will send you tech data and energy studies for these fluids.

1/24/133:05 PM

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renewaMember

1. Some lubricant manufacturers offer an aerosol form of the Molybdenum disulfide (mainly for open gears and chain lubrication) - it may be one option to lubricate the bearings but discuss with your lubricant supplier about the suitability of using these style of products . There are also running in type compounds that can be added again check with lube supplier on whether it is suitable.
2.Where there are extended periods of shut down, then a vapour phase inhibitor can be added to the oil to protect against corrosion - it works by coating the unimmersed parts of the component. This additive is typically used in agricultural oils whereby farming equipment is not used for a number of months during the year. Again speak to your lube supplier to see if you are able to source the neat additive direct - generally 1 to 2 % is added to resevoir oil of the system. Provided the oil is suitable for further use in the first place, it generally does not require dumping at start up time Alternatively use an agricultural style oil and grease with VPI incorporated in it's formulation matched closest to the current product in use.
3. I have come across applications where grease is cleaned out of the bearing caps and regreased but I am not sure how effective this strategy is, perhaps other more experienced members of the forum are able to advise. Generally the bearings are sealed off to ensure no moisture or dirt can get in. There are also oil mist preservation strategies.
4. Not sure

There are articles on preservation strategies which may provide you with more information one of which is protection of equipment during standby, storage and decommissioning.

I hope this helps.

1/24/137:29 PM

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