Rotate the shaft 2 1/4 turn weekly - API 686 - ? 2

[reallyme00]

Dear All,

I appreciate if anyone could clear me this doubt as i am very new to rotating equipments.

"mark the shaft and rotate 2 1/4 revolutions weekly as a part of preservation in all machinery’s as per API-686".
In this statement, why the rotation is 2 1/4 turn. What is the specific reason?

Thanks in advance.

 

[vpl]

I'm not familiar with API Codes, but the reason I learned for rotating non-operating "rotating equipment" (such as a pump in storage) is as follows:

Rotating the shaft 2 turns ensures that it is free to rotate and prevents any oxidation (rust) buildup.

Rotating the shaft that last 1/4 turn means the orientation is changed so you don't get any "sag" in the shaft from being in one orientation for a long time.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[ScottyUK]

If it runs on a roller or ball bearing then any low level of background vibration can, over a long period, cause an effect called 'false brinelling' which leads to damage like in this image:

http://www.emersonbearing.com/fail_falsebrinell.htm.

The 2 1/4 turns is probably an effort to ensure that the shaft, or more accurately the bearing elements, do not come to rest in the same location after each rotation. Whether it is successful will depend on the bearing design.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[Artisi]

every week sounds excessive - once a month should suffice if stored in a clean stable temperature and vibration free area.

The neeed to rotate a couple of times is to ensure the bearings are evenly coated with lubricant to prevent corrosion and the 1/4 turn is to put the static bearing load onto a different part of the bearing each time.

 

[waross]

Nice link Scotty. Worth a thousand words.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[electricpete]

I'm with vpl on the reason for the extra quarter turn - to prevent shaft bow.

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[electricpete]

And Artisi captures what I believe the reason for the 2 turns is... to spread lubricant around on all the bearing surfaces to prevent oxidation.

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[reallyme00]

Dear All,

I am really thankful to all of you. Its amazing to get such a worthy response.

I am satisfied with your inputs and thank you once again for sharing your knowledge.

 

[pumpking]

If you are long term storing a pump, it is also very important to make sure machined surfaces and internals are covered with rust inhibitor - just had to put our hands in our pocket as gesture of goodwill as one of our customers had a spare pump ion the shelf for nearly 2 years, went to use it, solid, rust, bearings etc etc.

Good customer, so hey, thats life sometimes - made me laugh to myself however, as long term storgae and preservation procedures were tagged to the pump...

Customer is king !!!!

Ash Fenn

http://www.cdrpumps.co.uk

 

[Artisi]

sounds typical - when all else fails read the instructions.

Reminds me of a call from the customer some years back:

Customer. "We started the pump, the motor goes round but the pump doesn't"

Me. being one step ahead and guessing what had happend:
"Did you check the coupling alignment and motor direction before starting the pump" Trying to not laugh.

C. "of course"

Me. I suggest you re-check everything, as the pump was shipped without the spacer coupling fitted so that is probably why the motor goes round and the pump doesn't"

C. "Oh"

Heard back a few days later from another source - they found the coupling in the store with the fitting instructons attached.

 

[PwrPumpGuy]

The reason you would want to rotate the shaft is so that flat spots do not develop on the ball bearings from sitting idle for a long period of time. Generally, it is once a month. However, as can often be the case, trying to avoid one problem can cause another. Depending on situation, clearances, materials, ect., rotating the shaft in a piece of dry equipment can cause issues with galling; example 316 on 316.

Ideally, if you have experienced personnel that know the equipment, and can adequately mitigate possible problems, you can perform this task with little risk.