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Reciprocating Compressor - Purging the Lube System of Air

04/09/2009 11:55 AM

I'm writing a procedure for an old recip compressor going into a new service and for commissioning, we need to purge the lube system of air. I'm assuming that the best way to do this is to use the hand pump and open the filter bleed to purge air out of that section and then open a bleed on the end of the bearing supply header and use the hand pump to be sure I've pushed the air out of all of that section as well.

Anyone have any other tips or tricks to use? Lets assume that I've already done particulate flushing and all that other jazz and I just need to get the air out after having the lube circuit bolted back together for the last time.

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#1

Re: Recip Lube System Commissioning

04/09/2009 1:15 PM

On what sound like smaller recips (of the V-8 auto variety) we used to prelube by pulling the (generally) distributor shaft so we could run the oil pump with an electric drill with an adapter chucked. As you say, this is after all other pre-start precautions have been taken.

Don't know if this would be appropriate for your application tho...

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#2

Re: Reciprocating Compressor - Purging the Lube System of Air

04/09/2009 11:10 PM

I don't think you have do anything other than start it and run. The reason is the system has a gear pump (?) and if the compressor was put back together using proper techniques there should be ample oil (residual) in the bearings and crankshaft to take at least 3 minutes of run time to purge all air from the system. I'm assuming the bearings have free flow without orifices.

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#3

Re: Reciprocating Compressor - Purging the Lube System of Air

04/10/2009 12:41 AM

So bottom line of the question is taking all air from the lube oil system of the compressor. You want to make sure that all the system is well lubricated with oil. There should not be any air pocket inside the system. Is my understanding on your question correct?

Then, run the lube oil system for 10 min. before you start the compressor.
You run the lube oil pump (aux. lube oil pump when the main oil pump is compressor shaft driven) 10 min advanced earlier than compressor.

Just check the lube oil pressure and when it is OK and stablized, then you can run the compressor.

All air inside the line and header will be vent leaving the oil tank for the time being.

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#4

Re: Reciprocating Compressor - Purging the Lube System of Air

04/10/2009 12:44 AM

Assuming that you only have a shaft driven pump, and not external supply pumps this sounds about right. If you have a seperate lube skid with pumps, then just run those and much sure you are getting flow. However I am with May, seems to me you ought to be able to start with out worrying too much about it. As long as your shaft pump is working.

I am also assuming that you are talking about frame lube only, and not cylinders...oh and I am assuming this is a big process machine and not a bitty air compressor sitting on a receiver.

Lots of assumptions...

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#5

Re: Reciprocating Compressor - Purging the Lube System of Air

04/10/2009 3:56 AM

Too many assumptions would need to go into play to give a particular start up procedure without more info.

But one thing for sure with any type is to be sure you start up and stay in the un-load mode until your compressor has full oil pressure and is moving at rated speed.

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#6

Re: Reciprocating Compressor - Purging the Lube System of Air

04/10/2009 8:38 AM

Sorry it is an old DR 2200 hp 6 throw machine that has a 480 VAC aux lube pump with a shaft-driven main pump. There is a hand pump as well. Most of the oil piping is new and the aux pump is new as well.

General consensus seems to be that I may not even need to use the hand pump, I can just rely on the aux pump to push all the air into the frame (reservoir).

Yes, the cylinder lube is a different story, what would you suggest to get that system ready for start?

Thanks for the responses so far.

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#7
In reply to #6

Re: Reciprocating Compressor - Purging the Lube System of Air

04/10/2009 5:40 PM

Add oil to the sump, a little over fill, not too much. Prime the system with the little hand pump whilst having cracked the lines to the bearing. Pump until the oil seeps from fittings and then fire up the machine. Oil to the cylinder walls will be flung on by the counter-weights and the mains will have enough oil in them until the aux lube system build enough head to push any remaining air/oil to the main rollers.

When oil is now seen seeping from the fittings tighten them and continue to run. Have the compressor in the unloaded mode. Run unloaded until the equipment reaches an elevated temperature. Monitor the crank bearings with a temperature gun The bearings should be within 10F of each other. Close the bypass valve and load the compressor until the high pressure cutoff activates. Check to make sure the cut off is at the proper pressure as not to over load the unit. Cycle the unit from low to high five or six times. All's good, put unit into service. Change the oil out after 10 hrs service or drain and discard if shipping. Be sure to tag, "Oil to be added upon receiving".

Cheers, Good luck.

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