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Reciprocating Compressor Vent And Drains

reciprocating compressor vent drain

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#1 james.corrobro@gmail.com

james.corrobro@gmail.com

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Posted 02 April 2019 - 05:46 PM

hi, 

 

For reciprocating compressor, I see that for skid mounted units, there are connections such as

1. Packing vent and drain, 2. Unloader vent and 3. distance piece drain

we have closed drain system at 7 PSIG and a sump or saver pit at atmospheric pressure, our flare backpressure is 3-4 psig. What is best way to route these drain and vents. 

For packing vent and drain do we need a small pot or separator to separate vapor and liq?? can we take liq to oil pit or closed drain? 

for distance piece drain can we take to close drain or saver pit?

for unloader vent can we take to flare??

please help.

 

jc



#2 Art Montemayor

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Posted 02 April 2019 - 07:57 PM

The previous thread is composed and edited:

 

Hi,

 

For a reciprocating compressor, I see that for skid mounted units, there are connections such as

  1. Packing vent and drain;
  2. Unloader vent; and
  3. distance piece drain.

We have closed drain system at 7 PSIG and a sump or saver pit at atmospheric pressure, our flare backpressure is 3-4 psig.

 

What is best way to route these drains and vents?
For packing vent and drain do we need a small pot or separator to separate vapor and liq??
Can we take liquid to oil pit or closed drain?
For distance piece drain can we take to close drain or saver pit?
For unloader vent can we take to flare??

 

please help.
JC



#3 Art Montemayor

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Posted 02 April 2019 - 08:00 PM

JC:

 

Your query, besides being badly composed, makes little sense.  I have edited and formatted it so it can be better understood.

 

All reciprocating compressors, whether they be skid mounted or stand-alone, have the same requirements for venting and blowdown gases - as well as condensate removal.  Where did you “see” your claimed information?

 

Are you presently operating the compressor you describe with vents and drains?  If so, what gas (complete with constituents) are you compressing - and in how many stages.  Show us in a detailed sketch which are your vents, drains, and other flows going to your flare and waste disposal.

 

There should never be any piston rod packing “drains” on a reciprocating compressor.  I don’t know what you mean by that phrase.

 

Are you using process gas to actuate your valve unloaders instead of instrument air?

 

The distance piece in a reciprocating compressor is a non-pressurized item that is meant to segregate a compression cylinder from the crosshead and ultimately from the crankcase.  This is to avoid cylinder oil and compressed gas from migrating through the piston rod via packing gland.  It is expected that the packing box will not leak under normal operation.  The only thing that could collect in the distance piece is lubricating oil from the packing gland - in drops per day.  Is that what you are referring to?

 

If you have a multi-stage compressor, what is the composition of the condensate collected?  What are you presently doing with it after it supposedly goes to your drain system and sump?

 

All piston rod packing is not designed to drain liquids.  What liquids are coming through your rod packing?  Reciprocating compressors compress gases - not liquids.  There should be no liquids in your compressor’s cylinders during normal operation - except for a minuscule oil film if you have a lubricated compressor.  I assume your compressor is NOT a non-lube reciprocating unit.

 

I can’t tell you if you can “take liquid to oil pit or closed drain”.  I don’t know what your liquid contains and whether you can contaminate your drained oil.  I don't know anything about your liquid disposal system.  



#4 james.corrobro@gmail.com

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Posted 02 April 2019 - 08:43 PM

hello sir, I have typed some replies in red below. I will try to give more detailed information as well 

 

All reciprocating compressors, whether they be skid mounted or stand-alone, have the same requirements for venting and blowdown gases - as well as condensate removal.  Where did you “see” your claimed information?

The claimed information is from a compressor manufacturer’s GA drawing showing all skid edge connections. I am not proficient with all the parts and including vents and drains for recip compressors, hence have some basic queries. Compressor model is Ariel JGT/4 and Engine is CAT 3516B

 

Are you presently operating the compressor you describe with vents and drains?  If so, what gas (complete with constituents) are you compressing - and in how many stages.  Show us in a detailed sketch which are your vents, drains, and other flows going to your flare and waste disposal.

Gas being compressed is natural  gas with around 82 mol% methane.

 

There should never be any piston rod packing “drains” on a reciprocating compressor.  I don’t know what you mean by that phrase.

 The connection mentions Packing vent/drain. Hence I wanted to understand if we can expect any liquid from the packing which would need to be separated before disposing off the vapor.

Are you using process gas to actuate your valve unloaders instead of instrument air?

We are using instrument air for valve unloaders. Does unloader vent only vent the air used for actuation?

 

The distance piece in a reciprocating compressor is a non-pressurized item that is meant to segregate a compression cylinder from the crosshead and ultimately from the crankcase.  This is to avoid cylinder oil and compressed gas from migrating through the piston rod via packing gland.  It is expected that the packing box will not leak under normal operation.  The only thing that could collect in the distance piece is lubricating oil from the packing gland - in drops per day.  Is that what you are referring to?

Yes, I am referring to that liquid / lubricating oil. We have an oil saver pit and a closed drain system. I assume best would be to take the oil to a saver pit.

 

If you have a multi-stage compressor, what is the composition of the condensate collected?  What are you presently doing with it after it supposedly goes to your drain system and sump?

Condensate goes to the closed drain system. It is then pumped to an adjacent plant where it is again sent to a separator vessel.  

 

All piston rod packing is not designed to drain liquids.  What liquids are coming through your rod packing?  Reciprocating compressors compress gases - not liquids.  There should be no liquids in your compressor’s cylinders during normal operation - except for a minuscule oil film if you have a lubricated compressor.  I assume your compressor is NOT a non-lube reciprocating unit.

It is a lubricated compressor. Do we need to separate this oil before we vent the gas? From the packing is the gas pressurized

 

I can’t tell you if you can “take liquid to oil pit or closed drain”.  I don’t know what your liquid contains and whether you can contaminate your drained oil.  I don't know anything about your liquid disposal system.  



#5 breizh

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Posted 02 April 2019 - 08:59 PM

https://www.arielcor...ion-Technology/

Hi, 

Consider the link above .

good luck,

Breizh



#6 GK18

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Posted 18 April 2019 - 02:19 AM

For drains from distance piece, you can follow the arrangement provided in Annex-I (i.e. Figure I-1 and I-2) of API 618. I hope that would help you in making right choice.






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