Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
(OP)
Does anyone have a quick method/rule of thumb that can be used as the sizing basis for a slug catcher/separator located on the inlet to a compressor on a natural gas line.
The intent of the vessel is to just avoid any liquid carry-over into the compressor. So far, the idea is to place a control valve on the inlet to the vessel to minimize the slug flow into the vessel. If I have this control valve in place does this mean that any size vessel (16" above) will work?
Any help would be much appreciated.
thank you.
The intent of the vessel is to just avoid any liquid carry-over into the compressor. So far, the idea is to place a control valve on the inlet to the vessel to minimize the slug flow into the vessel. If I have this control valve in place does this mean that any size vessel (16" above) will work?
Any help would be much appreciated.
thank you.





RE: Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
(1) See GPSA Chapter 7.
(2) In answer to your last question...no. Consideration of settling velocity, liquid level, droplet size and other parameters in combination will show what size works and what size does not work. The slug-buster valve on the separator inlet serves mainly to optimally size the dump valves on the liquid outlet, with some corollary benefit of simultaneously throttling the gas rate somewhat. I am not sure that I would count on that valve to help downsize the separator much, beyond its raw slug capacity.
Regards,
SNORGY.
RE: Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
I don't have a decent quantative solution below 50 psia. As a stopgap I generally use 100 pipe diameters of fluid hitting the slug catcher at 100 ft/sec. I've been using this "technique" for nearly 10 years without an upset that caused me to rethink it. You're welcome to it, but know that it is just about as arbitrary as any "rule of thumb" you'll ever see. The problem is that there really isn't any published experimental data for low-pressure gas.
David
RE: Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
I've not seen a control valve in front of a slug catcher.. ever. If I had seen one, I would have expected to see someone removing the pieces after it had been destroyed by a slug impact. You normally don't want control valves before slug catchers in lines with enough liquids in them to need a slug catcher. You want to have as much of a constant flow operation as possible to minimize slug formations.
I think that FIRST you must decide if this is going to be a simple KNOCKOUT POT or a real SLUG catcher.
We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer
RE: Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
I looked in GPSA 12th edition - chapter 7 and there is only a couple of lines on slug catchers. No formulas or methodology presented. Perhaps you all are referring to an older version?
Operating pressure is around 750 psi.
"BigInch" the idea for the inlet control valve was only to protect against a high level shutdown if the valving downstream of the vessel was overloaded. It will be open most of the time. Does this still seem like a bad idea to you?
thanks again.
Juujee12
RE: Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
Put the level control valve on the slug catcher, downstream on the gas side. If the liquid volume coming in is exceeding your ability to handle the liquids through the liquid system, pinch the gas outlet flow from the slug catcher.
RE: Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
When the slug catcher is full, I would think that you should shut down the compressor station, as any further liquid entry would presumedly carry a very high risk of flow through the slug catcher and into the compressor. Put that level control valve dcasto mentioned on the slug catcher and dump the accumulated liquids. If for some reason you can't dump the liquid to the normal disposal route, plan on completely closing a valve between the pipeline and slug catcher when the slug catcher goes to HHi level and shutting off the compressor until the slug catcher has returned to operating levels. Then, and only then, reopen the pipeline valve and start the compressor again.
We will design everything from now on using only S.I. units ... except for the pipe diameter. Unk. British engineer
RE: Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
First thing you have to do is to figure out how big the slug is. If it is the result of pigging then it will be of considerable size.
If you want to see what the pipe or finger type slug catcher looks like then check the Taylor Forge website.
The design steps for a real pipe type slug catcher is far more complex than can be discussed in this forum.
RE: Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
Regards,
SNORGY.
RE: Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line
Thank you all so much for your input.
Regards,
Juujee12
RE: Quick method for sizing a Slug Catcher/Separator on a Nat Gas Line