Venting NG to atmosphere 3

[norzul]

Hi Guys,

Have yu got any experience venting NG to atmosphere? Concerns on explosion, safety, etc

Thanks

norzul

 

[zdas04]

The only problems I've had have been losing the economic benefit of selling the gas, and the problems with Greenhouse gas limits. Dispersion modeling shows that the explosive envelope (i.e., the volume of space that is between the Upper Explosive Limit and the Lower Explosive Limit) is really small and with any wind at all it becomes vanisingly small.

Methane does not contribute to any form of corrosion that I've ever heard of.

David

 

[Ashereng]

We sometimes use process gas for instrument air (instrument gas). There is a constant bleed in the I/P and controllers, but the amount is quite small.

This is mostly for existing sites. I haven't seen a new site do that lately. I would think that it is no longer allowed, with existing sites grandfathered in.

How much are you venting?

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[zdas04]

I wrote an SPE paper (SPE61030)once on those venting controllers. We had an economic benefit on ripping all of them out and replacing them with non-venting controllers. Those things put more gas into the air than you would think.

David

 

[Ashereng]

David, do you have a link to that paper?

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[dkf]

To all
Is there any simple means, say free software to estimate size of dispersion plume or stack?
When you have NG that has in its composition, significative proportions of ethane, propane and butanes ( say totalling 20%in addition to methane)does this affect significatively the dispersion pattern, once these components are heavier than air at atmospheric pressure?
TIA
dkf

 

[zdas04]

Ashereng,
You can get it from the SPE e-Library. I have just put a version on my web site under the "Samples" tab, under Gathering System Samples it is the last entry.

dkf,
The software I used for dispersion modeling in my last job was on the order of $15k/seat. That is as close to "free" as I've ever seen those calculations.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[Ashereng]

David,

Thank you very much.

I appreciate you posting it on your website. The SPE e-library charges $20USD per copy. (I'm not a member.)

I also like the other articles on your site. They are very useful.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[Ashereng]

David,

May I share your article?

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[Ashereng]

I talked to a colleague, and he mentioned that at one site, all the vents are piped/tubed to supply fuel for building gas heaters.

In this case, I guess you can call it
constant bleed/zero emission/combustion product



"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[zdas04]

Ashereng,
You are welcome to anything that is there. The intent is to make you think "if he's giving this quality of stuff away, what do you get if you pay him?". Sometimes it works too. I'd appreciate that if you share any of the papers you do it through a link instead of just making a copy and mailing it, but I don't have any way to control that and it really isn't that big a deal either way.

Some controllers have the capability to pipe the exhaust to somewhere convenient (usually used to get the explosive gases out of a confined space), bringing them all together to run a burner really increases the risk that backpressure will keep them from working when needed. I'm uneasy even piping them outside of a building since I've had insects plug the end of the tubing on several occasions.

"Building heaters" seem to be a very intermittent load which would never be in sync with the intermittent supply from the controllers (how do you even keep your pilot running when all the controllers have stopped venting at the same time because of a process upset). I'm not saying it can't be done, but I'd be leary of doing it.


David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[Ashereng]

David,

We have a separate line (with regulator) that acts as a makeup to the heater. The vented gas is sucked like a venturi effect to the heaters I think?

I haven't seen it but I think/hope that's right.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[Ashereng]

Thank you for the use of your articles. I will definitely share the link to your site.



"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[norzul]

Dear All,

The link below will direct yu to my blog explaining on the SSOV application...replacing the conventional relief valve. Appreciate your feedback...

http://technical2005.blogspot.com/

Thanks

norzul

 

[Ashereng]

norzul,

That link is also in your HIPPS post. Is this what you are referring to in this thread? You are venting NG via a PSV to atmosphere? If so, you probably should have mentioned that in your OP. My reply is totally off your mark.

We don't relieve to atmosphere. Typically, we pipe our PSVs to our flare. I don't believe that we relieve any HC gas to atmosphere anymore.

I would think that there is a definite concern with explosion - same as if the flare went out. Having said that, I don't have experience sending that my HC gas to atmosphere.



"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[zdas04]

It is pretty common to vent PSV's locally on small well sites. Again, the dispersion calculations put the risk of explosion pretty low (you have to evaluate your particular situation, don't rely of broad generalizations).

About your blog ... you need younger eyes than mine to even read it. I could tell that there were some schematics, but I couldn't see a single word that I could read.

David

 

[Ashereng]

Many jurisdictions are moving to disallow that.

In sour well service, you have to flare.
In sweet well service, they are moving in that direction currently also.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[norzul]

David,

Perhaps yu need to click the respective photo to route yu to a more readable photo

try this...

http://photos1.blogger.com/blogger/6171/1348/1600/SSOV_Page_3.1.jpg

I'm sure yu can read now.

 

[norzul]

Ashereng,

The "small" PSV or we call it creep valve will only vent the NG to atmosphere when both SSOVs failed...refer to the safety protection features. This is for additional protection (may not be required).

norzul