Distance between blowdown stacks in gas pressure boosting facilities 5

[abdolmaleki1975]

Hello dear friends and experts;
In a natural gas pressure boosting station, it is necessary to add a blowdown stack for emergency evacuation of the compressor station gases.
While in the area there are two stacks of incoming pipelines (56 and 40 inches), so in order to locate the third stack, we need to know the safe distance between the stacks.
Of course, I referred to the API 521 standard of the 2014 version, but the distances seemed very strange, and because I did not know the safety standards, I need help.
Thank you for your guidance.

 

[pmover]

regarding prevailing wind and urban areas . . .

typically, the mostly methane gas(?) released to atmosphere is lighter than air; thus the gas will quickly disperse and rise.

yes, the operating company should involve safety and environmental personnel.

 

[georgeverghese]

With the space constraints you are facing, would suggest it may be well worth your company's time to revisit these relief / blowdown scenarios for the existing 2 stacks to see if some spare capacity can be derived from them for any new loads. You may be surprised at the outcome of this revisit - process / safety engineers may have come up with this 3rd stack requirement without knowing the constraints you have now discovered.

For example, modification of a single stage blowdown on a compressor to a 2 stage sequenced blowdown can significantly reduce the peak blowdown rate to be accommodated at the connected stack.

Find out also if Company management have the stomach to take on some reasonable risk of including additional safety related operating procedures that will result in spare capacity at these new stacks, but this approach would be the least preferred option.

 

[GD2]

abdolmaleki1975,
If you constrained with available space, you might have to raise the stack height and do a dispersion/radiation model study with existing stacks so that radiation levels are kept to an acceptable level.

GDD
Canada

 

[abdolmaleki1975]

Dear GD2,
Thank you very much for your attention
It can be said that the dispersion/radiation model study should be done by which discipline?
With best regards

 

[abdolmaleki1975]

Hello dear friends
Is it permissible for me to use a check valve(to prevent gas from returning to the pipeline and to protect workers while working) even to use an existing stack for two purposes?

 

[1503-44]

Stacks can be used for two purposes, if sized according to the maximum expected flow and pressures.

You should never use a check valve for protection. A check valve should be considered as always leaking, or ready to leak at any moment. Some companies even require more than one ball valve and use at least two for positive isolation and worker protection purposes.

A black swan to a turkey is a white swan to the butcher.

 

[abdolmaleki1975]

Dear 1503-44,
We have also installed two plug valves on the 16" lines that comes from the pipelines, but sometimes it is possible that exactly when the workers are working on this line and this valves are open, the return of the gas will cause dangers.
or maybe those valves in the form of They are not completely sealed.

 

[1503-44]

Close the plug valves before working!
If they do not seal, install blind flanges, or spectacle blinds there. Never work against only a check or any type of leaky valve. AND always verify that no gas is exiting with a gas leak detector BEFORE starting work.

A black swan to a turkey is a white swan to the butcher.

 

[abdolmaleki1975]

Thank you 1503-44,
But this is with the operators and they know what they are doing. I just have to consider the possibilities in the design.
I was wondering if it was possible to use a 24-inch pipe, for example, as a jacket pipe on an existing 16-inch pipe(If we consider the existing 16-inch pipe as the core), how's it?.
Anyway, thank you very much for your remark about nonreturn valve leaking.

 

[1503-44]

We hope they know what to do.

I dont understand what you want to do with the jacket.

A black swan to a turkey is a white swan to the butcher.

 

[abdolmaleki1975]

Yes Sir, They have been operating the pipeline for 50 years, so they know their job.
I mean, we do not create a new stack for the new blowdown and instead join the existing stack on a part of the route(As a jacket).
Do you think this idea is acceptable?

 

[LittleInch]

He wants to build a vent inside a vent...

Well that's something new.

Don't see why it couldn't work but much easier just to build two vent pipes next to each other

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

I'd probably build a big one, connect both to it, then dismantle the old one.

A black swan to a turkey is a white swan to the butcher.