I have found a valuable piece of info from this link. 🙂
What does the Code say about Flare stack location (Upwind or Downwind)?

I agree with Jop on Note Note No.1
I personally prefer to put the flare stack on cross wind.

Thanks

Antony,

Both your references supplied:

Reference: 8.3.1.k
Environmental Protection for Onshore Oil and Gas Production Operations and Leases
API RECOMMENDED PRACTICE 51R
FIRST EDITION, JULY 2009

and

Reference:5.8.c.1
Recommended Practice for Design and Installation of Offshore
Production Platform Piping Systems
API RECOMMENDED PRACTICE 14E (RP 14E)
FIFTH EDITION, OCTOBER 1, 1991

appear to be the opposite of what is regarded as good engineering practice – and what others on this topic have said.

That being said, there are a number of factors to consider, not least of of site personnel safety – and each plant will have its own particular set of challenges.

In a large refinery plant, where there is plenty of space, an “Upwind” location would negate any hydrocarbon gas leakage from process being transferred to flare stack which is a source of ignition for these gases.

Offshore however, ‘Downwind’ may be preferable, so as to avoid any dangers/ill-effects to plant& personnel;
There are no nearby properties so the chances/possibilities of a nearby adjoining property “going up” are remote.

Regardless of rules and codes, every project must be looked at on its own merits …
Someone said once (probably JOP)
There is a rule for everything in piping … and for every rule, there is an exception!

Regarding the reference:
“What does the Code say about Flare stack location with respect to Prevailing Wind Direction”

My comments:
Note #1 – This is dead wrong. Placing the Flare Stack (or Flare Pit) down wind of the Facility and the potential leaks could result in a Back-Flash of the Vapors and a fire in the plant.

Note #5 – This is not a good idea. It is better to have an active Pilot system. Pressure relief Valves are prone to leakage and large facilities can have hundreds of relief valves. Low pressure and low flow Vapors leaks could build up in the Flare system piping and be ignited by a lighting strike.
Real Case: A California, USA Refinery, Time: the middle of the night on a warm summer evening. Heavy Hydrocarbon Vapors were released and boiled over the top of pilot less flare stack. It then ‘flowed’ down the stack and spread out over the plant and surrounding facilities. The invisible ground cloud grew and reached a road out side the property fence. It was ignited by a person going home from a late night work shift at a Hospital at 3: am. The driver was later found to have been smoking a cigarette with the windows rolled down.

Notes #2, 3, 4, 6 & 7 – These are just Common Sense.

I found some design instructions for flare stack. hope it helpful.
1. flare stack location should be upwind direction of processing unit.
2. knock-out drum should be close to flare stack, so that their distance could be the shortest.
3. area within 60meter from flare stack shouldn’t have any public road or other facility (except knock-out drum) to avoid flare flare heat radiation.
4. flare stack should have slope and drain.
5. purge steam line should do stress analysis to decide the location of anchor and support.

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Regards.

Charlie