Design of Flare system 1

[SSSHARMA]

Sir,
I would like to know if the flare line leading to flare can be buried 1-2 meter below the groung and top surface can be concertised . The flare knock out drum is planned to be kept near the installation and flare line approx. 90 m is planned to be taken underground.The flare tip would be appox. 30 m in height for safe flaring of gas. The design capacity of the flare would be approx. 1,00,000 scmd . The concept if used anywhere in petrochemical/oil-gas industry in onshore conditions may be referred.
sssharma

 

[MortenA]

i dont see any problems as such - just remember that its common to have a drop towards the flare KO drum. This will be difficult if you dont bury the KO drum also.

Its most common to have the flare header on an elevated piperack. This enables road crossing etc. without leg and pockets in the header.

Another problem that strikes me concerning burying the pipe is that you quite often think up new uses for the flare line. If you want to connect to the buried section later on its going to be a lot of hassle.

Best regards

Morten

 

[Flareman]

The biggest potential problems I see with buried headers are

- drainage - you will certainly dis-entrain liquids in the header which have to be collected somewhere; even an inoperative header will act as a condenser and collect atmospheric water;

- the need to put associated drums below ground in pits; these are then poorly vented hazardous locations which need breathing apparatus avialable for personnel access

- corrosion - you may need to coat the entire line with an epoxy coating which makes future modification a real "pain"; perhaps you even need to consider cathodic protection;

- restrained expansion - is that why you mention "concertised" (a term I'm not familiar with)? Underground flare lines which are not in trenches move around little by little and can compact the material in which they are embedded (gravel?), eventually one of the expansions is too great and the pipe ruptures underground creating a difficult situation.

You can design against all the above problems but, it seem to me, you avoid most by putting the pipes on a rack.


David

 

[SSSHARMA]

Thanks for the reply. It would be better if such an instance is qouted where submerged flare system has been designed and working satisfactorilly.
The problems in submerged flare line are plenty but the situation so demands that the flare line be submerged 1-2 meter below ground.
The reference of standards used in such case may be referred .
sssharma

 

[Phil100]

I think that it will be virtually impossible to guarantee that a buried flare header is drained and hence at full capacity and available to receive pressurised releases. The flare is intended to be the ultimate safe release point for any overpressure excursions on a high pressure processing plant with the potential to become a large bomb!
The points raised by others relating to corrosion, inspection etc are all valid and need to be thought through thoroughly.
You need to carry out a risk assessment to justify any non-standard designs such as this and be prepared to justify your thoughts to a judge!!

 

[RotaryG]

I know little about flare lines. But, would like to congratulate SSS.... for posing the question clearly so that those in the knowledge could answer him to the point.

Regards,

Guru

"Evolution rather than Revolution"