12 replies to this topic

[dgoyal]

Hello all

I am facing difficulty in one projects my clients want the flare on offshore platform shall be 700 meters away from production platform but if I do radiation check than 60 mts distance is ok .

client want that flare shall be 700 mts away and connected by suabsea pipeline but I am not comfortable with this concept as in 700 mts distance there might be chances of condensate formation and it could lead to burning sea scenarios.

my question is
can I recommend him to a bridge connected flare or cantilever flare boom .
is there any specific reason client is asking this type of flare . is its govern by some general practice in offshore platform .

pls guide me

deepak

[JoeWong]

dgoyal,
What the basis for 60m ? Please advise.
Why clients insist on 700 meters ? Please ask your client and advise.

No way Che Jedi can advise without any information...


"700m cantilever flare boom"
Check with your structure engineer if (>700 m) cantilevel flare boom is cost effective. If your platform is fixed type, the jacket / support will be BIG !!! If your platform is floating type, i guest the Center of gravity is outside your platform edge. Again check with your structure engineer if your proposal is feasible.

"client want that flare shall be 700 mts away and connected by suabsea pipeline but I am not comfortable with this concept as in 700 mts distance there might be chances of condensate formation and it could lead to burning sea scenarios."

Has you addressed this issue to your client ? What's the response ?



JoeWong

[gvdlans]

I agree with JoeWong that you should provide us more information.

However, I can tell you a few things based on what you wrote:

- 700 m is definitely not offshore industry standard. I have done quite a few offshore projects but I've never seen such a distance. There are quite a few bridge linked or cantilevered flares out there! (off course there are no cantilevered flares for >700 m as JoeWong suggested, but this was not what dgoyal was proposing...)

- Apart from radiation limitations, there may be other issues that determine flare location, especially the dispersion of flammable and toxic gases in case of flare flame failure. Can the flare gas contain toxic components (H2S)?

- What radiation limit(s) did you use for your calculations?

[JoeWong]

(off course there are no cantilevered flares for >700 m as JoeWong suggested, but this was not what dgoyal was proposing...)

Just wanna to clarify...700m bridge linked flare was extracted from original post by dgoyal...is not my idea.

I have never seen 700m bridge linked flare offshore (even onshore with my limited experiences).



JoeWong

[gvdlans]

Never mind Joe, but.. where did the poster write "700 m bridge linked flare"?

First he/she writes about a flare 700 m from the platform, then that he/she thinks that 60 m would be sufficient and then asks whether he/she should propose a cantilever (meaning directly connected to the main platform structure) or bridge linked flare platform. It is your interpretation that the cantilever or bridge linked flare option would be for the flare 700 m away. It is my interpretation that the cantilever or bridge linked flare option would be for the flare 60 m away...

I think my interpretation is the right one because especially a cantilever flare 700 m from the platform is clearly ridiculous (and it would not have to be connected by a subsea pipeline..., same for a bridge linked flare where the flare line would be routed over the bridge).

Just an illustration of the importance of precise writing and reading. Precise writing means that you do not leave room for interpretations by the reader...

[JoeWong]

No point to interpreter a fact...


dgoyal,

Please provide precise information so that no further interpretation required.




JoeWong

[dgoyal]

[Hello Forum
Sorry for any miscommunications on my part.
And interoperation made by gvdlans is correct .

And here is answer of clarification asked on forum
1. 60 meters come from radiation calculation and the limits for normal flaring scenario is 440 Btu/Hr.ft2 and for peak its 1500 Btu/Hr.ft2 on platform .
and for these only I want to propose a cantilever or bridge connected flare .
and I am aware about fact that 700 mts cantilever flare boom is not possible.
2. These gas having H2S only 10-20 PPM .
3. And here I want to tell that maximum flare load is 80 MMSCFD .

Here I want to make clear that before going to client with all facts I want to make sure that what I am proposing to him is correct or not
So my queries are ;
1) 700 mts sub sea connected flare is offshore standard or not.
2) If not what type of flare are normally considered for offshore applications.
3) Why sub sea connected flare at all designed for offshore as I explained earlier it could lead to burning sea scenario.

Thanks for your effort

Deepak

[gvdlans]

[Hello Forum
Sorry for any miscommunications on my part.
And interoperation made by gvdlans is correct .

And here is answer of clarification asked on forum
1. 60 meters come from radiation calculation and the limits for normal flaring scenario is 440 Btu/Hr.ft2 and for peak its 1500 Btu/Hr.ft2 on platform .
and for these only I want to propose a cantilever or bridge connected flare .
and I am aware about fact that 700 mts cantilever flare boom is not possible.
2. These gas having H2S only 10-20 PPM .
3. And here I want to tell that maximum flare load is 80 MMSCFD .

Here I want to make clear that before going to client with all facts I want to make sure that what I am proposing to him is correct or not
So my queries are ;
1) 700 mts sub sea connected flare is offshore standard or not.
2) If not what type of flare are normally considered for offshore applications.
3) Why sub sea connected flare at all designed for offshore as I explained earlier it could lead to burning sea scenario.

Thanks for your effort

Deepak

Based on the information you give, I agree that flare doesn't have to be more than 60 m away. I assume that the 1500 BTU/hr.ft2 peak radiation level is for emergency flaring only (so it is a rare event). Please confirm.

Related to your queries, most of these were already answered in earlier replies, but OK:

1) 700 m subsea connected flare is not offshore standard. As an illustration: just do a Google picture search on "offshore platform" and you will see many platforms with cantilever flares...

2) Cantilever and bridge linked flares are normally considered for offshore platforms.

3) I don't know why this 700 m subsea connected flare was proposed. You should ask your clients.

I have worked on design and engineering of offshore oil and gas production platforms for quite a few years and never encountered a subsea connected flare. So my advise for you is to challenge this design based on the arguments you gave yourself. Apart from these arguments, the subsea connected flare will also be more expensive...

[JoeWong]

Many old platforms (>20 years) are having subsea connected flare. I guess it was an old design concept.

I am working on an offshore platform upgrading project. It has existing subsea connected VENT (instead of FLARE), 600m away from mother platform. Normally the line is purged, no liquid/condensate is expected in the line. In the event of relief, large gas flow (together with condensate) will push everything out from the stack and fall on the sea. In case of vent gas is ignited due to lightning, snuffing system is there to put-out the flame.

Nowadays, with the improved flare tip designed i.e. sonic tip, tulip tip, etc, normal approach is cantilever or bridge linked flare (less or no vent boom).

With 80 MMSCFD and radiation limit of 1500 Btu/Hr.ft2 during peak 9emergency), with distance of 60m (assuming 45deg boom0 boom length is about 85m, this can be easily managed by the structure group. 85m boom with 80 MMSCFD, boom length seem a bit on the high side.


JoeWong

[dgoyal]

Thanks Joe
Its great. I got answer for my queries as you are saying that flare boom length for this flow is may be high I will recheck that.

Thanks very much again

Deepak

[dgoyal]

Thanks Forum
I should say thanks to all who have given me great guidance this will help to challenge the existing design.



Deepak

[UK Engineering]

What software did you use to calculate heat radiation? or did you use API 521

[dgoyal]

i have used API521

Deepak