Offshore Platform drainage
Offshore Platform drainage
(OP)
Dear members,
We are designing a offshore platform and have come across a basic question on design of hazardous open drainage. There are limitations in treating that and owner decided to collect the contents and ship to onshore. Having decided that they wanted to size the collection tank as small as possible which is possible only by avoiding rain water falling on the collection areas. Since bunds (coaming) is provided under all hydrocarbon vessels the total drainage load has been estimated to be vety high.
In order to overcome the above, Owner raised a query why the pressure vessels (Flare KO Drum, Methanol Drum etc.)need bunds below them. Their point is that since all such pressurised vessels are provided with closed connection to the closed drainage, spillage is not expected from them and hence bunding not required. They are OK with providing bunding for atmoshperic tanks such as diesel and lube oil tanks to cater to overflows etc.
I referred to Shell DEP also but it does not give any clarification which equipment call for bunding and whether Owner's point is right (removing bunds for pressurized vessels). Advise/feedback from you is highly appreciated.
Thanks
Techv
We are designing a offshore platform and have come across a basic question on design of hazardous open drainage. There are limitations in treating that and owner decided to collect the contents and ship to onshore. Having decided that they wanted to size the collection tank as small as possible which is possible only by avoiding rain water falling on the collection areas. Since bunds (coaming) is provided under all hydrocarbon vessels the total drainage load has been estimated to be vety high.
In order to overcome the above, Owner raised a query why the pressure vessels (Flare KO Drum, Methanol Drum etc.)need bunds below them. Their point is that since all such pressurised vessels are provided with closed connection to the closed drainage, spillage is not expected from them and hence bunding not required. They are OK with providing bunding for atmoshperic tanks such as diesel and lube oil tanks to cater to overflows etc.
I referred to Shell DEP also but it does not give any clarification which equipment call for bunding and whether Owner's point is right (removing bunds for pressurized vessels). Advise/feedback from you is highly appreciated.
Thanks
Techv





RE: Offshore Platform drainage
Best regards
Morten
RE: Offshore Platform drainage
The Spill Prevention, Control, and Countermeasure (SPCC) rule includes requirements for oil spill prevention, preparedness, and response to prevent oil discharges to navigable waters and adjoining shorelines. The rule requires specific facilities to prepare, amend, and implement SPCC Plans.
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"(c) Provide appropriate containment and/or diversionary structures or equipment to prevent a discharge as described in ยง112.1(b), except as provided in paragraph (k) of this section for qualified oil-filled operational equipment. The entire containment system, including walls and floor, must be capable of containing oil and must be constructed so that any discharge from a primary containment system, such as a tank or pipe, will not escape the containment system before cleanup occurs. At a minimum, you must use one of the following prevention systems or its equivalent:
.......................
(2) For offshore facilities:
(i) Curbing or drip pans; or
(ii) Sumps and collection systems."
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RE: Offshore Platform drainage
Best regards
Morten
RE: Offshore Platform drainage
Usual practice is to dump drain systems into open bottomed caisson(s) where hydrogens and water settle out and the oil is skimmed off the top and pumped back into production. If you have your open drain system discharging into the same caisson as the closed drain system, make sure that the drain leg of the former is suffiently lower than the laatter to ensure that pressure discharges due to the closed drain will not introduce vapour through-out the open drain system.