321sol,
Your original question: "Can an oil/water separator be located inside the bund wall of a tank farm?"
If the fluids in the Storage Tanks are Hydrocarbon (i.e.: Flammable) then the answer is NO!
Try This: NFPA 820 Standard for Fire Protection in Wastewater Treatment and Collection Facilities
Sometimes its possible to do all the right things and still get bad results
Yes, I am talking about storage tanks for hydrocarbons (mogas, gaspoil, fuel oil) but I do not think NFPA 820 applies to us. It applies mostly to sewers and places that treat waste water.
Does this oily water separator treat oily water from other bunded areas ? If it does, then it may not be a good idea to keep it in this storage tank bunded area. In the event of a major spill in this bunded area, typical practice is to isolate all feeds into and out of this bunded area (with emergency shutdown valves located just outside the bund perimeter), which will include the feed to this oily water sep also. So this sep will not be able to handle oily water streams from other bunded area in this emergency, thus escalating the impact of this local spill to a plant wide event.
If it deals with oily water fluids from this bunded area only, this should be okay ( from the little information you've provided so far) as long as bunded area containment volume for the largest of the storage tanks in this bunded area is not compromised.
One key issue is "does the separator have a burner?" If so then you don't want it to be the ignition source for a big fire.
If not, then the big question is do you want a pressure vessel compromised if there is a fire from another source within the bund? A jet fire will burn through any amount of steel, so if you have a hole in a tank (corrosion, gunshot, bad weld) that can jet towards the separator then you have just involved your entire gathering system and possibly your wells in a fire. All to save the price of a bund? Sounds like a false economy to me.
The oily water separator will not receive oily water from other bunded areas and it does not have a burner. Granted the products in the tanks are stored under atmospheric pressure, jetting from a low level hole is a concern of mine but the distance between the tank and bund wall seems adequate.
I will heed your warnings and advise management on moving the oily water separator to an area outside the bund.
The oily water separator is used to separate storm water from any petroleum products in the bunded area and not for discharge of the petroleum in the event of a catastrophic failure of the tank, fire or no fire.
If there is a catastrophic failure of the tank, then there is nothing the oily water separator can do even of its in the bunded area or not. Only if there is rainfall, then I guess it can come into play. But for a catastrophic failure, the product in the bunded area has to be pumped out to other storage tanks. If there is a fire, one would definitely not want product getting out of the bunded area. The product would have to be contained and covered with foam.
Any conduits leading through the bunded area would always have gate valves on either side and a always kept close. Therefore, for a catastrophic failure, no product can get out of the bund.
Therefore, it does not seem to matter whether the oily water separator in inside or outside the bunded area.
Note that this bunded area is not connected to any other bunded areas and there are no burners on the separator.
Just think for a moment. The purpose of an oily water separator, which is what I assume you mean, is to remove the small traces of oil / product from rain water that land sin the hopefully impermeable bunded area. The outlet water then usually goes off to a local drain or stream / river.
Sometimes the inflow of water is too high for the separator (thunderstorm say) to cope with or maybe there is to much oil in the water and then the inlet needs to be closed. If the separator is outside the bund this is quite simple and all that happens is that you get some water in the bund which you can then let out at a slower rate.
however if it is inside the bund then all you can close is the outlet valve and the separator then gets swamped with water, all the stored oil skimmed off the top then floats back to the top and you end up with an unholy mess to fix when it stops raining.
You also often need to pump out the oil slop chamber on a regular basis and also clean it every now and then to remove sludge and dirt.
so which location works best - inside or outside the bund wall??
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
