Hi, I am looking for an extinguisher solution for a mineral oil quench tank. Briefly, the process is that hot material is immersed in the oil to cool it. The oil is circulated through a heat exchanged to cool the oil. The concern is that should the oil reach its flash point how would we extinguish the fire. This has never happened in the past. The tank has CO2 extinguishant systems on it, but I suspect that once the CO2 has dissipated, the oil could reignite. So I was thinking of something like an AFFF extinguisher, on a trolley that we could use should this happen, extinguishing the fire and allowing the oil to cool naturally. Has anyone got any experience with this? Thanks in advance

johno If there is a foreseeable risk of the oil being ignited and the area of the open top of the tank isn't too big, a simple, low cost and effective measure could be to have a single or multi-piece metal lid/cover which could be slid or hinged over the top. It's the industrial equivalent of placing a metal or gauze lid or a fire blanket over blazing oil in a kitchen chip pan. Covering/enclosing any fire helps to deprive it of air (effectively the oxygen in air) which is needed to sustain combustion. This is partly achieved by containing and concentrating the fumes from the fire so that they exclude air and act as an asphyxiant. However, it's worth ascertaining how likely it is that a fire could occur and therefore what measures should be taken to try and reduce the likelihood. This could involves consideration of various factors such as how much oil is in the tank, how many hot items of what size (mass) and temperature are quenched in it and at what rate. Is there any means by which the temperature of the oil can be monitored while the tank is in use? If so, perhaps the oil supplier and/or others could suggest a temperature at which it would be prudent to temporarily stop quenching items until the heat exchanger had cooled the oil sufficiently to allow resumption of quenching. As the above points are based on simple principles (secondary school science level) regarding heat and fire, hopefully forum users with greater experience of quench tanks can give more detailed advice.

Thanks for the advice, the tanks have a substantial 'snuffer plate' that lowers automatically. I am not aware of the oil ever catching fire, but the soot around it has occasionally caught fire, this is just part of the process and is contained within the tank The tank has a temperature display and we know what is a safe quench temperature so it would have to be a series of mistakes or failures before the oil actually went up. The tank is designed that the largest load of material cant take the oil to an unsafe temperature, the tank is about 200,000 litres.

yes, the snuffer works as you describe. the flash point is quite high, im checking what it is currently as we have it analysed regularly. As for the possibility of it leaking, well, its in a very substantial concrete and steel tank, and the pipework is designed so that any leak would drain back into the bund. Its all in doors, set into the floor. Anyway, Its useful to think out loud sometimes, this is one of those occasions!

Thanks, that all sounds familiar. I think ill get the foam setup as a last resort, just in case. Thanks for the discussion :)

Just to be absolutely clear, I know the foam will float on the oil, my concern is the foam overflowing and causing slip hazards and just causing a girt big mess in the middle of a flap... Jim

Keep right on thinking Deeps. This is all over my head but its good to get an insight into these things. Rob

Ill ask about the thermal shock when the rep comes to see me