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Hi everyone,
I have a question about a possible scenario that might lead to static accumulation that may contribute to a possible fire when unloading jet fuel from a storage tank into a truck.
The scenario is as follows: kerosene (flammable class liquid) is stored in a 2500 L horizontal storage tank and will be unloaded into a tanker once 90% of the tank's capacity is reached. The method for unloading the tank is by opening the manway on top of the tank and putting a spear and hose connected to the truck's pump into it. The pump will then pump the kerosene out of the tank and into the tanker. The tanker has a bottom loading design and the storage tank has an open vent. This is a manned operation.
I've already implemented the conventional risk mitigation techniques to limit static accumulation in the tank and tanker (i.e. limiting the pump's flowrate as per API 2003, and implementing adequate earthing and bonding for both) but I've been wondering if it is plausible that, once all the kerosene has been pumped out of the tank, could pumping the kerosene exhaust in the tank as well as any air from the atmosphere be considered a hazard as well? (the tank has no low level alarms or switches so it is possible to continue pumping exhaust and air into the tanker once the liquid has been pumped out).
My concern is twofold:
(i) that there might be static accumulation due to exhaust being pumped out
(ii) that since the manway is open during the unloading, air will come into contact with the liquid and exhaust in the tank, thereby introducing more oxygen to a flammable mixture, which might lead to a greater risk of fire
I couldn't find much information on this specific scenario in any standards (probably because static accumulation when gas moves is not generally considered to be substantial enough to cause a fire or explosion).
Apologies if I am overthinking (or underthinking) but I have not dealt with static accumulation that much before this, so I would just like to get the professionals' take on whether my concerns are valid or not. Thanks!
