Question: This question relates to the pounds per gallon rating. “On our tank trailers, we have a pound-per-gallon rating. Is there a rating for this on our tank containers? Do we have a maximum pound per gallon rating?”
Tank Guru: There is a definitely a maximum cargo weight you can carry, but the terminology in the tank container industry is a little different from the tank trailer industry, at least in the U.S.
For a tank container it is based on the Maximum Gross Weight (MGW) of the tank. For instance, on many new tanks the MGW is 36000 KG or 79,365 lbs. If you subtract from that the tare weight of 7,500 lbs. for a representative 24000 liter T11 tank, you would have a Maximum Payload carrying capacity of 71,865 lbs.
So if you filled that 24000 liter tank to the minimum safe-transport level of 80% you would have a payload of 19200 liters or 5,072 gallons. Therefore the cargo could weigh up to 14.169 lbs. per gallon (71,865/5,072). Now, you could never legally scale a load that heavy, but if you could the tank could handle it. So in theory, that would be the pound-per-gallon rating. In actual practice, you will be shipping loads of lighter density products in 24000 liter tanks (and probably to a higher filling ratio), but you can still use the same math for any sized tank and its actual MGW (less its actual tare weight). Or, you could even use 24000 liter tanks at a lower filling ratio if baffles are installed — but just don’t forget to include the weight of any added baffles to the tare weight of the tank (because of the reduction to the payload capacity). Hope that helps!