Category Archives: tank baffles

80% filling ratio

Question:  “We have a customer that wants to load a 1.17 SG product in 24000 liter tanks.  Because the product will solidify in transport as it cools, a representative from one of the Class Societies said it would be OK. 

The problem we see is that once the product arrives overseas and is heated at a depot prior to being delivered to the customer, it will no longer be solid and we believe it will no longer meet the viscosity requirements in IMDG 4.2.1.9.6 that allow you to ignore the 80% fill rule.  But the Class Society representative says that the IMDG viscosity criteria is at 20° C, and since we are having to heat the product above 20° C in order for it to be viscous, therefore we are in luck.”

Tank Guru:  His logic makes sense; however it sounds like complying with the letter of the law but not the spirit of the law.  If the rule is there to prevent a dangerous slosh and surge situation, but you dodge the rule because ‘had the product been cooler it would have been less volatile’ — then good luck defending that position in a court of law if there is a rollover accident resulting in death or injuries.

I think you should convince your customer to use 21000 liter tanks, which will generally have a lower tare weight than larger tanks, and allow for slightly more payload anyway.      #CommonSenseSafety

Pounds-per-Gallon rating

Question:  “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!