Over the years I have posted several articles about hazardous materials being unloaded to the wrong tank. And it seems that each time I do I get several e-mails stating how rare these events are and that I am being an alarmist. So I thought I would post a section of a PHMSA Investigation Report from an incident where Sulfuric Acid was unloaded into a tank with Hydrochloric Acid. The host facility knew what was in the tank; however, they did not inform the driver of the tank contents. The acid tank was NOT labeled and things go downhill from there. Count the number of failures from this listing of the events leading up to the gas release…
On January 3rd, 2014 a driver was delivering a load of sulfuric acid to a facility. He arrived at 10:50 am at which time he was met by a worker, who opened the gate. This worker went back to placing a sign on the tank marking it as sulfuric acid. Driver asked him if they had room for the load of sulfuric acid and if they had the other half of the flange. Drivers do not carry flanges on their truck And he needed this part to hook the 2″ hose to acid tank. Worker was not sure so he went into the office and the driver met another worker, who was said to be the head person in charge. “I told the head person in charge was there to deliver a load of sulfuric acid and I needed a way to hook up to their tank”.
The head person in charge and driver went into the supply room and found a 2″ coupler that would work to off load from the truck into the sulfuric acid tank. Both the head person in charge and driver placed the new fitting on the sulfuric acid tank. At this time the driver showed the head person in charge the bill of lading and the certificate of analysis and he signed the copy. After signing my bill of Lading, Driver asked the head person in charge if they had enough room for the load of sulfuric acid. The head person in charge said “our tank is a 3000 gallon tank and there is 500 gallons of sulfuric acid in the tank”. Driver stated he had about 2000 gallons and asked the head person in charge if it was okay to unload. The head person in charge said “go ahead”.
Driver hooked up the 2″ hose from the sulfuric acid tanker onto the sulfuric acid tank and opened their valve. After opening the valve on the tanker the driver walked over to the connection at the sulfuric acid tank, that’s when the sulfuric acid tank started to shake. A cloud of gas started down the outside of the sulfuric acid tank. Driver ran back to his tanker to shut off the valve. While shutting off the valve he was over taken by the gas.
The valve was now closed so the driver headed into the shipping office to inform the head person in charge that there was gas coming out of their sulfuric acid tank and if he was sure that it was sulfuric acid in the tank. The head person in charge replied “there is hydrochloric acid but that’s okay they are compatible acids.” Driver said “no they are not, you need to come and see the cloud of gas, I need Help!” Driver left head person in charge and went outside to shutdown the truck and to call his boss.
Driver called his boss who asked if 911 was called and if not we needed to call them now. The head person in charge came out of the shipping building and said the fire department was on the way. The driver’s boss asked who “authorized the unload of sulfuric acid”, driver told him that head person in charge authorized it and at this time handed the head person in charge the phone. The head person in charge told the driver’s supervisor that he authorized the unload of the sulfuric acid into their sulfuric acid tank.
The fire department arrived and head person in charge asked them to give the driver medical treatment. They transported the driver to the hospital.
Source: https://hip.phmsa.dot.gov/analyticsSOAP/saw.dll?Dashboard
FYI the gas exiting the tank was Hydrogen Chloride gas. Normal strength hydrochloric acid is ~36% (varies) which means there is a lot of water in with the HCl. Sulfuric Acid is usually at least 93% acid and will give off a lot of heat when mixed with water. The contents in the tank were boiling from the acid water reaction, thus generating the gas/vapor.