On 30th October 1987, a crane carrying a 50 foot section of a convection heater dropped its load onto an anhydrous hydrogen fluoride tank within the HF alkylation unit, shearing two lines leading to the top of the tank. This resulted in an air release of hydrofluoric acid at the Marathon Petroleum Company refinery in Texas City.
One line was a 4-inch acid truck loading line, and the other was a 2-inch tank pressure relief line. The tank was at the normal operating pressure of approximately 125 psi, so that when the incident occurred a cloud of HF was produced which moved with the prevailing wind. The tank originally contained 35,700 gallons of AHF, of which about 6,548 gallons was released over a 44 hour period, although the majority of the release took place during the first two hours as the tank depressurised. The release also included some light hydrocarbons (primarily isobutane) and water vapour.
The first mitigation action was to place stationary fire monitor nozzles and to erect a water spray curtain about 10 feet downwind of the release to control the HF acid vapour plume.
Approximately 4,000 people were evacuated from the residential areas threatened by the plume and the three area hospitals treated 1,037 patients, of which nearly 100 were hospitalised. There was extensive damage to trees and vegetation in the residential area.
Lines, I.G., ‘A review of the manufacture, uses, incidents and hazard models for hydrogen fluoride’, HSE Contract Research Report No. 79/1995, ISBN 0 7176 0983 9, 1995.