The piping concerned (DN 80) connects a 100 m³ air tank storing 32% HCl to a 17 m³ intermediate storage tank. The aerial piping – 3 m high – is equipped with shut-off valves.

An acid loading operator in a chemical plant observed HCl on the ground in the morning, caused by acid dripping from a valve on a transfer line. At around 3 p.m., 2 maintenance technicians drained the piping, allowing 1 m³ of product to spill out onto the loading/unloading area. The drivers located nearby were affected by the irritating vapours released. As the area was built on a retaining system, the products were channelled to the plant’s treatment station.

The investigation conducted by the operator revealed that the maintenance technicians had not followed the operating procedures. The intervention permit on the system concerned was not signed by the line manager, the operation’s risk analysis was not completed on the intervention form, the recommended PPE was not worn, and no means were set up to collect the acids or mark the area. The maintenance technicians were penalised and the subcontractor in charge of the loading/unloading station was fired.

Actions were initiated to raise the awareness of plant and group personnel regarding this event. The procedures for issuing work permits and performing maintenance operations were reviewed. Refresher training for subcontracted personnel was initiated with regard to the proper use of the intervention form.

Inspectors of Classified Facilities requested that the operator include, with its intervention form, a description of the safety measures specific to the equipment and the product concerned. A standard phrase, reminding the production crews to properly secure the equipment, without specifying the nature of the measures to be taken, is inappropriate.