An incident involving PLASTIC sulphuric acid piping at a gas plant. Two workers were operating valves on a 1″ polyvinyl chloride (PVC) drain line so they could transfer sulphuric acid from a storage tank. They were
- following a written procedure,
- had held a tailgate meeting to discuss the hazards and emergency procedures, and
- had all necessary personal protective equipment for the task.
The first worker was wearing the REQUIRED FULL CHEMICAL SUIT when operating the drain valves. Although access to the drain valves was limited, the suit did not impede his ability to conduct the task. During the process, inadvertent contact with a 60-mm-long PVC pipe nipple between the two (2) drain valves caused the nipple to fail, resulting in pressurized sulphuric acid spraying in the workers’ direction.
Both workers received aid from the plant’s emergency response personnel, utilizing the on-site emergency chemical showers.
The worker who was operating the drain valves below the storage tank was airlifted to the hospital and released the following day; the second worker suffered minor exposure injuries and was treated on site.
A subsequent investigation of the accident revealed:
- There were no records indicating the age, installation date, or repair history of the failed component.
- The final drain valve had a plug installed which appeared to have been subjected to repeated removal and reinstallation, whereas this component should have been replaced every time it was removed.
- The fracture appearance did not show signs of plastic deformation; a circumferential crack in the PVC nipple may have propagated and worsened over time.
- It was undetermined whether the effects of weather or ultraviolet light exposure on the PVC material were contributing factors.
This incident could have resulted in much more severe consequences if the personnel involved had not been adequately trained, had not followed plant procedures, were not using the required protective equipment, or had not reviewed emergency procedures prior to starting the task.
The incident serves as a sound reminder of the dangerous nature of the equipment found at plant sites, and of some of the substances involved –pressure equipment operators cannot become complacent, even when conducting seemingly routine tasks. Owners are also encouraged to periodically verify that all of their piping (including non-metallic piping) is adequate for the intended purpose, and to keep careful records of fabrication and maintenance.
Source: https://www.absa.ca/media/1691/the_pressure_news_2017-v22-iss3_september2.pdf