When outdoor air temperatures drop, it is important for process plants to be prepared for safety challenges posed by cold weather. Low temperatures may affect piping, other equipment, and instrumentation. Cold weather vulnerabilities may result in process safety incidents.
The US Chemical Safety Board’s (CSB’s) Safety Digest, Preparing Equipment and Instrumentation for Cold Weather Operations, addresses this topic.
Water freezing and expanding can crack or break piping, rupture or damage process equipment, or cause instrumentation to fail. This damaged equipment may not become evident until the temperature rises, the ice thaws, and a leak develops. Dead legs are particularly susceptible to such failures.
Processes may be susceptible to the formation of a hydrate, where water combines chemically with a process material forming a solid that can block process piping or equipment. This can occur even above freezing temperatures.
The CSB Safety Digest summarizes three CSB investigations where ineffective freeze protection practices and programs were found to be causal to the incident:
- DuPont La Porte, Texas Chemical Facility Toxic Chemical Release, November 15, 2014, Four workers killed, three workers injured.
- Valero Refinery Propane Fire, February 16, 2007, Four workers injured; refinery evacuated and an extended shutdown.
- Bethlehem Steel Corporation Gas Condensate Fire, February 2, 2001, Two workers killed, four injured.
Companies should identify and control winterization hazards, and establish formal, written winterization programs. The CSB Safety Digest provides key safety lessons from these incidents, as well as additional freeze protection guidance and resources.
The Safety Digest is available at:
https://www.csb.gov/assets/1/17/csb_winterization_safety_digest.pdf?16379