Human Factors in Refinery and An Operator in a Safety Instrumented Function
Buncefield was a major process safety event in the UK arising from the overflow of gasoline from a tank in a terminal leading to a vapour cloud explosion. No-one died but the cost of the incident was estimated at £1 billion. The follow-up report recommended that all gasoline tanks be fitted with a high integrity overfill protection system that complied with the international standard IEC-61511, also that the overfill prevention system should preferably be automatic. Automatic shut-down would be fully acceptable for a gasoline blending operation but dangerous if false alarms led to blocking the rundown from major refinery units.
IEC-61511 allows for operators to be used for SIL-1 systems but gives no further guidance on necessary characteristics.
A working group of UKPIA (UK Petroleum Industry Association) members and the consultants Human Reliability Associates developed a checklist defining the standards of hardware and operator performance needed to be compliant with IEC-61511, EEMUA-190 and UK-HSE best practice guidance. The team also developed a second checklist defining excellence in process safety for tank operations to give guidance to operators on how to further improve.
Key to the checklist was recognition of the human factors that can affect an operator and possibly prevent the correct outcome. The checklist defines requirements of staff availability, ease of alarm detection and response and site culture. For example is the operator to be able to resolve the issues alone (not needing a colleague on a bicycle to go and close a valve), not already overloaded with alarms, has a checklist to follow giving clear procedures, trained in the procedures and the site culture encourages operators to respond by shutting down the site, if needed.
The work was trailed in two refineries with teams of operators and is now being implemented in the Safety Case (Seveso) Reports of sites.
Mark Manton, PhD, joined ABS Group after 25 years' experience working for Shell in a variety of assignments, including Process Safety Manager for five years at Shell's Stanlow refinery (second largest in the UK). During that time was part of, and Chaired for half the time, the UK Petroleum Industry Association's Process Safety Leadership Network, the main interface between the sector and the Health and Safety Executive and Environment Agency. He worked on and/or led a number of sector-wide working groups on Human Factors, Buncefield follow-up and environmental risk assessments. He has extensive experience working with the UK HSE and demonstrating industrial practices in refineries are compliant with the ALARP principle.
About ABS Group
ABS Group of Companies, Inc. (www.abs-group.com), through its operating subsidiaries, provides technical advisory and certification services to support the safety and reliability of high-performance assets and operations in the oil, gas and chemical, power generation, marine, offshore and government sectors, among others. Headquartered in Houston, Texas, ABS Group operates with more than 1,500 professionals in over 30 countries. ABS Group is a subsidiary of ABS, a leading marine and offshore classification society.