Program Ranks Musculoskeletal Risk of Operating Valves in Process Industries Source: Journal of Petroleum Technology | 7 August 2014
Every process plant presents a high number and diversity of valves that control the flow of feedstock, products, and service liquids and gases. A comprehensive program was developed for a major US refinery to assess the musculoskeletal risk associated with manually operated valves then to rank each valve according to the risk each poses to plant operators and maintenance technicians. Valve repair and replacement is expensive, so the cost-effective approach was to assess only those valves that are critical to plant operation.
Process plants contain a large number of process valves with a wide diversity of designs that control the flow of a wide range of fluids. The ergonomic issues associated with the design, operation, and maintenance of valves include
- Physical stress to open and close them
- Potential for injuries and subsequent related costs
- Lack of access to process-critical valves
- Difficulty of removing and replacing them
- Potential for process upsets when valves cannot be operated in the time required
As a result of injuries suffered while operating valves, a major US petroleum-refinery company initiated a program to identify high-risk valves and to modify them to reduce the operating risk of injury.
Fig. 1—Systematic approach to working with valves in process operations.
A model, illustrated in Fig. 1, was developed to create a systematic approach to identify the valve issues in a process plant, analyze the issues, prioritize the valves that need attention, implement a solution, and measure the results. The approach can be modified to reflect the unique character of the plant that implements the program.
The objectives of the study were to
- Develop a valve-risk-assessment program unique to the process plant based on the plant’s human-factors engineering-design standards and the valve-assessment model.
- Assist site personnel in identifying the process-significant valves and surveying them to determine the top candidates for repair or replacement.
Process-significant valves were those that met the following definitions:
- Frequently operated—valves that are operated more than four times per year
- Operated in an emergency—emergency block valves, emergency isolation valves, battery-limit valves, depressuring valves, and dump valves
- Manual, gear-operated valves
- Large valves—valves with valve wheels ≥24 in. in diameter
- Manual block valves and bypass valves around control valves
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