Choosing HIPS over PRV - It's More Than Risk Reduction

The use of the term “High Integrity Protective System” or HIPS has changed from 2000 when this author won the 2000 best paper award from the Loss Prevention Symposium on the subject. Initially, the term applied to some very specific applications of safety instrumented systems (SIS). Now, it seems to have become a catchall term for any SIS implemented to minimize the need to relieve excess pressure through a pressure relief valve (PRV). It is unlikely that this trend will cease, as more facilities use the equivalent risk reduction argument to justify relying on instrumentation and controls for overpressure protection in lieu of a conventionally designed PRV and disposal system.

HIPS are more complex systems than PRVs, but the equivalent risk reduction argument is a strong one. A HIPS can provide protection similar to or better than a pressure relief device for loss events caused by process upsets. Actually achieving similar risk reduction in the process operating environment takes significant effort beyond rigorous HIPS design and management, which was discussed in the 2000 paper and many others over the last 17 years. This paper presents implementation challenges that must be understood before a HIPS can be expected to provide overpressure protection without causing potentially dangerous side effects:

• Process Design
• Functional Specification
• Design Calculations
• Engineering
• Installation and Operation
• Maintenance