Due to environmental constraints, safety and cost saving, HIPPS has gained popularity over the last years as the last line of defense, replacing pressure safety valves (PSV), blow down and flare systems. HIPPS is an acronym for High Integrity Pressure Protection System, which is a specific application of Safety Instrumented System (SIS). The function of a HIPPS is to protect downstream equipment against overpressure or upset conditions coming from the upstream.

A High Integrity Pressure Protection System is a complete functional loop consisting of:  
     •   The sensors, (or initiators) that detect the
          high pressure
     •   The logic solver, which processes the input from
          the sensors to an output to the final element

It is designed in order to reach the desired fail-safe condition for the process according to the following standards:
     •   IEC 61508: ”Functional Safety of Electrical/Electronic/Programmable Electronic Safety Related
         System”
     •   IEC 61511: ”Functional Safety: safety instrumented systems for the process industry sector”
     •   ANSI/ISA S84.01, ”Application of Safety Instrumented Systems for the Process Industries”

The standards are performance-based with the safety integrity level (SIL) as the primary performance Measurement. The SIL must be assigned by the user based on the risk reduction necessary to achieve the user’s risk tolerance.

It is the user’s responsibility to ensure consistent and appropriate SIL assignments by establishing a risk management philosophy and risk tolerance. The risk reduction provided by the HIPPS is equivalent to the probability of failure on Demand (PFD) attributable to all of the HIPPS devices from the sensor through the logic solver and final elements.