HIPPS (High-Integrity Pressure Protection System) is a part of the Safety Instrumented System (SIS) & designed as the “last line of defence” preventing overpressure, loss of containment & fugitive emissions. A key driver reducing or supplementing the number of existing pressure relief systems with HIPPS has been the annual operating expense (OPEX) of testing relief valves. Design and implementing of HIPPS is often more complex in that they require the successful functioning of multiple devices to achieve the same performance as a single pressure relief, thus the need for a complete solution.
Carsten opened describing the increased demand for HIPPS applications. It’s driven by environmental concerns, regulatory directives to reduce gas flaring, and the desire to reduce operating expenses (OPEX) caused by the annual testing of relief valves.A HIPPS loop includes two Virgo ball valves with Bettis actuators, ASCO solenoid valves, and Fisher DVC controllers. Three Rosemount pressure transmitters measure the pressure in a two-out-of-three (2oo3) voting scheme. The safety instrumented function is completed with the DeltaV SIS logic solver.
Carsten described the challenges process manufacturers face. These challenges occur in many phases–analyze, design, performance, environment, technology, and contract management. In the analyze phase, defining the safety requirement specifications and ensuring that they are followed is paramount.
The design phase, consider random as well as systematic integrity to meet the safety integrity level (SIL) requirements for the loop. In the performance phase, monitoring and testing is performed with the HIPPS in service. The answer to systematic failures is the IEC 61511 safety lifecycle to manage all of the activities including testing.
Emanuele described challenges on a product level. Closing speed is a critical factor for the valve to meet the requirements of the safety loop. It must be reliable and repeatable. The valve must handle the torque and shear force requirements and be sized for the highest load situation.
For the actuator, it must manage the closure speed and position of the valve. Overshooting the final position can damage the integrity of the valve.
All part of the HIPPS safety instrumented function require diagnostic coverage to test performance while the shutdown valves remain online. Partial stroke testing can be initiated periodically from the DeltaV SIS logic solver to test the loop. Solenoids are tested with 50-100msec pulses to begin the partial stroke test without closing the valve.
Carsten showed the logic solver panel on integrated HIPPS solution that can reside either in a control room or directly on a skid where the shutdown valves are located. For the Rosemount pressure transmitters, a high-integrity manifold is included for testing the pressure transmitters.
As a single supplier, all parts of the safety lifecycle can be provided with the HIPPS, including calibration, test, and inspection plans. Compliance reports are provided.