Subsea HIPPS

HIPPS is an instrumented safety system that is designed and built in accordance with the IEC 61508 and IEC 61511 standards. Additionally API RP 17O – Recommended Practice for Subsea HIPPS - provides guidelines for using the IEC standards in subsea systems. These international standards refer to safety functions (SF) and Safety Instrumented systems (SIS) when discussing a solution to protect equipment, personnel and environment. A system that closes the source of over-pressure within 2 seconds with a determined reliability level is usually identified as a HIPPS.

A subsea HIPPS is a complete functional loop consisting of:

• The initiators that detect the high pressure.
• A logic solver, which processes the input from the initiators to an output to the final element.
• The final elements, that actually perform the corrective action in the field by bringing the process to a safe state. The final element consists of a valve and fail safe actuator and possibly solenoids.

Safety loop

In order to provide a complete HIPPS system Mokveld works together with reputable suppliers of subsea initiators, voting logic, instrumentation pods and subsea skids. The complete HIPPS module will be certified to the required safety integrity level.

Third parties, like the German TÜV and Atomic Energy Agency, have validated the Mokveld database of installations and the derived reliability data. Failure rates for both clean and unclean fluids are available for 2 seconds stroking time applications. Mokveld’s vast experience in fast stroking final elements totals over of 35 000 operational years (with more than 2500 valves). The Mokveld final elements are therefore proven-in-use for high reliability safety applications in natural gas and multiphase hydrocarbons. 

The certified Mokveld failure rate for the final element (being the valve + actuator) for a failure to deliver a full stroke in 2 seconds for applications in untreated hydrocarbons is: λd = 1,0 x 10-4 / year. The failure rate for a single Mokveld hydraulic mechanical initiator is: λd = 9,7 x 10-4 / year. This data enables Mokveld to supply a HIPPS to suit SIL 3 or even SIL 4 with a proof test interval of 1 year or a system fully in accordance with EN 12186 or EN 14382.

The Mokveld final elements do not require additional electronic systems, like partial stroke testing devices, to meet SIL 3 with a 1 year test interval. A separate technical datasheet on this subject is available.

Mokveld engineers can provide support in an early phase of the project. We can assist in defining suitable HIPPS architecture, fault tree analysis, determining the pressure rise in the protected volume and the required stroking times and set points of the entire system.

HIPPS are critical elements in a process loop. Malfunction or failure of a HIPPS can seriously affect plant operation, the environment and personnel. The design of a HIPPS should be based on sound technical and economical arguments and long-term perspectives. Selecting a Mokveld HIPPS with proven reliable performance will ensure a safe and reliable operation of your plant.