(47u) Sil Determination of High Integrity Pressure Protection System (HIPPS)

High Integrity Pressure Protection Systems (HIPPS) are Safety Instrumented Systems (SIS) implemented to address overpressure scenarios in lieu of a pressure relief valve (PRV). HIPPS essentially replaces the PRV for those scenarios that the SIS is designed to prevent. HIPPS applications are generally pipeline and pressure vessel overpressure protection.

The fourth edition of API 521 allows credit for a favorable response of the instrumented systems that prevent over-pressure and/or over-temperature. The recommended practice refers to these systems as high integrity protection systems and states that they should be at least as reliable as a pressure relief device.

The Pertamina Hulu Energy Offshore North West Java (PHE ONWJ) intents to install new YYA NUI (Normally Unmanned Installation) platform will be sent to the existing unmanned KLB platform via 12 inch three phase pipeline. The KLB platform has fix flare system and has limited space to increase its capacity due to the additional production from the YYA.

The overpressure scenario has been identified in the HAZOP study and need to be mitigated by either release the pressure through PSV to flare or installing another layer of protection to prevent overpressure scenario. In this case of the releasing pressure to existing KLB flare is not sufficient to handle the gas relief from YYA wells. Therefore HIPPS was selected to replace the PSV in preventing the potential overpressure at the KLB.

The LOPA workshop was conducted for SIL determination of the HIPPS system and attended by discipline engineer and operator to identify initiating cause, the protection layer and severity level. It was identified 5 initiating events related to the overpressure scenario above. The independent protection layer also identified the existing pressure switch high which can be assumed to have a credit for SIL 0. The consequences or severity level for safety, environment, cost and business image was determined as impact of the scenario happened. The modifier factor was also included for occupancy (NUI) while the ignition probability was not credited as the ultimate consequence ultimate scenario is rupture.

The assessment of SIL determination resulted IL target IL1 for safety, IL2 for environment and IL0 for commercial. From this LOPA method, maximum IL2 with PFD 6.1E-03 was selected for IL target. The next step is to design HIPPS and verify the SIL level after gathering data of PFD from the vendor.