High Integrity Protective System (HIPS)
From a design standpoint, HIPS do not differ greatly from other trip systems
The systems are composed of field input devices, a logic solver, and final elements. The sensors may be on-off switches or transmitters. Discreet switches are less expensive compared to transmitters, but the disadvantage is loss of “live” recording of the process variable concerned. Separate taps are used to avoid common failure for example due to plugging of the line.
Advantages And Disadvantages of Using HIPS
Industry is increasingly moving towards utilizing HIPS to reduce flare loading. They are becoming the option of choice to help alleviate the need to replace major portions of the flare system in existing facilities when adding new equipment or units. If the header and flare system must be enlarged, significant downtime is incurred for all of the units that discharge to that header.
The relatively low capital cost of HIPS compared to flare system piping upgrades and the ability to install HIPS without incurring significant additional downtime during a turnaround, makes these systems an extremely attractive option.
Another benefit is that the process unit will not flare as much as a process unit designed for full flare loading. In some areas of the world, this is becoming important as regulatory agencies place greater restrictions on flaring.
The main disadvantage of HIPS is these systems are more complex and require that many different components work as designed. The effectiveness of the system is highly dependent on the field design, device testing, and maintenance program.
The ability of the HIPS to adequately address over-pressure is limited by the knowledge and skill applied in the identification and definition of overpressure scenarios. When a PRV is not installed, the HIPS becomes the “last line of defense,” whose failure potentially results in rupture of the vessel or pipeline.