HIPPS (High Integrity Pressure Protection Systems) provide protection to pressurized equipment from overpressure and rupture. Traditionally, rupture disks and safety relief valves were used but they have drawbacks. Rupture disks or relief valves discharging can cause environmental and personnel issues. It can also be difficult to determine the root cause of bursting. HIPPS addresses these issues by using fast-acting shutoff valves to close the line within seconds if overpressure occurs, preventing it from traveling downstream. Understanding HIPPS requires knowledge of Safety Instrumented Systems.

1. HIPPS-High Integrity Pressure Protection Systems
Introduction
By now if you have been working in the process industries (like chemicals,
oil & gas, petrochemicals and so on) for some time, you must have come
across the term HIPPS. What is it? It is an acronym for High Integrity
Pressure Protection Systems. These protection systems can be considered
to a special subset of Safety Instrumented Systems (learn more about
them here), that are meant to provide protection to pressurized
equipment (tanks, pipelines and so on) against overpressure and
consequent rupture.
Traditional Pressure Protection for equipment
Traditionally pressure protection for equipment was implemented using
two main techniques, rupture disks (also known as burst disks) and safety
relief valves. The burst disk, as the name suggests, is a contraption that
bursts under overpressure conditions to release the pressure inside the
equipment on which it is mounted and protect the equipment itself from
bursting. Therefore the burst disk always bursts at a slightly lower
pressure than the equipment's design pressure. Conceptually, it is similar
to a fuse that blows in an electrical circuit if excess current flows in the
circuit. The fuse gets destroyed but the other expensive and/or critical
electrical/electronic devices in the circuit are protected.
In case of mechanical safety relief valves, excess pressure in the
equipment lifts the valve and the excess pressure is relieved. As soon as
the excess pressure is vented, the valve shuts and maintains the pressure
inside the equipment. The advantage is that the safety relief valve is not
a "single-use" item, it can operate even several times in a hour, in case a
process upset results in excess pressure conditions in the equipment.
Conceptually it is similar to a circuit breaker which trips in case of
overcurrent, but can be used again and again in the same circuit to
protect critical and/or expensive electrical/electronic devices.
The traditional methods have worked for a number of years successfully.
In fact most plants today use MAINLY the above two methods of pressure
protection for equipment. Of course many plants do have pressure
transmitters and pressure switches to generate alarms in case of excess
pressures, but they are mainly meant for operator intervention and not
for automatic pressure relief.
Drawbacks of the present mechanical systems
Despite the fact that these traditional methods form the bulk of
overpressure protection, does not mean that that users are very happy
with them. There are several drawbacks in these methods; these are
given below:

2. Modifications in existing plants-lack of flare capacity
Many times, expansion or debottlenecking projects in plants do not
correctly estimate the additional load on flare systems, due to increased
throughput. This point only comes up during the HAZOP and other safety
and environmental studies. The increased investment in flare headers and
the shutdowns that may be necessary to increase the flare capacity are
simply not possible in today's tight economic situations. This is where
HIPPS is an alternative. Instead of merely venting the gases to relieve
overpressure, a fast acting HIPPS simply shuts down the inlet valves to
prevent overpressure from building up in the first place.
Environmental Release & Personnel Injury
If a burst disk or relief valve opens, it may discharge environmentally
unfriendly substances into the surrounding air, leading to consequential
problems of spillage, pollution, environmental damage or personnel
injury. In many older plants, many processes are still operated manually
which means more humans are working around pressure vessels. Any
release of flammable or toxic contents into the surroundings may also
endanger the personnel working in the area.
Fire and Explosion
If the released material is an explosive material then releasing large
quantities of it through relieving devices can increase the risk of fire or
explosion. It may also endanger the personnel who may rush to that area
to replace the burst disk.
Replacement problems
When a burst disk operates, the equipment of part of the pipeline gets
shutdown. Replacing it and starting the plant again entails a lot of use of
resources. Sometimes, it is challenging to find out why a burst disk burst
at a particular time and place. Nowadays there is an arrangement where
when a burst disk bursts, a pressure switch senses the bursting and
generates an alarm in the control room to alert the operator. Even then, it
may be difficult to find the root cause of the bursting. It may be due to a
genuine overpressure condition, or it may be that the particular burst disk
operated a slightly lower pressure than it was designed to-it is difficult to
pinpoint.
The HIPPS solution
To avoid all these problems, users today are now actively accepting the
HIPPS alternative. A typical HIPPS is shown below. In case of
overpressure in the line, the quick shutoff valves close the line in a matter

3. of seconds, preventing the overpressure condition from travelling further
downstream.
Where do I Know more
To understand and implement HIPPS, requires an understanding of Safety
Instrumented Systems. Download the Safety Instrumented Systems
course now to easily understand all about Safety Instrumented Systems.