Pressure Relief Valves and
Back Pressure Regulators

Pressure relief valves and back pressure regulators work in a similar way, but serve different functions.

A pressure relief valve is traditionally defined as a device used to limit or control the pressure in a process or vessel during an unusual circumstance such as equipment failure or fire. 

A back pressure regulator is  a type of valve that controls flow in order to maintain the upstream, or inlet pressure (see definition).

The emphasis for a Pressure relief valve is for a device which is normally closed, but can open to relieve any excess pressure above the desired set-point.  The device is normally expected to close (re-seat) after the excess pressure subsides.  In many applications, this function is required to maintain the safety of a process ("Safety Relief Valve") and is required by pressure vessel codes and regulations.

A rupture disc can be used as a substitute for a pressure relief valve. However, because it cannot re-seat, it has to be replaced after each use.

A back pressure regulator (BPR) performs a similar function, but the primary emphasis in on flow control in order to control process pressure.  A process pressure approaches and exceeds the set-point pressure, the BPR gradually opens up to control its inlet pressure and prevent over-pressure.

Equilibar offers high precision back pressure regulators for a wide range of demanding applications.

Uses for Back Pressure Regulator

BPRs as a rule are not marketed or approved to function as the formal safety protection for a vessel (i.e. as a safety relief valve).  However, there are also many other situations where a back pressure regulator can be used to control process pressure.

In the example schematic below, a precision back pressure regulator is used as the primary method of controlling vessel pressure, while a rupture disc is installed as the formal safety protection. The high performance back pressure regulator allows operation closer to the relief valve setting, while avoiding the risk of inadvertent failure.

Equilibar precision

The Equilibar back pressure regulator uses a unique technology to provide stable pressure control over widely varying flow rates.  It uses a dome-loaded technology where an air signal is used to communicate the set-point to the Equilibar (see how it works). This is highly desirable for computer automated applications.

Learn details about the Equilibar high resolution back pressure regulator and how it works.

Contact our engineers to discuss whether your process control application could benefit from Equilibar precision.