Backpressure Regulator/Valve (BPR): Back-pressure regulators control inlet pressure by balancing an adjustable spring force against the force of the inlet pressure. The spring force is adjusted by turning the stem/ handle, which sets the desired inlet pressure. When the force caused by the inlet pressure rises above the force of the spring, the regulator opens until the spring force and inlet pressure are balanced again.
The function of a backpressure regulator is to limit and accurately control the upstream pressure of a gas or liquid (from a pump, tank, wellhead control, metering systems, analyzer systems, paint spray lines, etc.) and is much more accurate and reliable than a relief valve.