An Equilibar back pressure regulator can be used as a control valve to achieve a very wide 100:1 flow rate range.
Traditional flow control valves have a very limited range of controllable flow rates. The ratio of the maximum flow rate to the minimum controllable flow rate, called the turn down ratio, is often limited to 15:1 or even 10:1 depending on the type of flow control valve. A flow control valve with a turn down ratio of 15:1 that had a maximum flow rate of 30 gallons per minute (GPM) could not be counted on to reliably control flow rates below 2 GPM.
This video demonstrates how an Equilibar precision back pressure regulator can be used to directly replace a traditional control valve and achieve a flow turn down ratio up to 100:1 In the video the Equilibar back pressure regulator is used to precisely control the differential pressure across a flow restriction (an adjustable needle valve was used as the restriction in the video). flow is directly proportional to the square root of the pressure drop across this restriction. By establishing and precisely maintaining the correct differential pressure the flow rate through the system is controlled. The pressure controlled by the Equilibar back pressure regulator is accurately set with an electronic air pilot pressure regulator. An electronic flow transmitter is used to monitor the flow rate and provides an electronic feedback signal to a PID controller. The PID controller uses an electronic command signal to modulate the set point pressure of the Equilibar back pressure regulator. In this fashion the PID controller will modulate the differential pressure until the system flow rate as seen on the flow transmitter matches the flow rate that has been requested. Closed loop electronic control of flow rate is achieved. The Equilibar back pressure regulator is able to control flow over a wide range because it has a much higher resolution than traditional back pressure regulator designs. The Equilibar uses a flexible diaphragm as the only moving part. The diaphragm acts as both the pressure sensing element and acts as the main flow control valve by directly sealing against a field on parallel orifices. Other back pressure regulator designs typically do not offer suitable resolution.