Understanding pressure controller types: pressure reducing regulators and controllers, back pressure controllers, and closed volume pressure controllers
There are many different methods to and reasons for controlling pressures. Here we present a brief overview of these methods and the intended goals of these methods.
Pressure Reducing Regulators
The primary goal of a pressure reducing regulator is to control the outlet pressure of a gas source to match the desired pressure demand of the user. Pressure reducing regulators come in many shapes sizes and technologies. Any control valve is essentially a pressure reducing regulator, as opening or closing a valve inherently allows for greater or lower output pressures respectively.
Mechanical Single stage, and mechanical two stage regulators are common forms of pressure reducing regulators commonly used on gas bottles. Needle valves, and single valve electronic pressure controllers are also examples of pressure reducing regulators.
Some methods of pressure reducing regulators involve input and output pressure measurement so that manual or electronic setpoints for outputs can be set. Other methods simply create a more or less restricted output path.
Common applications for pressure reducing regulators include gas mixing, welding, leak checking, automotive paint, and fuel cell testing.
Back Pressure Regulators
While pressure reducing regulators reduce a higher supply pressure at the inlet down to a regulated lower pressure at the outlet, back pressure regulators work the opposite way. A Back Pressure regulator’s primary function is to control the restriction on the outlet of a system in order to control pressures that build or release upstream of the installation point of the back pressure regulator.
When gas pressure exceeds the intended set point the back pressure regulator opens more to relieve the excess pressure. Back pressure regulators similarly require a means of measuring upstream pressure, and reducing or increasing the restriction at the outlet of that system.
Common applications for back pressure regulation include compressor testing and control, chromatography and analysis, chemical engineering, pressure relief and safety applications.
Closed Volume Pressure Controllers
Both pressure reducing regulators and back pressure regulators are typically single valve systems, designed to control pressure in flowing systems. Sometimes pressure control of closed volumes is required, and a regulator must maintain a pressure in a non-flowing system. Most closed volume pressure controllers use two proportional valves (or a proportional valve on the inlet and a digital valve on the outlet) to precisely control the pressure of gases within closed or dead-ended volumes. An inlet valve allows pressure into the system while an exhaust valve relieves pressure.
Many dome loaded pressure regulators use closed volume pressure controllers as a means of controlling their internal mechanical setpoints.
Common applications for closed volume pressure control include chemical dispensing, micro-fluidic control, and sensor testing.