Let’s start with the basics.
What is a pressure regulator?
A pressure regulator is a normally-open valve used to regulate or reduce undesirable, high upstream pressure. The pressure regulator must be installed at the START of a system, before any pressure-sensitive equipment.
The valve is held open by springs, and a screw that sets spring force. When outlet pressure exceeds the setpoint, the valve will close. When the valve closes, pressure is reduced downstream.
What is a back pressure regulator?
A back pressure regulator is a normally-closed valve used as an obstruction to reduce flow and maintain pressure upstream. Unlike the pressure regulator, a back pressure regulating valve must be installed at the END of a piping system.
Back pressure regulators work similar to relief valves, only the emphasis in on steady-state pressure control instead of on/off pressure protection.
The valve is held closed by a similar spring and screw mechanism as a pressure regulator. When flow is present, the sensing diaphragm transmits inlet pressure to the spring, pushing the valve open when pressure exceeds the spring setting.
Once the back pressure on the inlet side is reduced, the valve reverts back to its normal, closed position. Pressure is maintained upstream by varying the flow through the valve as inlet pressure changes.
So, when should I use what?
Let’s say you need to install a regulator at the end of a return line, just before a tank. When pressure becomes too high, you want the valve to dump the process into the tank, maintaining pressure upstream. Which regulator do you use?
Many people make the mistake of installing a pressure regulator in this scenario. With a pressure regulator, the valve will remain open, allowing flow to continue straight into the tank without having maintained upstream pressure.
The correct instrument in this scenario would be a back pressure regulator, as it affects what happens upstream of the valve.
A back pressure regulator will remain closed, preventing flow from entering the tank unless necessary to relieve spikes in upstream pressure. It will ensure all equipment before the valve maintain the right pressure for the process.
If you need a regulator to benefit what comes downstream to the valve, a pressure regulator would be the instrument to use. Placed at the beginning of a system, a pressure regulator will ensure safe downstream pressure for your process.
Pressure regulators are commonly used in gas grills to regulate propane, heating furnaces to regulate natural gases, medical equipment to regulate oxygen and anesthesia, pneumatic automation systems to regulate compressed air, or engines to regulate fuel.
When to use both
Both pressure and back pressure regulators can be used in balancing a system. When working together, a pressure regulator at the beginning of a process, and back pressure regulator at the end, can ensure balanced pressure throughout.
Of course, every system is different, so don’t hesitate to ask for help. Our factory-trained sales team is available to answer any and all of your pressure and back pressure regulator questions.
For more information visit our www.lesman.com or give us a call at 800-953-7626.
Lesman is the premiere stocking representative for process valving, controls, and measurement instrumentation, serving customers in Illinois, Indiana, Wisconsin, Eastern Missouri, Eastern Iowa, and Michigan’s Upper Peninsula.