Pneumatic Pressure Control and Flow Control Valves
Pressure control is the control of a fluid’s force within a vessel. It is transmitted equally in all directions. Think of your automobile’s tire pressure. When the pressure in all four tires is set properly, they collectively exert enough force (power) within them to safely support your automobile.
Flow control is controlling the movement of pressure between two vessels, and it moves from the vessel with greater pressure to the vessel with lower pressure. When tire pressure is too high, the tire valve is opened to release pressure from the tire “flowing” to the atmosphere. When tire pressure is too low, the valve is opened to receive a greater pressure “flowing” from the air compressor.
Today, electronic sensor technology exists such that pressure and flow can be changed dynamically, in a closed-looped microprocessor-based system. A simple example is a service station tire pump, which allows you to set your desired tire pressure and automatically shuts off the pump when that pressure setting is achieved.
Pneumatic Flow Control Valves
All valves control flow. The industry term "flow control valve" refers to its ability to vary the flow of a fixed pressure to its output side. There are manually controlled and current (amperage) controlled valve types.
Manual flow control valves usually have a knurled adjustment knob or throttle. Once the desired flow is set, these valves remain in that flow setting until further adjusted.
Flow control valves (operated by current) are commonly referred to as proportional valves. As amperage is applied or varied to its solenoid operator, the output flow of the valve varies accordingly.
The primary advantage of these “proportional valves” is their ability to be used with a microprocessor-based programmable controller, particularly in closed-loop systems. In these systems, downstream sensors continuously provide feedback to the controller to change (or not) the current to the valve’s solenoid operator.
Other names for flow control valves include:
- Needle valves
- Proportional valves
- Meter out valves
Pneumatic Pressure Control Valves
Pneumatic pressure control valves are commonly called pressure regulators and come in manual and electronic models, similar to flow control valves. Pressure regulators are designed to respond and maintain a controlled downstream pressure setting when a pressure loss or surge occurs. Each pressure regulator has a restriction, load and reference element to respond to pressure and maintain the desired output.
They are only used in closed-loop systems since they require downstream feedback to maintain a set pressure. Pressure regulators are offered with either piston or diaphragm-type valves. Piston types are better suited to rugged applications that require some accuracy and durability, while diaphragms provide precision control.