Pneumatic Pressure Regulators

Pressure Regulators

How Pressure Regulators Work

In applications where the fluid medium's pressure must be kept within a given range, pressure regulators ensure consistency and guarantee optimal operations. Pressure regulators come in varying types, sizes, and designs, depending on their unique use cases. We’ve covered more about pressure regulators below.

Pressure Regulator
Figure 1: Tameson Pressure Regulator

What are Pressure Regulators and How Do They Work?

Are devices designed to control the pressure of gases and liquids by reducing a high input pressure into a steady low-pressure output. These regulators also stabilize fluctuating inlet pressure to ensure a controlled and constant output pressure. To understand how pressure regulators work, we need to look at the different elements of a pressure regulator and their role in pressure control. These basic elements are:

  • Pressure reducing element – an example is the spring-loaded poppet valve used to control the inlet and outlet pressure. This valve works for both high-pressure and low-pressure applications. The poppet valve comes with thermoplastic sealing in high-pressure applications, while in regular or low-pressure applications, it features elastomeric sealing. The seals prevent any fluid leakage as the valve opens and closes.
  • Sensing element – an example is a piston or diaphragm. For high accuracy applications, a diaphragm is used as a sensing element. The latter is made of thin material, e.g., elastomer that’s super sensitive to pressure changes. Diaphragms also have lower friction than pistons and provide a much higher sensing area. On the other hand, pistons are used for high-pressure applications with wider tolerances. And due to the friction between the regulator body and pinion sealing, pistons tend to be sluggish and less accurate.
  • Loading element – this works to exert some force on the sensing element, helping open the valve and letting the fluid medium flow from the inlet to the outlet. The outlet pressure obtained depends on the amount of the spring force.

Pressure Regulator Types

Pressure regulators come in two distinct types: The self-operated/ direct-operated and the pilot-operated types. Here’s a quick overview of the two:

Self-operated Regulators

Thanks to its self-contained nature, this pressure regulator type has a simplistic design. It’s suitable for low and medium pressure applications, typically below 0.07 bar and up to 35 bar. Since the self-operated regulator does not need an external sensing element at the output, its operation is more straightforward. The pressure from the flowing fluid media activates the diaphragm, directly controlling a spring-actuated valve. In other words, an increasing downstream pressure serves as the diaphragm, closing the valve plug with the help of the spring compression force. If the downstream pressure reduces, the spring force becomes greater than the force exerted on the diaphragm, opening the valve.

Pilot-operated Pressure Regulators

In applications with large fluctuations in inlet pressure or variations in flow rates, precise pressure control is required. Pilot-operated regulators are best used in these conditions, thanks to the wide range of pressures and accurate regulation.

There are two types of pilot-operated regulators: a single-stage regulator and a double-stage regulator. The former is designed for applications requiring small pressure reduction or those with minimal inlet fluctuations. Double-stage regulators are commonly used since they can handle large fluctuations in flow rates and inlet pressure. They consist of two stages. The first one has a spring-actuated pilot, which controls the pressure exerted on the diaphragm of the main regulating valve. When the pressure of the fluid medium on the spring-actuated pilot is low, theres no downstream flow.

But once the pressure increases, the spring compresses, and the pilot valve opens. This creates some pressure differential between the inlet and outlet of the main regulating valve. The pressure differential then actuates the main operating valve, causing an outflow of the fluid medium at reduced pressure. This is the second stage of the regulator. Unlike the single-stage pilot-operated regulators, this type is only used with clean fluids and gases as the small ports and passages can easily get clogged.

Pressure Regulator Use Cases

Pressure regulators perform other functions besides reducing input pressures and stabilizing large inlet fluctuations. An example is the backpressure regulator that maintains the desired input pressure by varying the flow of the fluid medium with respect to the change in input pressure. The other pressure regulators used for different applications include:

  • Pressure relief valve – used to restrict system pressure to a predetermined maximum value by diverting all or some fluid medium from the pump to the tank, i.e., when the set pressure is reached.
  • Pressure switching valves – these regulators are used for switching purposes in pneumatic logic systems and are either 2/2-way or 3/2-way.
  • Vacuum regulators – they are designed to maintain a constant vacuum at the inlet when a significantly higher vacuum is connected to the regulator outlet.

Some of the typical applications of pressure regulators are in domestic settings to control the amount of outlet gas in gas ovens, pressure cookers, home heating furnaces, etc. Pressure regulators are also used in compressed air applications (e.g., when inflating tires), aerospace industries for propulsion pressurant control, and welding and cutting applications.

Special thanks to Tameson for contributing this page