How to Select the Perfect Pressure Regulator

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Set Pressure / Set Flow: Initial regulator outlet conditions

Drop (Droop): Decrease in Outlet Pressure with increasing Flow

Cv: Flow capacity at wide open position

Operating Range: Optimal flow range, linear portion of the curve

System temperature

Processes can reach extremes in temperatures, especially due to changes in pressure. Your choice of regulators must withstand the ranges of temperatures that occur in typical operating conditions. System temperature and media determine the most suitable seal material option for your application. If the system operating temperature exceeds the limit of seal materials ratings, it can cause leaks internally and/or externally, which create safety hazards and significant downtimes.

System media

The type of system media (gas, liquid, or steam) along with temperature will affect the longevity of the regulator you select. Surface treatments such as electropolish and passivation, in addition, to surface finish, can enhance corrosion resistance and cleanliness with stainless steel regulators. Another consideration is seal materials. Metal regulators are especially affected since they are typically designed with plastic or rubber seals. Knowing media compatibility will influence the decision on the best seal material choice. Media that is not compatible can cause faster deterioration and decrease the life cycle, making the material compatibility between your regulator and your system media a key consideration.

End connections

End connection types are usually synonymous with the industry served and the means to provide the level of leak integrity needed. For example, ultra-high purity regulators used for semiconductor processes commonly have welded face-seal or tube-end connections due to more stringent leak rates. On the other hand, regulators for oil and gas industries commonly use National Pipe Thread Tapered (NPT) connections.

Tied vs. non-tied diaphragm

Tied diaphragm regulators physically connect the poppet to the diaphragm, resulting in a mechanically assisted positive shut-off acting as a safety shut-off feature in the event there is leakage across the seal. Tied diaphragms allow the spring to be removed from the wetted area, making the operation far cleaner and reducing particles that could be generated during operations. Therefore, tied diaphragms are preferred in ultra-high purity (UHP) applications. In applications with hazardous and corrosive media, tied diaphragms are considered an added safety feature. However, a tied diaphragm costs more due to the increased number of components.

Contact us to discuss your requirements of pneumatic pressure regulator valve. Our experienced sales team can help you identify the options that best suit your needs.

A pressure reducing regulator is commonly used to manually control pressure of a liquid, gas or steam. Choosing the right regulator for your application can be challenging. There are 5 variables required to size any pressure regulator and properly calculate Cv: upstream pressure, downstream pressure, flow range, temperature and fluid type. We define each variable and talk about why it&#;s crucial to sizing a pressure regulator.    

**Please note: Cv is a coefficient of flow for valve sizing. It&#;s used to quantify valve flow performance and can vary with both size and style of the valve or regulator. Once you calculate the required Cv range, you&#;ll know the valve or regulator is sized correctly to handle the actual flow.

1. UPSTREAM PRESSURE

Supply pressure or Inlet pressure. This is the pressure upstream of the regulator. This pressure could be coming off of a main header at 100 psi. If it is a higher pressure, such as 1,000 psi, and your goal is to regulate a much lower pressure, less than 100 psi, then a second regulator may be required to knock down the pressure in two stages: one high pressure regulator and one low pressure regulator. 

2. DOWNSTREAM PRESSURE

Outlet or Control Pressure set point or range. This is the pressure downstream of the pressure reducing regulator. The pressure levels are what you are attempting to control. It could be a specific pressure point, like 30 psi, or a range of 5 to 20 psi. The difference between upstream and downstream pressure is called a &#;pressure drop&#; or &#;pressure differential&#;. 

3. FLOW RANGE (minimum, maximum and normal)

It&#;s a good idea to size the regulator at a minimum of 3 separate points in order to get a range of flow requirement. This gives you a safety factor, so the regulator is not over or under-sized. 

4. TEMPERATURE (minimum and maximum)

Temperature can affect the required Cv. Note that temperature does not affect Cv nearly as much as pressure and flow. 

5. FLUID TYPE

Determine what fluid is going through the regulator. Is it liquid, gas or steam? What are its properties? Understand that sizing formulas are different for each type of fluid. For example, the formula for critical pressure drop is different than non-critical pressure drop for gases. For steam, you must know whether it&#;s saturated steam or super heated (higher temperature).

A regulator cannot be accurately sized without knowing these 5 variables. Understand that changing any of the above values could get you into a completely different regulator.

After sizing, the next step is to select your regulator by identifying the following criteria:

• Line size
• Material compatibility
• Connection type
• Accuracy required
• Shutoff capability (metal seated vs. resilient seated)
• Direct-operated vs. Pilot-operated

Do you have a question about sizing or selecting a pressure regulator or other type of valve for your application? Ask us about it! Our dedicated team of valve specialists look forward to hearing from you!

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