Direct Acting vs. Pilot Operated Pressure Reducing Regulators: Key Differences and Applications

Pressure Regulator Overview

A pressure reducing regulator (also referred to as pressure regulator) is a valve that automatically reduces a higher inlet pressure to a stable, lower outlet pressure. It regulates the flow of liquid or gas to maintain a set outlet pressure regardless of fluctuations in inlet pressure or flow demand.

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Direct Acting Pressure Reducing Regulators

Direct acting pressure reducing regulators have a simpler design and are typically used in low to medium flow and pressure applications.

• Working Principle: The basic mechanism consists of a spring-loaded diaphragm or piston that directly measures outlet pressure. When the outlet pressure exceeds the set point, the regulator valve closes proportionally to reduce the flow and maintain the desired pressure.
• Design Features:
  • Compact and simple design
  • Uses a single sensing element (diaphragm or piston) directly coupled to the valve
  • Typically has fewer moving parts, resulting in less maintenance
• Typical Applications: Small gas or liquid supply lines, laboratory equipment, pneumatic tools, household or light industrial systems
• Advantages: Fast response to pressure changes (fast modulation), economical and easy to maintain, suitable for moderate flow rates and pressure drops
• Disadvantages: Limited ability to handle large flow volumes or high pressure drops, less stable under flow fluctuations due to direct mechanical action, larger valves can be bulky and less efficient

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Pilot Operated Pressure Reducing Regulators

Pilot operated pressure reducing regulators (also called servo regulators) are designed for more demanding industrial applications, especially where high flow rates or stable pressure control under changing loads are critical.

• Principle of Operation: This regulator uses a pilot (a small regulator) that senses the outlet pressure and controls the main valve through a pilot line. The pilot controls the position of the main valve indirectly by modulating the pressure on one side of the main valve actuator (usually a diaphragm or piston), causing the valve to open or close to maintain the set pressure.
• Design Features:
  • More complex design with two valve components: pilot and main valve
  • Main valve is typically larger and can handle higher flow rates
  • Pilot provides accurate pressure feedback, improving stability
• Typical Applications: Large industrial gas distribution systems, high-pressure steam or air systems, hydraulics and process control in manufacturing plants, situations requiring precise control with highly variable flow or high pressure drop
• Advantages: Can handle very large flow rates, excellent control stability and accuracy even with sudden changes in demand, suitable for high pressure drops
• Disadvantages: More complex and expensive, requires more maintenance and periodic adjustment of the pilot valve, slower response time compared to direct acting regulators due to the indirect control mechanism

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Summary of Main Differences

Feature	Direct acting pressure reducing regulator	Pilot operated pressure reducing regulator
Working Mechanism	Valve directly actuated by diaphragm or piston	Main valve indirectly actuated by pilot regulator
Complexity	Simple design	More complex, with pilot and main valve
Capacity	Suitable for low to medium flow rates	Suitable for high flow rates and large pressure drops
Response Time	Fast response	Slower response due to indirect control
Pressure Stability	Moderate control under varying flow conditions	Excellent pressure stability under varying flow conditions
Typical Applications	Residential, small industrial, air tools	Large industrial processes, gas distribution, steam systems
Maintenance	Low operating costs	Higher maintenance required
Cost	Typically lower cost	Higher initial and operating costs

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Conclusion

The choice between a direct and pilot operated pressure reducing regulator depends largely on the requirements of your specific system: flow rate, pressure, and desired accuracy. Direct acting regulators offer simplicity and cost effectiveness for small scale applications. Pilot operated regulators, on the other hand, provide superior performance and reliability in harsh industrial environments where high flow rates are required.

 

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Cashco’s pressure reducing regulators are designed for precise pressure control across a wide range of industrial applications—delivering reliability, safety, and efficiency. For more information about Cashco's regulators, view all models here .

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