Relief Valves

Relief Valves
Features and Benefits:

• Water, oil, and gas (WOG) compatible — designed to withstand extreme temperatures, pressure and chemicals.
• Firmly held, soft seated design assures rapid and positive sealing after relief, so it does not wobble or leak.
• Smooth and consistent open and close with a fully guided lift throughout actuation.
• The highest safety standards with sensitive spring adjustment that ensures precise control of the blowdown pressure setting.
• Wide range of options to relieve high or over- pressure to meet the specific needs of your application.

Frequently Asked Questions

How do your relief valves work?

CPV relief valves operate by using a spring-actuated mechanism to open when the pressure in the system exceeds a predetermined set point. This allows excess pressure to be released, maintaining system integrity.

What is their typical lifespan?

CPV relief valves are renowned globally for their unmatched strength and dependability. We engineer them to last for thousands of life cycles.

Do you have different valve end connectors?

Yes, CPV offers various valve end connectors to accommodate a wide range of installation requirements.

How do I select the right relief valve for my application?

That involves considering factors such as system pressure, flow rate, temperature and the type of fluid being handled. Contact us to help you choose the best relief valves for your specific application.

When should a pressure relief valve open and close?

A pressure relief valve opens when system pressure reaches its predetermined set pressure threshold, which must not exceed the maximum allowable working pressure of the protected system, and closes or “reseats” when system pressure drops back to its normal operating level. According to CPV Manufacturing’s engineering expertise, the set pressure selection is critical – for example, if normal system pressure is 3000 PSI, engineers might set the relief valve at 3300 PSI to provide adequate protection without nuisance operation during normal pressure fluctuations.

CPV’s high-pressure relief valves feature sensitive spring adjustment mechanisms that enable precise control of both opening pressure and blowdown characteristics, ensuring reliable operation when protection is needed while minimizing unnecessary venting. CPV manufactures relief valves in two proven series: the 150 series soft-seated valves with set pressures ranging from 5 PSI to 300 PSI, and their flagship O-SEAL® line designed for positive control of high-pressure liquids and gases in critical applications.

What are the different types of relief valves?

Relief valves encompass several distinct types:

• Spring-loaded direct-acting valves for general applications.
• Pilot-operated valves for large capacity or precise set pressure requirements.
• Thermal relief valves for closed systems subject to temperature increases.
• Pressure-reducing relief valves that maintain downstream pressure limits.

Each relief valve type offers specific advantages depending on the application requirements, system size and operating conditions. Spring-loaded valves provide simple, reliable operation for most applications, while pilot-operated designs offer superior accuracy and capacity for critical systems.

CPV Manufacturing’s comprehensive understanding of valve technology enables its engineers to recommend the optimal relief valve configuration for your specific safety and process protection requirements.

How are relief valves used across industries?

Relief valves provide essential overpressure protection across diverse industries, from residential water heaters to large industrial facilities, with each application requiring specific capacity, materials, and certification standards. However, CPV Manufacturing focuses its expertise specifically on high-pressure industrial applications including naval and commercial marine vessels, aerospace systems, petrochemical processing, industrial gas filling operations, liquid processing systems, and alternative energy and catalysis systems which encounter extreme pressures and which require mission-critical reliability.

CPV Manufacturing has developed specialized expertise in high-pressure relief valve solutions that meet the most stringent safety and performance requirements. The proof of its expertise lies in decades of supplying relief valves to the U.S. military and naval operations and in its support for the NASA space program. Its relief valve offerings include the 150 series (5-300 PSI) and the flagship O-SEAL® line designed for high-pressure applications up to 6000 PSI, serving industries where failure is not an option.

What’s the difference between a relief valve and a pop (safety) valve?

Pop safety valves open rapidly and fully when the set pressure is reached, providing maximum flow capacity immediately and remaining open until pressure drops significantly below the set point, while relief valves may open gradually and proportionally to pressure increase, providing more controlled pressure reduction. Pop valves are typically used where rapid pressure relief is critical for safety, such as steam boilers and pressure vessels, whereas relief valves are often preferred for liquid applications or where gradual pressure control is desired.

The choice between these valve types depends on the fluid being handled, the required response characteristics, and applicable safety codes. Pop valves provide better protection against rapid pressure rise but may cause more system disturbance when they operate. CPV Manufacturing’s extensive experience in both safety-critical and process applications enables them to recommend the appropriate valve type and configuration for optimal system protection and performance.

What safety standards and codes apply to relief valves?

Relief valves must comply with various safety standards, and in some industries these include ASME Section VIII (pressure vessels), API 520/521 (sizing and installation), ISO 4126 (safety devices) and regional standards such as PED (Pressure Equipment Directive) in Europe. These standards specify design requirements, testing procedures, materials, and installation practices to ensure reliable operation under emergency conditions. Additional industry-specific codes may apply, such as NFPA for fire protection systems or ASME B31 for piping systems.

Compliance verification through third-party testing and certification is often required for critical applications. Regular inspection and maintenance per these standards help the valve provide continued safe operation throughout its service life. CPV Manufacturing’s relief valve solutions meet or exceed all applicable safety code requirements.

Why is choosing the correct set pressure important for a relief valve?

Correct set pressure selection ensures equipment protection without unnecessary operation during normal pressure fluctuations, preventing premature valve wear and product loss while maintaining system safety. Setting the pressure too low causes frequent nuisance operation, wasting product and reducing valve life, while setting it too high risks equipment damage or failure before relief occurs.

The set pressure must account for normal operating pressure variations, system dynamics and pressure vessel design limits. CPV Manufacturing’s engineering expertise helps customers select optimal set pressures that balance safety requirements with operational efficiency for long-term reliable performance.

What is blowdown and why does it matter in relief valve selection?

Blowdown refers to the pressure differential between valve opening and closing, typically expressed as a percentage of the set pressure, and determines how much system pressure must drop before the valve reseats and stops relieving. This characteristic prevents valve chattering during pressure fluctuations and ensures stable operation, but excessive blowdown can result in unnecessary pressure loss and reduced system efficiency. The required blowdown depends on system characteristics, fluid properties, and operational requirements, with typical values ranging from 2-20% of set pressure.

Proper blowdown selection balances valve stability with system performance requirements. Applications with rapid pressure changes may require higher blowdown to prevent cycling, while systems sensitive to pressure loss need minimal blowdown values. CPV Manufacturing’s detailed understanding of valve dynamics enables them to provide relief valves with optimized blowdown characteristics tailored to specific application requirements for reliable, efficient operation.