Top Considerations When Selecting a High-Pressure Relief Valve
High-pressure relief valves fulfill a critical safety function in multiple applications, ranging from petrochemical to power, marine and aerospace industries. Regardless of the application, certain primary features can help guide engineers when selecting a durable high-pressure relief valve that will help avoid catastrophic failure to protect your workers’ health and safety while also preserving capital equipment.
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What’s the Primary Purpose of a Relief Valve?
A relief valve functions as an operational safety feature, to help control and regulate the flow of high-pressure fluids and gases. It is designed to vent off extra pressure, whether from gas or a liquid. The design triggers the valve to open once a system reaches a predetermined set pressure.
This protects systems from experiencing pressures that exceed their design limits. Once a system reaches that predetermined level or valve set pressure, the relief valve opens, and a portion of the liquid or gas is removed from the system by diverting it through an outlet in the valve.
The relief valve helps maintain safe pressure levels to prevent potential damage or catastrophic failure. Once system pressure drops to its predetermined normal level, the relief valve closes or “reseats” until it is needed again. While a relief valve functions as a safety feature, it differs from a safety valve which only triggers in an emergency.
A safety valve opens instantly to its full venting capacity while a high-pressure relief valve opens gradually when system pressure reaches the preset level.
A catastrophic failure could mean loss of capital equipment such as pipes if the pressure doesn’t diminish. Pressure build up, if unrelieved, can lead to more serious consequences such as an explosion, potentially harming personnel and causing more widespread damage to equipment and surroundings.
High-pressure relief valves are found in several different industries including marine applications on naval and commercial vessels, aerospace, industrial gas, the petrochemical industry, power plants and many industrial applications as well.
Factors for Specifying a Relief Valve
There are several factors to take into consideration when specifying a relief valve. These can include:
1. Set pressure limit
The set pressure limit is the threshold that triggers the high-pressure relief valve action. For example, if the normal system pressure is PSI the engineer might determine the set pressure limit is PSI. Once pressure reaches that threshold it triggers the relief valve which then vents the excess liquid or gas. Consistent triggering of the relief valve often indicates a problem with the system.
2. Valve capacity
This relates to the amount of flow the valve is able to relieve.
Connection size and type—The connection of the valve or valve size needs to correspond to the size of the discharge piping. Operators must also determine the connection type for the inlet and outlet ends, typically threaded or flanged.
3. Shock and vibration
Material selection, design and testing will reveal the ability of the valve to withstand shock and vibration without triggering its action. Naval vessels require parts such as relief valves pass specifications for shock and vibration.
4. Environment
This particularly plays a role in material selection for the valve construction when it will come into contact with a corrosive or abrasive substance. An example of this would be a marine relief valve that can or will regularly encounter salt water. All CPV Mfg. high-pressure relief valve specified for marine purposes are manufactured of bronze.
5. Temperature
This factor impacts O-ring material selection. Depending on the temperature range, CPV can specify a specialty elastomer or material for the O-ring.
6. Orifice size
This relates to the relief capacity of the valve. When the orifice size is smaller, the relief valve can rate to a higher pressure but relieve less capacity. The larger the orifice, the lower the pressure but the higher the relief capacity of the valve.
7. Positive Reseating
All relief valves manufactured by CPV have a positive reseating, which means after it blows at pressure, it reseats itself or reseals once the pressure drops into the normal range. This reseating capability allows for continuous operations. Look for a soft seating design which acts as a bubble tight seal, versus a metal-to-metal interface, which can be prone to leaking.
8. Spring adjustment
A sensitive spring, such as those incorporated into a CPV high-pressure relief valve, allows the operator to adjust the release for a very narrow PSI range. For example, the spring itself might be rated for 1,000 to 2,000 PSI, but the sensitivity enables the operator to set it at a specific target, such as 1,015 PSI, for example.
Add to this testing capabilities, and the cooperative efforts of the engineering design team and the valve manufacturer can produce a valve with the most accurate control of the blowdown pressure setting.
Why Choose CPV Manufacturing?
CPV manufactures relief valves in two different series: the 150 series and our flagship O-SEAL® line. The 150 series is a line of soft-seated female threaded relief valves with set pressures that range from the low end of 5 PSI up to 300 PSI.
The O-SEAL® line of soft-seated valves and separable fittings allow for positive control of high-pressure liquids and gases. This line offers leak proof performance from vacuum up to PSI (414 bar).
CPV has been supplying high-pressure relief valves to the U.S. Navy for mission critical applications since the s. Each individual valve built by CPV Manufacturing undergoes testing, not random or batch testing, but each valve.
Valves must meet a safety factor for the pressure rating of four to one. If a valve is rated for 6,000 PSI for example, the valve strength is up to or in excess of 24,000 PSI. In addition, all valves meet the ASME Boiler and Pressure Vessel Code. Our valves are over-engineered to exceed the pressure strength rating, for the utmost in reliability.
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Trust CPV Manufacturing for durable, reliable, high-pressure valves that meet the stringent requirements of the U.S. Navy, found in service in submarines, aircraft carries and other vessels throughout the fleet. We can work within your specifications or consult for customized projects and applications.
Pressure control valves play an essential role in refinery operations. If properly set up and integrated, the control valves will allow for the correct amount of different substances—in gaseous or liquid phases—for processes. This ultimately results in favorable outputs in terms of quantity and quality in an expedient manner.
When choosing a pressure control valve for oil and gas applications, it’s important to ensure that the valve can integrate seamlessly into your operations and safely transport the chemicals. This is especially true because the body of a control valve varies based on size and functional constraints. It’s also important to choose an actuator based on the amount of automation and method utilized for altering flow rate. Finally, control valves need to be constructed out of materials that are not corroded by the substances they encounter.
In this article, we will discuss options for the control valve body and its actuator to help you choose an appropriate pressure control valve for your oil and gas applications.
Understanding the Variations in Control Valve Body Elements
The control valve body can differ in material, size, motion, and design. The material used to construct the control valve body should be determined based on the properties of the chemical substances in operations. The overall size of the control valve will be determined by the piping and the ancillary equipment in processing. Valves generally use linear motion or rotation to adjust the working distance between two surfaces, the orifice, and the stem. Depending on how that is accomplished, the body can come in various shapes.
Control Valve Body Designs Options
There are three types of control valves based on body design: double block and bleed valves, manifold valves, and ball valves. These designs each have benefits for specific systems of operations as discussed below.
Double Block and Bleed Valves
Double block and bleed valves allow for primary isolation of substances. They can be designed to be small if space is limited. Double block and bleed valves are frequently used when an absolute shut-off is needed.
Manifold Valves
Manifold valves are often used within a larger system to isolate and control the flow of substances. They are frequently used to control the movement of substances between pumps and actuators. These valves are used to regulate flow in multiple directions (e.g. five-way valves if needed). They can be designed to be small to fit in systems with limited space.
Ball Valves
Ball valves provide a long service life (15+ years depending on the material used in construction). They can be designed to withstand high pressure and are frequently used for shutoff applications.
Once you’ve selected a pressure control valve body for your specific operation, you’ll want to select a compatible actuator.
Selecting the Control Valve Actuator
The control valve actuator is the device connected to the valve through the valve stem that provides the force required to move the valve. It opens and closes the valves based on different system conditions. These include changes in pressure, temperature, and flow. As such, they maintain substances at acceptable conditions for efficient operations. The design options for a control valve operator include the method of control such as controlling them electrically, pneumatically, or hydraulically. Choosing between these options is dependent on the chemical substance, the phase of matter of the substance, and if an electronic sensor is being used in conjunction with the valve.
The Benefits of a Fully Integrated and Optimized Control Valve
As control valves regulate the pressure and flow for different substances in operation, control valve failure can be very consequential:
- the correct amount of needed chemicals may not arrive at the specified location
- damage could occur to several systems
- leaks could occur due to a build-up of pressure
- overall operations could be delayed
When selecting control valves for safe and efficient operations, the application of the valve, the operation design specifications, the amount of pressure and temperature in operations, and the substance used in operations must all be taken into account. Swagelok offers several pressure control valve options to fulfill these needs.
Top-Quality Pressure Control Valves
The following table shows several top-quality options for control valves offered by Swagelok. These options differ based on the type of fuel being processed and options to increase efficiency and safety—such as preventing leaks to the atmosphere based on the pressure, flow, and the need for continuous use.
The control valve body plays an important role in controlling flow and there are several different designs to choose from. The type of processing occurring is important to consider for the materials being used in the valve and the type of control valve being used. If the type of processing is not considered, substances could be incompatible with the control valve and result in increased corrosion. The type of substances used in operation is also important as the pressure threshold varies between different types of control valves. A build-up in pressure could be damaging not only to the control valve but to systems and piping throughout the whole operation. Further, the operating methods employed are important to note for choosing a control valve actuator as differing levels of automation and control may require different actuators.
Expert Guidance on Choosing Pressure Control Valves for Oil and Gas Applications
An expert in control valves and refinery operations can help identify the optimal control valve option for processing based on the intended purpose of processing. Ultimately, the proper choice in a control valve will reduce maintenance costs and mitigate production delays. It is therefore ideal to work with an expert to get a fully optimal control valve based on your operational needs.
Swagelok has the experts to help you make the proper decisions for the implementation of upgrades of control valves. Swagelok’s control valves have a range of options including ball and quarter-turn plug valves, bellows-sealed valves, diaphragm sealed valves, and manifolds. These options will cover all your control valve needs.
For decades, we have helped process and manufacturing companies in Northern California and Western Nevada improve the reliability of critical components within their oil and gas applications. We’ll work closely with you to understand your specific process requirements. With this understanding, we’ll recommend pressure control valves for safe and efficient operations.
To learn more about how Swagelok Northern California can help you with your control valve needs, contact our team today by calling 510-933-.
Morgan Zealear | Product Engineer – Assembly Services
Morgan holds a B.S. in Mechanical Engineering from the University of California at Santa Barbara. He is certified in Section IX, Grab Sample Panel Configuration, and Mechanical Efficiency Program Specification (API 682). He is also well-versed in B31.3 Process Piping Code. Before joining Swagelok Northern California, he was a Manufacturing Engineer at Sierra Instruments, primarily focused on capillary thermal meters for the semiconductor industry (ASML).