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A pressure relief valve is an automatic pressure-relieving device that opens when system pressure reaches a predetermined set pressure. It discharges gas, vapor, steam or liquid to prevent the protected equipment from exceeding its allowable pressure limit, then closes again when pressure returns to a safe level. In engineering work, a pressure relief valve is …
A pressure relief valve is an automatic pressure-relieving device that opens when system pressure reaches a predetermined set pressure. It discharges gas, vapor, steam or liquid to prevent the protected equipment from exceeding its allowable pressure limit, then closes again when pressure returns to a safe level.
In engineering work, a pressure relief valve is not treated as a normal valve. It is a final mechanical protection device for pressure vessels, boilers, pipelines, compressor packages, heat exchangers, process skids, pump discharge lines and other pressurized systems. If the pressure relief valve is incorrectly selected, installed or maintained, the system may remain exposed to overpressure even though a valve is physically installed.
The most common mistake is to define a pressure relief valve only by its inlet size, outlet size or pressure rating. A valve may fit the nozzle, but that does not prove it has the required relieving capacity. A valve may have the correct set pressure, but that does not prove it can discharge enough flow during the governing relief case. A valve may pass shop testing, but still chatter after installation if back pressure or inlet pressure loss was not reviewed.
This guide explains what a pressure relief valve is, how it works, how it differs from a safety valve or PSV, where it is used, what causes it to open, and what engineers and buyers should check before selection or purchase. For the complete engineering selection process, read our Safety Valve Selection Guide.
Engineering takeaway: A pressure relief valve should be selected from the protection requirement first, not from the catalog model first. The key checks are protected equipment, relief scenario, set pressure, required relieving capacity, certified capacity, medium condition, back pressure, valve type, material compatibility and documentation.
A pressure relief valve, often shortened as PRV, is an automatic device designed to release pressure from a system when the inlet pressure reaches a specified set pressure. Its purpose is to reduce the risk of excessive pressure in the protected equipment.
Unlike a manual valve or a control valve, a pressure relief valve does not depend on an operator to open it during an emergency. It responds automatically to pressure. When system pressure rises to the set pressure, the valve begins to open. As pressure continues to rise during the relieving event, the valve must pass enough flow to control the overpressure condition. After the system pressure falls to a safe level, the valve should reseat properly.
In practical engineering terms, a pressure relief valve answers one basic question:
How will the system release pressure if pressure rises above the allowable limit?
The valve may discharge to atmosphere, a safe drain, a closed vent system, a flare header, a recovery system or another approved discharge destination. The correct discharge arrangement depends on the medium, pressure, temperature, toxicity, flammability, environmental requirement and local regulation.
Pressure relief valves are used to protect many types of pressure equipment, including:
The protected equipment determines the pressure boundary, design pressure, maximum allowable working pressure, relief scenario and applicable code requirement.
A normal valve is usually selected for isolation, throttling, flow control or switching duty. A pressure relief valve is selected for pressure protection. That difference changes the selection logic.
For a normal valve, connection size and pressure rating are often major purchase details. For a pressure relief valve, they are only part of the review. The engineer must also confirm set pressure, required relieving capacity, certified relieving capacity, orifice area, back pressure, material compatibility, seat tightness, installation condition and documentation.
A pressure relief valve that is wrong by capacity or wrong by service condition may still look correct on a drawing. That is why engineering review is required before purchase and installation.
A pressure relief valve works by balancing closing force against system pressure. In a spring-loaded valve, spring force keeps the disc against the nozzle seat. In a pilot-operated design, the pilot system controls the main valve. The exact mechanism depends on valve type, but the protection sequence is similar.
During normal operation, the valve remains closed. The operating pressure should normally stay below the set pressure with enough margin to avoid simmering, leakage or frequent lifting.
If the system operates too close to set pressure, the valve may leak before an actual emergency condition. The cause may not be a defective valve. It may be poor operating margin, pressure fluctuation, damaged seating surfaces, dirt at the seat, back pressure fluctuation or piping stress.
Set pressure is the inlet pressure at which the pressure relief valve starts to open under specified test conditions. It determines when the valve begins to respond.
Set pressure does not prove that the valve has enough relieving capacity. A valve can open at the correct pressure and still be undersized if its certified relieving capacity is lower than the required relieving load.
For a deeper explanation of set pressure, overpressure, accumulation and blowdown, read our Safety Valve Set Pressure, Overpressure and Blowdown Explained.
After the valve opens, it must discharge enough fluid to control the pressure rise. This is where required relieving capacity and certified relieving capacity become critical.
The required relieving capacity comes from the governing relief scenario. The certified relieving capacity is the verified capacity of the selected valve under a stated basis. These two values should be compared before the valve is approved.
For detailed capacity review, read our Safety Valve Sizing and Certified Relieving Capacity Guide.
After discharge, the valve should reseat when system pressure falls to the reseating pressure. Reseating depends on blowdown, spring force, seat condition, guide condition, back pressure, inlet pressure loss and valve design.
Poor reseating can lead to product loss, noise, emissions, repeated cycling and seat damage. A valve that does not reseat properly should not be adjusted blindly. The operating pressure trend, discharge system, seat condition and calibration history should be reviewed first.
The terms pressure relief valve, relief valve, safety valve, safety relief valve, PRV and PSV are often mixed in plant documents and purchase requests. They are related, but they should not be treated as identical without checking the actual service condition and valve design.
| Term | Common Engineering Meaning | Typical Service | Selection Warning |
|---|---|---|---|
| Pressure relief valve | General term for a device that relieves excess pressure | Gas, vapor, steam, liquid or two-phase service depending on design | Must confirm valve design, capacity basis and medium state |
| Relief valve | Often used for liquid service with more gradual opening | Liquid systems, thermal expansion, pump discharge | Do not assume it is suitable for gas or steam without confirmation |
| Safety valve | Often associated with rapid opening in steam, gas or vapor service | Steam boilers, steam headers, air and gas systems | Must verify set pressure, capacity and applicable code |
| Safety relief valve | Design that may be suitable for gas, vapor, steam or liquid service depending on certification | Mixed industrial pressure protection duties | Check actual service and manufacturer data |
| PSV | Often means pressure safety valve in plant documents | Process plants, pressure vessels, oil and gas systems | The abbreviation alone does not define valve design |
| PRV | Often means pressure relief valve, but can be used differently by industry | General pressure relief service | Confirm whether the document means relief valve, safety relief valve or pressure reducing valve |
A pressure relief valve is a broad term. It may refer to devices used for gas, vapor, steam, liquid or two-phase relief, depending on valve design and certification.
In procurement, the term PRV should not be used alone. The buyer should also specify medium, fluid state, set pressure, required capacity, back pressure, valve type and applicable standard.
A relief valve is often associated with liquid service. It may open more gradually as pressure rises. This can be suitable for liquid thermal expansion or hydraulic relief service, but the actual design must still be checked.
A safety valve is commonly associated with steam, air, gas and other compressible fluids. It is usually designed for rapid opening at set pressure. Steam boiler safety valves and air receiver safety valves are common examples.
A safety relief valve may be designed for gas, vapor, steam or liquid service, depending on its design and certification. It should not be selected by name only. The actual certified service and sizing basis must be reviewed.
In many process industry documents, PSV is used for pressure safety valve and PRV is used for pressure relief valve. However, abbreviations can vary by company and country. In some contexts, PRV may also mean pressure reducing valve, which is completely different from a pressure relief valve.
The abbreviation does not tell you the required relieving capacity, valve type, orifice area, seat design, back pressure limit, material compatibility or certification basis. For engineering selection, the actual service condition is more important than the abbreviation.
Field judgment: When a request only says “PRV” or “PSV,” do not approve the valve until the medium, fluid state, set pressure, required capacity, back pressure, valve type and documentation basis are confirmed.
Different pressure relief valve designs respond differently to pressure, back pressure, medium cleanliness, temperature and maintenance conditions. The valve type should be selected by service condition, not only by price or availability.
A spring-loaded pressure relief valve uses spring force to hold the disc closed. When inlet pressure reaches the set pressure, system pressure overcomes the spring force and the valve opens.
Spring-loaded valves are widely used in steam, air, gas, pressure vessel and many utility services. They are relatively simple and easier to inspect than more complex designs. However, conventional spring-loaded valves can be sensitive to back pressure and inlet pressure loss.
A balanced bellows valve uses a bellows arrangement to reduce the effect of back pressure on valve operation. It may be considered when a conventional spring-loaded valve would be too sensitive to superimposed or built-up back pressure.
The bellows is a critical component. It can fail due to fatigue, corrosion, overheating or improper venting. A balanced bellows valve should be selected within the manufacturer’s limits and maintained with attention to bellows condition and bonnet vent requirements.
A pilot-operated pressure relief valve uses a pilot valve and system pressure to control the main valve. It may be suitable for clean high-pressure gas service, large-capacity duty, tight shutoff requirements or systems operating close to set pressure.
It should be reviewed carefully for dirty, wet, sticky, crystallizing, polymerizing or particle-containing service. Contamination in the pilot circuit or sensing line can affect stability and response.
A thermal relief valve is commonly used to protect blocked-in liquid sections from pressure rise caused by thermal expansion. The required flow may be small, but the pressure rise can be rapid.
Thermal relief valves are often used on liquid-filled piping, pump systems and isolated equipment sections. They should still be selected with the correct set pressure, material, discharge destination and service compatibility.
Safety relief valves may be used for compressible service such as gas, vapor and steam, depending on design and certification. For steam service, temperature, drainage, discharge reaction force and seat material are important review points.
For a detailed comparison of valve types, read our Spring-Loaded Safety Valve vs Pilot-Operated Safety Valve.
| Valve Type | Often Suitable For | Main Selection Risk |
|---|---|---|
| Spring-loaded | General steam, air, gas and utility service | Back pressure, inlet loss and chatter risk |
| Balanced bellows | Services with back pressure influence | Bellows fatigue, corrosion and vent blockage |
| Pilot-operated | Clean high-pressure gas, tight shutoff and large capacity | Pilot circuit contamination and maintenance sensitivity |
| Thermal relief | Blocked-in liquid thermal expansion | Small flow may lead to careless selection |
A pressure relief valve cannot be selected correctly unless the key parameters are understood. The buyer should not treat these as catalog words. Each parameter affects how the valve protects the system.
| Parameter | What It Affects |
|---|---|
| Set pressure | When the valve starts to open. |
| Operating pressure | Margin below set pressure and leakage tendency. |
| Overpressure | Pressure rise above set pressure during relief. |
| Accumulation | Pressure rise experienced by the protected equipment. |
| Blowdown | How far pressure must fall before the valve reseats. |
| Required relieving capacity | Flow required to protect the equipment during the governing relief case. |
| Certified relieving capacity | Verified valve capacity under a stated basis. |
| Orifice area | Internal flow area related to rated capacity. |
| Back pressure | Opening behavior, lift, capacity, stability and reseating. |
| Seat tightness | Leakage performance during normal operation. |
| Material compatibility | Corrosion, erosion, sticking, leakage and service life. |
Set pressure defines when the pressure relief valve starts to open. It should be selected in relation to the protected equipment’s pressure limit, operating pressure and applicable code requirement.
Raising set pressure to stop leakage is dangerous unless it is approved by engineering and followed by recalibration, resealing and documentation update.
Operating pressure is the normal pressure of the system. If it is too close to set pressure, the valve may simmer, weep, leak or lift during normal fluctuation.
Overpressure is the pressure increase above set pressure during a relief event. Accumulation is the pressure increase above the protected equipment pressure limit. They are related, but they are not the same.
Blowdown affects when the valve closes after opening. If blowdown is too narrow, the valve may cycle. If it is too wide, the system pressure may drop more than necessary before reseating.
Required relieving capacity is the flow that must be discharged to prevent the protected equipment from exceeding its allowable pressure limit during the governing relief scenario.
Certified relieving capacity confirms the verified relieving capability of the valve. Orifice area is related to the internal flow path and capacity. Connection size and orifice area are not the same.
A valve with the same inlet connection may have a different orifice and a different certified capacity. This is why replacement by flange size alone can be unsafe.
Back pressure is pressure at the valve outlet. It may exist before the valve opens, or it may be created after the valve opens and flow passes through the discharge system.
Back pressure can affect opening, lift, capacity, chatter, blowdown and reseating. For a deeper explanation, read our How Back Pressure Affects Safety Valve Performance.
Seat tightness affects leakage during normal operation. Leakage can be caused by damaged seating surfaces, dirt, corrosion, operating pressure too close to set pressure, wrong seat material, piping stress or poor repair practice.
Material compatibility should cover the body, bonnet, nozzle, disc, guide, spring, bellows and seat. Corrosion on the nozzle or disc seating surface can cause leakage even when the spring setting remains correct.
Pressure relief valves are used wherever credible overpressure can occur. Different applications create different risks, so the valve should be reviewed for the actual service condition.
| Application | Main Engineering Concern |
|---|---|
| Pressure vessels | MAWP, relief scenario, certified capacity and code basis. |
| Steam boilers and steam systems | Set pressure, steam capacity, high temperature, drainage and discharge reaction force. |
| Air compressors and air receivers | Operating margin, compressor control range, pulsation and seat leakage. |
| Chemical and petrochemical systems | Corrosion, two-phase relief, toxic release, flare or closed vent connection. |
| Oil and gas, LNG and refinery systems | Relief scenario, flare header pressure, back pressure and material requirements. |
| Pump discharge and thermal expansion service | Liquid relief, thermal expansion and blocked-in pressure rise. |
| Heat exchangers and process skids | Tube rupture, gas blow-by and package documentation. |
Pressure vessels require protection against overpressure from blocked outlet, external fire, regulator failure, process upset or other credible scenarios. The selected valve should match the vessel pressure boundary and required relief case.
Steam service requires careful attention to set pressure, steam capacity, high temperature, condensate drainage, outlet support and discharge reaction force. A liquid relief valve should not be casually used for steam service.
Air systems often experience pressure cycling and pulsation. If compressor cut-out pressure is too close to valve set pressure, the valve may simmer or leak during normal operation.
Chemical service may involve corrosion, polymerization, crystallization, toxicity, fouling or two-phase relief. Material compatibility and discharge destination must be reviewed carefully.
Oil and gas systems often discharge to closed headers or flare systems. Back pressure, simultaneous relief, flare system capacity and sour service material requirements may affect valve selection.
Liquid-filled blocked-in sections can develop high pressure from a small temperature rise. The required flow may be small, but the pressure protection function is still important.
Heat exchanger tube rupture can expose a low-pressure side to a high-pressure fluid. Process skids may also include package-specific relief valves that must be reviewed against the final installed system.
A pressure relief valve opens when system pressure reaches its set pressure, but the reason pressure rises depends on the relief scenario. Identifying the correct relief scenario is essential because it determines required relieving capacity.
| Relief Scenario | Why It Matters |
|---|---|
| Blocked outlet | Flow cannot leave the equipment, so pressure may rise rapidly. |
| External fire exposure | Heat input can vaporize liquid or expand gas. |
| Thermal expansion | Blocked-in liquid can generate high pressure from a small temperature increase. |
| Pressure regulator failure | Downstream equipment may be exposed to higher upstream pressure. |
| Control valve failure | Excess flow or pressure may enter protected equipment. |
| Heat exchanger tube rupture | High-pressure fluid can enter a low-pressure side. |
| Gas blow-by or process upset | Unexpected gas or vapor generation can increase pressure. |
A blocked outlet can cause pressure to rise when incoming flow continues but the discharge path is closed or restricted. This is a common governing case for vessels, separators and process equipment.
External fire can add heat to a vessel, causing liquid vaporization, gas expansion or pressure rise. Fire case sizing should not be ignored simply because the valve rarely opens in normal operation.
When liquid is trapped between closed valves, temperature rise can create a large pressure increase. Thermal relief valves are commonly used for this duty.
If a regulator fails open, downstream equipment may be exposed to pressure above its design limit. The relief valve must be selected for the credible failure case.
A failed control valve can send too much flow or pressure into a system. The relief scenario should consider the upstream pressure source and downstream equipment limitation.
A tube rupture can allow high-pressure fluid to enter the low-pressure side of a heat exchanger. This can create a rapid overpressure condition and must be evaluated carefully.
Gas blow-by, vapor generation, reaction upset or cooling failure can create relief loads that are much higher than normal operating flow. These cases should be reviewed before sizing or purchasing a valve.
Pressure relief valve problems often begin before the valve is installed. Many failures come from incomplete selection data, wrong assumptions or replacement without engineering review.
| Mistake | Possible Consequence | Prevention |
|---|---|---|
| Selecting by connection size only | Valve fits the nozzle but lacks required certified capacity. | Check orifice area and certified relieving capacity. |
| Confusing set pressure with capacity | Valve opens at the right pressure but cannot relieve enough flow. | Compare required capacity with certified capacity. |
| Ignoring back pressure | Chatter, flutter, reduced capacity or poor reseating. | Review outlet piping, header pressure and allowable back pressure. |
| Using the wrong valve type for dirty service | Pilot instability, guide sticking or seat leakage. | Review medium cleanliness and maintenance access. |
| Ignoring material compatibility | Corrosion, galling, leakage or early failure. | Check body, nozzle, disc, guide, spring, bellows and seat materials. |
| Accepting incomplete test documents | Inspection delay or unverified protection capability. | Request datasheet, capacity data, material certificate and test reports. |
A replacement valve with the same inlet size may not have the same orifice area or certified capacity. The replacement should be checked against the original design basis and required relieving capacity.
Set pressure only defines when the valve starts to open. Capacity defines whether it can relieve enough flow. These two values must both be correct.
A valve that passes bench testing may become unstable after installation if outlet resistance or common header pressure creates excessive back pressure.
Pilot-operated valves can be excellent in clean service, but dirty or wet gas can affect the pilot circuit. Service cleanliness should be reviewed before selecting a pilot-operated design.
Seat leakage is often caused by corrosion or erosion at the nozzle and disc. Material review should include internal trim parts, not only the body material.
Without proper capacity data, calibration certificate, material certificate and seat leakage report when required, the buyer may not be able to verify the valve’s suitability.
The following examples show why pressure relief valve selection should be based on engineering data, not only catalog size or purchase price.
A pressure vessel had a relief valve with the correct set pressure. The valve opened near the expected pressure during testing, so it appeared acceptable. During a fire-case review, however, the required relieving capacity was higher than the valve’s certified capacity.
The root cause was a replacement decision based on connection size and pressure rating. The replacement valve had a smaller effective orifice than the original design basis. The correction was to recalculate the required relieving load and select a valve with certified capacity equal to or greater than the governing relief case.
The prevention is to compare required relieving capacity, orifice designation and certified capacity before approving any replacement.
A spring-loaded pressure relief valve passed shop testing and opened at the correct set pressure. After installation, it chattered during discharge. The first suspicion was a spring or seat problem.
A field review found that the outlet line had been extended and connected to a common discharge header. The added outlet resistance increased built-up back pressure. The valve itself was not defective; the installed discharge condition had changed.
The correction was to review outlet resistance, common header pressure and valve type suitability. The prevention is to include back pressure and discharge system data in the selection review before purchase.
A pressure relief valve began leaking after a period of service in a corrosive medium. The set pressure was still close to the required value, but the leakage increased after each lift event.
Inspection showed corrosion damage at the nozzle and disc seating surface. The root cause was not only poor lapping. The trim material was not suitable for the actual fluid chemistry. The correction was to review material compatibility for the nozzle, disc, guide, spring and seat.
The prevention is to treat material selection as a functional protection issue, not only a body material question.
Standards should be used to support real engineering decisions. They should not be listed only for appearance. The applicable standard depends on equipment type, industry, country, project specification and owner requirement.
| Standard / Code Direction | Where It Matters |
|---|---|
| ASME BPVC Section VIII Division 1 | Pressure vessel design, inspection, testing and certification basis. |
| ASME BPVC Section I | Boiler and steam boiler pressure protection. |
| API 520 Part I | Sizing and selection of pressure-relieving devices. |
| API 520 Part II | Installation review for pressure-relieving devices. |
| API 521 | Pressure-relieving and depressuring systems, flare and relief scenario context. |
| API 527 | Seat tightness testing of pressure relief valves. |
| ISO 4126 | Safety devices for protection against excessive pressure in international projects. |
| National Board / NBIC / VR | Inspection, repair, recertification and pressure relief valve repair authorization. |
| NACE MR0175 / ISO 15156 | Sour service material requirements when H2S service applies. |
ASME BPVC is commonly referenced for boilers and pressure vessels. ASME Section VIII Division 1 is associated with pressure vessels, while ASME Section I is relevant to boilers. The exact code basis should be confirmed by project specification and local jurisdiction.
For pressure vessel projects, refer to ASME BPVC Section VIII Division 1.
API 520 Part I is a key reference direction for sizing and selection of pressure-relieving devices in refinery and related process industry applications. API 520 Part II focuses on installation considerations and engineering analysis for pressure-relieving devices.
API 521 is relevant where the pressure relief valve is part of a larger relief system, flare system or depressuring system, especially in refinery, LNG, petrochemical, gas plant and oil and gas facilities.
API 527 is commonly referenced for determining seat tightness of metal- and soft-seated pressure relief valves, including conventional, bellows and pilot-operated designs.
ISO 4126 is relevant for international projects involving safety devices for protection against excessive pressure. ISO 4126-1 applies to safety valves, while ISO 4126-4 is relevant to pilot-operated safety valves.
For repaired pressure relief valves, inspection and repair requirements may involve NBIC and National Board VR authorization depending on project, jurisdiction and owner specification. The National Board VR Certificate of Authorization is relevant for organizations repairing pressure relief valves under that framework.
A supplier cannot correctly select a pressure relief valve from connection size and pressure rating alone. The buyer should provide enough process, equipment and installation data to support engineering review.
Provide the protected equipment type, equipment tag, MAWP or design pressure, design temperature, operating pressure, operating temperature and applicable code requirement.
Provide set pressure, relieving pressure, normal operating pressure, relieving temperature and any expected pressure fluctuation. These values affect opening behavior, capacity and material selection.
Define whether the medium is steam, gas, vapor, liquid, two-phase or flashing. Also state whether the service is clean, dirty, corrosive, sour, sticky, crystallizing, polymerizing or particle-containing.
Provide the required relieving capacity and its basis. If this value is unknown, the valve selection should be considered preliminary.
Provide outlet destination, superimposed back pressure, estimated built-up back pressure, outlet pipe size and length, silencer data, common header pressure and discharge system information.
State the required body material, trim material, spring material, bellows material and seat type where applicable. If seat tightness is important, include the required leakage test standard.
Request the valve datasheet, certified capacity data, general arrangement drawing, material certificate, pressure test report, calibration certificate, seat leakage test report if required, nameplate data and installation manual.
For a full buyer-focused checklist, read our Safety Valve Procurement Checklist for Engineers and Buyers.
Before approving a pressure relief valve quotation, check whether the valve can protect the actual system, not only whether it can fit the piping.
| Check Item | Confirmed |
|---|---|
| Protected equipment identified | ☐ |
| MAWP / design pressure confirmed | ☐ |
| Operating pressure and set pressure confirmed | ☐ |
| Relief scenario identified | ☐ |
| Required relieving capacity calculated | ☐ |
| Certified relieving capacity verified | ☐ |
| Medium and fluid state confirmed | ☐ |
| Back pressure reviewed | ☐ |
| Valve type selected for service condition | ☐ |
| Material and seat design confirmed | ☐ |
| Installation condition reviewed | ☐ |
| Applicable standard confirmed | ☐ |
Final engineering question: Can this pressure relief valve relieve the required load under the actual medium, relieving temperature, back pressure and installation condition, and can the supplier prove it with certified data and test documents?
Send your medium, set pressure, required relieving capacity, relieving temperature and back pressure condition for pressure relief valve engineering review.
Related pressure relief valve engineering guides:
Author / Engineering Review Note: This article is written from a pressure relief valve and safety valve engineering review perspective, including selection, sizing awareness, back pressure, installation, material compatibility, maintenance and procurement documentation. Final valve selection should follow the applicable project specification, local regulation, equipment code and manufacturer-certified data.
A pressure relief valve is an automatic device that opens when system pressure reaches a predetermined set pressure. It discharges fluid to prevent the protected equipment from exceeding its allowable pressure limit and closes again when pressure returns to a safe level.
A pressure relief valve remains closed during normal operation. When inlet pressure reaches the set pressure, the valve opens and relieves flow. After pressure falls to the reseating pressure, the valve should close again.
Not always. A pressure relief valve is a broad term. A safety valve is commonly associated with rapid opening in steam, gas or vapor service. A relief valve is often associated with liquid service. The correct term and valve type depend on medium, design, certification and application.
PRV often means pressure relief valve, while PSV often means pressure safety valve. However, abbreviations vary by company and industry. The abbreviation alone is not enough for selection. The service condition, valve design, set pressure, required capacity and certification basis must be reviewed.
A pressure relief valve opens when system pressure reaches its set pressure. The pressure rise may be caused by blocked outlet, external fire, thermal expansion, regulator failure, control valve failure, heat exchanger tube rupture, gas blow-by or process upset.
A pressure relief valve may leak because operating pressure is too close to set pressure, the seat is damaged, dirt or corrosion is present, back pressure fluctuates, the seat material is wrong, piping stress distorts the valve or repair quality is poor.
Not without engineering review. The same inlet size does not prove the same orifice area or certified relieving capacity. Replacement should confirm set pressure, certified capacity, orifice designation, material, valve type and documentation.
To choose a pressure relief valve, confirm the protected equipment, relief scenario, set pressure, required relieving capacity, medium, fluid state, relieving temperature, back pressure, valve type, material, seat design, installation condition and applicable standard.
Provide protected equipment data, MAWP or design pressure, operating pressure, set pressure, required relieving capacity, medium, fluid state, relieving temperature, back pressure, valve type preference, material requirement, testing requirement and documentation requirement.
ZOBAI focuses on safety valve solutions for pressure systems, including spring loaded safety valves, pilot operated pressure relief valves, bellows balanced designs, sanitary systems, jacketed service, LNG and LPG applications, and other engineered pressure protection products.
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