Selecting the correct pressure relief valve is a critical factor in any industrial installation handling pressurised fluids.

This type of valve protects equipment, personnel and processes against undesirable pressure increases, ensuring system stability and operational efficiency.

In this article, we will explore in detail how pressure relief valves operate, the key factors to consider when selecting the most suitable model, and the range of specialised solutions Valfonta offers for different industrial sectors.

If you need to guarantee maximum reliability in your operations, read on.

Content Table

What is a pressure relief valve?

A pressure relief valve is a device designed to open automatically when the pressure within a system exceeds a predefined limit, allowing controlled fluid release and preventing structural damage or accidents.

Its primary function is to protect the system against overpressure conditions that could compromise the integrity of pipelines, tanks, pumps or other critical components.

Although often confused, pressure relief valves and safety valves serve different purposes.

While safety valves are designed to open sharply during extreme emergency situations, relief valves respond progressively to moderate pressure increases, providing finer control and avoiding sudden fluctuations within the system.

These valves are essential in industries such as chemical processing, food production, energy generation and pharmaceuticals, where precise pressure control is vital to ensure reliable and safe operations.

Adjustable pressure relief valve

Pressure excess valve S1

Válvula de exceso de presión Valfonta Modelo PRV53

Pressure excess valve PRV53

How does a pressure relief valve work?

The operating principle of a pressure relief valve is simple yet highly effective. Under normal conditions, the valve remains closed while the system pressure stays below the preset set point.

When the inlet pressure exceeds this threshold, the force of the fluid overcomes the resistance of the internal spring or actuator, causing the plug to open progressively.

This movement allows part of the fluid to be discharged, thereby reducing the system pressure back to safe levels. Once equilibrium is restored, the spring forces the plug back into the closed position, and the valve automatically seals again.

In Valfonta models such as the S1, S2 and S3 valves, this mechanism is achieved through highly sensitive self-actuated systems, capable of operating with steam, compressed air, neutral gases or liquids, ensuring precise control across a wide range of pressures and temperatures.

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Key factors when selecting a pressure relief valve

Selecting the right pressure relief valve not only depends on the type of system where it will be installed, but also on a series of technical factors that will determine its efficiency, durability and long-term safety. Below, we outline the most important aspects you should consider before choosing the most appropriate model for your installation:

Type of fluid

The first fundamental criterion is the type of fluid that will circulate through the valve. Not all models are suitable for every medium.

Valfonta’s pressure relief valves are designed to operate with:

  • Steam
  • Compressed air
  • Neutral gases
    Industrial liquids

For example, if high-temperature steam is involved, a model capable of withstanding extreme thermal conditions, such as the S3 valve, would be necessary.

For corrosive fluids, it is advisable to select valves manufactured from AISI 316L stainless steel to ensure durability and chemical resistance.

Operating pressure range

Each valve has a specific pressure range within which it can operate safely and effectively.
 It is essential to know both the normal working pressure and any potential pressure peaks that may occur.

Examples of pressure regulation ranges in Valfonta products:

  • Model S1: 0.1 to 15 barg
  • Model S2: 0.02 to 10 barg
    Model PRV53: 0.5 to 10 barg
  • Model PRV55: 0.01 to 8 barg

Choosing a valve that operates comfortably within the correct pressure range will extend the service life of the valve and enhance the overall safety of the system.

Adjustable pressure relief valve

Pressure excess valve PRV55

Válvula industrial

Pressure excess valve S2

Operating temperature

The temperature of the fluid is another critical parameter to consider.
 Each membrane and gasket material has a safe operating temperature limit:

  • NBR: -20°C to 80°C
  • EPDM: -40°C to 125°C
  • PTFE: up to 220°C

In steam applications or systems handling very hot fluids, it is essential to ensure that both the valve body and internal components can withstand the expected temperatures.

Construction materials

The materials used for the valve body and internal components will directly affect its resistance to corrosion, pressure and temperature.

At Valfonta, we utilise materials such as:

  • Ductile iron GGG40.3
  • Carbon steel A216 WCB
    Stainless steel A351 CF3M

For demanding environments or aggressive fluids, it is strongly recommended to opt for models constructed entirely from stainless steel to ensure maximum reliability.

Connections and standards

Another important aspect to consider is the type of valve connection:

  • DIN flanges PN16–PN40
    ANSI 150/300 flanges
  • BSP or NPT threaded connections

Additionally, it is essential that valves comply with the relevant European standards, such as the Pressure Equipment Directive PED 2014/68/EU, and, where applicable, ATEX certification for explosive atmospheres.

Válvula de exceso de presion PRV54

Pressure excess valve PRV54

Types of pressure relief valves by Valfonta

At Valfonta, we offer a complete range of pressure relief valves designed to meet the needs of various industrial sectors. Each model is specifically engineered to suit different types of fluid, pressure ranges and operating temperatures. Below, we present a summary of our most prominent models:

Model Main features Recommended applications
S1 Self-actuated. Suitable for steam, air, gases and liquids. Pressure range from 0.1 to 15 barg. Constructed in ductile iron, carbon steel or stainless steel. General industrial systems, steam and compressed air.
S2 Self-actuated. Pressure range from 0.02 to 10 barg. Excellent response to overpressure events. Steam installations, neutral gases and liquids.
S3 High thermal resistance. Suitable for fluids up to 220°C. Pressure range from 0.5 to 20 barg. Guided plug design. Steam, chemical and food industry applications.
PRV53 Compact valve, easy to install. Inlet pressure up to 10 bar. Made from stainless steel. Compressed air, nitrogen, water and neutral gases.
PRV54 High thermal resistance up to 210°C. Bellows-balanced design. Wide pressure range (0.5–8 barg). Steam processes, chemical laboratories.
PRV55 Maximum pressure up to 25 barg. Robust construction. Operating temperature up to 180°C. Sanitary plants, steam, industrial gases.

Additionally, all our models can be supplied with different sealing options (NBR, EPDM, PTFE, FKM) and connection types according to the most demanding industrial standards (DIN, ANSI, BSP, NPT).

Each product’s technical datasheet is available on our website, where you can review detailed specifications or contact our technical department directly for advice on selecting the most suitable valve for your system.

 Installation and maintenance advice

Correct installation and proper maintenance are essential to guarantee the performance and service life of any pressure relief valve. Even the best design can fail if certain fundamental principles are not respected during assembly and operation. Below, we share the main practical recommendations to help you get the most from Valfonta’s pressure relief valves:

Installation: best practices

Before installing the valve, it is vital to thoroughly clean the inside of the piping to remove any solid particles or impurities that could damage the internal components.

It is recommended to install a strainer upstream of the valve to protect the seat and plug from debris carried by the fluid.

 Valfonta pressure relief valves must be installed in horizontal pipework, following the flow direction indicated by the arrow on the valve body.

 Pipe supports should be placed as close as possible to the flanges, ensuring that no weight or stress is transferred to the valve or actuator.

For models requiring an external pressure sensing line (such as the S1), this line must be connected at least 1 metre upstream from the valve, using appropriate tubing.

In steam systems or those handling hot liquids, it may be necessary to install a condensation pot to protect the diaphragm from thermal damage.

Maintenance: key actions to extend service life

 Although Valfonta valves are designed for low maintenance, regular inspections are recommended to check for leaks, plug wear or membrane deformation.

If deviations in opening pressure are detected, it is important to recalibrate the valve according to the manufacturer’s instructions by adjusting the nut or regulation screw.

 In extreme or intensive-use conditions, it may be advisable to replace seals and diaphragms after a certain number of opening/closing cycles, always using original replacement kits.

If the valve is not going to be installed immediately, it should be stored in a dry environment, protected from humidity, dust and extreme temperatures.

Válvula reductora de presión vapor

Frequently asked questions about pressure relief valves

The absence of a pressure relief valve in a system can lead to uncontrolled overpressure situations.

This can result in serious damage to pipelines, tanks, pumps or other equipment, as well as posing a significant safety risk to personnel.

A pressure relief valve acts as a passive safeguard: it remains closed under normal conditions and only activates when necessary, preventing costly or even catastrophic accidents.

Although both devices protect against overpressure, they serve distinct functions:

  • Pressure relief valve: Opens progressively in response to a controlled pressure increase. Ideal for processes requiring fine regulation.
  • Safety valve: Designed to open rapidly and fully during extreme overpressure events, acting as an emergency protection device.

In many systems, it is recommended to install both types of valves together to provide comprehensive protection.

The opening pressure is usually adjusted via a screw or nut located at the top of the valve actuator.
Turning clockwise increases the setpoint pressure, while turning anticlockwise reduces it.
This operation must be carried out carefully and, where possible, following the specific adjustment procedures provided for each model.

Although Valfonta’s pressure relief valves are designed for low maintenance, it is advisable to carry out a preventive inspection at least once a year, particularly in critical systems or intensive operating conditions.
 During inspection, the following should be checked:

  • Condition of the plug and seat
  • Membranes and seals
  • Proper operation of the regulation mechanism
  • Any leaks or accumulation of dirt

Correct maintenance ensures optimal performance and extends the service life of the valve.

 

If you have any questions about our pressure relief valves or would like to receive personalised advice, simply call us on (+34) 93 372 08 88 or email valfonta@valfonta.com.

You can also fill in the contact form with your details, and one of our sales representatives will get back to you as soon as possible.

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