Safety valves – spring-loaded pressure relief valves for air, steam and gas
A safety valve is used when your system requires protection against excessive pressure as the final mechanical safeguard. A safety valve opens automatically once the set pressure is exceeded, discharges the excess pressure, and closes again independently. Spring-loaded safety valves are most commonly applied in systems handling compressed air, steam, gas and liquids. Ebora specialises in the selection and supply of spring-loaded safety valves for industrial applications, including versions with PED certification (2014/68/EU).
When do you use a safety valve?
A safety device is mandatory in any system where pressure can rise above the safe operating limit of the installation. This can occur when a pressure regulator fails, a process deviation occurs, or a blockage develops in the system. A safety valve is the last line of defence — it protects first and foremost the people working on the installation, then the installation itself, and finally the process.
Please note: a spring-loaded safety valve is not intended for the continuous discharge of excess pressure during normal operation. If that is what you require, you need a pressure relief valve or overflow valve, not a safety valve.
Safety valve or pressure relief valve – what is the difference?
This is the most frequently asked question when selecting pressure protection equipment. The difference lies in the opening characteristic and the intended use.
A safety valve (spring-loaded) opens rapidly and fully once the set pressure is exceeded by 10%. It discharges the full excess pressure and then closes again. It is intended exclusively for emergency situations and should never activate during normal operation. After activation, Ebora recommends replacing the valve to continue guaranteeing system safety.
- Set pressure is reached; valve is still closed.
- Set pressure is exceeded; disc begins to lift.
- At 10% above set pressure, the valve opens rapidly and fully.
- Maximum opening is reached – the valve discharges the total excess pressure.
- Pressure drops below set pressure – the valve begins to close gradually.
- At 10% below set pressure (gases) or 20% (liquids), the valve is fully closed again.
Points 1, 3, 4 and 6 are defined in standard DIN EN ISO 4126-1.
The opening characteristic of a pressure relief valve differs significantly. A pressure relief valve may discharge continuously and is frequently used as an overflow protection on pumps to prevent the pump from running against a closed valve.
- Set pressure is reached; pressure relief valve is still closed.
- Set pressure is exceeded; the valve opens proportionally to the overpressure.
- At the required overflow capacity, the pressure relief valve self-adjusts.
- As system pressure decreases, the pressure relief valve begins to close.
- System pressure continues to fall and the valve closes further.
- At a pressure just below the set pressure, the pressure relief valve is fully closed.
For more information, please refer to the pressure relief valve and overflow valve product page.
What types of safety valves are available?
The two most commonly used designs are spring-loaded and weight-loaded safety valves.
Spring-loaded safety valves are the standard in industrial installations. The spring determines the opening pressure and is easy to adjust. Ebora supplies spring-loaded safety valves for a wide range of media and pressures, including bellows versions for applications with back pressure on the discharge side.
Weight-loaded safety valves use a weight as the opposing force. The risk here is that an operator may reposition the weight — intentionally or accidentally — causing pressure in the system to rise to a dangerous level. This design is therefore less common in modern industrial installations.
Where are safety valves applied?
Spring-loaded safety valves are used across a wide range of sectors and media:
- Compressed air and gas pipelines
- Steam systems and steam boilers
- Pressure vessels and heat exchangers
- Chemical and petrochemical industry
- Biogas installations
- Food, pharmaceutical and cosmetic industry
- Shipbuilding and technical gases
Ebora supplies safety valves for liquids, gases and vapours, including steam, compressed air and cryogenic media. For pressure measurement in combination with your safety system, Ebora also supplies pressure sensors and pressure gauges.
Spring-loaded safety valves from Goetze, Spirax Sarco and ARI Armaturen
Ebora supplies spring-loaded safety valves from three specialist manufacturers, each with a distinct area of expertise.
Goetze Armaturen offers an extensive range of safety valves in brass and stainless steel for compressed air, gas and liquids, with EN and PED certification.
Spirax Sarco is the specialist for steam applications. Their safety valves are specifically designed for steam, hot water lines and condensate systems, meeting the most stringent process requirements.
ARI Armaturen supplies robustly constructed safety valves for industrial applications at higher pressures and temperatures, including versions for steam, gas and liquids with ATEX and PED documentation.
Ebora advises you on the right brand and design based on your medium, pressure and certification requirements.
What information is needed for correct valve selection?
For correct selection of your safety valve, Ebora requires the following data:
| Selection parameter |
Details |
| Medium |
Air, steam, gas, liquid or vapour |
| Set pressure |
The required activation pressure in bar |
| Back pressure |
Pressure on the discharge side (relevant for bellows version) |
| Temperature |
Process temperature in °C |
| Discharge capacity |
Required flow rate at full open position |
| Material |
Brass, stainless steel, grey cast iron |
| Certification |
PED (2014/68/EU), ATEX or none |
Choose a version with an internal bellows if back pressure is present on the discharge side. Without a bellows, back pressure can shift the activation point of the safety valve.
Set pressure, operating pressure and reseating pressure – what is the difference?
When selecting a spring-loaded safety valve, four pressure terms are important:
- Set pressure (activation pressure): the pressure at which the valve begins to open. This is the specified setting of your safety valve.
- Operating pressure (working pressure): the maximum pressure during normal operation. Maintain a minimum margin of 10% below the set pressure to prevent premature activation (simmer).
- Reseating pressure: the pressure at which the valve is fully closed again after activation — approximately 10% below the set pressure for gases and approximately 20% for liquids.
- Design pressure: the maximum pressure permitted in your system. Your set pressure must be at least 10% below the design pressure.
What should you consider during installation?
Install the safety valve as close as possible to the installation. A long pipeline between the installation and the valve causes pressure drop during discharge, which negatively affects capacity and performance.
Consider the discharge piping carefully. The pressure drop in this piping must not become excessive. Pay attention to the direction of the discharge line: a safety valve for compressed air with a discharge line directed towards a solid wall can generate sufficient reaction force during discharge to unscrew the valve from its fitting.
Does your installation also require check valves as part of the pressure management system? Ebora is happy to advise on the complete installation configuration. Select the correct spring-loaded safety valve based on medium, set pressure and discharge capacity, or request a quotation directly via the contact form.
Frequently asked questions
Should I replace a safety valve after it has activated?
Yes, Ebora recommends replacing a safety valve after it has activated. Following discharge, the seal on the disc may have been compromised, which can result in leakage past the valve. Only replacement or overhaul can continue to guarantee the safety of the system.
When should I choose a bellows version?
Choose a spring-loaded safety valve with an internal bellows when back pressure is present on the discharge side of the valve — for example due to a long or rising discharge line. Without a bellows, back pressure shifts the activation point of the valve, compromising the reliability of the protection.
Which certificate is required for a safety valve on pressure vessels in the EU?
For pressure vessels and systems falling under the European Pressure Equipment Directive (PED 2014/68/EU), a CE-marked safety valve is required. Ebora supplies spring-loaded safety valves with PED certification from Goetze, Spirax Sarco and ARI Armaturen. Please contact us for the exact documentation requirements for your application.
