Safety valves for inert gases

Introduction to the use of inert gases

Inert gases are gases that under ordinary conditions barely react with the substances around them. Typical representatives are the noble gases and other stable gases – nitrogen is used most often, along with argon, helium or carbon dioxide (CO₂). Thanks to their non-flammability and chemical inertness, inert gases are widely used wherever unwanted reactions must be prevented: nitrogen creates a protective atmosphere in tanks (preventing oxidation or explosion), argon and CO₂ serve as shielding gas in welding, and helium finds use in cryogenic systems and in leak detection. An inert gas therefore creates a safe, stable environment where oxygen or other reactive gases could cause problems (corrosion, combustion and so on).

The most widespread inert gas in industry is nitrogen – used from chemical and food plants to laser cutting. Specialised valve models exist for nitrogen applications (see the safety valves for nitrogen category), but the principle of overpressure protection is the same for all inert gases. Even an inert gas under high pressure can present a danger, which is why safety valves are used in all pressure systems.

The importance and function of safety valves in gas systems

Every pressure system with gas (compressor, storage pressure vessel, pipe network, cryogenic tank and so on) must be protected against dangerous overpressure. Safety valves serve this purpose – safety devices that automatically release excess pressure out of the system as soon as the pressure reaches the set value. The valve then opens and releases some of the gas into the open (or into a safe pipe), preventing any further rise in pressure. It thereby protects your pressure system from damage or explosion. Without a safety valve, even an otherwise harmless inert gas could cause a serious accident during a sudden pressure rise. Safety valves are therefore an essential part of pressure equipment and their installation is often required by standards and law.

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Specific features of safety valves for inert gases

Safety valves intended for inert gases do not differ in operating principle from valves for other media – their task is to release overpressure reliably. They do, however, have certain particularities in materials and construction so as to be optimally adapted to a gaseous medium and to ensure maximum tightness and operating safety. Below are the main particularities of these valves:

• Valve body material (brass vs. stainless steel): For inert gases, valves of brass or stainless steel are most often used. Brass safety valves are widespread in ordinary compressed air and inert gas applications at ambient temperatures – brass is strong enough, resists corrosion in dry gases and is cost-effective. For more demanding conditions or higher environmental cleanliness, stainless steel valves are chosen. Stainless steel gives high corrosion resistance and allows the valve to be used across a wide temperature range (including very low ones). In some cases (a combination of high temperature and nitrogen or steam, for example) other materials such as bronze or cast iron may be used in safety valves, but for inert gases brass and stainless versions dominate in practice.

• Construction and tightness: Safety valves for gases are usually spring valves with a precisely set spring force determining the opening pressure. Leak resistance is important – gas has low viscosity and would easily pass through even a small leak. These valves therefore have a precisely machined seat and are often fitted with a soft seal (a PTFE ring, for example) on the seat face. That ensures the closed valve lets through practically no gas (until the opening pressure is reached). Good tightness matters not only for safety but for the economics of operation – it prevents unwanted losses of expensive gas through slow leakage.

• Cleanliness and preparation for a gas environment: Applications with inert gases (in food production, pharmaceuticals or electronics manufacturing, for example) place emphasis on system cleanliness. Safety valves for gases are therefore often supplied degreased and cleaned by the manufacturer, so that they release no impurities or production oil residues into the medium. Inert gases are not aggressive, but at very low temperatures even small impurities could cause freezing or abrasive damage to the seal. A clean valve design additionally guarantees that no unwanted particles enter the process (a tank of food-grade nitrogen, for instance).

Cryogenic version of inert gas valves

A separate category are safety valves for cryogenic gases – that is, for inert gases stored in liquid form at extremely low temperatures. A typical example is liquid nitrogen (about –196 °C) or liquid argon. Special cryogenic safety valves are used for these purposes, built to work reliably even in deep cold. The material of such a valve is exclusively quality stainless steel (brass would become brittle at cryogenic temperatures). The internal construction is also adapted: springs are of stainless or a special alloy (Inconel, for example) resisting embrittlement, and seals are of materials that retain elasticity in the cold (PTFE or other polymers intended for cryogenics). In construction, a cryogenic valve usually has an extended „neck“ or extension separating the valve mechanism from the coldest part – this helps keep the spring and adjusting elements at a somewhat higher temperature so that they do not freeze. It goes without saying that a cryogenic valve must also seal perfectly when closed, otherwise evaporating gas would escape continuously. You will find these cryogenic models in our range in the safety valves for cryogenic gases section, which allow overpressure to be released safely from vessels of liquid nitrogen or other liquefied gases.

Recommendations for choosing a safety valve for gases

When choosing a suitable safety valve for an inert gas, several important criteria must be taken into account. Every application may have specific requirements, but in general we recommend focusing on the following parameters:

• Medium and temperature: Be clear about which gas and in what conditions you will use the valve. You will choose a different version for compressed gas at room temperature (a brass valve suffices here) and a different one for a cryogenic liquid (here a stainless, cryogenic valve is necessary). Every valve has a manufacturer-specified operating temperature range – make sure your range (-20 °C to +50 °C for nitrogen, for example) falls within it.

• Set pressure (opening pressure): Safety valves are supplied set to a specific opening pressure (10 bar, for example). This pressure should match the maximum allowable pressure of your system. Check whether the valve type you have chosen covers the required value – valves have a certain range of adjustable pressures (5–16 bar, for instance). Always order the valve with the setting from the manufacturer/supplier, who will ensure precise adjustment and a seal preventing the setting being changed.

• Size and connection: The correct valve size and connection type matter. Smaller equipment uses threaded safety valves (typically G 1/4" to G 1" threads), while larger vessels and pipework use flanged valves. Check that the valve has the right thread or flange size for your equipment. The valve size (bore, designated DN) also relates to flow – a larger valve can release more gas per second when open. So if you have a large volume of gas, make sure the chosen valve has sufficient capacity (manufacturers state flow parameters).

• Material and version: As mentioned above, the choice of body material (brass, stainless) and seal must match the medium. For ordinary inert gases a standard brass valve with an NBR or PTFE seal suffices. For a more aggressive environment or very pure gases, consider a stainless valve. With liquid CO₂ or other gases that can cool sharply on expansion, again prefer stainless (because brass becomes brittle in the cold).

• Certification and documentation: A safety valve is a safety element that should be certified (TÜV, CE) for the given use. From reputable suppliers (such as ourselves) you receive complete documentation with the valve – a declaration of conformity, a certificate and a setting report for the safety pressure. That matters for inspections of pressure equipment and for your peace of mind that the valve has been tested and will work at the stated pressure.

🔎 Tip: If you are unsure of the right valve choice, read our detailed advice article How to choose the right safety valve, where all the important parameters and tips are set out step by step. You can also contact us at any time – we will gladly help with the choice. The complete range of all types of safety valve (for various gases, steam, water and so on) is in the main category Safety valves – all designs.

Advantages and limits of valves for inert gases

Advantages:

• Reliable protection of pressure systems: Quality safety valves intended for inert gases (from the reputable Herose brand, for example) provide safe release of overpressure and thereby protect your equipment from destruction. Thanks to a design specialised for a gaseous medium they respond precisely at the given pressure and minimise the risk of unwanted operator intervention.

• Optimised for gaseous media: Valves for inert gas have a seat and seal design tuned so that no gas escapes in normal operation. Compared with valves for liquids they tend to have finer springs and often softer sealing elements, ensuring tightness right up to the moment of opening.

• Long service life and low maintenance: Inert gases are non-corrosive and clean, so the valve is not exposed to an aggressive environment. That shows in its service life – no rusting or clogging with dirt occurs. The valves therefore need only minimal maintenance (just a periodic function check during vessel inspections).

• A wide range of versions: Many variants of safety valve are available for inert gases – from small threaded valves for cylinders and compressors to large industrial valves with flanges. You will easily find a suitable model for the particular pressure, flow and connection method. Moreover, one valve often covers several media: a safety valve set for nitrogen can usually be used for argon or helium too (inert gases behave similarly).

Limits:

• Intended only for specific media: Safety valves in this category are certified for inert gases (and possibly compressed air). They cannot be used for aggressive or flammable gases or for liquids they are not intended for. For oxygen, for instance, a valve that is degreased and made of materials suitable for O₂ must be used – a standard inert gas valve could present a risk in oxygen service. Always follow the manufacturer's recommendation about the medium the valve is approved for.

• Temperature limits: Every valve has a limited operating temperature range. Brass valves suit neither very low nor very high temperatures – they become brittle in frost and lose strength at high temperatures. For cryogenic conditions, therefore, always choose a stainless cryogenic valve. Conversely, some cryogenic valves may not be built for higher temperatures above 100 °C. Make sure the temperatures in your operation match the capabilities of the chosen valve.

• The need for regular inspections: Although inert gas itself causes no wear, a safety valve is a mechanical device and as such requires occasional checking. It is advisable to verify the valve's function during regular inspections of the pressure vessel (to the statutory intervals). The spring may change its characteristic slightly over time and the seal can age, so at inspections the valve is usually tested or replaced to maintain complete reliability.

• Possible operational limitations: When a large quantity of gaseous medium is released, very rapid cooling of the valve can occur (the expansion effect) along with intense noise from the escaping gas jet. These are features common to all gas safety valves – they must be allowed for during installation (leading the valve discharge into a safe outdoor space and fitting a silencer where necessary, for example).

Taken as a whole, safety valves for inert gases are a key element of protection in every pressure system with non-flammable gases. A correctly chosen and installed valve gives you safe operation without fear of an uncontrolled rise in pressure – so you can concentrate fully on using the inert gas in your process while safety is reliably taken care of.