TÜV-SV1090 S/G

Safety valves are a key part of every pressure system – they provide the controlled release of excess medium pressure from a boiler, vessel or pipe. Without a properly working safety valve, excessive pressure can seriously damage equipment (by bursting a pressure vessel or pipe, for example) and create danger for operators and the surroundings. For these reasons it is essential to use quality, certified safety valves. Safety valves certified to TÜV-SV1090 S/G meet strict safety and performance requirements for media in the gaseous state, including hot steam. Every safety valve bought from us is supplied set to the required opening pressure and sealed, so it is ready for immediate installation in your system.

What TÜV certification and the TÜV-SV1090 S/G designation mean

TÜV (Technischer Überwachungsverein) is an independent German testing organisation for technical inspection and certification. TÜV certification of safety valves means the valve has undergone strict third-party type testing and meets the standards laid down for safe operation. The designation TÜV-SV1090 S/G is a specific TÜV type approval for safety valves intended for steam (S) and gaseous media (G – Gase). The abbreviation SV stands for the German „Sicherheitsventil“ (safety valve). The letter S comes from the designation for steam and G from the German „Gase“ (gases), so the certification covers use of the valve for hot steam and technical gases alike. The number 1090 is the identification number of the certification report. A valve with this designation has been type-approved by TÜV for use on gaseous media (including steam) and meets the requirements of the relevant regulations (the AD 2000-Merkblatt standards for safety valves and the European Pressure Equipment Directive PED 2014/68/EU, for example). It therefore also carries CE marking and compliance with applicable pressure equipment legislation is guaranteed.

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Typical uses of TÜV-SV1090 S/G safety valves

Safety valves certified to TÜV-SV1090 S/G are intended above all for gaseous media and steam. Typical applications cover a wide range of equipment and industrial plants where the system must be protected against a dangerous rise in gas or steam pressure:

• Steam boilers and heating systems: Ensuring safety in steam boilers, heat exchangers and systems with hot steam. The safety valve protects the boiler or pipework from excessive steam pressure – if the permitted pressure is exceeded the valve opens and releases some of the steam, preventing an explosion of the boiler or pipe. Such valves are used in industrial boiler houses, thermal power stations, steam-heated plants or sterilisers and autoclaves.
• Compressors and air systems: Protecting compressed air pressure vessels (receivers) and compressor outlet pipework. S/G safety valves are commonly installed on compressor stations and air receivers in workshops and industry to prevent the safe air pressure being exceeded. If the compressor control fails or the gas heats rapidly, the valve opens and blows off the overpressure to atmosphere, protecting the vessel from bursting.
• Tanks and distribution systems for technical gases: Safety relief in systems with technical gases (nitrogen, carbon dioxide, argon and other inert gases, or flammable gases such as propane). Examples include pressurised gas tanks in industrial plants, pipework for compressed gases, or tanks in food production (CO₂ for carbonating drinks and the like). The safety valve prevents a dangerous rise in pressure caused, for instance, by the gas warming or a fault in the filling system. With flammable gases (LPG, CNG and so on) a working safety valve is critically important to prevent an explosion if the tank overheats.
• Gas cylinders and mobile pressure tanks: Some portable pressure cylinders and gas tankers are fitted with S/G-certified safety valves for protection during external heating or fire. Large industrial oxygen or nitrogen cylinders, or mobile tankers with liquefied gases, may have safety valves that open and release gas when the pressure rises above the safe limit. That prevents catastrophic failure of the cylinder through gas expansion.

Design features and material particularities of TÜV-SV1090 S/G valves

Design: Safety valves certified to TÜV-SV1090 S/G are generally direct-acting spring valves in an angle design (inlet from below, outlet to the side). This proven arrangement makes it easy to connect a discharge pipe to lead the medium safely into a suitable space when the valve opens. The valve consists of a body, a closing disc (seat) with a seal, a spring calibrated to the given opening pressure and usually also a manual lever for function testing. The spring presses on the closing element and keeps the valve shut until the medium pressure on the seat exceeds the force of the set spring. Once the opening pressure is exceeded, the valve opens suddenly (fully on full-lift valves, gradually on proportional ones) and releases the excess gas or steam.

Body materials: The body of a safety valve is made of quality metallic materials resistant to gases and high temperatures – most often brass, bronze (gunmetal) or stainless steel. For ordinary applications (compressed air, nitrogen) brass or bronze valves are often used, offering good corrosion resistance and pressures up to tens of bar. For more demanding conditions, particularly with hot steam or aggressive gases, stainless steel valves are preferred, tolerating high temperatures better (steam can reach 200 °C) and highly resistant to corrosion (from steam condensate, acidic gas components and so on). A quality metal valve body provides sufficient strength under pressure and a long service life.

Seal and seat: To achieve high tightness when closed, safety valves for gases and steam tend to have a soft seat with a durable seal. Different seal materials are used depending on the medium and operating temperature:

• For ordinary compressed air and inert gases at lower temperatures, NBR (nitrile rubber) or a similar elastomer is often sufficient – such a seal seals reliably and is usable to roughly 80 °C.
• For hot steam and higher gas temperatures, more heat-resistant elastomers are chosen, such as EPDM (ethylene propylene rubber) usable to about +150 °C, or FKM (Viton), a fluoroelastomer suitable for temperatures around +160 to +180 °C and also resistant to oils or fuels contained in the gas.
• For very high temperatures and universal chemical resistance, PTFE (Teflon) or a similar polymer is ideal – a PTFE seal withstands temperatures around +200 °C and does not degrade even in hot steam. A PTFE seat is used, for instance, on valves that must cover the whole range from low pressures up to ~40 bar and temperatures to 200 °C.

With a suitably chosen seal, safety valves achieve practically zero leakage of medium when closed (up to a pressure just below the set opening value). That matters for gases too – it prevents losses of expensive medium, a drop in system pressure or unwanted gas emissions into the surroundings. Every valve has important data stamped on the body (set opening pressure, TÜV certification mark, material designation and so on) for easy identification during inspections and checks.

Spring cover: On safety valves for steam and gases the spring chamber is often vented (an open cover or a cover with discharge holes). That means when the valve opens, gas or steam can partly flow out around the spring through small openings, which prevents pressure building up in the spring space and keeps the valve's operation unaffected. Some versions instead have a closed cover or use a bellows – chosen where escape of medium into the surroundings through the spring space must be entirely prevented (with toxic or expensive gases, or to eliminate the effect of back pressure at the outlet). Most standard S/G valves, however, have an open or vented cover, because escaping gas or steam during occasional blow-off does not present the risk that liquids do.

Quality requirements and standards: TÜV-SV1090 S/G certification guarantees that the valve met strict requirements in the type test. That test verifies correct function – above all the accuracy of opening at the rated pressure, flow stability and closing after the pressure drops – as well as sufficient flow capacity for the medium. The tests also verify the valve's mechanical resistance under repeated pressure loading and the tightness of the seat. The valves must comply with the relevant standards, such as EN ISO 4126-1 (the European standard for the design and testing of safety valves) and the German AD 2000-Merkblatt regulations mentioned. Part of the quality requirements is compliance with the European PED directive – the valve maker is supervised by a notified body (TÜV, for example) and every valve is supplied with a declaration of conformity (CE). In practice that means a valve certified to TÜV-SV1090 S/G is safe, reliable and ready for service in industrial equipment (or another pressure system) without further individual testing. The user has the certainty that the valve meets all legislative requirements and technical standards for the area of use.

Advantages of using TÜV-SV1090 S/G certified valves

Using a safety valve with this certification brings a number of advantages for operators of steam and gas systems:

• High safety and reliability: Independent TÜV certification gives certainty that the valve meets all relevant safety standards. The risk of failure is minimised – the valve opens exactly at the set pressure when needed and thereby protects your equipment from overpressure. Strict quality control eliminates the possibility of the valve failing to open in time or, conversely, letting gas through when it should not.
• Tightness when closed: Quality machining of the seat and a suitable seal guarantee that the valve does not leak medium during normal operation. With gases that means savings – no loss of compressed medium or energy occurs (with steam, a leaking valve would lower the pressure and waste heat). It also increases the safety of the surroundings, because no gas or steam escapes into the plant room until the critical pressure is reached.
• Accurate pressure setting: Certified valves are set precisely to the required opening pressure. They open on reaching the calibrated value with a very small tolerance and, once the overpressure has been blown off, close tightly again as soon as the pressure falls below the closing value (usually slightly lower than the opening value – the blowdown). They thereby keep the system within a safe pressure range and prevent both over-pressurisation and too-frequent blow-off (the valve does not discharge needlessly often, only at genuinely excessive pressure).
• Compliance with regulations (CE/PED): A valve carrying the TÜV-SV1090 S/G certificate automatically meets the requirements of the European PED 2014/68/EU directive and bears CE marking. You need not fear problems during regular inspections of technical equipment – using such a valve complies with all mandatory standards from a legislative point of view. That is fundamental, for instance, for pressure systems supervised by inspection authorities.
• Build quality and long service life: Certified valves are made by reputable manufacturers (HEROSE among others) from first-class materials. Investing in a quality safety valve pays off – the valve keeps its setting accuracy and seat tightness over a long period of service. Durable materials such as stainless steel and top-grade springs ensure the valve resists corrosion, material fatigue and wear from repeated opening. Thanks to the high quality, intervals for mandatory re-testing or maintenance can be extended, reducing operating and downtime costs.

Recommendations for choosing a safety valve (practical tips)

When choosing a safety valve for steam or gas certified to TÜV-SV1090 S/G, consider several important aspects:

• Determining the medium and certification type: Make sure the valve you choose matches the medium in your system. For steam and compressed gases the right choice is a valve with S/G (steam/gas) certification, such as TÜV-SV1090 S/G. If you need to protect a system with a liquid (water or oil, for instance), choose a valve certified for liquids instead (such as TÜV-SV581 F-2 intended for liquid media). Other type designations of safety valve also exist – TÜV-SV749 D/G-2, for example – covering specific ranges or combinations of media. Always choose a valve with the certification appropriate to the nature of the medium and the operating conditions in your equipment.
• Set pressure: Choose the correct opening (set) pressure for the valve. It should be somewhat higher than the maximum normal working pressure of the system, but not higher than the maximum allowable pressure of the protected equipment (MAWP). The safety valve is usually set about 10 % above the normal working pressure so that it does not act under normal conditions yet opens reliably if the pressure rises dangerously. We supply the safety valves in our range already set to the required pressure at the works – so when ordering it is enough to state the opening pressure you need. Never adjust the valve yourself; any interference with the spring calibration would invalidate its certification and could endanger operational safety.
• Flow capacity: Every safety valve has a certain flow capacity – the maximum quantity of medium it can release per unit of time when open. In practical terms it is important for the valve's capacity to exceed the maximum possible inflow or generation of excess medium in your system during an emergency. On a steam boiler, for instance, the valve must be able to release as much steam as the boiler can generate in a fault (or as much as evaporates on overheating). On a compressor the valve must release at least the air flow the compressor can deliver when running unloaded. Valve data sheets usually give flow figures for air or steam at various pressures – compare them with the requirements of your system, or contact us for help calculating the capacity needed.
• Size and connection: Choose a suitable valve bore (DN) and connection type. Most smaller safety valves for steam and gas have a threaded connection (a male thread G 1/2", G 3/4" and so on) that should match the connection on your boiler, vessel or pipe. For larger flows or industrial boilers, flanged valves in larger sizes (DN 50, DN 100) are available. Make sure the valve fits dimensionally at the installation point – check the space for its height, any lever and the discharge direction. Correct sizing also matters for function itself: too small a valve might not keep up with releasing pressure, while too large a valve may be needlessly expensive and seal less well at low load.
• Material resistance: If you work with a specific medium or demanding conditions, verify the body and seal material of the valve for chemical and thermal resistance. For ordinary dry air or clean steam, standard bronze/brass valves with a Viton or EPDM seal suffice. In more demanding conditions – for aggressive gases (containing corrosive impurities) or high-temperature steam – choose a stainless steel valve with PTFE or a special high-temperature seal. If the medium contains oxygen (O₂) or other highly reactive gases, make sure the valve is suitable for it (for oxygen, degreased valves free of oil residues and with compatible materials are used). The right choice of material extends the valve's life and ensures safe operation without corrosion or degradation damage to the seal.
• Correct installation: In practical terms we recommend installing the safety valve as close as possible to the protected vessel or equipment, ideally on a vertical outlet pointing upwards. The valve should be upright unless another position is expressly permitted by the maker – vertical mounting ensures the valve is not affected by gravity or deposits. No shut-off fitting (cock or valve) that could close off the path to the safety valve may be placed between the valve and the protected equipment. Lead the valve outlet (discharge) to a safe place – either upwards into the open air at a safe location, or by connecting a discharge pipe that vents out of the room. With steam, the discharge is often led into a vertical pipe ending in a safety discharge head; with gases it is led outside the enclosed space so that an explosive or asphyxiating atmosphere cannot accumulate. When releasing steam, protect personnel from scalding; when releasing gases, ensure sufficient ventilation. Also remember to remove any transport plugs or opening covers before commissioning a new valve, if it has them, so that the passage of medium is fully assured.

If you are unsure about the right choice of safety valve, use our advice centre – the article „How to choose the right safety valve“ gives detailed advice and explains all the important parameters. You are of course also welcome to contact us directly for expert consultation; we will gladly help you select the optimal solution tailored to your equipment. With a quality safety valve certified to TÜV-SV1090 S/G you gain certainty of safe operation and long-term protection of your technology.