Flanged Safety Valves
Flanged safety valves are spring-loaded, proportional-lift safety fittings that discharge the fluid when the set pressure is exceeded at high-capacity points such as steam boilers, hot water and thermal oil installations, pressure vessels and process lines. Inlet and outlet are flanged and the valve is bolted into the pipeline.
Bodies are made of grey cast iron in PN16, and of cast steel or cast stainless steel in PN40; sizes range from DN15 to DN100. Depending on size and spring, the set pressure can be chosen from about 0.2 bar up to 40 bar. The design is based on EN ISO 4126-1 and AD 2000-A2; type-approved versions are certified separately for steam, gas and liquid discharge. Bellows and closed-lever versions are available as options.
Main Applications
- Steam boilers and superheated steam lines
- Hot water and thermal oil circuits
- Pressure vessels, reactors and autoclaves
- Outlet side of pressure reducing stations
- Gas and compressed air distribution lines
Technical Data
| Connection | Flanged inlet and outlet; raised face form B1 |
|---|---|
| Flange standard | PN16: EN 1092-2 · PN40: EN 1092-1 |
| Sizes | DN15 … DN100 |
| Lift type | Proportional lift, spring-loaded |
| Set pressure | About 0.2–40 bar (by size and spring); bellows types about 3–40 bar |
| Cast iron temperature | −10 / +300 °C |
| Cast steel temperature | −10 / +450 °C (down to −60 °C at reduced pressure) |
| Stainless temperature | −60 / +400 °C |
| Design basis | EN ISO 4126-1, AD 2000-A2, VdTÜV 100 |
| Type approval | Separate for steam/gas (D/G) and liquid (F) |
| Gasket | Pure graphite (CrNi reinforced) |
| Options | EPDM bellows (−10 / +120 °C), balanced stainless bellows, closed lever |
Material Options
| Part | PN16 · grey cast iron | PN40 · cast steel | PN40 · stainless |
|---|---|---|---|
| Body | EN-GJL-250 (EN-JL1040) | GP240GH+N (1.0619+N) | GX5CrNiMo19-11-2 (1.4408) |
| Seat | X6CrNiMoTi17-12-2 (1.4571) | X6CrNiMoTi17-12-2 (1.4571) | X6CrNiMoTi17-12-2 (1.4571) |
| Disc | X39CrMo17-1+QT (1.4122) | X39CrMo17-1+QT (1.4122) | X6CrNiMoTi17-12-2 (1.4571) |
| Spring | 51CrV4 (1.8159) | 51CrV4 (1.8159) | X10CrNi18-8 (1.4310) |
| Bonnet | EN-GJL-250 | Depending on model | GX5CrNiMo19-11-2 (1.4408) |
| Adjusting screw | X20Cr13+QT (1.4021) | X20Cr13+QT (1.4021) | X2CrNiMo17-12-2 (1.4404) |
| Body gasket | Pure graphite | Pure graphite | Pure graphite |
Material note: Valves with grey cast iron (EN-JL1040) bodies are not used in steam boiler plants covered by TRD 110; cast steel or stainless bodies must be chosen there. At low temperatures (below −10 °C) a steel body requires A4-70 studs and nuts. The inlet pipe must not be smaller than the valve size; suitable flange gaskets should be used for the flange joints.
Advantages
High Capacity
- Flanged bodies up to DN100.
- A single valve may be enough on large boilers and vessels.
Wide Temperature
- Up to 450 °C with a steel body.
- Suitable for superheated steam and thermal oil.
Stainless Internals
- Seat 1.4571, disc 1.4122 or 1.4571.
- Resistance to erosion and corrosion.
Type Approval
- Separate certificates for steam, gas and liquid.
- Easier documentation for inspections.
Optional Features
- Bellows, balanced piston, closed lever.
- Adapts to back pressure or dirty media.
Construction and Design Features
- Flanged angle body with spring bonnet on top
- Stainless seat and disc, adjustable spring
- Pure graphite body gasket
- Open or closed lifting lever
- Optional EPDM or stainless bellows protecting the spindle
Send the vessel design pressure, fluid, temperature and discharge flow through the Request a Quote form; we will select the flanged valve by body material, size and spring range.
How to Choose?
- Start from design pressureThe set pressure must not exceed the maximum allowable pressure of the vessel.
- Determine discharge flowCalculate the required flow from boiler capacity or the fire case.
- Choose size and certificateConfirm the size with the approved discharge coefficient for steam/gas or liquid.
- Match body to temperatureCast iron up to 300 °C, steel up to 450 °C, stainless for corrosive media.
- Assess back pressureIf the discharge line has back pressure, prefer the bellows version.
Complementary Products
Why ORFA?
Types of Flanged Safety Valves
Other Safety Valves
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