Safety Valves · Balanced Bellows Safety Valves
Type 441/442 Balanced Bellows Safety Valves
The Type 441/442 balanced bellows safety valve is a full-lift, rolled-seat execution whose bellows balances back-pressure out of the set-pressure equation: the same nominal set point holds whether the outlet sees atmosphere or a superimposed built-up back-pressure. The benchmark execution covers DN 20 to DN 400 (NPS 3/4 to 16), set pressures from 0.1 to 49 bar CE / 1 to 49.3 bar ASME, and a temperature window of -270 to 450°C CE / -268 to 538°C ASME across orifices F to X.
Part of the Balanced Bellows Safety Valves family
Last updated: 2026-11
Specifications
| set pressure range | 0.1–49 bar (CE) / 1–49.3 bar (ASME), 1.5–710 psig / 15–715 psig |
|---|---|
| pressure class | PN 10 - PN 40 (DIN EN 1092) / Class 150 - Class 300 (ASME B16.5) |
| size range | DN 20 to DN 400, NPS 3/4 to NPS 16 |
| capacity orifice | F to X |
| body materials | Gray cast iron, Nodular cast iron, Carbon steel, Stainless steel |
| end connections | Flanged — DIN EN 1092 (DN 20 to DN 400) or ASME B16.5 (NPS 3/4 to NPS 16) |
| temperature range | -270 to 450 °C (CE) / -268 to 538 °C (ASME) |
| design | Full lift safety valve with rolled seat |
| flange class | PN 10 - PN 40 (DIN EN 1092), Class 150 - Class 300 (ASME B16.5) |
| bellows material | Stainless steel, Elastomer |
| seat gasket | Metallic, Sealing plate, O-Ring |
| body material grades | 0.6025, 0.7043, 1.0619, 1.4408, Gr. 60-40-18, SA 216 WCB, SA 351 CF8M |
| flow diameter d0 | 18 - 295 mm | 0.71 - 11.61 in |
| overpressure | 5% pressure increase |
Application & selection guidance
Choose the DIN EN 1092 PN 10-40 or ASME B16.5 Class 150-300 flange set against the piping standard, then size the orifice (F to X) for the required capacity at set pressure. Body materials span gray and nodular cast iron, carbon steel and stainless steel in listed grades (0.6025, 0.7043, 1.0619, 1.4408, Gr. 60-40-18, SA 216 WCB, SA 351 CF8M); bellows are stainless steel or elastomer, with metallic, sealing-plate or O-ring seat gaskets to match temperature and tightness requirements.
Frequently asked questions
What does the balanced bellows do in a safety valve?
The bellows isolates the disc and guide area from outlet pressure, so back-pressure — superimposed or built-up — no longer offsets the set point. The valve pops at its set pressure even where the discharge line runs at elevated pressure.
What size, set-pressure and temperature range does the Type 441/442 cover?
DN 20 to DN 400 (NPS 3/4 to 16) with orifices F to X; set pressure 0.1-49 bar in the CE configuration and 1-49.3 bar (1.5-710 psig) in the ASME configuration; service temperature -270 to 450°C CE / -268 to 538°C ASME.
Which flange standards and body materials are offered?
Flanges per DIN EN 1092 PN 10-40 or ASME B16.5 Class 150-300. Bodies in gray cast iron, nodular cast iron, carbon steel or stainless steel — listed grades include 0.6025, 0.7043, 1.0619, 1.4408, Gr. 60-40-18, SA 216 WCB and SA 351 CF8M — with stainless steel or elastomer bellows and metallic, sealing-plate or O-ring seat gaskets.
Ordering & documentation
Documents
Ask for the documentation set you need with the inquiry — typical items for this execution (material certificates, test reports to the listed inspection standard, dimensional drawings) are confirmed and supplied with the quotation.
Quotation
A quotation-ready inquiry states: nominal size and pressure rating, body and seat material preference, end connection, operation, and the service medium with temperature. Typical values on this page are benchmark reference ranges; the binding values are confirmed at quotation.
Sample & supply
Supply terms, order quantities and lead time are agreed per order — state the destination country and required schedule with the inquiry.
Storage & shipping
Store valves with seats and seals protected from UV, ozone and deformation, keep end-face protectors on until installation, and for elastomer- or PTFE-seated executions avoid prolonged outdoor storage — seat compounds age fastest in direct sunlight and freezing conditions.
Knowledge: selection guides
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