A42Y Seal Type Spring Full Lift Safety Valve (PN16/PN25, DN40–DN100)
A42Y Seal Type Spring Full Lift Safety Valve for air, gas, petroleum, water, and non-corrosive media.
- Available in A42Y-16C, A42Y-16Q, and A42Y-25 models
- Enclosed bonnet with full lift design for high discharge capacity and piped exhaust option
- Pressure ratings PN16/PN25; sizes DN40–DN100; working temperature ≤300°C
- WCB cast steel or ductile cast iron body with Stellite hard-faced disc and seat ring
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Product Details
The A42Y seal-type spring full-lift safety valve is the premium flanged overpressure valve: an enclosed bonnet that lets discharge be piped to a safe location, combined with a full-lift disc for maximum capacity and a Stellite hard-faced seat for gas, petroleum, air and water service to 300°C. PN16/PN25, DN40–DN100.
- Flanged spring-loaded safety valve, full-lift for maximum discharge
- Enclosed (sealed) bonnet — discharge piped to a safe location
- Stellite hard-faced disc and seat for long cycle life
- PN16/PN25, DN40–DN100, to 300°C
- WCB cast steel or QT450-10 ductile iron body; 50CrVA calibrated spring
- CE-marked; China Safety Valve Manufacturing License; designed & tested to GB/T 12243
Product Overview
The A42Y is a flanged spring-loaded safety valve for air, natural gas, petroleum and water at temperatures to 300°C. When system pressure exceeds the set point the spring-loaded disc lifts to full travel for maximum discharge capacity, and reseats automatically when pressure normalizes — no manual reset.
The enclosed bonnet is the defining feature: instead of venting to the surrounding air, the discharge is routed through a piped outlet to a safe collection or recovery point. That is what specifications require for hazardous, toxic or valuable media, and for indoor plant where atmospheric venting is not permitted.
Body material follows the duty: WCB cast steel for higher temperature and pressure, QT450-10 ductile iron as the cost-effective option for standard service. The Stellite sealing surfaces and 2Cr13 internals hold a tight seal through thousands of cycles, and the 50CrVA spring is calibrated to the set pressure and sealed before dispatch.
Key Advantages
Maximum Discharge (Full Lift)
The disc opens to full travel, giving the largest flow area for rapid relief — essential on boilers and large vessels where a fast overpressure must be vented quickly.
Piped, Controlled Discharge
The sealed bonnet routes discharge to a safe remote point rather than the room — required for hazardous or valuable media and indoor plant.
Stellite Sealing for Cycle Life
Stellite hard-facing gives exceptional wear, corrosion and erosion resistance under repeated actuation.
Calibrated 50CrVA Spring
The alloy spring holds the set pressure consistently and reseats tightly; adjustable screw allows on-site calibration within the rated range.
Two Body Materials
WCB cast steel for strength and temperature; QT450-10 ductile iron for cost-effective standard duty.
Fine Pressure Gradation
Multiple working-pressure steps within PN16/PN25 ensure an exact match to the system set pressure, without compromising safety margin.
Pressure Test Data & Set Pressure Range
| PN | Strength Test (MPa) | Working Pressure Classes (MPa) | Working Pressure Classes (MPa) | Working Pressure Classes (MPa) | Working Pressure Classes (MPa) | Working Pressure Classes (MPa) | Working Pressure Classes (MPa) |
|---|---|---|---|---|---|---|---|
| PN16 | 2.4 | 0.1–0.13 | 0.13–0.16 | 0.16–0.2 | 0.2–0.25 | 0.25–0.3 | 0.3–0.4 |
| PN16 | 2.4 | 0.4–0.5 | 0.5–0.6 | 0.6–0.8 | 0.8–1.0 | 1.0–1.3 | 1.3–1.6 |
| PN25 | 3.8 | 1.6–2.0 | 1.6–2.0 | 1.6–2.0 | 2.0–2.5 | 2.0–2.5 | 2.0–2.5 |
| Working Temp | ≤ 300°C | ≤ 300°C | ≤ 300°C | ≤ 300°C | ≤ 300°C | ≤ 300°C | ≤ 300°C |
| Applicable Media | Air, Natural Gas, Petroleum, Water, Non-Corrosive Media | Air, Natural Gas, Petroleum, Water, Non-Corrosive Media | Air, Natural Gas, Petroleum, Water, Non-Corrosive Media | Air, Natural Gas, Petroleum, Water, Non-Corrosive Media | Air, Natural Gas, Petroleum, Water, Non-Corrosive Media | Air, Natural Gas, Petroleum, Water, Non-Corrosive Media | Air, Natural Gas, Petroleum, Water, Non-Corrosive Media |
Materials for Main Parts
| Part Name | Material |
|---|---|
| Body | WCB Cast Steel / QT450-10 Ductile Cast Iron |
| Disc, Seat Ring, Adjusting Ring, Guide Sleeve, Adjusting Screw, Stem, Valve Guide | 2Cr13 / Stainless Steel |
| Bonnet, Cap of Valve | WCB Cast Steel / Ductile Cast Iron |
| Spring | 50CrVA Alloy Spring Steel |
| Disc & Seat Ring Seal Surface | Stellite Hard-Facing Alloy |
Dimensions & Weight
| DN (mm) | d0 | L | D | K | g | b | Z-φd | D1 | Kt | gl | bt | Dt | Z′-φd | H | H1 | Wt (kg) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 40 | 25 | 120 | 150 | 110 | 88 | 18 | 4-φ18 | 165 | 125 | 102 | 18 | 50 | 4-φ18 | 272 | 110 | 18 |
| 50 | 32 | 135 | 165 | 125 | 102 / 20 ▲ | 18 / 20 ▲ | 4-φ18 | 185 | 145 | 122 | 18 | 65 | 4-φ18 | 332 | 130 | 22 |
| 65 | 40 | 150 | 185 | 145 | 122 / 22 ▲ | 18 / 22 ▲ | 4-φ18 / 8-φ18 ▲ | 200 | 160 | 138 | 20 | 80 | 8-φ18 ▲ | 366 | 130 | 24 |
| 80 | 50 | 170 | 200 | 160 | 138 / 24 ▲ | 20 / 24 ▲ | 8-φ18 | 220 | 180 | 158 | 20 | 100 | 8-φ18 | 478 | 150 | 42 |
| 100 | 65 | 205 | 235 / 236 ▲ | 180 / 190 ▲ | 158 / 162 ▲ | 20 / 24 ▲ | 8-φ18 / 8-φ22 ▲ | 250 | 210 | 188 | 22 | 125 | 8-φ18 | 627 | 180 | 70 |
Inlet flange columns D/K/g/b/Z-φd; outlet flange columns D1/K1/g1/b1/D1′/Z′-φd. Marked values differ for PN25. Certified drawings issued with the quotation; state set pressure when enquiring.
Gaoshan Safety Valve Series — Which Model
| Model | Lift | Bonnet | Seal | DN Range | Best For |
|---|---|---|---|---|---|
| A47H | Low lift | Open | 2Cr13 | DN32–DN150 | General steam / water relief |
| A48Y | Full lift | Open | Stellite | DN32–DN150 | Boilers, large vessels — high capacity |
| A41H | Low lift | Sealed | 2Cr13 | DN40–DN100 | Water / air / oil — piped discharge |
| A42Y | Full lift | Sealed | Stellite | DN40–DN100 | Gas / petroleum — max safety + capacity |
This page is the A42Y. For the other lift/bonnet/seal combinations see the series table and the safety valve series.
Structure Drawing
Design, Testing and Reference Standards
- CE-marked and manufactured under the China Safety Valve Manufacturing License; designed and tested to GB/T 12243.
- EN ISO 4126 and, for US codes, ASME BPVC Section VIII compliance available on request — state the code your project is inspected against.
- Material certificates to EN 10204 3.1 and a set-pressure certificate supplied with each calibrated valve.
Installation & Maintenance Guidelines
- Mount vertical at the top of the protected volume: no isolating valve upstream; the valve must see system pressure directly.
- Pipe the discharge: route the enclosed outlet to a safe location; support the pipe so no load reaches the valve.
- Never adjust in service: the set pressure is factory-calibrated and sealed; recalibrate at the interval your code requires.
- Test periodically: bench-test or raise to set at the inspection interval to confirm lift and reseat.
- Protect from condensate on steam: allow drainage so the valve is not waterlogged.
Application Fields
The A42Y protects gas and petroleum lines; compressor and air systems; pressure vessels; piped discharge where atmospheric venting is not permitted. Anywhere a trapped volume can exceed its rated pressure, the spring safety valve is the last line of defence.
What We Need to Quote Your A42Y Valves
- Size and pressure class: DN40–DN100, PN16/PN25.
- Set pressure (MPa): the key parameter — state it exactly.
- Medium and temperature: air, natural gas, petroleum and water, to 300°C.
- Body material: WCB cast steel or QT450-10 ductile iron.
- Bonnet: sealed (piped discharge) as standard.
- Code: GB/T 12243 standard; EN ISO 4126 / ASME on request.
- Documentation: EN 10204 3.1 + set-pressure certificate.
Frequently Asked Questions
Sealed (enclosed) bonnet or open bonnet – which do I need?
A sealed bonnet (A41H/A42Y) routes the discharge through a pipe to a safe point – required for hazardous, toxic or valuable media and indoor plant. An open bonnet (A47H/A48Y) vents to atmosphere – the economical choice for steam and water where that is safe. This page is the sealed-bonnet A42Y.
Full lift or low lift – which do I need?
Full lift (A48Y/A42Y) opens to full travel for maximum discharge – choose it for boilers and large vessels where a rapid overpressure must be vented. Low lift (A47H/A41H) opens proportionally in a smaller envelope for modest relief needs. The A42Y is full-lift.
What does the Stellite seat buy me?
Stellite (cobalt-based) hard-facing gives far better wear, erosion and corrosion resistance than plain 2Cr13 under repeated high-energy actuation – the choice for steam boilers and cycling service. 2Cr13 is fine for general steam/water.
How is the set pressure calibrated?
Each valve is calibrated to your stated set pressure and sealed before dispatch, with a set-pressure certificate. The adjusting screw allows on-site calibration within the rated range, but never adjust it in service.
Can it be used on corrosive media?
The A42Y covers air, natural gas, petroleum and water. For acids and aggressive fluids use the stainless A28Y/A27Y threaded series or a stainless flanged variant – tell us the medium.
What standards does it meet?
CE-marked and manufactured under the China Safety Valve Manufacturing License, designed and tested to GB/T 12243, with EN ISO 4126 and ASME BPVC Section VIII compliance available on request. State your code and we will confirm.
Request a Quote or Technical Consultation
Gaoshan Valve has manufactured industrial valves since 1975 and holds ISO 9001/14001/45001, is CE-marked and holds the China Safety Valve Manufacturing License, exporting to more than 30 countries. Reply within 24 hours. Contact us with your size, pressure class and exact set pressure for a calibrated A42Y quotation.
