A27H Spring Low Lift Safety Valve
• A27H-10/16Q/16C/25C/40C/64 spring low lift safety valve
• A27Y-25/40P/R series for corrosive media applications
• Threaded connection, DN15–DN80, working temperature ≤200°C
• Discharge coefficient 0.65, opening height ≥1/4 throat diameter
• For steam, water, air, and corrosive media overpressure protection
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Product Details
The A27H spring low-lift safety valve — a compact threaded pressure relief valve — protects small-diameter lines, vessels and equipment from overpressure on steam, water and air systems to 200°C. When pressure exceeds the set point the spring-loaded disc lifts automatically, vents the excess, and reseats when pressure normalizes. PN10 to PN64, DN15–DN80.
- Threaded (screwed) inlet/outlet: quick install on small lines, vessels, compact equipment
- PN10–PN64, set pressures 0.1–6.4 MPa, DN15–DN80, to 200°C
- 50CrVA alloy spring, precision calibrated, automatic reseating
- Low-lift design: rapid response, minimal lift, low seat wear
- Certified discharge coefficient 0.65; opening height ≥ 1/4 throat diameter
- A28Y/A27Y-P/R all-stainless variants for corrosive media
Product Overview
The A27H is a compact threaded pressure relief device. The low-lift disc opens proportionally and reseats tightly when pressure falls, giving reliable overpressure protection with minimal lift and low seat wear — suited to small vessels, boilers, compressors and compact equipment where space is limited.
Body material follows the service: cast iron or ductile iron for low-pressure steam and water, WCB cast steel to PN64, and the A28Y/A27Y-P/R all-stainless variants for corrosive chemicals. The 50CrVA spring is precision-calibrated to the set pressure and reseats automatically at ≥90% of set.
A safety valve is the last line of defence on a pressure system — it is not a control valve and must never be isolated or adjusted in service. Specify the set pressure at order; each valve is calibrated and sealed before dispatch.
Key Advantages
Compact Low-Lift Protection
The low-lift disc gives rapid, proportional relief in the smallest envelope, ideal for vessels and equipment with limited headroom.
Low Seat Wear
Minimal lift height reduces impact and wear on the seating surfaces, extending service life between calibrations.
Threaded, Tool-Light Installation
Screwed inlet and outlet fit small-diameter pipelines and vessels without flanges, cutting install time and cost.
Wide Set-Pressure Spectrum
PN10 to PN64 with set pressures 0.1 to 6.4 MPa covers low-pressure boilers to high-pressure air and gas.
Calibrated 50CrVA Spring
The alloy spring holds the set pressure consistently and reseats at >=90% of set, so the valve closes tight after relieving.
Corrosive-Media Variant
The Y-P/R all-stainless series handles acids and aggressive fluids where a carbon steel body would corrode.
Pressure Test Data
| Parameter | A27H-10 | A27H-16Q/16C | A27H-25C | A27H-40C | A27H-64 |
|---|---|---|---|---|---|
| Set Pressure Range (MPa) | 0.1 ~ 1.0 | 0.1 ~ 1.6 | 0.1 ~ 2.5 | 0.1 ~ 4.0 | 0.1 ~ 6.4 |
| Seal Test Pressure | When Ps < 0.3 MPa: Ps − 0.03 MPa; When Ps ≥ 0.3 MPa: 90% of set pressure | When Ps < 0.3 MPa: Ps − 0.03 MPa; When Ps ≥ 0.3 MPa: 90% of set pressure | When Ps < 0.3 MPa: Ps − 0.03 MPa; When Ps ≥ 0.3 MPa: 90% of set pressure | When Ps < 0.3 MPa: Ps − 0.03 MPa; When Ps ≥ 0.3 MPa: 90% of set pressure | When Ps < 0.3 MPa: Ps − 0.03 MPa; When Ps ≥ 0.3 MPa: 90% of set pressure |
| Discharge Pressure | ≤ 1.03 × set pressure | ≤ 1.03 × set pressure | ≤ 1.03 × set pressure | ≤ 1.03 × set pressure | ≤ 1.03 × set pressure |
| Reseating Pressure | ≥ 90% of set pressure | ≥ 90% of set pressure | ≥ 90% of set pressure | ≥ 90% of set pressure | ≥ 90% of set pressure |
| Opening Height | ≥ 1/4 throat diameter | ≥ 1/4 throat diameter | ≥ 1/4 throat diameter | ≥ 1/4 throat diameter | ≥ 1/4 throat diameter |
| Working Temperature | ≤ 200°C | ≤ 200°C | ≤ 200°C | ≤ 200°C | ≤ 200°C |
| Discharge Coefficient | 0.65 | 0.65 | 0.65 | 0.65 | 0.65 |
| Applicable Medium | Steam, Water, Air | Steam, Water, Air | Steam, Water, Air | Steam, Water, Air | Steam, Water, Air |
Materials for Main Parts
| Model | Body, Bonnet | Valve Disc, Seat | Spring | Application |
|---|---|---|---|---|
| A27H-10 | Cast Iron | 2Cr13 | 50CrVA | Steam, Water, Air |
| A27H-16Q | Ductile Cast Iron (QT450) | 2Cr13 | 50CrVA | Steam, Water, Air |
| A27H-16C / 25C / 40C / 64 | WCB Cast Steel | 2Cr13 | 50CrVA | Steam, Water, Air |
| A27Y-25P/R / 40P/R / 64P/R | Stainless Steel | Stainless Steel | 50CrVA | Corrosive Media |
Dimensions & Weight
| DN (mm) | d0 (mm) | R | L (mm) | L1 (mm) | G | ≈H (mm) |
|---|---|---|---|---|---|---|
| 15 | 10 | 1/2″ | 40 | 65 | 1/2″ | 140 |
| 20 | 15 | 3/4″ | 40 | 65 | 3/4″ | 140 |
| 25 | 20 | 1″ | 40 | 76 | 1″ | 155 |
| 32 | 25 | 1 1/4″ | 55 | 85 | 1 1/4″ | 177 |
| 40 | 32 | 1 1/2″ | 62 | 90 | 1 1/2″ | 215 |
| 50 | 40 | 2″ | 67 | 110 | 2″ | 225 |
| 65 | 50 | 2 1/2″ | 76 | 128 | 2 1/2″ | 283 |
| 80 | 65 | 3″ | 110 | 140 | 3″ | 370 |
R = inlet thread, G = outlet thread, d0 = throat diameter, L/L1 = lengths, H = overall height. Set pressure is calibrated to order; state it when enquiring.
Safety Valve, Relief Valve or Full/low Lift: Which to Specify
| Question | Answer / choice |
|---|---|
| Safety valve vs relief valve? | A safety valve opens rapidly with a pop action for gas/steam; a relief valve opens proportionally, usually for liquid. The A28H/A27H are spring-loaded safety (relief) valves for steam, air, water. |
| Full lift (A28H) or low lift (A27H)? | Full lift for maximum discharge and fast venting, with a test lever; low lift for compact, proportional relief on small vessels. |
| Threaded or flanged? | These are threaded (DN15-80). For larger or flanged lines see the A42Y/A47H/A48Y flanged series. |
| Corrosive media? | Use the A28Y/A27Y-P/R all-stainless variant. |
| Which standard? | Designed and tested to GB/T 12243; EN ISO 4126 / ASME VIII compliance on request – state your code. |
For the flanged safety valve range see the safety valve series.
Structure Drawing
Design, Testing and Reference Standards
- Design and testing to GB/T 12243; set pressure calibrated and valve sealed before dispatch.
- Seal test: Ps−0.03 MPa (Ps<0.3) or 90% of set; discharge ≤1.03× set; reseat ≥90% of set.
International Standards & Certification
- 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 supplied with delivery.
- Set-pressure certificate supplied with each calibrated valve.
Installation & Maintenance Guidelines
- Mount vertical, inlet at top of protected volume: a safety valve must see the system pressure directly, with no isolating valve upstream.
- Never adjust in service: the set pressure is factory-calibrated and sealed; field adjustment voids the calibration and the protection.
- Keep the discharge safe: route the outlet to a safe location; on steam, allow for condensate drainage so the valve is not waterlogged.
- Test periodically: raise system pressure to set (or bench-test) at the inspection interval to confirm lift and reseat.
- Recalibrate on schedule: springs relax over time; re-certify the set pressure at the interval your code requires.
Application Fields
The A27H protects small steam boilers and heaters; air and gas compressors; pressure vessels and tanks; pumps and pipelines; heat exchangers; commercial and industrial equipment. 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 Safety Valves
- Size and pressure class: DN15–DN80, PN10–PN64.
- Set pressure (MPa): the single most important parameter — state it exactly.
- Medium and temperature: steam, water, air, gas, or corrosive (Y-P/R).
- Body material: cast iron / ductile iron / WCB / stainless.
- Type: low-lift (A27H) or full-lift with lever (A28H).
- Code: GB/T 12243 standard; EN ISO 4126 / ASME on request.
- Documentation: EN 10204 3.1 + set-pressure certificate.
Send the vessel or line data sheet and the required set pressure and we will return a calibrated quotation within 24 hours. Drawings are in the download center and qualifications on the certifications page.
Frequently Asked Questions
What does a low-lift safety valve do?
It protects a pressure system by lifting automatically when pressure exceeds the set point, venting the excess, and reseating when pressure normalizes. Low-lift means the disc opens a small, proportional amount – compact and low-wear.
Low lift or full lift – which do I need?
Low lift (A27H) suits compact vessels with modest relief needs. Full lift (A28H) opens to full travel for maximum discharge and adds a manual test lever – choose it where a rapid overpressure must be vented quickly.
Why threaded instead of flanged?
Threaded connections fit small-diameter lines, vessels and compact equipment without flanges, cutting install time and cost. For larger or flanged lines use the A42Y/A47H/A48Y flanged series.
How is the set pressure calibrated?
Each valve is calibrated to your stated set pressure and sealed before dispatch, with a set-pressure certificate. Never adjust it in service; recalibrate at the interval your code requires.
Can it handle corrosive media?
Yes, with the A27Y-P/R all-stainless variant for acids and aggressive fluids; the standard A27H covers steam, water and air.
What standards does it meet?
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.
Get a Quote & Technical Support
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 A27H quotation.
