A28H Spring Full Lift Safety Valve with Lever
Gaoshan A28H is a spring full lift safety valve with lifting lever — a threaded pressure relief valve that pops fully open for rapid, high-capacity overpressure discharge on boilers, compressors and steam lines.
• Full lift disc (≥¼ throat diameter) — fast mass relief where low-lift valves can only weep
• Lifting lever lets you pop-test the disc on site without dismantling the valve
• Set pressure 0.1 – 6.4 MPa across PN10 – PN64, DN15 – DN80 threaded ends
• Discharge ≤1.03 × set pressure; reseats tight at ≥90% of set pressure
• 50CrVA spring calibrated to your set pressure and sealed — no field adjustment
• 2Cr13 stainless disc & seat; ductile iron or WCB body; ≤200 °C for steam, air and water
• All-stainless variant for corrosive media available on request
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Product Details
The A28H is a spring full lift safety valve with lifting lever — a threaded-body pressure relief valve whose disc opens to full lift (≥1/4 of throat diameter) for rapid, high-capacity overpressure discharge on boilers, compressors, small vessels and steam/air/water lines. Set pressure 0.1–6.4 MPa across PN10–PN64 classes, DN15–DN80, ≤200 °C. Every A28H is calibrated to the ordered set pressure, sealed before dispatch, and the lifting lever lets you pop-test the disc on site without dismantling. Factory direct from Gaoshan Valve.
What the Model Code Means
| Symbol | Meaning |
|---|---|
| A | Safety valve |
| 2 | External threaded connection |
| 8 | Full lift structure (A27H low lift differs by this digit) |
| H | Stainless steel (2Cr13) sealed disc & seat |
| −10/16/25/40/64 | PN10 – PN64 pressure class |
What Is a Full Lift Safety Valve
In a full lift safety valve the disc opens to at least a quarter of the throat diameter, giving a rapid, full-pop discharge with high relief capacity in a compact threaded body. That is the difference between venting an overpressure event and merely weeping it: where a low-lift pattern bleeds pressure proportionally, the A28H dumps the surplus fast and then reseats at ≥90% of set pressure. It is the correct choice when the protected equipment — small boilers, compressors, receivers, hot-water generators — can build pressure faster than a low-lift valve can drain it.
The Lifting Lever — Manual Pop Test on Site
The integrated lifting lever lets an operator raise the disc manually against the spring — the standard way to verify the valve is free and seats correctly during periodic boiler and system inspections, without dismantling or overpressurizing the line. Release the lever and the disc reseats tight. This is the defining A28H feature over the plain A27H pattern.
Key Features
Calibrated & Sealed 50CrVA Spring
The alloy spring is precision-calibrated to your ordered set pressure and sealed before dispatch — adjust nothing in service; the set pressure is your first specification parameter.
Wide Set-Pressure Spectrum — 0.1 to 6.4 MPa
PN10 to PN64 classes cover set pressures from 0.1 MPa on low-pressure heating circuits to 6.4 MPa on high-pressure air and gas systems, DN15–DN80 threaded.
Tight Reseating — ≥90% of Set Pressure
After relieving, the valve closes at ≥90% of set pressure and discharge stays ≤1.03 × set pressure, so the system keeps working steam instead of losing it.
Corrosive-Media Variant
All-stainless body and internals are available for acids and aggressive fluids where a cast iron or WCB body would corrode — ask for the Y-P/R series.
Pressure Test Data — A28H Series
| Parameter | A28H-10 | A28H-16 | A28H-25 | A28H-40 | A28H-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 |
| Discharge Pressure | ≤ 1.03 × set | ≤ 1.03 × set | ≤ 1.03 × set | ≤ 1.03 × set | ≤ 1.03 × set |
| Reseating Pressure | ≥ 90% of set | ≥ 90% of set | ≥ 90% of set | ≥ 90% of set | ≥ 90% of set |
| Working Temperature | ≤ 200 °C | ≤ 200 °C | ≤ 200 °C | ≤ 200 °C | ≤ 200 °C |
| Applicable Medium | Steam | Steam | Steam | Steam | Steam |
⚠️ Data verification note: the source data sheet on this page was labeled A27H — the values above must be confirmed against the official A28H factory datasheet before publication (opening height, discharge coefficient and seal-test details especially).
Materials for Main Parts
| Part | Material |
|---|---|
| Body & bonnet | Cast iron (PN10) / ductile iron QT450 (PN16) / WCB cast steel (PN25–PN64) |
| Disc & seat | 2Cr13 stainless steel |
| Spring | 50CrVA alloy steel, calibrated & sealed |
| Lifting lever | Carbon / stainless steel |
| Corrosive variant | All-stainless body & internals |
Dimensions & Weight
| DN (mm) | d0 (mm) | R (thread) | L (mm) | L1 (mm) | G (thread) | ≈H (mm) |
|---|---|---|---|---|---|---|
| 15 | 10 | ½” | 40 | 65 | ½” | 140 |
| 20 | 15 | ¾” | 40 | 65 | ¾” | 140 |
| 25 | 20 | 1″ | 40 | 76 | 1″ | 155 |
| 32 | 25 | 1¼” | 55 | 85 | 1¼” | 177 |
| 40 | 32 | 1½” | 62 | 90 | 1½” | 215 |
| 50 | 40 | 2″ | 67 | 110 | 2″ | 225 |
| 65 | 50 | 2½” | 76 | 128 | 2½” | 283 |
| 80 | 65 | 3″ | 110 | 140 | 3″ | 370 |
d0 = throat diameter; R = inlet thread; L = inlet face-to-face; L1 = outlet face-to-face; G = outlet thread; H = overall height. Confirm against the factory datasheet.
Full Lift vs Low Lift — A28H vs A27H
| Factor | A28H Full Lift (this page) | A27H Low Lift |
|---|---|---|
| Opening height | Full pop (≥¼ throat) | Proportional, minimal lift |
| Discharge capacity | High — rapid mass relief | Lower — bleeds pressure gradually |
| Lifting lever | Fitted — manual pop test | Not fitted |
| Best for | Boilers, compressors, fast pressure build-up | Small vessels, tight spaces, gradual loads |
Need flanged ends or all-stainless construction? See the A48Y flanged full lift safety valve and the A42Y full lift series; for compact low-lift duty see the A27H low lift safety valve and A41H.
Design & Testing Standards
- Design & manufacture: GB/T 12243 (spring loaded safety valves)
- Face-to-face: GB/T 12250 · Threaded ends: GB/T 7306 / ISO 7-1
- Test & inspection: GB/T 12251 · ISO 9001 quality management system certified
- TS special equipment manufacturing license
- 100% hydrostatic shell test at 1.5× rated pressure; 100% seat leakage test; Y-series air vent function test per batch
Installation & Maintenance
- Install vertically at the protected vessel with the outlet pointed to a safe discharge location; never isolate the valve in service.
- Exercise the lifting lever periodically (at ~75% of operating pressure) to confirm free movement and clean seating.
- Never exceed the set pressure adjustment — the spring is calibrated and sealed at the works.
- Steam service: fit a drain at the inlet low point so condensate cannot pool on the disc.
Application Fields
- Small boilers and hot-water generators
- Air compressors and receivers
- Steam mains, drip legs and tracing lines
- Pressurized water and thermal-oil circuits
- Compact skids and OEM equipment requiring overpressure protection
What We Need to Quote Your Safety Valve
- Set pressure (first parameter) and required back pressure
- Medium (steam / air / water) and temperature
- Required discharge capacity or heating duty
- Inlet / outlet thread standard and size (DN15–DN80)
- Body material: cast iron, ductile iron, WCB or all-stainless
- Quantity and delivery site
Frequently Asked Questions
What is the difference between the A28H full lift and A27H low lift safety valve?
Both are spring-loaded threaded safety valves. The A28H opens to full lift (≥¼ of the throat diameter) for rapid, high-capacity relief and carries a lifting lever for manual testing; the A27H opens proportionally with minimal lift for compact duty. Full lift protects equipment that builds pressure fast; low lift suits gradual overpressure with limited space.
What is the lifting lever for?
The lever lets you lift the disc manually — the standard periodic check that the spring and disc are free and the seat is tight — without dismantling the valve or overpressurizing the system. Release it and the disc reseats under spring force.
How is the set pressure calibrated?
You order the valve by set pressure (0.1–6.4 MPa across PN10–PN64). Each A28H is calibrated on a test rig, then the adjusting screw is sealed so the setting cannot drift in service. State the set pressure as your first specification parameter when ordering.
What media and temperature can it handle?
Steam, air and water up to 200 °C as standard, with 2Cr13 stainless disc and seat. For corrosive media, all-stainless body and internals are available on request.
Threaded or flanged — which body do I need?
The A28H is threaded (screwed) ends for compact DN15–DN80 lines. For flanged connections, see the A48Y flanged full lift safety valve or the A42Y full lift series.
Protecting a boiler, compressor or receiver?
Send Gaoshan Valve your set pressure and medium for a factory-direct A28H full lift safety valve quote.
