D343H Triple Eccentric Hard-Seal Butterfly Valve – Flanged, Bidirectional, High-Temperature
The Gaoshan D343H is a bidirectional triple eccentric hard-seal butterfly valve designed for demanding industrial applications. Rated PN2.5 to PN40 and available in sizes DN50–DN2000, it features a laminated metal seat disc rated to 425°C and a triple-offset design that eliminates seat contact during operation. This results in zero friction, extended service life, and reliable tight shut-off for steam, high-temperature oil, corrosive media, and natural gas. Available with flanged (D343H) end connections in cast steel or stainless steel.
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Product Details
The D343H triple offset (triple eccentric) flanged butterfly valve is the metal-seated butterfly for service where elastomers fail: steam and hot oil to 425°C, pressures to PN40, in a flanged body from DN50 to DN2000. Three eccentricities lift the disc clean of the laminated metal seat through the stroke, giving friction-free, bidirectional tight shut-off.
- Triple offset geometry: zero seat friction, bidirectional pressure-assisted seal
- Laminated stainless + graphite metal seat, continuous service to 425°C
- Flanged to GB/T 9113; PN2.5–PN40; DN50–DN2000
- Worm gear standard; pneumatic (D643H) or electric (D943H) on request
- WCB cast steel or stainless (CF8/CF8M) body; duplex optional
- CE-marked; API 6D; designed & tested to JB/T 8527 / GB/T 13927
Product Overview
The D343H is the flanged version of Gaoshan’s triple-offset hard-seal family (the butt-weld version is the D363H). The triple-offset geometry means the disc contacts the seat only in the final degrees of closure, eliminating rubbing wear and keeping torque low, while the laminated metal seat tolerates temperature cycling that cracks solid metal or elastomer seats.
Body and disc are WCB cast steel as standard with stainless and duplex options; the seat laminate can be all-stainless for high temperature or PTFE for chemical service. Worm gear is standard, with pneumatic and electric actuated variants for automated lines.
Model Designation Guide
| Model Code | Pressure | Size Range | End Connection | Drive |
|---|---|---|---|---|
| D343H-10C / 16C | PN10 / PN16 | DN50 – DN2000 | Flanged (GB/T 9113) | Worm gear handwheel |
| D343H-25C / 40C | PN25 / PN40 | DN50 – DN1600 | Flanged (GB/T 9113) | Worm gear handwheel |
| D643H (Pneumatic) | PN10 – PN40 | DN50 – DN600 | Flanged | Pneumatic actuator |
| D943H (Electric) | PN10 – PN40 | DN50 – DN1600 | Flanged | Electric actuator 380V/220V |
Why Triple Offset Seals Better
Three Eccentricities, Zero Friction
Two offsets move the disc axis off the stem and seat axes; the third makes the sealing surfaces conical. The disc lifts clear on opening and touches the seat only at final closure – no rubbing wear, low torque.
Bidirectional, Pressure-Assisted
The conical metal seal tightens as differential pressure rises in either direction, giving zero-leakage class shut-off both ways.
Laminated Seat for Thermal Cycling
The stainless + graphite laminate flexes to conform to the seat and absorbs thermal cycling that cracks a solid metal seat – why it holds on steam and hot oil that cycle daily.
Metal Seat Where Elastomers Fail
At 425C and in abrasive or hydrocarbon service an EPDM/PTFE seat ages quickly; the metal laminate does not.
Materials of Construction
| Component | Standard | Optional |
|---|---|---|
| Body (阀体) | Cast Iron / Cast Steel (WCB) | Stainless Steel (CF8, CF8M) |
| Disc (蝶板) | Cast Steel | Stainless Steel; Duplex SS |
| Shaft (阀杆) | Cast Steel | Stainless Steel (316) |
| Seat Ring (阀座) | Carbon Steel | Stainless Steel; PTFE-lined; Rubber-lined |
| Laminated Disc Seal | Stainless steel + Flexible Graphite laminate | All-SS laminate (high-temp); PTFE laminate (chemical) |
| Stem Packing | Flexible Graphite | PTFE; PTFE + Graphite composite |
Design & Inspection Standards
| Design / Manufacturing | Flange Connection | Face-to-Face Length | Pressure Test & Inspection |
|---|---|---|---|
| JB/T 8527 | GB/T 9113 | GB/T 12221 | GB/T 13927 |
International Standards & Certification
- CE-marked and API 6D licensed; designed and tested to JB/T 8527 / GB/T 13927.
- EN 593 / API 609 compliance available on request – state the code your project is inspected against.
- Material certificates to EN 10204 3.1 supplied with delivery.
Connection Dimensions (Flanged)
Full PN10/PN16/PN25/PN40 dimension tables (DN50–DN2000) are supplied with the quotation; the excerpt below shows the PN16 series. D = flange OD, D1 = bolt PCD, H0 = face-to-face, H = height, G = gear diameter.
| DN | L | D | D1 | D2 | f | b | Z-Φd | H0 | H | A | B | G |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 50 | 100 | 165 | 125 | 102 | 3 | 18 | 4-Φ18 | 82.5 | 195 | 50 | 144 | 180 |
| 65 | 112 | 185 | 145 | 122 | 3 | 18 | 4-Φ18 | 92.5 | 215 | 50 | 144 | 180 |
| 80 | 120 | 200 | 160 | 138 | 3 | 20 | 8-Φ18 | 125 | 240 | 62 | 200 | 300 |
| 100 | 127 | 220 | 180 | 158 | 3 | 20 | 8-Φ18 | 110 | 235 | 50 | 144 | 220 |
| 125 | 140 | 250 | 210 | 188 | 3 | 22 | 8-Φ18 | 125 | 290 | 60 | 200 | 300 |
| 150 | 140 | 285 | 240 | 212 | 3 | 22 | 8-Φ22 | 100 | 310 | 63 | 200 | 300 |
| 200 | 152 | 340 | 295 | 268 | 3 | 22 | 8-Φ22 | 202 | 360 | 63 | 200 | 300 |
| 250 | 165 | 395 | 350 | 320 | 3 | 26 | 12-Φ22 | 235 | 395 | 80 | 230 | 350 |
Butterfly Family — Which Type to Specify
| Type | Models | Seat | Strength | Best For |
|---|---|---|---|---|
| Centerline wafer | D71X/D371X/D671X/D971X | Rubber (EPDM/NBR) | Lightest, lowest cost, PN10/16, to 135C | Water, HVAC, general |
| Double eccentric (HPBV) | D342/D642/D942 | Rubber / PTFE | Large bore to DN2000, low torque | Water, large mains |
| Triple offset (metal seat) | D343H/D363H | Laminated metal | High temp to 425C, high pressure | Steam, oil, high temp |
Structure Drawing
Installation & Maintenance
- Mount with stem horizontal or vertical: keep the gear clear for operation; large sizes need pipe support.
- Do not throttle with the gear closed hard: stop when resistance rises – the seal is torque-assisted.
- Keep the seat clean at commissioning: flush weld slag before first closure to protect the laminate.
- Inspect the laminate on shutdowns: check for delamination or scoring; the seat is replaceable in line.
Application Fields
The D343H is specified on steam and hot oil lines to 425C; refinery and petrochemical headers; power plant auxiliary systems; high-temperature gas and flue gas; large-diameter water where metal seating is required.
What We Need to Quote Your D343H Valves
- Size and pressure: DN50–DN2000, PN2.5–PN40.
- Medium and temperature: sets the seat laminate (all-SS / PTFE / graphite).
- Body material: WCB / stainless / duplex.
- Drive: worm gear standard; pneumatic D643H / electric D943H on request.
- Code: JB/T 8527 standard; EN 593 / API 609 on request.
Frequently Asked Questions
What is a triple offset (triple eccentric) butterfly valve?
A butterfly valve with three geometric offsets so the disc lifts clear of the seat during the stroke and contacts it only at final closure – friction-free, bidirectional metal-to-metal tight shut-off for high temperature and pressure that destroy elastomer seats.
When do I need triple offset instead of double eccentric?
When temperature, pressure or abrasion rule out an elastomer seat – typically steam/hot oil above ~150C, high pressure, or abrasive media. Double eccentric (HPBV) covers water and large bores with a soft seat; triple offset is the metal-seated high-service answer.
Is it bidirectional?
Yes – the conical metal seal is pressure-assisted in both directions, giving zero-leakage shut-off regardless of flow direction.
Flanged or butt-weld – which do I need?
This page is the flanged D343H. The butt-weld version for welded piping is the D363H. Same triple-offset sealing, different end connection.
Can it be actuated?
Yes – worm gear is standard; pneumatic (D643H) and electric (D943H, 380/220V) variants are available to PN40. Tell us the supply and fail position.
What temperature can it handle?
Continuous service to 425C with the stainless + graphite laminated seat; all-SS laminate for higher, PTFE laminate for chemical service.
Get a Quote & Technical Support
Gaoshan Valve has manufactured industrial valves since 1975 and holds ISO 9001/14001/45001, CE (EU PED) and API 6D certification, an approved supplier to Sinopec, CNPC and State Grid, exporting to more than 30 countries. Reply within 24 hours.
