3/4″-800LB-SW Bellows Seal Gate Valve
Description
Technical Data Sheet
Product: Bellows Seal Gate Valve
Model / Size: 3/4″ – 800LB – SW
1. Product Description
This valve adopts a bellows seal design, which fundamentally eliminates stem packing leakage commonly found in conventional gate valves. The bellows assembly, combined with the stem, forms a static seal. An additional packing box serves as a secondary backup seal, achieving a “zero leakage” stem sealing performance. It is suitable for severe service conditions including high temperature, high pressure, high vacuum, and toxic, flammable, or corrosive media.
2. Basic Parameters
| Item | Parameter |
|---|---|
| Nominal Size | 3/4 inch (DN 20) |
| Pressure Class | Class 800LB (equivalent to PN 140 ~ 160 bar, depending on standard) |
| End Connection | Socket Weld (SW) |
| Structure Type | Outside Screw & Yoke (OS&Y) / Solid Wedge |
| Stem Sealing | Bellows seal + auxiliary graphite packing |
3. Design Standards
| Item | Standard |
|---|---|
| Design & Manufacture | API 602 (Steel Gate, Globe and Check Valves for Petroleum and Natural Gas Industries – Compact Design) |
| Pressure-Temperature Rating | ASME B16.34 |
| End Connection (SW) | ASME B16.11 |
| Face-to-Face Dimension | ASME B16.10 / Manufacturer’s standard |
| Inspection & Testing | API 598 (or ISO 5208) |
| Bellows Testing | ISO 15848-1 (Fugitive Emissions Standard) |
4. Bill of Materials (Typical Configuration)
| Part Name | Material (Typical Options) | Remarks |
|---|---|---|
| Body | A105 / A182 F316 | Carbon steel / Stainless steel optional |
| Wedge | A105 + 13Cr / F316 | 13Cr or Stellite hardfacing on sealing faces |
| Seat Ring | Integral per API 602 | Stellite 6 hardfacing on body seat |
| Stem | A182 F6a / F316 | Precipitation hardened stainless / Austenitic SS |
| Bellows Assembly | SS304 / SS316L | Multi-ply formed, high cycle life |
| Bonnet | A105 / A182 F316 | Matching body material |
| Packing | Flexible Graphite | With corrosion inhibitor |
| Handwheel / Stem Nut | Carbon steel (or ductile iron) / Copper alloy |
5. Dimensions & Weight (Reference)
| Item | Value |
|---|---|
| Face-to-Face (L) | Approx. 117 mm (per API 602) |
| Handwheel Diameter (W) | Approx. 100 mm |
| Overall Height (H) | Approx. 240 mm |
| Socket Weld Bore (D) | Per ASME B16.11, socket depth approx. 10 mm |
| Approx. Weight | 5.5 ~ 7.5 kg (depending on material) |
6. Operating Conditions
| Item | Parameter |
|---|---|
| Suitable Media | Steam, thermal oil, toxic gases/liquids, corrosive media, hydrocarbons |
| Temperature Range (Carbon Steel) | -29°C ~ 425°C |
| Temperature Range (Stainless Steel) | -196°C ~ 538°C (cryogenic / high temperature) |
| Max. Allowable Pressure | Per ASME B16.34, Class 800LB at ambient temperature (38°C) approx. 13.8 MPa (138 bar) |
7. Testing & Inspection
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Shell Strength Test: 1.5 times rated pressure, no leakage.
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High-Pressure Seat Test: 1.1 times rated pressure.
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Low-Pressure Pneumatic Test: 0.6 MPa compressed air.
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Bellows Leak Test: Helium mass spectrometry, leakage rate < 1×10⁻⁶ Pa·m³/s (or meeting Class V sealing requirement).
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Operational Test: Valve cycled fully open/close under rated differential pressure.
8. Features & Benefits
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Zero Leakage Assurance: The bellows isolates the stem from the atmosphere, eliminating external stem leakage – ideal for stringent environmental applications.
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Long Service Life: High-cycle-life bellows design ensures reliability under frequent operation.
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Low Maintenance: Dual stem sealing (bellows + packing) provides a secondary seal in the event of bellows failure, ensuring system safety.
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High Temperature & Pressure Capability: Class 800 rating with socket weld ends is suitable for high-pressure steam and thermal oil systems.
Notes:
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Dimensions and weights are typical values based on API 602; actual values may vary slightly depending on manufacturer design (e.g., handwheel size, bonnet height).
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For NACE MR0175 (sour service) compliance, please specify when ordering.
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During installation, follow the approved Welding Procedure Specification (WPS) for socket weld connections to avoid welding stress that could affect bellows life.
