Cast Steel Gate & Globe Valves
In a pressure seal gate valve, the bonnet seal is designed to tighten as internal pressure rises. At high pressure and temperature this gives more reliable sealing than a bolted bonnet, together with a more compact and lighter body.
Overview
Pressure seal gate valves are used in Class 900, 1500 and 2500 on high-pressure steam, boiler feedwater and power plant main and auxiliary lines. Chromium-molybdenum cast steels (WC6, WC9, C12A) are preferred for high-temperature strength; for material designations, see our guide to reading valve material codes.
Technical specifications
| classe de pression | ASME Class 900, 1500, 2500 |
|---|---|
| End connections | Mainly butt-weld (BW); RTJ flanged option |
| Materials | WCB, WC6, WC9, C12A; F22 / F91 (forged) |
| Garniture | Hard-faced (Stellite) seats and wedge |
| Operation | Gear operator, multi-turn electric actuator; bypass and drain options |
Key features
- Bonnet seal that tightens with pressure
- Cr-Mo materials for high temperature
- Optional bypass line and warm-up connection
- Butt-weld ends suited to power plant and boiler lines
Catalog data
- Application: on Class 900, 1500 and 2500 gate valves, the body-bonnet joint is usually a pressure seal design; in Class 150–600, a bolted bonnet is standard.
- Sealing: as internal pressure rises, the bonnet seal is compressed harder; at high pressure and temperature the joint is more reliable and more compact than a bolted flange connection.
- Materials: A216 WCB, A217 WC6, WC9, C12A and A351 CF8M; trim 5, 8 or 12 (hardfaced).
- Face-to-face: ASME B16.10; butt-weld (BW) ends are the most common option on power plant steam lines.
Trim options (API 600)
Trim is the material combination of the internal parts in contact with the fluid: wedge (or disc), seat and stem. Stating the trim number in the inquiry and the order defines the internal materials in a single line:
| Trim no. | Wedge / disc face | Seat face | Stem | Service typique |
|---|---|---|---|---|
| 1 | 13Cr | 13Cr | 13Cr (F6a) | Water, air, general service |
| 2 | 304 (18Cr-8Ni) | 304 | 304 | Mildly corrosive service |
| 5 | CoCr hardfacing (Stellite) | CoCr hardfacing | 13Cr | High temperature, steam, erosive fluids |
| 8 | 13Cr | CoCr hardfacing | 13Cr | Hydrocarbons and steam; the most common trim for carbon steel valves |
| 10 | 316 (18Cr-8Ni-Mo) | 316 | 316 | Corrosive service |
| 12 | 316 | CoCr hardfacing | 316 | Corrosive and erosive service |
| 13 | Alloy 20 (19Cr-29Ni) | Alloy 20 | Alloy 20 | Sulfuric acid and similar aggressive media |
| 16 | CoCr hardfacing | CoCr hardfacing | 316 | Severe corrosive and erosive service |
The table lists the most common trims. For the full API 600 trim table (1–18) or special trims, send us your specification.
Documentation and testing
On industrial projects the documentation package matters as much as the valve. We confirm the certificate and test scope for every line item at quotation stage:
- EN 10204 3.1 material certificates for pressure-retaining and wetted parts, traceable by heat number
- EN 10204 3.2 with third-party inspection, on request
- Pressure test reports to API 598 or EN 12266-1: shell, seat and, where specified, gas tests
- Fire-test certificates (API 607 / ISO 10497) for fire-safe type-tested designs
- PMI reports for alloy and stainless materials
- Dimensional, visual and coating inspection records
- PED 2014/68/EU CE declaration for equipment within its scope
- NACE MR0175 / ISO 15156 compliance statement for sour (H₂S) service
Technical datasheet
Foire aux questions
What is the advantage of a pressure seal valve?
Internal pressure compresses the bonnet seal, so sealing improves as pressure rises. Because no large bolted flange is needed, the body is more compact and lighter in high classes.
Why is a bypass used on large high-pressure valves?
To equalize the pressure difference across the closed valve before opening and to warm up the line in a controlled way. This reduces opening torque and seat wear and prevents thermal shock.
Produits associés
API 600 Cast Steel Gate Valve
2″–42″, Class 150–900; OS&Y, flexible wedge, API trim options.
View details
API 6D Slab Gate Valve
Full bore suitable for pigging; pipeline and station service.
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BS 1873 Cast Steel Globe Valve
Bolted and pressure seal bonnet; flat or plug disc, backseat, Stellite trim.
View detailsRequest a quote: Pressure Seal Gate Valve
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