Power Plant Steam Stop Valve -- Pressure Seal WC9
High-Pressure High-Temperature On/Off Valve for Thermal Power Plants
Document No.SV-DS-PWR-001
RevisionRev A
DateMay 2026
ManufacturerSupreme Valves India, Ahmedabad, Gujarat, India
This datasheet covers pressure seal globe valves in WC9 Cr-Mo steel for main steam isolation, turbine bypass, and boiler outlet stop service in thermal and combined-cycle power plants.
Technical Specifications
| Parameter | Specification |
|---|
| Valve Size Range | DN50 to DN400 (2" to 16") |
| Pressure Rating | Class 900 / Class 1500 / Class 2500 |
| Body Material | WC9 (2.25Cr-1Mo) cast steel, normalised and tempered |
| Plug / Seat Material | WC9 + Stellite 6 overlay, 13Cr hard-faced seat |
| Bonnet Seal | Pressure seal graphite ring + segmented thrust ring (no bolting) |
| Temperature Range | -29°C to +593°C (WC9 limit) |
| End Connections | Butt weld ASME B16.25, flanged ASME B16.5 (Class 1500/2500) |
| Operation | Gear operator, motorised actuator, or hydraulic actuator |
| Leakage Class | ANSI/FCI 70-2 Class V (metal seat) |
| Flow Characteristic | Quick-opening plug for on/off; modified equal-percentage for control |
Materials of Construction
| Component | Material |
|---|
| Body | WC9 (2.25Cr-1Mo) cast steel, normalised 920°C, tempered 720°C, hardness 180-220 BHN |
| Bonnet | WC9 pressure seal type with graphite seal ring and segmented thrust ring |
| Plug | WC9 with full Stellite 6 overlay on seat contact surface for erosion and galling resistance |
| Seat | Integral WC9 with Stellite 6 hard facing; replaceable seat ring on request |
| Stem | 17-4PH precipitation-hardened stainless steel for high-temperature strength and galling resistance |
| Packing | Pure graphite braided rings with Inconel wire reinforcement for 593°C service |
| Gaskets | Pure graphite pressure seal ring with anti-extrusion lip; no spiral winding required |
Testing & Inspection
| Test | Requirement |
|---|
| Test Standard | API 598 / ASME B16.34 pressure test |
| Certification | CE, PED, ISO 9001, IBR (Indian Boiler Regulations) |
Applicable Standards
| Standard | Description |
|---|
| Design Standard | ASME B16.34 / API 623 / IEC 60534 |
Notes
- Pressure seal bonnet must be re-tightened after first thermal cycle; follow OEM torque sequence provided in installation manual.
- WC9 material requires post-weld heat treatment (PWHT) after field welding; maintain 720°C ± 15°C for 2 hours per inch of thickness.
- Stellite 6 overlay hardness is 40-45 HRC; do not attempt in-line lapping -- replace trim if leakage exceeds Class V.
- For modulating control service, specify equal-percentage cage-guided trim with anti-cavitation diffuser.
- IBR Form III-C certificate and third-party inspection by IBR inspector required for boiler application; allow 3 weeks.
