Self-energising pressure seal bonnet design for supercritical and ultra-high-pressure isolation where bolted bonnets cannot perform.
At Class 900 and above, the pressure seal bonnet design becomes superior to bolted bonnets. The internal pressure in the valve body acts on the back of the bonnet sealing ring, increasing bonnet sealing load as line pressure rises. This self-energising characteristic makes pressure seal valves inherently safer than bolted designs under high-pressure thermal cycling — explaining their universal adoption in power station main steam service.
VALVAX pressure seal gate valves are designed to ASME B16.34 and IBR approved for Indian power plant service. The forged chrome-moly or carbon steel body is machined from a single forging — eliminating the cast body porosity risk that exists in bolted-bonnet valves at these pressure levels.
| Parameter | Value |
|---|---|
| Design Standard | ASME B16.34 |
| Size Range | 2″ – 16″ (DN50 – DN400) |
| Pressure Class | ASME Class 900 – 2500 |
| Face to Face | ASME B16.10 |
| End Connections | BW / RTJ / RF |
| Body Material | WCB / WC6 / WC9 / CF8M / P91 |
| Gate / Stem | SS316 / 13Cr / Alloy 625 HF |
| Seat | Integral machined / Stellite 6 HF |
| Design Temp. | Up to 650°C (P91 / WC9) |
| Testing | API 598 / IBR |
| Certification | IBR Approved |
ASTM A216 WCB / ASTM A105
High-pressure oil, gas, and water service at Class 900–2500. Economical for lower temperature duty.
ASTM A217 WC6 / WC9 / P91
Supercritical and ultra-supercritical steam. P91 for the most demanding high-temperature duties above 565°C.
ASTM A351 CF8M
High-pressure corrosive and cryogenic applications at Class 900–2500 where alloy steel is unsuitable.
ASTM A890 4A
High-pressure offshore wellheads and subsea applications with chloride corrosion requirements.
Main steam isolation valves, boiler feed pump discharge, and turbine bypass in supercritical power plants.
Wellhead Christmas tree components, high-pressure manifold isolation, and HP separator block valves.
Hydrocracker and hydrotreater high-pressure hydrogen service at Class 1500 and 2500.
Industrial cogeneration, waste-heat recovery, and process steam generation at supercritical conditions.
High-pressure wellstream isolation in duplex or 625 overlay trim for sour and chloride-rich environments.
Our IBR-approved engineering team will help you specify the correct class, material, and bonnet seal for your steam or process application.