High Pressure Globe Valve
Valves / Globe ValveA high-pressure globe valve is designed for service at Class 600 through Class 2500 (and above), handling extreme pressure differentials in power generation, petrochemical, and oil and gas applications where reliable shut-off and throttling are critical.
Working Principle
The valve operates as a standard globe valve with a disc lifting off and lowering onto a seat. The high-pressure design incorporates several critical enhancements: pressure seal bonnet (above Class 600) where line pressure forces the bonnet against a metallic seal ring, heavier wall sections per ASME B16.34, and seat designs that resist the wire-drawing erosion caused by high-velocity leakage at extreme differential pressures. Stellite or tungsten carbide hard-facing on disc and seat surfaces is standard. The body may use forged construction for smaller sizes or heavy-wall castings for larger sizes. Balanced disc designs are common at very high differential pressures to keep actuator forces manageable.
Key Components
Heavy-wall body (forged or cast), pressure seal bonnet, disc (hard-faced or balanced design), seat ring (hard-faced, replaceable), stem (high-strength alloy), graphite packing with live-loading, handwheel or actuator.
Types & Variants
| Type | Key Feature | Typical Use |
|---|---|---|
| Pressure seal HP globe | Pressure seal bonnet, Class 600-2500 | Power plant main steam isolation |
| Balanced HP globe | Balanced disc for high DP | Hydroprocessing isolation, high DP throttling |
| Forged HP globe | Forged body, small bore | Instrument and drain on high-P headers |
| Welded bonnet HP globe | Welded body-bonnet, zero leak path | Lethal/toxic high-pressure service |
Common Materials
ASTM A217 WC9 (2.25Cr-1Mo) for steam service up to 538°C. ASTM A217 C12 (9Cr-1Mo) for higher temperatures. ASTM A182 F22/F91 for forged bodies and pressure seal components. Disc and seat hard-facing: Stellite 6 or 12, tungsten carbide, or 13Cr hardened. Stem: F6a (410SS) or F22 with Stellite overlay.
Applicable Standards
- API 602 (forged globe valves)
- ASME B16.34 (pressure ratings)
- API 600 (reference design)
- MSS SP-93 (pressure seal valve requirements)
Industrial Applications
- Power plant main steam and reheat isolation
- Boiler feedwater system isolation
- Refinery hydroprocessing unit isolation (high H2 pressure)
- High-pressure chemical reactor isolation
- Compressor station blowdown and vent
- Offshore high-pressure injection systems
Advantages & Disadvantages
Advantages
- Handles extreme pressure differentials reliably
- Pressure seal bonnet eliminates gasket leak path at high pressure
- Hard-faced seats resist wire-drawing erosion from high-velocity leakage
- Balanced designs available for manageable actuator forces at very high DP
Disadvantages
- Heavy and expensive — high-pressure construction adds significant cost and weight
- Pressure seal bonnet requires special tooling for maintenance
- Not suitable for frequent cycling — hard-faced seats wear faster under repeated impact
- Longer lead times due to specialized materials and manufacturing
Selection Guide
- Always specify pressure seal bonnet for Class 600 and above in high-pressure service
- Stellite 6 hard-facing on both disc and seat is the minimum for high-pressure throttling duty
- For differential pressures above 50 bar, consider balanced disc design to reduce actuator size
- Live-loaded graphite packing is essential to prevent packing leakage during thermal cycling
Practical Tips
- Wire-drawing is the biggest enemy of high-pressure globe valves — even a tiny leak at 150 bar cuts through untreated seat faces in hours. Hard-facing is not optional
- When sizing actuators for high-pressure globe valves, always include a 30% margin for seat breakout friction after long periods of inactivity
FAQ
What is wire-drawing in a high-pressure valve?
Wire-drawing is erosion caused by high-velocity fluid leaking through a partially open or damaged seat. At high differential pressures, even a tiny gap creates jet velocities that cut through seat metal like a water jet cutter. Hard-facing (Stellite, tungsten carbide) is essential to resist this.
Pressure seal vs bolted bonnet at high pressure?
Pressure seal is preferred at Class 600 and above. Line pressure itself keeps the bonnet seal tight, eliminating the gasket that is the weak point of bolted bonnet designs. Pressure seal also reduces body weight and simplifies maintenance (no bonnet bolts to remove under pressure).