Pressure Seal Globe Valve

A Pressure Seal Globe Valve is a type of valve used in high-pressure and high-temperature applications, typically found in power plants, oil & gas, petrochemical, and other heavy-duty industrial settings.

What is a Pressure Seal Globe Valve?

A globe valve controls fluid flow through a linear motion of a disc or plug against a stationary seat. The pressure seal design refers to how the valve bonnet (top cover) seals against the valve body: the higher the internal pressure, the tighter the seal.

Key Features

• Pressure Seal Bonnet: Unlike bolted bonnets, pressure seal bonnets improve the seal as internal pressure increases, making them ideal for high-pressure systems (e.g., ANSI Class 900–2500).

• Linear Motion: The valve opens and closes by raising and lowering a plug, providing good throttling and shutoff capabilities.

• Globe Valve Body: Provides a tortuous flow path, which adds resistance but gives better control compared to gate valves.

• Seats & Disc Options: Typically include hard-faced options (like Stellite) for durability in severe service.

Advantages

• High Pressure & Temperature Capability

• Enhanced Seal Integrity at High Pressure

• Excellent Flow Control (throttling)

• Low Maintenance (compared to bolted bonnets)

Common Applications

• Steam systems

• High-pressure water systems

• Nuclear power plants

• Refineries and chemical plants

Common Materials

• Body: Carbon Steel, Alloy Steel, Stainless Steel

• Seat/Disc: Stellite, Hardened Alloys

• Bonnet: Pressure seal design (typically forged or cast)

Absolutely! Here’s a more detailed breakdown of Pressure Seal Globe Valves, including construction, working principle, pressure classes, maintenance considerations, and standards.

Detailed Construction of a Pressure Seal Globe Valve

Working Principle

1. Manual or Actuated Operation – The handwheel or actuator moves the stem up or down.

2. Linear Motion – The stem moves the disc toward or away from the seat.

3. Flow Control – The flow is throttled or stopped as the disc closes against the seat.

4. Pressure Seal Effect – As internal pressure rises, it forces the bonnet gasket tighter into its seat, enhancing sealing without needing excessive bolting.

Pressure Classes (ASME)

Pressure Seal Globe Valves are typically rated under ASME B16.34 and available in:

Actual pressure-temperature ratings vary by material group (per ASME B16.34 tables).

Maintenance Considerations

• Less frequent gasket maintenance due to pressure seal bonnet.

• Special tools or techniques may be needed to reseat or replace internal parts due to the compact and rugged design.

• Hard-facing wear surfaces reduces need for frequent replacement in high-pressure, erosive services.

Relevant Standards

• ASME B16.34 – Valves – Flanged, Threaded, and Welding End

• API 600 / API 602 – Steel globe and gate valves for refinery and petrochemical service

• MSS-SP-144 – Pressure seal bonnet valves

• BS 1873 – Steel globe and globe stop check valves

Comparison with Other Valve Types

Common Variants

• T-Pattern Globe Valve (standard flow path, best shutoff)

• Y-Pattern Globe Valve (lower pressure drop)

• Angle Pattern (90° turn, for space-saving installation)