Pressure Seal Bonnet Valves for High-Pressure Service

Pressure seal bonnet valves are designed for high-pressure service above ASME Class 600. The unique pressure-energized sealing mechanism makes them suitable for power generation, petrochemical, and oil and gas applications at extreme pressures.

Pressure Seal Principle

Unlike bolted bonnet valves where gasket compression is provided by bolting, pressure seal bonnets use the process pressure itself to energize the seal. As internal pressure increases, the pressure seal gasket is forced outward against the body seating surface, creating a tighter seal at higher pressures.

Design Advantages

• Seal improves automatically as pressure increases

• Bonnet can be removed for inspection without full valve disassembly

• Compact design compared to bolted bonnets at high pressure

• Lower body weight for the same pressure rating

• Well-suited for Class 900 through Class 4500 ratings

Gasket Materials

Pressure seal gaskets are typically made from iron or soft steel for carbon steel bodies, and from austenitic stainless steel or alloy materials for stainless and alloy bodies. The gasket must be softer than the body and bonnet seating surfaces to conform and seal effectively.

Applications

• Boiler main steam and hot reheat lines (Class 1500 to 2500)

• High-pressure feedwater systems

• High-pressure hydrocracker and reactor feed systems

• Gas injection wellhead equipment

Maintenance Considerations

Pressure seal gaskets are single-use items and must be replaced each time the bonnet is removed. Body and bonnet seating surfaces must be inspected and reground if damaged. Special procedures are required for assembly to achieve proper gasket positioning and initial compression.

Standards

Pressure seal bonnet valves are manufactured in accordance with ASME B16.34, API 600 (gate), API 603, and manufacturer-specific standards. Material and dimensional requirements follow the same specifications as bolted bonnet valves of the same pressure class.