Pressure Seal Bonnet (Cast Steel)

The Cast Steel Gate Valve with Pressure Seal Bonnet is a high-integrity isolation valve engineered specifically for elevated pressure and high-temperature service in power generation, oil and gas, and petrochemical applications. Unlike a conventional bolted bonnet where the sealing load is fixed at assembly, the pressure seal bonnet uses line pressure itself to energise the bonnet gasket, the higher the internal pressure, the tighter the seal becomes. This self-energising mechanism makes the pressure seal bonnet the preferred choice for Class 900 and above applications where a conventional bolted design would require excessively large fasteners and heavier construction to achieve equivalent sealing reliability. The result is a more compact, lighter valve body that maintains a leak-free bonnet joint throughout the full pressure and temperature operating cycle.

Features

• Self-energising pressure seal bonnet tightens progressively as line pressure increases, delivering superior bonnet joint integrity at high pressure without dependence on external bolt preload — eliminating the re-torquing maintenance requirement associated with bolted bonnet designs at elevated temperatures
• Seal-welded seat rings are permanently fused to the body bore, preventing inter-leakage between the seat ring and body and removing the risk of seat loosening or rotation in service under thermal cycling or pressure surge conditions
• Flexible wedge and split wedge configurations with balanced design absorb pipeline deflections and thermal deformation without transmitting bending loads to the seating faces, protecting seat integrity across wide temperature swings typical of steam and high-temperature hydrocarbon service
• One-piece cast flexible wedge minimises stress concentration across the wedge face, maintaining consistent seat contact pressure and reducing the risk of wedge cracking under repeated thermal and mechanical loading cycles
• Rising stem with trapezoidal threads and burnished finish provides low operating torque, positive visual open/closed indication, and extended stem thread life across the high-cycle operation common to power plant and process plant service
• Pillar yoke construction ensures clear access to the bonnet and gland packing area for routine re-packing and inspection on installed valves, reducing maintenance time and supporting compliance with fugitive emission requirements