Pressure Seal Gate Valve

• Pressure Seal Bonnet Valves: Pressure seal bonnet valves are a compact alternative to bolted bonnet designs, especially suitable for high-pressure applications. In a pressure seal valve, the bonnet closure assembly is designed so that internal fluid pressure acts on the bonnet, increasing the compressive load on the sealing gasket and creating a self-energizing seal. Unlike bolted bonnet designs, the sealing effectiveness of a pressure seal bonnet improves as internal pressure increases.
• Pressure Seal Gate Valves: Gate valves are multi-turn linear motion valves with a rising stem, meaning multiple handwheel rotations are required for full opening or closing of the valve. Gate valves are designed to operate only in fully open or fully closed positions. If used in a partially open condition, the gate may vibrate or chatter, and erosion (wire drawing) may occur at the seating surfaces. Therefore, gate valves should not be used for flow regulation. Gate valves close by rotating the handwheel clockwise and open by rotating it counterclockwise. For handwheel-operated valves, the position of the stem above the handwheel indicates whether the valve is open or closed. In gear-operated valves, where the stem top may not be visible, a position indicator is provided to show valve status. The valve closes by driving the disc downward into the seat ring area. The disc and seat rings are precisely machined and lapped to ensure tight sealing. When the valve is fully open, the stem back-seats in the bonnet to provide additional sealing protection.
• Types of Pressure Seal Gate Valves: Based on disc design, pressure seal gate valves are classified into two types: Pressure Seal Flexible Wedge Gate Valve; Pressure Seal Parallel Slide Gate Valve.

» Separated rings are designed to absorb the thrust along the stem generated by internal pressure.

» Sealing rings are used to withstand system pressure and prevent deformation of the gaskets.

» Stainless steel inlays are provided to ensure integrity and corrosion resistance in the critical body sealing zone for carbon steel and alloy steel valves.

» A mild steel gasket seal provides a large contact area to achieve reliable and effective sealing performance.

» The blowout-proof stem design features a tapered sealing surface that contacts the bonnet backseat when the valve is fully open, enhancing safety and sealing reliability.

» The flexible wedge design can compensate for seat face distortion and body deformation caused by pipeline stress.

» Seat rings with Stellite 6 hardfacing overlay are provided as standard and are installed using a seal-welded construction.