Why Gate Valves are Equipped with Back Seat

Back seat refers to a sealing design feature that prevents medium leakage to stuffing box in certain types of valves, such as globe valves and gate valves.

Take gate valves for example, they are equipped with a back seat mainly for the following important reasons:

Secondary Seal: The primary function of the back seat is to provide a secondary metal-to-metal seal that prevents leakage when the valve is fully open. When the gate valve is in the fully open position, the stem is extended outwards and pressed against the back seat, creating a reliable metal-to-metal seal. This secondary seal ensures that there is no fluid leakage through the stem packing when the valve is fully open, even if the primary stem packing is damaged or worn.

Maintenance and Repairs: The back seat design simplifies maintenance and repairs of gate valves. When the valve is fully open, maintenance personnel can safely work on the stem packing or other components without shutting down the entire system. This is particularly important in industrial settings where minimizing downtime is critical.

Durability: The metal-to-metal seal between the stem and the back seat enhances the overall durability and longevity of the gate valve. It helps protect the stem and the stem packing from corrosion and wear, extending the valve's service life.

Safety: Gate valves are commonly used in critical applications where safety is paramount. The back seat feature adds an extra layer of safety by preventing any unintentional or unexpected fluid leakage through the stem when the valve is fully open.

Compliance: In certain industries and applications, gate valves with back seat features may be required to meet specific industry standards, regulations, or safety guidelines. The back seat feature ensures compliance with such requirements.

These benefits make gate valves with back seats a suitable choice for various industrial and commercial applications, especially those where leakage prevention and minimal downtime are essential.