Types of Gate valves

Gate valves are classified based on the type of disc, body-bonnet joint, and stem movement . Here’s a breakdown:

I. Based on Disc Type:

Solid Wedge Gate Valve: This is the most common and basic type, known for its simplicity and strength . It’s a single, solid piece and suitable for most fluids and turbulent flow .
Flexible Wedge Gate Valve: This has a one-piece disc with a cut around the perimeter to provide flexibility . This design is better for thermal expansion and prevents thermal binding, often used in steam systems .
Split Wedge (Parallel Disc) Gate Valve: It has two solid pieces held together by a mechanism . This allows each disc to adjust to the seating surface and is suitable for noncondensing gasses and liquids .

II. Based on Body-Bonnet Joint:

Screwed Bonnet: This is a simple, inexpensive design .
Bolted Bonnet: This is the most common type, using a gasket to seal the joint .
Welded Bonnet: It’s a design where disassembly is not required, and it’s lighter than bolted bonnets .
Pressure-Seal Bonnet: Used for high-pressure and high-temperature applications, where increased pressure improves the seal .

III. Based on Stem Movement:

Rising Stem (Outside Screw and Yoke – OS&Y): The stem rises when the valve is opened, giving a visual indication of the valve position . The stem threads are outside the valve, protecting them from the fluid .
Non-Rising Stem (Inside Screw): The stem does not rise or lower; instead, it rotates, making it suitable for tight spaces . The stem threads are exposed to the fluid .

Additional Types:

Knife Gate Valve: This is designed with a sharp edge to cut through thick fluids and slurries, often used in industries like mining and paper .
Through-Conduit Gate Valve: This type has a gate that’s fully enclosed when open, which is designed to maintain a smooth, uninterrupted flow path. It’s commonly used in pipelines where pigging is required .