All You Need to Know About Gate Valves 

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Gate Valve is designed to be fully open or fully closed. It is unable to control flowrate of liquids. It has 2 ports for inlet and outlet. It commonly has a built-in wheel for manual opening/closing which can be done by multiple 360 degrees turns. It has slow opening and closing speed which prevents water hammer effect. Water hammer effect is a phenomenon that occurs when the valve close quickly and the flowing water inside the pipe hits the closed valve abruptly. This results in extremely high pressures in pipes and causes the water to flow backwards. Pipes may burst and joint leaks can happen when the pressures in the pipe are too high. 

Gate Valve is designed to be fully open or fully closed. It is unable to control flowrate of liquids. It has 2 ports for inlet and outlet. It commonly has a built-in wheel for manual opening/closing which can be done by multiple 360 degrees turns. It has slow opening and closing speed which prevents water hammer effect. Water hammer effect is a phenomenon that occurs when the valve close quickly and the flowing water inside the pipe hits the closed valve abruptly. This results in extremely high pressures in pipes and causes the water to flow backwards. Pipes may burst and joint leaks can happen when the pressures in the pipe are too high. 


DT

1. Disc Type 

Solid Wedge – commonly used in applications with a moderate to low pressure-temperature range. 
Split Wedge – generally used in corrosive liquids at normal temperatures.
• Flexible Wedge – commonly used in high temperature steam systems.

2. Stem Type

RSGT

Rising Stem Gate Valve

Image Credit: Whatispiping.com

When the valve is open, the stem of the valve will rise over the handwheel. 

• Suitable for only above-ground installation.

NRSGT

Non-rising Stem Gate Valve

Image Credit: Whatispiping.com

• When the valve is open, the disc in the valve moves up while the stem remains at original position without moving. This is because the disc is threaded with the stem.

• Suitable for underground or limited space condition installation.

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Fully Open and Closed for Rising Stem Gate Valve

Image Credit: Assuredautomation.com 

When the built-in wheel on top of gate valve is rotated, the disc of the valve is raised from the flow channel. To close the gate valve, the wheel must be rotated in another direction, which slowly brings the disc down and blocks the flow of liquids. The main component which raises or brings down the disc of the valve is the rising stem that is attached with the wheel.

Applications

Based on different designs of the gate valve, gate valves are utilised in many industries such as pharmaceuticals, automotive, manufacturing, water and the oil and gas industries. These are some of the common applications:

● Older plumbing systems where on/off is not frequent 
● Water treatment plants 
● Clean water supply and building services  

Advantages

- Gate valves can be used in both directions
- Minimum pressure loss when gate valve is fully open.
- They perform tight sealing when fully closed.
- They help to prevent water hammer effect.

Disadvantages 

- Gate valves cannot deal with slurries/ viscous fluids.
-They cannot operate quickly.
- Gate Valves require large space for installation and maintenance.
- The seat and disc for gate valves tend to wear out.