Gate valves are widely used for all types of applications and are suitable for both above-ground and underground installation. It is paramount to choose the right type of valve to avoid high replacement costs.
Gate valves are designed for fully open or fully closed service. They are installed in pipelines as isolating valves, and should not be used as control or regulating valves. Operation of a gate valve can be provided with a clockwise to close (CTC) or clockwise to open (CTO) rotating motion of the stem. When operating the valve stem, the gate (or wedge) moves up- or downwards on the threaded part of the stem.
Gate valves are often used when minimum pressure loss and a full, free bore flow path is required. When fully open, a typical gate valve has no obstruction resulting in a very low pressure loss, and this design makes it possible to use a pipe-cleaning pig.
A gate valve is a multi-turn valve meaning that the operation of the valve is done by means of a threaded stem. As the valve has to turn multiple times to travel from the open to closed position, the slow operation also prevents water hammer effects.
Figure 1 - resilient seated gate valve (smooth base on valve bore)
Figure 2 – metal seated gate valve (sump at base of valve bore)
Brief history and current status of metal vs resilient seated gate valves.
Before the resilient seated gate valve was introduced to the market (circa 1980’s), gate valves with a metal seated design were most commonly used for all sizes. Since then, resilient seated gate valves have become, by far, the most common choice for water and wastewater applications for sizes up to and including pipework diameters of 600mm. Metal seated gate valves are still more commonly used for valve sizes of DN700 and above.
However, with advances and improvements in manufacturing processes and equipment, resilient seated gate valves are readily available from AVK in sizes up to and including DN1000, and this will be increased further to DN1200 in the near future.
As you would expect from AVK, these larger resilient seated gate valves are designed, tested and manufactured in full accordance with the relevant standards (BS EN1074-1 & 2, BS EN558, BS EN1092-2 & BS EN12266-1) and are suitable for drinking water applications being manufactured from WRAS approved materials.
Download this report.
This downloadable report (click on the link - no login required) describes the various advantages of using resilient seated gate valves compared to the metal seated equivalent and shows that the following important benefits can be achieved:
• Leakage reduction
• Increase system efficiency
• Reduced operating torque and input effort
• Reduced costs for gearboxes and electrical actuators
• Reduces power consumption for valve operation
• Increased flexibility for valve installation
There is a legacy of using metal seated gate valves for water and wastewater applications on sizes above DN600. However, resilient seated gate valves are now readily available from AVK in sizes up to and including DN1000 (see Figure 5) and this size range will increase even further in the near future.
AVK offer a full range of resilient seated gate valves from DN50 to DN1000 and also offer metal seated gate valves from DN50 to DN1800. A wide range of options are also available.
We would welcome the opportunity to discuss your gate valve requirements, please contact AVK UK directly on the link above and we will connect you with the technical specialist best suited to your project or installation.
Note: This paper was authored by Greg Morris, AVK UK Technical Manager, our specialist in valves for Dams, Reservoirs and Hydropower.
