Ultra Control Valves was among the exhibitors at the recent IMESA Conference held 29 to 31 October at the East London International Convention Centre. Peter Telle of Ultra Control Valves here explains the difference between wedge gate valves and RSV gate valves, highlighting the benefits gained through product developments.
The traditional wedge gate valve (left) and the RSV gate valve (right), preferred today for most water and wastewater applications.
Gate valves are widely used in water and wastewater systems, but not all gate valves are the same. Understanding the differences between wedge and resilient seated (RSV) gate valves helps users choose the right option for reliability, cost, and long-term performance.
Wedge gate valves
Traditionally, the term ‘gate valve’ referred to wedge gate valves, which have a metal-to-metal seating. The gate is shaped like a wedge so that it can be forced tightly onto the body seats.
The valves are designed to be strong and long-lasting, but they do have some drawbacks.
- They are often over-tightened to achieve a tight seal, and this can make them hard to open again. Forcing them with leverage poles can cause damage.
- The groove at the bottom of the valve traps dirt, which prevents the valve closing properly.
- Corrosion protection is difficult because the coating is easily damaged in areas next to the seating surfaces.
Resilient seated gate valves
To overcome these problems, resilient seated gate valves were developed. They use a rubber-coated gate that seals directly against the valve body. With this design, no separate body seat is needed. A fusion bonded epoxy (FBE) coating on the body and bonnet saw this type of valve quickly become popular.
Product improvements
In early RSV gate valves, there were problems with poor manufacturing quality and the rubber lining coming loose. Many users switched back to wedge gate valves at that time. However, subsequent improvements fixed the problems. The rubber is now moulded to the gate under high temperature and pressure, creating a strong bond that covers both the inside and outside surfaces, including the area where the spindle moves. Most manufacturers follow this process today, and some offer up to 20-year replacement guarantees.
RSV gate valves are now widely used for scour applications, where high water speeds once tore the rubber from the valve. The only caution in scour use is that rats might chew the rubber to reach water, but this can be prevented by installing a guard mesh over the outlet.
RSV gate valves deliver several benefits.
- Current designs provide better sealing performance.
- The valves require lower operating torque because friction is reduced between the gate and valve body.
- Particles are easily flushed out because there is no groove at the bottom of the valve.
- RSV gate valves reduce water hammer as the rubber absorbs pressure spikes.
- Because they need less machining and are produced in high volumes, RSV gate valves are usually less expensive and more readily available than wedge gate valves.
Resilient seated gate valves offer a more modern, corrosion-resistant and low-maintenance alternative to traditional wedge gate valves. For most water and wastewater applications, they provide dependable operation and good long-term value.
For more information visit: www.ultravalves.co.za
