Slide valves ? opens and closes the flow in demanding applications
Slide valves regulate flow with the help of a plate or flap that is raised or lowered over an opening in the pipe. Vimab works primarily with wedge gate valves, a type of gate valve with a wedge at the bottom that makes the flap close to the seat. This type of valve is suitable for shutting off the flow with high pressure and high temperature.
In a slide valve, the flow is regulated by a plate or flap that slides into place, up and down, over an opening. It is activated by a wedge or slide at the bottom of the flap resting against its seat. The valve type is used for shut-off. The advantage is that it has a straight flow and therefore allows maximum flow when it is fully open. It is manoeuvred by means of a knob or a manoeuvring lever.
A slide valve should only be used when it is fully closed or fully open. If it is left partially open during operation, the valve may be damaged.
The most common types of gate valves are wedge gate valves and gate valves. In a wedge gate valve, the plate is wedge-shaped at the bottom, which means that it is pressed tightly against the sealing element and prevents leakage. In a gate valve, the sealing is missing with a wedge, which means that it does not seal as well. Gate valves are therefore used in low-pressure applications, such as water and sewage.
The wedge gate valve, on the other hand, can handle high pressures and high temperatures. A flow with a temperature of just over 500 degrees and a pressure of 100 bar, for example, is not an unusual application for a wedge gate valve. The valve is tight in both directions. It is often used for different types of applications in the power industry.
Another type is the parallel slide valve. Instead of a wedge, this type has a round seal that t�ts against a seat in the inflow and one in the outflow to the valve. The advantage of this type is that it opens and closes very quickly and takes a lot of water. It is often used in the oil and gas industry.
H�igh pressure
If a wedge gate valve is operating under very high pressure, you may need to reduce the pressure in order to open it. Otherwise the flap will be too close to the valve body. To reduce the pressure, there is often a bypass valve, a small pipe with a valve that directs part of the flow past the wedge and thus reduces the pressure.
In terms of size, wedge gate valves start at 25 mm and can be virtually any size.
Wedge gate valves should not be used in applications with particles in the media, as the particles can get trapped under the wedge and cause leakage.
It is important that the flap slides smoothly against the valve body. To minimise friction, there are many different materials to choose from for both the clapper and the valve body, such as stainless steel, cast iron or ductile iron. Since the different materials have different properties at different pressures, temperatures and in different media, material selection can be a delicate task. Here you have to consult the manufacturer to get a combination of properties that works.
Regular maintenance
The wedge gate valve needs to be exercised occasionally so that the wedge does not get stuck. In addition, the threaded spindle needs to be lubricated and you should also make sure that no debris is stuck in the spindle.
If the valve is leaking, you need to grind the wedge and seat surface. Valves with flanged mounting can be disassembled and transported to Vimab for refurbishment. In the case of welded assembly, the valve is refurbished on site with portable equipment. There are a large number of makes of wedge gate valves. For the most demanding applications, Vimab recommends valves from KSB, Persta and Sempell.
Click here to see which wedge gate valves are currently in stock. http://ventillager.vimab.se/