A double-disc gate valve is also known as a parallel double-disc gate valve. A double-disc gate valve is a type of gate valve that has two discs and two seats. The disc in a double-disc gate valve is used to open or close fluid flow. The two-disc expand from each other when the valve is working. Double disc gate valve manufacturers design these valves in on and off-fluid flow applications. These valves are not meant for use in throttling applications.
Double disc gate valves have tight seals, which ensure zero fluid leakage unless there is mechanical damage to parts of the valve.
The basic principle of double disc gate valve (stretch type, upper top wedge):
When the gate valve is closed after the gate plate is lowered to the bottom, the valve stem continues to push the top wedge down so that the two gate plates are stretched open and tightly pressed on the sealing surface of the valve seats on both sides to achieve forced sealing.
Double disc gate valves are operated manually using the valve handwheel or through pneumatic, electric, and hydraulic actuators. Double disc gate valves have two disc seals. The sealing is enhanced by combining internal fluid pressure and spring force. A floating seat is used to relieve pressure automatically when the middle section of the valve is under pressure.
The double disc gate valve has the following structural characteristics:
1. The valve adopts a sealing structure composed of two parallel gate plates and their wedge-tightening devices to replace the traditional wedge gate valve structure.
2. The parts of the valve sealing mechanism are separated from each other; even if the temperature changes are caused by deformation, it can still ensure the sealing and will not make the gate plate squeeze and open due to high-temperature expansion.
3. The valve seal is made of wear-resistant and corrosion-resistant materials, which prolongs the valve’s service life.
Double gate plate gate valve has many advantages, such as good sealing, safety, and long life. Its level of development has also reached a certain height. Currently, there are various types of double gate plate gate valves on the market, which are used in different fields and have different structural characteristics.
The most traditional structural forms of double gate plate valves are self-sealing type (unsuitable for the high-pressure environment, gradually replaced) and stretch type. The stretch type is divided into upper top wedge type and lower full wedge type.
The double-gate gate valves of these structures have their characteristics and have their advantages and disadvantages. The design of gate valves also tends to be diversified, but there are also rules to follow, and the double gate plate gate valves on the market can be roughly divided into two categories.
The first type is composed of two gate plates and wedge structures, which are relatively independent and work together to complete the sealing effect. The other type is the combination of wedge and gate plate as a whole, and the gate plate itself is used as a wedge structure, extruded to form a self-seal.
In contrast, the second type of structure has better stability because such a structure has much fewer parts under the same function. This significantly improves stability.
The design should also consider the situations that may be encountered in the application process, and design the appropriate structure according to different situations.
Working conditions for double disc gate valve:
Parallel double gate valve is suitable for use as closed circuit equipment on pipelines where the medium is water and sewage, and is allowed to be used for regulating flow and emptying. Frequently used in petroleum, chemical, pharmaceutical, power, and other industries. It is used for opening and closing the pipeline of steam, water, oil, and other media with nominal pressure ≤ l.0MPa. There are parallel double gate valves, parallel single gate valves, open rod parallel double gate valves, and open rod parallel single gate valves.
Features of double disc gate valve:
1.When the system works normally, the gate plate opens and closes at a constant speed of 1.0m/min; The shutdown in an accident state such as a system power failure is divided into two stages: fast and slow shutdown.
2.It is used in the outlet of the water pump as a shut-off and check valve, and the valve also has a stem-locking device. Ensure safe operation.
3.Z943T gate valve adopts a new electric device, which can be operated locally or remotely controlled, and can meet the requirements of computer program control. Accurate, safe, and reliable control.
Working principle of double disc gate valve:
Parallel double gate valve is a kind of ceramic gate valve. Therefore, its structure and working principle are consistent with the gate valve, and its opening and closing body (valve plate) is driven by the valve stem to lift the sealing surface of the valve seat, which can connect or cut off the channel of the fluid.
With the help of the external power provided by the cylinder or handwheel, the valve stem drives the valve plate to move up and down to realize the opening and closing of the valve, and the preload of the spring set between the double gate plate is closely in contact with the valve plate and the valve seat during the valve opening and closing process to achieve sealing.