Learn about the development history of knife gate valves.

Release time:

2022-05-31

Gate valves entered China in the 1980s, and within less than two decades, their application scope has expanded from conventional areas to a wide range of industries. They are now used not only in coal preparation, gangue removal, and slag discharge at mines and power plants, but also in urban wastewater treatment. Moreover, their use has extended from general industrial pipelines to specialized pipeline systems in sectors such as food, sanitation, and pharmaceuticals.

　　Gate valves entered China in the 1980s, and within less than two decades, their application scope has expanded from conventional areas to a wide range of industries. They are now used not only in coal preparation, gangue removal, and slag discharge at mines and power plants, but also in urban sewage treatment. Moreover, their application has extended from general industrial pipelines to specialized pipeline systems in sectors such as food, sanitation, and pharmaceuticals.

　　A knife gate valve, also known as a knife-type sluice valve or a blade-type slurry valve, features a gate as its closing member. The gate’s motion direction is perpendicular to the flow direction of the fluid. The gate, equipped with blade-like edges capable of cutting fibrous materials, serves to shut off the medium. The gate has two sealing surfaces; in commonly used wedge-shaped gate valves, these two sealing surfaces form a wedge shape, with the wedge angle varying depending on the valve’s specifications—typically around 50 degrees. In wedge-type knife gate valves, the gate can be constructed as a single piece, referred to as a rigid gate.

　　It is also possible to fabricate gate valves with a slight degree of deformation capability, which improves their manufacturability and compensates for deviations in the sealing surface angles that may occur during machining. Such gates are referred to as flexible gates. In fact, the valve body does not have any internal chamber; instead, the gate moves up and down within guide slots on the side and is tightly pressed against the valve seat by lugs at the bottom. If higher media sealing performance is required, an O-ring sealed valve seat can be used to achieve bidirectional sealing. Knife gate valves feature a compact installation footprint, low operating pressure, resistance to debris accumulation, and a relatively low cost.

　　When a knife gate valve is closed, the sealing surfaces rely solely on the pressure of the medium to achieve sealing—specifically, the medium pressure forces the sealing surface of the gate against the valve seat on the opposite side, thereby ensuring a tight seal. This is known as self-sealing. Most knife gate valves, however, employ forced sealing: when the valve is closed, an external force is required to press the gate firmly against the valve seat, thus guaranteeing the sealing performance of the sealing surfaces. In piping systems, valves of this type should generally be installed horizontally.

The vast majority of stainless steel knife gate valves employ forced sealing: that is, when the valve is closed, an external force is applied to forcibly press the gate against the high-pressure valve seat, thereby ensuring a tight seal on the sealing surfaces. Some gates can also be designed to undergo slight deformation, which helps improve their manufacturability and compensate for any misalignment in the sealing surface angles that may occur during the manufacturing process. Such gates are referred to as flexible gates. The majority of knife gate valves rely on forced sealing—meaning that when the valve is closed, an external force is used to press the gate firmly against the high-pressure valve seat, thus guaranteeing a secure seal on the sealing surfaces. Valves of this type are generally installed horizontally in pipelines.

2023-05-11

Next, let’s talk about several operating procedures for knife gate valves.

When a gate valve is closed, the sealing surfaces rely solely on the pressure of the medium to achieve a seal—specifically, the sealing surface of the gate is pressed against the valve seat on the opposite side by the medium’s pressure, thereby ensuring a tight seal. This type of sealing is known as self-sealing. In contrast, most gate valves employ forced sealing: when the valve is closed, an external force must be applied to press the gate against the valve seat in order to guarantee the sealing performance of the sealing surfaces. Such valves should be installed vertically in the pipeline.

2023-05-11

Next, let’s talk about whether knife gate valves have fire-resistant and anti-static requirements.

When an electrostatic knife gate valve is opened or closed, the sphere and the valve seat experience mutual friction. The static electricity generated by this friction tends to accumulate on the sphere—something that is unacceptable for ball valves used in gas, fuel, and chemical pipelines, as it could potentially lead to pipeline explosions. Ball valves with antistatic designs are equipped with static discharge devices.

2023-05-11

Next, let’s talk about some important considerations for the installation, operation, and maintenance of pneumatic knife gate valves.

Pneumatic knife gate valves have a wide range of applications, spanning from ordinary fields to more diverse industries—from coal preparation, gangue removal, and slag discharge in coal-fired power plants to urban wastewater treatment; from general industrial pipelines to pipeline systems used in food, sanitation, and pharmaceutical industries. So, what are the key considerations when installing, using, and maintaining pneumatic knife gate valves?

2023-05-11

Slurry Valve Manufacturer: How are stainless steel knife gate valves good?