A brief introduction to the functions of a hydraulically actuated knife gate valve.

Release time:

2021-12-28

The hydraulic knife gate valve, also known as the hydraulic knife-type gate valve or hydraulic blade gate valve, connects the piston rod of a hydraulic cylinder to the valve gate. Its operating principle is as follows: By manually actuating the handle of the hydraulic pump, hydraulic oil is directed through a manual directional control valve into the upper and lower chambers of the hydraulic cylinder. The piston rod then moves up and down, driving the opening and closing of the gate and thus completing the valve’s on/off function.

　　The functions and applications of the hydraulic knife gate valve are as follows: compact structure, rational design, excellent valve rigidity, smooth flow passage, and a low resistance coefficient. The seals are made of stainless steel and hard alloy, ensuring a long service life. The knife gate valve employs flexible graphite packing rings to achieve reliable sealing, along with robust yet sensitive operation.

　　The operating modes include manual, electric, pneumatic, gear-driven, and structural types—specifically, the elastic wedge type. The main technical parameters and performance characteristics of the hydraulically actuated knife gate valve are as follows: Nominal pressure: 0.6 MPa, 1.0 MPa, 1.6 MPa, 2.5 MPa, 150 Lb; Nominal diameter: DN50 to 500 mm, NPS 2" to 20".

　　Applicable temperature: -38~+200℃ (the specific temperature range depends on the materials of the sealing elements and the properties of the medium). Flange connections: ANSI B16.5, GB/T9113, JB/T79, HG, SH, JIS, DIN, NF, BS. Body materials: WCB, ZG1Cr18Ni9Ti, ZG1Cr18Ni12Mo2Ti, CF8, CF8M, CF3, CF3M. Sealing types: hard seal, soft seal.

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?