Let’s talk about the performance characteristics of knife gate valves.

Release time:

2022-01-05

The knife gate valve, also known as the knife-type gate valve, knife-gate valve, slurry valve, or mud valve, features a gate plate as its closing member. The motion direction of the gate plate is perpendicular to the flow direction of the fluid. The medium is cut off by a blade-shaped gate plate that can shear fibrous materials. The gate plate has two sealing surfaces; in commonly used designs, these two sealing surfaces form a wedge shape, with the wedge angle varying depending on the valve’s specifications—typically around 5°. In wedge-type knife gate valves, the gate plate can be made as a single piece, referred to as a rigid gate plate.

　　The knife gate valve, also known as the knife-type gate valve, blade gate valve, slurry valve, or mud valve, features a gate plate as its closing member. The motion direction of the gate plate is perpendicular to the flow direction of the fluid. The medium is cut off by the blade-like edge of the gate plate, which is capable of shearing fibrous materials. The gate plate has two sealing surfaces; in commonly used designs, these two sealing surfaces form a wedge shape, with the wedge angle varying depending on the valve parameters—typically around 5°. In wedge-type knife gate valves, the gate plate can be made as a single piece, referred to as a rigid gate plate.

　　It is also possible to fabricate gate valves with micro-deformation capabilities, which can improve their manufacturability and compensate for any angular deviations that may occur on the sealing surfaces during machining. Such gates are referred to as elastic gates. In knife gate valves, the valve body essentially has no cavity; instead, the gate rises and falls within lateral guide slots and is tightly pressed against the valve seat by protrusions 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, operate at low working pressures, are resistant to the accumulation of debris, and are relatively inexpensive. Before installing a stainless steel knife gate valve, the manufacturer recommends thoroughly inspecting the valve cavity and sealing surfaces to ensure that no contaminants or sand particles remain. All bolts at connection points must be tightened evenly. The packing area should be checked to ensure it is properly compressed—this guarantees both the sealing performance of the packing and the smooth operation of the gate plate.

　　Before installing the valve, users must verify that the valve model and connection dimensions are correct and pay attention to the flow direction of the medium to ensure compliance with the valve’s specifications. When installing the valve, users must leave sufficient space for the valve actuator. Wiring connections for the actuator must be made according to the wiring diagram. Knife gate valves must undergo regular maintenance and should not be subjected to random impacts or compressions, as this could compromise their sealing performance.

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?