Working Principle and Advantages of Knife Gate Valves

Release time:

2022-07-07

Working Principle and Advantages of Knife Gate Valves A knife gate valve is a relatively common type of gate valve and can also be considered a very typical on-off valve. Its shape resembles that of some ancient guillotines, so people commonly refer to this type of on-off valve as a knife gate valve; many also simply call it a “knife gate valve.”

The knife gate valve is a relatively common type of gate valve and can also be considered a very familiar on-off switch. Its shape resembles that of some ancient guillotines, so people commonly refer to this type of switch valve as a knife gate valve; many others also call it... “Knife Gate Valve.” This vividly describes the shape of a knife gate valve. Today, knife gate valves are not only used in electrical circuits but are increasingly prevalent in most industrial pipeline applications as well. Unlike the simple knife-gate circuits of the past, today’s knife gate valves feature more complex structures and a wider range of functions. Below is an explanation of how a knife gate valve works.

Working principle

It consists of three main components: the handwheel for controlling the knife gate valve, the outer wall of the valve body, and the internal control mechanism. We primarily operate the knife gate valve by turning the easily accessible handwheel located above the valve, which sets in motion a series of physical actions within the valve body via the control mechanism, thereby opening or closing the valve and ensuring its proper functioning and effective control of the pipeline.

The internal structure is highly complex. By manually turning the handwheel of the knife gate valve, we set it in motion, which in turn drives the levers and gears inside the valve. Through a coordinated series of movements, the blocking mechanism within the valve rapidly changes its position, enabling the knife gate valve to open and close depending on the direction of rotation. Moreover, this operation can be completed in a very short time, effectively saving time and boosting work efficiency.

The working principle is to turn the handwheel by hand, causing the valve stem to rise or fall, which in turn moves the gate up or down, thereby opening or closing the valve. Turning the handwheel clockwise lowers the gate and closes the valve. Turning the handwheel counterclockwise raises the gate and opens the valve.

Compared to traditional gate valves, knife gate valves have a simpler structure, smaller length and dimensions, and are easier to install, disassemble, and maintain. Knife gate valves are suitable for pipelines carrying media with high viscosity and containing solid particles. The blade-like gate disc delivers a superior crushing and breaking effect, effectively breaking down various impurities contained in the medium flowing through the pipeline. This addresses the leakage issues commonly encountered with traditional gate valves after they have been used to handle media containing particulate impurities.

The structure has a short length and occupies minimal space. The full-bore knife gate valve design enables the valve to operate even in media containing impurities, while the replaceable seat and disc make valve maintenance significantly easier.

Although knife gate valves outperform traditional gate valves in terms of performance, their higher price compared to traditional gate valves means that knife gate valves cannot completely replace traditional gate valves.

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?