Introduction to the Application of Knife Gate Valves

Release time:

2022-04-20

The method of selecting materials for knife gate valves—choosing valve materials based on different circulating media and varying service environments—has become a consensus among many valve manufacturers. However, there are certain differences in material selection for knife gate valves. Due to their inherent properties and performance characteristics, carbon steel and stainless steel are typically used as the primary materials in most cases.

　　Rather than alloy materials or even engineering plastics used in other types of valves, the valve body itself requires both strength and hardness; therefore, carbon steel is primarily used for the valve body. The advantage of carbon steel is obvious: its high carbon content provides exceptional hardness and strength. Since gate valves frequently come into contact with liquid media, the materials used to manufacture knife gate valves should be corrosion-resistant stainless steel.

　　To ensure the service life of knife gate valves, the materials used in these valves actually need to be selected based on the specific operating conditions—meaning they can be custom-made according to requirements. During operation, the valve should be cleaned regularly and lubrication measures should be performed at scheduled intervals. Due to the unique characteristics of its gate, the stress levels are relatively high; therefore, special attention should be paid to the selection of materials for the sealing surfaces and the valve stem. The strength and load-bearing capacity of these two components directly affect the overall performance of the valve.

　　When installing outdoors, pay attention to waterproofing measures to prevent rainwater from causing external corrosion. Valves should also be provided with appropriate protective measures, as external dust and solid impurities will inevitably scratch and damage them. If the installation location is near the sea, consider the corrosive effects of seawater and sea breeze on the valve body. In this regard, it is recommended to use enhanced metal or ceramic materials that are resistant to acid, alkali, and salt corrosion as the primary material for the valve body.

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?