Differences between knife type gate valve and ordinary gate valve

Gate valve,also called sluice gate valve, sluice valve,is one widely used industrial valve. The movement direction of the valve plate of the gate valve is perpendicular to the direction of the medium fluid. The gate valve can only be fully opened and fully closed, and cannot be used for adjusting or throttling. The gate valve is sealing by the contact between the valve seat and the valve plate. For different sealing structure, there are resilient seated soft sealing gate valve, and metal to metal seated hard sealing gate valve. For soft sealing gate valve, its valve seat material is usually EPDM or PTFE. For metal seated hard sealing gate valve, its sealing surface is usually welded with metal material to increase its wear resistance, such as 1Cr13, STL6, stainless steel,etc. 

Knife type gate valve is actually one kind of gate valve, whose valve plate moves up and down perpendicular to the direction of the medium flow to achieve the opening and closing of the knife type gate valve. So the working principle of knife type gate valve is same as that of the gate valve, so we can say that knife type gate valve is one special kind of gate valve. Even that there are still some differences between knife gate valve and gate valve.

today we are going to introduce you the differences between knife type gate valve and ordinary gate valve: 

1. The knife type gate valve and ordinary gate valve have different function: 

The function of the knife type gate valve is to cut off and not to throttle, while the ordinary gate valve can be used as a throttle or a switch device. Compared with ordinary gate valve, knife type gate valve is simple in structure, small in size, flexible in operation, easy to install and suitable for media with high consistency and solid particles. The full bore knife gate valve allows the knife type gate valve to be used for dirty media, and the replaceable valve seat and packing make the knife type gate valve to be easy and convenient to maintain. Even though the performance of knife type gate valve is generally better than that of the ordinary gate valve, while the price of knife type gate valve is generally higher than that of the ordinary gate valve. 

2. The knife type gate valve and ordinary gate valve have different applications: 

Knife type gate valves are suitable for viscous particles and are often used in beverage, paper, pulp industry, industry sewage, urban sewage treatment, chemical plants, bulk material transportation, and flying ash treatment industry. 

Gate valve are generally used in chemical industry, metallurgy, power station, mining, pharmaceutical, boiler, tobacco, hotel, construction, textile and other industries. 

Knife type gate valve is also called knife gate valve, knife edge gate valve, knife blade gate valve, slide gate valve, slurry knife gate valve, slurry gate valve, mud gate valve, mud knife gate valve. The opening and closing part of the knife gate valve is one sharp disc, the movement direction of the valve disc of the knife type gate valve is perpendicular to the flow direction of the fluid. The knife type gate valve can cut off the medium by the blade-shaped valve plate which can cut the fiber materials. The valve plate of the knife type gate valve has two sealing surfaces, that two sealing surface form a wedge shape. The wedge angle varies with the parameters of the knife type gate valve, usually that wedge angle is 5°. 

The valve plate of the knife type gate valve can be made into a whole, which is called a rigid valve plate; that valve plate can also be made into a gate what can produce a small amount of deformation, to improve its manufacturability and compensate for the deviation of the sealing surface angle during processing. This kind of valve gate is called elastic valve plate; 

There is actually no chamber in the valve body of the knife type gate valve, the valve plate moves up and down in the side guide groove, and is pressed tightly on the valve seat by the lug structure at the bottom of the valve body of the knife type gate valve. If a higher medium sealing performance is required, an O-shaped sealing seat can be used to achieve the bidirectional sealing effect. 

3. The knife type gate valve and ordinary gate valve have different sealing structure: 

The knife type gate valve has small installation space, low working pressure, is not easy to accumulate sundries and for some types of knife type gate valve, their price is low. 

When the knife type gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, relying on the medium pressure to press the sealing surface of the valve plate to the valve seat on the other side to ensure the sealing effect of the sealing surface, which is called self-sealing. 

While most of the ordinary gate valve adopt forced sealing, that is to say, when the gate valve is closed, the valve plate should be pressed to the valve seat by the external force, so as to ensure the sealing effect of the sealing surface. 

The knife type gate valve is suitable for use in mud and fiber-containing medium pipelines, and its knife-shaped gate can cut off the fiber materials in the medium; knife type gate valve is often used in the pipelines for conveying coal slurry, ore slurry, and paper making slurry. 

The knife type gate valve is a derivative of the ordinary gate valve, which has its unique advantages and disadvantages. 

Advantages of knife type gate valve: 

1. Metal to metal hard sealing knife type gate valve is the preferred valve product for slurry, mud, and pulp pipelines; 
2. Knife type gate valve has simple structure, small size, light weight, and is easy to install. 

Disadvantages of knife type gate valve: 

1. Knife type gate valve can only be used in low pressure pipelines. 

Gate valve is a large category, there are various different types of gate valves, various types gate valves are suitable for many working conditions; 

While knife type gate valves are mainly used in slurry pipelines, and can also be said that: knife type gate valve is the special valve for slurry pipeline, that is why knife type gate valve is also called slurry gate valve or mud gate valve;