The pressure structure selection of electric gate valve?

Definition of valves

Valve is the control device of fluid pipeline. Its basic function is to connect or cut off the flow of pipeline medium, change the flow direction of medium, regulate the pressure and flow of medium, and protect the normal operation of pipeline and equipment. This paper focuses on the selection of common valves for water supply pipelines and matters needing attention.

For water supply pipelines, valves are often used, such as gate valves, globe valves, ball valves, cock valves, butterfly valves, and each valve can be divided into more categories according to its structure.

For many kinds of valves, in order to select the most suitable valve products for installation in pipeline system, first of all, we should know the characteristics of the valve, the position used and the medium of circulation; secondly, we should select valves with reasonable price and reliable quality according to the working environment; finally, we should pay attention to the matters of selecting valves.

II. Characteristics of Valves

Valve characteristics can be divided into two types: service characteristics and structural characteristics.

The service characteristics of the valves determine the main performance and scope of use of the valves. Valve usage characteristics include: valve selection, valve selection summary

Product types: gate valves, globe valves, butterfly valves, ball valves, etc.

The main parts of the valve: body, bonnet, stem, disc, sealing surface material, etc.

(3) Valve transmission mode.

III. Structural Characteristics of Valves

The structural characteristics of the valve determine the characteristics of the installation, maintenance and other methods of the valve. Among the structural characteristics are:

The structural length and overall height of the valve;

(2) Connection form with pipeline: flange connection, welding connection, internal thread connection, external thread connection, etc.

(3) The form of sealing surface: Insert ring, threaded ring, surfacing, spray welding, etc.

(4) Stem structure: rotating rod, lifting rod, etc.

IV. Selection of Valves

Valve is a kind of control device for "keeping soldiers for thousands of days, for a short time". Normally, the valve should be opened in place to reduce the water loss in the pipe section; once necessary, the valve should be able to quickly close and reliably cut off the flow.

The principle of valve selection in water supply system is to select high-quality, reliable and applicable valves, and to use new and more advanced valves for those types that can not meet the requirements for a long time.

Next, the application of several commonly used valves in water supply system is illustrated as an example.

1. Description of Globe Valve Type Selection

Globe valve is one of the most used valves in the pipeline network. It is used in DN < 50mm water supply network. For a long time, the globe valves used in the pipeline system have the common phenomenon of "leakage, lax closure and short service life". In this regard, the selection of globe valves should be measured from the following technical aspects, and then determined:

(1) Minimum size of water-crossing section;

(2) Valve chamber flow pattern. Choose straight-through or angular globe valves as required.

(3) Stem size, body wall thickness and material of each part of the valve;

(4) The form of upper seal. As far as possible, "O" type sealing ring and high-quality filling of the cut-off valve.

Corrosion resistance. The inside and outside of the valve are not rusty and corroded, especially the water contact parts are clean and hygienic.

Select products and control the quality and performance of globe valves according to the above requirements.

2. Type Selection of Gate Valves

In the water supply network of 100mm < DN < 600mm, the traditional hard-sealed gate valve (Z41T-1.0) is often used. This kind of gate valve has some defects such as improper closing, leakage, failure of opening and closing, and maintenance is very frequent. At present, a kind of soft sealing gate valve (also known as "elastic seat gate valve") appearing in the market can basically avoid these problems.

The soft-sealed gate valve has the following characteristics: no groove at the bottom, so it will not cause the failure of tight closure; the valve plate is integrally covered with rubber, which improves the sealing performance of the valve by using the elasticity of rubber to ensure zero leakage; the upper seal structure is more reasonable, the manufacturing accuracy is high, and the multi-channel "O" rubber ring seal is adopted, which fundamentally solves the problem of easy leakage of the upper pressure cover of traditional gate valve, and also has a fundamental effect on water quality. Guarantee.

As can be seen from the table above, the price of elastic seat gate valve is 2-3 times higher than that of open stem gate valve of the same specification. But judging from the use of the elastic seat gate valve produced by Shanghai Watto Valve Co., Ltd., it is reasonable to use the soft seal gate valve, especially in the water supply network with DN less than 500 mm, regardless of the operation and maintenance cost of the valve or the reliability of the valve.