1. Gate valve

Gate valves are used as shut-off media, and when fully open, the entire flow is through. At this time, the operating pressure of the medium is minimized.

Gate valves are usually suitable for working conditions that do not require frequent opening and closing, and maintain the gate fully open or fully closed. Not suitable for use as a regulator or throttle.

For high-speed flowing media, when the gate is partially opened, it can cause valve vibration, which may damage the sealing surfaces of the gate and valve seat. Throttling can cause the gate to be eroded by the medium.

The main difference in structural form is the form of sealing components used.

According to the form of sealing components, gate valves are often divided into several different types, such as wedge gate valves, parallel gate valves, parallel double gate valves, wedge double gate valves, etc. The more commonly used forms are wedge gate valves and parallel gate valves.

2. Globe valve

The stem axis of the globe valve is perpendicular to the sealing surface of the valve seat. The opening or closing stroke of the valve stem is relatively short.

Once the valve disc of a globe valve is in an open position, there is no longer contact between its seat and the sealing surface of the disc, resulting in less mechanical wear on its sealing surface. As most globe valves have seats and discs that are relatively easy to repair, there is no need to remove the entire valve from the pipeline when replacing sealing components. This is very suitable for situations where the valve and pipeline are welded together. The above characteristics make the globe valve very suitable for use as a medium for cutting, adjusting, and throttling.

When the medium passes through such valves, the flow direction changes. Therefore, the flow resistance of the shut-off valve is higher than that of other valves.

There are several commonly used globe valves:

Angle globe valve: In an angle globe valve, the fluid only needs to change direction once, so that the pressure passing through the secondary valve is smaller than that of a conventional structure globe valve.

Direct current globe valve: In a direct current or Y-shaped globe valve, the flow of the valve body forms a diagonal line with the main flow path, which reduces the degree of damage to the flow state compared to conventional globe valves. Therefore, the pressure loss through the valve is correspondingly reduced.

Plunger type globe valve: This form of globe valve is a deformation of conventional globe valves. In this valve, the disc and seat are usually designed based on the plunger principle. The valve disc is polished into a plunger and connected to the valve stem, and the sealing is achieved by two elastic sealing rings placed on the plunger.

Two elastic sealing rings are separated by a sleeve ring, and the sealing ring around the plunger is pressed firmly by the load applied to the valve cover by the valve cover nut. The elastic sealing ring can be replaced and can be made of various materials. This valve is mainly used for "opening" or "closing", but each has a special form of plunger or special sleeve ring, which can also be used to regulate flow.

3. Butterfly valve

The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical channel of the butterfly valve body, the disc-shaped butterfly plate rotates around the axis, with a rotation angle between 0 and 90 degrees. When it rotates to 90 degrees, the valve is fully open

Butterfly valves have a simple structure, small size, and light weight, consisting only of a few components. And it only needs to rotate 90 degrees to quickly open and close, with simple operation. At the same time, this valve has good fluid control characteristics. When the butterfly valve is in the fully open position, the thickness of the butterfly valve is the only resistance when the medium flows through the valve body, so the pressure drop generated through the valve is very small. Butterfly valves have two sealing forms: elastic seal and metal seal. Elastic sealing valve, the sealing ring can be embedded on the valve body or around the butterfly plate.

Valves with metal seals generally have a longer lifespan than those with elastic seals, but it is difficult to achieve complete sealing. Metal seals can adapt to higher working temperatures, while elastic seals have the defect of being limited by temperature.

If a butterfly valve is required for flow control, the main thing is to choose the correct size and type of valve. The structural principle of butterfly valves is particularly suitable for making large-diameter valves. Butterfly valves are not only widely used in general industries such as petroleum, gas, chemical, and water treatment, but also in cooling water systems of thermal power plants.

There are two commonly used types of butterfly valves: clamp type butterfly valve or flange type butterfly valve:

A clamp type butterfly valve is a valve that is connected between two pipe flanges using double headed bolts.

A flange type butterfly valve is a valve with a flange, which is connected to the pipeline flange by bolts at both ends of the valve.

4. Ball valve

Ball valves have evolved from rotary valves. It has the same 90 degree rotation action, but the difference is that the plug body is a sphere, with a circular through-hole or channel passing through its axis.

The ratio between the sphere and the channel should be such that when the sphere rotates 90 degrees, it should all appear spherical at the inlet and outlet, thereby cutting off the flow.

Ball valves can be tightly closed with only 90 degrees of operation and minimal rotational force. The safe and equal valve chamber provides a small resistance and straight flow path for the medium.

It is generally believed that ball valves are most suitable for direct opening and closing use, but recent developments have designed ball valves to have throttling and flow control functions.

The main characteristics of ball valves are compact structure, easy operation and maintenance, suitable for general working media such as water, solvents, acids, and natural gas, and also suitable for harsh working conditions such as oxygen, hydrogen peroxide, methane, and ethylene. The valve body of a ball valve can be integral or modular.

5. Check valve

Check valves only allow medium to flow in one direction and prevent flow in the opposite direction. Usually, check valves operate automatically, and under the pressure of fluid flowing in one direction, the valve disc opens; When the fluid flows in the opposite direction, the flow is cut off by the fluid pressure, the weight of the valve disc, and the action of the valve disc on the valve seat.

Check valves include swing check valves and lift check valves.

The swing check valve has a hinge mechanism and a valve disc that is like a door, freely leaning against the inclined valve seat surface.

In order to ensure that the valve disc can reach the appropriate position on the valve seat surface every time, the valve disc is set in a hinge mechanism, so that the valve disc has enough swing space and truly and comprehensively contacts the valve seat.

The valve disc can be made entirely of metal, or it can be embedded with leather, rubber, or synthetic covering on the metal, depending on the performance requirements.

When the swing check valve is fully open, the fluid pressure is almost unobstructed, so the pressure drop through the valve will be relatively small.

The disc seat of the lift check valve is located on the sealing surface of the valve seat on the valve body. Except for the valve disc, which can be freely raised and lowered, the rest of the valve is like a globe valve. Fluid pressure lifts the valve disc from the sealing surface of the valve seat, and the medium reflux causes the valve disc to fall back onto the valve seat, cutting off flow.

According to the applicable conditions, the valve disc can be an all metal mechanism, or it can be embedded with rubber pads or rubber rings on the valve disc holder.

Like globe valves, the passage of fluid through lift check valves is also narrow, so the pressure drop through lift check valves is greater than that of swing check valves, and the flow rate of swing check valves is limited very little.

Select valves according to the adjusted medium parameters.

In the production process, in order to ensure that the pressure, flow rate and other parameters of the medium meet the requirements of the process flow, it is necessary to install an adjustment mechanism to adjust the above parameters.

The main working principle of the regulating mechanism is to adjust the above parameters by changing the flow area between the valve disc and the valve seat.