Brief introduction to water meter knowledge

The difference between shut-off valve and gate valve: A shut-off valve is a valve that moves a closing member (valve) along the centerline of the valve seat. Depending on the form of motion of the flap, the change in the seat opening is proportional to the flap travel. Since the valve stem has a relatively short opening or closing stroke and the cutting function is very reliable, and because the valve seat opening is proportional to the stroke of the flap, it is very suitable for adjusting the flow. Therefore, this type of valve is well suited for cutting or conditioning and throttling. The selection principle is:

1. The shut-off valve is applied to pipes or devices of high temperature and high pressure medium.

2. On the pipeline where the flow resistance is not strict. In other words, places where pressure loss is not considered.

3. Small valves can be used with needle valves, instrument valves, sampling valves, pressure gauge valves, etc.

4. There are flow adjustment or pressure adjustment, but the adjustment accuracy is not high, the pipe diameter is relatively small.

5. In the desiliconization workshop and the easy coking pipe for producing alumina Bayer method, it is easy to choose DC shut-off valve or DC throttle valve, the valve body is separated, the valve seat can be removed, and the carbide sealing pair.

6. In water supply and heating projects for urban construction, it is known that through smaller pipes, cut-off, balancing valves or plunger valves can be used. The most obvious advantage is that during the opening and closing process, the friction between the valve flap and the sealing surface of the valve body is less than the friction of the gate valve, and therefore wear resistance. The opening height is usually only 1/4 of the diameter of the seat channel and is therefore much smaller than the gate valve. Usually there is only one sealing surface on the valve body and the valve flap, so the manufacturing process is better and easier to repair.

Different materials are used for water, steam, oil, nitric acid, acetic acid, oxidizing media, urea and other media. The opening and closing member of the gate valve is a gate. The direction of movement of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, not suitable for adjustment and throttling. The door has two sealing faces. The two sealing faces of the most commonly used wedge gate valves form a wedge shape. The wedge angle varies with valve parameters and is typically 5o. The gate of the wedge gate valve can be made into a whole, called a rigid gate; it can also be made into a gate that can produce a small amount of deformation to improve its processing performance and compensate for the deviation of the sealing surface angle during processing. This plate is called an elastic baffle. When the gate valve is closed, the sealing surface can only be sealed by medium pressure, that is to say, the sealing surface of the pressure head is pressed against the valve seat on the other side by medium pressure to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves are forced to seal, that is, when the valve is closed, external forces are forced to press the gate onto the seat to ensure a sealed seal surface.

The gate valve has the following advantages:

1. The fluid resistance is small, and the sealing surface is less washed and eroded by the medium.

2. Opening and closing is more laborsaving.

3. The flow direction of the medium is not limited, and does not interfere with the flow or reduce the pressure.

4. The utility model has the advantages of simple shape, short structure length, good manufacturing process and wide application range.

Different materials are used for water, steam, oil, nitric acid, acetic acid, oxidizing media, urea and other media.

There are other advantages in adjusting the flow without using a gate valve:

Due to the different structure, the frictional surface between the valve body and the valve seal is small during the opening and closing of the shut-off valve, so the wear resistance is good
The size of the shutoff valve of the same nominal diameter is much smaller than the size of the gate valve.
The valve body and the valve flap of the shut-off valve have only one sealing surface, and the manufacturing process is good and the maintenance is convenient, but the shut-off valve is also opposite to the gate valve.

Disadvantages: The flow resistance coefficient of the shut-off valve is greater than the flow resistance coefficient of the gate valve, and the pressure loss is also large.