What is flow resistance of valve？

The flow resistance of the valve is the medium circulation of the valve at different degrees and the pressure loss after the medium passes through the valve. The circulation capacity and pressure loss of the valve are important parameters in the selection, use and design of the valve.

 Why the valve has a cut device？

For valves used as cutters, the purpose of using such valves is to cut off a part of the circuit. Therefore, the valve must ensure excellent sealing, when the circuit equipped with this kind of valve works normally, the valve should be fully open, and as far as possible, so the flow test of this kind of valve is mainly to determine the flow resistance coefficient in the fully open state. The flow resistance coefficient of various valves is different, even if the same valve, because the structure and flow channel are different, its flow resistance coefficient is also significantly different. Through the test, we can find out the various factors affecting the flow resistance coefficient of the valve, so as to improve the structural design, reduce the fluid resistance of the valve, and make it consume as little energy as possible.

 What is the flow rate and pressure of the valve？

The valve used to regulate the flow rate or pressure produces a large pressure loss, and the size of the pressure loss varies with the opening and closing position of the valve. The flow test of this kind of valve is mainly to determine the flow coefficient under different opening degrees. Through the test and improvement, the adjustment performance of the valve can be improved. In order to facilitate the use, the calculation formula of flow rate, flow rate conversion and flow resistance coefficient of all kinds of valves are listed (Table 1-1~ Table 1-3).

Where the volume flow rate of Q —— liquid, m³ / s;

A- -Broken area of the pipeline, m²;

V- -Average flow rate in the pipeline, m/s;

And d- -caliber, m.

Q(L/min)=Q(m³/s)×1000×60

Q(m³/h)=Q(L/min)×60/1000

Table 1-1 Base flow rate (liquid)

Table 1-2 Conversion Table of flow rate and flow rate Unit: L / min

Table 1-3 Flow resistance coefficient of various valves is ζ

Note: 1. Data of gate valve is suitable for parallel double gate structure,

2. When the ball valve is not reduced in diameter, the value of 5 is very small, the fluid resistance loss is only equivalent to the pipe with the same diameter (the length of the pipe is equal to its structure length), and the flow resistance coefficient is generally about 0.1.
3. The g of butterfly valve is mainly related to the shape of butterfly plate and the relative thickness of the plate: diamond plate ξ 0.05~0.25; and cake plate ξ 0.18~0.6.
4. The flow resistance coefficient of straight-through diaphragm valve is less than that of weir diaphragm valve, which is generally 0.6~0.9.