The flow rate and flow rate of the valve mainly depend on the diameter of the valve, and it is also related to the resistance of the valve structure to the medium.

The flow channel area of the valve has a direct relationship with the flow rate and flow rate, and the flow rate and flow rate are two interdependent quantities. When the flow rate is constant, the flow rate is large, the flow channel area can be smaller; the flow rate is small, the flow channel area can be larger. Conversely, the larger the flow channel area, the smaller the flow rate; the smaller the flow channel area, the larger the flow rate.

The flow rate of the medium is large, the valve diameter can be smaller, but the resistance loss is large, and the valve is easily damaged. If the flow rate is large, it will have electrostatic effect on flammable and explosive media, causing danger; if the flow rate is too small, the efficiency will be low and not economical. For viscous and explosive media, a smaller flow rate should be used. The flow rate of oil and liquid with high viscosity should be selected according to the viscosity, generally 0.1 ~ 2m/s.

In general, the flow rate is known and the flow rate can be determined empirically. The nominal diameter of the valve can be calculated from the flow rate and flow.

The valve diameter is the same, its structure is different, and the fluid resistance is also different. Under the same conditions, the larger the resistance coefficient of the valve, the more the flow rate and flow rate of the fluid passing through the valve will decrease; the smaller the valve resistance coefficient, the less the flow rate and flow rate of the fluid passing through the valve will decrease.

The selection of valve diameter should take into account the machining accuracy and dimensional deviation of the valve, as well as other factors. The valve diameter should have a certain margin, generally 15%. In actual work, the valve diameter depends on the diameter of the process pipeline.