Valve Flow Characteristics

Tianjin Tanggu Water-Seal Valve Co., Ltd (TWS Valve Co., Ltd)
Tianjin，CHINA
14th，August，2023
Web:www.water-sealvalve.com

Valve flow characteristics curve and classification valve flow characteristics, is in the valve at both ends of the pressure difference remains constant conditions, the medium flow through the valve relative flow and its opening between the relationship between the flow characteristics of the valve is an important technical indicators and parameters in the valve application process to make the correct selection has very important significance.

The valve flow characteristic can be defined as: the relative flow of the controlled medium through the valve, and the relationship between the relative opening (relative displacement) of the valve and the valve is called the flow characteristic of the regulating valve. Generally speaking, it is divided into four types: straight line, equal percentage (logarithm), parabola and fast open! The specific description and advantages are as follows:

First, the linear characteristic refers to the linear relationship between the relative flow rate of the valve and the relative opening, that is, the constant of the flow change caused by the change of unit opening. The relative travel of the linear characteristics is in a straight line relationship with the relative flow rate. The change in flow rate caused by the change of unit stroke is constant. When the flow rate is large, the relative value of the flow rate changes small, and the flow rate is small, the relative value of the flow rate changes greatly.

Second, the equal percentage characteristic (logarithm) means that the relative flow change caused by the change of unit opening is proportional to the relative flow rate of the point, that is, the amplification coefficient of the control valve is changing, and it increases with the increase of the relative flow. The relative stroke and relative flow of equal percentage characteristics are not in a linear relationship, and the change in flow caused by the change of unit stroke at each point of the stroke is proportional to the flow rate at this point, and the percentage of flow change is equal. Therefore, its advantage is that the flow rate is small, the flow change is small, and when the flow is large, the flow rate changes greatly, that is, it has the same adjustment accuracy in different openings.

Third, the parabolic characteristic refers to the relative flow change caused by the change of the relative opening of the unit in direct proportion to the square root of the relative flow value of this point. The flow rate varies proportionally to the two sides of the stroke, with roughly intermediate characteristics of linear and equal percentage characteristics.

Fourth, the fast opening flow characteristic refers to the larger flow when the opening is small, with the increase of the opening, the flow rate can soon reach the maximum, and then increase the opening, the flow change is very small, so it is called the fast opening characteristic.

The flow characteristics of diaphragm valves are close to the quick opening characteristics, the flow characteristics of butterfly valves are close to equal percentage characteristics, the flow characteristics of gate valves are linear characteristics, the flow characteristics of ball valves are straight lines in the middle opening and closing stage, and equal percentage characteristics in the middle opening.

In general, ball valves and butterfly valves are usually not used for adjustment, if used for adjustment, but also in the case of a small opening to play a role in regulation, generally can be classified as a quick opening type, and the real as a regulation of most of the basic globe valve, the valve head processing into such as parabolic cone, spherical, etc., will use different curve characteristics, generally used as adjustment, basically the percentage of characteristics are used more.

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