Introduction to the minimum flow control valve and what are the flow characteristics of the control

Minimum Flow Control Valve The minimum flow control valve is also known as the boiler feed pump recirculation valve. In power plants it is installed at the outlet of the feed pump and connected to the deaerator. The boiler feed pump sucks the water out of the deaerator and sends it to the boiler.

In order to prevent overheating of the feed pump and to prevent cavitation, the flow rate of the feed pump must in any case not be less than a specified safe flow rate, i.e. the minimum flow rate. When the boiler feed water needs to flow very small, such as when the steam turbine trips, the minimum flow valve needs to be opened in time to return a part of the high-pressure water from the pump outlet to the deaerator to ensure the safe operation of the feed pump. The system in which this valve is located is called a recirculation system.

Here are some of the well-known brands recognized in the valve industry, which are widely recognized and have a high reputation. While rankings may vary depending on time and market conditions, the following brands are generally considered to be among the top brands in the valve industry:

The following are the top ten domestic first-line valve brand manufacturers in 2022-2023, but for reference only: Suzhou Neway Valve Co., Ltd., Shanghai Guanlong Valve Machinery, Shanghai Qizhong Valve Manufacturing, Sanhua, Su Yan, Shentong, Su Valve, Nanfang, Jiang.

First, the word Yao. The above manufacturers are only estimates and references, and the specific situation may vary or fluctuate at any time due to changes in a series of factors such as changes in the market, the size of the competition pattern, and the stability of product quality. As an indispensable key device in industrial production and civil facilities, the quality and reputation of the valve brand directly affect the satisfaction and trust of users.

These brands are known in the valve industry for their innovative technology, high-quality products and reliability. It is important to note that the market and industry are evolving rapidly, and different rankings may vary depending on time and region. For the most up-to-date ranking information, it is recommended to refer to industry reports, professional organizations or market research data for more detailed and accurate information.

The relationship between the relative flow rate q qmax and the relative opening l lmax of the control valve: q qmax = f (l lmax).

The relationship between the relative flow rate q qmax of the control valve and the relative opening l lmax and the pressure difference on the valve: q qmax=f(l lmax) (dp1 dp) 1 2).

The inherent flow characteristics of the control valve itself depend on the shape of the spool, the simplest of which is the linear flow characteristicThe relative flow rate of the control valve is in a linear relationship with the relative opening, that is, the flow change caused by the change of a single stroke is a constant.

There is no definite formula for calculating the relationship between valve opening and flow rate and pressure. Their relationship can only be expressed as a general function, and the specific test curve should be checked.

Different flow characteristics will have different valve openings, and the quick-opening flow characteristics will vary greatly at first, and then be relatively gentle. The linear flow characteristics are that the opening of the valve is proportional to the flow rate, that is to say, the valve opening reaches 50%, and the flow rate of the valve also reaches 50%.

The flow characteristics of the regulating valve are the relationship between the relative flow rate of the medium flowing through the regulating valve and its opening under the condition that the pressure difference between the two ends of the valve remains constant. There are three types of flow characteristics of the control valve: linear characteristics, equal car cluster ratio characteristics and parabolic characteristics. The significance of the three note characteristics is as follows:

Equal percentage characteristic (logarithmic).

The relative stroke and the relative flow of the equal percentage characteristic are not in a straight line, and the change in flow caused by the change in the unit stroke at each point of the stroke is proportional to the flow rate at that point, and the percentage change in flow is equal. Therefore, its advantage is that the flow rate is small, and when the flow rate is large, the flow rate changes greatly, that is, it has the same adjustment accuracy in different openings.

Linearity (linearity).

The relative travel and flow of the linear properties are in a linear relationship. The change in flow rate caused by the change in the unit stroke is constant. When the flow rate is large, the relative value of the flow rate changes slightly, and when the flow rate is small, the relative value of the flow rate changes greatly.

Parabolic characteristics.

The flow rate varies proportionally to the two sides of the stroke, and generally has the intermediate closed-letter cherry characteristics of linear and equal percentage cancellation.

From the analysis of the above three characteristics, it can be seen that in terms of its regulation performance, the equal percentage characteristics are the best, and its regulation is stable and the regulation performance is good. The parabolic characteristics are better than the adjustment performance of the linear characteristics, and any of the flow characteristics can be selected according to the requirements of different use occasions.