Regulators are used to regulate the flow, pressure and level of the media. According to the adjustment part signal, the opening of the valve is automatically controlled to achieve the adjustment of the medium flow, pressure and liquid level. The regulating valve is divided into an electric regulating valve , a pneumatic regulating valve and a hydraulic regulating valve.
The regulating valve is composed of an electric actuator or a pneumatic actuator and a regulating valve. It is usually divided into two types: straight-through single-seat control valve and straight-through two-seat control valve. The latter has the characteristics of large flow capacity, unbalanced operation and stable operation, so it is usually especially suitable for large flow, high pressure drop and leakage. Less occasions.
The flow capacity Cv is one of the main parameters for selecting the regulating valve. The flow capacity of the regulating valve is defined as: when the regulating valve is fully open, the pressure difference between the two ends of the valve is 0.1 MPa, and when the fluid density is 1 g/cm3, the flow path per hour The flow rate of the regulating valve is called the flow capacity, also called the flow coefficient, expressed in Cv, the unit is t/h, and the Cv value of the liquid is calculated by the following formula.
According to the table of the flow capacity Cv value, the nominal diameter DN of the regulating valve can be determined.
The flow characteristic of the regulating valve is 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 across the valve is kept constant. The flow characteristics of the regulating valve are linear, equal percentage and parabolic. The significance of the three fluence characteristics is as follows:
(1) The relative stroke and the relative flow rate of the equal percentage characteristic (logarithm) are not linear. The change of the flow caused by the change of the unit stroke at each point of the stroke is proportional to the flow at this point, and the percentage of the flow change It is equal. Therefore, its advantage is that the flow rate is small, the flow change is small, and when the flow rate is large, the flow rate changes greatly, that is, the same adjustment precision is obtained at different opening degrees.
(2) Linear characteristic (linear) The linear relationship between the relative stroke and the relative flow is linear. The change in flow caused by changes in unit stroke is constant. When the flow rate is large, the relative value of the flow changes little, and when the flow rate is small, the relative value of the flow changes greatly.
(3) The parabolic characteristic flow rate varies proportionally to the two sides of the stroke, and generally has an intermediate characteristic of linear and equal percentage characteristics.
It can be seen from the analysis of the above three characteristics that, in terms of its adjustment performance, the equal percentage characteristic is excellent, the regulation is stable, and the adjustment performance is good. Parabolic characteristics are better than linear characteristics, and any of the flow characteristics can be selected according to the requirements of the application.
The regulating valve is composed of an electric actuator or a pneumatic actuator and a regulating valve. It is usually divided into two types: straight-through single-seat control valve and straight-through two-seat control valve. The latter has the characteristics of large flow capacity, unbalanced operation and stable operation, so it is usually especially suitable for large flow, high pressure drop and leakage. Less occasions.
The flow capacity Cv is one of the main parameters for selecting the regulating valve. The flow capacity of the regulating valve is defined as: when the regulating valve is fully open, the pressure difference between the two ends of the valve is 0.1 MPa, and when the fluid density is 1 g/cm3, the flow path per hour The flow rate of the regulating valve is called the flow capacity, also called the flow coefficient, expressed in Cv, the unit is t/h, and the Cv value of the liquid is calculated by the following formula.
According to the table of the flow capacity Cv value, the nominal diameter DN of the regulating valve can be determined.
The flow characteristic of the regulating valve is 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 across the valve is kept constant. The flow characteristics of the regulating valve are linear, equal percentage and parabolic. The significance of the three fluence characteristics is as follows:
(1) The relative stroke and the relative flow rate of the equal percentage characteristic (logarithm) are not linear. The change of the flow caused by the change of the unit stroke at each point of the stroke is proportional to the flow at this point, and the percentage of the flow change It is equal. Therefore, its advantage is that the flow rate is small, the flow change is small, and when the flow rate is large, the flow rate changes greatly, that is, the same adjustment precision is obtained at different opening degrees.
(2) Linear characteristic (linear) The linear relationship between the relative stroke and the relative flow is linear. The change in flow caused by changes in unit stroke is constant. When the flow rate is large, the relative value of the flow changes little, and when the flow rate is small, the relative value of the flow changes greatly.
(3) The parabolic characteristic flow rate varies proportionally to the two sides of the stroke, and generally has an intermediate characteristic of linear and equal percentage characteristics.
It can be seen from the analysis of the above three characteristics that, in terms of its adjustment performance, the equal percentage characteristic is excellent, the regulation is stable, and the adjustment performance is good. Parabolic characteristics are better than linear characteristics, and any of the flow characteristics can be selected according to the requirements of the application.
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