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Regulating valve flow characteristics

From:Net   Date:2012-3-5

 

Equal percentage valve characteristic linear characteristic, parabolic characteristic

Regulating valve for regulating the flow of media, pressure and level. Parts based on the adjusted signal, the automatic control of the valve opening, so as to achieve medium flow, pressure and level adjustment. Regulating valve of electric control valve, pneumatic control valves and hydraulic control valve. Commonly used is the electric control valves and pneumatic control valve two kinds.

Regulating valve by electric actuators or pneumatic actuator and control valve two parts. Regulating valve is usually divided into through a single seat type regulating valves and straight-through two-seater regulator valve, the latter has a flow capacity, imbalances do small and stable operation characteristics, it is usually especially suitable for high flow, high pressure drop and leakage few occasions.

Cv flow capacity is to select one of the main parameters regulating valve, regulating valve flow capacity is defined as: when the control valve fully open, the pressure differential across the valve is 0.1MPa, the fluid density is 1g/cm3 per hour flow path the flow control valve number, called flow capacity, also known as flow coefficient Cv expressed in units of t / h.

Flow capacity Cv value based on the size of look-up table, we can determine the control valve nominal diameter DN.

Regulating valve flow characteristics, differential pressure across the valve is kept under constant conditions, the medium flows through the valve and the relative relationship between the degree of opening it. Regulating valve flow characteristics are linear features, such as the percentage of properties and parabolic characteristic three. Three kinds of Fluence features the following meanings:

(A) the percentage of properties (logarithmic)

Equal percentage relative stroke and not a linear relationship between the relative flow, the trip unit trip at each point changes flow changes caused by the flow rate is proportional to this point, the percentage change in flow rate are equal. So it has the advantage of traffic hours, the flow change is small, the flow rate, the flow changes, which is in a different opening degree, the same regulation accuracy.

(2) linear characteristic (linear)

Linear characteristic relative stroke linear relationship between the relative flow. Unit itinerary changes caused by the flow change is constant. Flow, the flow rate changes relative value, flow hours, the flow rate variation in relative value.

(3) parabolic characteristic

The two flows are proportional to the square itinerary changes, generally with linear and equal percentage of intermediate characteristics.
From the above analysis we can see three characteristics, in terms of their regulation performance to equal percentage characteristic is the best, its regulation and stability, regulation and good performance. The parabolic characteristic off than linear characteristic good regulating performance, according to the different requirements using the occasion, pick any one flow characteristics.

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