Needle valve flow coefficient of the calculation with the following formula: Q - big flow m3 / h; The proportion of G - (1) is commonly used in; P1 - inlet pressure bar; The P2 - outlet pressure bar; Delta P = (P1, P2 bar. And Cv with Kv relationship is as follows: Cv = 1.17 Kv, accurate, actually That Cv = 1.167 Kv, and Kv and Kvs is considerable.
But in theory, in different air conditioning circuit, 忖 P value is different, is a dynamic change of value, the influence of the Cv/Kv calculation. At constant when the needle valve type kg 忖 P selection, the greater the corresponding diameter is small, the medium Qualitative but the greater the ability to control, but hydraulic fitting manufacturer the smaller the flow capacity is, small diameter of needle valve can not meet the capacity requirements of system on the one hand, on the other hand type needle valve will need through the system to provide the large pressure difference in order to maintain sufficient flow, increase the load of the pump.
Type, needle valve vulnerable; Valve diameter will make the control performance is poor, easy to make the system impact and oscillation, and investment will increase, the needle valve type had greater than small will be the consequences of control valve life expectancy and maintenance inconvenience.
Import needle valve can be divided into stainless steel valve, valve and chrome molybdenum steel carbon steel needle valve type. Usually, and USES the form of the structure to have commonly: thread the needle valve, ferrule needle valve type valve, flange, welding needle valve, Angle type type needle valve and pressure gauge Valve type valve, level gauge, the Duo function needle valve, pressure meter hand type sampling valve, needle valve, etc.
Instrument valve group usually has two valves, three valves group and five valve group. Instrument valve in the pipe system measuring instrument to open and close pipe channel. Due to fire, explosion, high pressure resistance and excellent sealing performance, it is a power plant, oil refinery Plant, chemical plant and equipment measure the important products in the pipeline. Type needle valve is typically used for simple measurement in the pipeline, and instrumentation valve group is used for more complex in the pipeline for separation and merger.
Needle valves open and close type needle valve device drivers use a powered device, use the drive device is designed to make the valve easy operation convenient, fast and reliable, or automatic control and remote control, is to drive the basic requirement, torque or thrust Meet the needs of the opening and closing of the valve, the stroke and the torque control accurate, reliable and suitable for dynamic selection of site condition, opening and closing actions conform to the requirements of the control, light and small device itself.
Type needle valve actuating device according to the output shaft is divided into many rotary movement way, part of the rotary and linear reciprocating 3 kinds. Rotary rotary is more circle, more suitable for the stem or stem nut revolving circle is needed to open or close the valve, such as gate valves, cut Check valve, series of the output torque value is commonly 40 ~ 10000 cattle meters (thrust of 20 ~ 1.1 million cows). Part of the rotary is suitable for the stem within a circle in the rotation can be fully open or close the valve, such as hydraulic fitting supplier ball valve, butterfly valve, the output torque of the series is commonly 125 ~ 125000). Linear reciprocating applicable to stem only do linear reciprocating motion can be fully open or close the valve, such as solenoid valve. Type needle valve actuating device according to the power source can be divided into manual gear, gear, pneumatic device, electric actuator, hydraulic device, gas-liquid linkage, electro-hydraulic linkage and so on. The simple valve actuator is hand wheel, handle, with the needle valve , large-scale and automation of production process of all kinds of needle valve actuator needs more and more.