Bellows type needle valve adjusting range is big, is used to working temperature t the 200 degrees of clean medium such as air and steam piping, cannot be used for the liquid pressure, more cannot be used for containing solid particles medium in pipeline. When installation usually have filter in front of the pressure reducing valve, to ensure the pressure reducing valve sensitive and reliable.
Wiredrawing phenomenon is after mold opening mold, product formation of filaments gate, this article filaments stick on the products or to stay in a mould to form a product defect. Thermal resistance to heating of the two. Shorten the formation of needle valve, reduce the influence of valve for shuikou material. Needle valve on the drive back to a trough, thus reducing the plastic. In go brass tube fitting on permission, to decrease the size of system of the gate. Hot nozzle gate area and cooling device, reduce the valve needle front end temperature. Open system drawing phenomenon generally are common, the reason is because the plastic parts at the time of cooling, is by the gate around the cortex curing first, if the gate area when curing incomplete (gate area temperature constant input), then pull plastic mould gate area formed wiredrawing phenomenon.
Needle valve type according to different can be divided into sensitive element and structure of piston, diaphragm, spring film type, bellows type and lever type, etc. Piston type needle valve work reliable, small amount of 38 tube fitting maintenance and decompression range is larger, cover an area of an area small, wide application scope. Diaphragm type needle valve work reliability is poorer, large amount of maintenance, decompression range, small volume, covers an area of big, applies only to low temperature and pressure of water and air as the medium in pipeline.