Needle valve principle and installation

Posted by uuuseff on November 17th, 2019

A needle valve is a valve that can be precisely adjusted for a wide range of uses, such as cutting torches for flame cutting and adjusting the temperature of the flame to a needle valve. Gauge needle valve is an important part of instrumentation piping system, there are stop valve and ball valve, its function is to open or cut off the pipeline access. The needle valve spool is a very sharp cone, like a needle inserted into the seat, hence the name. The role of any valve is to shut off the fluid. According to the different spool, can be divided into globe valve, gate valve, plug valve, ball valve, butterfly valve, needle valve and so on. Needle valve valve than other types of valves to withstand greater pressure, good sealing performance, it is generally used for smaller flow, high pressure gas or liquid medium seal. Needle valve type and pressure gauge with the most appropriate use of the general needle valve made of thread connections. Anticorrosion valve needle First of all anti-corrosion valve body, the main choice is the correct material. Although the anti-corrosion information is very rich, but it is not easy to choose the right thing, because the problem of corrosion is very complicated. The difficulty of choosing the valve body material lies in that it can not only consider the corrosion problem, but also must consider the ability of pressure and temperature resistance, economically reasonable and easy to purchase and other factors. Followed by the lining measures, such as lead-lined, lined with aluminum, lining engineering plastics, lined with natural rubber and various synthetic rubber. This is a saving method if the media conditions permit. Third, in the pressure, the temperature is not high, the valve body with non-metallic materials, often very effective control of corrosion. In addition, the outer surface of the needle valve body is also subject to atmospheric corrosion, the general steel materials are to paint to protect. Needle Valve Installation Notes 1) Installation location, height, direction of import and export must meet the design requirements, pay attention to the flow direction of the medium should be consistent with the direction of the arrow marked by the body, the connection should be strong and tight. 2), the appearance of the valve must be installed before the inspection, the valve nameplate should be consistent with the current national standard "General Valve Flags" GB 12220 requirements. For the working pressure is greater than 1.0 MPa and the main pipe to play the role of cut-off valve, the installation should be carried out before the intensity and tightness test, qualified after the standard use. Strength test, the test pressure of 1.5 times the nominal pressure, the duration of not less than 5min, valve housing, packing should be no leakage as qualified. Tightness test, the test pressure of 1.1 times the nominal pressure; test duration in line with the requirements of GB 50243. The principle of selection of various types of needle valves 1, low temperature medium piping systems and devices, should use the valve cover with a low temperature needle valve. 2, oil refining unit of the catalytic cracking unit piping system, optional lifting rod needle valve. 3, acid and alkali chemical systems and other corrosive media and piping systems, should be made of austenitic stainless steel, PTFE valve seat ring all-stainless steel needle valve. 4, Metallurgical systems, power systems, petrochemical plants, urban heating systems in high temperature medium piping systems or devices, the choice of metal to metal seal needle valve. 5, the need for flow control, the choice of worm-driven, pneumatic or electric with V-shaped opening of the needle valve. 6, oil, natural gas pipeline delivery, need to clean the pipeline, but also need to be buried in the ground, the choice of full diameter, all-welded needle valve structure; buried in the ground, the choice of full-diameter welding connection or flange connection Ball valve 7, refined oil pipeline and storage equipment, the choice of flanged needle valve. 8, city gas and natural gas pipeline, the choice of flange connection and internal thread connection needle valve. 9, oxygen pipeline system in the metallurgical system, should be adopted after strictly degreasing, flanged needle valve.

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