Needle Valve Connection fastening
Needle valve is an important part of the instrument measuring pipeline system, mainly with cut-off valve and ball valve, its function is to open or cut off the pipe path.
It has the advantages of easy installation and disassembly, quick connection, favorable fireproof, explosion-proof and high pressure resistance, good sealing performance, etc. It is an advanced in power station, oil refining, chemical device and instrument measuring pipeline. Connection of the valve.
Needle valve seal is good, long life, even if the sealing surface damage, only need to replace the vulnerable parts, you can continue to use. The flow direction of the medium should be the same as the direction of the arrow on the valve body. Manual shut-off valve, ball valve can be installed in any position on the pipeline. High sealed sampling valve sealing performance refers to the sealing parts of the valve to prevent the ability of media leakage, it is the most important technical indicators of the valve. The sealing part of the valve has three parts: the contact between the opening and closing parts and the sealing surface of the valve seat; the filling of the packing and the stem and the stuffing box; the connection of the valve body and the valve cover. One of the previous leak is called the internal leakage, which is usually said lax, it will affect the ability of the valve to cut off the media. For the cut-off valve class, the internal leakage is not allowed. After the two leaks called leakage, that is, the media leak from the valve to the valve outside. Leakage will cause material loss, pollution of the environment, serious will cause accidents. For flammable and explosive, toxic or radioactive media, leakage is not allowed, so the valve must have a reliable sealing performance.
The media flow through the valve will have a pressure loss (both before and after the valve pressure difference), that is, the valve flow of the media have a certain resistance to the media to overcome the resistance of the valve will consume a certain amount of energy. From the energy conservation considerations, the design and manufacture of valves, as far as possible to reduce the valve on the flow medium resistance.
Hoisting force and opening and closing torque refers to the valve opening or closing must be applied to the force or torque. When closing the valve, it is necessary to form a certain sealing pressure between the opening and closing parts and the sealing surface of the opening, and also between the stem and the packing, between the stem and the nut thread, the stem end support and Other friction parts of the friction, which must impose a certain closing force and closing torque, the valve in the opening and closing process, the required opening and closing force and opening and closing torque is changing, the maximum value is closed in the final instantaneous or open The initial moment. Design and manufacture of valves should be designed to reduce their closing force and closing torque. The opening and closing speed is expressed by the time required to complete the opening or closing operation of the valve. Generally on the valve opening and closing speed without strict requirements, but some conditions on the opening and closing speed have special requirements, if any requirements quickly open or closed to prevent accidents, and some requirements to close slowly to prevent water hammer, This should be taken into account when selecting valve types.
This refers to the valve for the media parameters change, make the appropriate response to the degree of sensitivity. It is a very important technical performance index for valve and valve with special function such as throttle valve, pressure reducing valve and regulating valve, which are used to adjust the parameters of medium and safety valve and trap.
Service life indicates the degree of durability of the valve, is an important indicator of the performance of the valve, and has great economic significance. Usually to ensure that the sealing requirements of the opening and closing times to represent, can also be used to express the time.
