How to solve the dynamic sealing valve and static sealing problem?

How to solve the sealing problem can not be ignored, because the valve run, risk, dripping, and drain phenomenon, the vast majority took place here.



Dynamic Sealing



Dynamic seal valve, mainly refers to the stem seal. With the valve stem to prevent movement within the media leak, is the central subject of dynamic seal valve.



Stuffing Box Type



At present, the dynamic seal valve to the main stuffing. Stuffing the basic form is:



(1) gland-type



This is the most used form.



The same form can distinguish many details. For example, from the clamping bolt, the bolt can be divided into T-shaped (for the pressure of ≤ 16 kg / square centimeter of the low-pressure valve), double-headed bolts and bolts of living sections. Speaking from the gland can be divided into integral and modular.



(2) compacting Nut



This form, shape, small size, but the clamping force is restricted to use only in small valves.



Filler



Stuffing in order to fill in direct contact with the valve stem, and filled with stuffing to prevent media leakage. On the filler has the following requirements:



(1), sealing well;



(2) corrosion resistance;



(3) The friction coefficient is small;



(4) to adapt to medium temperature and pressure.



Common fillers include:



(1) packing Asbestos: asbestos packing, heat and corrosion resistance are good, but when used alone, sealing results are poor, it is always impregnated or additional other materials. Oil asbestos packing: its basic structure, there are two, one is a twisted system, the other one is knitting. Also can be divided into round and square.



(2) PTFE braided packing: The packing of PTFE thin braided belt, has an excellent corrosion resistance, but also for deep-cold medium.



(3) Rubber O-ring: In the low state, a good sealing effect. Temperature subject to limitations, such as natural rubber can be used only 60 ℃.



(4) plastic molding packing: General made three-piece, but also can be made into other shapes. PTFE is used in plastics in many, there are nylon 66 and nylon 1010.



In addition, the use of units according to their own needs, often to explore an effective form of packing. For example, in 250 ℃ steam valve, the use of asbestos and lead-lap alternately Diego packing together, the situation would reduce the steam leakage; some valves, media constantly changing, such as asbestos packing and PTFE THREAD SEAL TAPE common use, sealing effect will be better. To reduce the friction between stem, and some occasions, can be added molybdenum disulfide (M0S2), or other lubricants.



Currently, new fillers, are engaged in exploration. Such as using polyacrylonitrile fiber impregnated by PTFE emulsion, but also by the pre-oxidation, in the mold sintering suppression, can be sealed-performance molding filler; Another example is made of stainless steel sheets with asbestos filler waveform can be high temperature , high pressure and corrosion. 

 

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