The valve packing technology do you understand

by:J&T     2020-06-26
Valve is pipeline installation, chemical water pump flow control of commonly used equipment, valve leakage is very troublesome is a serious problem, the valve packing is leakage prevention and control of dissipation range includes volatile harmful substances leaking & ndash; — Prevent environmental pollution, including steam and other low temperature inert medium leakage & ndash; — To prevent the production efficiency lower. From the source to prevent leakage, it should be said that the default choice. In particular, need careful design shell, reasonable selecting packing material and structure, and correct installation. Usually within the stuffing box can accommodate four to six packing ring, and the valve stem packing element, less one to two, much as rising stem structure, there may be seven packing ring. Packing ring can use braided rope method or moulding molding in manufacturing. Braided rope method of manufacture of packing material, can according to the circumference of the spindle/stem length cut into segments and incision & 45 ordm; ( Miter) Or 90 & ordm; ( Vertical) 。 Recommend the miter method is adopted, because under the action of axial load can obtain better face combination effect. Must pay attention to, each packing ring must be complete around the spindle/stem the circumference of a circle; Good state is, packing ring tightness between the outer and the inner wall of the stuffing box, above the tightness of the medial between stem and packing ring. If the incision of packing line head is too long lead to stack, or too short, can lead to packing ring density is uneven, a potential leak paths. A, turn the valve rod stuffing box is also to ensure clean without impurities and grease. Put before a packing ring in a stuffing box, pay attention to the position of the interface, should first of all, the interface part into stuffing box, and then into the rest of the packing rings. If it is a flexible graphite molded packing ring, shall each ring tensile into spiral again after installed, in order to avoid packing ring damage. Every time you install a packing ring, ensure it is within the packing after compaction and filled, can install the next. If the length of the gland follower is not enough to reach the bottom of the stuffing box, when installing the packing ring require temporary ring auxiliary tools or lengthen. Unless you have specific provision, sealing element can not be smooth processing. In accordance with the manufacturers specifications, installed on the first packing ring applied load. Repeat the same steps to a packing ring, only install one at a time. Any two adjacent packing ring their interfaces, must be respectively in 90 & ordm; And 180 & ordm; The location of the. After the installation is complete, must operate the valve stem, circulation in the position of the figure, the valve is in three to ten times, in order to ensure the packing group sit properly. In this process, packing group can produce a degree of relaxation, so switch operation finished, shall, in accordance with the manufacturer to provide the parameters of the retightened, in order to have enough margin to offset the relaxation in the future. By the same token, the valve according to the normal working condition after put into use, once after fastening should be made for packing group for the stress relaxation will happen in future reserve enough margin. Second, avoid leak if properly installed packing, the axial stress into radial stress will reduce attenuation. This helps to packing in a longer time to maintain reliable sealing performance, and reasonable friction load distribution. On this basis, the dissipation of valve leak sealing performance, and the production efficiency will be improved significantly. If the valve packing several drops of liquid leakage per minute, still can be accepted. The current era, the legislative orientation of the government is to eliminate the leakage, and introduced the related regulations, procedures, to find, reduce and control valve leakage dissipation. In addition, manufacturers and end users require valves smoothly through a variety of standard test, such as ISO15848 - 1, API 624 and API 641. The correct packing installation procedure is one of the elements of decision sealed performance is qualified or not. The sealing performance is whether the value of the valve supplier beyond the colleague's important symbol. Three, temperature limit only at a certain temperature range, packing and sealing material can have performance. For example, ptfe ( PTFE) The temperature range is about between 101 ℃ and 232 ℃ below zero. If applied to the higher environmental temperature, its molecular structure is likely to change, lead to harmful gas leak, and corrosion in the stem, and even lead to toxic ptfe flue gas escaping from the top of the gland follower. This kind of flue gas could even carcinogenicity. In addition with flue gas release, the packing material will soften, reduces weight, and lead to harmful process medium leakage, leakage or product. If using flexible graphite, it is suitable for the temperature range of different nature. In the oxidizing atmosphere, generally is between 196 ℃ and 450 ℃ below zero. Considering the material characteristics, such as ash, sulfur chloride, and the content of fluoride and other halogen compounds and the oxidation of manufacturers to provide quality information loss, can determine high graphite packing can be reliable in the 450 ℃ environment to prevent leakage and dissipation in the oxidizing reaction not steam condition, high-energy under 650 ℃. Flexible graphite and ptfe ( PTFE) Are widely used in the PH value 0 All kinds of medium; Graphite material in some cases also applies to the fire safety seal.
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