Talking about the Reason of Valve Leakage and Optimization of Its Design Type

Abstract: With the constant development and expansion of the scale of petrochemical production in our country, great economic and social benefits have been achieved, and the balance of the ecological environment has also brought great damage. The oil industry as well as the impact of the chemical industry's production on the ecological environment is more serious, so we must strictly treat this issue. We have taken a certain approach to the emission control of "three wastes" (waste water, waste gas and waste residue) and actively managed them and achieved some success. However, we have also neglected some other sources of pollution. For example, valve leakage is a source of pollution that we neglected. The leakage of valves is a typical one of these sources. Because of the huge amount of valves used, valves leaked from various causes not only have a serious impact on the environment, but also cause serious waste of raw materials and products, sometimes causing serious accidents. Therefore, it is necessary and important for us to pay attention to the leakage of valves in the process of chemical production. Below on the cause of the valve in the petrochemical equipment leak and the way to avoid and eliminate leaks make comments on the reasons for the current valve leaks and valve design selection analysis, in order to provide a favorable reference for people who value this issue, to promote Optimization Design of Valve in Industrial Design.
Key words: valve leakage; reason; design selection Introduction Valve leakage as an important factor affecting the environmental pollution in China's oil industry, the ecological environment protection, energy conservation and the safety of petrochemical industry development has a certain negative impact. In this regard, a clear grasp of the petrochemical industry, the valve of the common causes of leakage, and optimize the design, has become China's oil industry and related departments of thinking and research focus.
1, the reasons for the valve leakage Valve as the petrochemical industry production process indispensable control device, its main role is to: protect the various aspects of the project, the pipeline running stability and safety, to meet the various technical requirements of the foundation On the reasonable control of the pipeline to complete the production of products. The current causes of valve leakage mainly in the following aspects: First, by the valve design and manufacturing process technology, valve sealing often problems, leading to leakage or penetration of pipeline material, resulting in environmental pollution and economic losses. Second, valve design and manufacturing process, when there is unscientific material choice, the valve will be used in the process of structural deformation, corrosion or damage and other phenomena, resulting in valve leakage problems. Third, as the valve manufacturing more use of "casting" technology, so in the process of valve plastic casting, by the operator's own factors or external factors, it is easy to have the valve body "trachoma" problem, so the use of trachoma valve , It is easy for the liquid (gas) medium to leak (leakage) problem. To solve this problem, it can detect the acute sealing test by water pressure and replace the dominant valve in time to avoid the leakage problem. Fourth, the valve manufacturing process, the valve seal packing did not reach the seal, resulting in the packing seal media infiltration, resulting in pipeline media pollution. Fifth, in the valve transport, installation, management, process, if the valve sealing surface deformation and damage, the same will cause the valve flow of small infiltration (discharge) problems, triggering media leakage, pollute the surrounding environment. Sixth, the use of the valve, when the valve stem is not closed, the valve is blocked, the valve stuck and so on, the same media leakage problems will occur, the problem is often larger leakage of material flow, the environment destructive. In addition, when the medium, especially the liquid medium, is doped with solid impurities, it also forms a problem of medium instability leakage, thus polluting the environment, causing damage to the ecological environment, and causing economic losses and production safety problems in the petrochemical industry.
2 Optimization of valve design selection 2.1 Stem stuffing box seal valve stem manufacturing There are also packing filler production. Bellows and diaphragm is not required filler, compared with the use of the filler stem, this fillerless valve stem as long as not because of the use of a long time damage will not leak, but there are flaws, is the production of this Valve stems more difficult, costly, and as long as the damage occurred in the work, the leak will be very serious, so generally adopt this valve stem, will take a layer of packing just in case. The packing stem, though not as robust as the unfilled stem, is widely used because of its simple structure, simple production process and low cost. It consists of a stuffing box, stuffing box, stuffing pad and stuffing box. The stuffing box is placed in the body and the stuffing equipment is inside the stuffing box. The packing pad is placed under the stuffing box and supports the stuffing box. Filler is divided into two types: soft and forming filler. The basic materials of soft sealing filler are asbestos fiber, fluorine fiber and carbon fiber, etc .; forming packing with O-ring, v-shaped packing. Conventional soft packing seals rely on the axial pressure of the packing gland to seal to a certain radial contact stress (radial pressure) between the valve stem and packing, and the side walls of packing and stuffing box. Therefore, to reach the seal, gland axial force is necessary to be quite large, which formed between the filler and the stem friction torque increases, wear and tear added, so the soft seal packing wear fast, often tighten the packing gland bolts Or replace the filler to ensure better sealing effect. Molding filler system to rubber, plastic and other engineering plastics as raw material, the choice of molding or turning made of a variety of ring seals. In contrast, the molding packing compact structure, good sealing performance, complete varieties of standards, a wide range of applications, therefore, now more commonly used. Use the appropriate packing seal and packing seal combination, can improve the reliability of the valve to extend the service life of the valve, such as the combination of flexible graphite ring packing than simple flexible graphite ring packing sealing effect. At present, the situation of using pure flexible graphite ring packing in China is relatively more, and the use of flexible graphite ring packing combination abroad has begun to prevail and has achieved outstanding results.
2.2 valve body sealing parts connected to the local body closure is closed between the valve body and bonnet, all over the use of flange connection method, if the valve cross-sectional area is relatively small, the use of thread connection method. The seal between the valve body and the bonnet is statically closed and it is necessary to reach the following five points of specification: ① No matter the temperature or the pressure changes, it must be closed. ② frequently disassembled equipment will not be damaged. ③ simple structure, close, using less metal power. ④ will not be affected by the shock or impact load. ⑤ Regardless of the physical and chemical functions of the fluid, it will not be affected. The body of the convergence Most of the local use of tongue and groove, bump-type gaskets, in recent years, 0-sex gaskets have also been used throughout. Tenon-type flat gasket seal, the flat gasket device in the closed slot, this structure can occur in the sealing surface of the high seal pressure, generally far beyond the yield limit of the gasket data, and then to ensure reliable Sealing. It is suitable for medium and high pressure PN≥4.0MPa valve. The disadvantage of this seal structure is that when the valve is disassembled, the gasket is difficult to remove from the seal groove, and if it is removed rigidly, the gasket tends to be damaged. Bump style seal is the flat pad device in the concave shape of the flange, and tenon style seal compared to the concave and convex style seal has the following two advantages: ① removal of the valve process is very simple You can put the gasket out. ② closed groove is not smooth, so the processing skills is relatively simple and excellent. Flat pad material, in accordance with the technical parameters and the physical and chemical properties of the fluid to be selected, you can use aluminum, copper, chromium and rubber asbestos board. Fluoroplastics can also be used as a material for manufacturing flat mats, however, due to the cold flow properties of fluoroplastic itself, adding unreasonable closure planning can cause serious leaks. O-shaped gasket, the structure is simple, the production of lunch, the design is complete, the equipment can be formed after enough radial kneading deformation, you can not have to go through the axial auxiliary can show the perfect closure, so the seal Used in the flange connection structure, you can greatly reduce the size of the flange, the screw down the amount and size, in order to reduce the gravity of the valve itself.
Conclusion From the above, we can clearly see that the valve leakage in industrial production can not be ignored, which has a serious impact on the economy of production, safety and the environment. The key to eliminate the valve leakage is to optimize the valve structure design, according to different process conditions, the rational selection of valve manufacturing information, improve the quality of the valve during the production process to optimize the selection of the valve. In the chemical production process to effectively deal with the leakage of the valve can be largely satisfied with the requirements of safety and production, drastically reduce the economic losses caused by leakage, as well as effectively reduce the formation of chemical production process environment Pollution.

Machine Room-less Elevators

Mrl Passenger Elevator,Hospital Elevator,Bed Elevator

XIWEI Elevator Co., Ltd. , http://www.sqelevator.com