Application of Upstream Pumping Mechanical Seal on Liquefied Steam Pump
Hao Muming Petroleum University Department of Mechatronics Shandong Dongying City 257062 Su Yuzhu University of Petroleum Shenghua Refinery Dongying Shandong 257062 Zero escaping upstream pumping mechanical seals. The industrial application results show that the upstream pumping mechanical seal can realize the zero-escape of the volatile medium, and has the advantages of long service life, low operating cost, and safety and reliability.
Theoretical analysis shows that the upstream pumping mechanical seal can achieve zero or zero leakage of the sealing medium under the design conditions, and the experimental study also confirmed that the 2,3 upstream pumping mechanical seal ensures zero leakage of the sealing fluid in a non-contact state. There are reports of successful applications in the industry. 4. The John Crane Seal Company of the United States developed and developed the 8000 series of upstream pumping mechanical seal products, marking its entry into the industrial application and promotion stage.
Up to now, the upstream pumping mechanical seals are mainly used to replace the common contact type double-end mechanical seals, and the seals have a high risk and are not easily vaporized. In the petroleum and petrochemical industry, a large number of light hydrocarbon pump shaft seals have low vapor pressure due to the medium, which makes the seal in an unstable vapor-liquid two-phase working state, generates a large amount of vapor phase leakage, causes serious environmental pollution, and leads to early failure of the seal. Shadow production safety operations.
After a lot of experimental research, aiming at the existence of refinery liquefied gas pump shaft seals, we developed an upstream pumping mechanical seal that can achieve zero escaping of liquefied gas pumps, and developed an upstream pump suitable for shaft seals for easily vaporizable media pumps. Sending mechanical seals has accumulated experience.
1 The existence of ordinary seals The liquefied gas pump is a bottom pump of a refinery catalytic device. The population pressure is 09 when the medium is working, the outlet pressure is 1.5, the pressure is uniform, the degree of transport is 35, and the ambient temperature is 18. Rotating speed 2950min, rated flow 25mVh, mechanical diameter of the seal at the shaft diameter for the disc is built-in single-end large spring balanced structure sealing surface inner diameter of 52, outer diameter of the bracket 2, the width of the end face is 5, the balance diameter of the share. 5 painting, the balance coefficient is 0.234, the spring pressure is 0.25 Peng, 2 the use of the question exists in the delivery temperature is 35 when the liquefied steam vapor pressure is 0.36, lower than the outer diameter of the sealing surface of the liquefied gas pressure is about 1.2; And at ambient temperature 18, chaos, irritated, scraped, 0.205, at ambient atmospheric pressure. According to the vapor-liquid two-phase seal theory 5, the friction seal of the mechanical seal of the liquefied gas pump is in the vapor-liquid mixed phase lubrication state, that is, the phase change occurs between the sealed end faces except for the inner liquid film, the liquid phase near the outer diameter side and the vapor near the inner diameter side. Phase, its working state is extremely unstable, it is easy to cause the sealing face to open and cause the liquefied gas to vent or escape to the atmosphere side in the form of vapor. At the same time, the seal friction pair will undergo dry operation, serious wear and even hot cracking, leading to seal failure. Have to change seals frequently.
In order to improve the sealing working environment, reduce the friction temperature rise of the end face and prolong its service life, some supplementary measures have been taken for the original contact type mechanical seal, including 1 taking self-rinsing measures.
The injection hole on the gland 9 is directly injected into the seal friction pair in the seal box 4 to form a cycle under the effect of pressure difference, and the friction pair produces a good friction state. The on-site measurement of the liquefied gas self-cleaning volume is approximately 5 China Petroleum and Natural Gas Corporation technological development project 1 sleeve, 2 spring sleeves, 3 spring yellow, 4 sealed boxes, 5 ring seals, 6 rings, 7 static ring seals Ring, 8 static ring, 9 pressure cover 2 uses static ring back-cooling measures, at the same time, through the pressure of the lid to inject the cooling water into the hole to indirectly cool the back of the static ring, it can also reduce the temperature rise of the end face to a certain extent, improve work surroundings. Cooling water flow is 231.
After adopting the above measures, the working environment of the mechanical seal has been greatly improved, the life cycle has been prolonged, and the sudden accidents of seal failure have been correspondingly reduced. However, due to the working principle of the contact type mechanical seal, the contact pressure between the end surfaces is used to achieve the sealing. Under the influence of the internal and external pressure difference, the medium must pass through the small gap between the two rough surfaces to generate a leak. For the liquefied gas, , it is in the form of vapor phase to escape to the outside, that is, no liquid leakage is observed. After several weeks of work, it was found through concentration instrumentation that the concentration of liquefied gas in the room was significantly increased. After two months of accumulated operation, the liquefied gas concentration had been severely exceeded, and the pump had to be replaced and sealed.
Moreover, after the flushing and cooling measures are adopted, the wiper pair is still in the vapor-liquid mixed-phase frictional state, and the direct friction and wear between the end surfaces is more serious. Therefore, the extension of the seal life is also limited.
From the above analysis, it can be known that ordinary contact-type mechanical seals cannot eliminate leakages or escapes to the atmosphere, such as liquefied gas and other easily vaporizable petrochemical process media, due to the limitations of the self-sealing principle, resulting in environmental pollution. Of course, the double-end seal or the series seal can be used to substantially eliminate the leakage, but the seal assist system is complicated and the operating cost is greatly increased, and the reliability of the auxiliary system directly affects the use effect of the seal.
Upstream pumping mechanical seals are based on fluid dynamic pressure lubrication theory and even zero escape to meet the stringent requirements of modern environmental protection, and because there is no direct solid friction and wear between the seal friction secondary end face, its working life is greatly extended, friction The low surface temperature rise of the power consumption is limited, which can greatly reduce the flushing cooling amount of the seal, or even completely eliminate the flushing cooling measures, so that the operating cost is greatly reduced, and the working efficiency of the pump is correspondingly improved. Therefore, the upstream pumping mechanical seal has a new type of mechanical sealing technology integrating environmental protection, energy saving and long life, and will surely have an extremely wide industrial application prospect.
2 Upstream pumping mechanical seal design Upstream pumping mechanical seal Zero leakage Upstream enthalpy mechanical seal and zero escape Upstream pumping mechanical seal Two types of zero leakage Upstream pumping mechanical seal No additional buffer auxiliary system is required, mainly used To seal similar non-flash hydrocarbons such as various normal-temperature oils and other difficult-to-vaporize media; and zero-escape upstream pumping mechanical seals require a buffer auxiliary system, suitable for sealing vaporous hydrocarbons such as flash vaporous media For example, ethylene-catalyzed liquid hydrocarbon liquefaction of vapour-liquid ammonia can completely eliminate media emissions to the outside world in any form. At the same time, it allows trace amounts of buffer to pump people's seal media without affecting process production and product quality.
Based on the characteristics of liquefied gas and the use of existing seals, a buffered liquid lubricated with zero is designed to escape the upstream chestnut delivery mechanical seal on a large number of experimental studies. Taking into account the process requirements, the buffer is filtered tap water, the pressure is 0.150, the filtration accuracy is 5, and eliminate the self-flushing measures. The buffer is sent upstream through the injection hole on the secondary sealing box 9 and the mechanical seal is mainly composed of the moving ring 6 and the stationary ring 8 and the water seal. The trace buffer can flow through the water seal 10 to the outside.
1 bushing, 2 spring bushings, 3 springs, 4 sealing boxes, 5 moving ring seals, 6 moving rings, 7 static ring seals, 8 static rings, 9 sealing boxes, water seals, gland structure, moving ring Inlay evaluation, warehouse magistrate jurisdiction, not lung, x06 Min graphite.
The end of the seal ring is an internal grooved spiral groove upstream pumping structure. 4. The relevant structural parameters of the seal ring are the seal groove inner diameter is 0, the relevant structural parameters are spiral groove inner diameter = 48, and the outer diameter is 0!
Lubrication and sealing of 1.56 ships, the maximum pumping volume of the buffer is 1 This application effect The liquefied gas pump was replaced at the beginning of September 1999 with the developed upstream pumping seal structure, and the sub-successful operation was successful until the end of April 2000. Stopping due to the expansion of the catalytic device, during which the pump has been running for nearly 5 months, and the seal is tested periodically every week. The sealed liquefied gas escaped volume has not been measured to exceed the standard, and the moving ring is not obvious after disassembly and sealing. Wear 5, measured static ring wear is less than 0.02 In addition, the buffer cooling water consumption is less than 0. Mainly leaked through the water seal to the outside world.
Adopting the upstream pumping mechanical seal not only basically eliminates the vapor phase escape of the liquefied gas pump, but also increases the benefit by 130,000 yuan in the same device operating energy consumption due to the elimination of the self-fluiding fluid circulation amount of nearly 1300 within 5 months. Calculated with a profit of 100 yuan, the cooling water is saved by nearly 60, and the amount of sewage treatment is reduced accordingly. It can be seen that the economic benefits generated by using an upstream pumping mechanical seal on a liquefied gas pump are considerable.
4 Conclusions Ordinary contact-type mechanical seals are difficult to achieve zero-emission of easily vaporizable media such as liquefied gas, and have a short service life and high operating costs.
The use of an upstream spliced ​​mechanical seal on a liquefied gas pump not only allows zero leakage or zero escape of the sealing medium, but also greatly prolongs the use cycle, and can significantly reduce the operating costs and increase the production efficiency of the device. If the upstream pumping mechanical seal can be used and promoted in various processes and pumps of the petroleum and petrochemical industry, the economic and social benefits will be enormous.
Hao Muming, Hu Danmei, Yang Huiying. Research and Development of Upstream Pumping Mechanical Seals, Fluid Machinery, 20012931 MENG Jian, HAO Muming, HU Danmei, Research on Sealing Performance of Reverse Flow Pumping Mechanical, Flow Gu Yongquan, Phase Analysis of Pump Mechanical Seal and Analysis of Phase Stability Proceedings of the International Fluid Seal Conference, 1992.
Soft metal critical shear stress 9.8xIQ8Pa melting point crystalline gold, face-centered cubic silver face-centered cubic, lead 41 face-centered cubic dense cubic tin-16, body-centered side-centered cubic solid lubricant combination for the manufacture of composite friction reducing materials In practice, a large number of various combinations of additives are often added to improve the friction reduction performance. For example, graphite is often used together, sometimes with 8 additions to iron, copper, aluminum, nickel or other alloys; in aluminum-based alloys, or with 0.5, 50, and in combination with solid lubricants, the use of solid lubricants can make better use of the various groups. Yuan's performance characteristics, complement each other.
3 Conclusion The use of light, corrosion-resistant and thermally conductive aluminum as a friction-reducing material matrix will obviously become active. Since the tenth decade, many industrially developed countries, especially Japan and the United States, have been actively developing and developing. Aluminum-based solid self-lubricating anti-friction material is manufactured by powder metallurgy method, which has a wide application prospect Fedorchinko, powder metallurgy composite anti-friction material, Beijing Institute of Powder Metallurgy, Beijing, 1985.
Nishimura Yun, Introduction to Solid Lubrication 5 Solid Lubrication, 1987, 73> 177182, Zeng Delin, ed., Powder Metallurgy Materials, Beijing Metallurgical Industry Press, 1988.
Deng Zhiqian et al., Metal Materials and Heat Treatment, Changsha Zhongnan University of Technology Press
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