Key words: cast steel valve welding valve forged steel valve stomatal stress seal

0 Introduction

The valve in the refrigeration system plays a vital role in the flexibility and reliability of the valve opening and closing, which directly affects the technical performance of the refrigeration system, and the anti-leakage performance of the valve affects the economy and safety of the refrigeration system.

According to a Jinan refrigeration equipment company's data, in 2014 the company's customers in six of the valve leak occurred, only to add freon's direct costs on more than 30 million, and due to freon leakage caused by damage and loss of goods is more Big.

In the 1980s, there were four more accidents in the refrigeration system of Ningbo, because of the stagnation of the valve spool, the losing, the breakage of the bonnet, the explosion caused by the broken flange [1].

June 2004, a chemical plant in Hubei due to ammonia valve gland rupture, filler dripping ammonia, causing a lot of liquid ammonia spray [2]. These leakage of ammonia, explosion accidents, to the refrigeration system personnel, equipment safety caused a significant impact.

State Administration of Quality Supervision, Inspection and Quarantine in the fourth quarter of 2014, 75 enterprises of the 78 batches of valve products, a total of 14 batches of substandard [3]. To ensure the reliability and safety of the refrigeration system, many refrigeration systems use imported valves, but the expensive price to the enterprise has brought a heavy burden. Relative to the refrigeration compressors and other core components and automatic control valves and other precision control components, the general manual valve is not too high technical threshold, as long as the technical improvements and strengthen production management, domestic valves can meet the requirements of refrigeration systems.

1. Valve Frequently Asked Questions and Improvement Measures

1.1 cast steel valve body trachoma, stomata

Cast steel valves are one of the main valves used in refrigeration systems. The main problem with casting valves is trachoma and stomata. Although the modern casting technology can be used in the charge of the gas before the use of vacuum pump out of the smelting process can also maintain a high degree of vacuum, but the casting solidification interval is narrow, strong thermal conductivity, making the solidification speed. The gas involved in the filling process will not be timely from the vent or gate discharge, and ultimately the formation of pores in the casting.

In 2014, Changqing Oilfield Technical Testing Center tested a total of 170,284 valves, of which the appearance of unqualified inspection 2817, mainly trachoma, stomata, cracks, mechanical damage, shrinkage, etc. [4].

Casting forging is the development trend of the valve industry [5]. East cold forging steel valve, is the use of 3000t forging press, through the forging to eliminate the metal cast as loose, welding holes, the mechanical properties far better than the same material castings. And eliminate the existence of castings trachoma, pores, shrinkage and other hidden dangers.

East cold forging steel has been the national patent, patent number: zl2014 3 0386552.1

                                Zl2014 3 0386550.2

                                Zl2014 3 0386548.5.

1.2 Welding valve residual stress

Compared with the casting valve, the welding valve stiffness is poor, after the pressure deformation of the impact of sealing performance, wear resistance is poor. In addition, improper improper handling during welding, there will be residual welding stress, will affect the performance of the valve work.

East cold forging steel valve, through the forging of metal materials to improve performance, rigidity, wear resistance, there is no residual stress.

1.3 stem leaks

Stem leakage is the most common problem in refrigeration systems, due to repeated switching, stem and packing between the friction, packing wear caused by leakage. Reduce the valve stem leakage In addition to selecting the sealing performance is excellent, good wear resistance of the filler, the filler processing accuracy, assembly compression is also the key to the valve design. East cold valve with flexible PTFE filler, sealing performance, self-lubricating, wear-resistant.

1.4 valve flap off

The traditional refrigeration valve, the valve flap with the stem at the bottom of the annular groove connected, long time use, the pin will be due to wear and tear, resulting in valve flap off. East cold valve valve and valve stem between the use of bearing connections to improve the connection strength and reduce the friction resistance, which can effectively prevent the valve flap and stem off, extending the life of the valve stem and valve.

1.5 disc seal off

At present, the valve door of the refrigeration valve is generally sealed with polytetrafluoroethylene. The Teflon sealing ring is embedded in the annular groove at the bottom of the valve flap. After prolonged application, the sealing ring will fall off. East cold valve in the lower part of the valve flap to add a screw ring, to ensure that the seal will not fall off.

East cold valve valve connection technology has been the national patent, patent number: zl200720022713.3.

1.6 stem icing

Refrigeration system in less than 0 ℃ working conditions of the valve, stem icing is inevitable. For valves that are always at low temperatures, the stem is free from ice, but for valves on hot air defrost pipes. In the normal cooling, the stem is frozen, hot air defrost, the ice melted. At this time, if the valve is closed, the valve will be infiltration of water. When the valve again low temperature work, the stem and the filler will be frozen between. When the filler is frozen, the switch valve will cause damage to the packing, which is the main reason for the leakage of the valve stem of the refrigeration system. Now the market supply of valves, mostly in accordance with the national standard "ammonia with cut-off valve and lift check valve" GB / T26478-2011 production, the design working temperature of not less than -30 ℃, and the stem exposed, is a weak insulation Link. East cold valve with long neck valve cover structure, can increase the thickness of the valve insulation, so that stem packing away from the valve body medium, in a relatively high temperature zone, reduce the ice and the resulting damage to the filler to reduce leakage.

1.7 Distribution valve group stress damage

Refrigeration engineering installation of the most difficult, most prone to leakage of the site is the distribution station. As the valve, the spacing is small, welding deformation can not be avoided. For the casting valve, because it is a flange valve, distribution station production, must first welding, after assembly. Due to the thermal deformation of the dispenser head in welding, the length of each branch valve assembly assembled by uniform length can not meet the length requirement after the head deformation. Assembly, only rely on the flange bolts for fastening, the results of the distribution station flange, weld cracks occurred when the accident occurred. The distribution station at the valve-intensive, if there is leakage, maintenance is very difficult. Fluid pipe welding valve due to the larger size, and sometimes can not meet the distribution station welding requirements.

   East cold forging steel valve for the welding valve, the valve body size is small, welding connection, by improving the distribution of the branch valve parts of the welding sequence, effectively alleviate the impact of welding deformation caused by the head.

1.8-30 ℃ below the evaporation temperature of the cooling valve hard to find

Food refrigeration and refrigeration industry is the most important application area of ​​refrigeration technology. The corruption of food is mainly caused by the biochemical reactions of microbial life activities and enzymes in food. Microbial propagation and the role of enzymes need to have the appropriate temperature conditions, the principle of refrigeration is in low temperature conditions, the loss of vitality of microorganisms, the role of the enzyme is inhibited. In order to extend the shelf life, improve storage quality, food refrigeration temperature has become increasingly low trend. China's early low temperature library temperature is generally -18 ℃, the corresponding cooling system evaporation temperature of -28 ℃. Therefore, the national standard "ammonia with cut-off valve and lift check valve" GB / T26478-2011 provides ductile iron valve and fluid pipe welding valve temperature is not less than -30 ℃. But now a lot of cold storage enterprises in the low temperature storage temperature reached -25 ℃ ~ -35 ℃, the cooling system corresponding to the evaporation temperature of -35 ~ -45 ℃, and the freezer evaporator temperature is often up to -45 ℃ ~ 55 ℃. At such a temperature, according to the current national standard production of the valve is clearly unable to meet the requirements. East cold valve with forging technology, its materials and technology can meet the requirements of the existing refrigeration system.

1.9 cast steel valve shrinkage flow resistance exists

Liquid alloy from the pouring temperature to the solidification cooling to room temperature in the process of size and size will have different degrees of reduction of the phenomenon, casting will produce many defects: shrinkage, cracks, deformation and other residual stress. Due to shrinkage, the valve flow resistance, increasing the energy consumption of the refrigeration system. East cold forging steel valve does not exist shrinkage, in the design, but also improve the opening height of the valve, increasing the flow of the valve section, making the refrigerant flow resistance smaller and more energy efficient.

1.10 Carbon dioxide refrigeration system No special valves

Due to the impact of CFCS on atmospheric ozone and atmospheric warming, the protection of the environment and the replacement of CFCs become a common concern worldwide. As a ring-type natural type of natural working fluid, CO2 re-attention, both at home and abroad have built a large number of success stories. However, compared with the traditional refrigeration system, the working pressure of carbon dioxide refrigeration system is higher, and its subcritical cycle pressure is about 4MPa. In accordance with the national standard "ammonia with cut-off valve and lift check valve" GB / T26478-2011 regulations, ductile iron valve and fluid pipe welding valve engineering pressure PN25. The original ammonia, fluoride refrigeration valve can not meet the requirements of carbon dioxide refrigeration system. East cold licensing refrigeration valve has been issued by the Shandong Provincial Bureau of Technical Supervision B1, B2 production license, can produce PN25, PN40, PN63 three levels of valve production license, to meet the needs of carbon dioxide and other refrigeration systems. Component combinations, the filter was the Shandong Provincial Bureau of Technical Supervision B-production license.

1.11 double valve head safety valve

With the gradual improvement of safety awareness, safety regulations are becoming more and more severe. Europe and the United States and other developed countries are using dual-valve refrigeration system safety valve, is expected in the near future will be enforced in China. Qingzhou City, Shandong Province, Oriental refrigeration equipment factory in the country's first R & D and production of a double valve head safety valve, access to the State Technical Supervision issued by the A2-level production license, can produce PN63 pressure level safety valve. To ensure that the refrigeration system more secure, more at ease.

 

2. Concluding remarks

In the refrigeration system, the valve plays a vital role. After twenty-six years of unremitting efforts, through the investigation and analysis of common problems of refrigeration valves, drawing on domestic and foreign well-known brands and high-pressure valve design ideas, the East cold valve in the material, technology, sealing, valve connection and fixed, pressure capacity And other aspects of the technological innovation. So that the product in the sealing performance, wear resistance, pressure level, reliability, etc. have been greatly improved for the safe and efficient operation of the refrigeration system to provide a reliable guarantee.

                                 

references:

[1] Kong Fancheng, four by the ammonia valve caused by major accidents and technical analysis. "Refrigeration Technology" 1990 the fourth period .22-23

[2] Sun file, with ammonia leakage accident analysis. "Labor Protection" 2005 the second period

【3】 State Administration of Quality Supervision, Inspection and Quarantine. The fourth quarter of 2014, the quality of the valve product quality supervision and inspection results. "Machinery Industry Standardization and Quality" 2015 No. 3 .51-52.

[4] Chen Fei, Cao Haiping, the valve appearance of common defects and assessment. Industrial Technical Supervision. 2015 (8) .11.

[5] Yu Xingjuan Chen Wenxun, etc. The status of the valve industry and the trend of casting and forging development analysis.

Forging and stamping .2015 (13) .47-49.

[6] Zhang Fuguan, Huang Yongshen. Valve common faults and maintenance strategies. "Science and Technology Innovation and Application" 2015 (23) .142

[7] Lu Yanbin Guo Rui. Structural optimization design of ultra-low temperature valve. "Science and Technology Innovation and Application" 2015 (10) .55-56.

[8] Xu Chenxia Xia Yuan. Valve seal structure design problems and countermeasures. "Scientific research" No. 9, 2015.148.

[9] Liu Xingyu Hu Jingyuan, etc. Valve packing material calculation method analysis. "Mechanical Research and Application" 2014 (5) .160-161.

[10] Liang Qiang. Low temperature valve bonnet neck temperature field analysis and structural design. "China Science and Technology Expo" 2014 (30) .389.