My week according to the needs of social development. Take me weeks to build "resource-saving and environment-friendly" society, the coal industry is facing historic challenges and opportunities, undergoing crucial changes. The realization of IT and mechatronics technology as the core of integrated automation; clean production and clean coal technology-based clean technology; to large enterprise groups and characterized by intensive diversification, that is efficient, safe, clean, structural optimization, has become the direction of the new era of China's coal industry development.

   Hydraulic support is high-pressure liquid powered, if supported by a ten hydraulic components (cylinders, valves) in combination with a number of components made of metal roof of the coal face and control equipment. High strength, moving fast, good supporting performance, safety and reliability features.

 According to Sony learned to hydraulic tools, supporting the coal mine is always an important issue troubled coal yield efficient and safe production. Thus, the birth and development of hydraulic support for the main equipment is mechanized coal mining history of the development of the production of a major revolution, not only to improve working and safety conditions for all. Also improve the efficiency of coal production and quickly laid the foundation for the coal production outlook completely changed.

A hydraulic support the development of domestic and international comparison

     1.1 Overview of the development of hydraulic support abroad
 
   In 1954 the UK for the first time developed a stack hydraulic support, followed by the development of the French section of hydraulic support bracket instead of wood and metal friction brackets, the technological revolution has opened up the coal face support equipment. The former Soviet Union 60 years to develop and improve the OMKT type shield bracket (with a four-bar linkage), to solve the problem of the change from the end of the stent, the stent opens up a new era of hydraulic design; 70s are the "immediate support" approach; 1980 Xi Dehe mother Shuttleworth has developed G550-22/60 cover bracket, the maximum height of 6m. To improve the deep production capacity, reduce production costs, the mid-1970s, the British Coal Board first proposed the development of electric hydraulic control. The first electric hydraulic control for longwall coal mine in Australia is Kelimaner the face by the 74 former British Road antimony company developed four-poster crib hydraulic frame composition, commissioned in 1981. By the end of 1983 the British original road antimony mine company has manufactured for the U.S. cancell two-button computer controlled hydraulic support, in 1984 production. By the end of 1995 the British original road antimony company has developed a full face centralized electro-hydraulic control system. Westphalian - Tony Reiter company developed the test more advanced P-M3 and P-M4 electro-hydraulic control system. Now the electro-hydraulic control system has been developed to the full mechanized mining equipment visualization integrated control stage.

   Since the 1980s, major mining countries in the world have been around less face lift capacity, reduce personnel and efficiency, reduce costs and to focus on the production and efforts to achieve mine. They actively develop and apply new technologies, is committed to developing high-performance, high reliability, a new generation of heavy-duty hydraulic support. The new hydraulic support generally have mini-motor or solenoid-driven electro-hydraulic control valve, equipped with a displacement sensor jack goes, Shearer equipped with infrared sensing devices, columns bore more than 400mm, cutting coal to reduce the time, generally use 0.8 ~ lm The cutting depth, but also with yield strength steel bracket 800 ~ 1000MPa, both high strength, hardness and toughness, but also has good cold welding performance. With the increasing length of the longwall face, to meet the needs of fast moving aircraft, widely used abroad, high pressure and large flow of emulsion pump, the rated pressure of 40 ~ 50MPa, the rated flow 400 ~ 500L/min, the work can be achieved surface into groups or rows of fast moving aircraft, reaching 6 ~ 8s / rack. 1.2 Development of domestic hydraulic support

Hydraulic support our development process can be divided into four stages

   (1) the initial stage of learning

   China from the early 1970s to start development work hydraulic support, basic conditions are very poor, everything from scratch, the required sheet, pipe and hydraulic pipe glue and so need to be developed and tested. 1964 from the Taiyuan Branch and Zhengzhou Coal Mining Machinery Factory Design Type 70 self-shifting move bracket, from the beginning of the road made hydraulic support. In the majority of the hard work of scientists, has developed a windrow, festival style and shield bracket. Although stent performance and reliability are poor, but for the development of hydraulic laid the foundation for the future development of hydraulic supports accumulated experience.
 
   (2) the introduction, digestion, absorption, development stage

   The late 1970s and early 1980s of three times on a large scale introduction of foreign support, especially in the third installment of the introduction of the more advanced Western countries was mechanized mining equipment total of 100 units, of which the main hydraulic support leg shield with two and four-poster Braced main parameters and performance stents have significantly improved than ever imported bracket. In 1984, Beijing mining, Shenyang, Zhengzhou Coal Mine Factory in Shenyang, China's first set Puhe caving hydraulic support industrial test, and then developed a variety of low, median and high caving support, success to gently inclined thick coal seams and steep inclined seam adopted for use in the face. Through digestion and absorption of foreign advanced technology, the researchers developed a variety of different uses hydraulic support, a representative of the stent has QY series and ZY series bracket, which QY31 and ZY35 stand in the larger context has been widely used. During this period developed stent ordinary lighter weight, such as the QY31 economic bracket weighs just 6T, stand working resistance also small, two column bracket generally 2000 ~ 3500kN, four-post rack is generally 3000 ~ 4600kN. Reliability stents are relatively poor, life test only 8000 times larger gap with foreign countries. In the control of the stent, the main operating valve to valve ZC chip-based, flow only 80L/min. Emulsion pump flow rate is generally 80 ~ 200L/min, stent slower moving frame, generally 20 ~ 30s / rack, column jack rubber seals are all short-lived.

    (3) improve and enhance the stage
 
   From the mid-1990s, China began to enter the hydraulic support a rapid development stage, the national number of fully mechanized coal face greatly improved the performance of hydraulic support, parameters, reliability has been significantly improved, rack-type continuously enriched. Especially in top coal caving technology in China's successful application, greatly promoted the rapid development of caving support. Rack-type positions divided by caving high, medium, low caving support, according to the direction of four with a positive four-link and reverse four-link caving stents. The past five years with the increasing domestic demand for high-end hydraulic support (2007 hydraulic support demand reached 25,000) and the development of hydraulic support localization process, the domestic high-speed development stage hydraulic support, Zhengzhou Coal Mining Machinery Factory has produced other manufacturers out of 5.5m, 6m high hydraulic support of 800MPa and 900MPa grade high strength steel welding were studied systems. Pingdingshan Coal Factory, Zhengzhou Coal Factory and Beijing Coal Factory and other hydraulic support electro-hydraulic control technology research, about to enter the pilot phase of industrialization. Design and manufacture of hydraulic support domestic level is gradually close to the international advanced level.

2 hydraulic support the development of the domestic situation

    (1) the current level of stent design

   According to Sony hydraulic tools noted that China currently has a design capacity of the hydraulic support units there are four, namely Beijing exploitation, Beijing Coal Factory, Zhengzhou Coal Mining Machinery and Shenyang Institute. Beijing mining in recent years accounted for about 50% of the national volume of hydraulic support design tasks, a higher proportion of new aircraft type that accounts for some of the designs. Beijing is mining the technical focal point hydraulic support, standard hydraulic support, design specifications are from the Institute. Beijing exploitation of the stent design level represents the domestic hydraulic support design standards, has achieved a hydraulic support design 3D CAD design and develop a simulation of hydraulic support systems and stand with the international advanced level parameters to optimize the design of software systems. Although the design level of the hydraulic support and abroad have a certain gap, but the gap is narrowing.

    (2) the use of the material status of the hydraulic support
 
   Previously used by the vast majority of domestic bracket plates are made of 16Mn steel 350MPa, and good welding performance, but low-intensity, stand heavier. In order to reduce the weight of the bracket, began to study domestic welding of high strength plate from the mid-1990s, after years of efforts, now below the rank of 1000MPa steel welding process were studied. The second is the column jack, 2004 Zhengzhou Coal Mining Machinery Manufacturing Φ360mm uprights Jincheng has been successfully applied in large mining height bracket. At present, China has several major stent manufacturers have the ability to produce in Φ400mm the column, two columns shield working resistance of support can reach l0000kN. (3) Our standard hydraulic test stand
 
    China is currently testing the use of hydraulic support MT312-2000 technology standard to replace the MT312-1992, the new standard in the development process not only referring to the European standards, but also a combination of hydraulic support at this stage in our usage. The new standards from August 2001 began to implement enforcement. New standards on the number of tests has greatly improved over the old standard, when the top beam partial load load torque four-bar linkage 70% increase than the old standard, in addition to the two-column bracket also increased the level of loading conditions. (4) status of the control system of hydraulic support
 
   At present, China has a control system for hydraulic supports two types, namely, manual control and electro-hydraulic controls, most of which is manually controlled system, only Shenhua, Jincheng mining area and a few imported stent using electric hydraulic control system. Traffic manual system is generally 200 ~ 400L/min, the fastest moving rack up 11s / rack. China from the mid-1990s began to develop electro-hydraulic control system, although a lot of work, but the results are not satisfactory, the impact of the valve and the stability problem is not resolved, it is not fully implemented in the promotion and application of downhole . In recent years our Tenma in cooperation with Germany, the introduction of Germany's Ma Ke PM3 technique has been successful in filling state, the application of the bracket Kailuan mine, and have achieved good results.
 
3 hydraulic support domestic and foreign gap
 
   Currently the gap between domestic hydraulic supports the world's advanced countries mainly in the overall reliability of the stent material structure, control several aspects of the system and hydraulic components.

   (1) reliability, the reliability gap with foreign countries most of the gap between our current stent is relatively large. For example Shenhua imports stand, face the operation rate of over 90%, with an annual output reaching 10MT, 15MT coal bracket overhaul cycle is over. However, there are mechanized mining face average operation rate of about 50%. Bracket overhaul cycle average production volume of about 4 ~ 5MT. But recently China has independently developed ZFS6800/18/35 annual coal caving support has reached 8MT.

   (2) control systems
 
    Some developed countries in the world stand control system has been widely used in electro-hydraulic control system, such as the U.S., Australia, Germany, has been widely used. Electro-hydraulic control system technology in these countries has been very mature, stent frame shift very fast, up to 8s / rack, you can keep up with the speed of 13m/min Shearer. China currently uses hydraulic support electro-hydraulic control system for a small number, the vast majority of the manual. At present, China has 17 sets of stent using electro-hydraulic control system, the vast majority of imported equipment, which the company Shenhua East 9 sets, Jincheng, 2 sets all the iron law of imported equipment, the Kailuan two days Mary set for domestic production company . Control systems in China and abroad, the larger the gap. China is currently the vast majority still use manual control hydraulic support, moving frame rate is generally 15 ~ 20s / rack, you can keep up with the speed of the shearer 6 ~ 7m / s of. Compared with manual control electro-hydraulic control, labor-intensive, low degree of automation, slow, poor support.

    (3) aspects of hydraulic components

     According to Sony to understand hydraulic tools, development speed of China's hydraulic components lags far behind the need for the development of hydraulic support. Reliability of hydraulic support depends on the reliability of hydraulic components, hydraulic support successful application in coal production, the technical performance of key hydraulic components are doing to meet the requirements. At present, many foreign countries with large flow valve, check valve, globe valve, setting load holding valves and liquid column rapid return valve, the structure of hydraulic components, geometry, material selection, heat treatment and surface treatment and other methods aspects of in-depth research and development, the development of a number of good sealing performance, high sensitivity, large fluid intake and exhaust capacity, strong impact load all types of hydraulic components, hydraulic support to adapt the work performance requirements. In China, the development of such hydraulic components lags behind and is still in use on a 1980s product, there is no universal hydraulic components, serialization, standardization.