煤矿科技英语.doc

煤矿科技英语8. COAL CUTTING MACHINES SHEARER2006年8月1日 10:5:08-1 Major Components of Shearers 1Although there are many models, the shearer has several common basic components. A double-ended ranging-drum shearer 2, for example, consists of four major components: electric motors3, gearheads 4, haulage unit（power pack）5, and cutting drums 6.The electric motor ranging from 300 to 1000 horsepower（223750kw） is the power source for the shearer. It provides to run the hydraulic pumps 7 in the haulage and the gearheads for cutting drum. The large capacity shearers are generally equipped with two electric motors: one for the haulage unit and one gearhead and the other for the other gearhead and other ancillary equipment 8. The motor can be remotely controlled.There are two gearheads, one on the left-hand side and the other on the right- of the shearer. Each gearhead consists of a gearhead gearbox 9 and a ranging arm.The cutting drum is laced with spiral vanes 10 on which the cutting bits are mounted. It diameter ranges from 0.861.83m with rotational speeds 11 from30 to 195 rpm. The drums are also equipped with power cowls 12 to increase the coal loading efficiency. The power cowl is usually located behind the cutting drum. For that reason, it can be rotated a full 180.The electric motor, haulage unit, and gearhead boxes combine to form the shearers body, which is mounted on the underframe 13. The underframe has four sliding shoes 14. The face-side shoes are fitted and ride on the face-side top guide of the face conveyor pan 15, and the other two gob-side sliding shoes are fitted on a guide tube to prevent derailment. The haulage speed of the shearer ranges from 5.814.0 m/min.In addition, the shearer is equipped with auxiliary hydraulic pumps and control valves 16 for operating the ranging arms and power cowls, water spraying devices 17, cable 18, chain anchorage 19 and tensioners 20, and so on.8-2 Types of Modern ShearersSingle-ended fixed-drum shearer 21is an earlier model. A single drum is mounted on the shearers body and cannot be adjusted for height. Therefore, it is not suitable for areas where there are constant changes in seam thickness and floor undulation 22. Thus the single-ended fixed-drum shearer is used mostly for thin seams.This is a single-ended ranging-drum shearer 23. The cutting drum is mounted at the end of the ranging arm . The ranging arm can be raised up and lowered down by hydraulic control to accommodate the changing seam thickness and floor undulation. But when the seam exceeds a certain thickness, the single drum shearer cannot cut the entire height in one cut, and a return cutting trip 24 is necessary to complete a full web cut 25. Furthermore, since the drum is located on the headentry 26 side, it generally requires a niche in the tailentry 27 side. A niche 28 is a precut face end, one web deep and a shearers length long. With a niche at the face end the shearer can turn around.Nowadays, the double ranging-drum shearer is used predominantly. The shearer cuts the whole seam height in one trip. The two drums can be positioned to any required height（within the designed range）during cutting and lowered well below the floor level. The arrangement of the drums enables the whole seam to be cut in either direction of travel, thereby ensuring rapid face advance and shortening roof exposure time. There are various types of double ranging-drum shearers. Based on the location of the drums, there are two types: one with one drum mounted on each side of the shearers body and the other with both drums mounted on one side of the machine. The former type is the most widely used. Its advantage is that the shearer with one drum on each side can sump 29 in either direction. During the cutting trip, the leading drum cuts the upper 70% of the seam height while the rear drum cuts the lower 30% and cleans up the broken coal on the floor. The two drums are approximately 710m apart. When the shearer is traveling in the opposite direction to that of the face conveyor , the coal cut by the leading drum has to pass under the shearers body, which increases the moving resistance 30 of the shearer and the face conveyor and could cause a “crowding” 31 condition. If the broken coal is too large, it may block the shearer and stop the production. In general, when the shearer and face conveyor are traveling in the opposite directions, approximately 70% of coal taken by the leading drum will pass under the shearer. But when they are traveling in the same direction, the coal taken down by the rear drum together with the float coal from the floor constitutes approximately 30% of the coal that has to pass under the shearer. The former case consumes 25% more power than latter. As compared to the single-ended shearer, the underframe of the double-ended shearer is higher, thereby ensuring a sufficient cross section for coal passage.Based on the method of adjusting the height of the cutting drum, there are also two types of shearers: ranging-arm shearer and gearhead shearer 32. The former one is commonly used, whereas the latter one is a recent development. The advantage of the gearhead shearer is that the haulage unit is located at the center of the shearers body and amounted on the underframe. On both sides of the haulage unit, there is a gearhead. Each gearhead contains an electric motor and speed-reduction unit 33. The gearhead is raised and lowered by an adjustable hydraulic ram. The adjustable range of cutting height is large. It can reach up to 1.4m.Based on the mounting relation between the shearer and the face conveyor, there are also two types of shearers: the regular type which rides on the conveyor and in-web shearer 34 which moves on the floor in front of the conveyor. The in-web shearer is used mainly for the thin seams. As it moves along the face, the leading drum cuts the coal, making a sufficient space for the passage of the shearers body.8-3 Haulage of ShearersThere are different types of shearer haulage: chain haulage 35 and chainless haulage 36, hydraulic haulage and electric haulage 37.A. Chain Haulage The haulage chain is a round-link chain 38, which extends along the whole face width and fixed on both ends at the head and tail drives 39 of the face chain conveyor, respectively. The chain also passes through the driving and deflecting（or guiding）sprockets 40 in the haulage unit of the shearer. As the driving sprocket rotates, its teeth 41 trap 42 to the matching chain links and move along the nonmoving haulage chain, thereby pulling the shearer along the face. When the driving sprocket rotates counterclockwise 43, the shearer moves to one direction. Conversely, when the sprocket rotates clockwise 44, the shearer moves to the opposite direction. That part of the chain in front of the moving shearer is generally tight or on tensioned side 45 whereas the other side, behind the moving shearer, is slack or on the slack side 46.There are many problems with chain haulage:When the shearer travels, the haulage chain is subjected to a large tension, due to the haulage force, and deforms elastically 47. Thus the tensioned chain contains considerable elastic energy. When the shearer stops or once the chain breaks, the elastic energy will be released suddenly, causing accidents 48.The haulage chain is suspended along the whole face width. If the faceline is not straight and the floor uneven, the chain may suddenly jump 49, injuring the crew. Under the combined effects of the elastic rebound of the haulage chain and haulage resistance of the shearer, the haulage velocity of the shearer oscillates 50 and frequently produces sudden impacts 51. This is damaging to many components of the shearer. The existence of the haulage chain is inconvenient for crew travel and accident handling. This is especially true for thin seams 52. As the power capacity of the shearer increases, the haulage force increases correspondingly. Therefore, the chain must be strong and the chain size must be increased. The heavy chain is inconvenient for transportation and maintenance.B. Chainless Haulage In response to all the disadvantages associated with chain haulage, the chainless haulage was developed. According to the haulage principles, the chainless haulage can be divided into three types: drive chain-rackatrack 53, drive wheel-rackatrack 54, and ram propulsion 55.This is the double-ended ranging-drum shearer with a wheel-rackatrack haulage system. The system eliminates any types of drive chain. The shearer moves by driving sprocket matched with the rackatrack through an idler 56. The haulage-driving unit is similar to the conventional ones. The driving sprocket matches an idler sprocket, which in turn rides on the rail track 57 made of steel peg rods 58. Thus, the driving system of power transmission is highly efficient. The rack is made of sections that have the same length as the conveyor pan, but they are installed in such a way that the center of each section is directly above the connection line between two adjacent pans.C. Electric Haulage Shearer Electric haulage shearers have successfully extended. Each element of the electric haulage shearer, including chainless haulage unit, two gearheads, auxiliary power pack, haulage and auxiliary control, is driven by its own electric motor with control equipment housed in a central unit 59.The advantages of the electric haulage shearer shearer are as follows: Easy maintenance: Units are readily accessible for removal from the waste side 60 without splitting 61 the machine, and are designed for easy maintenance and repair.Simplified transmission 62: Simplify and direct gearing to the cutting drums and haulage drive wheels.No structural requirement: Units are self-contained 63 within the shearers mainframe and are not subject to any external forces. The MG series AC frequency converted electric haulage 64 shearer was the first development in China. The technical performance and the reliability 65 of the product reached to a leading level in China and have been widely applied in the coal industry. At present, the product has been become a series product. The power of the product is ranging from 344 - 1020 kW and is suitable to a seam thickness ranging from 1000 mm to 4629 mm. The main features of the product are as followings: A special flame proof AC frequency converted speed adjusted device 33 was developed with a wide speed adjustment, a high haulage force and less fault; The product was driven with multi electric motors 66 and a flexible shaft was used to protect the cutting motor and the driven system; A PLC control technology 67 was used to develop a Chinese words interface between man and machine, a operation status monitoring and control, monitoring and measuring, fault memory and display technology68; A frame structure was used for the product in order to have a easy disassembling and maintenance 69; Hydraulic nut fastener 70 was used for a reliable connection.8-4 Characteristics of Modern ShearersA. The shearer should be designed to cut at low drum speeds with no breakdowns 71 and a minimum of maintenance. Attention should be given to visibility to enable the operator to control and manipulate the machine with ease. B. There should be an emphasis on robustness 72 and simplicity in the design and an absolute minimum usage of hydraulics. C. Effective dust suppression 73 has been provided by a water supply through the drum shaft known as “Pick Face Flushing” 74. In addition, a hollow shaft ventilation system 75 has also been provided to dilute the built up methane gas.D. The machine controls and health monitoring systems 76, such as natural gamma radiation sensor 77 to measure roof coal thickness and to position automatically the cutting drum, and the devices for remote control of machine functions have been used. The radio control has also been used. E. It is anticipated that shearers will require up to 1200 hp, 4160 volts motors and weigh up to 50 tonnes. The power of the machines increase with the increase demand for slower shearer drum speeds to reduce dust production. Drum speeds of 33 revs per min. have been used successfully. The optimum is a compromise between the speed of drum required to maintain a cutting advance of up to 0.11m/s and the need to minimize dust. NOTES TO THE TEXT1 Major components of the shearer：采煤机的主要部件2 double-ended ranging-drum shearer：双端可调高滚筒采煤机 3 electric motor：电动机 4 gearhead：传动机头（输送机等） 5 haulage unit：牵引部 6 cutting drum：截割滚筒 7 hydraulic pump：液压泵 8 ancillary equipment：辅助设备 9 gearhead gearbox：传动机头齿轮箱 10 spiral vane：螺旋叶片 11 rotational speed：旋转速度 12 power cowl：带动力的挡煤板 13 underframe：底托架 14 sliding shoes：滑靴15 conveyor pan：输送机溜槽 16 control valves：控制阀 17 water spraying devices：喷雾装置 18 cable：电缆 19 chain anchorage：牵引链锚固装置（采煤机） 20 tensioner：拉紧装置 21 single-ended fixed-drum shearer：单端固定滚筒采煤机 22 floor undulation：底板起伏2