0.9Mta副立井提升機(jī)選型設(shè)計(jì)含7張CAD圖,mta,立井,提升,晉升,選型,設(shè)計(jì),cad 外文資料 Mine hoisting in deep shafts in the 1st half of 21st Century Alfred Carbogno 1 Key words: deep shaft, mine hosting, Blair winder, rope safety factor, drum sizing, skip factor Introduction The mineral deposits are exploited on deeper and deeper levels. In connection with this, definitions like “deep level” and “deep shaft” became more and more popular. These definitions concern the depth where special rules regarding an excavation driving, exploitation, rock pressure control, lining construction, ventilation, underground and vertical transport, work organization and economics apply. It has pointed out that the “deep level” is a very relative definition and should be used only with a reference to particular hydro-geological, mining and technical conditions in a mine or coal-field. It should be also strictly defined what area of “deep level” or “deep shaft” definitions are considered. It can be for example: - mining geo-engineering, - technology of excavation driving, - ventilation (temperature). It is obvious that the “deep level” defined from one point of view, not necessarily means a “deep level” in another area. According to [5] as a deep mine we can treat each mine if: - the depth is higher than 2300 m or - mineral deposit temperature is higher than 38 oC. It is well known that the most of deep mines are in South Africa. Usually, they are gold or diamonds mines. Economic deposits of gold-bearing ore are known to exist at depths up to 5000 m in a number of South Africa regions. However, due to the depth and structure of the reef in some areas, previous methods of reaching deeper reefs using sub-vertical shaft systems would not be economically viable. Thus, the local mining industry is actively investigating new techniques for a single-lift shaft up to 3500 m deep in the near future and probably around 5000 m afterwards. When compared with the maximum length of wind currently in operation of 2500 m, it is apparent that some significant innovations will be required. The most important matter in the deep mine is the vertical transport and the mine hoisting used in the shaft. From the literature [1-12] results that B.M.R. (Blair Multi-Rope) hoist is preferred to be used in deep mines in South Africa. From the economic point of view, the most important factors are: - construction and parameters of winding ropes (safety factor, mainly), - mine hoisting drums capacity, This article of informative character presents shortly above-mentioned problems based on the literature data [1-12]. Especially, the paper written by M.E. Greenway is very interesting [3]. From two transport systems used in the deep shaft, sub-vertical and the single-lift shaft systems, the second one is currently preferred. (Fig.1.) [6] Hoisting Installation The friction hoist (up to 2100 m), single drum and the double drum (classic and Blair type double drum) hoist are used in deep shafts in South Africa. Drum winders Drum winders are most widely used in South Africa and probably in the world. Three types of winders fall into this category - Single drum winders, - Double drum winders, - Blair multi-rope winders (BMR). Double drum winders Two drums are used on a single shaft, with the ropes coiled in opposite directions with the conveyances balancing each other. One or both drums are clutched to the shaft enabling the relative shaft position of the conveyances to be changed and permitting the balanced hoisting from multiple levels The Blair Multi-Rope System (BMR) In 1957 Robert Blair introduced a system whereby the advantage of the drum winder could be extended to two or more ropes. The two-rope system developed incorporated a two-compartment drum with a rope per compartment and two ropes attached to a single conveyance. He also developed a rope tension-compensating pulley to be attached to the conveyance. The Department of Mines allowed the statutory factor of safety for hoisting minerals to be 4,275 instead of 4,5 provided the capacity factor in either rope did not fall below the statutory factor of 9. This necessitated the use of some form of compensation to ensure an equitable distribution of load between the two ropes. Because the pulley compensation is limited, Blair also developed a device to detect the miscalling on the drum, as this could cause the ropes to move at different speeds and so affect their load sharing capability. Fig.2 shows the depth payload characteristics of double drum, BMR and Koepe winders. The B.M.R. hoist is used almost exclusively in South Africa, probably because they were invented there, particularly for the deep shaft use. There is one installation in England. Because of this hoist's physical characteristics, and South African mining rules favouring it in one respect, they are used mostly for the deep shaft mineral hoisting. The drum diameters are smaller than that of an equivalent conventional hoist, so one advantage is that they are more easily taken underground for sub-shaft installations. A Blair hoist is essentially a conventional hoist with wider drums, each drum having a centre flange that enables it to coil two ropes attached to a skip via two headsheaves. The skip connection has a balance wheel, similar to a large multi-groove V-belt sheave, to allow moderate rope length changes during winding. The sheaves can raise or lower to equalize rope tensions. The Blair hoist's physical advantage is that the drum diameter can be smaller than usual and, with two ropes to handle the load, each rope can be much smaller. The government mining regulations permit a 5 % lower safety factor at the sheave for mineral hoisting with Blair hoists. This came about from a demonstration by the% permits the Blair hoists to go a little deeper than the other do. On the other hand, the mining regulations require a detaching hook above the cage for man hoisting. The balance wheel does not suit detaching hooks, so a rope-cutting device was invented to cut the ropes off for a severe overwind. This was tested successfully but the Blair is not used for man winding on a regular basis. The gearless B.M.R. hoist at East Dreifontein looks similar to an in-line hoist except that the drums are joined mechanically and they are a little out of line with each other. This is because each drum directly faces its own sheaves for the best fleet angle. The two hoist motors are fed via thyristor rectifier/inverter units from a common 6.6-KV busbar. The motors are thus coupled electrically so that the skips in the shaft run in balance, similar to a conventional double-drum hoist. Each motor alternates its action as a DC generator or DC motor, either feeding in or taking out energy from the system. The gearless Blair can be recognized by the offset drums and the four brake units. A second brake is always a requirement, each drum must have two brakes, because the two drums have no mechanical connection to each other. Most recent large B.M.R. hoists are 4.27 or 4.57 m in diameter, with 44.5 ÷ 47.6 mm ropes [1]. In arriving at a drum size the following parameters have been used: - The rope to be coiled in four layers, - The rope tread pressure at the maximum static tension to be less than 3,2 MPa, - The drum to rope diameter ratio (D/d) to be greater than 127 to allow for a rope speed of 20 m/s. With the above and a need to limit the axial length of the drums, a rope compartment of 8,5 m diameter by 2,8 m wide, was chosen. The use of 5 layers of coiled rope could reduce the rope compartment width to 2,15 m but this option has been discarded at this stage because of possible detrimental effects on the rope life. One problem often associated with twin rope drum hoists is the rope fleeting angle. The axial length of the twin rope compartment drums requires wide centres for the headgear sheaves and conveyances in the shaft. To limit the diameter of the shaft, the arrangement illustrated in Fig. 4 has been developed and used on a hoist still to be installed. Here, an universal coupling or Hooke’s Joint has been placed between the two drums to allow the drums to be inclined towards the shaft center and so alleviate rope fleeting angle problem, even with sheave wheels at closer centres [11]. The rope safety factor The graphs in Fig. 5 illustrate the endload advantage with reducing static rope safety factors. While serving their purpose very well over the years, the static safety factor itself must now be questioned. Static safety factors, while specifically relating to the static load in the rope were in fact established to take account of: a. Dynamic rope loads applied during the normal winding cycle, particularly during loading, pull-away, acceleration, retardation and stopping, b. Dynamic rope loads during emergency braking, c. Rope deterioration in service particularly where this is of an unexpected or unforeseen nature. If peak loads on the rope can be reduced so that the peak remains equal to or less than that experienced by the rope when using current hoisting practices with normal static rope safety factor, the use of a reduced static rope safety factor can be justified. The true rope safety factor is not reduced at all. This is particularly of importance during emergency braking which normally imposes the highest dynamic load on the rope. Generally, the dynamic loads imposed during the skip loading, cyclic speed changes and tipping will be lower than for emergency braking but their reduction will of course improve the rope life at the reduced static rope safety factor. The means, justification and safeguards associated with a reduced static safety factor are discussed in [4,7,9,12]. Based on the static rope safety factor of 4, the rope endload of 12843 kg per rope can be achieved. With twin ropes, this amounts to an endload of 25686 kg. With a conveyance based on 40 % of payload of 18347 kg with a conveyance of 7339 kg. There are hoisting ropes of steel wires strength up to Rm = 2300 MPa (Rm up to 2600 MPa [6] is foreseen) used in deep shafts. There are also uniform strength hoisting ropes projected [2,8]. Conveyances The winding machines made from a light alloy are used in hoisting installations in deep shafts. The skip factor (S) has been defined as the ratio of empty mass of the skip (including ancillary equipment such as rope attachments, guide rollers, etc) to the payload mass. If the rope end load is kept constant, a lower skip factor implies a larger payload – in other words, a more efficient skip from a functional point of view. However, the higher the payload for the same rope end load, the larger the out-of-balance load –implying a more winder power going hand in hand with the higher hoisting capacity. If, on the other hand, the payload is fixed, a lower skip factor implies a lower end load and a smaller rope-breaking load requirement. Under these conditions, an out-of-balance load attributable to the payload would remain the same, but that due to the rope would reduce slightly. The sensitivity of depth of wind and hoisting capacity to skip the factor is illustrated in Fig. 6 and 7. A reduction of skip factor from 0,5 to 0,4 results in a depth gain of about 40 m for Blair winders and 50 m for single-rope winders. The increase of hoisting capacity for a reduction of skip factor by about 0,1 is about 10 %. Typical values for the “skip factor” are about 0,6 for skips and about 0,75 for cages for men and material hoisting. Reducing skip factors to say about 0,5 is a tough design brief and the trade-offs between lightweight skips and maintainability and reliability soon become evident in service. The weight can be readily reduced by omitting (or reducing in thickness) skip liner plates but this could reduce skip life by wear of structural plate leading to the high maintenance cost or more frequent maintenance to replace thinner liner plates. Similarly, if the structural mass is saved by reducing section sizes or changing the material from steel to aluminium for example, the structural reliability is generally reduced and the fatigue cracking becomes more efficient. Some success has been achieved in operating large capacity all – aluminium skips with low skip factors but the capital cost is high and a very real hoisting capacity constrain must exist before the additional cost is warranted. It would appear that the depth and hoisting capacity improvements are better made by reducing the rope factor of safety and increasing the winding speed. The philosophy of the skip design should be to provide robust skips with reasonable skip factors in the range of 0,5 to 0,6 that can be hoisted safely and reliably at high speeds and that are tolerant to the shaft guide misalignment. Conclusions The first installation of Blaire hoists took place in 1958. From that time we can observe a continuous development of this double-rope, double-drum hoists. Currently, they are used up to the depth of 3 150 m (man/material hoist at the Moab Khotsong Mine, to hoist 13 500 kg in a single lift, at 19,2 m/sec, using 2 x 7400 kW AC cyclo-convertor fed induction motors). The Blair Multi-Rope system can be use either during shaft sinking or during exploitation. The depth range for them is 715 to 3150 m and the maximum skip load is 20 tons. In South Africa in deep shafts single lift systems are preferred. Welding is essential to the expansion and productivity of our industries. Welding has been become one of the principal means of fabricating and repairing metal products. It is almost impossible to name an industry, large or small, that does not employ is type of welding. Industry has found that welding is an efficient, dependable, and economical means of: joining metal inprtactically all metal fabricating operations and in most construction. In tooling-up for a new model automobile, a manufacturer may spend upward of a million dolla on we~ing e~pmenti Many buildings; bridgesi and ships are fabricated by welding. Where construction noise must be kept at a minimum, such as in the building of hospital additions, the value of welding as the chief means of joining steel sections is particularly significant. Without welding, the aircraft industries would never be able to meet the enormous demands for planes, rockets, and: missiles; Rapid progress in the space been made possible by new methods and knowledge of welding metallurgy. Probably the most sizable contribution welding has made to society is the manufacture ofspecial products for household use. Welding processes are employed in the construction of suchitems as television sets, refrigerators, kitchen cabinets, dishwashers, and other similar products. As a means of fabrication Welding has proved fast, dependable, and flexible It lowers production costs by simplifying design and eliminates costly patterns and machining operations. Welding is used extensively for the manufacture and repair of farm equipment, mining and oil machinery, machine tools jigs and fixtures, and in the construction of boilers, furnaces, and railway cars. With improved techniques for adding new metal to worn parts, welding has also resulted in economy for highly competitive industries. Types of Welding Processes Of the many processes of welding in use today, oxy-fuel gas welding, arc, and resistance dominate the field. These processes are best explained from the standpoint of the operator's duties. The principal duty of the operator employing oxy-fuel gas welding equipment is to control and direct the heat on the edges of metal to be joined, while applying a suitable metal filler to the molten pool. The intense heat is obtained from the combustion of gas usually acetylene and oxygen. For this reason, this process is called oxyacetylene welding In some applications other gases--such as Map propane, or natural gas--may beutilized to generate the intense heat necessary for welding. The skills required for this job are adjustment of the regulators, selection of proper tips and filler rod, ,preparation of the: metal'edges to be joined, and the technique of flame and rodmanipulation. The gas welder may also be called upon to do flame cutting with a cutting attachment and extra oxygen pressure. Flame or oxygen cutting is employed to cut various metals to a desired size or shape, or to remove excess metal from castings. The three main types of arc welding processes used today are shielded metal-arc welding, gas tungsten-arc welding, and gas metal-arc welding. Shielded metal-arc welders perform their skill by first striking an arc at the starting point of a weld and maintaining this electric arc to fuse the metal joints. The molten metal from the tip of the electrode is then deposited in the joint, together with the molten metal of the edges, and solidifies to form a sound and uniform connection. The arc welding operator is expected to select the proper electrodes for the job or be able to follow instructions as stated in the job specifications, to read welding symbols, and to weld any type of joint using the technique required. Gas-shielded arc processes have gained recognition as being superior to the metal arc process. With gas-shielded arc both the arc and molten puddle are covered by a shield of inert gas. The shield of inert gas prevents atmospheric contamination, thereby producing a sounder weld. The processes known:as gas tungsten arc welding and gas metal arc welding, sometimes called TIG and MIG, are either manually or automatically operated. Resistance welding operators are responsible for the control of machines which fuse metals together by heat and pressure. If two pieces of metal are placed between electrodes which become conductors for a low voltage and high amperage current, the materials, because of their own resistance, will become heated to a plastic state. To complete the weld, the current is interrupted before pressure is released, thereby allowing the weld metal to cool for solid strenqth. The operator's duty is to properly adjust the machine current, pressure, and feedsettings suitable for the material to be welded. The welder usually will be responsible for the alignment of parts to be assembled and for controlling the passage of parts through the welding machine Selection of the Proper Welding Process There are no hard and fast rules which govern the type of welding that is to be used for a particular job. In general, the controlling factors are kind of metals to be joined, costs involved, nature of products to be fabricated, and production techniques. Some welding jobs are best completed using the oxyfuel welding process as compared to shielded metal arc welding process Oxyacetylene welding the most pular oxy-fuel gas welding process, is used in all matal working industries and in the field as well as for plant maintenance. Because of flexibilityand mobility, it is widely used in maintenance and repair work . The welding unitcan be moved on a two-wheeled cart or transported by truck to any field job where breakdowns occur.Its adaptability makes the oxyacetylene process suitable for welding,brazing,cutting,anfdheat treating, The chief advantages of shielded metal arc welding are the rapidity with which a high quality weld can be made at a relatively low cost and the variety of applications. Specific applications of this process are found in the manufacture of structural steel for buildings,bridge and machinery shield metal arc welding is considered ideal for making storage and pressure tanks as well as for production line products using standard commercial metals Since the development of gas-shielded arc processes, there are indications that they willi be used extensively in the future welding all types of ferrous and nonferrous metals in both gauge and plate thicknesses Resistance welding is primarily a production welding' process. It is especially designed for the mass production of domestic goods, automobile bodies,