1、英文原文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 “d
2、eep 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
3、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. I
4、t 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 de
5、pth is higher than 2300 m or - mineral deposit temperature is higher than 38 C. 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 regi
6、ons. 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 t
7、he 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
8、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 capac
9、ity, 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
10、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
11、 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 clu
12、tched 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 rope
13、s. 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 ho
14、isting 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, B
15、lair 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 i
16、n South Africa, probably because they were invented there, particularly for the deep shaft use. There is one installation in England. Because of this hoists physical characteristics, and South African mining rules favouring it in one respect, they are used mostly for the deep shaft mineral hoisting.
17、 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
18、 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 hoists physical advantage is that the drum
19、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
20、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 bu
21、t the Blair is not used for man winding on a regular basis. The B.M.R. hoist has been built in three general styles similar to conventional hoists. The three styles are (Fig. 3 and 4): The gearless B.M.R. hoist at East Dreifontein looks similar to an in-line hoist except that the drums are joined me
22、chanically 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
23、 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 alwa
24、ys 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
25、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
26、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 angl
27、e. 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 H
28、ookes 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 r
29、ope 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 no
30、rmal 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
31、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 e
32、mergency 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 sa
33、fety 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 conveyanc
34、e 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
35、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 impl
36、ies 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 pay
37、load 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 ca
38、pacity 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 f
39、or 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 readi
40、ly 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 c
41、hanging 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
42、 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 ski
43、ps 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. It should be noted that some unconventional skips have been proposed (but not yet built and tested) that could offer skip factors a
44、s low as 0,35. 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
45、 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 sing
46、le lift systems are preferred. References 1 BAKER. T.J.: New South African Drum Hoisting Plants. CIM Bulletin, No 752, December 1994, p. 86-96. 2 CARBOGNO, A.: Winding Ropes of Uniform Strength. 1st International Conference LOADO 2001. Logistics and Transport. Hotel Permon, High Tatras, June 6th 8th
47、 2001 p.214-217. 3 GREENWAY, M.E.: An Engineering Evaluation of the Limits to Hoisting from Great Depth. Int. Deep Mining Conference: Technical Challenges in Deep Level Mining, Johannesburg, SAIMM, 1990 p.449-481. 4 HECKER, G.F.K.: The Safety of Hoisting Ropes in Deep Mine Shafts. International Deep
48、 Mining Conference: Technical Challenges in Deep Level Mining. Johannesburg, SAIMM, 1990 p. 831-838. 5 HILL, F.G, MUDD J,B: Deep Level Mining in South African Gold Mines. 5th International mining Congress 1967, Moscow, p. 1 20. 6 LANE, N.M: Constraints on Deep-level Sinking an Engineering Point of V
49、iew. The Certificated Engineer, vol. 62, No6, December 1989/January 1991 p. 3-9. 7 LAUBSCHER, P.S.: Rope Safety Factors for Drum Winders Implications of the Proposed Amendments to the Regulations. Gencor Group, 1995 Shaft Safety Workshop. Midrand, Johannesburg, November 1995, paper No 5 p.1-11. 8 MAC DONALD, D.H., PIENAAR, F.C.: State of the Art and Future Developments of Steel Wire Rope in Sinking an
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