1142 _____________________________________________________________________________________________________________ THE COLLIERY GUARDIAN. June 7, 1918. A winding rope is subjected to less detrimental treatment by a properly controlled electrically driven overhead Koepe hoist than probably by any other pos- sible type of winding device. Not only is the abrasion of the rope almost entirely eliminated, owing to the fact that it has no hard iron pulley to encounter, but the fatigue of the rope is reduced to a minimum owing to the steady winding movement and the absence of the destructive wave motion in the rope. A winding rope becomes most fatigued in the imme- diate region of the socket, partly owing to torsional stresses, but principally to the strain of the arrested wave motion. Since in this plant wave motion is practically eliminated, the author sees no valid reason for having to introduce numerous links to replace such liberal recapping as is desirable in the case of a rope subjected to the “flogging” of a steam winder. For subsequent ropes a softer wire would be prefer- able, drawn, say, to a breaking strain of 90 tons per sq. in., with a correspondingly larger rope instead of the 105 ton breaking strain steel used in the present If in. diameter rope. The object of using a rope of softer steel would be to reduce the tendency to fatigue from wave motion in the region of the socket. reach its correct shaft centre again until 1 in. has been grooved or worn out. The segment groove is allowed to wear down roughly another inch before the segments are changed or packed up. The depth of the groove in the new segments is not less than 3 in. Elm segments are found to give more satisfactory results than oak. Efficiency of Plant. The following tests were carried out: — 1918. (------>------- Item. Jan. 18. May 3. Duration of test ...............(mins.) 60 ... 683 Number of winds ..................... 29 ... 23 Average time per wind ..........(secs.) 124T ... 178 Total useful load raised (coal) ...(tons) 67’31 ... 54’85 Useful load raised per wind (coal) (cwt.) 46’40 ... 47’70 Total useful work done (shaft horse-power hours) 2’15 ... 50’65 Total energy consumption ___(B.T.U.) 81’25 .. 72’00 Total energy consumption (horse-powerhours) 108’87 ... 96’48 Energy consumption per ton raided (B.T.U.) 1’20 ... 1’31 Energy consumption per shaft horse- power hour ...............(B.T.U.) 1’31 ... 1’42 Over-all efficiency...........(percent.) 57'20 ... 52’60 Rope Slip. The question of slip between the winding rope and the driving pulley is of considerable interest and importance. The driving pulley is loaded as follows : (a) Empty cages, each 65 cwt.; (b) weight of empty tubs per cage (6 tubs at 5 cwt. each), 30 cwt.; (c) weight of coal per cage (6 tubs at 8 cwt. each, 48 cwt.; (d) weight of winding rope or balance rope on either side of the driving pulley, 28 cwt.; (e) weight of cage chains and attachment on the screw side, 16J cwt.; (/) weight of cage chains and links on link attachment side, 8J cwt. Although the coefficient of friction between the wood-lagged driving pulley and the rope is difficult to determine, the following experiment is instructive as helping to fix it: — The first trial gave better results than the second, chiefly because with a winding period of 124-1 seconds against a capacity of one complete wind, including decking time in 70 seconds, the plant was standing only 44 per cent, of the time as compared with 61 per cent, in the second case. As the motor-generator set consumes energy at the rate of 18 horse-power even when the plant is standing, the difference in the results is accounted for. If the plant were run at its full capacity, the over-all efficiencies would be 61-50 per cent, in the first trial and 59-20 per cent, in the second, an average of about 60 per cent, on full capacity. This latter figure is equivalent to 1-25 B.T.U. per shaft horse-power hour, which again with current from a modern efficient turbo-generator at, The cage with the screw attachment was resting on the shaft bottom keps, when the other side cage was raised empty at bank-level, the height of one deck without slip and without the tension of the bottom cage on the pulley, owing to its resting at the time on the pit bottom keps, as stated. The load T, therefore, on the rope at the point where it engaged with the driving pulley raising the cage at bank-level in this instance was : (a) Empty cage, 65 cwt. ; (d) winding and balance rope, 28 cwt.; (/) cage chains (link side), 8| cwt.; total T, 101| cwt. The load t on the rope at the other side at the point where it was leaving the driving pulley was : (d) wind- ing and balance rope, 28 cwt.; (e) cage chains (screw side), 16J cwt.; total t, 44| cwt. V/EX OF SecMEH 7S sxow/xa EXO OF LZX/1/X Fig. 2. Fig. 3. Faff, 5EC 770/Y OF Otf/twc Polley PPm w/rp SezME/vr. T The value —, therefore, or the relation of the load on one side ®f the pulley to the load on the other = 101J 4-441 = 2-56. Assuming the reliability of the formula used by Weisbach, Prof. Jameson and others, namely— T L°gc—= p, e where log = nap. log; T and t = greater and lesser tension on each side rope at the point where it makes or loses engagement with driving pulley; ^= coeffi- cient of friction; and 0 = rope contact with driving T pulley in radians; by utilising the value for ~ of 2’56 as above, p becomes the only unknown quantity in the equation and develops a value arrived at in this way of 0-3. Such a value is twice what is frequently ascribed to p under such conditions, but the author advances the foregoing with entire confidence, and considers that the flattened strand rope lying across the grain of the wood in the segments is the explana- tion. At the suggestion of Prof. Louis, the author had an experiment carried out with an 11 /16 in. length of Lang’s lay rope and the value of p in that test —487 lb. and 235-5 lb.—came out at 0-347, which, incidentally, seems to bear out the reliability of the formula quoted. In coal winding the value of T is : (a) Empty cage, 65 cwt.; (b) empty tubs, 30 cwt.; (c) coal, 48 cwt. ; (d) ropes, 28 cwt.; (e) chains (screw side assumed), 16J cwt.; total, 187| cwt. The value of t is: (a) Empty cage, 65 cwt.; (b) empty tubs, 30 cwt.; (d) ropes, 28 cwt.; (/) chains (link side assumed), 84 cwt.; total t, 131J cwt. * • . T The coal winding value, therefore, — =187|4-131^ Side View V/eu Fig. 4. Fig. 5. ■^'ScreH - 3 d/a. sodcA Uoci/e XhP it’ tiOCAef 2"tfr/c/c Me P/aYes 7 lr Figs. 4 and 5.—Rope Adjustment Screw and Links. = 142, which shows in comparison with the above figure of 2-56 a surplus margin of not less than 80 per cent, of frictional grip of the driving pulley on the winding- rope. The coefficient of friction of necessity varies con- siderably with the type of winding rope used, with the amount of lubrication, with the grain of the wood lagging, and the kind of wood used, etc. The author considers from other trials and observations that the experimental figure of 2-56, or, say, 2J determined as T described for the ratio of — is very near the full value of the frictional grip between the rope and the driving pulley, and that if the heavier side were loaded to a greater extent than 2J times the lighter side slip would occur. The winding rope, it may be added, is regularly oiled with old engine oil. Reverting to fig. 2, showing the tread of the driving pulley with the elm segments, the driving pulley segments wore down in the groove 2f in. during 19 months’ running, the guide wheel grooving down 2 in. in 20 months’ running. If the plant had been running at full capacity, this rate of wear would have been not less than doubled. The winding ropes are in their correct centres in the shaft when the segment thickness between the bottom of the groove in the segment and the pulley tread is 3 in. As the segments are renewed with a thickness of 4 in’ below the groove, the rope does not say, 13 lb. of steam per B.T.U., is equal to the iery satisfactory figure of 16J lb. of steam per shaft horse- power. With the plant working at about ha]f capacity, the actual steam consumption is about 23 lb. per shaft horse-power, the colliery generating sets con- suming 17 lb. to 18 lb. of steam per B.T.U. Since a winding plant cannot be run continually on full capacity, one of the disadvantages of the Ward- Leonard control with its motor-generator set is that the over-all efficiency of the plant falls off rapidly with intermittent working, as a result of the “dead” running of the motor-generator set. Comparisons and Conclusions. The calculated cost of this overhead electrically- driven Koepe winding plant was only 75 per cent, of the cost of an ordinary steam winding equipment for the same duty, taking all outlay into consideration, engine house, head gear, pulleys, etc., but excluding any charge for the capital cost of the colliery generating plant. The cost of the links and screw adjustments on the winding ropes, and other outlay incidental to the erection of an overhead winding tower, must be taken into account. On the Continent the Koepe plant mechanically and electrically is regarded as being 50 per cent, cheaper in first cost than drum winders (leaving such items as the headgear and engine house out of account). The Koepe system is particularly adapted to an electrical drive, the jerking of the engine (with its tendency to produce slip between the driving pulleys and the winding rope) being eliminated, whilst the electrically- driven Koepe plant is essentially suited to installation in the headgear. At the Adler Colliery, near Essen, however, the author has seen an overhead steam- driven plant (see Appendix) which appeared to work satisfactorily. The Ward-Leonard system is said to be preferable for an overhead winder, owing to its extremely sen- sitive control, but in the view of the German A.E.G. Company a direct-coupled three-phase motor is prefer- able when ~ is under 0’18; a Ward-Leonard control when ^0 2 is between 0’18 and 0’28; and an Ilgner set when 0) 2 exceeds 0’23; where s — winding depth, in metres, and t = winding time, in seconds. It is probable that the Koepe winder, owing to the lesser weights of the moving parts, is capable of a higher efficiency than any other type of winding plant. Continental practice shows a consumption of 40 lb. of steam per shaft horse-power hour with an efficient steam-driven Koepe plant in a ground-level engine house, which may be compared with 45 lb. of steam per shaft horse-power in an efficient steam-driven drum winder, or, in the case of many steam winding engines, of anything over 100 lb. In electrically-driven winders on the Continent the Koepe plant with a Ward-Leonard control and a ground-level engine house is stated to average 1-50 kw. hours per shaft horse-power hour, while the electrically driven drum winder is put at 1-65 kw. hours per shaft horse-power. Recent British practice compares very satisfactorily with these figures, 1-50 B.T.U. per shaft horse-power not being unusual with electrical drum winding. By placing the Koepe plant on the headgear, the efficiency is improved by dispensing with the head- gear pulleys, the average consumption per shaft horse- power for the two tests carried out on the Plenmeller plant, as tabulated above, being 1-35 B.T.U. per shaft horse-power. If the plant had been running at full capacity, the test figures would have approximated to an over-all efficiency of 60 per cent., 1-25 B.T.U., or 16J lb. of steam per shaft horse-power hour, assuming an electrical generator of 13 lb. of steam consumption per kw. hour. It is probable that 16| lb. of steam per shaft horse-power is not more than a tenth of the steam consumption of many steam winding engines in regular use. In summarising the Koepe’s advantages and dis- advantages, the following may be taken as the prin- cipal considerations: — Advantages. (1) High efficiency; (2) low capital cost; (3) lesser weight of moving parts; (4) one rope only required; (5) reduced liability to failure of the winding rope due to steady winding; (6) compactness of plant; (7) Reduced liability to overwinding and the dispens- ing with detaching hooks; (8) headgear pulleys dis- pensed with ; (9) shorter winding rope ; (10) improved rope lead. The latter three considerations only apply if the plant is mounted on the headgear. Disadvantages. (1) The inconvenience resulting from being unable to detach either cage for any purpose without securing the winding rope; in short, the plant cannot con- veniently be operated at all for any purpose, such as raising and lowering machinery, unless both cages are attached to the winding rope; (2) the necessity for rope length adjustment arrangements; (3) the necessity, under most circumstances, for a balance rope; (4) the comparative inaccessibility of a high tower for the replacing of heavy pieces of machinery in case of breakdown. ’ (The latter consideration ob- viously only applies in the case of overhead plants.). Disadvantages which are frequently urged against the Koepe plant after casual investigation are: (1) Slip between the pulley and the winding rope ; (2 )probable fall of both cages in case of winding rope failure. These, however, need not be taken seriously. Whilst there is no positive hold of the winding rope on a drum, the frictional figures show ample fric- tional grip for ordinary winding, even when the rope is well oiled. Owing to the steady winding conditions, the risk of failure of a Koepe winding rope is so small as to counterbalance the disadvantage of the certainty of both cages falling to the pit-bottom. Incidentally, the falling is not necessarily confined to the one cage in the event of the failure of a drum winding rope. Recapping. With regard to the recapping of the rope, the author regards the Continental custom of allowing a Koepe rope to work for two years without recapping, and then scrapping it, as unduly rigid practice. He con- siders that with the British periodical recapping of the rope, the removal of 6 in. or so from each end, using efficient cappies, is more satisfactory, and allows the full 34 years’ life for the rope. A Koepe rope treated in this way will be found to have undergone less fatigue in any part than a similar drum winding rope, particularly if the plant is an overhead one. The issue between the modern overhead Koepe plant and the drum winder steam or electrically driven can be reduced almost entirely to a comparison of advantage No. 1 (“efficiency”) against disadvantage No. 1 (“inconvenience”). The balance is so close that the author is disposed to regard the choice between the Koepe and the drum winder as a matter of personal temperament. This conclusion would appear to be borne out by the fact that on the Continent the Koepe principle appears to enjoy periodical rather than continual favour, so far as new construction is concerned. Although personally inclined towards the sim- plicity of the drum winder (either steam or elec- tric, according to the available power supply), the author has no alternative but to state that, sub- ject to the inconvenience referred to, the electrically driven overhead Koepe hoist is capable of a high winding efficiency. It is quite dependable and re- liable, is particularly suitable for winding men, and is cheaper in first cost.