SAFETY IN WINDING OPERATIONS. 



By J. A. Vaughan, M.I.C.E., MT.Mech.E. 

 (Read July lo, 191 8.) 



The author has chosen a title which covers a very large 

 field, but intends to confine his remarks in the main to the ques- 

 tion of the safe handling of the winding-engine, having recently 

 dealt with the subject of the winding-rope in the proceedings uf 

 another institution. 



On the Witwatersrand, besides a large number (about i.oooj 

 of small auxiliary hoists or winches of average horse power — t6 

 steam and 65 electric — there are installed main winding plants to 

 the extent of 443 in number, of collective horse power totalling 

 173,038. These statistics refer to 31st December, 1916. and are 

 the latest obtainable. The comparative figures subsequently 

 tjuoted will therefore be taken for that date, although later figures 

 are in these cases available. 



Of this total of 443 main winding plants, 262 are driven by 

 steam and 181 by electric motor. The number out of use is not 

 known, but the published return shows that 372 were licensed for 

 the conveyance of persons, the maximum capacity of the con- 

 veyance being rated for 10,790 persons. 



Taking 200,000 persons as the number employed under- 

 ground on the Witwatersrand, it would need only 20 trips to 

 lower and raise this complement in the 242 shafts. But the 

 lowering and raising operations are not always simultaneous, the 

 loading of the cages is not always up to full complement, and the 

 trips at the beginning and end of the shifts are not nearly all the 

 occasions on which persons are being transported. 



Instead of trying to estimate the number of hoists in which 

 there is a human freight, it is better to regard the general wind- 

 ing operation in trying to estimate the accident risk. It has also 

 to be remembered that accidents such as overwinding cause 

 annually great and expensive damage to plant, besides the 

 personal casualties that will be treated later on. 



Let us suppose, what are very close to the facts, that 400 

 main winding i:)lants are regularly at work, and that an average 

 of nine trips per hour are made ; a " trip " being the downward 

 and upward journey of the conveyance, whether the companion 

 drum is sinmltaneouslv in motion or not. The annual total will 

 be just over 31.000,000. while the winding accidents such as we 

 are considering amount to about 62. ecjuivalent to a rate of i in 

 500.000. This low accident rate could be regarded with complacency 

 if it were felt certain that the mistake was in all cases inevitable 

 and the resulting accident absolutely unpreventable. Regarded 

 in another way, it may be assumed that 800 certificated engine- 

 drivers are responsible for 50 accidents annually, so that if each 

 driver was restricted to one accident he would have a chance of 



