THE INSTALLATION OF A KOEPE WINDING PLANT AT A WORKING SHAFT

ABSTRACT

Brief descriptions are given of the work involved in preparing a busy operating shaft to receive its planned Koepe winder. The more important features of the operation are detailed, including the headgear arrestor gear, the tail rope loop protection, and the loading box. Brief details of the conveyances are given. The method of installing and changing the head and tail ropes is explained. Features of the winder are described including the tread truing device, the 200-ton jacks for raising the drum shaft, the braking system and the speed controlling devices.

INTRODUCTION

At shafts, which are planned for large future outputs, the installation of one of the three large winders can be deferred sometimes until the decision is taken for the expansion of operations. It has been found convenient in such cases to construct a concrete headgear with the provision in its design for the subsequent addition of either a tower-mounted Koepe winder or a ground-mounted drum winder. Such were the conditions anticipated regarding the shaft and headgear in question. In this case, a tower-mounted Koepe winder was decided upon.

The 26 feet 0 in diameter circular shaft, 5 000 feet deep, had been well served by three winders

1. A 5 200 hp A.C. dynamic control rock winder operating a skip with a capacity of 11 tons. The skip bridle could also accommodate a three-deck cage to carry 69 men.

2. A 2 700 hp Ward-Leonard control man and material winder operating single-deck cage to carry 50 men.

3. A temporary service winder operated in the proposed Koepe winder compartments. This proved most necessary and invaluable to the shaft system and accomplished an enormous amount of work during its period of operation prior to the commissioning of the Koepe installation.

Fig. 1 shows the initial layout of the shaft and its winders. Fig. 2 shows the final layout of the winders. Also shown are the Koepe winder M.G. set which is mounted at ground level, and the rope installation winder.

The installation of the Koepe winding system was coincident with the completion and commissioning of a 150 000-ton capacity reduction plant. The capacity of the shaft prior to the installation of this new winder had reached its peak, with the two main winding plants working as "busy hoists". The diagrams as shown in Fig. 3 indicate the extent of their duties.

The rock winder could only average 22 hoisting hours per day at an average of 28 trips per hour, the payload of 11 tons being drawn from three loading positions in the shaft. The monthly capacity of this winder was therefore about 174 000 tons of reef and waste.

The men and material winder could only achieve an average of about 310 trips per day, due to the multiple clutching operations necessary to serve eight main stations with sufficient men and material to provide the abovementioned tonnage.

To augment the capacity, a nearby ventilation shaft was used for one shift daily to lower material to three of the upper producing levels.

SHAFT PREPARATION

This busy shaft had to be made ready to accommodate the Koep., winder, which was to be a single purpose winding plant to hoist ore from the lowest loading point in the shaft. This winding plant would allow the other two main winding plants to handle more men and material to meet the rising production. Fig. 4 is a cross-section of the shaft showing the compartments. Fig. 5 shows the position of the drum of the Koep winder relative to the compartments.

The preparation of the shaft involved working long hours often in difficult conditions, initially only at weekends, but, later daily, to adhere to a limited time schedule. This work was done from specially constructed cages operating in the Koepe compartments using the service winder, whilst normal hoisting procedure continued with the main winders. The work involved the installation of the tail rope protection cover at the shaft bottom, the installation of the 20-ton measuring bins and chutes and the erection of a specially protected 45-foot-long ladderway in the shaft above the loading box, to facilitate the installation of the head ropes and tail ropes. Alterations had to be made to the steelwork at all shaft stations. Pipes and cables had to be removed, repositioned or installed throughout the shaft. The steelwork at the bank for rope installation and the tipping paths and chutes in the headgear had to be installed. Finally, after the service winder and its equipment had been removed, the arrestor structure had to be erected in the headgear in a position previously occupied by the sheave wheels of the service winder.

HEADGEAR SUPERSTRUCTURE

Because of modern sinking methods, the dimensions of sinking equipment had become larger and the total weight of kibbles, ropes, and multiple deck sinking stages can amount to about 130 to 140 tons. The headgear during the sinking, therefore, had to be of design no less robust than that of the permanent structure required to serve the shaft after the addition of the tower-mounted Koepe winder.

The headgear is of shell form, square in section, to fulfill its function of supporting the Koepe winder, the headgear sheaves at the desired elevations for the other two ground-mounted winders, the reef and waste bins and the internal steel frame. The amount of internal steelwork is considerable and it could weigh as much as 160 tons.

Simultaneously with the abovementioned construction work in the shaft, the foundation for the Koep winder was superimposed on the existing headgear and the Koepe winder was erected. About 1 800 tons were added to the already massive structure.

The foundation for the winder progressed as shown in Figs. 6 to 9. This foundation of reinforced concrete accounted for 1500 tons of the superimposed weight.

Fig. 10 shows the completed headgear.

Much forethought had been applied to the design of this headgear. Apart from the super-imposition of the Koepe winder, the following loads had to be considered: -

(a) Dead loads

These loads included the weight of the sheaves, platforms, beams and bearings, internal steelwork, and the weight of the structure itself.

(b) Live loads

These loads included the weight of the rock in the ore bins incorporated in the structure and the super-imposed loading by the operation of the other winders.

(c) Wind load

This load was based on a wind velocity of 70 miles/h.

(d) Rope loads

(i) For normal conditions, rope loads were taken as being equal to the weight of the ropes together with the weight of the fully-loaded conveyances.

(ii) For the worst type of condition, a load that would cause the ropes to break should a conveyance jam in the shaft or should a conveyance be arrested by the crash beams.

HEADGEAR ARRESTOR GEAR

Conveyances operated by the Koepe system cannot be detached from the winding ropes in the event of an overwind. It is, therefore, necessary to introduce a method of arresting the upper and lower conveyances and with them the moving rope system.

In the headgear, situated below the winder floor, are 2 reinforced concrete beams approximately 14-foot deep x 4-foot-wide crossing the headgear structure and carrying the winder (See Fig.ll)

Slung below these beams for each compartment is a 2-inch-thick mild steel catch plate, the friction block slide, and the jack catch posts, all of which made up the conveyance arrestor structure. The overall length of this structure is 37 feet. The arrangement of the 60 lb rails and jack catch posts for each compartment is shown in Fig. Il.

The spring-loaded keeps or jack catches are as shown in Fig. 12 and extend the entire length of the specially constructed supporting posts, since the point at which the ropes will break cannot be accurately predicted. Their robust construction, close spacing, and quick spring action provide a positive means of retaining a conveyance in the headgear should the necessity arise.

To each of the four 60 lb rails arranged as shown in Section M - M of Fig.ll, specially constructed friction blocks are secured. Enlarged detail of such a block is shown in Fig. 13. When mounting a block on the rail, its braking or friction components, namely, the cast iron and phosphor bronze wearing slippers, are pressed against the railhead by the tightening action of the four 1 in diameter securing bolts with springs on the outer cast steel body pieces. By this means the block can absorb impact by friction. As many of these blocks may be fitted to each rail as desired. At present four friction blocks are fitted to each rail, making a total of 32 blocks per compartment. To ensure that the crosshead of the skip bridle will strike the friction blocks should the conveyance travel past its tipping point, the adequate lead-in is provided to the arrestor structure, and only 3/8 in clearance is allowed round the bridle crosshead for entry into the structure.

Each bolt positioning the friction block on the slide rail is tightened to a torque of 200 foot-lb by a torque wrench. The blocks are staggered at intervals along each rail, so that, on impact by the crosshead, each block would resist in turn. The resistance would gradually build up to avoid shock and breakage of the rope until the conveyance had entered the zone of the jack catches. The shock-absorbing effectiveness of this friction block is about 2 to 10 tons per yard of movement.

Tests were carried out to determine the effectiveness of this friction-type arrestor block. A weight of 3150 lb was dropped from various heights onto a friction block secured to a rail, the bolts in the block being tightened to the abovementioned torque. New shoes were used for each test.

The results of these tests show that a considerable resistance can be set up using multiple friction block system, but this will be sufficient to take care of a minor overwind.

It is considered, however, that in the event of a major overwind at high speed, nothing could prevent a catastrophe. It is hoped that the two enormous 14-foot x 4-foot reinforced Concrete beams at the upper extremity of the wind will resist the impact of the Conveyance and no bending of the beams should occur. The head ropes would break and the free tails would be thrown Over the winder drum and would probably fall to the bottom of the shaft in the opposite compartment without endangering the driver since his control position is remote from the line of action of the ropes. The conveyance should be held in the headgear by the arrestor gear. 

A serious overwind could endanger the winder drum, but because of its heavy boss construction and because the drum shaft is short and massive, the damage should be limited.

 SHAFT BOTTOM TAIL-ROPE LOOP PROTECTION

The design and construction of this protection are of importance to the Koepe winder installation because not only must it serve as a tail rope protection but it must also in no way restrict rope movement or looping. In this case, the shaft bottom Construction serves a two-fold purpose; all shaft Conveyances are stopped at this level in the event of an overwind or accident; the tail rapes are protected; this installation is commonly known as "crash beams". It should be noted that the men and rock conveyances operate within the loop of the tail ropes.

The structure consists of heavy section 16 in x 6 in R.S.J. spanning the shaft and suitably braced with channel sections to form strong trusses; see Figs. 14 to 17. The beams support steel top-hat guides arranged in a camelback form (T) to deflect falling spillage or material away from the loop of the tail ropes. Other steel top-hat guides are positioned as shown at (U), to allow spillage to build up to provide a cushion for falling spillage or material. The 9 in x 3 in timber cladding (V) provides a clear and unrestricted rubbing surface for the loops of the tail ropes. These timbers are secured to the steel uprights by phosphor bronze bolts, whose heads are countersunk into the timber. The timber cladding (V) is protected on the outside from falling spillage by more top-hat guides, arranged as shown at (W).

Timber baulks (X), size 9 in x 9 in, are provided to form a rubbing surface for the tail ropes in their passage through the crash beams just before the loop is formed. These baulks are secured to the steelwork by phosphor bronze bolts whose heads are countersunk into the timber.

Further 9 in x 9 in timber baulks (Y) shaped to fit the shaft were secured to the sidewall by expanding shell bolts and securing straps to ensure that the tail ropes would have timber protection on this side as well. These baulks are carried down for 15 feet below the end of the steel guide of the compartment.

Two specially constructed rubber covered rollers were installed at (Z) their purpose is to help spread the tail ropes, should they hang in too narrow a loop. These rollers can turn freely and speedily to reduce wear on the rollers should the ropes touch them.

Adequate lighting is provided at the tail rope inspection tunnel for handling and inspection purposes. Also at this point, bell and telephonic communication are provided to the shaft system. To enable the tail ropes, the rollers, and the crash beam structure, in general, to be examined and inspected, three aluminum cars were constructed. These are stored in the tail rope inspection tunnel. When an inspection is to be made, they are pushed out across the shaft and joined together to form a safe working platform. Aluminum extension ladders are provided to reach the upper parts. An elevator serving the shaft bottom is used for quick access to the tail rope inspection tunnel.

THE BOTTOM DISCHARGE SKIPS

The type of bottom discharge skip which has come into favor during the past few years is a modification of the original "Saunders" and "Lake Shore" basic designs. The main features of the 20-ton capacity skip used are shown in Fig. 18. The skip pan is hinged at the top and its lower end is swung out of the bridle to discharge into the headgear bin by means of a roller engaging a suitable tipping path. Rollers attached to the bottom door of the pan run over profiled horns attached to the bridle so causing the pan to open. After tipping when the skip descends and the skip pan returns to the vertical position and simultaneously the bottom door closes and locks.

The pan weighs 8.6 tons, while the bridle and attachments weigh 11 tons, giving a total weight of 19.6 tons. All headrope and tail rope attachments are of "Mangear "steel. The skip and the associated tipping path is designed to bring the side of the skip pan and the bottom of the door into line in the fully tipped position so that the ore has a straight path for discharge. In operation, this skip discharges 20 tons cleanly in 6 seconds.

It will be noticed that the skip bridle has no gear for equalizing the tension in the four ropes. The head ropes are directly coupled to the bridle cross-head by means of pear-shaped wedge type cappels. See Figs. 19 and 24.

Sealed ballbearing swivels are provided where each tail rope is attached to the bridle tailpiece to release any residual torque or twist which may build up during operation.

The design of the bridle incorporated three important functions, viz:

i.  Flexibility; owing to its extreme length (some 40 feet) it had to be made flexible to negotiate any possible irregularity or misalignment in the shaft guides.

ii. Strength; in a shaft of 5 000 feet in depth, the load produced by the tail ropes tends to close the bridle in. The strong construction of the crosshead and tailpiece will be seen.

iii. A quick interchange of pans; this is an advantage when maintenance is necessary. The scheduled maintenance on the bridle occurs less frequently than is necessary for the pans.

The solid-tired roller units, attached at either end of the bridle assembly, serve to reduce wear on the shaft guides and bridle slippers and reduce shock to the bridle assembly because of bad joints in the guides or faulty plumbing of the guides.

HANDLING ARRANGEMENTS

Specially made carriages are provided on the shaft bank to facilitate handling of the skip bridle and pan since this weighs 19.6 tons. The carriages had to be of an abnormal length to ensure adequate support for the side channels of the bridle to prevent them from bending (See Fig. 20). The carriage had to be high enough to enable the crosshead and tailpiece to clear the track. Due to the large wheelbase, necessary for stability, a bogey had to be included in the design to allow the carriage to negotiate curves in the track near the shaft.

A rail traverser was installed for the quick positioning of the conveyances on the bank. Suitable overhead crawl beams and 10-ton pneumatic rope blocks are provided for the easy and effective handling of the conveyances, or parts thereof, into or out of compartments of the shaft.

 UNDERGROUND SKIP LOADING ARRANGEMENTS

The arrangement for loading the skips is of the fixed volume. measuring flask type. The ore pass control chute IS fitted with a pneumatically operated radial cut-off door. A straight type fully open or fully closed pneumatically operated quick discharge door is used for the measuring flask. The latter door has a toggle lock to prevent accidental opening by the weight of the ore. Fig. 21 shows the general arrangement of the system. It also indicates the position the skip bridle must be in for the installation or changing of a head or tail rope. The ladderway in the shaft is permanent and is required for access to the headrope cappels when the bridle is in the abovementioned position.

The fixed volume measuring flask may hold slightly different weights of rock due to incorrect loading by the skipman or because there are more fines in the ore. The skipman must make sure that the measuring flask is filled to the predetermined level to ensure the correct operation of the Koepe winder under semiautomatic conditions. From operating experience, it has been found that the ropes stretch about 20 inches as the skip is filled. If the skip positioning magnets are accurately located, spillage from the loading flask is negligible. Unless the skip is in the correct loading position, an interlocking magnetic contractor prevents the discharge door of the measuring flask from being opened. After loading, the skip cannot be hoisted, unless the measuring flask door is dosed and locked in position. An electrical interlock is arranged to prevent the winder moving before this door is closed.

 THE METHOD ADOPTED FOR INSTALLING THE WINDER ROPES

The four head ropes used are to the following specifications: -

Diameter 2 in, weight 7.375 lb/ft, breaking load 213 tons.

Class of steel: Special Improved Plough galvanized.

Construction of rope: Non-spin 18 (12 over 6), outer strands R.H. lay, inner strands L.H. lay.

Construction of strands: 12 outer; 6 inners.

Wires 8 over 2 parallel 29(11 x 12 x 6 Triangular) with 3 filler wires.

The specifications for the four tail ropes used are as follows: -

Diameter 2 in, weight 7.721 lb/ft, breaking load 206 tons.

Class of steel: Best Plough galvanized.

Construction of rope: Non-spin 15 (9 over 6) Outer strands R.H. lay, Inner strands L.H. lay.

Construction of strands: 9 outer; 6 inners.

Wires: 8 ribbon 27 (9 x 12 x 6 Triangular) with 3 filler wires.

The head ropes are attached to the bridle crosshead by means of pear-shaped wedge type cappels. The tall ropes are attached to the bridle tail-piece by means of sealed ball-bearing swivels and straight wedge type cappels.

For installation of the ropes and for subsequent maintenance operations, a permanent rope winder is provided. This rope service winder is a 120 hp A.C. grid controlled machine with a single drum having a diameter of 5 feet and a width of 6 feet. It is geared to produce a rope speed of 100 ft/min.

 Arrangements for installing and changing ropes

The four head and four tail ropes on their reels, as received from the manufacturer were mounted on steel trestles in suitable positions on the bank and were then wound onto the rope service winder in turn

as required. For installation, each rope was ordered some 200 feet longer than required.

It was cut to the correct length when in position in the shaft compartments.

Efficient signaling and telephonic communication systems were provided at all main operating points.

A colour code was introduced for each rope and its respective attachments. This proved beneficial to the personnel underground where the lighting was fair but working conditions were wet and uncomfortable. The winder crane (35 long ton capacity) and the auxiliary crane (5 long ton capacity), situated in the engine room on top of the headgear, were used for handling the ropes at various stages of installation.

A 10-foot diameter sheave wheel mounted on the bank on suitable steelwork was provided and this could be placed in various positions as required. An auxiliary 30 hp single-drum winch was conveniently positioned on the bank and was fitted with a ? in diameter rope of suitable length. All the necessary tools, clamps and slings were provided.

 Head rope installation procedure

1.      The auxiliary winch rope A was raised to the Koepe floor level by means of the 5-ton auxiliary crane B passed through the openings of the winding compartment and over the Koepe wheel and lowered to the bank on the opposite side of the headgear. Fig. 22A. This rope was attached to the No. 1 head rope.

2.      The end of No.1 head rope wound on the service winder C was raised to Koepe floor level via the bank sheave wheel and through openings of the winding compartments by means of the auxiliary winch A., The head rope was pulled over the Koepe wheel, through the openings of the opposite compartment to bank level. The Koepe wheel could idle freely. Fig. 22B.

3.      No.1 head rope was attached to the pear-shaped wedge cappel on the No. 1 bridle. The bridle was pulled into the compartment with the service winder C and lowered in the guides to the predetermined position at the loading box where the bridle was supported by means of cleats and a bearer between guides. The bridle was piloted through the shaft with the Koepe wheel idling (Fig. 22C).

4.      The slack in the rope was taken up and the head rope was clamped at bank-level D on the auxiliary winch A side to the steelwork provided, by means of a suspension gland type of clamp. (Fig. 22C).

5.       No. 1 head rope over the Koepe wheel was slackened, the loop was pulled up by means of the two 2-ton chain blocks E and the loop was tied to the brake tension rod F on the winder to free the wheel for the next rope. The rest of the rope was removed from the service winder C (Fig. 22D).

6.      The above procedure was repeated for No.4, No.3, and NO.2 head ropes, the ropes being attached to the special crosshead instead of to the bridle. The crossheads are removed at the main pump station level (4620 feet below the surface) after being piloted through the shaft. Each rope is then lowered further with its pear-shaped wedge cappels attached for attachment to the bridle.

7.      Bridle No.2 is now lifted to the predetermined position in the headgear (Fig. 22E) by means of the 5-ton auxiliary crane B with its rope doubled down or by means of the auxiliary winch A with its rope suitably reeved. The bridle is supported on bearers.

8.      Replace all head rope loops on Koepe wheel. Secure each rope to the top of bridle No. 2 by means of the pear-shaped wedge cappels.

9.      Bridle No. 2 was lifted by means of the main crane G using a pennant attached temporarily to one rope, the bearers supporting the bridle were removed and it was lowered until suspended by the head ropes. This completes the head rope installation.

Tail rope installation procedure - See Fig. 23

1.      From the service winder C, No. 1 tail rope with its cappels attached is passed over the bank sheave wheel and connected to a temporary crosshead. The crosshead is piloted through the shaft compartment to the main pump station level where the crosshead is removed and returned to the surface. The end of the tail rope is then lowered further and fed through the crash beam openings. It is connected to the rope from the service winch H and pulled up to the bottom of No. 1 bridle where it is attached to its respective swivel.

2.      The tail rope loop is adjusted. The suspension gland type clamp was secured to the rope and was supported on the steelwork provided at the bank. The tail was removed from the service winder C made off to length and attached to the bottom of bridle No.2, using the straight wedge type cappels connected by the rope swivel to the bridle.

3.      After repositioning the bank sheave wheel, the above procedure was repeated with Nos. 4, 3 and 2 tail ropes respectively.

 To transfer the load to the Koepe wheel

1.      A pennant was suspended from the main crane hook G and clamped to No. 1 head rope in Koepe wheel pit on the auxiliary winch side. The head rope was lifted slightly to free the suspension gland type clamp on bank-level D and the clamp removed. The pennant was slowly lowered to transfer the weight to the Koepe wheel.

2.      This operation was repeated for the other head ropes.

3.      The steelwork for supporting the clamp was removed.

4.      The Koepe winder was used to free the clamps on the tail ropes. The clamps and their supports were removed.

5.      The Koepe winder was used to release No. I bridle supports and they were removed. The initial installation of all ropes was completed in four days, working during daylight hours only except on the fourth day when work was carried on to midnight to complete the job. The normal shaft operations were held up for only 12 hours during this operation resulting in little dislocation to production.

SHORTENING THE ROPES

Due to rope stretch, it is necessary to shorten the head ropes from time to time. A simple and effective method was devised to carry out this operation. The procedure is as follows: -

1.      Both skip pans are removed from their respective bridles in turn at the bank level.

2.      On the side to be shortened, a specially made pennant is clamped to each rope at a suitable distance above the cappels and a second pennant is clamped to the free end of each rope where it protrudes from the cappels, the bridle being at the bank level. (See Fig. 24.)

3.      A 2-ton chain block is attached between each pair of pennants and a slight amount of tension is applied. The hand chains of all four chain blocks are securely fastened to ensure their safe passage through the shaft.

4.      The bridle, with the chain blocks attached, is driven down and stopped at the lower station elevation (4560 feet below the surface). Two 1 in diameter slings are passed through the bridle crosshead and are secured to the steelwork at the station.

5.      The winder wheel is turned a small amount to cause the headropes to hang slack in the shaft. The bridle and the short length of tail rope below it is supported by the slings. (See Fig. 25.)

6.      In turn, the pear-shaped wedge in each cappels is freed and the corresponding free rope end is pulled through to shorten the rope the correct amount. The attached chain block is used for this purpose. The cappels wedge is then reseated.

7.      The bridle is raised sufficiently to enable the lings supporting it to be removed and the bridle is returned to the surface, where the chain blocks and pennants are removed. The free ends of the ropes are cut to suitable lengths and are clamped to the head rope. The pans are then returned to their respective bridles. The time taken for the complete shortening operation is about 3 hours. The length of rope taken up at each adjustment is limited to 3 feet. The shortening operation is done alternately at one end or the other to obviate the possibility of broken wires occurring in the rope where it goes around the wedge in the cappels and to prevent the accumulation of slack on one side only. Fig. 26 indicates stretch in the head ropes relative to the work done by the ropes.

Using the rope installation equipment, the procedure is as follows: -

1.      The conveyances are brought to the rope installation positions, that is, one above the loading box, the other about 30 feet above the bank m the headgear.

2.      After clamping it to the winch rope, the tail rope is disconnected from the conveyance at the loading box and the tail rope is lowered to the bottom of the shaft by means of the auxiliary winch H.

3.      The new tail rope having been wound onto the rope service winder C and having had a cappels attached is passed over the sheave wheel at the bank and is lowered to the shaft bottom, being piloted all the way. The auxiliary winch H is used to lift the capped end of the rope to the underside of the conveyance at the loading box. The cappels is connected to the bridle.

4.      The loop in the tail rope is then adjusted to suit the other ropes and the rope is clamped at the bank by means of a suspension gland type clamp D. The rest of the rope is removed from the rope service winder C.

5.      A rope is now wound on the rope service winder C passed over the sheave wheel at the bank and is clamped to the old tail rope, the old tail rope is pulled up a short distance to enable the connecting pin to be removed from the attachment under the conveyance in the headgear. The old tail rope is wound onto the service winder drum until it is removed from the shaft.

6.      The cappels is now attached at the correct distance from the free end of the new tail rope and is connected to the underside of the conveyance in the headgear. The suspension clamp D and its supporting steelwork are removed.

 The method of changing a head rope

To reduce handling to a minimum and to ensure that the used head rope could be recovered intact so that it can be used as a tail rope if necessary, the following procedure was adopted after much deliberation (see Fig. 28)

1.      The bridle of the conveyance on the side nearest to the rope service winder C is driven to the lowest main station of the shaft and is supported by the steelwork at the station as before. The opposite conveyance will be just below the bank level. The winder wheel is driven a short distance to cause the head ropes to hang slack. The head rope to be changed is disconnected from the bridle and the cappels are removed. The winder wheel is rotated until the remaining head ropes lift the bridle and the bridle support is removed.

2.      The opposite conveyance is brought to the bank level. The head rope to be removed is now clamped and suspended from support steelwork D at the bank-level in the compartment nearest the service winder C. The opposite conveyance is hoisted to release the tension in the rope to be changed. The rope is disconnected from the bridle in the headgear, passed over the Koepe wheel and lowered to bank-level by means of the bank winch A.

3.      The new head rope having been already wound onto the service winder C is lowered via the bank sheave to the conveyance at the lowest main station and the end secured in the cappels which is connected to the bridle in place of the head rope just removed. The man and rock hoist conveyances are used as platforms from which this work is done. The new head rope is clamped at the bank and the rest of it is removed from the service winder. The end of the rope is passed over the Koepe wheel, the cappels fitted and connected to the conveyance in the headgear.

4.      The end of the old rope is secured to the drum of the service winder C and the used rope is removed from the shaft via the sheave wheel at the bank.

5.      The winder is moved sufficiently to release the suspension clamp on the new rope at the bank level. The clamp and its supporting steelwork are removed.

6.      The bridle that is underground is now moved to the station level supported there and the final tensioning of the new rope is carried out as described previously.

The method of changing the bridle

The following procedure is used to change a bridle.

1.      Both skip pans are removed at the bank level in turn.

2.      The hinged guides in the headgear of the compartment t concerned are opened.

3.      Steel bearers are placed across the compartment at bank-level to support the suspension type lamps, the bridle being in the headgear above the bank. All four tail ropes are clamped at a point about 6 feet below the cappels.

4.      The winder drum is rotated slightly to allow the clamps to take the weight of the tail ropes.

5.      Steel bearers are placed across the opposite compartment at bank-level to support four 50 ton jacks, the jacking beams, and the suspension type clamps.

6.      The four head ropes and the suspended bridle are lifted about 12 inches by operating the jacks, to give sufficient slack to enable the head ropes to be disconnected from the bridle in the headgear. The auxiliary winch at the bank is used to support the bridle to allow it to be removed from the compartment.

7.      The new bridle is moved into the compartment using the auxiliary winch, the head ropes are attached and then the tail rope connections are put on.

8.      The jacks are lowered, the clamps on the ropes are removed and the supporting steel bearers on that side are taken out of the compartment.

9.      The winder drum is rotated slightly to lift the newly installed bridle and tail ropes. The clamps on the tail rope are removed and the supporting steelwork taken from the compartment.

10.  The newly installed bridle is now directed into the guides and hinged guides are closed and secured.

 SOME FEATURES OF THE WINDING SYSTEM

The four-rope Koepe winding plant mentioned this paper is the largest of its type ever to be designed and manufactured in the Republic of South Africa. It is probably the largest Koepe winder to date to be installed at a South African gold mine.

Description of the winding system

M.G. set and exciter unit: Ground-mounted

Koepe winder: Tower mounted, 192 feet 0 in above ground level

Horsepower: 5000

Control: Twin motor, Ward-Leonard, acceleration, and retardation by magnetic amplifiers. Helical controller and Ardic controller for super-vision of retardation

Hoisting Depth: 4917 feet from box to tip

Hoisting speed:  3000 feet/min

Skip payload:  20 ton (of 2000 lb)

Skip weight:  19.6 tons

Type of Skip:  Bottom discharge

The diameter of the winder drum: 19 feet 6 in

Drum treads: Hard rubber (80 Shore hardness, locally made)

Winding cycle: About 125 seconds from box to tip. Manual loading, 24 skips/h.

Head ropes: 4 - 2 in dia. non-spin, each weighing 18.5 tons. Breaking load about 210 tons

Tail ropes:4 - 2 in dia. non-spin, each weighing 19.5 tons. Breaking load about 205 tons

Headrope attachments:  Pear-shaped wedge friction cappels (G.H.H. type)

Tail rope attachments: Reliance straight wedge cappels with swivel

Electrical braking: Using regenerative current

Mechanical braking: Application by springs, release by hydraulic control

Rope creep compensation: Automatic

Conveyance arrestor gear: Rail friction blocks and jack catches

The winder is driven by two direct-coupled overhung D.C. motors positioned at either end of the main drum shaft. These motors are controlled on the Ward- Leonard principle and are supplied with direct current from a twin-generator M.G. set situated on the ground level. Each motor is rated at 2600 hp at 49 rev/min.

The control equipment is arranged for either automatic winding or manual control. Magnetic amplifiers are used to control the field system on an exciter unit which is provided with two excitation windings, one being for each direction of rotation of the winder motors. The output of the exciter is used for excitation of the main generator field system. The control amplifier is excited by various superimposed signals and acts as a director to the whole control system.

This Koepe installation with its Ward-Leonard control presents a most favorable condition for the employment of automatic control equipment which 1 ad to a reduction in winding time and thus to an increase in the winding capacity.

Maximum independence of load and rapidity of control are important in the control of the winder. In the control system adopted, the rapidity of control action is attained using magnetic amplifiers adjusted for optimum performance. Although the magnetic amplifier is slower in response than the electronic amplifier, nevertheless it has a distinct advantage for this installation, because if its sturdiness and immunity to aging. The magnetic amplifiers concerned control a direct current obtained from a reference voltage generator while drawing their energy from an alternating current source. When the on setters button is pushed, the full reference voltage is applied to the accelerating magnetic amplifier. This opposes the bias voltage and potential is transmitted to the control magnetic amplifier.

The rate of acceleration is controlled by feeding back the LR. drop developed across the compensating pole winding in the driving motor. This is applied to the control magnetic amplifier in opposition to the output of the accelerating magnetic amplifier.

The speed attained is controlled by the potential developed by the generator (voltage proportional to speed) being fed back to the accelerating magnetic amplifier in opposition to the reference voltage; thus, the speed of the winder is proportional to the applied reference voltage.

Retardation of the winder is controlled by means of the retardation controller, which reduces the reference voltage by means of magnetic switches on the spiral controller.

The direction of travel is governed by the polarity of the reference voltage. The magnetic amplifying system is duplicated for reverse, and the control magnetic amplifier excites one or other of the two fields in the exciter generator, which are in opposite direction electrically. Thus, the polarity output to the generator field is reversed, depending on the polarity of the reference voltage. Provision is made to limit the current taken by the motors by an applied potential taken from the terminals of the auxiliary windings of the motors to a current limiting amplifier. The output voltage of this amplifier applied to the control amplifier is zero below a certain given value of current in the generator circuit. Above this value, the signal furnished to the control amplifier is preponderated over those in the other regulating circuits.

The Koepe wheel

The winder is designed to haul a payload of 20 tons from a depth of 5 000 feet at a speed of 3 000 feet per minute. The Koepe wheel is 19 feet 6 in diameter. It is manufactured in two halves and is of all-welded construction and has a total weight of 70 tons. Contrary to normal winder design practice, this diameter was not dictated by the consideration of rope bending ratio or tread pressure. It was designed to be the same as the distance between the centers of the compartments served by the Koepe hoist. By using a wheel having this diameter it was possible to dispense with deflection sheaves for the head ropes and all their attendant complications. Furthermore, because the centers of the compartments are 19 feet 6 in apart, a large loop is possible for the tail ropes. This leads to simplifications at the bottom of the shaft since it was not necessary to use sheaves for the tail ropes.

The Koepe wheel was designed after exhaustive tests had been carried out on a 1/5th full-size scale model of the wheel to determine stress levels under various loading conditions. These tests were deemed necessary at the commencement of design since both theoretical and practical results on other Koepe winders used in this country had not proved entirely satisfactory.

The friction material used for the rope treads is a locally made product consisting of hard rubber blocks of 80 Shore hardness, secured to the drum barrel face by wedge-shaped aluminum blocks. This tread has proved satisfactory to date and present results indicate that extremely long tread life can be expected. Tests have shown that the material possesses a high coefficient so that the possibility of rope slip occurring under emergency conditions may be regarded as minimal.

The Koepe wheel is fitted with two brake paths, one on each side of the treads. The caliper-type brake shoes are actuated by independent brake engines.

A section of the periphery of the Koepe wheel is shown in Fig. 30.

Tread trueing device

Because no compensating gear is provided where the ropes are attached to the bridle it is essential that all the tread grooves on the Koepe wheel be kept to the same diameter. A tread trueing device has been incorporated in the design to serve this purpose and may be used during winding operations whenever necessary. The device takes the form of a pneumatically operated, rotary, formed cutting tool which is mounted on a slide rest that allows both lateral and longitudinal movement. It is situated below the Koepe wheel and is set with the point of the tool on the centerline of the drum shaft as shown in Fig. 31. So far it has not been necessary to use the device.

The winder bearings

The total weight of the head ropes, the skips, the tail ropes, and a single payload is approximately 220 tons. The weight of the Koepe wheel is 70 tons, that of the drum shaft is 30 tons, while each armature of the two direct overhung driving motors weighs 25 tons. This too tall load of 370 tons is carried on two lain self-aligning 30 in diameter by 48 in long white metal bearings. Each bearing thus carries about 185 tons. The advantage of having only two bearings is that the problem of alignment is minimized and the arrangement of the foundation in the engine room is simplified. The layout of the winder is shown in Fig 32. Lubrication of the main bearings is by a gravity feed from an overhead tank which can be filled by pumps. Oil rings are also provided to circulate the oil from the reservoirs in the bearing pedestals.

Hydraulic lifting gear

In view of the heavy loads that must be handled should the main bearings require adjustment or replacement, two 200-ton capacity hydraulic jacks are provided to raise and support the drum shaft. These Jacks are situated at each end of the drum shaft, between the main bearing and the motor armature as shown in Figs. 32. and 33. Each ram has a stroke of 2 in and is used to raise the cradle under the shaft. On either side of the jack are steeled support columns which position the cradle. When raised, the cradle can be supported by putting packing pieces between the cradle and the columns. The base plate of the assembly is fixed to the base plate of the main bearing. These devices have justified their inclusion in the winder design being both time savers and safe positive working tools.

Brake system

There are two separate brake assemblies, one on each side of the Koepe wheel, operating on brake paths integral with the shell and the outer wheel spiders. The brakes are of the caliper type actuated by brake engines which are mechanically independent but are interconnected hydraulically to operate together. The brake shoes are of the fully floating type pivoted at their center to the brake posts. The lower pivot for the brake posts is directly beneath the center of pressure in the brake shoe itself, thereby minimizing the servo effect and eliminating all tendency to judder or rumble when the brakes are applied fiercely.

The brake engines are illustrated in Fig. 34. The braking force is derived from many helical springs held in compression. The force exerted by the springs is relieved by a hydraulic piston located in the cylinder at the lower end of the brake engine assembly. The braking force applied is thus inversely proportional to the oil pressure beneath the piston. This pressure is controlled by a pressure follow up servo mechanism located beneath the driver's platform in such a way that the braking force is proportional to the position of the driver's level. Oil under pressure is supplied to the brake engines from an air/oil accumulator.

In the event of an emergency the emergency control center, which can be seen in the lower left-hand side of Fig. 34 takes over control of the braking and is arranged so that it causes the braking force to build upper a pre-set pattern. This pattern has been chosen so that smooth retardation will take place under all winding conditions, the rate of the application is increased as the conveyances approach the terminal points of the wind.

A feature of the braking system is that the driver's control remains available for brake application even after an emergency trip has occurred. To warn the driver and to prevent him from overriding the automatic brake graded application in emergencies, a "feel device" is incorporated in the driver's control lever linkage. This is used to increase the effort required to move the brake lever towards the "on" position whenever the automatic emergency braking pattern is being exceeded.

The brakes can be applied by three different means, namely-

(a) The driver's brake lever for normal braking;

(b) Automatic operation solenoid valves for automatic braking; or

(c) A push-button for emergency braking.

 The helical retarding controller

The purpose of the helical retardation controller is to obtain accurate and constant control of the rate of retardation irrespective of any variation of loading. This is of importance when the winder is operating under semi-automatic conditions. The design of the controller is shown in Fig. 35. It has a fixed shaft in the center on which is a helical thread of rectangular section. There is also an external fixed helical rig having the same pitch as the center thread. The rig represents the shaft, to a reduced scale. Its peripheral length is approximately 65 feet. On the rig are mounted several magnets operated relays in suitable positions (see Fig. 36). A carriage mounted on rollers and holding a permanent magnet is rotated around the center thread guided by two vertical rods which are driven from the winder drum shaft. As this carriage rotates it follows a spiral path, the pitch of which is the same as the external fixed helical rig. The carriage represents a conveyance. In traveling along with the helical rig, it represents, to a reduced scale, the travel of the conveyance through the shaft. The relays mounted on the helical rig represent points in the shaft. The relays are operated by the magnet mounted on the carriage and initiate signals for well-defined and unchanging positions of the conveyance in the shaft. The relays can be moved along the helical rig for easy adjustment. Additional signals can be obtained by adding relays at the required positions and precise accuracy is attained. 

The controller eliminates the use of relays mounted in the shaft and operated by conveyance. These require constant maintenance and are always a source of trouble. 

Great accuracy is required in the automatic control of the retardation of the winder. The retardation gear operates effectively through the stepped resistances used in the circuits which regulate the speed of the winder, in this case, the excitation circuit of the Ward Leonard generator. The retardation gear operates in parallel with the driver's master controller on the Same control apparatus and consequently ensures automatic retardation of the winder, even if the driver's lever is kept in its "ON" position.

The retardation controller can be used for another signaling, interlocking or control purposes relative to the position of the conveyance in the shaft, such as:

(i) tripping the winder in case of an overrun of the conveyance,

(ii) controlling the change of the mechanical braking torque or its speed of application.

(iii) controlling the rope creep compensation equipment, or

(iv) preventing the restart of the winder in the wrong direction.

Operation of the retarding gear

In automatic operation, the winder is started by push-button and is stopped by the magnetic switches of the helical controller. The winder accelerates at a rate defined by the setting of the magnetic amplifiers up to full speed (Point A). The setting can be adjusted by means of sliding resistances. Full speed is maintained constant to the beginning of the retardation period (Point B), irrespective of load. The retardation gear automatically controls the decrease of the speed reference down to the "creep speed" value and the winder retards to creep speed (Point C) at a rate defined by the magnetic amplifiers. The winder completes the cycle at creep to point D where it is stopped by the application of the mechanical brake, the speed reference being simultaneously reduced to zero. In manual operation, the winder is controlled by the combined control brake lever of the driver.

During retardation, the first relay of the retardation gear is actuated by the carriage mounted magnet and the speed reference is reduced from "full speed" down to "90 percent of full speed" (See Fig. 37). The winder, therefore, retards automatically at the rate defined by magnetic amplifiers down to 90 percent of the full speed. Successive relays are actuated until the speed reference is reduced to creep speed in ten steps. Provided the control circuits correctly answer the signals received from the retardation mechanism and that the moving carriage of the latter is always synchronized with the position of the conveyance in the shaft, the winder performance will match the preferred speed/time diagram.

In Fig. 37 the retardation is shown as a stepped line which is, in fact, the theoretical speed/time curve followed by the conveyance under the control of the retardation gear signals. If the safety circuit is tripped but the main power and regulation circuits are still available when the conveyance is within the retardation zone, the action of the retardation gear is short-circuited. The speed reference is immediately reduced to zero and the winder retards at the rate defined by the amplifiers, i.e. at a rate greater than that followed in normal operation but which is inherently safe.

Supervisory and protection units incorporated in the retarding gear

Speed supervisory units are incorporated in the retardation gear equipment to ensure that the winder correctly retards on receipt of the signals transmitted by the helical controller.

The Ardic controller

The Ardic controller supervises the retardation of the winder only and throughout this period shadows the helical controller by a cam and follower system. If the winder fails to respond to the signal initiated by a relay of the helical controller, does not retard and is thus running at overspeed, the Ardic controller trips the safety circuit and the winder must retard at a rate defined by the magnetic amplifiers and come to rest.

Rope creep compensators

Because of possible slip or creep of the rope on the Koepe wheel or because the diameter over the treads is reduced owing to wear of the friction treads, synchronism between the travel of the conveyance and movement of the carriage of the helical controller may be altered. To remedy this, the helical controller and the Ardic Controller are driven from the main shaft of the winder through a servo-motor-operated differential gearbox. This allows for automatic compensation "after each cycle should the rope slip or creep and brings both control units into step with the monitored conveyance.

If rope slippage occurs causing the helical controller carriage to be in advance of the conveyance being raised, when the conveyance reaches the "tip" position in the headgear, the carriage will have overrun its "tip" position. Only after the brakes have been applied and the hoist is at rest, does the carriage through a relay initiate a circuit which causes the differential gear servo-motor to move in the direction to return the retardation mechanism to its correct " tip" position. Only on completion of this operation can hoisting proceed.

If rope creepage occurs causing the conveyance to be in advance of the carriage when the conveyance reaches the" tip" position in the headgear, the carriage will not yet have reached its" tip" position. Once again after the hoist is at rest the differential gear servo-motor is moved to bring the carriage into step with the conveyance in the headgear "tip" position.

To compensate for a reduction in the diameter of the tread, the gear ratio between the helical controller and the main winder shaft must be changed. This is easily done because a positively infinitely variable gearbox is incorporated in the drive.

Tachogenerators

A tachogenerator is fitted at each end of the drum shaft and is driven mechanically from the same shaft that drives the helical controller or the Ardic controller. These generators feed a D.C. circuit in which is a relay that trips on low current. By this means, full supervision of the mechanical drives and the abovementioned controllers is achieved.

The engine room crane

The crane in the engine room, although not a part of the winder itself, is an essential feature of the installation. It consists of the main crane unit of 35 long ton capacity and an auxiliary crane of 5-ton capacity. The former is designed to lift heavy loads outside the headgear from ground level to the engine room floor or to lift loads in the engine room. It was used for the erection of the winder and is invaluable for the maintenance of the winder. In addition, it can be used for handling the winding ropes in the compartments of the shaft. The 5-ton crane unit, which is smaller and faster than the main crane, can be used to advantage during the normal operations of rope changing and for general handling of tools and material.

A feature of these crane units is that they each have two control panels. One control panel is situated on the ground level, the other is in the engine room. Control can be diverted from one point to the other as required by means of a change over switch.

CONCLUSION

Since it was commissioned in March 1965, this Koepe winder has operated satisfactorily for the hoisting of mineral and has augmented the capacity of the shaft considerably. The two main winders at ground level are fully occupied handling the material and men necessary to serve the growing underground complex, while the Koepe winder handles all the ore from the lowest loading place in the shaft.

The maximum daily hoisting schedule for the Koepe winder is approximately 22 hours. At present, the average daily hoisting time is 18 hours. The remaining time per day is occupied by compulsory examinations, unavoidable delays or unexpected shaft accidents. Despite these delays, the winder has been able to hoist an average of 224000 tons of ore per month (See Fig. 38.) If optimum performance is attained 300 000 tons of ore per month could be brought to the surface.

ACKNOWLEDGMENT

Thanks, are due to the Manager, Western Areas Gold Mining Company Limited, and to the Consulting Mechanical and Electrical Engineer of the Johannesburg Consolidated Investment Company Limited, for agreeing to the publication of this paper.

DISCUSSION

Mr. D. W. Chambers (Visitor): The author has covered the subject thoroughly and the following comments are an indication of the considerable amount of planning and organizing necessary to bring about the successful commissioning of this Koepe winder.

The facilities available for the handling of the equipment can be described as an erection engineer's dream because the use of the 35-ton overhead crane operating over the engine room hatchway enabled even the heaviest lifts to be lifted directly from the road motor vehicles on the bank to the engine room without requiring any 'double' handling.

The erection crew experienced some difficulties and brief delays while leveling and aligning the winder due to vibrations transmitted in the headgear structure when the bank mounted rock hoist was handling the rock. The final leveling and alignment were carried out when this hoist was being used for man/material handling or when it was stationary. A further problem in leveling was brought about by the variation in the expansion of the headgear structure caused by the movement of the sun in its path from east to west. However, the erection crew was favored by a period of not less than six days of dull overcast skies and during this period it was possible to complete the operation successfully. The two-bearing design for the main drum shaft simplified the leveling and alignment operations.

The provision of hydraulic nuts with pre-stressed bolts on the drum halves and rigid couplings, proved to be of considerable advantage in both accessibility and accuracy of tightness because the oil pressure gauge provided an instant direct reading enabling the precise pre-stress loading on each of the main bolts to be obtained. The use of hydraulic nuts is an obvious advantage in the design because the associated bolts can be in positions that would normally be inaccessible if standard bolts and nuts were used.

After the erection of the main shaft, the Koepe drum, and the two motors, the complete assembly was dynamically balanced.

Mr. I. D. Tudhope (Visitor): I was interested in the shaft layout adopted wherein all rock hoisting is now undertaken by the Koepe winder, using the two outer compartments in the shaft. I have often heard it said that this arrangement complicates both the loading and unloading layout and that the complication is increased where it is necessary to differentiate between waste and ore during hoisting operations. In this case, it is apparent that the Mining Company intended from the beginning to use the outer compartments and I would be interested to hear Mr. Armstrong's comments on the experience which has been gained with this layout. Are these loading arrangements more expensive in the first cost and do they require more maintenance attention than would be the case with the more conventional arrangement where the two skips operate in adjacent compartments?

The Koepe wheel design was verified by tests carried out on a one-fifth full-size scale model of the wheel. Initially, the winder design was prepared from theoretical principles and the model constructed in accordance with this preliminary design. To eliminate the effect of unsatisfactory welding from the analysis, the model was machined from solid, so that all junctions, which in practice would be welded, were homogeneous in the model. The model was then placed in a rig where it could be artificially loaded to simulate the stresses imposed by the winding ropes and by the mechanical brakes (see Figs. 39 and 40). To determine the direction of principal stresses, particularly the stresses which appear in the side, plates, use was made of a brittle lacquer which cracks when the steel on which it is painted is stressed. The cracks appear at right angles to the direction of the principal stresses. This technique enabled the designers to gain considerable insight into the nature of the stresses generated in the wheel structure and resulted in there being able to place strain gauges on the model where they would be of greatest use, that is in regions which were' highly stressed or where reversing stresses were anticipated.

The model was then exhaustively tested, using the strain gauges to measure the stresses occurring because of a) rope loads only, b) the wheel rotating, c) the action of the mechanical brakes, and d) any combination of these loads. Several empirical design criteria were established and it is gratifying to note that little modification to the initial design concept was felt necessary before the wheel was put into production. During production, considerable care was taken to ensure that all welding was carried out to the highest standards and that the surface finish of welds was sufficiently smooth to avoid-causing concentrations of stress in any part of the structure.

The author comments that the rubber rope treads have behaved well so far, that no recourse has been necessary to the use of the trueing device and that life expectancy of the existing treads appears to be good. It may be of interest to provide a little more detail on the treads themselves.

The treads are moulded in blocks each of which is 36 inches long. These blocks, as moulded, are straight and are bent to suit the periphery of the Koepe wheel during installation. The material used is rubber with a hardness of 80-850 Shore. The blocks are moulded with a pre-formed rope groove in the upper surface and a corresponding, though smaller, a groove in the under surface. The latter groove has seen found by experience on other mines to be instrumental in promoting even wear of the rope tread groove, which tends to wear into a cusp if the under-surface groove is omitted. This is probably since the rubber behaves as an incompressible fluid and the lower groove permits the block to adjust itself to the changing pattern of stress resulting from the rope loads.

The circumferential surface of the wheel on which the rope treads bear was machined to provide them with an even and firm supporting base. This also accounts for it being unnecessary to true the rope grooves after installing the block. Small circular rods were welded on to this surface in a transverse direction to engage with transverse grooves moulded into the lower face of the rope tread blocks. The purpose of these rods or keys is to minimize the creeping of the tread block against the drum surface.

During the design of the Koepe winder, considerable thought was given to the effect of possible unbalanced magnetic pulls emanating from the large direct-coupled motors. It will be appreciated that these large D.C. machines can generate quite considerable transverse loads if the armature is not centrally disposed within the magnetic field system. Therefore, considerable care was taken to ensure that the winder drum shaft was stiff enough to resist the worst unbalanced pulls which could be generated and in addition great care was taken during the setting up of the winder to ensure -

(a) that clearances in the bearings were small enough to contain movement within set limits,

(b) that the outer surface of the armatures ran as true as possible, and

(c) that the air gaps in the motors were as even as possible around the periphery.

The armatures were first mounted on the drum shaft in the winding engine chamber. By packing the spigots with shims, it was possible to adjust the armature run-out to a minimum. The final setting was such that the outer surface of the 140-inch diameter armature had a run-out not exceeding 0.003 inches. To enable the flanges of the couplings to be bolted together using fitted bolts, the bolt holes were reamed after the final and best armature setting had been obtained. A modified motor-car type cylinder boring machine was used for this purpose. The coupling bolts were then finished to a size to suit the finished bored hole.

The duty cycle for the winder includes three-quarters of an hour a day for examination, while the drum winders at the same shaft require approximately half an hour. Theoretically, therefore, it might be possible to operate the Koepe winder for 23t hours a day and a drum winder for 23t hours a day provided both were being used for hoisting from one level only and did not require to be stopped for shift changes. Does Mr. Armstrong feel that this is a true reflection of the service availability of the Koepe winder when compared with the drum winder, bearing in mind that a Koepe installation requires considerably more time in the way of examination of head ropes, tail ropes and for adjustment to rope tensions?

Mr. E. J. Wainwright (Associate Member): The winding plant described has proved to be one of the most successful of the deep level Koepe winding plants insofar as the ropes are concerned. The first set of head ropes was discarded at the end of January 1967, having pulled approximately 25 0000 skips (5 000 000 tons). The ropes had been regularly electro-magnetically tested and it appeared that the final deterioration was rapid. The future life expectancy should be about 230 000 to 240 000 skips. Just before the ropes were discarded it was discovered during an electro-magnetic test, that one of the ropes had developed an "hourglass" failure (i.e. the inner strands of the rope had failed, see Figs. 41 and 42, there is no wire failures in the outer strands). This point of maximum deterioration occurred in No. 3 rope at a position about 20 feet past the winding drum when the skip nearest it was in the tip.

Compared with other deep level Koepe winding plants the life of the ropes has been excellent and the following factors which may have influenced this life should be considered:

(a) Depth: this is one of the major factors affecting the life of Koepe winder head ropes. It has two effects, one being an increase in the twisting of the ropes with depth and the other the increase in the total weight of rope in the system, which increases the maximum static load range acting on the rope, with an increase in depth. The winding depth of various deep level Koepe winders is as follows:

Stilfontein, Margaret Shaft = 4439 ft.

Western Areas = 4917 ft.

West Driefontein, No.5 Shaft = 5618 ft.

Western Deep Levels No.2 and No.3 Shafts = 6320 ft.

(b) Absence of deflecting sheaves: This has undoubtedly influenced the rate of deterioration and it is of interest to note that the region of maximum deterioration of the rope occurred at the position where deflecting sheaves would normally be installed.

(c) The ratio of drum rope diameter and tread pressure: The ratio of the drum to rope diameter which is 117 to 1 is like that of other Koepe winders and has been dictated by rope size and the geometry of the shaft layout. This has resulted in a tread pressure 225 lbf/in2 (c.f. Western Deep Levels at 276 Ibf/in2, No. 5 Shaft, West Driefontein at 257 lbf/in2 and Stilfontein at 212 lbl/in2).

(d) The factor of safety: Although the factor of safety of 7.16 seems to be rather high, this figure was arrived at by considering the range of load change in the rope. The maximum static load range was increased by 15 percent to allow for dynamic effects and the total limited to 13 percent of the breaking strength of the rope.

(e) Dynamic loading on ropes: In view of the satisfactory behavior of the head ropes it was decided to carry out dynamic tests on the winder to establish the magnitude of the dynamic forces and to assess the extent to which the load is shared by each rope. These tests, carried out by the Mine Equipment Research Unit of the National Mechanical Engineering Research Institute of the C.S.LR., indicated that the maximum dynamic forces increased the load range by 25 percent.

(f) Equalizing gear: Although. no rope load compensators are provided on the winder, tests indicate that the load sharing of the ropes is satisfactory. The maximum variation between the lowest and highest loaded rope being 4000 lbf.

(g) Rope design: The ropes used are a modified version of the 15 strands "Fishback" ropes used at Western Deep Levels, West Driefontein and Stilfontein. These ropes of the "Fishback" design have 12 outer strands instead of 9. This has improved the non-spinning properties; the C factor (or torque to end load proportionality factor) being reduced from 0.124 in to 0.090 in for a 2 in diameter rope.

In the writer's opinion, the factors which have had the most influence on the life of these head ropes are those which have tended to reduce the dynamic loading to a minimum, the high factor of safety and the adequate non-spinning property of the ropes.

Mr. A. H. Gyngell (Associate Member): The basic concept of this shaft layout has made it possible to use a friction winder without deflection sheaves and with a low tread pressure and a large tail rope loop. These are the most desirable qualities and have not all been met at the same time by any previous 4-rope Koepe installation in this country. There are several cases in Canada where the skip compartments are separated by a ladderway and this produces the necessary spacing to achieve the same result although on a much smaller scale.

The use of direct-coupled twin overhung D.C. motors adds further to the simplicity and consequently to the reliability of this outstandingly successful installation.

The description of the friction arrestors was of interest because a similar installation was designed and installed on the sub-vertical friction winders at Western Deep Levels, Limited. Falling weight tests like those described by the author were conducted at Western Deep Levels. While the frictional drag produced by a single buffer stop varied between 7000 lb and 14000 lb depending on the state of the rails it was apparent that the buffer stop could form the basis of a simple and practical arrestor. Fortunately, or unfortunately depending on one's viewpoint, the Western Deep Levels sub-vertical arrestors have not been required to operate on a serious overwind. It is therefore of great interest and comforting to hear that the installation described in the paper has survived an overwind at considerable speed without serious consequences.

The author mentions a rotating cutting tool for trueing the rubber rope treads but admits that it has not been necessary to use it yet. A similar device driven by an air motor was tried at Western Deep Levels and proved useless, the tool becoming blunt in a short time. A satisfactory tool faced with the coarse abrasive paper of the type used for sanding floors has been found to be much superior.

The elimination of lever-type suspension gear has contributed to the extremely favorable payload/skip weight ratio of 1.02. At Western Deep Levels and at Vaal Reefs where lever-type compensators are in use, this ratio is only 0.85, partly because of the compensators and partly because of the stronger bridle for the greater depth of the shaft. It is advisable to 'retain the levers at these mines because they provide a good indication of the incipient failure of a head rope.

It would be interesting to hear from the author what life has been obtained from the head ropes and tail: ropes. At Western Deep Levels and at Vaal Reefs the pattern of headrope deterioration is consistent and is concentrated within a zone about 150 feet from each capel. Within this zone, extensively broken wires appear in the inner strands. These breaks are generally detectable in time by the D.C. electro-magnetic test.

Mr. G. A. P. Low (Member): My contribution is limited to a few general observations.

Equalizing gear

The decision to dispense with rope tension equalizing gear was based, amongst others, on the following considerations:

(a) Any material differences in groove diameters are not permissible, for well-known reasons. A tried trueing device was therefore built into the drum set to ensure that any possible differences could be dealt with as they occurred.

(b) The slight differences in average rope diameters are unlikely to lead to other than negligible differences in tension.

(c) The hoisting ropes, in general, respond elastically to safe loadings, e.g. a 2 in rope 5 000 feet long is extended some 4 feet by a 10-ton increase in load, i.e. by an increase equivalent to 5 percent of its breaking load. Yet the arrangement of cappels illustrated in the paper allows a 6 in the difference in length at 5000 feet to be easily observed and adjusted, i.e. differences of the tension of about 2 ton or 1 percent of the breaking load can be corrected. Greater accuracy seems unnecessary.

Tail rope loop

Fig. 43 shows the shape of the loop in the tail rope at different speeds, i.e. a catenary when stationary and the "bell-shape" it assumes under acceleration Hoist due to centrifugal force at nearly full speed. There occurs an inherent cyclic disturbance of the shape of the loop during every normal trip and further disturbances occur after tripping or other reason. If the Rope characteristic loop shape is known beforehand, the design can easily be adapted to dispense with the rollers M.G. altogether, so that the tail ropes will never touch anything under any but abnormal circumstances. The rollers are merely a precautionary measure and in any case, turn only at low hoisting speeds. Moreover, if the stiffness of the rope can be adjusted by different constructions to fall naturally into a circle of diameter approximately equal to that of the drum groove, cyclic disturbances can be further reduced.

Arrestor gear

It should be noted that the design of the arrestor gear is such that the arresting forces merely compress the beams supporting the hoist, without increasing bending moments.

Slip

To test for slippage of the ropes on the wheel, the hoist was repeatedly tripped when running at full speed with uncontrolled braking. No-slip whatsoever was observed.

Availability

The following table gives the availability for the hoisting of the equipment during the first two years of operation. The availability can be improved considerably if necessary. Some 6 500 000 tons have been hoisted since the winding plant was commissioned until the middle of August 1967.

Mr. K. A. MacMillan (Member): The installation of an M.G. set at ground level involves a considerable cost in copper conductors from the ground to the hoist mounted above the headgear. Could the author give an idea of the cost involved?

A large amount of money has been spent in providing for retarders and jack catches, not the least of which is because of the increased height of the headgear. This equipment is of doubtful value when the momentum of moving loads is considered. In one installation hoisting a 20-ton payload from 4500 feet (here referred to as hoist B), and which has been hoisting 3 480 000 tons a year since 1960, no such gear is provided. Reliance is placed on overwind protection, followed by shadow protection, followed by relative-position protection. The shadow devices have the added advantage of being actuated independently of the other two devices, i.e. they are not operated by the same driving spindle. The same driving spindle. The idea of using friction blocks does, however, seem to be an economical method for retardation compared with hydraulic retarders. They may be a tendency for them to seize over a period.

The layout using a large diameter tail loop is apparently an advantage, together with the obvious advantage of efficient spillage deflectors. Could the author confirm that the rollers at the shaft bottom have operated in a trouble-free manner?

In the case of hoist B, the exemption was granted from the Mines and Works regulation to enable all attachments and bridles to be kept in use for twelve months before removal and overhaul. No trouble has been experienced because of the extended period of use.

The author mentions that "no gear for equalizing tension" is provided. This probably relates to attachment gear. For deep shafts, no such gear which is of much use has yet been devised. If simple levers are used at one end of the head ropes, they do give a good visual indication of uneven rope stretch. Unequal tensions in headropes during running can be due to (a) unequal rope lengths, which is easily corrected, and (b) unequal rope diameters or unequal thread diameters, which can be offset by using elastic treads, e.g. rubber. In the case of hoist B, the treads are never machined or "trued because this appears to be a "waste of time, even when one head rope is changed at a time, and tread life is equivalent to 17 000 000 tons hoisted.

The changing of one headrope only does ensure that there are always one or two new ropes in use. A headrope can be changed in 6 hours, a tail rope in 4 hours and a bridle in 11 hours (two bridles are changed every twelve months) so that rope replacement is much more convenient and easy than is the case with drum winders.

The author mentions jacking up during bridle changing. We have found it quicker to lift ropes in the opposite compartment by using the hoist drum. We contend that the changing of tail ropes is easier and faster when done at the shaft bottom station.

Adequate interlocks for loading at the loading station, as described, are necessary because of the danger of possible damage to the tail ropes. Fixed volume loading does not appear to be satisfactory, weight measurement being a more accurate method because of the changing ore from time to time.

The following table gives a comparison of headrope performance for the two hoists: -

An interesting point with a tower-mounted Koepe hoist arises when bedding-in the main bearings. The jacking gear must be designed to clear brake components so that the brakes can be released and the drum shaft rocked, to get bedding marks, without disconnecting the ropes and conveyances.

It has been stated by some authorities that a Koepe should be referred to as a hoist and not a winder. The latter term apparently refers to drum winders wheel reel in or coil the rope. This is, of course, a matter of opinion.

AUTHOR'S REPLY TO DISCUSSION

In Reply to Mr. I. D. Tudhope

Fig. 21 in the paper indicates a general arrangement of the underground loading arrangements. Fig. 44 clarifies the arrangement. The outer Koepe compartments and the adjacent initial rock winding compartments are shown as being fed from the same side at the shaft, via a small capacity transfer ore pass, from a twin belt conveyor system above.

The transfer ore pass has a capacity of about 100 tons which is equal to 5 Koepe skips or about 10 skips serving the inner compartments. From experience, this has proved to be a flexible and practical arrangement, since the ore handling equipment is in duplicate, but controlled from one point underground. The transfer ore pass could conceivably become a bottle-neck to the system, but due to its small capacity, this is not often experienced. It also allows for quick clearance of ore or waste as required.

The hoisted ore or waste is unloaded into its respective small capacity bin in the headgear structure and is transferred to a belt conveyor for further treatment or disposal. The headgear bin is small to allow for speedy clearance of ore or waste so that change. Over can be effected with a minimum loss of time. An electrical system is used to notify the hoist driver and the banksman on duty, whether ore or waste is to be hoisted. The movable carriage mounted on rails below ore and waste chutes, feeding the twin belt conveyors, contacts a switch in either Position to initiate a signal to the control on the Surface. A similar signal is transmitted from the headgear unloading Positions of ore and Waste. In this case, the headgear bin traverser is used to contact a Suitably situated switch.

The initial cost of the arrangement was made than would be the case where two skips operate in adjacent compartments. The excavation to accommodate the proposed 20 ton measuring bins serving the outer compartments was larger, and, with the belt tunnel for two 42 in belt conveyors had to be completed as part of the Sinking programme; the 20 ton measuring bins and the second 42 in belt conveyor were installed coincident with the Koepe hoist only one belt conveyor Was required to serve the initial rock hoisting arrangements. Under the present conditions, maintenance of the loading arrangement is like that required for a loading arrangement in adjacent compartments.

The service availability of the Koepe hoist is approximately 22 hours. Fig. 38 was intended as a typical diagram only, the words "shift change" being substituted for time lost. In fact, hoist drivers, banksmen and onsetters hand over duties to their reliefs at v their respective posts, whether the hoist is in manual or automatic Control and no time is lost. Exemption from the relevant Section of the Mines and Works Act permits inspection and maintenance of the hoist, rape, conveyances, headgear, and shaft to be done on a Sunday if necessary.

In Reply to Mr. A. H. Gyngell

The First Set of head ropes Was discarded after being 22 months in service. They had hoisted approximately 250 000 skips or 5000 000 tons of rock. The second set is still in use. The average life of the tail rope was introduced for the second set in. hoisted. A slight modification in the construction of the tail rape was introduced for the second Set in. stalled. The modified tail rapes are in service now and it will be interesting to compare results.

In Reply to Mr. K. A. MacMillan

Since the M.G. set of the hoist installation was ground-mounted, eight major cables had to be carried to the hoist situated above the headgear. Several smaller cables followed the same route for control purposes. The cost of these conductors was approximately R12 000.

The shaft bottom rollers are constructed as follows: a 3 in dia. x 9 feet 0 in long mild steel shaft is securely fixed by dead eyes at each end to the 16 in x 6 in R.S.J. columns as shown in Fig. 46. The total length of the roller is 80 in, made up of eight separate rollers each 10 in long and 12in in diameter which is covered with It in thick rubber. Each roller has two sealed tapered roller bearings and can rotate independently of the next. The inner sleeve of the roller is fixed to the shaft by locking screws. Weekly maintenance and Inspection of the rollers are necessary. As each roller wears it may be repositioned along the shaft or removed for overhaul and replaced by a new or reconditioned roller.

Roller wear occurs mostly during the acceleration period of the hoist when the tail rope loop tends to distort slightly and move away from the centerline of the compartment in which the skip is being hoisted. When full speed is attained, the loop tends to balloon slightly so that no contact is made with the rollers during this period. Excessive wear on the corners of the rollers has been minimized by the installation of the second set of rollers 12 in below the first set. These have two special 15 in wide sections in the outer positions, thus staggering the sides of the individual rollers which were vulnerable wear points of the units. See Fig. 47. This double unit arrangement has proved satisfactory.

The term Koepe hoist does seem to be correct when referring to the machine, for the reason stated.