Hoists, cost

The number, duration and complexity of the tasks necessary to fully rebuild a used hoist are frequently underestimated. Table 1 provides a listing of some of the refurbishment tasks and their relative costs as a percent of the total hoist cost. Figure 1 shows a modern production facility for new hoists, where parts tracking and assembly are tightly controlled. Figure 2 show parts as received for an overhaul project. The part identification was not ideal and led to assembly problems and cost overruns. The most cost effective time to repair a hoist is during the refurbishment phase so it is critical to ensure that necessary rework is identified and completed prior to rebuilding the hoist Once the hoist has been rebuilt and installed, repairs become extremely expensive. 

The author surveyed a niunber of projects in the mining industry a cost comparison was made of the total costs of the used hoist after refurbishment relative to a new hoist cost. It was found... 

Let us assume that extra labor costs money. It is not free like the help given by David, Nancy, and Daniel. Then, all the above proposals to reduce the time it takes to change a tire cost money. If the use of a jack or hoist is to be avoided, more labor must be hired. If a hydraulic jack or power wrench is to be used, it must be purchased or rented. Finally, the remounting of the spare tire means spending extra money and effort in advance of the project. 

If some distance separates the plants and the pre-concentration plant is situated nearer to the ore hoisting shaft or open pit then ore transport costs can be reduced significantly. 

Industrial starches are supplied to the paper mill in packages or bulk containers.9 The shipment of starch as a suspension in water is possible, but it is costly due to the need to transport about 65% water. Starch settles easily, is difficult to resuspend, and can easily spoil. Bags are shipped stacked in layers on pallets. Super sacks, which hold about 1000 kg starch, have lifting straps for handling them with forklift trucks or overhead hoists. The sacks are fitted with an outlet sleeve. 

Materials-handling cost for chutes, conveyors, gates, and hoists are given in Figs. 14-89 through 14-95. In addition, Table 7 lists costs for materials-handling equipment by automotive means. 

Hoisting equipment. Extra costs include acid-resistant construction, S340 dust-tight construction,... 

Tubular heat exchangers appear to have zero exponents, implyinig feftt direct labor cost is independent of size. This reflects the fact that s h equipment is set with cranes and hoists, which, when adequately sized for the task, recognize no appreciable difference in size of weight of the equipment. The higher labor exponent for installing carbon-steel towers indicates the increasing complexity of tower internals (trays, downcomers, etc.) as tower diameter increases. 

The series motor is used where frequent starts under load are necessary as for traction, and hoisting. Speeds increase as loads (torques) decrease and the motor may run away if the load is entirely removed (as by breakage). Power output remains about constant over a wide range of speeds efficiency is constant for a wide speed range but a narrow power range. Full-load efficiencies vary in about the same way as those for shunt motors, but the maximum is about 3 per cent lower. Five hundred-volt series motors weigh 30 to 60 lb. per horsepower. Costs per pound are about constant for sizes from 50 to 200 hp. 

Economic comparisons and detailed investigations into the cost of operating all these various types of hoists and cranes cannot well be made here, but an analytical consideration of the more complicated type, the overhead cranes, will serve to demonstrate approved methods for arriving at such data. 

Miscellaneous Cranes.— Wall and jib cranes, whether stationary or of the traveling type, hoists of various kinds and all other varieties of cranes lend themselves to economic selection and analyses as to probable net cost of operation along lines very similar to those followed in the case of overhead electric cranes. A full knowledge of operating requirements is necessary, suitable provisions should be made for possible expansion, and the mistake avoided of assuming too great a mechanical efficiency for the equipment. An intimate knowledge of costs— labor and equipment—and depreciation expenses is also required for even such approximate estimates, if they are to be at all reliable. 

A recent innovative machine-room-less traction elevator (ISIS) from ThyssenKrupp takes full advantage of the properties of p-aramid in the design of the hoist cable and associated traction sheaves [130-133]. The cable has three times the life of a steel rope, is smaller in size, and weighs 90% less than a steel rope at a comparable strength rating. The smaller size permits the use of smaller sheaves thereby decreasing torque requirements and operating costs. No lubrication is required because the inner strands are Teflon coated. Finally, the cable transmits less noise and provides a smoother, quieter ride. 

Hoists for medium lift, heavy duty with push trolley, multiple disc brakes including motor and drive. FOB cost = 16000 for lifting capacity = 2.6 Mg with n = 0.36 for the range 4.5-26 and n = 1.48 for the range 26-45. For motor driven trolley X 1.6. 

Hoists for long hft with motor driven trolley, cab or floor controlled, variable speed, mechanical or electric load braking, double reeving, single or twin load hooks, overload relays, AC current. FOB cost = 40000 for lifting capacity = 3 Mg with n = 0.82 for the range 2-20. For DC current X 1.05. L-tM = 1.5. L/M = 0.22. 

Solid bowl, disc, intermittent nozzle dischai e c/s with motor drive, sludge pumps, sludge cake conveying and hoists for waste water sludge dewatering. Installed module cost, PM cost = 1 600000 for a dry solids capacity of 1 Mg/h with n = 0.78 for the range 0.2-8 Mg/h. 

Due to the recent market demands for SIL 3 mine hoist brake systems some manufacturers (including the manufacturer that the author works for) are embarking on the development of SIL 3 brake systems. This is a costly and complex endeavor involving more than just the technical design of a mine hoist brake system and the oft quoted ideas of eager sales people to take... 

The relative cost of disc brakes verses driun brakes will be discussed for the various hoist applications. 

Ultimately with steel ropes, a practical limit of shaft depth occurs where the steel rope is not able to hoist an economically satisfactory payload. At this point to achieve the desired production rate, either additional parallel hoisting plants must be installed, or the hoisting distance split into two or more separate shafts. Either option results in increased capital costs for construction and increased maintenance and operating costs for the additional infrastructure and equipment. 

A Koepe hoist requires balance ropes to balance the weight of the headropes in order to maintain an acceptable tension ( T1/T2 ) ratio. The total weight of balance ropes normally equals the total weight of headropes. This additional set of ropes results in increased capital, operating and maintenance costs. Balance rope designs have been optimized to minimize... 

Balance ropes may not behave satisfactorily in very deep shafts, due perhaps to the dynamic behavior of the ropes causing tangling of the rope loops at shaft bottom or other unforeseen problems. In some mining jurisdictions it has been common practice to employ sheaves at the shaft bottom to control the balance rope loops, and the deepest existing Koepe hoist installations employ these balance rope sheaves. This adds additional costs and complexity and may not be of any value. Simulations or tests may be required to identify any problems with balance ropes for deep shafts. 

Due to the balance between hoist and balance ropes, Koepe hoists require significantly less torque compared with a drum hoist of similar capacity. This results in reduced capital costs due to smaller motors and drive systems, and reduced operating costs due to power consumption. 

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