2 Major Components of Hoisting System w Shaft - a near vertical hole in ground through which things can be raised and lowered w Head-frame - Steel structure over hole used for lining up conveyance and directing cables w Conveyance - That container for batch movement of cargo - name varies with application
3 Support Features for Conveyance w Since Hoist is a batch movement process needs loading and unloading features w Shaft features a loading pocket for material transfer quickly to conveyance w Usually a surge bin or ore pass to hold ore and smooth surges in production with need to keep hoist running steadily w Headframe usually has dump pocket to side to quickly catch discharge from conveyance
4 Rope Handling Features w Conveyance moved by ropes or cables w Headframe has rope handling and aligning facilities w Often have a large Sheath or Wheel at top that redirects the cable w May be a storage drum for rope to one side or sometimes at top of headframe w May have hoist house on top of frame
5 Typical Hoisting System
6 Two Major Types of Shafts w Inclined Shaft Not Common today Steeper than decline In the wall haulage systems in open pits May follow vein in small scale metal mine to limit development to vein w Vertical Shaft Boring Technologies up to medium sized Large still need conventional sinking
7 Uses for Hoisting Systems w Man Cages - Haul men and supply w Utility Hoists - Mostly for supply handling w Emergency Hoists - often in small shaft to get few people out in emergency w Production Hoists Will be focus of this unit Used for removing pay product
8 Application Hoist Influences what is raised and lowered w When men and supplies are handled usually called a cage some may be multi-level w Production Handling - Called Skips w Skips need way to get material in and out
9 Skip Configurations w Solid and open at top need special equipment to dump w Open at top - bottom opens still need to be unload without dumping load down the shaft w Side discharge - high production open off to side of top side opens for easy discharge to dumping pocket
10 Types of Hoists w Drum Hoist rope is stored on drum w Keope Hoist rope just passes over wheel at top of headframe must have a balancing load on other side rope just sits over wheel and is held by friction obviously some limits on how hard can accelerate this
11 Drum Hoist Configurations w Simple Single Drum Hoist drum with rope wrapped around it w Just lowers the skip to anyplace in range of rope w Inherently out of balance - big load down shaft when at extension w Out balance makes slow and suitable for only limited depth w Easily serves multiple levels
12 Hoist Rope Drive Assemblies
13 Drum Hoist Configurations w Double Drum Hoist Two ropes wound in opposite directions Stick a load on each rope Creates a balance load - lower something when pulling something up - less energy and strain - can hit greater depth w May put a counter weight on one side - can then go to any level w May put two skips in balance - but now can only serve one level and expect skips to line up right.
14 Drum Hoist Arrangements w Double Drum with separated drums - one clutched w Functions like double drum except that now can shorten one rope to allow multilevel service Usually won’t do unless need to have two in balance skips w Splitting drum and adding clutch increase inertia and cost w Runs short distances out of balance
15 Drum Hoist Types w Double Drum Divided Both Sides Clutched w Adding still more inertia and cost w Can adjust for multi-level hoisting but could do that with just one drum clutched w Usually done for man hoists - need to be sure that something will be able to run if it has to
16 Weird and Wonderful Drum Tricks w Simple drum is a cylinder problem is want to start hard - but theres lot of inertia and tremendous torc w Conical Drum leverage to spin up to speed Size can get scary fast w Cylindro-Conical cylinder for starting rope - then flatten out to cone w Bycylindro-Conical often creep away from load pocket and then hit it
17 Keope (or Friction) Hoist w Has to hoist in balance w Control on inertia No large rope storage drums No rope wrapped around everything w Generally less costly w Not as Quick as Drum - can’t peel out the friction on the wheel w Sometimes have to put extra tare load to keep the balance w How in the heck are we going to serve multiple levels?
18 The Multilevel Problem for Keope Hoists w If just one level don’t care w Can do a skip and counter weight and serve multi-levels if your willing to cut your production in half w Can use multiple wheels each wheel has a skip and counter weight if two levels can try to skip pairs (not at all common)
19 Choosing Between Drum and Keope w Limited depth favors Drum Hoists Rope Storage is less scarey Peppy acceleration boosts production w Multi-level favors Drum Hoist (but Keope can play too) w Greater Depth favors Keope below about 3,000 feet drums usually can’t compete Keope can do well on very shallow too
20 Rope Handling Comparisons w Keope Hoist Often uses several ropes on one skip The ropes bend in parallel so no differential twisting Multi-rope helps explain greater service depth Multi-rope gives more friction surface area w Drum Hoist has to be single rope to avoid pile-up and differential bending ever increasing rope size forces ever large drum to avoid hard twist on rope
The Mystery of the Tail Rope 21 Why would I leave a rope hanging down A shaft? Wire rope is very heavy and can be a big Part of the load.
Consider a Keope Hoist 22 Balanced loads on each side are important to prevent sliding Over the sheave wheel. What is out of balance here? The load in one of the scoops A big length of rope
Now What is Out of Balance? 23 The load in one of the skips Even though drum hoists don’t have the slipping issue The unbalanced load is what the hoist motor has to work Against – unbalance is bad here too.