(اسکیپ یا قفس)طراحی ترابری در چاه 1. Surface plant

a. Hoist room (headframe- or ground-mounted)

(1) Hoist drum or sheave (imparts motion to rope)

(2) Hoist electrical and mechanical equipment (prime mover, brake, clutch,

controls)

(3) Hoist ropes (steel wire strands, woven in a pattern or lay)

b. Headframe (tower or A-frame, steel or reinforced concrete)

(1) Idler sheaves

(2) Storage bins (ore and waste)

(3) Skip dump mechanism (overturning or bottom dump)

2. Shaft plant

a. Skips (bulk transport)

b. Cages, elevators (ore and waste)

c. Shaft guides (tracks for ships and cages)

3. Underground plant

a. Dump and storage bin

b. Crusher (if size reduction required for hoisting)

c. Loading pocket

d. Personnel and materials-handling facilities

(اسکیپ یا قفس)طراحی ترابری در چاه

Single-drum hoist Double-drum hoist Friction (Koepe) hoist Blair-multi rope hoist

(اسکیپ یا قفس)طراحی ترابری در چاه

Spiral drum Conical drum

Drum Hoists

The maximum desirable speed for a double-drum hoist

with fixed steel guides in the shaft is 18m/s (3,600 fpm).

The maximum desirable speed for a drum hoist with

wood guides in the shaft is 12m/s (2,400 fpm).

Optimum Speed (fpm) = 44H½ , where H is in feet

Or, Optimum Speed (m/s) = 0.405 H ½ , where H is in

meters

rule of thumb formula

Assuming reasonable values for acceleration gives the

following rule of thumb equations for the design speed

of drum hoists, in which H is the hoisting distance

(feet).

Design Speed (fpm) = 34 H ½ , hoisting distance less

than 1,500 feet

Design Speed (fpm) = 47 H ½ , hoisting distance more

than 1,500 feet

Drum Hoists

The hoist wheel rotation at full speed should not exceed 75

revolutions per minute (RPM) for a geared drive, nor 100-

RPM for a direct drive.

For a skip hoist, the acceleration to full speed should not

exceed 1.0m/s2 (3.3 fps2). For a hoist transporting persons, it

should not exceed 0.8m/s2 (2.5 fps2) as a matter of comfort to

the passengers.

Drum Hoists

With proper maintenance planning, a drum hoist should be

available 19 hours per day for a surface installation, 18 for an

internal shaft (winze). فرانسوی دساندری و واژه آلمانی گزنگ

A drum hoist is available for production for 120 hours per

week.

This assumes the hoist is manned 24 hours per day, 7 days

per week, and that muck is available for hoisting.

The total operating time scheduled during planning stages

should not exceed 70% of the total operating time available,

that is 16.8 hours per day of twenty-four hours.

Drum Hoists

The pitch distance on drum winders (hoists) should be

between 5.5% and 7% larger than the nominal rope

diameter.

Drum Hoists

The flanges on hoist drums must project either twice the

rope diameter or 2 inches (whichever is greater) beyond

the last layer of rope.

At installation, the allowable out-of-level tolerance for the

main shaft of a drum hoist is one thousandth of an inch

per foot of length.

Drum Hoists

The overwind distance required for a drum hoist is one foot

for every hundred fpm of hoist line speed.

The overwind distance required for a drum hoist is 1.6 feet

for every hundred fpm (1m for every 1m/s) of hoist

line speed, to a maximum of 10m.

The overwind distance required for a high-speed drum hoist

is 7m.

The underwind distance required is normally equal to ½ the

overwind distance.

Drum Hoists

Power consumption (energy portion of utility billing) of a

drum hoist is approximately 75% of root mean square

(RMS) power equivalent.

In calculating the RMS horsepower requirements of a drum

hoist, it is not important to determine a precise value

for the inertia. A 10% error in inertia results in a 2% error in

the RMS horsepower.

For a DC hoist motor, the peak power should not exceed

2.1 times the RMS power for good commutation.

For a DC hoist motor, the peak power should not exceed

2.0 times the rated motor power for good commutation.

Drum Hoists

• The easy way to design a drum hoist is to

first determine

the required hoisting speed and payload,

Then determine

the rope that is needed to meet the SF.

The hoist parameters can then all be determined only

considering the hoist rope and line speed.

Drum Hoists

• For purposes of initial design, the hoist line speed should

be 40% of the highest speed that is theoretically obtainable

over the hoisting distance (even though the most economic

speed is 50%).

This value leaves room to increase the speed at some

future date to as high as 60% without seriously

compromising power costs.

Drum Hoists

• The statutory minimum

drum diameter to rope diameter

Ratios

• Where guidelines indicate an 80:1 drum to rope ratio, it

may be reduced to 72:1 at hoisting speeds up to 2,000

fpm (10m/s) without significant loss of rope life when

employing stranded wire ropes on drum hoists.

For speeds exceeding 3,000 fpm (15m/s), the minimum

drum diameter to rope diameter ratio is 96:1.

At this minimum, the head sheave diameter to rope

diameter ratio may be increased to 120:1 as an

inexpensive means to help maintain good rope life.

Drum Hoists

• The overwind distance is normally first calculated for

the minimum statutory requirement and then increased if

required to meet good engineering practice.

• For deep shafts, the overwind distance calculated must

include an allowance for less turns of the hoist drum that

result from hoisting an empty skip.

Hoist controllers don’t know where the conveyance is;

they precisely track the revolutions of the hoist drum.

Drum Hoists

A modern hoist with automatic compensation of the rope

stretch and variations in drum diameter does not require

an overwind allowance related to hoisting an empty skip.

The inertia of the drive motor rotor must be multiplied by

the square of the gear ratio for the effect at drum radius.

Drum Hoists

An easy way to obtain an accurate value for the RMS

horsepower of a counterweight hoisting system (round

trip) from a computer program designed for balanced

skip hoisting (one-way trip) is by making two runs.

The first run hoists the full payload and the second

hoists the counterweight while lowering the empty

conveyance.

The RMS horsepower for the round trip may then be

obtained from averaging the heating values:

RMS HP = [(HP12 + HP2

2)/2]½

Drum Hoists

An easy way to obtain a value for

the RMS horsepower of a double-drum

sinking hoist from a computer program designed for

balanced skip hoisting is to substitute the sums of the

stop and creep times in the sinking cycle for those of the

skipping cycle.

Drum Hoists

The RMS horsepower calculation is not always the

criteria for selecting the drive for a drum hoist

installation.

When hoisting single from a deep horizon (or balanced

hoisting from great depths), if the peak horsepower

exceeds the RMS by a wide margin, the peak

horsepower may be the basis for selecting the size of

the hoist drive.

Drum Hoists

In the selection of a suitable motor for any hoist, the

peak demand, RMS demand, and creep speed

demand should be considered.

Also, selection should be based on torque rather than

power.

Drum Hoists

Fleet angle: Drum Hoists

For drum hoists, fleet angles of 1 in 45 (1o 16’) or 1 in 50

(1o 9’) are desirable.

The fleet angle for drum hoists should not exceed 1o 30’.

In mine-shaft hoisting, the maximum fleet angle should

be as close as possible to 1o 20’.

Excessive drum wear and poor spooling will result if this

angle is exceeded.

Ideally, the fleet angle should not exceed 1o 15’.

Some line scrubbing will occur in the zone between this

angle and 1o 30’, but at a wider angle the rope may pull

away from the flange or jump at high speed.

The maximum fleet angle should not exceed 2o.

Drum Hoists

For large hoist installations, vibration analysis is likely to

reveal that to avoid excessive rope whip, a drum hoist

should be closer to the headframe than the traditional

maximum desirable fleet angle will allow.

In such a case, it may be considered that selection of

the appropriate rope lay (right hand or left hand), a wide

pitch distance for the rope grooves, and the installation

of a miscoil detection device may permit employment of

a wider fleet angle than the limits once thought to be

necessary.

A minimum fleet angle of 30’ for a drum hoist will ensure

that the rope will cross back and start a new layer

without piling.

Drum Hoists

Creep Times:

The creep times for skip hoisting applications is usually

taken as equal to 5 seconds at the beginning and 5

seconds at the end of the wind (“creep out” and “creep

in”). For deep shafts, the creep out can be omitted, but

the creep in is typically increased to 15 or even 20

seconds for high-speed hoisting from deep shafts, to

provide an extra safety margin. For cage hoisting, the

creep out can be omitted, but the creep in may be

increased to 10 seconds to allow for spotting the deck.

The sum of the creep in times for shaft sinking in North

America with a double-drum hoist may be taken as 65

seconds, and for creep out it

totals about 40 seconds.

Drum Hoists

Drum Hoists: Hoist Cycle Time “T” Typical shaft skip hoisting in balance T = H/V + 35 (manual)

Typical shaft skip hoisting in balance T = H/V + 40 (automatic)

Deep shaft skip hoisting in balance T = H/V + 45 (automatic)

Shaft sinking in balance T = H/V + 165 (North America)

Shaft sinking in balance T = H/V + 135 (South Africa*)

Small cage and counterweight hoisting T = 2H/V + 100 (round trip)

Large cage and counterweight hoisting T = 2H/V + 130 (round trip)

Single drum shaft sinking (North America) T = 2H/V + 215 (round trip)

* South African shaft sinkers employ a creep speed higher than 2

feet/second.

Note At installations where skips are

hoisted on rope guides, the

cycle time may have to be

modified to account for slow

down at the ends of travel

required for the transition from

rope guides to fixed guides. An

entry speed of 300 fpm

(1.5m/s) is considered

desirable although there are

installations that have been

carefully engineered to permit

a faster transition speed (as

high as 1,100 fpm).

Maximum Line Speeds for Drum Hoists

Maximum Line Speeds for Drum Hoists

Drum Hoists: Example and its solution: