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(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
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
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).