Big Dog Mining

Underground Shaft Hoisting Capacity

How long a hoist cycle takes, the skip payload your production needs, and what that asks of the rope and the motor.
Production skip hoisting up a vertical shaft only: one hoist, one compartment. It is not a hoist design, not a headframe or shaft-furnishing design, not a brake or duty-cycle calculation, and it does not size a cage for people. Hoisting is statutory ground: rope safety factors, speeds and accelerations are set by your regulator and your hoist engineer, not by this page.

Step 1: The hoist

Speed only helps if the shaft is deep enough to reach it.

Units ?

Source equations are metric. Imperial is converted.

Hoisting distance ?

Loading pocket to dump. Not shaft depth.

Maximum hoisting speed ?

Published range is 2 to 20 m/s.

m/s Load and dump time ?

Combined. About 20 s is typical.

Acceleration ?

Up to 1.2, typically 0.75.

m/s² Deceleration ?

Often equal to acceleration.

m/s²

Step 2: The production it has to carry

Payload is whatever the tonnage divided by the cycles leaves you.

Required annual production ?

Tons a year up this shaft.

t/y Available hoisting hours per year ?

After maintenance, people and materials. Set it honestly.

h/y Operating efficiency ?

Published average for hoists is 0.7.

Step 3: Skip and rope

Two books give two different skip tare rules. Both are here.

Skip tare rule ?

The two handbooks disagree. Pick one and see both.

Rope strength factor ?

Step 6 uses 8.5. Four to ten are common.

Rope construction ?

The three the handbook publishes. They run to different maximum sizes.

The rope is picked for you, and it is the smallest one that works. Step 7 of the published procedure says to select a rope with the required strength, so this page walks Table 12.23 in size order and takes the first that meets it. Step 8 then adds the weight of that rope hanging in the shaft and re-checks the safety factor, which is the check the rope's own weight can fail on a deep shaft.

Step 4: Checks

Published bands. Outside them you are past what the sources cover.

Quantity	Published range	Yours
Maximum hoisting speed typical published range	2 to 20 m/s	12.00
Acceleration as high as 1.2, typically 0.75	up to 1.2 m/s²	0.75
Deceleration as high as 1.2, typically 0.75	up to 1.2 m/s²	0.75
Rope safety factor four to ten are common	4 to 10	8.50

Speeds, accelerations and the 20 s load-and-dump time are all from SME Mining Reference Handbook 1st ed. p. 238. The handbook adds that mining laws and regulations may place their own limits on maximum accelerations and speeds, and those outrank anything here.

skip payload needed

hoist cycle time

motor power

Step	Value	Where it comes from

Where the cycle goes

What more speed buys

The published selection procedure

Step	What the handbook says	On this page
4	Use the required annual production and available hoisting times per year to calculate the skip payload.	done
5	Use the skip payload and a reasonable skip tare mass based on 70% of the skip payload to determine the total attached load.	done, and the competing Eq. 12.44 rule is offered beside it
6	Multiply the attached load by 8.5 to determine the required rope strength.	done
7	Select a rope with this strength.	done, from Table 12.23 p. 316: the smallest published size that meets it
8	Check that the rope strength also meets the required safety factor (typically 5) when the rope weight is added.	done, using that rope's published kg/m over the hoisting distance
9	Determine the drum diameter based on 80:1 drum-to-rope diameter.	done
10	Estimate the motor power using kW = (payload × speed)/102.	done
11	Estimate the inertia of the rotating parts based on historical data.	not done: needs the machine
12	Carry out a duty cycle calculation to verify the selection.	not done: needs the machine

SME Mining Engineering Handbook, selection procedure for production drum hoists, p. 1300. Steps 11 and 12 are inertia from historical data and a full duty-cycle calculation; both need the machine, not the shaft, and neither is attempted here.

For a Koepe or friction hoist the same page says the procedure is identical except that the number of ropes must be defined, four being a reasonable starting point, and that the conveyances must be heavy enough to keep the tension ratio between the loaded and empty sides below about 1.5. It also caps the coefficient of friction used in that calculation at 0.25, which it says is achievable even with wet ropes as long as they are not overlubricated. This page sizes a drum hoist and does not attempt the T₁/T₂ check.

The cycle time equation

SME Mining Reference Handbook 1st ed. p. 238, Equation 12.43 after Edwards 1992:

TC_H = (V_max/ACC) + (H/V_max) − [(V_max/2)(1/ACC + 1/RET)] + (V_max/RET) + T_dl

where TC_H is cycle time in seconds, H the hoisting distance, V_max the maximum speed, ACC and RET the acceleration and retardation, and T_dl the combined load and dump time. The printed note adds that for a single-skip system you get the time to lower the empty skip by excluding T_dl.

That equation is the ordinary trapezoidal speed profile written in one line, and it can be checked rather than trusted: accelerate to speed, run at speed, decelerate, add the load and dump. Worked both ways for an 800 m lift at 12 m/s and 0.75 m/s², the equation and the physics agree to the millisecond, which is a stronger statement about the transcription than any number-matching could make.

What this tool does not know. It sizes the duty, not the machine. It does not calculate the inertia of the rotating parts, does not run the duty cycle that verifies the motor and the brakes, and does not check rope life, sheave sizing, headframe clearance, rope stretch or the harmonic behavior of the flight rope, all of which the handbook treats at length. It assumes a single skip in balanced hoisting and does not model a counterweight, a clutched double drum, or hoisting from several levels. It says nothing about people or materials movement, which competes for the same shaft. Every published value has been checked against the printed page.

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Worked example

Worked with the values this page loads with, so the method can be checked against the cited source without entering anything. Change any input above and the calculator recomputes; the numbers below stay as a fixed reference case.

13.58 t
102.7 s
1598 kW

Hoisting distance	800 m	your input
Maximum speed	12.00 m/s	your input; published range 2 to 20 m/s
Distance to reach speed and stop	192 m	V²/2ACC + V²/2RET; must fit in the shaft
Accelerate to speed	16.0 s	Eq. 12.43 p. 238
+ run and decelerate	66.7 s	Eq. 12.43 p. 238
+ load and dump	20.0 s	your input; about 20 s is typical, p. 238
= hoist cycle time	102.7 s	Eq. 12.43 p. 238
= cycles per hour	35.1	3,600 ÷ cycle time
Annual production	2000000 t/y	your input
÷ available hoisting hours	6000 h/y	your input
× operating efficiency	× 0.70	published average for hoists is 0.7, p. 238
= skip payload	13.58 t	step 4, selection procedure p. 1300
Skip tare, 70% rule	9.51 t	step 5, selection procedure p. 1300
Skip tare, Eq. 12.44	7.47 t	0.5 × payload + 680 kg, p. 238
= tare in use	9.51 t	the 70% rule
= total attached load	23.09 t	payload + tare, step 5
× rope strength factor	× 8.5	step 6 uses 8.5, selection procedure p. 1300
= required rope strength	196.23 t force	step 6, selection procedure p. 1300
= smallest rope that meets it	54 mm	step 7; 18 × 7 Independent Wire Rope Core Sinking (round), Table 12.23 p. 316
its published strength	197.25 t force	Table 12.23 p. 316
its weight over 800 m	9.75 t	12.19 kg/m × 800 m, Table 12.23
= safety factor with rope weight	6.01	step 8; strength ÷ (attached load + rope weight)
= drum diameter at 80:1	4.32 m	step 9 on the selected rope, selection procedure p. 1300
= motor power	1598 kW	payload kg × 12.00 m/s ÷ 102, step 10, selection procedure p. 1300
= hoisting capacity	333 t/h	payload × cycles per hour × efficiency

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Estimating aid only. This is not an engineering design and not a substitute for the judgment of a competent or qualified person. Verify every result against the cited source and your own site conditions. Full terms and disclaimer.