Underground Auxiliary Ventilation
How much air a development heading needs, what it costs in pressure to push
that down a duct, and what the fan burns in electricity to do it.
Auxiliary ventilation of a single dead-end heading only — one fan, one
duct, one face. It is not a mine ventilation network model, it does not balance a circuit or
solve for splits, it is not a heat or refrigeration calculation, and it is not a gas monitoring
plan. Statutory airflow is set by your regulator and your ventilation officer, not by this page.
Step 1 — The heading
The opening sets the velocity you can get away with.
Step 2 — What has to be diluted
Diesel almost always sets the number. Velocity limits then check it.
Step 3 — The duct
Diameter is the whole game. Resistance goes as area cubed.
Step 4 — Running it
Air power goes as the cube of airflow. Doubling the air costs eight times.
| Step | Value | Where it comes from |
|---|
The heading and the duct
Where the pressure goes
Friction factors, by what the air is running through
| Type of airway or ducting | Friction factor k, kg/m³ |
|---|
SME Mining Engineering Handbook, Table 15.3-1, p. 1579,
from McPherson 1993, referred to an air density of 1.2 kg/m³. Only the ventilation ducting
rows drive this page; the airway rows are shown because an auxiliary duct discharges into an
airway and it is worth seeing what the same air costs in each.
This table came back flagged as “rows 37 vs claimed 32”. Rendering p. 1579 and
counting settles it: 32 data rows plus five section headings is 37, and all 37 were transcribed.
The count was the model disagreeing with itself, not a row going missing.
What a bend costs in straight duct
| Source of loss | Equivalent length, m | ft |
|---|
SME Mining Reference Handbook, 2nd ed., equivalent lengths
for vent pipe and tubing, p. 362. Published in both metres and feet, and the two agree across
every row, which is a check a transcription cannot pass by accident.
The printed note on entrance and exit is load-bearing and is a question this page asks you
rather than assuming: they are counted only if the fan is not located at the point of
loss. Values given as a multiple of D scale with your duct diameter, and the sharp
against smooth distinction is the bend centreline radius: 0.75D is sharp, 1.25D is smooth.
Velocity and dilution limits
| Area | Maximum velocity, m/s |
|---|
SME Mining Engineering Handbook, Table 15.3-2, p. 1590. The same page gives a commonly applied minimum of 0.3 m/s after McPherson 1993, and both ends are checked here.
| Location | Diesel airflow requirement | Comments |
|---|
SME Mining Engineering Handbook, Table 15.3-3, p. 1590,
after Brake and Nixon 2008. These are regulatory numbers, not physics, which is why they differ
so much between jurisdictions and why some publish none at all.
Manitoba is quoted on a different basis and this page will not let you use it as a
simple multiplier. Its 0.92 m³/s per kW is more than ten times every other
jurisdiction on the list, and the printed comment says why: it “uses 100/75/50
rule”, which apportions the rated power of multiple machines rather than summing it. The
number is faithfully what the page prints. It is not comparable to the others.
Spending more time on spreadsheets than on the job?
We build the reporting and admin automation for mining contractors, so the numbers keep themselves.
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