Mine Ventilation Survey and Fan Commissioning Project

This project builds a commissioning package for an underground mine ventilation fan and its connected district. The deliverable is not a fan nameplate check. It is a measured airflow, pressure, power, leakage, monitoring, and interlock evidence package that supports an operating release decision.

The project is written for engineering education. Real mine ventilation work must follow the approved ventilation plan, legal requirements, site trigger-action response plan, competent-person signoff, calibrated instruments, worker exposure controls, electrical rules, and emergency procedures.

The engineering objective is:

Commission the installed fan and district ventilation controls so that required air quantities reach the intended mine branches, measured evidence agrees within tolerance, fan power is acceptable, and the operating mode is safe to release.

Project Scope

The reviewed installation serves a new underground production district. It includes a main fan, starter, variable-speed drive, pressure taps, fixed airflow station, regulators, doors, stoppings, branch measurement stations, gas monitors, and a supervisory control system.

The commissioning package must produce:

1. an airflow survey table;
2. a pressure and fan-power check;
3. a leakage and balance reconciliation;
4. instrument calibration and cross-check evidence;
5. regulator and door correction actions;
6. interlock and alarm proof-test records;
7. an acceptance matrix with release decision and residual limits.

Design Basis

The simplified commissioning basis is:

Item	Value or criterion
minimum total fan-station airflow	95\ \text{m}^3/\text{s}
North production district minimum	30\ \text{m}^3/\text{s}
South development district minimum	22\ \text{m}^3/\text{s}
pump chamber and workshop minimum	14\ \text{m}^3/\text{s}
refuge and escapeway minimum	10\ \text{m}^3/\text{s}
controlled bypass and leakage action limit	15\ \text{m}^3/\text{s}
air-balance residual action limit	8\% of fan-station flow
fixed station agreement with traverse	within \pm5\%
installed fan efficiency release criterion	at least 68\%
motor current release criterion	below 90\% of full-load current
critical ventilation interlocks	proof-tested before release

The values are project-specific examples. A real mine may require different branch quantities, exposure limits, heat-stress criteria, escape-route requirements, redundancy, alarm actions, or emergency ventilation modes.

Step 1: Fan-Station Airflow Traverse

The fan station has an effective measurement area:

A velocity traverse gives average velocity:

Volumetric airflow is:

This exceeds the minimum total airflow:

Mass flow, using air density:

is:

Engineering Comment

The fan station passes the total quantity screen, but that alone does not release the district. Air must reach the required branches, not only pass through a fan station.

Step 2: Branch Air Quantity Survey

The commissioning survey records:

Branch	Measured quantity	Minimum or limit	Result
North production district	31.0\ \text{m}^3/\text{s}	at least 30	marginal pass
South development district	24.0\ \text{m}^3/\text{s}	at least 22	pass
pump chamber and workshop	15.5\ \text{m}^3/\text{s}	at least 14	pass
refuge and escapeway	12.0\ \text{m}^3/\text{s}	at least 10	pass
controlled bypass and leakage	15.3\ \text{m}^3/\text{s}	at most 15	fail by 0.3

Useful branch flow is:

Measured branch and controlled bypass total:

Air-balance residual:

Residual percentage:

This is within the 8\% action limit.

Engineering Comment

The district is close but not ready for release. Total airflow is acceptable and the balance residual is credible, but controlled bypass and leakage exceed the action limit. The North district also has only a small margin above its minimum.

Step 3: Measurement Uncertainty and Guard Margin

For portable airflow traverse measurements, the commissioning team estimates:

Contribution	Standard uncertainty
velocity instrument and calibration	3\%
area measurement and obstruction correction	2\%
repeatability and traverse positioning	4\%

Combined relative standard uncertainty:

For the North district:

The measured margin above the 30\ \text{m}^3/\text{s} minimum is:

The margin is smaller than one standard uncertainty. The branch is not robustly released under the project guard rule. The regulator should be adjusted to add margin and the branch remeasured.

Engineering Comment

A number above the limit is not automatically good evidence. When the safety-critical margin is smaller than measurement uncertainty, the commissioning record should either improve the measurement confidence or adjust the system to create operational margin.

Step 4: Fan Pressure and Power Check

The measured fan pressure rise is:

Air power is:

Electrical input power from the power meter is:

Installed fan, motor, and drive efficiency is:

or:

This passes the 68\% release criterion.

Specific fan power:

Engineering Comment

The fan is operating plausibly. The efficiency screen does not prove that every branch is correct, but it helps detect gross installation problems such as excessive system resistance, wrong rotation, inlet obstruction, damaged blades, or a measurement inconsistency.

Step 5: Electrical Loading

The motor full-load current is:

Measured current during the loaded commissioning run is:

Fraction of full-load current:

This is below the 90\% release criterion.

Engineering Comment

Electrical loading should be checked with ventilation demand, fan curve, motor protection, cable rating, starter settings, and restart conditions. A fan can pass airflow but still fail commissioning if the electrical system has poor margin or trips during a ventilation-critical mode.

Step 6: Fixed Station Cross-Check

The fixed airflow station reports:

Traverse airflow is:

Difference:

Relative error against traverse:

This is within the \pm5\% cross-check criterion.

Engineering Comment

The fixed station can support routine monitoring, but the commissioning record should state its calibration date, installation condition, density assumption, signal scaling, and alarm setpoints. A fixed sensor is only useful if its number has a controlled measurement basis.

Step 7: Corrections Before Release

The team performs these corrections:

1. seals a damaged stopping near the bypass regulator;
2. adjusts the North district regulator to increase branch margin;
3. labels regulator positions and records locked settings;
4. verifies door-closed indication at two ventilation doors;
5. proof-tests fan-running permissive, low-flow alarm, and VSD fault alarm;
6. updates the ventilation model with measured branch resistance and leakage;
7. writes shift handover instructions for the released operating mode.

After correction, remeasurement gives:

Branch	Before correction	After correction	Criterion
North production district	31.0	33.2\ \text{m}^3/\text{s}	at least 30
South development district	24.0	23.5\ \text{m}^3/\text{s}	at least 22
pump chamber and workshop	15.5	15.1\ \text{m}^3/\text{s}	at least 14
refuge and escapeway	12.0	11.8\ \text{m}^3/\text{s}	at least 10
controlled bypass and leakage	15.3	11.4\ \text{m}^3/\text{s}	at most 15

The North district margin is now:

Its standard uncertainty is:

The corrected margin is greater than one standard uncertainty:

This satisfies the project guard rule.

Acceptance Matrix

Gate	Evidence	Result
Total fan airflow	Traverse result 104.4\ \text{m}^3/\text{s} versus 95\ \text{m}^3/\text{s} minimum	Pass
Branch quantities	All required branches pass after regulator correction	Pass
Bypass and leakage	Reduced from 15.3 to 11.4\ \text{m}^3/\text{s}	Pass
Air-balance residual	6.3\% before correction, within action limit	Pass
Fixed station agreement	-3.3\% against traverse	Pass
Fan installed efficiency	69.5\% versus 68\% minimum	Pass
Motor current	85.8\% of FLA versus 90\% limit	Pass
Critical interlocks	Fan-running, low-flow, VSD fault, and door indication proof-tested	Pass
Shift handover	Released mode, regulator settings, alarm actions, and recheck interval documented	Pass

Final Deliverable

The commissioning deliverable should include:

1. survey date, crew, instruments, calibration records, and operating mode;
2. fan-station traverse sheet and fixed-station cross-check;
3. branch airflow table before and after correction;
4. pressure, power, current, and efficiency calculations;
5. air-balance residual and leakage interpretation;
6. regulator, stopping, and door correction records;
7. interlock proof-test results and alarm response rules;
8. model update notes and residual uncertainties;
9. release decision with next survey interval and trigger conditions.

The commissioning recommendation is conditional release for the measured operating mode. The mine should re-survey if production headings advance, regulators are moved, doors or stoppings are repaired, fan speed changes, heat or contaminant sources change, or fixed monitoring drifts beyond the agreed tolerance.

Engineering Lessons

This project illustrates the difference between fan commissioning and ventilation release. A fan can move enough total air while branch distribution is still weak. A branch can read slightly above its minimum while measurement uncertainty makes the margin poor. A fixed station can look stable while regulator settings or door leakage change downstream conditions.

Useful ventilation commissioning connects:

1. measured airflow and pressure;
2. fan and electrical performance;
3. branch-level distribution;
4. leakage and bypass control;
5. sensor confidence;
6. interlocks and alarm actions;
7. operating-mode documentation.

The final engineering question is not whether the fan runs. It is whether the installed ventilation system delivers safe, measurable, and controllable air to the places where the mine plan depends on it.