Thermal Imaging Inspection of Auxiliary Equipment at CHP Plants, Mining and Metallurgical Sites

Overheating is a universal symptom of a problem: poor contact, overload, a worn bearing, a clogged heat exchanger. Thermal imaging inspection (infrared thermography) lets you see anomalies from a distance, without shutting down the unit and without removing covers — provided there's a direct line of sight to the surface.

For the auxiliary equipment fleet at metallurgical plants, mining sites and CHP plants, thermography is one of the fastest mass-screening methods: in a single shift you can survey dozens of motors, switchgear cells and pump units. Suspect points flagged by ΔT are then confirmed with SDT340 ultrasound on the bearing or partial-discharge detection in the switchgear — thermography sets priority, not a final diagnosis.

What gets inspected on auxiliary systems

Electrical connections

• terminal boxes on 4–200 kW motors;
• contactors and breakers in pump and fan control panels;
• busbar connections in CHP switchgear;
• connectors on variable frequency drives at conveyor sites.

Defect signature: localized overheating of a contact point, 5–50°C above neighboring phases under the same load.

Bearing assemblies

• bearing housings on pumps, fans, gearboxes;
• comparison of symmetric DE/NDE points on the motor.

Defect signature: one-sided heating — overload, insufficient lubrication, seizing, misalignment. Thermography doesn't distinguish the cause, but it prioritizes which units mechanics need to visit first.

Mechanical and thermal systems

• fouled air coolers and hydraulic system radiators;
• uneven heating of heat exchangers;
• steam leaks through insulation (given sufficient ΔT);
• overheated belt drives (where visible).

Standards and evaluation criteria

A relative ΔT criterion is used — the temperature difference between the monitored point and a reference (neighboring phase, symmetric bearing, ambient air):

Object	ΔT, guideline	Action
Terminal box contact	> 10°C vs. phase	Scheduled tightening
Terminal box contact	> 20°C	Urgent repair
Pump bearing	> 15°C vs. symmetric point	Diagnostics, lubrication, alignment
Bearing	> 25°C or > 90°C absolute	Shut down if possible
Switchgear busbar	> 15°C vs. adjacent section	Tightening, cleaning

Absolute temperatures depend on insulation class, load and season — which is why trend and relative difference matter more than a single snapshot.

Conditions for a quality inspection

• Load — at least 40% of rated capacity; defects in contacts may not show up at idle.
• Emissivity — accurate readings need the emissivity coefficient ε set correctly in the camera for the surface material.
• Shooting angle — perpendicular or up to 60°; a sharp angle distorts the reading.
• Comparability — images taken at the same points, from the same distance, to overlay the trend.

A protocol with the thermal image, date, load and unit ID is the foundation for CMMS records and insurance disputes after a switchgear fire.

Inspection frequency

Equipment class	Interval
6–10 kV CHP switchgear, main pumps with no standby	3–6 months
Class A auxiliary motors	6 months
Remaining fleet	12 months
After startup following a major overhaul	Unscheduled, after 48 hours of operation

At mining sites, dust on VFD radiators in summer raises operating temperature — a seasonal inspection before peak load reduces drive failures.

Typical field findings

A loose phase in the terminal box of a CHP condensate pump — ΔT of 18°C, a 20-minute tightening, an arc fault averted.

An overheated DE bearing on a mining conveyor — misalignment after a coupling replacement; resolved together with laser alignment.

A fouled cooler on a crusher hydraulic station — uniform oil overheating; flushed without disassembling the hydraulic system.

Overheated gearbox on a metallurgical agitator — an unscheduled oil analysis revealed rising Fe content; the oil was changed and the gear teeth inspected on schedule.

Limitations of the method

Thermography does not replace:

• oil analysis — early-stage internal gear wear with no external heating;
• balancing — imbalance can persist for a long time without causing critical overheating;
• alignment — bearing overheating is the consequence, not the elimination, of the root cause.

What it does offer is fast coverage, and it pairs well with the other three methods in a comprehensive PdM program.

Economics

A thermal camera pays for itself by preventing a single fire in a cable compartment or an emergency shutdown of a pump with no standby unit. Surveying 100 motors in a day is a realistic plan for two engineers with an IR camera and a checklist.

KEG TRK doesn't supply standalone thermal cameras, but covers part of this need with other instruments: SDT340 already has a built-in infrared thermometer for spot-checking a component right within the ultrasound route, and wireless I-care Wi-care sensors track unit temperature continuously, without IR-camera walk-downs.

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