CONVEYOR BELT MONITORING

There will always be incidents that trigger conveyor belt failures. Unplanned conveyor downtimes are often a catastrophic and very costly result, that must be avoided. Hence, good belt scanning is highly advisable, well, even a must.

 

Steel cords as such are susceptible to corrosion. Depending on their rubber filling degree, water or humidity may get into a cord when the conveyor belt was damaged, and then spread throughout the cord like in a drinking straw, unnoticed from the outside. In extreme cases, sometimes, invisible corrosion pockets grow several hundred meters away from the damage.

 

Below are short descriptions of the main types of monitoring.

VISUAL INSPECTION

Used for

Belt damages that may have injured the carcass, detecting protruding steel cords.

Working principle

A well-trained person is watching the belt running at creep speed.

Remarks

Works only at low speed. Carcass damages without external injuries are hard to detect.

X-RAY (PORTABLE CAMERA)

Used for

Detection of carcass damage.

Working principle

X-ray shots/photographs

Remarks

Excellent resolution.

Covers small areas only.

Suitable for spot check only.

TRANSMITTER-RECEIVER SYSTEM

Used for

Detection of cover injuries and damages of steel-cords.

Working principle

Site attenuation; decrease of an electric field by electrically conducting materials (the steel-cords).

Remarks

Even small cracks can be detected.

No real-time monitoring.

LEAKAGE FIELD MEASUREMENT

Used for

Detection of abrupt changes of the steel-cord cross-section.

Working principle

Leakage field measurement

Remarks

Can be used for speeds of up to 6 m/s.

No belt vibration allowed.

Quality of analysis depending on software and personal experience.

MAGNETIC RESISTANCE

Used for

Inspection of steel cord conveyor belts right after the production or at certain intervals during the operating time.

Working principle

The steel cords are inductively magnetized (before that they have to be demagnetized).

Remarks

No permanent monitoring.

Complicated analysis, vague interpretation.

OPTO-ELECTRONIC IMAGING

Used for

Recording the belt surface condition.

Working principle

Camera systems, laser

Remarks

Limited results under dirty conditions.

Belt carcass/steel cords not captured.

X-RAY (STATIONARY, CONTINUOUS)

Used for

Detection of cover and carcass damages, splice deterioration, wear, insufficient cleaning, ripping, foreign objects, material build-up, steel cord failures etc.

Working principle

Permanent X-ray recording of moving belt with image recognition technologies. Permanent and full cross-section X-ray recording.

Remarks

Excellent resolution, detection of any failure, real-time analyses, remote access, automatic reporting.

A comparison between continuous X-ray and magnetic based systems is here

PREVENTIVE MAINTENANCE

A four-part article published in Coal Age magazine, May 2016, elucidates the need for preventive maintenance:

 

The PM program should successfully avoid premature failures through timely inspection, condition-monitoring and testing. It should help extend equipment life with lubrication, cleaning, adjustment and minor component replacements like belts and filters. By avoiding premature failures, there will be fewer emergency repairs and more work can be planned because equipment deficiencies will be found long before failure, creating opportunities to plan the work. Because the resulting planned work is jointly scheduled with operations, it will be performed more productively and carefully by maintenance personnel, whose work will be of higher quality. Higher quality work increases the time needed before the work must be repeated. As a result, components will have a longer operating life and additional cost savings will be realized by reducing the rate of material consumption.