Case Study – Thermography – Infrared Detects Advanced Electrical Relay Fault at Cement Mill

 

 

Background:

It is well known that the heat produced from high electrical resistance typically precedes electrical failures. For this reason, infrared scans are an essential measure for troubleshooting, diagnostics, and preventive maintenance in electrical power distribution applications.

Thermal imagers are most commonly used for inspecting the integrity of electrical systems because test procedures are non-contact and can be performed quickly with equipment in service. Comparing the thermal signature of a normally operating piece of equipment to the one being evaluated for abnormal conditions offers an excellent means of troubleshooting.

This case study is from a cement mill plant in Ireland, Europe. Since 2018, Eastway have completed electrical thermography surveys of the plant’s electrical installations on a six-monthly frequency. Since this time, Eastway have been working closely with the cement mill’s electrical maintenance crew to find, diagnose and repair any electrical faults in advance of failure.

Case Description:

During the January 2021 survey, dangerous heat was found in excess of 120 degrees Celcius in a relay. Smut and smoke residue could be seen on trunking and the relay connections overhead. This excessive temperature posed a fire risk which would have resulted in a health and safety risk and plant production shutdown. Three other relays identical to this were also found during the inspection.

Recommendation:

Replace all relays for contactors and check cables haven’t been damaged by excessive heat before re-terminating. Cables to be re-terminated in accordance with current electrical standards.

Action Taken:

Maintenance work was planned and executed by the site’s electrical maintenance team. This allowed for each of the four relays to be replaced for contactors with no loss of production to the plant. Detecting the faults in advance, enabling timely planning and sufficient lead time to order materials and have the correct tools on location.

Thus in addition to eliminating a significant fire risk, avoiding unplanned downtime the detection also significantly reducing the man hours to replace the relays.

Location

110v DB Room

Sub-location

Out Feeder

Equipment ID

Cement Mill 6 & 7

Equipment type

Relay D11

Identification

 

Measurements

Sp1

130.1 °C

 

Parameters

Object Emissivity

0.95

 

Analysis and Recommendations

Priority of Fault

Urgent

Fault description

Excessive heat was found at Sp1. Smut and smoke residue can be seen on trunking and relay connections overhead. Three other relays identical to this were also found during the inspection.

Recommendation

Replace all relays for contactors and check cables haven’t been damaged by excessive heat before re-terminating.

Results: Estimated* cost savings associated with avoidance of unplanned downtime, emergency repair costs & secondary damage:

Maintenance time saved: Approx. 3 hours
Downtime avoided: 16 hours
Downtime cost per hour €5,000
Total Savings: €80,000
Safety Incident Prevention: +++++