Article by Chris Clifford
WHEN IS HOT TOO HOT?
Geo Therm’s Tony Dale discusses the use of thermal imaging to mitigate yacht outages and fire
Electricity is one utility that we all take for granted, and immediately miss whenever an outage or blackout aoccurs. Dead in the water is a cliché that is thankfully underused, much thanks to the pool of talent of the engineering crew and shore based support within our industry, servicing equipment to exacting standards.
As set forth in the various flag administration Safety Codes, Class certificates and insurance prerequisites that are all designed to bring about compliance and safe maritime operation.
Compliance measures are applicable to the size of the yacht, with safety and maintenance at their forefront. One modern maintenance technique mentioned in yacht inspection and maritime advisory notifications is the endorsement for thermal imaging cameras.
To capture a moment in time albeit a heat image (thermogram) is certainly worth more than a thousand words to the yacht owner. A thermal camera can, when used properly, identify electrically generated hotspots in a quick and timely manner, rapidly steering crew to perform corrective maintenance, that if left unnoticed, create excessive heat likely to cause an outage or worse an electrical fire.
When overheating occurs within an electrical system, it can be a sign of loose, over- tightened, corroded connections, undersized conductors, or another failure mode due to high resistance Your checklist for periodic yacht based thermal inspections:
- Electrical switchboards, including the emergency board
- Distribution boards
- Auxiliary equipment, motors, bearings, and starter panels
- Cable raceways
- UPS and Li-ion battery systems
- Shore power connections
Most electrical faults tend to occur at the weakest points in an energised system. When a component is failing, a run-away effect can occur, causing the temperature to dramatically rise. It is Ohm’s law (P=I2R) that describes this relationship, between current, electrical resistance, and the power or heat energy generated.
Abnormal heating associated with high resistance or excessive current flow is the main cause of many problems in yacht electrical systems. Yacht electrical repairs should be prioritised by safety first, i.e., equipment conditions that pose a safety risk followed by criticality of the equipment and the extent of the temperature rise. So when is hot too hot!? NETA (InterNational Electrical Testing Association) guidelines dictate immediate action when the difference in temperature between similar electrical components under similar loads exceeds 15 °C (27 °F) or when the difference in temperature between an electrical component and the ambient air temperatures exceeds 40°C (72 °F). Tests are best performed at 40% load to be effective.
Safety is also paramount whenever an electrical inspection is performed. The removal of secondary dead-front guards is necessary to achieve a direct line of sight, yet no contact is necessary as the thermal camera passively detects the radiant heat from the components. Component temperatures exceeding thresholds are a cause for concern, directing the chief to engage secondary systems before significant thermal damage occurs. Moreover, prompting part replacement orders and preventative maintenance scheduling.
Damage caused by overheating is usually irreversible; the only way forward is to replace the component part – a challenging task if no spares are carried onboard. Disruption is likely, with failure rates exacerbated by the age of the yacht plus inspection and maintenance histories. Typically, third party thermographic surveys are performed on an annual basis by an independent Class registered inspection company – providing the impartiality insurers and yacht management companies seek, and of course, complemented with periodic thermal scans by the yacht engineering crew trained in the technique.
Remember, energised electrical components can become hot enough to melt, causing outages and fire, so plan your independent thermal survey before your next voyage – it could be the best thing
you do today
For more details visit www.geothermltd.co.uk