Thermographic Testing
INTRODUCTION
Thermographic testing, also referred to as thermographic inspection and thermal imaging, is widely used in a range of premises as part of predictive and preventative electrical maintenance activities, covering items such as motors, main switchgear panels, distribution boards, control equipment, busbar systems and cabling. With the thermal images obtained, it is possible to identify hot spots arising from faults such loose connections, overloaded circuits, transformer cooling faults, overheated motor windings and other electrical defects and effect repairs at an early stage.
Visual Image
Thermal Image
STATUS OF THEMOGRAPHIC TESTING
Despite its benefits, thermal imaging is not recognised in BS 7671 as a test instrument, as a result of which it should be considered as being in addition to, and not a replacement for, conventional electrical inspection and testing programmes. Whist an excellent tool, thermal imagining is unable to identify defects such as physical damage to equipment and wiring, over rated fusing and lack of earth continuity. Nevertheless, it is recognised as being an extremely effective component of a planned preventative maintenance programme, particularly in sectors such as healthcare and financial services, where isolation of the electrical supply to facilitate conventional inspection and testing can become increasingly difficult.
There are no hard and fast rules as to the frequency of thermographic testing and much will depend on a risk assessment and the ongoing test results obtained. Initial testing frequencies will vary depending on circumstances, although commonly would be set at intervals of 12 months.
As well as being carried out by specialist contractors, thermographic testing can also be conducted by in-house electrical engineers using purchased equipment and with the correct training in the use of such equipment and the analysis of the test results. In these circumstances, a period of testing considerably shorter than once every 12 months may often be employed, particularly on major plant.
SURVEY EXPECTATIONS
In circumstances where thermographic testing is undertaken in the manner prescribed, details of this favourable risk feature are to be included in the survey report.
Risk improvements calling for an introduction of a thermographic testing programme are to be based on a risk assessment for which features such as the type of premises and environment encountered, together with the MD & BI exposures and loss/incident experienced should be considered. It is not expected that a risk improvement calling for thermographic testing will be raised routinely for smaller/medium size risks surveyed.
Where a risk improvement is considered appropriate, thermographic testing will normally be submitted as a Recommendation rather than a Requirement. The RiskSTOP risk improvement wordings database contains a standard wording which can be utilised or adapted as necessary.