Optic materials fall into two types; Infrared (IR) Sightglasses/Windows & IR Ports.
An IR Port is a hole or series of holes that provide no barrier between the thermographer and the exposed conductor and are actually a direct “path-to-arc”.
An IR Sightglass or Window provides a fixed barrier between the exposed conductors and the thermographer. This barrier can either be deemed “Arc-Resistant” or “None Arc-Resistant”. An Arc-Resistant IR Sightglass can protect an infrared thermographer from an arc-fault event, a None Arc-Resistant IR Window made from a low cost, thin film polymer material and cannot protect an infrared thermography from an arc-flash.
In order to comply with NFPA70E requirements and reduce the amount of Personnal Protective Equipment needed to perform an IR Scan, an Arc-Resistant IR Sightglass must be used.
None Arc-Resistant polymer IR windows increase the potential injury level due to molten projectiles and PPE should still be worn
In addition to the standard testing required for an accessory such as an IR window, combined energy and pressure testing must be performed in order to assess the resistance of the optic material to an arc-flash.
Parameters noted during an arc-fault event
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- Static Pressure
- Heat Flux ~ Temperature
- Thermoacoustic Effects
IR Sightglasses must be tested for resistance to all three parameters combined in order that risk associated with their installation and use be properly assessed. |
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