Warnings of failure by infra-red monitoring

Where will your next plant outage originate? The majority of plant outages are caused by the failure of an electrical component and the resultant interruption to the power delivery system

Where will your next plant outage originate from? Statistics show that the majority of plant outages are caused by the failure of an electrical component and the resultant interruption to the power delivery system or by actual physical damage to plant equipment caused by an arc flash explosion.

Infrared inspection of electrical equipment is a well known and proven method for reducing failure and associated downtime.

However, traditional methods for scanning high energy equipment, such as removing the covers are no longer acceptable due to the risks associated with arc-flash.

With the general industry wide adoption of NFPA70E as a method to mitigate arc-flash risk and injury, infrared scanning of electrical equipment is becoming more difficult.

To mitigate these risks, many companies are installing infrared sightglasses (sometimes called windows) manufactured from a coated crystalline material or protective mesh: these are transparent to infrared cameras and as such allow scanning without removing the covers and exposing operators to arc-flash risk.

Other options include a combination of a view port and a dedicated mating fisheye lens or a thin film plastic window.

The installation of a view port and mating lens ultimately requires an operator to scan via an open 0.62inch hole in the equipment - (IEEE C37 Switchgear guidelines state maximum enclosure opening of 0.5inches) - using a proprietary camera and expensive lens combination.

Without any barrier between the thermographer and the live electrical equipment there is a direct arc path to the operator, in addition the oversized opening required may allow the ingress of foreign bodies into the equipment or human contact with live parts with disastrous consequences.

From an initial cost analysis, thin film polymer windows also look like an attractive option.

However, in order that the polymer optic be transmissive to infrared rays it must be extremely thin, in the region of 0.01inches, which means that under an arc-fault condition the optic itself could turn into a molten projectile and cause severe contact burns to an operator.

Additionally, this type of window is generally only suitable for installation into a NEMA1 rated, indoor enclosure.

Recent developments in infrared sightglass technology have resulted in a high strength, broadband crystal option being available, such as the Hawk IR Sightglass, which can withstand the forces associated with an arc-flash, operates with all infrared cameras without the need for high cost, proprietary lenses.

Available in three sizes; 2inch (50mm), 3inch (75mm) and 4inch (100mm), the Hawk IR Sightglasses transmit both infrared and visible light and have been successfully arc-flash tested in accordance with IEC and IEEE standards for worldwide compliance.

The flexibility and overall compatibility of the sightglasses with virtually any IR camera, coupled with the strength and longevity of the Clirvu coated crystal have encouraged industry leaders such as GE, Powell, Texaco and Weyerhaeuser to install thousands of these arc-resistant, UL recognised sightglasses.

The Hawk IR Sightglass C-Range can be installed into virtually any piece of equipment at any operating voltage indoor or outdoor and unlike view ports without a window or barrier, are weatherproof even in the open position.

The device is designed for installation into panels, motor boxes or transformers of any thickness, and has no internal fixings such as nuts or bolts which could fall inside the equipment and cause an explosion.

In addition to infrared scanning, the device also allows visual inspection and identification of components within the equipment, an important advantage when inspecting crowded panels.

By visually identifying the component being scanned, repairs can be carried out quickly and efficiently.

The Sightglass, incorporates a non-conductive front face gasket which not only protects the camera lens from impact with the sightglass frame but also removes any path-to-ground concerns.

The coated crystal is impervious to moisture, mild acids and alkalis and the anti-static properties repel dust and dirt keeping the optic clean and useable.

Each Sightglass is supplied complete with a locking, protective cover to prevent un-authorised access to the optic.

The broadband optic is suitable for use with any infrared camera, and allows added safety measures such as correct body positioning in relation to the Sightglass to be utilised.

In contrast, a view port and lens combination often requires the thermographer's face to be in the direct path of an explosion should an arc occur during the scan.

The Sightglass is UL/cUL approved for installation at the OEM level or as a retrofit in the field on NEMA-Type 1, 3 and 12 enclosures, is tested for resistance to internal arc, in accordance with international IEC 62271 and IEEE C37 requirements and is a standard option on many MV equipment, including Rockwell Automation Arc-Resistant MV Starters.

It is suitable for indoor and outdoor equipment, as well as vertically and horizontally mounted cabinets.

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