Protecting personnel and productivity

Those who are implementing EMSD-based programmes are reaping benefits in terms of efficiency gains, cost control and fire prevention. Because lower PPE levels are required, inspections are quicker. They can be made even faster when a large infrared window is installed to allow a complete busbar, for example, to be scanned in single pass of the thermal imaging camera.

As the process is more efficient, less manpower is required. Electrical systems can be inspected more frequently and crucially this includes process critical systems.

Much of the recent acceptance of IR windows has coincided with the increase in the level of awareness regarding electrical safety and risk reduction. Organisations such as the IEEE have been at the vanguard of this movement with its ‘Safer by Design’ campaign. In response, switchgear manufacturers are increasingly installing IR windows at the point of manufacture.

This, in turn, has generated additional impetus for companies to retrofit equipment.  If you are thinking about this option, here’s an outline of what you need to consider to get the most from the investment.  

Window type

Quite simply, an infrared window is a data collection point for a thermal imaging camera. All types must fulfil the strength, rigidity and environmental requirements of the type of equipment into which they are to be installed and be compatible with the IR equipment being used.

The design, size and material used are driven by considerations such as field-of-view, camera lens compatibility, intended environment, sealing requirements and safety.

Lens materials

The choice of lens material is usually driven by application requirements, wavelength and cost consideration. Long wave infrared is most commonly used in the factory, predictive maintenance sector, a field where durability is a key consideration. While crystal windows are among the best broadband IR transmitters available, they do degrade and fracture easily. This is why polymer lenses were introduced and are becoming increasingly popular.

Emissivity

The emissivity of a material is the relative ability of its surface to emit energy by radiation. Properly compensating for the various emissivity values of all the components on the factory floor is one of the most critical factors in performing accurate and meaningful inspections. A typical electrical cabinet, for example, may contain materials with emissivity values from 0.07 to 0.95.

Transmittance

Maintenance professionals use IR cameras mainly to take quantitative (temperature measurement) images. To ensure accuracy, it is important to understand what other variables in the external environment can lead to possible measurement errors.

As well as emissivity, reflection, distance, humidity and camera angle all play an important role. When an IR window is used, transmission compensation needs to be factored in. Here, too, training is essential.

Field of view

How many windows? What diameter? The answer depends on three considerations: outside diameter of the infrared camera lens, the camera’s FOV and the window’s FOV. Talk to your camera and window supplier for advice.

Installation

Follow set protocols for modifying electrical equipment enclosures. This is critical to the long term use of the window and overall system performance. You’ll need to consider ingress protection, standards compliance and explosion ratings and complete a detailed risk assessment to identify hazards involved in installation.  

Standards 

Trying to sort through the myriad of certifications and standards relevant to infrared windows can be a daunting task, but help is freely available.

Arc flash

An arc flash is a short circuit through the air that creates an explosion equal in force to up to three sticks of dynamite. Since most incidents are triggered by human interaction, that blast occurs within a short distance of the worker. Various standards are in place and well documented to guide you in best practice.

The above sections are brief résumés of chapters in a new book produced by infrared windows specialist, IRISS. Written by a professional thermographer, it is a technical guide to scientific and engineering matters relating to the technology. Called 10 Things You Need To Know About Infrared Windows, the final two chapters provide an overview of PESD programmes and the cost-benefit analysis of their implementation.

To request a hard copy of the publication, please email: [email protected] or, to download a copy, visit www.iriss.com/10things.