Wednesday, January 2, 2019

How Have Infrared Windows Evolved Over Time?

It’s January 2019 and your company has initiated a Condition-Based Maintenance Program of the company’s critical electrical assets to maximize efficiency, increase safety and save money. New Polymer IR Windows have been installed and the maintenance team has attended several training classes on how to perform maintenance inspections and collect data using the polymer IR windows. Many of your colleagues have many years of experience working with crystal IR windows. During one of the final 2018 training sessions, information was provided as to why polymer IR windows were better suited to industrial environments than crystal IR windows. Some of the guys talked about their past experiences using windows and were curious as to the evolution of the IR windows over time. Let’s look at the history of IR windows and how we arrived at the current choice of polymer IR windows.

The interaction between an infrared window and an infrared camera shows that the camera can only measure the temperature of the electrical components that it can see through the infrared window. Infrared cameras cannot see (measure temperature) objects through glass, metal or plastics and therefore require special lens material that will transmit infrared radiation.

Historically, the common infrared window lens material was made of a fluoride based crystal. However, the fluoride crystal lens is fragile and will not withstand impact. Once the crystal breaks, the window is not IP2X electrical failsafe as a hole as large as 4 inches in diameter could be left in the equipment. The crystal lens is also hygroscopic insofar as it absorbs moisture from the atmosphere over time and can become contaminated which leads to inaccurate temperature measurements. Eventually, the lens contamination becomes visible to the human eye (looks “foggy”) but long before that the transmission in the IR spectrum is negatively impacted. Because of these limitations, crystal IR windows only have a limited lifetime warranty.

Evolution of IRISS Maintenance Inspection Systems

The next type of IR window manufactured was a polymer window using an opaque polymer lens with a reinforcing grill. The opaque polymer eliminated the fragileness of the crystal lens and the infrared transmission was excellent; however, the opaque lens did not allow visual or ultraviolet inspections. The advantages of this design were that it was impact and load resistant, was IP2X electrical failsafe due to the honeycomb reinforcing design, was made of insoluble materials and could offer an unconditional lifetime warranty.

Overcoming the lack of visual and ultraviolet capability was the next hurdle. The next version was manufactured using a patented clear infrared polymer lens design. This window design offered all the benefits of the opaque polymer lens but now provided both visual and ultraviolet viewing capabilities.

Recently, crystal lens window manufacturers such as FLIR have recognized the advantages of the patented polymer infrared windows and are now offering them to their customers (

But, innovation didn’t stop here. What other types of inspections could be routinely carried out on electrical assets using this infrared window? Ultrasound ports and partial discharge ports have been incorporated into the window design enabling both infrared and ultrasound inspections to be performed through the same window. The IR Window should now be called a Maintenance Inspection Window and not just an IR Window.

Another innovation with the newly described maintenance inspection windows is that they can be custom designed and manufactured to any size, any shape and any color. Windows are no longer confined to being small round or small rectangular sizes and shapes. This is a profound efficiency opportunity for companies that have many critical electrical assets and components that need to be inspected. Now a company can have one large inspection window that allows infrared, visual and ultrasound inspections covering a large field of view of many assets in place of many small windows that look at one or two assets. Some customers asked if the inspection window could be upgraded to an IP67 (NEMA6) environmentally sealed design that allows the window to better withstand harsh environments. This is “ENV” design is another option available today for electrical inspections of assets that are located outdoors.

The next innovation was the addition of an NFC (Near Field Communication) based tagging system to the inspection windows. Using a smartphone app, Special Inspection instructions and data is easily added to the tag on each window. The inspector can look at historical data on the asset tag to determine the health of the asset. Any problems can be flagged as an “alarm” condition that notifies management that a problem has been found. The Maintenance Scheduler can create and assign inspection routes for the maintenance line staff to perform. Route completion is tracked via the NFC asset tags.


As companies replace calendar based maintenance with condition based maintenance programs, the current maintenance inspection windows with infrared or the combination of infrared and ultrasound allow multiple technologies to be inspected using a single window design. These maintenance inspection windows allow an asset’s data to be collected under full load in a safe and guarded condition regardless of where that asset is located. The various options available of the inspection window design allows companies to select those designs that best enable inspection data to be collected and recorded in a condition based maintenance program.


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