What Specifications Must Be Considered When Choosing Maintenance Inspection Windows?

Your company is evaluating purchasing and installing maintenance inspection windows to comply with NFPA 70E 2018 Edition. As the manager of the small maintenance team, you are working with a consultant to write a specification document for incorporating these windows into both your existing equipment and new equipment specifications as part of your condition based maintenance protocols. Your company realizes the benefits of assessing the health of its critical electrical assets. The consultant provides insight into all of the criteria that must be considered when specifying maintenance inspection windows. Let’s summarize these criteria that need to be considered.

Maintenance Inspection Windows come with different applications. Let’s summarize:

  • Infrared (IR) Windows: IR windows allow infrared cameras to see and measure temperature of objects and connections inside energized electrical equipment with the covers and doors in place (maintaining a safe and guarded condition). IR Windows allow visual, infrared and UV inspections. These windows are increasing in popularity as companies comply with the NFPA 70E 2018 regulations because they provide a safe and cost-effective way to conduct inspections on energized electrical equipment.
  • Multi-technology Maintenance Inspection Windows: These windows go beyond just infrared inspection by adding ultrasound capability. In addition to allowing for thermal imaging, visual and UV inspections, ultrasound and partial discharge inspections can be performed – all from a single window. This approach is cost-effective for the company overall as one type of window can accommodate multiple inspection modalities.

       How to Specify Maintenance Inspection Windows

One vendor, IRISS, can provide custom maintenance inspection windows in any size, shape and even color. All IRISS’s windows also are either UL Recognized or UL Listed. Custom windows and replacement panels enable previously “un-inspectable” assets to be “inspectable”.

Other Criteria for Specifying Windows:

  • Field of View (FOV)- Field of View takes into consideration the viewing angles and distance from the object of the camera and window working simultaneously. Are all the internal objects visible to the camera or is something blocking the camera’s view? The FOV calculation determines the size of inspection window needed for each piece of equipment. When specifying windows on new equipment, make sure to specify the targets you want to be able to see and put the responsibility for selecting appropriately sized windows onto the OEM’s design team.
  • Window Design – compliance with flammability, impact and load requirements and OEM specifications for materials and color. The Window cover protects the window itself and the maintenance team.
  • Viewing Lens Materials – the lens material must withstand mechanical impact and load requirements with the cover open. The lens must also have a fixed and stable transmission rate for the life of the unit and not change over time. Likewise, the lens material should not change with exposure to humidity or other environmental factors such as vibration. Outdoor lens material should withstand exposure to the sun and not change when exposed to water.
  • Certifications Required – Windows, depending on application, may need to comply with multiple certifications such as UL, IP Ratings, CSA for Canada, IEEE Standards for specific equipment types and specialized certification for marine applications such as Lloyd’s of London Approval, ABS or DNV.
  • Performance specifications – specify the environment temperature where the Window will reside. Arc Containment testing may be required depending on the application of the Window or switchgear that contains the Window – on new equipment this becomes the responsibility of the OEM as part of their “type testing” protocols. Specify the lens material transmission rate be stable over the window’s operating life. Insure that the Windows are compatible with all makes and models of IR and ultraviolet cameras. If you choose a Window with IR, Ultrasound and Partial Discharge applications, the Window must be IP2X compliant.
  • The benefits of using Maintenance Inspection Windows outweigh the detailed planning process thereby creating a safe environment for inspecting electrical assets under full load conditions. With Windows, a single inspector can easily and safely perform a route and quickly gather data and perform a trending analysis to determine each asset’s health. The Windows also provide access to inaccessible targets that could never be inspected before which provides inclusive data on more of your critical assets that require inspection. The goal of condition-based maintenance is to trend the health of the assets over time and determine when an asset is showing signs of deterioration, so it can be easily fixed before the asset fails.



Planning for and determining Maintenance Inspection Window’s specifications may seem cumbersome; however, once the specification is determined and the Windows are installed, the maintenance team will be able to perform routes faster and more frequently and most important, safer. This ultimately limits unscheduled downtime for the company and reduces unforeseen operating costs. Maintenance inspection windows will ultimately reduce the Total Cost of Ownership (TCO) of your electrical infrastructure assets.


How to Specify Maintenance Inspection Windows

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