Proper installation of the infrared window is critical for the long-term use of the window and for the long-term performance of the panel and equipment enclosure. Although an infrared window is not as strong as the steel it replaces, installing an IR window is no different than many other modifications commonly performed on switchgear and other electrical applications. Therefore, if a company has a policy for modifications such as: replacing or adding an ammeter or similar device, installing a visual inspection pane or modifying a cabinet to add a new conduit run, then it is logical to include infrared windows under the same policies. For example, one would want to refer to any existing policies relating to: pre-planning, design/installation approval, installation best practices and post-installation inspection by an in-house or external authority.
Do Not Pass "Go"
Confirm the following prior to planning any modifications to an electrical equipment enclosure:
• Ingress Protection: Ensure that the NEMA or IP rating of the IR window or other component is rated for at least the same level of protection that the current enclosure is rated for. Never install an infra red window or any other component with a lower rating than the equipment onto which it is being installed.
• Tests and Certifications: Ensure that the IR windows have been tested and approved by the relevant certification bodies. Official test certificates and documentation should be easily obtained from the manufacturer.
• Explosion Ratings (if applicable): Enclosures located in intrinsically safe areas should never be modified in the field unless designs have been cleared with, and post installation inspection and re-certification will be performed by an Authority Having Jurisdiction prior to start-up.
Identify All Targets
Start the process by identifying specific targets on each piece of equipment. In addition to fuses and breakers, most infrared surveys focus on bolted connections within the gear, as these areas are considered the weakest points. These areas include:
• Cable connections
• Bus bar connections
• Isolator or circuit breaker connections
Make a quick inspection of the interior of the switchgear to identify these targets. Once identified, make every effort to standardize their emissivity while equipment is de-energized. Common methods include use of electrical tape, high-temperature paint or IRISS IR-ID labels. After emissivity standardization is complete, it is important to photograph each target since these photos will be used for report templates and future reference.
On many switchgear models, it is advisable to install viewing windows in the front and back for better access to the main breaker and bus connections. Ask the manufacturer for drawings and suggestions regarding the critical inspection locations for your equipment. This information, along with the experience and knowledge of the site maintenance engineer, will prove useful when calculating window placements and quantities.
Affixing information labels is an important final step in the installation process. One label should identify what the window is and how to use it. A second sticker should contain the following information that will be critical in performing a thorough and accurate infrared inspection:
• Each inspection window should be given a unique number. This will be invaluable, especially, if there are multiple windows on one electrical panel.
• Document the type of window (MW or LW) and the effective wavelength of the window.
• Record the transmission rate of the window, and the proper transmission compensation value for the MW and LW.
• Record all target data on the on the ID label. The most common method of documenting target location is the clock face method: i.e. bus bar connections at 4 o'clock. It should be noted that there may be multiple targets being surveyed through the IR window.
• Some cameras do not have the ability to adjust the external optics transmission; therefore, thermographers may use the emissivity settings on the camera to cover transmission and emissivity losses. Multiply the target emissivity by the transmission rate of the window.
After the window installation is completed, the thermographer should conduct a benchmark inspection to set the base line. Data for each inspection point should be recorded in a spreadsheet or database for trend analysis over several surveys. There are software programs available to assist with database management and trending of infrared data.
1. Do your homework first: check all applicable certifications and ratings.
2. Gather as much information as possible, while the equipment is de-energized.
a. Take high quality digital pictures
b. Standardize the target emissivity
c. Make detailed measurements
d. Note any internal obstacles
e. Conduct any outstanding maintenance tasks
3. Complete a thorough Risk Analyses and Method Statement before starting energized installations.
4. If possible, complete a specialized training program dealing specifically with installation of infrared windows.
5. Remember to label the windows correctly, since this data will be used during future inspections.
6. Do a complete infrared inspection at the end of the window installation in order to create a benchmark/baseline for future inspections.
Tip provided by: Arby Dickert, Americas Sales Manager, IRISS, Inc.