Your company’s reliability officer stated that the company is replacing calendar-based maintenance procedures with a Condition-Based Maintenance Program in 2019 to maximize efficiency, increase safety and save money. Electrical Maintenance Safety Devices, such as Infrared Inspection (IR) Windows, allow for real time, infrared data to be collected on energized electrical assets in a closed and guarded condition. Your company has purchased and completed installation of polymer IR Inspection Windows on critical electrical assets. At the next maintenance team meeting, training will be provided on how to conduct inspections using the new polymer IR Windows. The last company you worked for utilized crystal IR windows. Your curiosity prompted research into the polymer IR windows and why they are preferred over crystal IR windows. Let’s see what you uncovered in your research.
A previous article described IR Window Lens Materials and that the choice of lens materials is driven by the application of the window, environmental factors, wavelengths to be measured and cost. Polymer IR Windows are well suited for industrial environments because they are unaffected by mechanical stress, moisture, humidity, sea water and a broad range of acids and alkalis.
Your research found 10 advantages attributed to the polymer IR windows:
- Durable and rugged; able to withstand impact and vibration
- Polymers enable larger windows to be manufactured increasing the inspection area (Field of View)
- Fixed and Stable Transmission Rate (FAST) that is unaffected by mechanical stresses and humidity
- Works with all ranges of IR, Ultraviolet and Visual Inspection cameras
- Successfully Arc Containment Tested in metalclad and arc resistant switchgear
- Received the most certifications in the industry
- Can be custom manufactured to any size, shape and color
- Anti-fogging compared to crystal lens materials that fog due to high humidity
- More affordable than crystal IR windows
- Have an unconditional lifetime warranty
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 (https://www.flir.com/products/irw-x/).
Since some of your co-workers have previous experience with crystal lens IR windows, you will bring this information to the training meeting, so everyone can understand the advantages of the polymer IR windows.
Polymer Infrared Inspection Windows allow for inspections of electrical assets under closed and guarded conditions resulting in time savings, cost savings and improvements in safety procedures. The advantages of the patented polymer lens material versus crystal lens material are numerous and should be the lens material of choice for industrial applications.
Electrical Maintenance Safety Devices, such as Infrared Inspection (IR) Windows, allow for real time, infrared data to be collected on energized electrical assets in a closed and guarded condition. Your company has spent considerable time investigating inspection windows and is considering purchasing and installing them on critical electrical assets. The safety team is researching how to perform an inspection and what data can be obtained from using an Infrared Inspection Window. Let’s investigate!
Simply stated, an IR Inspection Window allows infrared cameras to “see” components and connections inside electrical equipment with the panel covers and doors in place and under fully loaded conditions. Infrared cameras measure the infrared energy emitted by objects which can be equated to an approximation of temperature once some external factors are accounted for. When using an Infrared Window between the camera and the target, the IR window transmission rate must also be factored in to help calculate the target object temperature. Infrared Cameras also take images of the equipment through the IR Inspection Window which allow us to do qualitative comparisons of like components to look for irregularities.
We learned in the article describing IR Window Lens Material that infrared cameras cannot see through glass or plastic. They require special lens materials that transmit infrared radiation. However, more than just the attributes of the lens material must be considered. When performing an infrared inspection, the thermographer must also consider these critical aspects:
1. Transmission Rate of the Lens Material: transmission rates vary based on type of lens material used as well as the thickness of the lens. The thermographer must know the exact transmission rate to enter into the camera or software setting to obtain accurate temperature data.
2. Emissivity of the Targets: defined as the power of a target’s surface material to emit infrared radiation. Materials are assigned an emissivity value between zero and 1.0. It’s important for the thermographer to know the emissivity value of the surface material he is measuring so he can properly compensate for that material on the IR camera. Incorrect emissivity settings on the IR camera can significantly impact the accuracy of the temperature measurements recorded. Targets with low emissivity values such as copper or aluminum bus should be avoided as they may reflect background infrared radiation and lead to incorrect temperature readings.
3. Field of View of the IR Camera: accurate temperature measurements are obtained when the IR camera has full view of the objects being measured. Any obstruction will compromise the temperatures being recorded. Having an IR Window larger than the diameter of the camera lens is one way to help eliminate errors.
4. Window Field of View (WFOV): to ensure that an IR window of sufficient size is being installed, it is important to know the width and height of the target as well as the depth of the target from the door or panel into which the IR window will be installed. For a simple IR window sizing tool, please click here https://www.iriss.com/fov-calculator/
5. Infrared camera’s operating wavelength: be aware of the operating wavelength of the IR camera (midwave vs. longwave). Make sure your IR window is compatible with the camera wavelength.
6. Number of targets being observed through the IR Window: more than one target can be observed through an IR Window. However, size and positioning of the window on the electrical asset is important. Above all, the thermographer must remember that there are three sources of infrared radiation that are measured by the IR camera: emitted radiation from a target, reflected radiation from a source other than the target or transmitted radiation through an object from a source behind it. The thermographer must determine that his camera is detecting radiation emitted from the target and not measuring reflected or transmitted radiation.
Infrared Inspection Windows allow for inspections of electrical assets under closed and guarded conditions resulting in time savings, cost savings and improvements in safety procedures. When determining the number of IR windows needed or the size of the IR Window needed for an electrical asset, other critical factors must be considered to obtain accurate inspection data. It’s important for the company to consult with a reliable infrared window provider to insure accurate window selection for the project.
IRISS and EATON join forces to manufacture the Pow-R-Way III Busway System that enables safe and accurate energized infrared inspections under full load. The UL Listed Joint Cover Design, with the polymer infrared window, enables Pow-R-Way III users to perform critical condition-based maintenance inspections of the busbar joint connections inclusive of infrared, ultraviolet and visual inspection. This Busway System allows infrared inspections to be conducted, safely, at any time. The ruggedness of the joint cover with the polymer window is uniquely designed for industrial environments where mechanical stresses are common.
At IRISS, we provide our customers unsurpassed quality at every touch point. We focus on what we do best by continuously improving infrared (IR) window, online monitoring devices and Ultrasound test equipment technology. We build reliable products exceeding customer expectations while remaining a science-based R&D company and protecting our products with industry leading warranties.
IRISS industrial-grade IR windows facilitate safer, more efficient inspections of energized electrical equipment. Our award-winning, IR window designs feature a durable transparent polymer lens that allows visual, UV, and short/mid/longwave IR spectrum inspections. The Windows are available in custom shapes, sizes, colors and with optional ultrasound ports or sensors.
As solution providers, the team at IRISS brings a multitude of experience from world-class maintenance programs together to meet the individual needs of commercial, industrial, marine, power generation and government maintenance programs.
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Following a recent Arc Flash incident at your workplace, you joined the company’s safety team to search for solutions that would minimize or reduce the risk of another accident occurring during an energized electrical inspection of the company’s equipment. Electrical Maintenance Safety Devices, such as Infrared Inspection (IR) Windows, allow for real time, infrared data to be collected on energized electrical assets in a closed and guarded condition. The team’s research on IR Windows reveals that there are many materials used in manufacturing the lens of an IR window. The next step is determining what type of lens material is best suited for your company electrical assets. Let’s investigate!
There are numerous types of lens materials that can be used in IR Windows. The choice of lens material is driven by the application, environmental factors, light wavelength to be measured and cost. The lens material should:
1. Withstand all mechanical impact and load test requirements
2. Have a fixed and stable transmission rate for the life of the unit
3. Transmit in the infrared wavelengths as a minimum as well as visual and ultraviolet wavelengths if desired
4. Transmit infrared radiation in the mid-wave and long-wave infrared ranges (3 – 12 microns) to coincide with most IR cameras
5. Withstand prolonged exposure to vibration without cracking or degrading
6. Withstand prolonged exposure to direct sunlight without degrading
7. Not absorb moisture (non-hygroscopic)
8. Be of an IP2X fail safe design (touch proof with less than ½“ aperture size even with the lens compromised)
9. Be able to withstand temperatures up to 250°C (482°F)
10. Be resistant to light acids, alkalis and water
11. Be made of materials that are non-carcinogenic and non-toxic and must not contain arsenic, barium, bromine, cadmium, chlorine, gallium, germanium, iodine, lead, lithium, mercury, selenium, sulfur, thallium or zinc
12. Be able to work with all makes and models of IR cameras
The most common materials used in IR windows are Calcium fluoride, Sapphire, IR Polymer, Germanium, Zinc Selenide and Barium Fluoride. Historically, Calcium Fluoride and Barium Fluoride were the most commonly used infrared window optic materials. However, since Barium Fluoride (in powder form) was classified as a possible carcinogen and known muscle toxin, Calcium Fluoride has been used more frequently.
Common Lens Materials Used in IR Windows
The table below lists the common lens materials and their respective performance criteria.
As you can see, some of the common materials in the table do not meet the requirements of being non-hygroscopic (soluble in water) or the Knoop Hardness criteria to withstand mechanical impact and vibration.
Things to Consider Before Choosing IR Window Lens Material
Thought must be given to determine the actual operating environments where IR Windows will be used. Key factors that need to be considered are:
- Is the IR Window for indoor or outdoor use?
- Is the IR Window located in a noisy environment or area of high traffic?
- Will the IR Window be subjected to severe environmental conditions such as humidity, rain, snow, sea water, acids, alkalis or extreme temperatures?
- What is the transmission rate and wavelength that the IR Window will operate in?
The choice of lens material depends on the application needed. Companies must give serious consideration to the intended use and operating environment of the IR Windows so the correct lens material is chosen. Installing Windows that are not compatible with the intended environment or application could be a costly event should the Windows fail mechanically or functionally.
Does Durability of the Lens Material Matter?
Even though crystal lenses have been used historically, they have disadvantages when used in industrial settings. Crystal windows like Calcium Fluoride and Barium Fluoride are soluble in water (hygroscopic) and will, over time, absorb water vapor into the crystalline structure reducing Infrared transmission through the lens. In addition, crystals are brittle and unable to withstand impact and mechanical stresses commonly seen in industrial settings. Mechanical stress can fracture the crystal lens or change the crystalline structure causing decreasing transmittance. If transmission rates of the material change over time, the data being recorded could be compromised. Could this be why crystal lenses themselves are not guaranteed by crystal window manufacturers?
Polymer IR Windows
Polymer IR Windows are unaffected by mechanical stress and are non-reactive to moisture, humidity, sea water and a broad range of acids and alkalis. They are well suited for industrial environments. Polymer Windows are extremely resilient and tend to absorb impact rather than shatter. Polymer Windows can be reinforced with special grills insuring that it passes industry standard impact tests. A transparent polymer optic is available allowing inspections in the ultraviolet, visual, short-, mid- and long wave infrared spectrums. The only disadvantage of a Polymer Window is if the environment exceeds an ambient temperature of 200°C (392°F) which is rare in industrial applications.
The logical approach for a company considering IR Windows is to work with the supplier that offers a variety of lens materials. They can help select the best suited Window for the application and environment.
Different lens materials will react differently to moisture, humidity, chemicals and mechanical stresses. It is mission critical that a company identify the specific application for the IR window and the specific environment where the IR Window will reside so that the appropriate lens material is selected. Companies should work with reputable IR Window suppliers that offer a variety of lens materials to help identify the appropriate lens material for the application in question.