Message Board Thread - "IR Windows"

Back to Threads | Back to Forums

TitleByPosted On
IR Windows newguy 6/13/2007
I'm hearing that the Hawk IR windows with the crystals have to be replaced every 2-3 years, is this correct?
I also heard that the the blast rating is only good when the cover is on. Anybody have any information on this?

Re:IR Windows Tony Holliday (HAWK IR) 6/15/2007
newguy wrote:
ring that the Hawk IR windows with the crystals have to be replaced every 2-3 years, is this correct?
I also heard that the the blast rating is only good when the cover is on. Anybody have any information on this?

Hello Newguy,

Unfortunely, your information is not correct, the Hawk IR windows do not need replacing and actually hold a lifetime warranty.

The latest 50kA blast test was completed in accordance with ANSI/IEEE C37.20.7 - 2001 alongside KEMA & ABB, so you can rest assured that the tested were performed correctly. Unlike open holes or meltable polymers, the CLIRVU crystal can - and has - withstood a 50kA arc-fault without mechanical support from the cover.

The Hawk IR Sightglasses are now the only product to be available on ABB SafeGEAR without derating its arc-fault containment capability, others include huge multinational OEMS such as Rockwell Automation/Allen Bradley whom we have also Arc-Tested with.

Additional Arc-Fault tests we have completed are to IEC62271 (Europe) and EMACS 14-1 Type B (Canada).

Some IR window companies claim that if the door remains closed 99.99% of arc-flash triggers are removed and hence arc-resistant IR windows are not required. This is a very dangerous and uneducated statement indeed, if arc-faults only occured with the covers removed then there would be no such thing as Arc-Resistant switchger which is only arc-resistant with the doors closed.

Dont be fooled by low cost IR window or port options which claim there is no need for arc-resistance, this is simply an attempt at justification as to why those products cannot pass such tests.

If you want to remain safe whilst performing your infrared scans then Arc-Resistant IR Sightglasses are the only way to go.

I hope that this was informative.

Best Regards,

Tony Holliday
Hawk IR International
Re:IR Windows Martin Robinson 8/5/2007
newguy wrote:
ring that the Hawk IR windows with the crystals have to be replaced every 2-3 years, is this correct?
I also heard that the the blast rating is only good when the cover is on. Anybody have any information on this?

The 2 most common failure modes for an infrared window is breakage through impact and failure due to water ingress from environmental issues such as humidity, saltwater, etc...

Presently there are no specific standards relating solely to infrared windows there are however standards for visual viewing panes that are fitted into switchgear. IEEE C37.20.2 sectiona.3.6 requires that a mandatory load and impact test is completed on visual viewing pane assemblies fitted into switchgear.

The mandatory tests completed on switchgear such as Arc tests, etc... are to type approve the switchgear ONLY not the components within the switchgear; you cannot take a component such as an infrared window and claim that it is arc rated, unless you are fitting it into the same make and model of switchgear in exactly the same location… There are just too many variables such as:

Window dimensions (larger windows are weaker!)
Window Position (Distance window is placed from arc incident during test)
Dimensions of the switchgear cabinets (differing volumes = differing pressures)
NEMA / IP Ratings of Switchgear (a window fitted into IP65 rated switchgear would be subjected to much more force than a window fitted into IP55 switchgear, etc…).
Switchgear ratings ( is it being fitted to HV, MV or LV switchgear)

At IRISS, we manufacture infrared windows from both crystals and polymers and our position on crystals is simple; we DO NOT recommend crystals for industrial infrared window applications because they are fragile... we do however recommend the use of our VPFR range of windows as these are a unit that was designed and built to overcome the most common failure modes of infrared windows and are the only IR window assembly that have undergone all the tests required by UL508, UL746C and IEEE C37.20 for impact, load and flammability and are also insoluble and resistant to light acids and alkalis.

Until the standards committees within NFPA, IEEE, UL etc…. agree on a specific standard applicable to IR windows, the disagreements relating to what tests are relevant or not will continue. Until this happens IRISS will continue to build IR windows to resist impact, load, water ingress and flammability.


Should you wish any further information please feel free to contact me directly.


Martin Robinson
Re:IR Windows Bob Berry 8/5/2007

I'm glad you do not avoid the topic of type tests the way other window manufacturers have done in the past.

It is my opinion and the opinion of a number of switchgear manufacturers that retro fitting windows would invalidate these tests. I am also aware of one case where a switchgear manufacturer would not accept warantee if there were retro fitted windows.

What is your opinion?

Also I came across one of your videos recently showing impact demo on windows with a hammer. I suggest you put a link to that video here for others, it may open their eyes a bit.
Re:IR Windows Tony Holliday (HAWK IR) 8/8/2007
A few points on IR Window arc-testing;

1. Larger dimensions maybe weaker but if they are still strong enough to withstand the end-use requirement - arc-flash protection - then the dimension itself is not important, the safety margin is. This is quantifiable.

2. Volume and Pressure are related, but this static pressure increase does not cause the physical damage associated with an arc-fault event. This effect which causes personnel and equipment to be "blown apart" is a dynamic - or thermoacoustic - wave which is a function of short circuit current and not volume this is quantifiable.

2. Position. The closer the position of the window to the arc-fault the higher the incedent energy level the optic is subject to. This is quatifiable.

3. NEMA/IP. These are environmental ratings and have nothing whatsoever to do with arc-testing or force. IP stands for Ingress Protection, these tests quatify the amount of fluid or dust a component or assembly is subject to at a given angle. This lack of understanding is dangerous.

4. HV/MV/LV Switchgear has virtually no bearing on the available energy. The nominal voltage of the system gives an indication of minimum arc-gap. This lack of understanding is dangerous.

Hawk IR International Ltd. alongside Rockwell Automation a leading manufacturer of Arc-Resistant MV Starters have published a number of papers relating to infrared inspection of electrical equipment using Infrared Sightglasses/Windows and how thorough arc-testing can be used to determine an incendent energy level upon the relevant optic and mounting.

I suggest that endusers consider the reason infrared windows are installed;

If there was no risk of arc-flash and NFPA70E did not exist, would infrared window installations be so prevolent? No, they would not.

If arc-faults only occured with the covers open then would every major switchgear manufacture in the U.S manufacture Arc-Resistant Switchgear? No they would not.

The bottom line is that today, thermographers have a choice where IR windows are concerned;

1. They can use polymer optic IR windows whose optics CANNOT withstand the combined dynamic, static pressures and temperature of an arc-fault but CAN be hit with a hammer or driven over by a truck.


2. They can use an Arc-Resistant IR Sightglass, which has been tested to every AR Standard in the world and is installed by most major Switchgear OEMS in AR gear.

The choice is ultimately down to the end user, but if your company is considering buying IR windows as a result of an Arc-Flash Hazard Analysis, then an arc-flash hazard exisits and as such products designed to withstand that event should be installed. Would anyone buy untested, polymner PPE and hope it did not melt as a means to satisfy NFPA70E?

For more information on infrared sightglasses, arc-testing, IP & NEMA, etc. please visit or feel free to contact me directly.


Tony Holliday
Hawk IR International Ltd.

P.S. If there are any folks out there who do maintain their switchgear by hitting it with a 2lb ball hammer or by driving their truck over it please drop me a line!
Re:IR Windows Toolman 8/15/2007
Yes an arc flash can happen with the door closed - following are some images I took of the results of an incident that occurred this summer....first two are of the remains of some of the contents..thirs is what was left of the door....
Re:IR Windows Toolman 8/15/2007
Re:IR Windows Toolman 8/15/2007
Re:IR Windows - Alternates to the windows, new technology RK 10/10/2007
To avoid exposure to the arc flash hazard and negate failures occurring between scan cycles, why not just install IR monitoring permanently inside the cabinet for constant thermal monitoring and alarming 24/7/365?

One gets to place the sensors where needed within the cabinet. Even the main bus in the metal clad switchgear.

Fit and forget IR sensors, with a life time warranty and calibration. No taking apart the switchgear each year and standing infront of it for a scan.
The temperatures are reported back to the SCADA system, and record in real time for trending as well.

-Bob Kern

IR Sensors installed RK 10/10/2007
IR Sensors Installed
IR Sensors RK 10/10/2007
Close up of an IR senors.

  • Back to Threads
  • Back to Forums


  •   Copyright © FLIR Systems, Inc 2012