General FAQ's

Frequently asked questions regarding IR thermography and Infrared Windows

1. Can you survey electrical equipment by just looking at the enclosure temperatures with an infrared camera?
2. What are the minimum dialectric clearances?
3. What is the effect of using infrared windows on certified enclosures?
4. What effect do the windows have on the thermal image?
5. Do we have to have a crystal or can we use a grill?
6. Can we have one lens and use it in all of our windows as we go?
7. Are custom materials or sizes available?
8. Who can install and service an IR window?
9. How long is the warranty on your IR windows.
10. What materials do you use in the construction of your IR windows?
11. What does IP65 and IP2X mean?
12. Can we install IR windows in the field?
13. What is the Arc Flash rating of your IR windows?
14. What are the benefits of fitting IR windows?
15. Why do I need bigger Infrared windows?
16. How Can I measure the transmission rate of an infrared window?

Q.  Can you survey electrical equipment by just looking at the enclosure temperatures with an infrared camera?

A.  -You cannot obtain adequate or reliable information with an infrared camera without looking at the actual electrical components. The majority of thermographic cameras are based on digital camera technology and therefore requires a direct-line-of-site to record an accurate image.  Surveys are hampered by cabinet designs that obscure the target components being imaged and thermographers are put at risk by having to open cabinets or doors in an attempt to gain access to the internal components that they wish to image, even the most comprehensive risk assessments and method statements cannot avoid the obvious risks involved.
The use of Infrared Inspection ports is becoming more common place, in fact electrical panel manufacturers are now fitting Infrared inspection ports, grills, mesh screens, etc. in an attempt to make their panels infrared friendly.

Return

Q.  What are the minimum dialectric clearances?

A.  -The most important area of concern is the maximum safe distance between the IR window and any live components; this is called the “dielectric clearance”. The recommended minimum dielectric clearances are as follows:
5 Kv Equipment -no less than 4 inches !!
15 Kv Equipment -no less than 6 inches !!
It must be noted that under no circumstances can the minimum clearances be compromised.

Another important point to remember is that most IR cameras can not focus closer that 4".

Return

Q.  What is the effect of using infrared windows on certified enclosures?

A. -If the panel that you intend to fit the IR window into carries any certification marks then these should where reasonably practicable not be breached in any way. In the case of a panel with UL certification, you should only consider using UL recognized components; a question that is regularly asked is how does field installation of IR windows affect the UL status of the panel?
The component (in this case, IR window) can be field or factory installed. The issue is the listing of the product in the field to which it is installed. Installing this product in the field does not negate the listing mark. Customers often modify assemblies that are UL listed and marked. Any modification done in the field is not covered by an existing UL mark. Therefore, UL is not responsible for the certification of these listings.
When changes are made to listed assemblies that affect the rating of the equipment, UL will do a field inspection of the modified product to re-certify the equipment meets UL requirements. A customer may request this to be done. The IR window would have to be added to the UL procedure for that piece of equipment. If it is not covered in the UL procedure then UL could not re-certify.
In cases where the IR window is not part of a product’s UL listing, there is another option, the field evaluation by UL. Since the IR window is a UL recognized component, UL should be able to provide a UL mark that would verify the modified product had been evaluated. However this would probably not be required in most cases.

Return

Q.  What effect do the windows have on the thermal image?

A.  -The lens material's ability to absorb some of the infrared radiation will lower the perceived temperatures somewhat. This can be accounted for with a simple procedure or by adjusting the transmissivity setting on your camera or software. The clarity of the image will not be affected.

Return

Q.  Do we have to have a crystal or can we use a grill?

A.  -Where there is no risk to the operator of electric shock or flash over, a viewing port with no crystal but with an inner protective grill may be installed to protect the assembly from objects falling into the component during inspection but still allow full access for an image to be taken.

However you must ensure that all grills have a maximum diameter of 12mm (IP2X) and you should also be aware that the use of grills still requires the use of full personal protective equipment as they are not compliant with NFPA 70E as the thermographer is still exposed to energised components within the panel being inspected.

NFPA 70E

IP2X

Return

Q.  Can we have one lens and use it in all of our windows as we go?

A. Where there is no immediate risk to the operator of electric shock, he or she may use a view port with a removable crystal option, resulting in significant savings as only one crystal will be required regardless of how many viewing ports they may have. This also allows you to use viewing crystals such as coated ZnSe which has a 99% transmission rate from 4-14 microns. ZnSe is too expensive to use in large quantities, but because you only require one crystal with the IRISS you can take advantage of the best IR viewing crystals on the market, together with the additional benefits that using them brings, at a fraction of the cost. The VPLC-50 lens carrier includes a lens and lens housing. This assembly fits into the VPR-50 windows. Both a VPLC-50 lens and VPR-50 windows are required to use the removable lens system.

However once again the use of a removable lens system is not NFPA 70E or IP2x compliant, and should you decide to use this system full precautions must be taken regarding the correct level of personal protective equipment.

NFPA 70E

IP2X

Return

Q.  Are custom materials or sizes available?

A.  Custom window sizes, design, and materials are available, however the prices will vary depending on the material, specifications, and possible the number of units ordered. You must be aware that when adopting this approach the IR window is not tested or certified to any recognized standard and local approval must be gained to certify their use.

Return

Q.  Who can install and service an IR window?

A.  The IR window must be installed and serviced only by qualified electrical personnel, more information regarding installation can be found in this website.

Return

Q. How long is the warranty on your IR windows.

A.  Our general purpose IR windows using the IR polymer are guaranteed for the life of the panel in which they are fitted, they are not guaranteed against damage or mis-use.  As our IR windows do not use any adhesives in manufacture or installation our products can be moved or upgraded with ease,  We do not however give a warranty on any of the Fluoride crystals as they are hygroscopic and fragile, therefore they will fail eventually.

Return

Q.  What materials do you use in the construction of your IR windows?

A.   The Bodies and gaskets of our IR windows are constructed from flame retardant plastics and rubbers, with regards to the lens materials a full list can be found in our Materials pages on this website.

Return 

Q.  What does IP65 and IP2X mean?

A.  IP65 and IP2X are integrity proofing test against agreed standards.  IP65 relates to a NEMA 4 classification, a copy of the full report can be downloaded from this website.

SIRA IP Test Report

NEMA Standards

Return 

Q.  Can I install IR windows into our field installations?

A.  There are many issues to be considered when it comes to the field installation of IR windows.  The first point of call should be to the manufacturers of the equipment to discuss any associated risks and produce a risk assessment and method statement covering all the requirements of the installation, you should then contact any relevant certification bodies regarding the install procedure, fitting instructions and certifications of our IR windows.  Remember that under no circumstances can you impair the integrity of the panel in which you intend installing IR widows. 

In the case of UL I have attached a copy of a letter that we received from them outlining that during the testing of our IR windows that consideration was given to their suitability for field installation when installed following our installation instructions.

UL Letter re: Field Installation

Return 

Q.  What is the Arc Flash rating of your IR window?

A.  No IR window or individual component can ever be Arc Rated or can protect you from Arc Flash, Arc flash has the potential to produce a shock blast of up to 700 miles per hour with a core temperature of 15,000 C, and there are no materials that can resist that type of temperature and force (See Video). Panel assemblies are designed to contain and survive differing levels of arc flash energy.
There are industry standards designed to test panels for resistance to Arc Flash.  If these assemblies are tested with IR viewing ports fitted, and pass the test, the standard is awarded to the assembly only, this does not mean that the IR window or any other components are Arc rated for any other assembly.

Each assembly needs to be dealt with in a case by case scenario and comprehensive risk assessments completed.

Return 

Q.  What are the benefits of fitting IR windows?

A.  To a thermographer there are many benefits to using IR windows, direct temperature readings will always be the preferred medium for gathering information especially on critical plant and services. IR windows are an asset to any inspection program and remove the necessity of:

• Complex risk assessments and method statements prior to an “open panel” inspection.
• Opening panels and exposing manpower to potentially hazardous live components.
• Permits to isolate and shutdown panels.
• Restarting plant after shutdown.

The additional benefits of using of IR windows are:

• Improved thermographic survey results, as they are direct temperature measurements.
• Improved plant reliability.
• Safer working environment for thermographers.
• Reduces the amount of time and costs involved in a thermographic survey, as no shutdowns are required. . 

IR windows make our work safer, faster and more accurate, but only when installed and used correctly.  If careful consideration is not given to the issues discussed in this paper the inspection port will give inaccurate results leading to poor diagnosis, thus negating the reason for fitting them in the first place.

Return  

Q.Why do I need bigger Infrared windows?

A. We have produced a paper outlining all the factors that need to be considered regarding this very subject. 

Why do I need bigger IR windows  

Return  

Q. How Can I measure the transmission rate of an infrared window?

A.  It must be noted that specialised instrumentation is used to measure the spectral transmittance of IR window materials, however as the majority of thermographers are unable to access this type of instrumentation we have to derive methods of using our IR cameras to calculate the approximate transmission rates. I have used this method in the field many times and it has proven to be accurate and reliable, we call it the “coffee cup test”

Method 1: IR camera with external optics transmission compensation:

1. Using electrical tape mark a low emissivity target onto a coffee cup and fill the cup with hot coffee.
2. Set the transmission rate to 0.99 and the emissivity to 0.95.
3. Measure the temperature of the emissivity target on the coffee cup.
4. Place window in front of target.
5. Calculate the IR window transmission by adjusting the camera transmission rate until the temperature reads the same as the temperature without the IR window.
6. Mark transmission rates on IR windows.

Method 2: IR camera does not have external optics transmittance compensation.

1. Using electrical tape mark a low emissivity target onto a coffee cup and fill the cup with hot coffee.
2. Set IR camera emissivity to 1.
3. Measure target apparent temperature without window in place.
4. Place window in front of target.
5. Adjust target emissivity until same apparent target temperature without window is found.
6. When using IR windows in this mode, enter the product of the target emissivity times the window transmittance for emissivity in your IR camera.
7. Mark the calculated emissivity setting on the IR window labels and ensure that all personnel using this calculation fully understand the procedure used.
8. The major caveat here is that the target reflected apparent temperature, the window reflected apparent temperature, and the window temperature must all be equal.

Note: 
This is a very popular method in use in the field today, particularly as the majority of IR cameras do not have the ability to adjust the optics transmission onboard the actual camera, but do however allow you to adjust the emissivity to obtain fairly accurate results using this methodology.

Method 3: Using IR camera reporting software:

1. Using electrical tape mark a low emissivity target onto a coffee cup and fill the cup with hot coffee.
2. Set the transmission rate to 0.99 and the emissivity to 0.95.
3. Take an image of the coffee cup measuring the temperature at the emissivity target.
4. Place window in front of target.
5. Take an image of the coffee cup through the IR window measuring the temperature at the emissivity target.
6. Save both images into your reporting software
7. Calculate the IR window transmission by adjusting the transmission rate within the reporting software on the image taken through the IR window until the temperatures read the same as the image without the IR window.
8.  Mark transmission rates on IR windows.

Return