The Broader Opportunity from Thermal Imaging

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The Broader Opportunity from Thermal Imaging

For more than 20 years Thermal Imaging (TI) has been used very successfully for monitoring electrical substations and switch yards, transmission lines and some other electrical and mechanical gear. This has mostly been carried out by contractors due to the cost of the TI camera but this cost has been steadily reducing. In the last 5 years a much larger number of organisations have purchased TI cameras. For some it has been just an interesting toy that stays in the cupboard most of the time but many others have found extremely valuable uses for Thermal Imaging. Often these applications for TI are discovered in diverse and unanticipated areas. An example is the discovery of sediment in the warm pipe at the right. As TI cameras are so broadly useful in understanding equipment condition and they are now becoming small, cheap and easy to use, they can start to be considers as a generic inspection tool for electrical and mechanical maintenance people.

If Thermal Imaging cameras are going to be used more widely by non specialists, then the first thing to consider is some safety rules. The main problem is the camera operator focusing too much on the TI screen and not enough on the local hazards. The standard rule is to select a safe observation location and do not walk while using the camera (unless under a procedure or after a job safety analysis). This rule will avoid issues with trips and slips and other environment hazards such as mobile equipment. There are also safety rules for electrical people when inspecting or working around live electrical equipment (Live Electrical Equipment Thermal Imaging Safety Rules) (Click on Link).

Resulting Failure from non-repaired Hot Joint

Use of a Thermal Imaging Camera – The easiest way to learn how to use a thermal imaging camera is to get instruction from an experienced user. It will typically only take 30 minutes instruction to learn the initial basics of use. If this is not available then you need to read the camera operating manual. The manual should also be used to learn the finer points of camera function and how to adjust these settings. Basic of operation of a TI camera is given below. At least one person per site should attend formal Level 1 Thermography training.

Focusing the camera
Adjusting the displays maximum and minimum temperatures if item of interest is outside the standard range
When a problem or something of interest is found, freezing the live image
If required, recording maximum temperature and temperature difference, details of the equipment item, a description of the fault/issue and any required follow-up actions.
Storing images (usually take a digital camera image as well as thermal image)

It is suggested to always take a digital photo along with a thermal image, as it significantly helps with the later analysis of the thermal image. If it is possible to confuse the item with a fault with other similar items. Often a second digital image from a stand back position can help eliminate any confusion. The thermal image and the digital images can be easily matched later using the time recorded on the photo and TI files.

A Thermal Imaging contractors aim is to create a fancy report of all the problems and issues found. This is not so important for many in-house applications for TI cameras. Often equipment faults can be identified, repaired and verified OK quickly as a part of the inspection process, so creating a report from the image is just extra work. It is still good practice to download the relevant captured images on a PC under the work order number so they can be identified and reviewed later. They are useful as maintenance history or for developing case studies. When the fault can’t be repaired immediately, then at least a basic report is required that contains the full details. This is so the issue can be followed up later. The TI cameras usually come with reporting software but another option is just inserting the images into an MS Word file. Where the camera is being used to do routine monitoring of an items temperature or differential temperature, then the image is not usually stored unless a defined alarm level is reached.

Understanding Temperature Patterns - Finding potential problems in equipment with a Thermal Imaging camera requires little training as people naturally are very good at recognising differences in visual patterns. The colours in thermal images make problems stand out and a lot of the analysis is seeing colour differences in things that should be similar. The better you understand the equipment the more likely you will spot a fault. It helps when trying to understand these patterns to have some understanding about Temperature and Heat (Click on Link). Thermal Balance and Heat Sources are two issues that need to be thought about when interpret thermal patterns.

In a stable environment all temperatures equalise. There has to be a heat source to cause a temperature profile (variation along a line). If there is no heat source inside an item, then to measure a temperature difference the heat must be supplied externally eg. externally from the sun. The thermal balance of the object you are measuring has to be upset to see a temperature pattern. If you were trying to measure the level of a tank (see above) but the tank was in a temperature controlled room, you would not see an external pattern if the tank liquid and walls had reached thermal balance. The top tank images to the right has a slightly warm fluid that easily identifies the tank level. The thermal image also show one of the tanks has a significant level of sediment build up. The lower tank has been heated by the sun but the fluid can't be heated quickly so the cooler surface identifies tank level.

Heating from the sun or the normal variation in daily temperature is often enough to upset the thermal balance and create a temperature pattern. If your monitoring is relying on this effect, then you should always consider whether the item is in thermal balance when you see no temperature pattern eg tank shows no thermal level indication. Where the object being measured has an internal source of heat or cold then monitoring is easier. An example of an internal source of heat is a poor electrical connection where the resistance to the electrical current flow generates heat. If the heat source in an object is very small, it is often better to measure before sunrise or after sunset to eliminate the effect of the sun.

Don’t Limit Inspection Scopes Too Much – As suggested in the opening paragraph, it is very common when people to start using Thermal Imaging cameras to find faults in equipment and locations that they never expected. You should make sure do not miss these unexpected opportunities. Whatever the scope of a thermal imaging job, at each location you visit, do a quick overall scan of the whole area. Record any temperature pattern that appears unusual or may be of significant interest to others. This does not necessarily have to be done when you arrive in an area and can often be done during minor waiting time or during the inspection work or when you are in a better location to do an overall scan. This process can significantly add to the value of the inspection. If no defects are found, the time involved at each area should be less than 20 seconds. If you can’t interpret the temperature patterns identified or what the equipment involved is, ask for the assistance of someone who knows the equipment better. If you are not sure if the temperature pattern represents a real problem, the images can be added as ‘items of interest’ at the end of a report for others to look at.

Justify Buying a TI Camera - Electrical sections should have no problems justifing buying a cheap TI camera, even if it is just to check repaired faults found by their normal Thermal Imaging Contractor. For mechanical guys it is usually just picking one proven application such as conveyor inspections, furnace/ boiler insulation/ refractory checks, checking delamination in rubber lined pipes and energy efficiency checks. See below for some examples of faults found. Once you have the TI camera, the opportunity is to have everyone doing routine inspections to use it at least monthly as a standard inspection tool.