Thermal Inspection – Case Study

In the following tests we will follow the performance of a drone equipped with a dual RGB/Thermovision camera.

This case study is made with the purpose of demonstrating the capability and practicality of drones use in Oil&Gas inspections, using state of the art thermal vision and drone equipment.

Our goal is to prove that we can detect leaks of hot fluids (60°C) like oil, in harsh environments.

Principal objectives:

  • Test #1 – Validating the accuracy of our equipment measurements
  • Test #2 – Validating the use case of drones in real life conditions for pipeline inspections by simulating a small, hard to detect leak in worst case possible scenario
  • Test #3 – Testing the limits of detection range, size and temperature in such applications

Although there is a noticeable difference between our tests and a real inspection, we have chosen a safer approach by assuming the hardest conditions”.

Table of contents & Location

Beregsău Mare

The location where we’ve carried out our tests.

View Map

Equipment used

Workflow

A workflow with key points was establish before the initial testing. The data and conclusions were taken on site, then post-processed with the appropriate thermal imagining software for a clear understanding of the data.

The temperatures from the radiometric images was taken using special tool of the software that measures the highest and lowest values in a specific area. In our images, the area is marked with a white circle, highest temperature with a red triangle and lowest temperature with a blue triangle. The point measured is indicated by the triangle tip.

Due to the height from which the images were taken, the boiler used to heat water was present in most of cases and can be seen as a bright spot on the right side of the images.

Test # 1

Validating the thermal camera measurements accuracy by comparing them to the classic and laser thermometer.

Methodology:

The above-mentioned equipment was used to measure, at the same time, the water temperature as it boils. The thermal camera was mounted on the drone and operated by the drone pilot. Classic and laser thermometer readings were taken manually. The test was concluded at ground level, 0 m altitude.

Results:

Classic thermometer  Drone  thermal camera  Laser thermometer 
98.3 °C  98.6 °C  104.4 °C

The error margin was very small, 0.3°C difference between the classic thermometer readings and the thermal camera readings mounted on the drone. Given the limitations of the laser scanner is this circumstance, the measured temperature was of the boiling pot exterior walls, not the water itself.

To verify the validation measurements, Test # 1 was repeated during the heating process after the water was replaced. The error margin was about the same, 80.5°C measured by the classic thermometer and 81°C measured by the thermal camera.

Conclusion:

Taking the data above in consideration, the measurements recorded by the thermal camera do coincide with the reality and therefore are valid.

Test # 2

Validating the use case of drones in real life conditions for pipeline inspections by simulating a small, hard to detect leak in worst case possible scenario

Methodology:

To make this test as close as possible to a real case scenario we have taken the appropriate measures thus making it a worst-case scenario where boiling water was spilled in a small area where a high level of vegetation was present. After that, images and measurements were taken with the thermal camera mounted on the drone at an altitude of 20m.

Results:

The results were concluded on site thus, a live inspection is possible, but for the purpose of this tests the images were interpreted with the appropriate software, making it easier to see.

Original, real time image - AInterpreted image - B

The image on the left (A) is uninterpreted, in it’s original from. Although they gray scale was our pilot choice at the time, there are a variation of color pallets to choose from to best suit the current application, depending on the circumstances.

The image on the right (B) was interpreted in post processing using software specialized in thermal vison. The advantage of doing so is that we can visually highlight the point of interest for a more accurate interpretation of the data. To keep things as scientifically as possible for these tests we locked visual interpretation scale to the same values for all our images.

The images above were taken before the water was spilled.

Before water spilling – RGB image - CBefore water spilling – Thermal image - C
After water spilling – Thermal image - DAfter water spilling – Thermal image - D

Our thermal camera ensemble is equipped with 2 sensors, RGB and thermal. For every thermal image shot, an RGB one is taken at the same time, thus giving us the ability to compare them. Using thermal images, we can clearly see where the water was spilled a red spot appears (D), but we can’t do the same on the RGB image(D).

Image D with the temperature measurements

Image D with the temperature measurements

The first measured temperature of the hottest spot was about 67°C. By the time the image above (D) was taken the temperature dropped significantly to 53.1°C. Adding insult to injury, the thermal radiation given up by the heated soil was partially blocked by the vegetation so it was harder to measure but fortunately it did not make it harder to see.

1 minute after the image D was taken - EImage E with the temperature measurements

After 1 minute the temperature dropped again by 6.2°C. Compared to oil and other metals, water gives heat away very fast and we can see that very clearly here.

Temperature measured at 50m - FTemperature measured at 100m - G

After another minute a third image (F) was taken, this time we raised the drone altitude at 50 m above ground. The measured temperature was 37.1°C. We did the same thing after 40 seconds image (G) but this time at the altitude of 100 m where the temperature measured was 32.6°C.

Note: The bright spot on the right side of the images was our boiler where we heated the water.

Conclusion:

The location where the water was spilled could be see and measured even in those harsh, absolute worst-case conditions. We also observed that the heat of the water alone was not giving us more than few minutes to future conclude our testing and that we needed a more persistent source of heat. The test was a success, our camera was able to detect and measure the water spilling.

Test # 3

Testing the limits of detection range, size and temperature

Methodology:

On our previous test we concluded that using water as a source of heat was not optimal, thus we changed it and used the empty pot as a source of heat, with a high and constant temperature. To push our thermal equipment vision even further we decided to place in under a tree.

Measurements were also taken with the pot placed in high vegetation area with a clear view of the sky. The tests for both pot placements were made at an altitude of 105 m and ground measurements were taken for reference.

Image D with the temperature measurements

Pot placement under a tree

Measurements were also taken with the pot placed in high vegetation area with a clear view of the sky. The tests for both pot placements were made at an altitude of 105 m and ground measurements were taken for reference.

Results:

Using the laser thermometer, we found that the initial pot temperature was 80.8°C. For a more accurate testing that resembles to a real-world case scenario we let it cool down below 65°C.

The measurements of the pot placed under a tree came inconclusive, although we were able to visually spot and locate it, the tree blocked most of the thermal radiation thus giving us a lower temperature reading of 30.2°C.

Image D with the temperature measurements

The pot was detected under the tree and it shows as the hottest point in the perimeter of the tree

Image D with the temperature measurements

Zoomed in image with a different color palette to enhance the visibility

Nonetheless, the results surprised us. We didn’t expect to see or detect the pot at all in those conditions and even more from an altitude of 105 m.

We continued with our tests and moved the pot a few meters away from the tree, in an open area with vegetation. From the images taken with the thermal camera at an altitude of 105m we identified the presence of the pot as a second bright spot that can be see on the left side.

Without the potWith the pot
Zoom - Without the potZoom - With the pot
Image D with the temperature measurements

Pot temperature measured from 105m

The measured pot temperature given by our thermal camera at 105m above the ground was 63.3°C

Image D with the temperature measurements

Live view of the thermal camera – 8x Zoom at 100m

As it can be seen from our pilot live view of the camera, the 8x zoom allows him to see even the shape of a 60 cm pot from a height of 100 m.

Image D with the temperature measurements

Image taken at 174m above the ground

The image above was taken with the purpose of testing the thermal camera resolution limits to see if and how a boiler with a diameter of 60cm shows on an altitude of 174m. It can by observed as a bright spot in the vicinity of the center of the image.

Conclusion:

The pot was identified and precisely measured from an altitude of 105 m. Even with the tree as an obstacle in the way, blocking most of the heat radiation, we were able to spot the location of heat source. The final image demonstrated one again the capabilities of our equipment, exceeded expectations and making this test a success.

Final Conclusion

We successfully validated the measurements taken with the drone thus demonstrating its detection capabilities.

  • In the first test we demonstrated the 0.5°C accuracy of the camera
  • The simulated leak was clearly identified and measured, as shown in Test #2
  • The equipment exceeded our expectations being overqualified for this application

Although the test was made at an altitude of 105 m with a point of interest in the scale of centimeters, in the real world the flight will take place at the altitude of 70 m and the oil leaks are in the scale of meters. Seeing and demonstrated by our tests, that the thermal camera can sense changes in temperature at a much smaller scale than the actual use case, we can safely conclude that the equipment is more than capable of detecting oil leaks.

The use case of drones in inspections offers more benefits then then ones mentioned so far, including time savings, high efficiency and accuracy, low complexity, data quality and the most important one in this industry: safety. Drone inspection do not require human intervention and eliminates every risk associated with it.

Taking all the above in consideration, drone technology offers quick and easy identification with unbeatable accuracy and high-quality data output being indeed a viable option.

Other thermal applications

Full radiometric thermal maps

Radiometric images can be fused into a radiometric orthomosaic, which is a larger map in which every pixel contains the temperature data.

Non-radiometric cameras output images that highlights relative temperature differences, this is not very reliable and can only display hot spots with no data.

Surface pipeline defect detection

Although in the visible spectrum this hot-water pipeline is completely without defects, the measurement of thermal camera shows that on the left hot-water pipeline there are a series of thermal bridges resulting in thermal losses.

The combination of visual and thermographed inspection using drones can discover a series of potentially hazardous problems before they become dangerous or financially demanding.

Underground pipeline leak detection

A hot-water pipeline heats the surface of the ground and, therefore, can be detected by a thermal camera located on the drone. Using this camera, areas can be detected where the pipeline is broken or where the penetration of hot water heats up the affected earth.

A traditional camera does not detect defects to internal heat insulation and the escapes of media below the surface of ground.

High voltage distribution lines

Transition resistance on the high-voltage distribution line leads to local heating of the stated joint. This problem results in energy losses and can result in fire breaking out in the future.

Easy, contact-free determination of the allocation of the temperature field on the surface of the measured body.

Security applications

The infra-red radiation can also penetrate through smoke. The thermal cameras enable to detect people through smoke or fog.

Another relatively less well-known fact is that infra-red radiation partially penetrates through undergrowth.

Photovoltaic power plants

A thermal image of a power plant with failure detected (hot spots) produced using a thermal camera.

In the IR spectrum, hot spots are significantly reflected on the thermal image (termogram) by contract colouring towards the surrounding.

Roof inspections

The thermal bridge on the roof of the building results in significant thermal losses.

Many places on flat roofs can be the source of defects (contact of the roof with the attic, penetration through the cover, inflows, etc.).

Questions?

Don’t hesitate to contact us!

+40 724 339 757
office@skylinedrones.ro