Detecting a gas leak

Basic steps to gas detection

  • First adjust the focus. If the camera is out of focus, there is a risk of missing a gas leak.

  • The key to making the gas visible is enhancing the temperature difference between the gas cloud and the background. To obtain optimal contrast, try to find a suitable background by aiming the camera toward the target from different angles.

  • Use the Delta T feature to show areas where there is insufficient temperature difference between the background and the gas.

  • Using the High Sensitivity Mode (HSM) can improve the detection of gas leaks, especially when they are small or low in concentration.

  • By adjusting the temperature scale to temperatures around the background of the gas, you can make the gas appear more clearly.

  • Selecting a different color palette can make it easier to see the gas cloud.

  • The sensitivity of the camera can be controlled by changing the camera temperature range. A general guideline is to start with the lowest camera temperature range, but change if the image becomes oversaturated.

  • Motion of the gas, for example, caused by wind, makes the gas cloud easier to see.

Adjust the camera focus

It is very important to adjust the focus correctly. If the camera is out of focus, there is risk of missing a gas leak.

You can adjust the focus manually by using the focus ring, or autofocus by pushing the center of the Focus/Zoom button. See also section Focus.

Note

Applicable to the FLIR Gx models: You can only adjust the focus manually by using the focus ring.

Delta T

A higher temperature differential between the gas plume and the background will make the plume more visible on the camera screen. The background should be at least 2°C (3.6°F) warmer (or colder) than ambient temperature to provide sufficient contrast.

Use the Delta T feature to show areas where there is insufficient delta temperature.

  1. On the main toolbar, select Delta T. This displays a dialog box.

  2. In the dialog box, you can define the Delta T settings:

    • Turn on/off the Delta T feature.

    • Atmospheric temperature: The current ambient air temperature in the same general area as the gas leak.

      Note

      This setting is the same as for the measurement parameters, see section Measurement parameters. Any changes in the Delta T dialog will also change the corresponding measurement parameter setting.

    • Temperature difference: As a general guideline, set the temperature difference to 2°C (3.6°F).

  3. To close the dialog box, push the Back button.

High Sensitivity Mode (HSM)

High Sensitivity Mode (HSM) is a feature specifically designed for gas detection.

The HSM mode makes motion more visible in the image. This is achieved by comparing the information in two image frames, taken at different times, and removing all information that is the same. What remains will be items that have changed, such as a moving gas. HSM also amplifies this remaining information, which makes a moving gas cloud stand out more clearly.

It is possible to adjust the sensitivity of HSM in a number of fixed steps, with different combinations of time between the image frames and amplification. A higher sensitivity value will allow you to see smaller variations, but there will also be more noise in the image.

You will need to experiment with the sensitivity until you get a clear image of a verified gas leak.

General guidelines:

  • If you believe the gas leak is small or low in concentration, use a high sensitivity value.

  • For large gas leaks, use a low sensitivity value.

Using HSM

To activate the High Sensitivity Mode (HSM), select Image mode > HSM on the main toolbar.

Note

You can also assign the function Toggle HSM to a programmable button, see section Programmable buttons.

When the HSM mode is active, a slider is displayed. Use this slider to change the HSM sensitivity.

To change the sensitivity, do one of the following:

  • Move the joystick up/down.

  • Drag the slider by touching the screen.

Adjust the temperature scale

The camera continuously adjusts the temperature scale for the best image presentation. By manually adjusting the scale to temperatures around the background of the gas, you can make the gas appear more clearly.

For instructions on how to manually adjust the temperature scale, see section Thermal image adjustment.

Note

Manual image adjustment is not possible in High Sensitivity Mode (HSM) mode.

Change the temperature range

The sensitivity of the camera can be controlled by changing the camera temperature range. The selected temperature range also has an impact on the integration (exposure) time. The optimal temperature range setting depends on the thermal conditions in the scene.

A general guideline for gas detection is to start with the lowest camera temperature range, which gives the highest sensitivity.

If there are warm objects in the scene, the image may become oversaturated. If this happens, you should change to the next temperature range. With a too low temperature range, you risk to miss a gas passing in front of the warm objects.

To change the temperature range, do one of the following:

  • Push the Temperature range button and then select a temperature range by using the joystick or touching the screen. See also section Temperature range.

  • On the Settings menu, select Camera temperature range. This displays a menu where you can select the temperature range.