Using a fluorescent leak detector correctly goes beyond just “spray and wait.” In this complete guide, we walk through each step along with additional tips and common mistakes that can compromise inspection results.

Step 1: Surface Preparation and Cleaning

Before anything else, the welded surface must be thoroughly cleaned of oil, grease, dust, and welding residue (such as slag or surface oxide). Any contamination on the surface can prevent the liquid from penetrating fine cracks or even mask the fluorescent glow, causing a real leak to be missed.

Common mistake: Incomplete cleaning or using solvents that spread grease across the surface instead of removing it. Always use a clean cloth and, if needed, a suitable industrial solvent, and let the surface dry completely.

Step 2: Even Application of the Product

Spray the product from an appropriate distance (typically 20 to 30 cm) evenly across the entire length of the weld line. Incomplete or uneven coverage can leave part of the weld improperly inspected.

Common mistake: Spraying too thin a layer or only covering spots suspected of having issues. It’s recommended to cover the entire weld length, not just suspicious areas, since many leaks appear in unexpected locations.

Step 3: Proper Dwell Time for Penetration

After spraying, the liquid needs sufficient time to penetrate cracks and pores through capillary action. This time depends on the part’s thickness, the type and likely depth of the defect, and ambient temperature, typically ranging from a few minutes to several dozen minutes.

Another important factor is the position and angle of the weld. For welds at the bottom of tanks (such as the floor of a transformer tank), gravity assists penetration, and a shorter dwell time is usually sufficient for the leak to appear. However, for welds higher up or on vertical surfaces, the liquid tends to run off, making penetration slower and more difficult; in these cases, an adequate amount of product should be applied (reapplying if necessary), and more time should be allowed for full penetration.

Common mistake: Applying the same fixed dwell time to all welds regardless of their position. Rushing the inspection of upper or vertical welds is one of the most common reasons real leaks get missed in practice.

Step 4: Inspection Under UV Light

Place the surface under UV-A light (typically around 365 nanometers) in a low-light or dark environment, and slowly move the lamp along the entire length of the weld line. The leak location will appear as a yellow-green glow.

Common mistake: Performing the inspection in daylight or a brightly lit environment, which reduces the apparent intensity of the glow and causes small leaks to be missed.

Step 5: Recording and Marking Identified Leaks

Before cleaning the surface, mark or record the exact location of each identified leak (with a marker, photo, or coordinate notes). This documentation is essential for the repair stage as well as quality reporting.

Common mistake: Wiping the surface clean immediately after spotting a leak without properly recording its location, which can cause confusion during repair.

Step 6: Final Surface Cleanup

Once the inspection is complete and results are recorded, the remaining product is wiped from the surface. Thanks to its minimal-residue formulation, this step is usually quick and simple, but it should still be done with a suitable cloth or solvent to leave the surface completely clean.

نتیجه‌گیری

The accuracy of a fluorescent inspection depends not only on the quality of the product but also on carefully following each of these steps. Avoiding the common mistakes above is what separates a reliable inspection from a missed leak.