Many costly failures in welded steel structures begin with early warning signs that often go unnoticed. In this article, we cover five common signs that indicate it’s time for a leak inspection.

1. Oil Stains or Moisture Around the Weld Line

If you notice even a small trace of oil or moisture around a weld, it could indicate an active leak that hasn’t yet grown large enough to be directly visible to the eye.

Quick fix: Thoroughly clean the surface and perform a fluorescent leak inspection with UV light at the earliest opportunity.

2. Unexpected Drop in Oil Level in Tanks (Such as Transformers)

If a tank’s oil level has dropped without a clear reason (such as maintenance or intentional draining), this is one of the clearest signs of a leak, even a very fine one, somewhere along the tank’s weld lines.

Quick fix: Systematically inspect the entire weld perimeter of the tank with a fluorescent leak detector to pinpoint the exact source of the oil loss.

3. The Structure Has Been Exposed to Continuous Pressure, Vibration, or Temperature Cycling

Structures that have experienced variable pressure, mechanical vibration, or repeated thermal cycles throughout their operational life are more prone to the growth of fine weld cracks, even if no defects were reported at the time of manufacturing.

Quick fix: For such structures, add periodic inspection (even without visible signs) to your preventive maintenance schedule.

4. The Weld Has Recently Been Repaired or Modified

Every time a weld is repaired or reworked, even partially, the likelihood of new defects (such as porosity or incomplete penetration) forming in that area increases.

Quick fix: After every weld repair, always perform a leak inspection before returning the structure to service.

5. The Structure Is Designed to Hold Pressurized Fluid or Gas

In any structure whose primary function is to contain a fluid or gas (such as tanks, containers, or pressure vessels), even the smallest leak can directly affect the system’s performance and safety.

Quick fix: For this category of equipment, treat leak inspection not as an optional step but as a standard part of the pre-operational quality control process.

Conclusion

Many of these signs aren’t alarming on their own, but together, they can signal a more serious structural issue. Recognizing them and responding quickly is the simplest way to prevent costly failures down the road.