Leak Evaluation

Leak evaluation is a critical test for confirming the integrity of welded joints on storage vessels, particularly tank floor and shell-to-floor welds where product containment is essential. QMS Asset Integrity provides NATA-accredited leak evaluation using differential pressure box (vacuum box) techniques.

This method is a requirement under API 650 (Welded Tanks for Oil Storage) for floor weld inspection and is widely specified for new-build tank acceptance and in-service tank floor assessments. Our technicians are experienced in conducting leak evaluations on above-ground storage tanks across the oil and gas, petrochemical and chemical storage sectors.

The differential pressure box test is a sensitive, practical and non-destructive method that provides immediate, visual confirmation of weld leak-tightness - essential for environmental compliance and product containment assurance.

A transparent vacuum (differential pressure) box is placed over the prepared weld area after applying a soap solution. A vacuum pump reduces the pressure inside the box, creating a pressure differential across the weld. If through-wall defects are present, air is drawn through the weld from the atmospheric side, producing visible bubbles in the soap solution that clearly identify the leak location.

The test pressure differential and hold time are maintained in accordance with the applicable code requirements. All indications are documented and the weld is assessed for acceptance or rejection.