CHALLENGE

LPG Storage Sphere Tank Constructional Weld inspection – Challenge; to reduce inspection times and costs, whilst improving on test sensitivity to the detection of both manufacturing defects and the early stages of in-service weld cracking.

During the long term operation of LPG storage tanks; high pressure, stress and product reaction with weld and parent material causes damage mechanisms including cracking.

Common conventional industry practice for the inspection procedure of LPG storage tanks (sphere or cylindrical design) is very time consuming, requiring the tank to be taken off-line and drained. The required pre-inspection internal cleaning of the vessel, and the erection of a full internal access scaffolding to facilitate surface preparation by blasting and internal inspection, proves very costly for obvious reasons.

SOLUTION

Integrity NDT Engineering offered Tank Fabrication Weld inspection carried out from the ‘external’ vessel surface by ultrasonic TOFD (Time of Flight Diffraction) technique. This very sensitive and fast inspection technique was adapted for long range inspections using the specially designed Integrity ‘I-Scan’ magnetic wheeled semi-auto scanner and 36m long umbilical cabling.

Scanning was carried out externally and without the need for access scaffolding using highly experienced IRATA Level 3 and Level 2 certified rope access technicians.

One of the main advantage of this system and approach being on-line inspection (the storage vessel is not required to be drained), massively reducing off-line times and costs.