PSI - Issue 60

Harikrishna S et al. / Procedia Structural Integrity 60 (2024) 700–708 Harikrishna S / Structural Integrity Procedia 00 (2019) 000–000

702

a refractory castable material (insulyte-7) and acid resistant brick lining (230mm thick) is provided over the same on all faces. The pit is closed by RCC slabs of 250mm thick. Major portion of pit (less top 800mm ) is buried in the ground. The sulphur pit has a collection chamber on one of its ends. The layout is shown below.

Fig. 2. Schematic layout of SRU-II sulphur pit.

As per extant practise, the sulphur pit must be inspected in detail every 4 years during a Turnaround of SRU and repair works shall be carried out. An outage of same was planned by 1 st quarter of 2022 for replacement of steam coils of pit and was opened accordingly for field assessment. The assessment was carried out in two phases. a. Visual Inspection b. Non-Destructive Evaluation (NDE). 3.0 Visual Inspection Visual inspection of pit was carried out in first phase. The following observations/concerns were noticed. Photographic evidence of distress locations was also collected which is reproduced below. • Serious bulging was noticed on acid resistant brick linings (both sides) of the internal wall. • The brick lining was found detached/delaminated from RCC portion leaving gaps between lining & wall. • The joints between bricks on the walls were found damaged at multiple locations having big perforations, with suspecting Sulphur intrusion through the brick layers. • The precast slabs over the pit were also found damaged due to sulphur vapour intrusion/ deposits from sulphur vapour. Spalling of concrete was also noticed and reinforcement rods were also found exposed on bottom portion of slabs. Sulphur patches were noticed on bottom of cover slabs leading to abrasion of cement plaster & exposure of aggregates.