Ok Tedi Mining Limited
Inspection of Storage and Process Tanks
About this Project
Worldwide Tank Services was engaged to carry out external inspections to 22 miscellaneous storage and/or process tanks at the Mine Plant Location at Tabubil, PNG, and prepare a Report on the status of each tank in relation to its suitability for continued service, and conformance with API 653
Worldwide Tank Services attended the mine plant site and initially established with our client, which tanks were the priority for inspection during this current visit (as it was not possible to inspect all of the tanks during the one visit). After resolving the scope of inspection, Worldwide Tank Services carried out the individual inspections of each of the 22 tanks, then prepared a detailed Report, supported with incidental photographs and Code references, to present to the client.
Included in the Report were Worldwide Tank Services’ recommendations for future actions by the Operator, based on 3 scenarios:
- For immediate action required maintain serviceability and integrity
- For short term actions required to maintain serviceability, integrity and Code compliance
- For medium to longer term actions required to bring tanks into Code compliance, but tanks are suitable for continued service without compromise to integrity
A proposal was prepared for our client, which included a detailed description of the circumstances that led to the leak, a proposed scope of works for the remediation process, and an associated Timeline Schedule. On acceptance of the proposal, Worldwide Tank Services managed all facets of the project, including planning, procurement, mobilisation and execution of the Works. Procurement and resources allocation were shared between RNO and WTS, to ensure the most efficient utilisation of resources, and to manage project costs most effectively.
The detailed site works, following mobilisation and orientation of resources, involved core drilling into the top of the concrete ring beam to allow initial installation of air bags, raising of the tank to a height of 2 metres, using the air bag methodology, abrasive blast cleaning of the underside of the tank bottom to ascertain the extent and presence of pitting corrosion, fitting, welding and NDE of over 500 patch plates to the bottom, removal and replacement of the foundation base course (which had been contaminated with acid), including inspection and repair of the secondary containment liner, painting of the repaired underside of the tank bottom, lowering the tank back to grade, ensuring correct orientation with connected piping, and final inspection.
Based on Worldwide Tank Services’ Inspection Report and recommended actions, our client was able to conduct repair or modification works to individual tanks, that required immediate action, and to plan for future works on remaining tanks, in line with scheduled plant shut downs and budget considerations.