BP Sangachal Terminal, Baku, Azerbaijan

Repairs to Crude Oil Storage Tank No 2

About this Project

During a scheduled tank inspection for the 125,000 m3 tank (96.5m dia x 20.5m high with external floating roof), significant corrosion was detected under the bottom plates, and particularly around the area just inside the concrete ring beam. Additionally, the floating roof seal had exhibited significant wear and degradation from its service, and required remedial action, and the floating roof, when in its lowered “out of service position” was not in its designed position, which allowed very large pools of water to reside on the roof, that could not drain per the intended design for roof drainage.

Worldwide Tank Services was engaged to provide Project Engineering, Management, Construction Management, and Site Supervision for the works required, including the engineering aspects, the Scope of Works, development of the Works Specifications and Work Packs.

Our client was reluctant to consider lifting such a large tank, which would be necessary for a complete bottom annular plate replacement, so Worldwide Tank Services devised a suitable strategy for replacement of sufficient of the defective bottom annular ring to provide the necessary structural integrity, as well as complying with the requirements of API 653.

Worldwide Tank Services ascertained that the corrosion that had occurred beneath the annular ring was caused by a combination of moisture entrapment in the drainage gully around the inner perimeter of the ring beam, as well as contact between rocks and the bottom of the annular plates, which provide a direct path for corrosive attack. Much of the intrusive moisture was due to water ingress beneath the annular plates form external weather influences Worldwide Tank Services was tasked to provide a suitable repair strategy to be incorporated into the remedial works program.

Our Process

Worldwide Tank Services developed the detailed scope for the remedial works, produced the detailed Works Specifications and Work Packs, and provided the Project Management, Construction Management, and Site Supervision of the nominated Works Sub-Contractor. The scope entailed replacement of sufficient of the defective bottom annular ring to provide the necessary structural integrity, as well as complying with the requirements of API 653.

During the course of the works, Worldwide Tank Services ascertained that the leak detection system and foundation drainage was not working correctly. The scope was revised to incorporate modification of the existing construction for each of the leak detection drainage pipes for correct functionality.

Incorporated into the Schedule was the removal and replacement of the floating roof seal, installation of additional drainage points on the floating roof, removal and replacement of the existing protective coating on the tank bottom, and replacement of the zinc anodes on the tank bottom, to ensure proper performance of the tank’s Cathodic Protection System.