Print Feasibility study of intelligent pigging in the ring main transmission line of Chattogram

Abstract

The project work is intended to establish the appropriateness of intelligent pigging as a single integrity assessment tool for the ring main natural gas transmission line of Chattogram city. For the purpose of the project work, previous cleaning pigging operations of the ring main line were reviewed. Significant portions where important structures/installations had grown up were identified. Records and information regarding the physical attributes and operational issues were collected from site visits, official documents and personal communications. Calculations were done to identify the limit of gas withdrawal rate at different operating pressures within the practiced speed limit of an intelligent pig. Calculations done are indicative of the ability of the ring main to allow an intelligent pig run. Alternates of intelligent pigging were checked for their appropriateness for adopting as an assessment tool for the ring main line. Review of previous cleaning piggings indicates existence of metal loss issue within the ring main line. This phenomenon is widely addressed by magnetic flux leakage (MFL) technology based metal loss intelligent pigging operation. An MFL based intelligent pigging will cost Tk 1,939.61 /meter on an average. Immediate rehabilitation of the ring main line would require Tk 39,518.76/meter, Tk 75,813.13/meter, Tk 46,839.52/meter and Tk 40,822.91/meter for segment 1, segment 2, segment 3 and segment 4 respectively. Assuming yearly 10% flat price escalation, these costs would be Tk 63,645.36/meter, Tk 1,22,097.80/meter, Tk 75,435.52/meter and Tk 65,745.71/meter for the segments mentioned above after five years. A qualitative risk analysis indicates that the intelligent pigging of the ring main line is a medium risk project.