The refined oil pipeline of the Longchang Branch of the Southwest Pipeline is a dual-line parallel pipeline that commenced operation in September 2002. It transports diesel and gasoline with a design pressure of 1.8 MPa and a pipe diameter of 168 mm. The steel pipe grade is X52, with a wall thickness range of 5.6 mm. The minimum radius of curvature for hot-bent bends is R=1.5D. There is one station and one oil depot valve chamber, and all stations lack pig launcher and receiver systems.

The Longchang Branch refined oil pipeline has been in operation for a long time and has not undergone pigging or internal inspection operations, posing high risks to pipeline operation. This time, the ultrasonic internal inspection of the Longchang Branch involved series-connected gasoline and diesel pipelines for internal inspection operations, with pigging and reception both conducted at the Longchang Oil Transportation Station. The inspection work mainly included process modification operations (at the Longchang Oil Transportation Station and Longchang Oil Depot), pipeline pigging operations, pipeline inspection operations, and restoration of process modifications. Among them, process modification operations were carried out during pipeline shutdowns. After modifications, pigging and inspection operations were conducted using diesel media during branch line shutdowns. The inspection operations were carried out using the pumping system after the process modifications.

During the preparation period, the T-ALL Inspection Longchang Branch team conducted detailed site surveys with the owner to identify risk points on the line, fully assess possible situations encountered by the pipeline pig and inspector during operation, and formulate corresponding solutions for potential issues during the operation to ensure the successful completion of pigging and inspection.

Prior to the operation, the T-ALL Inspection Longchang Branch team conducted multiple safety education and training sessions to strengthen employees' awareness of safety risks, ensuring that everyone understands and prioritizes safety. At the same time, they further confirmed and verified the construction plan, operation tickets, flowcharts, and the feasibility and accuracy of process modifications. Additionally, they made reasonable task arrangements for employees on duty during the internal inspection period, assigning specific responsibilities to individuals to ensure that they performed their duties safely and orderly.

During the operation, the T-ALL Inspection Longchang Branch team adhered to the principles of safety first, high efficiency, and high quality, prioritizing safety production. They ensured strict risk assessments before each process began, operated strictly according to the operation tickets item by item, fulfilled safety responsibilities in all aspects, and ensured the safety and reliability of the entire operation process.

In this inspection operation, T-ALL Inspection worked closely with the Lanzhou-Chengdu-Chongqing Branch Company and continuously innovated based on previous experience. On-site, by running half-coated foam pigs, fully coated foam caliper pigs, magnetic steel brush caliper pigs, magnetic steel brush pigs, and simulators, they monitored data such as pressure, flow rate, and pump speed during operation to ascertain pipeline conditions. Ultimately, they successfully operated the inspector, ensuring the completeness and validity of the inspection data, and accumulated valuable field experience for subsequent similar projects.