ILI Solutions for Inaccessible Supply Lines

Many supply lines were simply never designed with in-line inspection in mind. 

Unlike transmission pipelines, which often incorporate permanent launchers and receivers, facility supply lines often connect tanks, pumps, process units, and loading areas without any dedicated pigging infrastructure. 

That design creates a very basic problem: 

How do inspectors get an in-line inspection tool into & out of the pipeline? 

Installing permanent launchers and receivers is one solution, but it can require substantial piping modifications, engineering work, line isolation, hot-work permitting, and a planned outage of the affected system. 

For a short supply line, those modifications can cost more than the inspection itself. 

Operators often turn to temporary access solutions. Depending on the pipeline configuration, these can include: 

• Temporary launch and receive traps 
• Removable spool pieces 
• Existing flanged connections 
• Specially engineered access points 

These arrangements can enable deployment of several inspection technologies, including tethered tools, conventional ILI pigs, and robotic systems. 

Where internal access remains impractical, operators rely on external NDT methods, such as external UT and guided-wave UT. 

But creating an opening in the pipeline is only part of the challenge. 

The access arrangement must provide sufficient space to insert the tool safely, establish the required flow conditions, control pressure, and—depending on the method—recover the tool at the opposite end. 

Another option is Dexon's Flexi-ILI Dolphin. Its free-swimming, bi-directional design allows it to be deployed through several relatively simple access arrangements, including: 

• Prefabricated launcher/receiver spools 
• Temporary flanged access 
• Direct drop-in deployment 

The Dolphin can reduce mechanical work while still providing high-resolution ultrasonic coverage of the pipeline. 

There is no universal solution. The right approach depends on the line’s geometry, operating conditions, available access, and integrity objectives. 

For difficult facility piping, tool selection and access strategy have to be engineered together. 

A pipeline may be perfectly inspectable from an integrity perspective, but if there is no practical way to get the inspection tool inside, the first engineering challenge is not defect detection—it is access.