Piggable Pressure Isolating System For Untapped Live Onshore Pipelines

In a perfect world every pipeline repair or maintenance site would just happen to have a valve on either side to use to isolate the work site. It is not a perfect world but the good news is that help has arrived. With the advent of new communications systems and piggable pressure isolation tools, that isolation capability now exists.

In other words, it is now possible to have an internal temporary “piggable valve” placed at any location (or locations) on a pressurized onshore pipeline at any time.

Pressure isolation - isolating the work site from the pipeline content under pressure using remotely controlled (tetherless) piggable plugs - is quickly becoming the norm for allowing repairs, or other work such as modifications or tie-ins, to onshore pipelines.

These tools, such as the Lineboar Piggable Valve™, allow repair and maintenance to take place without blowing down, evacuating or depressurizing the onshore pipeline, and without welding on or cutting a hole into the line using hot-taps or stopples. In other words, both the upstream and the downstream of a pipeline repair can remain at operating pressure, with the work site only needing to be evacuated of content.

Use of such tools is the equivalent of placing a valve at any point in the pipeline, without intervention into the pipe, without depressurizing or evacuating large sections of pipeline, and without leaving any trace that the tool/valve was there once the operation is complete.

Operating Mechanism
The concept is relatively simple. A tool that looks and pigs much like any ILI tool, but can also be actuated so that it transforms into a “plug“ which forms a complete pressure seal between the work area and the content in the line.

This “plug module,” along with a communication system in a separate housing attached to the plug module, is inserted into the launcher and pigged to the work site (or two systems which are pigged in so that they straddle the work site). Once the module is stopped at the desired location (see example in Figure 2) an operator sends a signal to the tool instructing the plug module to “set.”

This instruction is sent via a tetherless, through-wall, real-time control and communication system that can send data through ground cover and the pipewall. It is also able to monitor pressures in real time on each side of the tool during the operation.

Upon receiving the instruction from the operator, the tool begins to set itself using an internally powered mechanism that causes the plug module to contract.

As the entire module contracts, a set of segmented gripping wedges ride up a ramp until they engage the pipewall. As the tool continues to contract, the pressure plate at the end of the tool moves toward the ramp, with a sealing element between them. This compresses the sealing element which causes it to extrude until it, too, engages the pipewall. Once set, greater differential pressure across the tool transfers longitudinal pressure circumferentially, maintaining the seal by using the difference in pressure to continue to contract the plug module. At this point, the tool is set and is therefore isolating the content under pressure on one side from the work site on the other side of the tool.