Isolate and Displace – The IsoPurge™

Client requested

The pipeline operator discovered long seam cracking under the Interstate highway and needed to replace the pipe with 1500’ of new pipe that was installed using a horizontal directional drill (HDD).   

Understanding the best solution

Their options to isolate the existing line for the tie in were to purge 35 miles of 20” pipe, or to use 4 split tee hot taps.  Rather than using these conventional methods the operator opted to IsoPurge the short segment under the highway.

Planning and delivery

Two IsoTools were launched 300’ apart and tracked into position (See Diagram 1).  The downstream IsoTool was parked DS of TOR A2, and the upstream IsoTool was brought into position between TOR A1 and TOR A2. 

Once in position the US IsoTool was set, and an Isolation Assurance Test was completed to verify the hold.  A nitrogen tube trailer was hooked up to TOR A2 and used to push the DS IsoTool into position DS of TOR B2, while displacing the product to on-site tankage.  The DS IsoTool was set, and also underwent an assurance test, after which the nitrogen was vented, and the mechanical tie in work could commence.

Vapor Tools were inserted US and DS of the cut and the new pipe was welded onto the cut.  To fill the empty pipe between the tools the oil that was initially evacuated was pumped back into the line from the frac tanks.  The IsoTool operators then opened to internal bypasses in both tools to equalize the pressure, and both IsoTools were unset.

Service completion report

The line was returned to Pipeline Control and the pigs were pumped to trap, where they were removed separately due to the length of the receive trap.

By purging one IsoTool against another the client avoided the use of line stops, and a lengthy purge, which safely and effectively reduced time and costs.