Anomaly Description:
Complete separation of a 2” branch on a 4” header due to extreme corrosion underground.

Client Report:
5 random areas were excavated to determine the condition of 051-WP-12-4″-150K01 underground piping.

Visual inspection results are following:

• General and pitting corrosion of the main header, separate pits are up to 3mm deep
• Damage of drain nozzle from 2G-501,1B
• Significant general corrosion of vertical pipe sections
• Areas with through wall damage of heater tracer. Currently heat tracing is switched off
• Damage to insulation
• Missing sand in trays in accordance with UTL-DU-5084-TCO i. 8.10.5
• Damaged or completely missed piping protective coating
• Water in trays

In accordance with UT results minimum measured thickness of 4″ header is 3.6mm

Root causes:
The cause of general and pitting corrosion is the result of multiple coating damages and direct contact of piping with ground water.

Integrity concerns:
The operation of piping with a damaged nozzle is not allowable.

Clamp Design:
A straight line enclosure was designed with a 2” nozzle and welded flanged connection.
The design allows the client to reroute the failed piping and connect it with another flange connection to the leak sealing enclosure. This allowed for a normal process flow and the return of the line back to pressure. A strongback system was also designed should there be full circumferential failure to compensate should more deterioration take place underneath the clamp as well as weakening of the header pipe (due to the branch line that corroded away). The enclosure has been designed according to ASME v111 Div1 and ASME PCC2.

Seal:
PTFE Compound was injected into a precut sealing groove around the entire seam of the enclosure as well as around the pipe bores to create a successful seal.