Failed High Density Polyethylene

1

• Failed High Density Polyethylene
• (HDPE) Water Line Pipe Joint

During a Hydrostatic Test, an HDPE Pipe to
Flange Joint Failed. The Joint Flange Had Been
Welded to Other Piping Sections and Subjected to
Hydrostatic Tests Prior to the Failure Developing.
2
On the Failed Joint, the Flange Inside Surface
Weld Roll Back Beads are Flat and Triangular.
In contrast, Non-Leaking Pipe to Pipe Joints have
Symmetrical and Rounded Roll Back Beads.
The Failed Flange Joint Roll-Back Bead Has
Multiple Folds. The Flange Joining Temperature
Was Low and the Material Did not Bond.
The Failed Flange Joint Fracture Surface Is
Flat-Non-Ductile.
3

• Findings
• The Joint Failed Due to Incomplete Fusion
  Between the Pipe and the Flange.
• The Maximum Pipe Manufacturer Misalignment
  Guidelines Should Have Been Stringently Followed.
• The Weld Roll Back Beads Must Be Round.