Hdpe welding failure

[Ahmed Osman]

Hi,I have a leak in gre pipe underground after many failure repair trials we decided to replace the pipe with hdpe pipe between 2 buried fire valves and a hdpe riser to above grade level then steel pipe to the termination point . I made a successful hydrostatic test to hdpe but after connecting the hdpe riser to the steel pipe (the mechanical department didn't make supports to the steel pipe) the hdpe riser welding reducer separated(as shown in the picture).I want to know what is the main reason that caused the welding separation and the solution to avoid this again.
Thank you