The quality problems of PE pipes and fittings are generally caused by irregular operation during transportation and construction. The causes of quality problems are as follows:

(1) Polyethylene pipes are dragged and thrown by Tora during transportation, handling and storage, resulting in damage to the pipes;

(2) There is no roller bracket used in the welding and trenchless pullback process of PE pipe straight section, resulting in scratches on PE pipe wall.

(3) No shelter measures such as sun protection and rain protection are taken to protect the pipes stored on site, which will affect the performance of the pipes and shorten the service life of the pipes.

(4) Pipeline after trench excavation is not backfilled in time according to regulations, and is covered and soaked by construction waste and rainwater for a long time, which affects the safety of pipeline operation and service life.

(5) The quality of pipes and fittings does not meet the requirements or the use of outdated pipes and fittings.

Quality Problems of Hot Melt Welding Joints

There are many quality problems in PE pipe hot melt welding joints, such as asymmetrical curling, excessive staggered edge, bubble depression and pitting on the weld surface.

The reasons for the above problems include:

(1) In order to save the cost of equipment, semi-automatic welding machine is used and welding parameters are not met, such as too large dragging pressure and too short cooling time.

(2) Full automatic welding machine with unqualified welding performance;

(3) Due to the different properties of PE pipes (such as thermal stability) from different manufacturers, the parameters of hot-melt welding machine are not consistent with the characteristics of pipes.

(4) Use incompatible pipes for welding, such as butt welding between PE80 and PE100;

(5) In order to catch up with the construction period, the constructors shall work under damp and other bad weather conditions.

(6) The required hot-melt fixture and roller bracket are not used during welding, and the quality of the counterpart does not meet the requirements.

(7) Welding machine operators are on duty without professional training and certification.

Quality Problems of Weld Joints in Electrofusion Joints

The main quality problem of PE pipe fused joints is "false welding". There are six reasons for this:

(1) When the fused sleeve fittings are connected to the PE pipe at both ends, the special fixture is not used to keep the interface of the two PE pipes "concentric". Forced assembly results in uneven interface clearance and reduced interface fusion area.

(2) The fused sleeve pipe fittings are not the same manufacturer as PE pipe fittings, and there are compatibility problems between the pipe fittings and accessories.

(3) Scraping oxide layer or uneven scraping resulted in non-roundness of PE pipe ports, uneven interface clearance and virtual welding.

(4) Moving the connector during the fusion process and cooling time;

(5) In oder to be in a hurry, the cooling process is not carried out in the natural state, with water or forced air cooling.

(6) Insertion length of tube into fused tube is insufficient, which may lead to de-welding.

Other Quality Problems

(1) Pipeline backfilling did not lay warning belts according to regulations, and groove depth did not reach the standard;

(2) If the PE pipeline is backfilled with yellow sand and fine soil according to the regulations, the compressed pipeline covered with stones or sharp objects will easily leak at the interface, which will seriously threaten the safe operation of the pipeline in the future.

(3) After the discontinuity of pipeline construction, the pipeline mouth is not blocked or covered with water and soil in the process of construction backfilling, which may cause a large amount of impurities and rainwater left in the pipeline, affecting the safe and smooth operation of the pipeline in the future.