Problems of mechanical composite pipe

1.Insufficient bonding strength

Because there is no metallurgical bonding interface between the two metals, the bonding strength is low, generally 0.2-0.3mpa.It is easy to peel off the inner pipe due to insufficient bonding strength.

2.Poor sealing of end bevel

The end bevel treatment of the mechanical composite pipe is a very key link. If the end seal is not good, it will not only lead to the peeling of the inner pipe and the outer pipe, but also affect the field butt welding.

The most commonly used end treatment is seal welding and overlay welding. The welding consumables of seal welding technology are less and relatively cheap. Although it has many years of experience and is mature, its stability is relatively cheap, and the requirements for field butt welding are high, which is greatly affected by the welding level of welders.

The welding consumables of overlay welding are more and the cost is more expensive，but it has good stability and high comprehensive safety.

3.Thermal collapse

Because of its low bonding strength, the mechanical composite pipe is prone to collapse under the condition of high temperature (about 200 ℃), which leads to the peeling of the inner pipe. In some projects, when the mechanical composite pipe is treated with 3PE external anti-corrosion treatment, some composite pipes suffer from thermal collapse due to high heating temperature, which brings great loss to the project.

4.Collapse during pressure relief

There is a interspace between the base pipe and the inner pipe. High pressure oil and gas enter into the interspace through the corrosion perforation point. When the pipeline is repaired with pressure relief, the inner layer collapses.