Apparatus and method for joining molecularly oriented pipe

A method for joining a first longitudinal section of non-corrugated molecularly oriented pipe to a second longitudinal section of non-corrugated molecularly oriented pipe to form a restrained joint between the first and second sections of molecularly oriented pipe, each of the longitudinal sections of molecularly oriented pipe being used in a municipal water or sewer line and having at least one plain, spigot end having a given external diameter and a mating socket end having a given internal diameter which presents an end opening having enough clearance to allow the plain spigot end of the first longitudinal section of molecularly oriented pipe to be inserted into the end opening of the mating socket end of the second longitudinal section of molecularly oriented pipe, the method comprising the steps of:

• inserting the plain spigot end of the first section of molecularly oriented pipe into the end opening of the mating socket end of the second longitudinal section of molecularly oriented pipe to a preselected depth;
• heating the mating socket end of the second longitudinal section of molecularly oriented pipe to about 80° C. so that the internal diameter of the mating socket end of the second longitudinal section of molecularly oriented pipe comes into contact with the external diameter of the plain spigot end of the first longitudinal section of molecularly oriented pipe, the second longitudinal section of molecularly oriented pipe being in a rubbery state after heating which allows the mating socket end of the second longitudinal section of molecularly oriented pipe to conform tightly to the external diameter of the plain spigot end of the first longitudinal section of molecularly oriented pipe without deforming the plain spigot end of the first longitudinal section of molecularly oriented pipe;
• and
• cooling the mating socket end of the second longitudinal section of molecularly oriented pipe to about 55° C., whereby the mating socket end of the second longitudinal section of molecularly oriented pipe undergoes thermal contraction to produce about an 0.5% interference fit with the plain spigot end of the first longitudinal section of molecularly oriented pipe, the interference fit resulting from the thermal contraction serving as the main source of restraint for the restrained joint.