Foaming method for thermal insulation layer of polyurethane foaming thermal insulation pipe

The invention belongs to the field of manufacturing of polyurethane foaming thermal insulation pipes, and particularly relates to a foaming method for a thermal insulation layer of a polyurethane foaming thermal insulation pipe. The foaming method for the heat preservation layer of the polyurethane foaming heat preservation pipe comprises the following steps that firstly, compressed gas is introduced into a material injection pipe, and the material injection pipe is used for injecting a foaming material into an inter-pipe annular space between an inner pipe body and an outer pipe body of the polyurethane foaming heat preservation pipe; 2, two foaming components needed by polyurethane foaming are pumped into the material injection pipe, and the foaming material is pushed into the inter-pipe annular space through compressed gas. The problems that in the prior art, when a polyurethane foaming heat preservation pipe is manufactured, a heat preservation layer is prone to cavities, and operation efficiency is low c