Apparatus and Techniques for Coating Pipeline Field Joints

摘要

An injection moulding apparatus has a mould tool that is positioned around a field joint of a pipeline to define a mould cavity. Two or more pumping chambers communicate with the mould tool. Each chamber is expansible to draw in molten polymer and contractible to drive the polymer into the mould cavity. Expansion of one chamber is synchronised with contraction of another chamber. The operation of supply and injection valves associated with the chambers is also synchronised, both with each other and with expansion and contraction of the chambers. In the embodiment described, two pumping chambers are defined within a common pressurising cylinder, in which the chambers are separated by a piston. The piston is movable within the cylinder to determine and to synchronise expansion and contraction of the chambers.

主权项

1. An injection moulding apparatus for coating a field joint of a pipeline, the apparatus comprising:
a mould tool positionable around the field joint to define a mould cavity; and first and second pumping chambers defined within a common pressurising cylinder and communicating with the mould tool, each chamber being reciprocally expansible in an induction stroke for drawing molten polymer into that chamber from a melt supply and reciprocally contractible in a compression stroke for driving molten polymer out of that chamber into the mould cavity in use; wherein expansion of one of said chambers is synchronised with contraction of the other of said chambers such that the induction stroke of one of said chambers coincides with the compression stroke of the other of said chambers.