Abstract: A pipe plug apparatus and method for its use are described herein. A pipe plug is provided which includes a first portion, and second and third portions which radially extend from the exterior surface of the first portion so as to surround the first portion. When the plug is positioned in a pipe, liquid is introduced into the space as defined between the second and third portions, and as defined between the pipe interior surface and first portion exterior surface, so as to at least partially fill the space with the liquid.

Abstract: A die assembly for the extrusion of thermoplastic pipe from a plastic exhibiting an appreciable amount of memory and thus having an elongated heated portion defined by an elongated outer bushing ring with an inside diameter substantially equal to the nominal outside diameter of the pipe to be produced and an inner mandrel ring having an outside diameter smaller than the inside diameter of the bushing ring and disposed within the bushing ring to form an annular extrusion channel, the essentially straight portion of the extrusion channel defining the land length of the die and the width of the extrusion channel defining the die opening of the die, the improvement comprising a mandrel formed in two sections, including a longer upstream section, fixedly mounted in the die and having a fixed mandrel outside diameter and a downstream mandrel section removably mounted in the die as an extension of the upstream section and replaceable by downstream mandrel sections of equal length but different mandrel outside diamet

Abstract: In the extrusion of plastic pipe in which polymer flows from an extruder into a spreader cone, through a plurality of channels in a distribution plate and through a choke passage for blending the plurality of flow streams from the individual channels in the distribution plate to form the sidewall of an extruded pipe, improved blending and welding of the polymer flow is accomplished by incorporating in the outer wall of the choke passage a plurality of elongated cavities with each cavity diminishing in depth and width from its upstream end to reach zero depth and width as the passage stretches downstream across the line of polymer flow. In preferred embodiments the cavities are tear-shaped with wall space in between and overlap at least an end of the nearest passage on either side as viewed in the direction of polymer flow.

Abstract: A blend of polymer fluff, at least one dry additive and a slip agent is prepared by compounding the polymer fluff and the dry additive, introducing this mixture to a disc mill while simultaneously introducing the slip agent to the disc mill and thoroughly mixing the polymer fluff, additive and slip agent in the mill.