Abstract: A multi-layer parison has a plurality of layers of main and auxiliary resins laminated with each other. An apparatus for forming the multi-layer parison includes a main resin extruding mechanism, at least one auxiliary resin extruding mechanism and a control unit for controlling the main and auxiliary resin extruding mechanisms so that the pressure for extruding the auxiliary resin is immediately increased and the pressure for extruding the main resin is gradually increased at the beginning of extrusion of the main and auxiliary resins.

Abstract: A break detector by which an internal pressure of a pipeline is detected and a changing rate thereof is detected and compared with a desired value and further, when the desired value is greater than the changing rate, a ramp output generates and is compared with the desired value and when the value becomes equal to same, a break signal is generated to cause fluid flow in the pipeline to stop, thereby serious pollution problems due to the occurrence of pipeline burst are prevented. The break detector according to the present invention can be used in poor environmental conditions and has high accuracy in operation thereof as well as simplicity and ease in adjustment, installation and maintanance regardless of the type of fluid flowing through the pipeline.