METHOD FOR BUTT WELDING OF PIPES OF BUILT-UP POLYETHYLENE Russian patent published in 2003 - IPC

FIELD: method for butt welding of pipes of built-up polyethylene for using these pipes in industrial underground construction of pipe-lines. SUBSTANCE: end surfaces of pipes are spatially melted by means of the working surfaces of a shaped heating element provided with radial teeth. The temperature of the heating element is higher than 420C, but lower than 450C. Increased toothed end surfaces of the pipes are formed, whose continuously melting from the vapor or gas phase to the phase of thermoelasticity. The toothed surfaces of the pipes get engaged with each other during the subsequent process of joining at a pressure of 0.10 to 0.40 H/mm² so that the-ends of the teeth of the end surface of one pipe becomes engageable with the tooth roots of the end surface of the other pipe. The phase of melting of these layers causes an effect of mixing of the melt by means of turbulent motions in the engaged end sections of the teeth with formation of spatially distributed weld with an increased surface of engagement. In the process of welding the pressure remains uncharged until the area of joint is cooled down to the ambient temperature. EFFECT: provided butt welding of built-up polyethylene with formation of a continuous weld of a high strength. 2 cl, 3 dwg