Lacks of penetration, pores, etc. often formed upon socket welding of polypropylene pipes adversely affect the weld strength. At the same time, welding is allowable at a positive ambient temperature. We present the results of studying weld strength for conditionally divided zones along the length of socket welded joints obtained at different ambient temperatures and various welding modes. At a negative temperature of ambient air welding of polypropylene pipes PPRC PN10 63 × 5.8 is carried out according to the technology developed at the Institute of Oil and Gas Problems SB RAS. Indicators of the strength of socket welding are obtained in tensile tests of blade specimens and ring specimen testing for shear by compression.