Abstract: A joint assembly for a nonambient temperature pipeline which in a preferred embodiment is designed for low temperature service, comprising a slip-lock joint including inner and outer spool members connected with upstream and downstream pipeline segments, respectively, and contacting primary seals with sloping surfaces arranged so that as the pipeline temperature is lowered from ambient, the line contracts thereby causing the spools to move relative to each other and progressively increasing the tightness of the primary seal. During movement, a spring-loaded shear key locks in place in a shear key receiving slot, which is maintained after the initial cooldown of the pipeline. This maintains the tightness of the joint and accommodates any further contraction movements in the pipeline.