F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
F16L17/00—Joints with packing adapted to sealing by fluid pressure
F16L17/02—Joints with packing adapted to sealing by fluid pressure with sealing rings arranged between outer surface of pipe and inner surface of sleeve or socket
F16L17/03—Joints with packing adapted to sealing by fluid pressure with sealing rings arranged between outer surface of pipe and inner surface of sleeve or socket having annular axial lips
F16L17/035—Joints with packing adapted to sealing by fluid pressure with sealing rings arranged between outer surface of pipe and inner surface of sleeve or socket having annular axial lips the sealing rings having two lips parallel to each other