MAINTENANCE CREW WAS INSTALLING A NEW RUBBER PIPE. HE OFFERED TO HELP AND POSITIONED HIMSELF SITTING ON TOP OF THE 20-40 BIN, GRASPING THE 8"" PIPE AT THE BOTTOM. WITH 3 OTHER WORKERS THEY AT TEMPTED TO RAISE THE VERTICALLY-ORIENTED PIPE, BUT REQUIRED ADDL. POSITIONING TO FIT IT ONTO THE BIN FLANGE. AS THEY LIFTED, EE FELT A ""POP"" IN HIS SHOULDER AND A SEVERE PAIN.