A BARREL OF OIL 55 GAL. WAS ON BARREL RACK WI8TH DRAIN VALVE AT APPROX 45 DEGREE ANGLE. HE TRIED BY HIMSELF TO TURN DRAIN VALVE DOWN CAUSING A RUPTURE OF LEFT SIDE JUST ABOVE GROIN. DR. SENT H IM BACK TO WORK (NO HEAVY LIFTING) MAY HAVE PROBLEM LATER.