During TM3 roughing down yesterday afternoon,The vacuum gauges CG1 and CG1S stopped at 1.20 torr and refused to drop down. Leak detector was used to found where the problem was. LD was in rough detecting mode and showed 2.7xE-6 atm.cc/sec as base leak rate. Spray medium amount of helium to TM3 service top, and found this leak was on round panel of TM3 side wall. LR climbed to E-4 atm.cc/sec range on helium spraying. In my vie,One 10# socket head screw was not tightened properly after cameras job and caused this. The TCS was vented. The panel was took off and reinstalled. O-ring on the panel was replaced by a new one as well. Then TCS was pumped down again. The leak disappeared . All turbo pumps on TCS and TM3 were started successfully later. |