ITW entrance module and exit 1 module leak check on module service cap/top air to vacuum seals and module to tank flange  o-rings have been done. all seals and o rings are leak free to 0.0 xE-9atm.cc/sec except one leak ( to low E-6 atm.cc/sec) on ITW RV4 KF50 o-ring was found. It caused by a cross o ring surface scratch on KF 50 flange. the scratch was sanded and polished out. on second time leak check, it is leak free.