The live loading is optimized to maintain a seal at the upper packing set to less than 500 ppm leakage, minimize {HEAD ~ packing friction} from both the upper and lower packing sets, and seal the lower packing set during {TAIL ~ fire safety tests} 
The live loading is optimized to maintain a seal at the upper packing set to less than 500 ppm leakage , minimize { HEAD ~ packing friction } from both the upper and lower packing sets , and seal the lower packing set during { TAIL ~ fire safety tests }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL