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