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Back Projection

A Back Projection is a method used on single feed cable sections to determine the distance (in feet) of a leak from an air source (or a bypass valve location). The Back Projection requires all of the information from the ZLP calculation, as well as a second pressure reading taken just beyond the ZLP defined search perimeter. Here's what you need to calculate a Back Projection:
  • Input pressure and flow rate at the air source
  • Pneumatic resistance of the cable per 1,000 feet
  • Zero Leak Projection
  • Air pressure reading at the first available location past the ZLP search limit

Back Projection Formula