Plan 32


Injection of external source of liquid into the seal chamber


  • Reduce flashing or air intrusion across seal faces
  • Can maintain vapor point margin
  • Must be provided at pressure higher than the seal chamber pressure
  • Provides the best seal environment of all single seal plans

For use:

  • Dirty or contaminated fluids
  • High temperature applications
  • Polymerizing and oxidizing fluids
  • Media with poor lubricating properties


  • External source must be continuous and reliable, even during start up and shut down
  • Flush fluid must be compatible with process fluid and should not vaporize at process temperature
  • Product dilution will occur
  • Use with close clearance throat bushing to maintain pressure and reduce flush flow
  • Understand the cost of flush fluid, several gallons per minute consumption is typical