Pressurized barrier fluid reservoir supplying clean fluid for an arrangement 3 pressurized dual seal.


  • Product in seal chamber is isolated from pumping area using a close clearance throat bushing.
  • Increases product temperature margin in the seal chamber thus avoiding vaporization.
  • Seal runs at a lower stabilized temperature of the media.
  • Removes only the generated seal face heat and the heat soak from the pump area, thus the cooler is smaller and more effective as compared to an equivalent Plan 21.
  • Uses a pumping ring for circulation in running condition.
  • In idle condition, thermosiphon effect ensures circulation.
  • A distributed flush is not recommended for this plan.

Recommended Application

Remarks Checkpoints : 

  • For media with high viscosities and higher freezing points, steam must be used in the cooling lines instead of water.
  • A high-point vent valve to be provided to vent the system before start-up.
  • A close clearance throat bushing must always be in place to reduce the heat soak from the pump.
  • Avoid sharp bends and 90° elbows in piping. Piping should be smooth and continuously rising.
  • Cooler to be installed approx. 500 mm (20”) above pump centerline.
  • Good quality cooling water is recommended to avoid deterioration of cooler efficiency.
  • Flush outlet from seal chamber should be in the top half of the seal gland plate or the seal chamber.

Recommended Application : 

  • Hot hydrocarbons.
  • Hot water services above 80 °C (176 °F).
  • Boiler feed water.
  • Applications where increasing seal chamber pressure to improve vapor pressure margin is not possible.