• AES Customer focus

API Plan 23


Product recirculation from seal chamber to heat exchanger and back to seal chamber.


1. Circulation is maintained by pumping ring.

2. In idle condition heat transfer is maintained by thermosyphon effect and in running condition by a pumping ring.

3. Lower product stabilization temperature is achieved.

4. Establishes required margin between fluid vapour pressure and seal chamber pressure.


1. In hot and clean services e.g. in boiler feed water and hot hydrocarbon services.


1. Maintain maximum 0.5m horizontal distance from seal chamber to heat exchanger.

2. Vent valve required at highest point of piping system.

3. Ensure that pump has a close clearance throat bush.

4. Ensure that the seal outlet connection is in the top half of the gland.

5. Ensure that the cooler is mounted above the pump centre line.

6. Vent the system fully before start up.


Want an expert explanation?

Our API expert Richard Smith walks through some of the 4th Edition API Plans, providing expert analysis and explanation of each plan.


API video series thumbnail


Click to Watch