The swirl pot is not a new idea. Over 100 years ago designers of fluid systems were being bothered by air bubbles forming in their systems and causing flow stoppages, overheating, noise and pump damage from cavitation.

The swirl pot is a tall cylinder with the a fluid inlet about mid height and at a tangent to the centerline so as to create a swirl in the fluid as it enters the pot. The swirl or spinning of the fluid provides a longer path and more time in the pot. A filler port at the top and some system to remove air recovered from the fluid. The fluid exits at the bottom center of the pot.

Entrained air is liberated by buoyancy and moves to the top of the pot.

A pressurized bottle is fed air and fluid into its bottom from the top of the swirl pot. At startup, the pressure bottle contains about a 1/3 volume of the same fluid. As the system changes volume from heating, air and fluid is forced into the pressure bottle, when system pressure drops below the bottle pressure, only fluid can be returned to the system.

After several heat cycles, additional fluid may be required in the pressure bottle. After several cycles very nearly all of the air will have been removed from the system. In large heating systems the pressure bottle (then called a make up tank) may be several hundred gallons in size. In smaller systems it might be as small as one quart.

The ITT version for heating systems is called a Rollairtrol.

This system is recommended by Cosworth on new installations.

The method is more effective when close to the pressure outlet of the pump, (higher system pressure) but will work, if sluggishly, anywhere in a pressurized system.

Total system pressure is controlled at the top of the pressure bottle with a spring cap or weighted safety valve.

The swirl pot should have the fill port as the highest part of the system. The pressure bottle can be mounted at any elevation.

Lynn E. Hanover