Deaerator Tank: The Thermic Fluid in the complete circuit expands in volume, when it is heated. The rate of expansion in volume is 7 % per every 100 Deg. C rise in the temperature of thermic fluid. Hence the selection of the size of expansion tank depends upon fluid content of the total system. As a guideline the expansion tank capacity should be 20 % of the total volume of the oil to be filled up in the system.
The Deaeration vessel capacity depends upon the flow rate. Its size can be roughly decided considering 2.5 to 3 m/s fluid velocity at its inlet nozzle. The standard Daearator cum expansion tanks supplied is suitable for most of the standard processes. In case the volumetric expansion of Thermic Fluid of the system is more then the capacity of the expansion tank provided, a separate extra expansion tank needs to be incorporated. The Thermic Fluid also contains some higher fractions which flash off at elevated temperature while commissioning.
These are to be driven out of the system to have proper functioning of the equipment. The combined expansion and Deaerator tank is so designed as to take care of the expansion of Thermic Fluid and also to drive away the gases or entrapped air. This tank should be installed at least 1 meter (3 Feet) above the highest point in the Thermic fluid pipeline. It is also necessary to confirm that the NPSH available at the pump suction is more, by at least 0.5 m, than the NPSH required for your pump. Supports are welded to the tank, with the help of which the tank can be fixed and bolted to the structure.