TECHNICAL 35
Q – What is a deaerator device ?
Patrick continues with his contribution , this issue on deaerator devices .
By Patrick Gordon of Calafrica ( technical @ calafrica . co . za )
Images supplied by Patrick Gordon
A : We have all come across an aerator that is fitted to a terminal fitting . These are used to add air to the water and the result is to break up a laminar flow . The deaerator does the exact opposite , it removes all the air from the plumbing system . Let us have a look at the need for , and the use of , a deaerator device . Deaerators are used to continuously remove the air contained in the hydraulic circuits of heating and cooling systems . The air discharge capacity of these devices is very high . They are capable of automatically removing all of the air present in the system , down to micro-bubble level . The circulation of fully deaerated water enables the systems to operate under optimal conditions , free from any noise , corrosion , localised overheating or mechanical damage .
The bubbles , fusing with each other , increase in volume until the hydrostatic thrust is sufficient to overcome the force of adhesion to the structure . They then rise towards the top of the device and are expelled through a float-operated automatic air vent valve ( 2 ) [ see article in the June 2023 edition of Plumbing Africa ]. It is designed in such a way that the direction in which the medium is flowing inside the deaerator makes no difference .
Micro-bubbles develop where the speed of the medium is particularly high , with a corresponding reduction in pressure . These points are usually the pump impellers and the water orifices of the regulating valves . These microbubbles of air and steam , the formation of which is accentuated in non-deaerated water , may subsequently implode because of the cavitation effect .
So how does a deaerator perform this magic ? The deaerator utilises the combined action of several physics ’ principles . The active part consists of a set of concentric metal mesh surfaces ( 1 ). These elements create the swirling motion required to facilitate the release of micro-bubbles and their adhesion to the surfaces .
“ The deaerator utilises the combined action of several physics ’ principles .”
The deaerators can also be supplied with an insulating shell to make thermal lagging easier . Deaerator devices may be used in both heating and cooling circuits , to guarantee progressive elimination of the air which forms continuously . They should preferably be installed vertically after the boiler , on the pump suction side , as this is where the formation of micro-bubbles is most prolific .
October 2023 Volume 29 I Number 8 www . plumbingafrica . co . za