Air and Dirt Separators are designed to remove both air and dirt from circulating heating and chilled water systems and in doing so play a vital role in helping to maintain water quality and efficiency in these types of installations.
A heating or chilled water system that has a significant build-up of corrosion and sludge has to work significantly harder to distribute the water. This corrosion will significantly impact the water flow resulting in components having to operate harder than their capabilities. Increased demands on the system will lead to replacing components sooner than expected which means unplanned maintenance costs and higher energy consumption
An air and dirt separator provides a dual function by collecting and removing dissolved gases from the system water through an automatic air vent and also trapping dirt particles that can be removed through periodic flushing.
Air is present in system water in a variety of forms. There are the large visible air bubbles that become trapped in the system as part of the installation process but also dissolved air which enters the system from the water. The dissolved air is released from the water as the system temperature rises or in areas of the system which has lower pressures. When dissolved air is released from the system water it takes the form of microbubbles.
Whilst the large visible bubbles can be removed by less sophisticated components such as float type air vents it is only specifically designed air and dirt separator that will remove microbubbles such as the Stourflex JP603
The separation occurs in the enlarged outer chamber of the air and dirt separator which is fitted with a stainless steel diffuser screen. Due to their small size and low buoyancy of microbubbles they are more difficult to capture than large visible air bubbles. The stainless steel diffuser screen provides the surface upon which microbubbles can cling and eventually fuse together to merge into larger bubbles which gain buoyancy and float to the top of the chamber where they are vented automatically.
By increasing the size of the chamber this reduces the velocity and decrease the turbulence of the water flow. This provides the opportunity for air bubbles to be separated and rise to the top of the chamber and for solid particles heavier than water to fall and be collected in the bottom of the chamber
When selecting the position to install we should be aware of what Henry’s Law states with regards to the relationship between a liquid and a gas.
Key elements of the law prove that the higher the temperature and the lowering of pressure are the conditions that need to be created to allow a gas (air) to be released from liquid (water)
These can be shown with the following examples
Lowering the pressure
An everyday example of Henry’s law is given by carbonated soft drinks. Before the bottle or can is opened, the gas above the drink is almost pure carbon dioxide at a pressure slightly higher than atmospheric pressure. The drink itself contains dissolved carbon dioxide. When the bottle or can is opened, some of this gas escapes, giving the characteristic hiss because the pressure of carbon dioxide above the liquid is now lower, some of the dissolved carbon dioxide comes out of solution as bubbles
As the temperature increases, the solubility of a gas decreases. More gas is present in a solution with a lower temperature compared to a solution with a higher temperature. This can be seen when heating water in a kettle small bubbles evolve and rise as the temperature increases
The Stourflex range of micro bubble air and dirt separators are designed to take advantage of these conditions in Low Temperature and Chilled Water systems
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