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Valmatic Air Valves for water and wastewater
Valmatic Air Valves for waterand wastewater system applications
The impact of air on a water and waste water system:
The presence of air in a pipeline and its impact on operations is one of the most misunderstood aspects of the Water & Wastewater industry. Many operational problems are blamed on improper installation of the line but they are really due to failure to de-aerate the line.
Air is always present in a pressurized, operating pipeline. This air comes from three main sources;
Present air – before a system starts there is air present in the pipe. When a pipe is filled with fluid this air must be eliminated. Most of the air is pushed downstream and released properly, however some air can become trapped at high points in the system. Air in water – water consists of about 2% air, during operations air will separate from the water and this too will become trapped at high points. Air through mechanical equipment – air is forced in through pumps or drawn in through valves under vacuum conditions.
There are two main impacts of air on a system:
Air accumulation – pockets of air collecting at high points can lead to a line restriction. They increase headloss, extend pumping cycles and increase energy consumption. Increased velocity – Air collecting at high points in the system means fluid is forced through a smaller space so fluid velocity is increased. As the air space grows larger two problems may occur: A pressure drop higher than pump capacity can develop and stop all flow The air pocket can become dislodged from the high point and is pushed downstream. The causes a huge increase in fluid velocity which is then suddenly stopped by another high point causing a high pressure surge know as a “water slam”. This is the most serious problem related to air accumulating at high points and can cause serious damage to valves, fittings, gaskets and can even break the line.
How to stop the impacts of air in a system:
Historically, engineers have tried using sandpipes to try and expel large amounts of air. Others used ball or gate valves to bleed off air at high points, but it was impossible to predict when a high point in a system may need bleeding. More commonly, open fire hydrants were used in the belief that all of the air will be released. The problem with this method is that hydrants are connected to the side of a pipe, still leaving some air trapped at high points.
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Sid Wilson’s solo show Val Air Ballroom 8/26/10