• TECH TALK •
The Essentials of Air Valves Explained
In water piping systems, air valves can be critical to ensuring system functionality. Aquestia’ s Laurent Dupuis explains why he constantly stresses this message when approached to discuss control valves for water usage.
• By David Sear, Technical English Services
Industrial systems can sound so straightforward that functionality is taken for granted. Consider fire-fighting systems in a refinery. These require access to water, a pump to generate flow, a control( deluge) valve for regulation, suitably positioned outlet points- with that, the system can surely be considered fit for purpose.
Laurent Dupuis, key account manager with Aquestia, explained trapped air in water pipelines could seriously impair flow, with far-reaching consequences. This is why, when asked to help with control( deluge) valve selection for fire-fighting lines and other systems for water, he always takes the time to ensure the client has given due consideration to air valves.
“ Trapped air in pipelines can cause more issues than most people realize,” he explains.“ Problems can include irregular water flow, dangerous down pressure, energy losses and even damage to the pipeline. Properly specified and located air valves can address such concerns. They can also assist in minimizing water hammer, especially when combined with nonslam devices.”
Air can be introduced in the system from several sources. For example, water can often contain up to two per cent dissolved air. It can also enter the system via centrifugal pumps.
“ Many engineers I speak to only take an interest in air valves at the end of the project, if at all. This can be partly explained due to air release valves being confused with gate, globe and check valves. Correctly selecting and installing air valves requires a good understanding of the behavior of air in a system, based on hydraulic and thermodynamic principles.”
Note that air valves can be classified into three main groups. Automatic air valves continuously release small air pockets from pipelines, kinetic air valves expel large amounts of air during filling
A pump suction control valve protects the pump suction supply from damage associated with low pressure and assures adequate supply pressure to the fire system components.
This high pressure, combination air valve is available in stainless steel, cast steel and super duplex materials and can withstand intermittent use up to 194 ° F.
( and admit air when draining), and combination air valves provide automatic and kinetic functions for complete air control.
The placement of air valves depends on system-specific criteria. They are typically installed at high points, pump stations, on long sections of a pipeline, and near control valves( all places where air pockets are likely to form).
Laurent’ s concluding piece of advice, however, is simplicity itself.“ When designing a system to transport water, make sure you eliminate air from so-called siphons. These are elevated sections of piping where the air will naturally accumulate – and could cause problems later, further along the pipeline.”
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