Friday, January 2, 2009

Water in Air

Cleaned Dried Compressed Air
Proper selection and application of air dryers maintains system reliability and longevity.

Most maintenance and production engineers would say that oil is the major contaminant in their compressed air system.

Nearly all of the total liquid contamination found in a compressed air system is water, with oil being a small part of the overall contamination problem. Filter systems can remove oil and dust, but dryers are required to remove water and adjust humidity.

How much water is actually in your compressed air system?
The answer might surprise you.
A small 100 cfm compressor and refrigeration dryer combination, operating for 4000 hours in typical northern Malaysia climate conditions, can produce approximately 2200 gal of liquid condensate per year!

Failing to remove this moisture from a compressed air system can result in condensation in piping, pneumatic tools, and instruments, leading to damage and premature failure.

Water, water, everywhere
Simply put, atmospheric air contains water vapour.
The air's ability to hold water vapour is dependent upon its temperature.
As temperature increases, the level of water vapour held by the air increases.

During compression, air temperature is increased significantly, which allows the air to retain more incoming moisture. It takes 7.8 ft3 of free air to generate 1 ft3 of compressed air at 100 psig.

After the compression stage, air is typically cooled to a usable temperature, reducing the air's ability to retain water vapour. A proportion of the water vapour condenses into liquid water and is removed by a drain fitted to the compressor after-cooler.

Further condensation occurs as air is cooled by the air receiver, piping, and as it expands in valves, cylinders, tools, and machinery.

When air is compressed, the dirt & foreign particles are not remove but they become concentrated to the maximum through the process of compression.

Condensed water and water aerosols can cause corrosion to the storage and distribution system, as well as damage to production machinery and an application's end products.

Liquid water can also wash away pre-lubricants on the cylinders and valves, decreasing their operational life.

Water in a compressed air system also reduces production efficiency and increases maintenance costs.

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