Brief Discussion on the Influence of Air Humidity on Air Compressors
As we all know, an air compressor compresses air and delivers compressed air to supply terminal equipment. Air compressors are widely adopted in factories of various scales, covering industries such as textile, chemical fiber, cement, glass, and auto parts manufacturing. So how to select a suitable air compressor for plant air demand? First of all, it should be clarified that users purchase a complete air compressor system and consume compressed air. Three core factors for model selection are crucial:
a) Pressure: Constant output pressure of the air compressor = Pressure required at air consumption points + Pipeline pressure drop + Pressure drop of post-processing equipment
b) Flow rate: Maximum flow rate – Average flow rate – Minimum flow rate – Reserve capacity for future expansion
c) Cleanliness: Requirements for compressed air quality, including water, oil, dust and particulate matter
Air humidity varies with air conditions. When air is compressed, its temperature rises and relative humidity declines. When compressed air expands, temperature drops and relative humidity increases, and water vapor normally condenses out. The impacts of air humidity are listed as follows:
- It hinders air compression and causes hydraulic shock to compression equipment and pneumatic machinery. If a large amount of water accumulates in coolers and cylinders, machine damage accidents may occur.
- It reduces the volumetric efficiency of gas. It is common knowledge that air is compressible while water is incompressible. Excessive moisture in air reduces the proportion of pure air per unit volume, resulting in insufficient air output of the compressor.
- Moisture in air is highly corrosive, which easily causes rust on compression equipment and pneumatic machinery and shortens their service life.
- Moisture narrows the flow path of compressed air and increases air flow resistance.
- One cubic meter of humid air has a lower weight than the same volume of dry air (lower gas molecular density). Most water vapor condenses after compressed air passes through coolers, air receivers and pipelines, which reduces the production capacity calculated by weight.
- During compression, moisture mixed with lubricating oil reduces lubrication efficiency and aggravates abrasion of components. In circulating lubrication packing materials, moisture not only leads to poor sealing but also causes deterioration of lubricating oil.
- If moisture exists in the air supply system, it will freeze on the inner wall of air pipelines when the temperature falls below 0°C. Ice narrows the pipe diameter; in severe cases, individual pipelines may be completely frozen and block operation.
Therefore, the quality of compressed air depends not only on its pressure but also on its humidity.
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