AIR CONDITIONING: AIR PURITY(1)

Maintaining the proper air quality level is essential for keeping compressed air energy costs down and to ensure reliable production. Poor air quality can have a negative effect on production equipment and can increase energy consumption and maintenance needs. The quality of air produced should be guided by the quality required by the end-use equipment

AIR CLEANING DEVICES.

  1. Dust collectors
  • Electrostatic precipitator
  • Fabric collectors
  • Wet collectors
  • Dry centrifugal collectors

2. Air filters

SELECTION OF AIR FILTRATION EQUIPMENT

The selection of air filtration equipment is based on;

  • Efficiency
  • Dust holding capacity
  • Pressure drop

METHODS OF AIR FILTRATION

Straining:  straining occurs when a particle is larger than the opening between fibers and cannot pass through. It is a very ineffective method of filtration because the vast majority of particles are far smaller than the spaces between fibers.

Impingement:  when air flows through a filter, it changes direction as it passes around each fiber. Larger dust particles, however, cannot follow the abrupt changes in direction because of their inertia. As a result, they do not follow the air stream and collide with a fiber. Filters using this method are often coated with an adhesive to help fibers retain the dust particles that impinge on them.

Interception:  interception is a special case of impingement where a particle is small enough to move with the air stream but, because its size is very small in relation to the fiber, makes contact with a fiber while following the tortuous air flow path of the fiber.

Diffusion:  diffusion takes place on particles so small that their direction and velocity are influenced by molecular collisions. These particles do not follow the air stream, but behave more like gases than particulate. Diffusion is the primary mechanism used by most extremely efficient filters.

Electrostatic:  A charged dust particle will be attracted to a surface of opposite electrical polarity. Most dust particles are not electrically neutral, therefore,  electrostatic attraction between dust particle and filter fiber aids the collection of efficiency of all barrier type air filters.

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Air Weight

Like other Substance, air has weight. Composed of nitrogen, oxygen, carbon dioxide and other gases, it surrounds the earth like an envelope. And, it extends almost a thousand kilometers above the Earth’s surface.

Air Weight  is the mass per unit volume of Earth’s atmosphere. The weight of air, like air pressure, decreases with increasing altitude. It also changes with variation in temperature or humidity.

WEIGHT OF AIR AND ALTITUDE

A little change in the atmospheric pressure can make us feel sick. This is the reason why mountaineers get sick at high altitudes. As we go higher, the air becomes thin and hence, the atmospheric pressure also decreases.

Air is a real substance and it has weight. That is why it weighs 14.7 pounds per square inch at sea level. What scientists mean when they give this figure is that if a column of air one square inch in size from sea level to the top of the atmosphere above Earth would weigh 14.7 pounds.

If you travel up over a mountain pass air pressure decreases as you move upward. At 18,000 feet above the Earth the air pressure is approximately 7.35 pounds per square inch or half the atmosphere at sea level.