By Ron Marshall
One of the most common ways to waste compressed air is to use it for blowing dust or debris. Compressed air is often directed at equipment to clean the dust that has settled on the surfaces. But when you think about it, reintroducing this dust into the atmosphere, only to settle on some other nearby surface is probably an exercise in futility.
Let’s examine a typical blow wand made up of a 3/8 inch pipe, controlled by a ball valve, and fed by a pressure of 90 psi. This wand might consume 100 cfm when blowing once the pressure losses in the supply hoses is taken into account. This is the equivalent to 25 hp of compressor power or about 21 kW. This is like bringing a cannon to a rabbit hunt, wasting 21 kW of power to dislodge a few ounces of dust. If this blowing was continuous, it would cost about $18,000 per year to produce the compressed air.
If the blow hoses are used to clean clothing the operation is also a safety hazard. Compressed air can cause small particles of debris to become airborne, flying into people’s eyes or lodging in their skin. In extreme cases compressed air has been known to pierce the skin and form embolisms. Many plants have outlawed personnel blowing, opting to go with electric cleaners as pictured in the photo.
Some tips about blowing:
- Continuous blowing for cleaning or cooling is the most expensive of all, consider the use of low pressure electric blowers
- If blowers can’t be installed, consider using engineered nozzles that can provide the same air movement for lower cost
- Reducing the duty cycle of blowing is a good way to reduce total operating cost, use of sensing eyes can ensure that the blowing takes place only when required
- Ensure a pressure regulator is installed on any blowing, reduce this to as low as possible
- For cleaning of equipment consider leaf blower style portable devices using electricity or fuel
- Realize that the use of compressed air is about 10 times more costly than direct electric power — this should be considered when installing any blow nozzles.