When we first tell converters that our dryer systems operate on compressed air, the immediate reaction is that compressed air is expensive. The truth however, is that Compressed Air Drying Systems only require about 65% of the energy required by Traditional Forced Air Systems. In fact the cost savings in heat energy alone is enough to offset the cost of operating the compressor. See Operating Cost Comparison Worksheet

Compressor Sizing
Air compressors are sized in terms of horsepower (hp), which correlates to the amount of air that the compressor can deliver or the SCFM. SCFM stands for Standard Cubic Feet of air per Minute and is defined as cubic feet of air per minute (CFM) at 70 Fº (21 Cº) and 1 atmospheric pressure (0 psi, 0 bar). As a general rule of thumb

SCFM = (Web width) * (# of dryers) * (# of air bars in each dryer) * 0.65

For example, a 17-inch press with 9 dryers, and each dryer containing 6 air bars will require 597SCFM (17 inches * 9 dryers * 6 air bars * 0.65 = 597 SCFM)

Types of Compressors
Air compressors are offered as either high pressure or low-pressure machines. High-pressure air compressors deliver line pressures in the range of 80 to 150 psi and are considered the standard for supplying plant air in virtually every industry. Advantages to using high-pressure compressors are that they are about 20% less expensive to purchase, they require smaller diameter piping for the airlines, and they provide a backup for plant air.

Low-pressure air compressors are designed to deliver line pressures in the range of 40 to 60 psi. Since the dryers only operate in the range of 15 to 20 psi, a low-pressure air compressor will deliver a sufficient amount of airflow. The advantage of using a low- pressure compressor is that it produces more SCFM at low pressures.

High-Pressure Air Compressor delivers 5SCFM/hp
Low-Pressure Air Compressor delivers –7SCFM/hp

So in the example given above, a converter could choose either a 120 hp high-pressure air compressor (597/5 = 120), or an 85 hp low-pressure compressor (597/7=85). A lower horsepower compressor translates into lower energy costs.

Consultation
We have established relationships with compressor companies and piping contractors so that they are familiar with the requirements of our dryer systems. We work closely with these vendors to ensure that guidance is available to our customers, on things like selecting the right type of compressor, making sure piping layouts include provisions for maintenance, the location of the compressor, etc.

  SCFM - (Definition)  

When talking terms of compressed air requirements, it is difficult to use CFM (Cubic Feet of air per Minute) because the mass of a specific volume of air is related to the pressure and temperature of that air. Mass is defined as a dimensionless quantity representing the amount of matter in a particle or object. As the air pressure increases, a specific volume will hold more mass of air. As the temperature of the air increases, the same specific volume will hold less mass of air. So in order to be accurate in discussing compressed air flow in terms of CFM, the pressure of the air and temperature of the air must also be considered.

As a result, SCFM is commonly used to specify compressed air flow rate on a common platform in terms of pressure and temperature. SCFM stands for Standard Cubic Feet of air per Minute and is defined as Cubic Feet of air per Minute at 70 Fº (21 Cº) and 1 atmospheric pressure (0 psi, 0 bar). This makes it convnient when specifying compressor capacity because it easily defines the "mass" of air for all air volume calculations regardless of their state of compression or temperature.