Compressed Air Open Blowing in Commercial Printing

Using compressed air for open blowing is common in commercial printing operations. Compressed air is typically 100 PSI in most printing plants. Using 100 PSI for open blowing is very expensive compared to low pressure blowing at 1-5 PSI.

Most industrial air compressors make slightly more than 4 SCFM per brake horsepower. A 5 PSI low pressure blower will make more than 40 SCFM per brake horsepower. Printers in Minnesota typically pay on average $400.00 per online compressed air horsepower.

Example:

Bindry Application needs 200SCFM (4000 hours annually)

Annual Electrical Cost to use Compressed Air: $10,000.00

Annual Electrical Cost to use low pressure blower: $2000.00

Open blowing is a mass flow application where pounds of air at a velocity are used to perform work. The pressure just upstream of the open blowing nozzle, regardless of the supply source will be near atmospheric and no where near the 100 PSI of the high pressure system. If the air is to be used at less than 10 PSI, why compress it to 100 PSI?

A considerable portion of high pressure open blowing nozzles use crimped copper tubing. This is terribly inefficient at shaping the air stream to perform work. Low pressure engineered nozzles can shape the air stream to fit the application by applying the work force where needed. The final result is the exact same mass flow (pounds of air at a velocity) as with high pressure, for less than half to one fifth the operating costs. This ensures a more efficient delivery, improving the final product.

Additionally, low pressure blowing does not require clean up equipment because we are compressing the air to less than one atmosphere and the blower is oil free. There is a low pressure blower to maintain but maintenance will be insignificant compared to that of a compressed air system.

Compressed Air Safety Nets:
A Guide to Predictive Maintenance Programs

Compressed air is probably one of the most versatile operations within the manufacturing environment. It transcends industries, operations and applications. Compressed air is used to power tools, move conveyers, transport products and make process applications possible. It is the fourth utility. Therefore, similar to electricity, disruption of the compressed air supply can cause costly production delays.

Fortunately, compressor operations are constant and very predictable. Compressor applications and subsequent performance are based on specific physical conditions. Over time, the demand requirements can negatively affect a compressor’s performance efficiency. For example, deposits found in the air can lead to a loss of air pressure. Therefore, there is an increase in electricity needed to produce the required pressure for a system’s application.

Predictive maintenance programs, when utilized correctly, can alert the plant operator to these and other potential failures within the compressed air system. With the help of various types of control systems, companies can perform daily "observation maintenance" programs for compressed air systems and other rotating equipment. By reviewing daily readings of temperatures, pressures, and functions, plant operators can predict, not only where the failure could take place, but more importantly -- when it may happen. This advantage can prevent unscheduled repairs and costly downtime.

This article reviews the importance of establishing a predictive maintenance system and reviews strategies for selecting and managing an effective program.

How Predictive Maintenance Works

The first step in establishing a predictive maintenance program is to understand your goals. The overall goal of a predictive maintenance program is to maintain the compressed air system’s efficiency, which in turn increases reliability and extends equipment life. Predictive maintenance programs provide protection for each sub-system within the compressed air system, including air, cooling, oil, and driver (i.e., electrical motor, steam turbine, diesel engine, etc.). Here are some examples:

For the air system, maintaining aerodynamic efficiency and the health of moving parts are primary concerns. Both can be compromised by poor air quality. If air contaminants come in contact with impellers, rotors or pistons, it can increase the wear rate of the moving elements and decrease the overall system efficiency.

Air cooling systems can become contaminated simply due to the build up of deposits found in the water. Over time, this build up can cause a loss of heat transfer capability, resulting in an increase in air temperature.

With oil cooling systems, if the lubricant is not kept clean and maintained at the correct temperature, metal to metal contact between rotating assemblies and bearings can occur. This can increase system vibration and required horsepower.

With lubricated compressed air systems, improper changeout intervals for separators and/or oil coalescing elements can increase oil carryover throughout the compressed air system. This type of carryover can be detrimental to the compressed air system’s application.

The driver system can have the same potential problems as the other systems. If the system becomes contaminated, its ability to work efficiently will be compromised.

A predictive maintenance program will help prevent these potential faults in the system’s efficiency and help reduce both downtime and unscheduled repair costs. Although, in order to ensure the success of a predictive maintenance program, there needs to be an understanding of what variables can be monitored.

Pat's Helpful Tip of the Day

Perform regular maintainence on your air compressor and air dryer drain valves.  On a hot Minnesota summer day, a 50 horsepower air compressor can generate up to 30 gallons of water.  If any of your drain valves are failing, the water will pass right though to the printing process.

Control your air quality by performing Air Quality Testing. Contact Pat Becker at Air Power Equipment Print Solutions for more information pbecker@airpowerequip.com.

For additional information, visit these related websites.

www.pimn.org

www.sonicairsystems.com