Air Logic
We recently provided insight into the AirTAC brand and before that we covered HMIs. These posts discussed modern pneumatic parts, data, and process flow. While increasingly prominent, we didn’t want to overlook air, which is arguably the oldest process of manufacturing control. Read on for a brief covering of Air Logic and a simple, overlooked application.
WHAT IS AIR LOGIC?
Air Logic Control, sometimes referred to as Pneumatic Logic Systems, is a reliable and functional control method for industrial processes. It is the traditional, low cost method of controlling equipment, acquiring machine data and more without the higher cost associated with more advanced systems. It is an important part of manufacturing systems, especially automation.
Benefits include:
• Ease of installation
• Superb reliability
• Minimal maintenance
• Very low cost
BRIEF HISTORY
Pneumatics is derived from the Greek word “pneumatikos,” which translates to “coming from the wind.” Air pressure was used to propel ships since the start of civilization. Bellows, used to produce bursts of compressed air for fire starting, date back to 3000 B.C. It was in musical instruments in the 1800s that pneumatic controls started to form. Perforated cardboard strips were attached end to end to produce a control process and play a continuous melody which was later applied to what became known as “player pianos.”
Compressed air preceded the use of steam and electricity as a form of mechanical control. Most development of air as a power source and control medium took place during the 18th and 19th centuries. Pneumatics became the main power source in many cities in the late 1800s. Paris had a network of more than 30 miles of piping with 90 psi provided by a 25,000 HP compressor. Pneumatic technology advanced and was later adapted to automate the textile industry as early as the early nineteenth century and evolved into the modern control and automation systems used today.
In modern applications, pneumatics often involves the combination of compressed air or fluid and electricity to create comprehensive control systems. With or without electricity, air pressure still provides many opportunities to power, control, and monitor manufacturing processes.
Before moving on, have a look at one of the most interesting applications of pneumatics from the 1800s. The tubing system shown below originated in Europe as a means of quickly transporting postal freight. Eventually, similar systems were installed underground throughout London and beyond.
These tube systems were created to transport mail and other packages across the city using only air pressure.
APPLICATIONS
Air Logic can perform almost any function normally handled by relays, pressure or vacuum switches, time delays, counters, and limit switches. While the design is similar, compressed air is the control medium instead of electrical current.
Environments high in dust or moisture are excellent places for air logic controls because practically no danger from explosion or electrical shock exists. Water can splash on the controls without effecting the operation. Air logic can also be used on equipment that has cylinders or fluid motors, but no form of electrical device.
One of the most common and overlooked uses is pneumatic counting. Our recent blog posts discussed preventive maintenance as well as more modern methods of acquiring data, but a simple pneumatic counter can provide valuable equipment data. Some mechanical or electrical devices may be impractical or inconvenient, depending on the application. Something like the Control Line AC-6 Pneumatic Counter can provide event recording, piece or part counting, or complete cycle counting. This information can be monitored and used for production purposes or in implementing a preventive maintenance plan as discussed in our Preventive Maintenance blog post.
Control Line AC6 pneumatic counter
Control Line SAC24 pneumatic programmer
DID YOU KNOW
Compressed air systems account for nearly 10% of all electricity used in U.S. manufacturing industries and the typical facility loses an average of 30% of its compressed air to leaks.
Compressed Air System Investment Realization
Knowing that, it should be easier to understand how ongoing energy costs are reported as the most significant investment in a compressed air system. One would assume the up front capital and ongoing maintenance costs would far outweigh energy expenses, but this chart illustrates the fact that 75% of an air compressor investment is in ongoing energy costs. The reason behind this is leaks.
In a 1,000 SCFM system, a 30% leakage translates into 300 SCFM. A report concluded that eliminating that type of leak is equivalent to saving as much as $45,000 annually in energy costs. Depending on plant location and energy costs, the amount saved could even be significantly higher.
Compared to a focus on energy efficient lighting and other efforts, air leaks cannot be seen. Often they produce no significant sound or any other potential indication of the issue. The invisibility of the issue is the common consensus as to why this significant source of energy waste is overlooked. We bring this up to spread awareness. Consider a review of your facilities. Ultrasound technology is one of a few ways to perform a comprehensive leak test, but often making employees conscious of the issue can be enough to remain vigilant in leak detection and prevention.
CONSIDERATIONS
Control systems can be pneumatic (ALC), electrical, mechanical, hydraulic, or a combination. Each have unique advantages and disadvantages.
Key criteria to consider when deciding on a control system:
• Capabilities
• Accuracy
• Reliability
• Responsiveness
• Safety
• Lifespan
• Cost
Air Logic remains a major part of American manufacturing, especially in the area of automation. The pneumatic infrastructure still exists from recent decades and many modern projects don’t necessitate additional functionality. Air logic will continue to be beneficial where upgrade cost, simplicity, or safety factors dominate.
Don’t discredit all older technology and don’t overlook the simple, effective ways of adding value to your operations.
AND FINALLY…
We hope this blog complimented our recent posts regarding pneumatics and preventive maintenance. Feel free to contact us with any further questions on air logic or any other custom manufacturing. We are always willing to help.