Pneumatic systems have become critical to automation motion and control applications in almost every sector. Clean, versatile and powerful, compressed air is piped around a ring main in a factory much in the same way as electricity and is, in effect, another utility.
Air is an abundant and safe material and in a well-designed and maintained system, compressed air can be accurately controlled and adjusted to meet the varying needs of different processes and machines.
However, when neglected or poorly maintained, air systems can become inefficient due to leakages and other factors resulting in breakdowns, costly line stops and extended downtime for unscheduled maintenance. Understanding how to prevent this costly downtime, including the criteria and factors that impact on the performance of your system, is critical to minimizing the impact of unscheduled maintenance.
We’ve compiled three ways you can prevent costly downtime:
1. Reduce artificial demand
Alarmingly, studies have indicated that in an average manufacturing plant, only around half of the compressed air generated is actually consumed by the normal production processes for which it is provided. Up to 30% is lost in leaks, with another 15 to 20% consumed in non-manufacturing uses such as handheld blowguns for cleaning, and even cooling for workers in the plant or factory. The remaining lost air is accounted for by what is often termed ‘artificial demand,’ caused by operating the system at excessively high pressure.
Using Parker’s Air Saver Unit can reduce air consumption by up to 50% through pulsed air technology to produce high speed on and off pulses resulting in fewer tank recharging cycles. Looking at the issue from a cost point-of-view makes the issue even more clear and concerning for business owners with an eye on costs. For every pound spent on electricity to generate compressed air – for example, powering the compressor – only around 12 to 17 pence is actually used productively. These figures only take into account direct energy costs, and do not reflect the cost of capital equipment investment and maintenance.
2. Implement an effective leak identification program
It is usually the case that people tend to consider air systems in relation to the direction the air flows; that is from the compressor out to the end piece of pneumatically operated equipment. However, it is important to understand that the demand side of any system determines what needs to happen on the supply side.
Stopping leaks is the obvious first step in improving the efficiency of a compressed air system and enjoying immediate cost savings. A managed and effective leak identification and correction program should be an integral part of any compressed air energy management program. However, whilst leak detection and management is important there are numerous other areas to address; it is a fact that many compressed air audit programs only take a cursory look beyond leaks.
3. Reverse engineer to save energy
Taking a reverse engineering approach to highlight and deal with inefficiencies in a compressed air system is a good approach once an ongoing leak detection program has been implemented and the work to deal with inappropriate use and over-pressurizing of the system is done. Reverse engineering can help highlight, check and then allow the addressing of the following factors:
A. Correct sizing of pneumatic piping and connections from the main header to the inlet of the equipment to minimize pressure drop. Best design practices include minimizing the number of angle fittings and connections to allow an uninterrupted flow and reduce the opportunity for leaks and pressure drops.
B. The use of appropriately sized air treatment components, such as filters, regulators and lubricators, can also help reduce the pressure drop. Cutting the total cost of ownership over the life of the equipment may far outweigh the acquisition cost of properly sized equipment.
C. Proper use of reverse flow regulators and dual pressure circuits can reduce air consumption while also increasing efficiency. Most actuators such as cylinders perform work in one direction only, and the return stroke is merely to allow repositioning for the next cycle. Performing work extending a cylinder or proper operation, and then retracting the cylinder at a reduced pressure, is a strategy that can result in significant energy savings and therefore reduced cost of operation.
D. Appropriate control and regulation of air consumption devices such as air knives, pneumatic motors, diaphragm pumps and compressed air venturi-type vacuum generators. When operated in an unregulated or uncontrolled manner, these devices can be large consumers of high-pressure compressed air. As well as being wasteful, this places additional stress on the system that may result in premature failure or reliability issues. Installing simple sensing circuits that turn the air off when the machine is idle or parts are not present can deliver significant savings.
E. The design and implementation of directional control valves, with wear compensated seal technology on the spools and solenoid-controlled pilot-operated technology, instead of lapped-spool and sleeve design using direct-solenoid operators, can reduce energy consumption and increase reliability. In a large manufacturing plant utilizing thousands of directional valves, the energy savings can be very significant indeed and the risk of breakdown and costly downtime significantly reduced.
After compressed air ‘demand side’ opportunities have been identified and acted upon, then a similar analytical look can be taken at the supply side to optimize potential savings there.
Taking time and allocating resources to optimize the design and performance of compressed air systems is becoming increasingly important as energy costs continue to rise. The impact on profitability of not taking steps can be significant and have a direct effect on the bottom line of any business. Achieving long-term energy savings and high system efficiency with reliability will be enjoyed if the steps described above are implemented and a sustained. An ongoing plan as opposed to a one-time, short-term approach will normally achieve excellent payback.