Efficient use of compressed air

Compressed air is often the highest energy cost for many businesses, but unfortunately this resource is often seen as unlimited. It is, therefore, important that this valuable energy source be utilised efficiently, in all processes, at all times.

With the requirements on industry to move to more sustainable and energy-efficient processes and practices, the need to identify and maintain better ‘in-house’ practices is developing.

The costs associated with the use of pneumatically operated processes can be dramatically reduced provided that the compressed air systems are efficient and are well maintained. Maintenance must include the establishment of, and adherence to, efficiency ‘benchmarks’ for all processes.

When establishing benchmarks for the efficiency of pneumatically operated processes, there are several areas that need to be considered:

Quality — What is the required level of particle filtration, moisture and odour removal? These are determined by the required processes and the requirements of the selected pneumatic components.

Volume — What volume of air is required for the processes? This should account for the highest demands required.

Pressure — What is the maximum pressure available? Is this pressure sufficient to satisfy all the processes?

In determining the above it is necessary to accurately measure the minimum requirements for each process. This must be measured during normal and maximum production. Once the minimum requirements have been determined these must be monitored on an ongoing basis to ensure that the efficiencies, once established, are maintained.

There are a number of considerations that must be observed when determining the minimum requirements for compressed air-operated processes.

Air preparation (or the conditioning of the compressed air) should be matched to the processes. Unnecessary filtration and conditioning will result in increased compressed air costs and often unreliable performance. The compressed air must be measured to establish current moisture levels, dewpoint temperature and air quality. It is often necessary to seek specialist assistance to determine this air quality.

Compressed air is generally supplied from a fixed compressor installation. The volume of air is, in many cases, established based on the initial plant development and, with the growth in compressed air demand (as the factory grows and production increases), can often result in periods where supply is insufficient to sustain efficient operation. In such cases, it is necessary to free up some air from certain processes in order to meet the demand of more critical processes or to reduce the air consumed through energy-efficient practices. The most efficient compressed air distribution can be determined following a compressed air survey. This survey should acknowledge all the factory processes, the compressed air systems employed and the efficient use of pneumatic components. More often resulting in considerable savings in compressed air usage, this process is essential to ensure the pressure energy is available where it is needed most.

The pressure of air supplied to processes is dependent on many factors. It is important to understand that the compressor merely develops air flow. The pressure developed in the supplied air is determined by the total pressure drops encountered throughout the system, up to the maximum capacity of the compressor. The capacity of the compressor, degree of filtration and installed components all affect the overall pressure drop and the maximum available pressure.

The layout of the compressed air distribution plumbing throughout the factory will further affect the air pressure that can be supplied to the pneumatic processes. In order to ensure the required pressure energy is supplied to the pneumatic processes, it is important to understand the use of energy-efficient components that can be employed. Wherever the pressure can be minimised while retaining efficient operation, then reduced costs will result. These costs are often 40% or more of current energy usage costs.

Many companies are ready to move towards energy-efficient processes but lack the expertise. Through the use of air survey specialists, a program can be established to assist with the transition to more energy-efficient practices. There are several steps in the move to more energy-efficient compressed air usage:

• Identify the need to save energy;
• Understand the current compressed air costs;
• Measure current air consumption;
• Incorporate air-saving measures wherever possible;
• Establish accurate benchmarks;
• Monitor performance against benchmarks.

Whenever a process changes or a new process is required, it is necessary to first understand the effects this will have on the total compressed air system. This understanding will assist in selecting the most energy-efficient solution, with the lowest operating costs. Often the cost savings in energy will dwarf the capital costs of the equipment selected.

As with all process improvements, it is necessary for all associated personnel to be given some ownership. An understanding of the benefits of energy saving and the benefits to the process and business will assist in maintaining a competitive process, and improve its environmental footprint.

*Bill Blyth is manager strategic product development, SMC Pneumatics (Australia) Pty Ltd