Almost every industry in America today is experiencing higher costs – energy, raw materials, labor, healthcare shipping – you name it. Energy prices have been rising and many experts forecast that these increases will continue. Energy costs sometimes are overlooked when developing productivity and cost reduction plans.
Compressed air systems are safe, reliable and versatile, but they are usually taken for granted with little regard to costs and energy consumption. There are three important reasons why it is worth investing time and effort in reducing compressed air costs:
- It will save energy and money by identifying and eliminating waste
- It will improve the reliability and performance of the compressed air system
- It will reduce environmental impact through reduced electricity consumption and consequent lower carbon emissions.
A properly designed and maintained compressed air system that is energy efficient could save the user thousands of dollars each year. It will also minimize the risk of lost production by increasing the reliability of supply and improve the strength and safety aspect of operating a pressurized system. Every dollar saved on energy goes straight to the bottom line and is a very effective way to increase profits.
Of all utilities, compressed air represents one of the largest opportunities for immediate energy savings on any site. Furthermore, most of the energy and carbon savings are achievable with little or modest investment.
Compressed Air Pipe System
The role of the compressed air pipe system is to deliver the compressed air from the compressor discharge to the points of use with minimal leakage, minimal loss of pressure and minimal effect on the quality of the air.
Friction and leaks cause a pressure drop between the compressor output and the eventual point of use. This lost of energy in the pipe system is largely due to the pipe material, design and layout.
Most distribution piping is made of galvanized steel, although copper, aluminum and some specialized plastics are becoming more common, with each having its own advantages and disadvantages. For instance, plastic can suffer from degradation through UV light, while high pressures and temperatures can deform the pipework. Not being as solid as metal, plastic can bow and require more brackets to install and support the ring main throughout the building. This adds cost to the installation.
Metals can also degrade. Copper and black iron have been the overwhelming favorites for compressed air systems for many years due to the cost of the materials. However, threaded joints often serve as a source of leakage. This leads to higher operating costs because compressors must operate overtime to compensate for the leakage. But these aren't the only drawbacks to metal piping systems. Interior corrosion can cause scaling and pitting on inside surfaces. As the corrosion products combine with moisture and other contaminants, they accumulate on the inner surfaces of the pipe and fittings, increasing their roughness. As the internal diameter becomes rougher, pressure drop increases. Again, this ends up costing money by reducing efficiency of the compressed air system. Perhaps more importantly, particles can dislodge and clog or damage end-of-line equipment.
Lightweight aluminum is the ideal product for maximum flow. The first push-to-connect aluminum piping system was launched by Parker in 1996. Transair is a system of powder-coated aluminum pipe and engineering grade polymer connectors. Transair’s quick, instant connections eliminate the need to thread, solder or glue pipe. The lightweight aluminum pipe is also easy to handle and safe to work with on elevated platforms.
The flow characteristics of Transair’s smooth bore aluminum pipework are crucial in helping to reducing the pressure loss through the system. Each stick of pipe and each take-off to a component such as an air tool will cause a reduction in pressure. For maximum system efficiency, Transair connectors do not intrude into the pipework to cause turbulence nor do they cause scratching on the outside of the pipe which can cause a leak at each connection.
The cost of air mains frequently represents a high proportion of the initial cost of a compressed air system. Therefore, smaller diameter pipe is often specified to save on capital cost. However, this is misleading since the restriction due to the smaller piping causes greater pressure drop across the system, resulting in higher energy consumption. The increased energy costs can soon exceed the price of larger diameter piping. This graph shows what happens to the power required to deliver 29 scfm of 7 102 psig air along 328 feet of steel pipe as the diameter changes.
As a general rule, pipe diameters should be calculated based on having a maximum air velocity of 19 ft/s, in the main supply line. In branch lines with a total length less than 49 feet, velocities up to 49 ft/s are acceptable.
Survey the layout of the pipe system. As far as possible eliminate elbows, minimize changes in the direction of airflow, remove other constriction, reduce excessive pipe lengths and isolate unused compressed air piping because is may be a significant source of air leaks. All compressed air pipe systems should be designed with the following points in mind:
Pipe diameters selected should minimize pressure drop and allow for possible expansion.
Fittings and valves selected should minimize restriction to airflow. Large radius bends are preferred to elbows, for example. Full-throated valves such as ball valves should be used rather than gate valves.
If replacing pipe, consider smooth bore pipe to reduce friction.
All piping must be well supported to minimize movement and sagging. This will help to minimize leaks, avoiding build up of corrosion and fluids and lengthen the life of the pipe system.
Compressed air represents one of the largest opportunities for immediate energy savings, which accounts for an average of 15% of industrial facilities consumption of electricity and most of the savings are achievable with modest investments compare to total costs.
Over a 10-year period, electricity costs make up 76 percent of a factory’s operating costs. In many cases, the electricity used by a compressed air system in a factory makes up the largest percentage of an increasingly expensive electricity bill. Monitoring compressed air usage, identifying compressed air waste and inefficiencies, and making investments in new compressed air equipment are tangible ways that businesses can cut their operating costs by lowering their electricity bill. For instance, it is estimated that a º-inch leak in a compressed air system equals about $8,000 per year leaking off a company’s bottom line. Therefore, a proper compressed air system has a tremendous potential to save a company a significant amount of money. The impending savings (payback time of less than 36 months*) can be summarized in three main categories in term of potential contribution: compressor improvement, reducing air leaks, and global system improvement.
As noted above, air leaks are the main sources for energy loss in a compressed air system. For instance, a 14.5 psi pressure drop uses 10 percent additional energy. Furthermore, the selection of pipe can have an impact on pressure drop. The graph below shows the difference in traditional and aluminum pipe using a length of 100 feet of pipe, 40mm (2” Steel), 60 HP compressor, and cost of electricity of $0.10 per KWh. Pressure drop can result from a number of sources, including poor system configuration, interior pipe surface corrosion and compressed air contamination.
Typical on-site savings have been estimated to be up to 30% of the energy input to the compressor. These savings are achievable through initially selecting the most efficient type of compressor, ensuring the correct air system design and ongoing efficient operation and good maintenance. It includes maximizing the use of the latest technologies available and also ensuring that attention is paid to the simple measures of keeping leakage rates to a minimum.
By choosing an efficient compressed air system the potential savings that can be achieved on a machine can reach up to 60%. Traditional piping systems, made of steel or copper and that are still in use, are known not be energy efficient, through loss of power and considerable leakages. Difficult to trace and repair, they can have a huge impact on operating budgets.
Therefore, Parker Transair has developed an energy calculator that enables system designers to determine the precise savings to be made by using Transair in comparison to other systems. Thanks to this software, contractors/end users can immediately calculate the potential savings that can be made by opting for a Transair solution. On the basis of compressor related data such as pressure, flow rate, annual hours of operation, the type of dryer and data from the characteristics of the network and the local cost of electricity, the Transair energy efficiency calculator software defines the savings and the duration of return on investment. The return of investment is based on the pressure, power or throughput, the number of annual service hours, the type of dryer, plus data from the network, such as length of the main circuit, the type of open or closed circuit, the pipe material used and the local cost of electricity, including inflation factor. The results speak for themselves and show that Transair is the best performing system and the best long term choice, no matter whether the project is for an extension, the modification of an existing network or a new installation.
To make the calculation using the Transair Energy Calculator, you will need:
- Data about the compressor room.
- Data about the compressed air network.
- Economic data (quotation for the network, electricity cost).
You will be able to compare Transair pipe to traditional compressed air network (steel, copper, plastic…):
- for an new quotation: the quotation for Transair compared to the quotation for a new network in steel.
- for an existing installation: the quotation for Transair compared to the annual cost for an old network in steel.
The results will show estimations of:
- Total annual cost for a traditional network and for Transair.
- Total of money saved for 1 to 10 years using Transair.
- The payback period of the initial investment in Transair products.
An additional “Financial report” will allow you to export and print a chart with a cost comparison, year after year, in order to give all the data to the decision-maker. The software is user friendly.
In industry today, we face many challenges including the high cost of energy and foreign competition. Your electricity bill is part of your cost and it is a cost that can be controlled in part by using a high-efficiency compressed air pipe system.
By Paul Johnson, Parker Transair