Industrial Utility Efficiency    

System Assessment

Compressed air represents one of the largest opportunities for immediate energy savings, which accounts for an average of 15% of an industrial facility’s electrical consumption. In fact, over a 10-year period, electricity can make up 76% of the total compressed air system costs. Monitoring compressed air usage, identifying compressed air waste and inefficiencies, and making investments in new compressed air equipment – including piping – are tangible ways businesses can cut their operating costs by lowering their electricity bill.
The advent of manifold-mounted, plug-in pneumatic valves has been a boon for machine builders. It allows them to mount complete valve packages in a safe and secure location on a machine. Using a D-sub connector, serial interface module, or similar single-point wiring system, all of the electrical control outputs can feed into one location on the manifold, greatly simplifying the wiring.
The project, which also involved the addition of a booster air compressor and receiver tank – along with the installation of an important pressure control valve – gives the automaker the ability to run fewer centrifugal air compressors during peak production. In so doing, the plant saves nearly 6.1 million kWh and more than $600,000 per year in energy costs. The project also qualified for a $369,374 rebate from the local utility, resulting in a six-month project payback – all while improving system reliability.
The compressed air system at the mail sorting facility has been in service since the 90’s. Two older 50-horsepower (hp) air-cooled fixed-speed lubricated air compressors are housed in the equipment room of the facility. The air compressors duty cycle alternates between one another on a set schedule. A 240-gallon wet storage receiver is used to help with air compressor control, with the air flowing through the receiver to a non-cycling refrigerated air dryer and system filters before finally being passed to the plant.
A chemical packaging facility had done everything right when they last upgraded their compressed air system a few years ago. They installed a Variable Speed Drive (VSD) air compressor and implemented other energy efficiency measures, but plant expansions caused increased system demand, which exceeded the capacity of the system. The packaging lines were now seeing low pressure, causing shut downs in production. And projections showed plant demand would increase even further.
With an eye toward strengthening its competitive edge, GKN opted for a new approach for the compressed air it uses to power metal molding machines in addition to a variety of other applications at its manufacturing facility. After careful analysis and planning with the Total Equipment Company located in Coraopolis, Pennsylvania, GKN opted to move beyond its aging compressed air system – and instead – outsource compressed air as a utility. Doing so allowed it to free up valuable floor space, while also achieving peace of mind since it can now count on a fixed cost for a reliable compressed air supply for years to come.
In terms of compressed air systems, it’s not unusual to see a plant with 10 to 15 air compressors, each of which is rated to provide 3,000 to 4,000 scfm of air. The air is used for everything from moving product, to powering pneumatic tools, pumps, and fans, to cleaning. There are easily 1,500 pneumatic control valves at a single plant.
Plant personnel had experienced ongoing problems with its process grinder performance due to unstable compressed air pressure. This created potential problems in terms of product quality. Grinders do not work properly without the proper pressure. Additionally, plant staff wanted to address these concerns, prior to a proposed 30% increase in production, and suggested raising the header pressure from the current operating pressure of 98 psig to 125 psig. The thought behind this was if the pressure from the header to the grinder process was dropping to 63 psig, then raising the pressure to the process would give the grinders enough pressure to work through higher peak production times.  
All industrial facilities use some form of compressed air, and in most, the air compressors consume a significant amount of the total energy bill. A facility with a good energy management system is likely to identify their compressed air system as a significant energy user (SEU). If the facility were using an energy management standard, such as ISO 50001, they would be required to assess and track the energy consumption of all their SEU’s. In the case of the metal processing facility, they were measuring the output of more than 250 devices within the plant, including building heaters, RTU’s, dust collectors, and also tracking the consumption of their electricity, natural gas and water. 
One observation I’ve made from 30 years of working with compressed air systems is to never underestimate the ingenuity of plant personnel when it comes to misapplying compressed air. We see something new in virtually every plant we visit, but one of the more common problems we encounter involves the use of expensive air for bearing cooling.