System Assessments

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 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.

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.

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.

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. 

By addressing inappropriate uses of compressed air and making changes to the compressed air production side of their compressed air system, a distiller of fine alcohol products reduced its energy consumption by 30%, saving \$16,600 per year in energy costs - with more potential savings possible.

Experienced auditors become wary when they see desiccant dryers installed in customers’ plants. These dryers are required when a plant needs instrument-quality compressed air, or when compressed air piping is exposed to freezing temperatures. However, while desiccant dryers can gain this level of quality, the energy cost of stepping up from a dewpoint of 35°F to a level of -40°F increases quite considerably. To attempt to reduce the energy costs of drying to these low levels, heated blower desiccant styles may be used. This article describes three common desiccant dryer types, as well as some experiences, good and bad, with heated blower types.

This major food manufacturing plant in the Midwest uses compressed air and onsite nitrogen generation to operate multiple snack production and packaging lines. The plant spends an estimated \$430,344 annually on energy to operate its compressed air system based on an average rate of 4.5 cents per kWh.