In this series we covered some very common issues in the Compressed Air Generation or “Supply Side” with regard to misapplying some capacity controls and installing different types of air compressors with piping and/ or orientation. These can preclude any reduction in compressed air demand on the production side from effectively translating lower air usage into a commensurate level input energy.
Analysis of the pressure data logging showed that, while the variable speed drive compressor maintained a constant discharge pressure near 120 psi, the pressure at various critical points fell to as low as 85 psi during peak production operations. General pressure in the plants, especially Plant 2, fluctuated between 102 and 112 psi, showing that the pressure/flow control valve was not regulating properly, and that Plant 2 lacked enough general storage volume to support transient flows.
A pharmaceutical plant, has had a compressed air assessment performed on two plant systems. The studies uncovered poor compressed air production efficiency, high air dryer loss, and problems with high flow compressed air uses negatively affecting plant pressure. The plant implemented energy efficiency measures, on the two compressed air systems, saving 46 and 64 percent in energy costs respectively.
In an ideal world, we would all have plenty of space, time and money to create the perfect compressed air system. In practice, we have to balance our ideals versus what we can actually accomplish. Compressed air systems take considerable forethought and planning to achieve a perfect install; however, we can use some key takeaways from this article even if we are ever faced a less than ideal installation. Remember to keep the compressors cool, minimize piping pressure drop and to allow sufficient room around the equipment for service.
One of the most common problems in plants is low air pressure. One of the most common solutions is to purchase new air compressors. Often this advice leads to a poor return on investment with the company’s hard-earned money. Often the issues are related to demand, distribution, or both. Solving the wrong problem can be expensive from a capital and operating cost perspective. Determining root cause analysis may cost more up front, but will save tens if not hundreds of thousands of dollars long term.
This article is going to identify two air compressor control situations that will preclude translating air use reduction in the production area into lower input energy into the air compressor.
Compressed air contains contaminants such as dirt, water and oil which must be removed before use. ISO8573.1 specifies air quality classes for these contaminants. Humidity is expressed in terms of Pressure Dew Point (PDP). PDP is the temperature at which air is fully saturated with moisture, when the air temperature falls below this point further condensation will occur.
Many are familiar with the advances with improved technology in the compressed air supply. Such advancements as, proactive central air compressor controls to maintain optimum operation of multiple compressors to support ever changing air demands; improved drive systems such as VSD’s; magnetic bearing drives (centrifugals); and more efficient and reliable equipment taking advantage of modern manufacturing capability. These new technologies are very important in generating relative high energy cost savings, and are well promoted by the OEM equipment manufacturers.
Their job is to brake the cars by gripping the wheels. They are operated either pneumatically or hydraulically, with Alton & Southern Railway’s system using the former. Considering much of Alton & Southern Railway’s compressed air piping system dated back to its 1960’s installation date, there were leaks. As of 2012, it was determined one and a half compressors were running at 100% capacity just to maintain leaks. This equated to about 1,500 cfm at a cost of roughly \$180,000 in electricity annually.
A Canadian poultry plant has upgraded their aging compressed air system for their new expansion, making it significantly more energy efficient and also solving ongoing pressure problems. The project has given the facility a much better system overall and increased system capacity enough to cover additional compressed air load. This article describes what was done to improve their compressed air system.
A zinc producer spends an estimated \$516,000 annually on electricity to operate the air compressors in a compressed air system at its north American plant. The current average electric rate, at this plant, is 5 cents per kWh, and the compressed air system operates 8,760 hours per year. This system assessment recommended a group of projects able to reduce these energy costs by fifty-one percent (51%) to an annualized \$270,000. The simple payback of the project was 15 months – without taking into account potential incentive dollars from the local utility.