Industrial Utility Efficiency    

Compressor Controls

Load-sharing is an important part of a multiple centrifugal-compressor master control system. It minimizes blow-off based on the available turn-down. In addition, remote start-stop saves more energy if load floats between different ranges. Finally, adding a screw compressor and implementing a hybrid control system might save the most energy and provide the best back-up. In any case, a well-instrumented system allows engineers and operators to assess, optimize and tune the system.
After getting its start manufacturing cost-effective products to the healthcare industry, 40 years later, 1888 Mills has become the fourth largest towel manufacturer in the world, and the largest towel manufacturer in the U.S. With facilities in the United States, Pakistan and Bangladesh, 1888 Mills’ towels are used in almost every corner of the world. 1888 Mills is recognized as a leader in innovation in the textile industry and produces 176,000 pounds of towels per week.
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.
The plant produces both molded and blow molded plastic parts on a 5 day per week, three shift schedule. Production and maintenance sometimes occurs on weekends, occasionally requiring the air compressors to run on a 24 x 7 basis so the practice was to leave the compressed air system always pressurized. The system consisted of three modulating lubricated screw compressors one sized at 150 hp and the others 125 hp (3 units), each controlled with their local compressor controllers.
When a system has the right combination of VFD and base-load air compressors, how do you coordinate their control? What tells the air compressors to run and load, to have just enough (or no) base-load air compressors and a VFD running, all the time air is needed? Appropriate master controls are needed. These controls are often called “sequencers” or “master control systems”.
A newly constructed ethanol plant experienced control gap issues shortly after comissioning.  This article discusses the cause of the issue and how the problem was solved.
A large pharmaceutical company needed huge flow rates of 30 psig air to aerate multiple fermentation processes which create food-grade materials.  Flow could vary from about 12,000 scfm to 35,000 scfm.  There were a variety of batch processes, mostly running independently.  An hour-by-hour schedule for anticipated air flow is developed every afternoon for the next day.  Based on that schedule, the boiler operators run the air compressors that can handle the load range for the whole day. In reality, the peak flow can be higher than anticipated.
Quite often the typical variability in compressed air flow demand does not proportionately translate into power reductions at the air compressors. This can be a result of numerous problems with the compressed air supply system. It is important to understand the supply-side’s ability to respond to the demand-side of the compressed air system. If the air compressors, on the supply-side, are not able to translate flow reductions into energy savings, implementation of demand reduction projects should be re-evaluated.  
Optimal compressed air system performance, defined by efficiency, reliability and air quality, has now become the main goal when operating, installing, purchasing or designing compressed air products. Whether you are the air compressor manufacturer, distributor or end user - everyone in the compressed air industry needs to be aware and work towards these goals.
The objective of this project is to help the building automation industry develop novel products that more cost-effectively identify faults (unwanted conditions) and inefficiencies in the operation of the compressed air plants of industrial facilities.  More cost-effective fault detection and diagnostics (FDD) products can come to the building automation marketplace only after that industry makes very significant advances in the state-of-the-art of its FDD software tools from what it currently offers.  Those advances require making common practice of rules-based artificial intelligence (AI) methods that the building automation industry has shown little to no familiarity with in its technology so far.  This project will utilize, under controlled conditions, the compressed air plant of the NIST campus as a facility for test and development of an embedded rules-based FDD tool based upon NIST expertise.
One of the statements made in the Compressed Air Challenge’s Fundamentals of Compressed Air Systems seminar is that improvements can always be made to every compressed air system, including new ones. The statement definitely applies to a Canadian pork processing facility built a few years ago. This article is based on a compressed air audit performed two years into the life of a brand new plant. The audit found numerous problems and made recommendations that helped reduce plant compressed air operating costs by 60 percent.