In this Ask the Experts feature, which will run quarterly in Plant Services, expert instructors from the Compressed Air Challenge (CAC) will tackle your questions on compressed air systems and associated technology.
The Compressed Air Challenge is a voluntary collaboration of industrial end-users; manufacturers, distributors, and their associations; trade organizations; consultants; state research and development agencies; energy efficiency organizations; and utilities. The CAC has one purpose in mind—helping facilities enjoy the benefits of improved performance of your compressed air system.
The first question in this series: “My compressors are failing, and I need to buy replacements. What should I do to renew my compressed air system?”
Chris Beals (Denver CO, L1 Trainer): The first thing that should be done is to have a compressed air system review performed, in a product neutral way, by a qualified compressed air system auditor. Why product neutral? This is recommended to put the client’s best interests first, rather than promoting the interests of the service provider sales staff. Customers should have a discussion about this prior to contracting with a provider to perform the compressor air system review. The review should provide the end user with the proper size and types of compressors and dryers, and the information required to maximize the system efficiency and reliability. Armed with the information from the review, the end user can then request bids from their local compressed air equipment distributors. While price is often a major factor in whose compressors are selected, the end user should consider the vendor with the best service reputation, even if the compressed air equipment costs a little more.
For more information about selecting a service provider see “Guidelines for Selecting a Compressed Air System Provider” in the Compressed Air Challenge website library.
Greg Ashe (Kaeser Compressors, Denver, CO, L1&2 Trainer): Understanding why the existing equipment is failing should be the first step before new equipment is evaluated. Are they old and have run their course, due for maintenance, or installed in a harsh environment? Correcting the environment in which the compressors operate can make new equipment last longer while requiring less maintenance and maybe most importantly less downtime. Once the reason for failure is understood, we should look at how much air is needed and at what pressure.
A common practice is to replace existing equipment with identically sized new equipment, which assumes the original equipment was sized correctly and there haven’t been any changes to the compressed air demand. This is often a false assumption given that compressed air leaks are always growing and plant production is ever changing.
There are various levels of compressed air audits that can help size a new system, and arguably the larger the system the easier it is to cost justify a thorough study. The most complete studies include both the supply and demand side of the system, but smaller systems can also benefit from a simpler audit so long as it’s accurate.
Whatever the data, it’s important to have it properly interpreted and explained by an experienced professional because things are not always what they seem, and compressed air systems are no exception. Armed with a report on how much air is currently needed and, perhaps, an estimate of future air needs, if available, it’s finally time to look at new equipment options.
Bill Scales, P.E. (New Hyde Park, NY, L1&2 Trainer): Excellent question, which may address or raise other problems and additional questions. It is important to review maintenance records for each of the multiple (two, three, or four) compressors.
- Are they from the same manufacturer and about the same age?
- What are some of the reasons for individual compressor shutdowns?
- Is it a specific component that is common to each?
- Does the plant do its own maintenance or have a service agreement?
- Are manufacturing processes affected if one compressor shuts down?
- What are the design operating pressures of the compressors, and present compressor discharge pressures?
If you have taken the CAC’s Fundamentals of Compressed Air Systems training, you may have a copy of our Best Practices for Compressed Air Systems Manual. Refer to Section 2 titled “The Supply Side – Compressor Room Equipment,” which guides the reader through selecting compressors, treatment equipment, cooling methods, condensate removal methods, compressor controls and primary receivers, pressure/flow controllers, and methods of interconnecting components for optimum performance. To obtain a copy check out the CAC’s bookstore (https://www.compressedairchallenge.org/bookstore).
Do you have a compressed air related question you would like to ask our experts? Email [email protected] to request an answer.
One other thing, be sure to repair all compressed air leaks, and set pressures for compressors and the system at the lowest pressure that maintains production requirements.
Paul Shaw (Berlin, CT, L1&2 Trainer): I would start by understanding the existing system, both the pros & cons. What does it do well, what doesn’t it do well and why is there a need to replace it. I would then do a walk-through and data log the system to determine the demand side requirements for flow and pressure, check for leaks and inappropriate uses, and finalize how much compressed air is needed both for the present and possible future expansion.
I would also like to understand the current power costs and voltage, the existing piping network to see if it is adequate or needs improvement, and the budget for the project. Once we have that information, we can determine the type and size of the compressor, whether it needs to be oil-free or lubricated, the control type, and the storage, drying, and filter requirements. Energy efficiency, heat recovery, space requirements, and reliability should also be part of the final analysis.
Ron Marshall (Winnipeg, MB, L1&2 Trainer): One often overlooked item when considering replacing compressed air components is awareness. It is difficult to persuade the people buying the new equipment of the benefits of purchasing more efficient premium compressors and related components, because they don’t know what is possible. And often the users of the compressed air in the industrial plants do not know about the high cost of wasting compressed air through leakage and inappropriate use.
Since the electrical cost of producing compressed air is by far the largest part of the life cycle cost of an air compressor, often consuming more than the purchase cost in a single year, it pays to be educated about what options are available when purchasing compressed air equipment. Awareness of end use and waste reductions can also help; sometimes enough savings can be found on the demand side of a system to eliminate the purchase of one or more compressors and the associated components.
I would suggest sending key staff at least to our Fundamentals of Compressed Air Systems seminars to help them learn what is possible. Participation in our Advanced Management of Compressed Air Systems, and Compressed Air System Assessment & Project Development seminars can also lead to additional important knowledge of how to address complex compressed air problems and how to calculate possible savings. Also available is a User Awareness option.
This story originally appeared in the May 2022 issue of Plant Services. Subscribe to Plant Services here.