Busting the myth that “another compressor” is always the answer
Compressed air is a commonly used power source in manufacturing facilities, but it isn’t necessarily a cheap one. Aided by the Compressed Air Challenge movement, which started 20 years ago, users have started treating compressed air as a utility with supply and demand.
This has led to a greater understanding of how to use compressed air efficiently, but many facilities are still running on systems that are not optimized.
It’s not a pressure problem, it’s a volume problem
Imagine a room full of production equipment that requires compressed air. The compressed air flows to the equipment from a system typically consisting of one or more compressors, a storage tank and a system of pipes to route the air to the points of use (the supply).
Each point of use periodically requires an amount of compressed air to perform its task (the demand), and will draw air from the system to do so. When that happens, system pressure drops accordingly — including the storage tank — and at some point, another compressor starts to restore the pressure to the set point. However, it takes time for the machine to start, reach the proper RPM and load up to produce the needed volume.
What happens when the cycles of all of the pneumatic equipment in the room align and they all require compressed air within the same five-second window?
The demand peaks, but is there enough “supply” to match it?
Often, demand “events” like this occur and pass before the supply system is able to respond — but people notice, and the manufacturing equipment is affected. Mechanical jams, misaligned cartons and over/under fills are all examples of uptime-robbing and defect-producing symptoms that can hurt manufacturing efficiency.
If another demand event occurs before the system pressure has time to recover from this major depletion, your process suffers even more.
Operators often diagnose this problem as a need for more air compressors (or more storage capacity).
But in this scenario, that’s not the case: Adding more energy-sucking compressors to the system wouldn’t address the problem. The actual problem is that there was no separation between the supply and demand. An optimized compressed air system is designed such that the supply is capable of meeting peak demand events without a noticeable change in demand pressure or the unnecessary starting of another compressor.
Separating supply and demand to create a supply “reserve”
The reason air pressure plummeted in the above scenario is because the compressors were unable to pack the system with enough volumes of air to maintain the required pressure in time to survive the high-demand event.
But what if you could have a reserve of compressed air volume so that you never have more demand on your plant floor than supply in your storage tank? Now we’re getting at the heart of optimizing your system.
Let’s say our original equipment manufacturer (OEM) recommended a minimum pressure of 100 psi for a machine to run at rated speed. Operators often add a buffer to this and operate the compressed air system at that pressure (let’s say 125 psi for this example).
While the equipment may have been tested by the OEM at 100 psi, and while it may run just fine at 100 psi, often the hardest-working air user on that machine may really only require 60-70% of that to accomplish the task at speed. But, how do you know?
Powering compressors to create more compressed air pressure than you need is not only a waste of energy, it’s a horrible operating philosophy!
So, what’s the solution?
Upgrade or update your system with proper instrumentation that allows you to control supply and demand of your compressed air separately, giving you the ability to store a “reserve” of pressurized air. This way, when even the worst-case demand event on your plant floor occurs, it will never outweigh your available supply. That means a more energy-efficient system and reduced risk for costly downtime.
What’s the bottom line?
Pressure controls alone cannot provide the “resolution” needed for efficient and trouble-free operation, no matter how much storage volume you have.
An optimized system balances supply and demand using modern instrumentation to measure and control pressure and flow, along with properly (and sometimes strategically) designed storage volume and pipe sizing.
When your system is engineered properly and a peak demand event occurs, the users on the demand side of your process may not notice events, and the supply side can take it’s time repacking the stored volume, usually without requiring another compressor.
A compressed air system is often the biggest energy user in the plant. Optimizing your compressed air system can yield impressive energy savings at your facility. And, if you’re experiencing defects and or downtime attributable to compressed air performance, the value can be even higher.
Where do I go from here?
If your compressed air system has been giving you headaches, consider having it examined. Hire a qualified contractor to perform a compressed air audit in which they analyze the conditions at the plant, measure usage and gather enough data to create a baseline profile. From this, a scope of work can be created for modifications needed to optimize.
The return on investment is almost always enough to fund the project.
If you’re considering a new facility, don’t skip the design of the compressed air system. Ensuring it’s optimized from the beginning can go a long way towards being the low-cost leader.
Finally, always look for and eliminate wasteful uses of compressed air in your manufacturing wherever possible. Leaks? Yes, fix them. But if your process lines have even one component that uses compressed air to blow something across, into, off of or through something else, it’s a volume hog and a wasteful use of energy. Chances are there’s a cheaper way to do it.
Want to learn more about compressed air system efficiency and system audits? Comment below or email me at firstname.lastname@example.org