By: Stephen Horne
We all know that plant pressure is important. When it’s too low, tools don’t operate correctly, processes fail, and tempers flare. Which is probably why there’s a fairly unhealthy—or at least a somewhat inefficient—relationship with pressure. But, if you take the time to get in the pressure zone you can reduce scrap, improve air quality, and lower operating costs. Here’s how.
How Does Pressure Impact Plant Operating Costs?
When pressure drops, there tends to be a knee-jerk reaction to fix it—production is critical, so turning up the pressure setting on the compressor seems logical. The problem with this myopic view is that it fails to address underlying issues causing the pressure drop. It also turns a blind eye to increased operating costs.
For typical plant air systems, every 2-psi increase in system pressure increases power consumption approximately 1%. Increasing the pressure also increases the air lost through leaks and any other unregulated use. So it’s a lose-lose.
It’s important to understand why you are having problems with pressure drop in your system. For example, if you notice there are short intermittent demands for a specific part of your process ——look at adding storage for that specific application. It will reduce the impact on the rest of your system.
If tools are under-pressurized, check the size of the line. Many times plants will add on tools as their process demand increases, but they never increase the size of the line. This is a common cause of pressure drop that can easily be fixed.
Another cause of low pressure is lack of control for multi-unit systems. The classic symptom is compressors that are short cycling—rapidly turning on and off because they are independently responding to pressure signals too close to the compressors. Add a system master controller that can monitor your system pressure further downstream and select the right mix of compressors to meet demand. This will save a lot of power and reduce wear and tear on compressors.
So the bottom line is fix the problem instead of raising the pressure. Reducing system pressure saves money in other ways as well. Lower system pressure means lower operating temperatures, which lowers the temperature of the lubricant and extends its life. Additionally, there will be less condensate in the system. This means less wear and tear on filters, and as a result, extended filter life.
Adding Pressure Zones in a Plant
Another approach is to create pressure zones in your plant. Take a look at your processes and identify which parts need different pressure ranges. You can then selectively use different technology to supply the appropriate pressure.
For aeration, agitation, air knives, pneumatic conveying, or other processes that require lower pressures, blowers may be a more cost effective solution. When considering this alternative, you’ll want to do the math and consider the ROI. If, for example, you only have a few air knives, it may not pay to install a separate blower system but it will definitely pay to buy air nozzles designed for the task rather than drilled pipe or other homemade solutions. On the other end of the spectrum, if you have a specific application requiring a higher pressure, use a booster for only that part of the process instead of the entire system.
Alternately, you can use a flow controller if you have a portion of the plant that runs below regular plant pressure. For example, plant pressure is 100 psig but you have one or more large applications running at 60 or 80 psig, isolate that part of the plant with a flow controller. This will save a lot of air for other parts of the plant. Learn more about how to properly apply flow controls in this whitepaper.
Taking a little more time to take a closer look will help you understand the pressure needs of your system. As a result, you’ll save money and improve the overall health of your equipment. So the next the time you are tempted to crank the pressure up, take a step back and get in the pressure zone. Your system will thank you for it.