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Pressure Drop
Pressure drop is the difference in total pressure between two points in a network, such as a compressed air system. In other words, it is a loss in pressure in a compressed air system or one of its components due to friction or restriction.
Any compressor system will experience some pressure drop. However, excessive pressure drop matters because the air compressor must work harder to deliver the air pressure required for your application. This increased effort creates higher energy consumption and reduces equipment performance.
FAQs
The calculation you use to determine pressure drop varies, depending on whether you are designing a system or determining the pressure drop in an existing setup.
When designing a system, you can estimate the pressure drop using this formula:
Δp = 7.57q1.85L104 / (d5p)
Here’s what each part means:
- Δp: Pressure drop in psi
- q: Air volume flow at atmospheric conditions in standard cubic feet per minute (scfm)
- L: Length of pipe in feet
- d: Inside diameter of the pipe in inches
- p: Absolute pressure in psia
If you have an existing air compressor system, you can calculate pressure drop much more easily. Install pressure gauges at various points in the system, such as right after the compressor discharge and right before the point of consumption. Compare the two values to determine the total pressure drop. You can also compare pressure drop in smaller system segments by installing additional gauges, like before and after the air dryer or inline filters.
The pressure may drop in your air compressor due to obstructions in airflow, friction or air loss. Various compressed air system components and distribution system parts cause these issues. Here are a few common reasons for air compressor pressure drop:
- Undersized pipes that introduce excessive friction to the air
- Poorly designed distribution systems with long piping, joins, turns and elbows
- Corrosion, which roughens pipes and increases friction
- System leaks, which create loss of air and a turbulent flow pattern
- Blocked inline filters, which increase the energy needed to push air through
- Undersized air dryers that can’t process the volume of air the compressor produces
- Any other components between the air receiver tank and the endpoint
- Water or other substances circulating through the system, creating resistance to flow
While some degree of pressure drop is inevitable, you can do several things to reduce the amount, including:
- Considering system design: Whether implementing a new system or looking for ways to improve your existing one, you can do several things during the design phase, such as selecting properly sized piping, minimizing piping length and choosing the right compressor for the application.
- Performing regular maintenance: Maintenance helps you clear blockages and prevent air quality issues that may cause a pressure drop. Clean filters and check dryers, seals, connectors and piping for potential problems. Also, monitor pressure with gauges to identify concerning areas.
- Choosing high-quality components: From the piping you choose to additional air treatment systems, do your research to find options designed for minimizing pressure drop.
These steps enable you to minimize pressure drop, improve energy efficiency and reduce compressed air costs.
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