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Total Pressure
Total pressure is the amount of pressure produced when stopping a moving stream of compressed air or gas in an air compressor. It is the pressure measured by an impact tube when placed directly in an airstream.
When compressed air moves through a compressor’s piping, it carries pressure energy and velocity energy. An impact tube facing into the airflow captures both energies by bringing the moving air to a complete stop. This stopping action reveals the total pressure at that location.
Total pressure measurements help operators assess the complete energy state of compressed air as it travels through distribution systems. Unlike static pressure measurements taken perpendicular to the flow, total pressure accounts for the kinetic energy of moving air for a more comprehensive picture of system performance. The measurement is useful for evaluating flow conditions, diagnosing restrictions and verifying that equipment receives the right amount of pressure to operate effectively.
Why the Bernoulli Equation Is Important in Total Pressure
As a fundamental principle of fluid dynamics, the Bernoulli equation explains why impact tubes measure total pressure by stopping the flow of moving air. According to this equation, the total pressure equals the sum of the static pressure and the dynamic pressure at any point in a flowing system.
Static pressure represents potential energy — the force against pipe walls measured perpendicular to flow. Dynamic pressure accounts for kinetic energy from air movement. When an impact tube stops the airstream, it converts all dynamic pressure back into static pressure, allowing measurement of total pressure.
This relationship explains pressure behavior in compressed air systems. As air flows through valves or smaller piping, velocity increases, and dynamic pressure rises. Static pressure must decrease proportionally. The total pressure remains relatively constant in an ideal system.
FAQs
Total pressure measurements enable operators to verify that their system supplies sufficient energy to their power tools and equipment. When total pressure drops significantly between measurement points, it indicates energy losses that reduce efficiency. These losses force the compressor to work harder, increasing power consumption.
Monitoring total pressure at key locations helps identify restrictions, leaks or design issues affecting performance.
Understanding the different pressure types helps operators identify whether pressure drops stem from velocity changes or restrictions:
- Static pressure: The force compressed air exerts when at rest, measured perpendicular to the flow
- Dynamic pressure: The kinetic energy from air movement, which increases with velocity
- Total pressure: The sum of static and dynamic pressure at any system point
Install pressure gauges at key points throughout your distribution system — near the compressor discharge, at major branch points and close to critical equipment. Regular readings help establish baseline performance and identify developing issues. Quincy Compressor’s network of professional and knowledgeable air experts can design monitoring strategies tailored to your operational needs.
Both compressor types produce total pressure the same way, but their operating characteristics affect how that pressure develops. Reciprocating piston compressors produce air in pulses, which can create pressure fluctuations that storage tanks help smooth out. Rotary screw compressors deliver more continuous airflow, typically resulting in steadier pressure readings.
Measurement locations and techniques are the same for both compressor types.