Pressure and volume: what’s the difference?

Technician using manifold gauge to outdoor air compressor unit

Pressure and volume are often used as performance indicators for air compressors and indicate the maximum air volume and pressure produced by an air compressor.

Many air compressor users do not understand the important relationship between volume, or flow, and pressure.

To better understand both the difference and relationship between pressure and volume, let’s investigate these two essential factors in any compressed air system.

Manometer of an air compressor

Measuring pressure: pounds per square inch (PSI)

PSI (often listed as psi in air compressor specifications), measures how many pounds of pressure (force) are in an area, specifically in one square inch.

The force of the air is what gives compressed air its power. For example, the Pilot K25L18 Horizontal 3 Phase Reciprocating air compressor has 160 max. psi, meaning that 160 pounds of pressure are delivered per square inch.

Measuring volume: cubic feet per minute (CFM)

CFM measures the volume of air, in cubic feet, for each minute it moves, i.e. how much air can move per minute inside the air compressor. For example, the Pilot K25L18 Horizontal 3 Phase Reciprocating air compressor has an output rating of 12.9 CFM, which means that 12.9 cubic feet of air are flowing per minute.

worker checking the air filter regulator‎ pneumatic system factory

How are they related?

CFM and PSI relate to each other in an important way to ensure the proper function of any compressed air system. For an air compressor to operate and perform optimally, both CFM and PSI must be sufficient.

A helpful way to think about the relationship between pressure and volume is to think about the common garden hose. If you turn the tap on relatively low, water will flow out… perfect for filling up a watering can.

However, if you put your thumb over the space at the end of the hose, the water will shoot out with much more pressure than before. It’s the same volume of water, but the extra pressure will allow the water to travel faster and further.

It is a very similar concept when talking about air compressors. It is crucial that your system has sufficient CFM (volume of air), and enough psi (pressure) to give power to the air.

A man operating the air compressor machine

A common, and costly, air compressor mistake

Given the above explanation, it is understandable that many air compressor users who are experiencing low air pressure in their application simply increase the pressure on their air compressor.

This is a very common, and costly, mistake. Increasing air pressure creates artificial demand and increases energy consumption (and costs), wear and tear, and maintenance requirements. Before increasing the pressure on your compressed air system, it is important to first check for leaks, as a small open valve can dramatically reduce the air pressure.

Accurately determining your air compressor size prior to purchase and properly maintaining your compressed air system will also help reduce any issues with air pressure.

Extensive product range

Whether you’re after a custom-built air compressor or a catalogue product, Pilot Air’s extensive offering of Australian made systems offers a solution for all your needs, no matter the industry.

From air compressors through to compressed air storage, treatment and distribution, we’ve got you covered.

Our product range and large stock levels, combined with our comprehensive spare parts inventory, ensure we maintain your compressed air system’s reliability and efficiency while reducing whole-of-life operating costs.

Learn more about our compressed air products.

Air Compressor Products

From air compressors through to compressed air storage, treatment and distribution, our extensive range of compressed air products ensures we have the right solution for your business needs, no matter the industry or application. We also offer custom-built packages and compressed air systems that are fit for purpose and tailored to your budget.

Pilot K25L18 Horizontal 3 Phase Reciprocating
Pilot K25L18 Horizontal 3 Phase Reciprocating

The Pilot K25L18 Horizontal 3 Phase Reciprocating air compressor is built with high performance and heavy-duty componentry, twin cast iron cylinder and Italian made pump to ensure reliability and longevity.

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Pilot K25/21 Vertical 3 Phase Reciprocating
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The Pilot K25/21 Vertical 3 Phase Reciprocating air compressor features vertical configuration and a small footprint, which makes it ideal for environments with limited floor space. Built with high performance and heavy-duty componentry.

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Pilot K30P Trade Petrol Electric Start Reciprocating
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