# Compressed air problem (pressure and flow rate calculations)

• tenichols94
In summary, the conversation discusses the difficulty of finding resources for making calculations to predict pressure and flow rate in a compressed air system. The suggested resource is the book "Compressed Air and Gas Data, Second Edition" which includes tables for line loss and specific flow rates for various components in the system. The conversation also explains the process of determining the total pressure requirement at the source based on the required flow rate at the tool and the pressure drops of each component in the system.
tenichols94
TL;DR Summary
When dealing with a compressed air system I would like to know how to make some calculations to predict pressure and flow rate throughout a system.
When dealing with a compressed air system I would like to know how to make some calculations to predict pressure and flow rate throughout a system.

e.g.
If I have a compressor that can supply 50 cfm @ 100 psi at the source, and the air flows through a system of pipes, filters, turns, etc. which causes head loss, and let's assume the head loss is known. If I have a pneumatic tool that runs at 75 psi, what type of flow rate could I expect?

This type of question is common is industry and I found it difficult to find resources regarding this type of question. Yes, there is general information but no clear way to make "rough" predictions.

See Bird, Stewart, and Lightfoot, Transport Phenomena chapter on macroscopic balances

berkeman
Get a copy of Compressed Air and Gas Data, Second Edition, edited by Charles W. Gibbs. It's out of print, but available used from Amazon: https://www.amazon.com/dp/B000YB9ZJ2/?tag=pfamazon01-20. If you are working with compressed air, this book should be on your desk.

Chapter 34 has tables giving the line loss for various sizes pipe, pressures, and flow rates. Exactly what you need for good rough predictions. You will need to get the air flow rate for a specific tool from the manufacturer.

jrmichler said:
Get a copy of Compressed Air and Gas Data, Second Edition, edited by Charles W. Gibbs. It's out of print, but available used from Amazon: https://www.amazon.com/dp/B000YB9ZJ2/?tag=pfamazon01-20. If you are working with compressed air, this book should be on your desk.

Chapter 34 has tables giving the line loss for various sizes pipe, pressures, and flow rates. Exactly what you need for good rough predictions. You will need to get the air flow rate for a specific tool from the manufacturer.
Wouldn't the air flow rate depend vary? If the gauge at the tool is set @75psi for example, wouldn't the flow rate depend on the system? That's what I'm struggling with.

tenichols94 said:
wouldn't the flow rate depend on the system
Yes.
tenichols94 said:
That's what I'm struggling with.
Get the book! It is a good one, and practical.
I found it difficult to find resources regarding this type of question.
Get the book! It is only ten dollars.

gmax137 said:
Yes.

Get the book! It is a good one, and practical.

Get the book! It is only ten dollars.
I'll check it out. Thanks!

berkeman
I'll expand a little...
tenichols94 said:
Wouldn't the air flow rate depend vary?
Yes! You have to work a problem like this backwards from the tool. The tool has a specific flow rate required, at a specific pressure. Then every component in the system (pipes, filters, turns, etc.), also has a specific pressure drop at that required flow rate. Add them all up with a spreadsheet, and you get a total pressure requirement at the source.

So this statement is backwards:
If I have a compressor that can supply 50 cfm @ 100 psi at the source, and the air flows through a system of pipes, filters, turns, etc. which causes head loss, and let's assume the head loss is known. If I have a pneumatic tool that runs at 75 psi, what type of flow rate could I expect?
The pressure drop through the system isn't known based on the supply device, it is determined based on the load. The supply device just needs to be able to supply enough flow at enough pressure to satisfy the system and load.

Asymptotic

## 1. What is compressed air and how is it used?

Compressed air is air that has been pressurized to a level higher than atmospheric pressure. It is commonly used in industrial and commercial settings for various purposes such as powering tools and machinery, cleaning, and transporting materials.

## 2. What factors affect the pressure and flow rate of compressed air?

The pressure and flow rate of compressed air are affected by several factors, including the size and type of compressor, the temperature and humidity of the air, the length and diameter of the air pipes, and any obstructions or leaks in the system.

## 3. How is the pressure and flow rate of compressed air calculated?

The pressure of compressed air can be calculated using the ideal gas law, which takes into account the volume, temperature, and number of moles of gas. The flow rate can be calculated using the Bernoulli's equation, which considers the pressure, velocity, and density of the air.

## 4. What are some common problems with compressed air systems?

Some common problems with compressed air systems include inadequate pressure or flow rate, leaks in the system, and moisture buildup. These issues can lead to decreased efficiency, increased energy costs, and potential safety hazards.

## 5. How can I troubleshoot and solve a compressed air problem?

If you are experiencing issues with your compressed air system, it is important to first identify the source of the problem. This may involve checking for leaks, cleaning or replacing air filters, and adjusting the pressure and flow rate settings. If the problem persists, it may be necessary to consult a professional or refer to the manufacturer's instructions for further troubleshooting steps.

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