How to calculate the velocity of compressed air in a pipeline

Written by ian kelly
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Knowing the velocity of compressed air delivered by a compressor allows you to select the correct machine to suit your air-driven tools, such as impact drills, staplers and spray-guns. Although there are a number of websites incorporating online compressed air calculators, using the compressed air velocity formula during your shopping expedition can help you arrive at an early decision without going online.

Skill level:
Easy

• Calculator

Instructions

1. 1

Using the following figures as an example: a) Compressor input flow rate = 750 cubic meters of ambient air per hour at 1 bar. b) Internal diameter of compressed air pipe (D) = 60mm. c) Compressed air flow rate (Q) = 75 cubic meters per hour at 7 bar; Calculate the velocity of compressed air (v) in the pipeline as follows:

2. 2

Rounding off the value of pi to 3.142, the formula for the velocity of compressed air (v) equals the compressed air flow rate (Q) divided by a quarter of the cross sectional area of the compressed air pipe (A). Therefore 75 cubic meters/hour divided by (0.25 x 3.142 x 0.060 squared) = Velocity of 26,552 cubic meters per hour.

3. 3

Calculate the per-second velocity as follows: Divide the per-hour velocity by the number of seconds in an hour. Therefore in the above example, 26,552/3600 = 7.4 cubic meters per second velocity.

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