Dust Control Handbook for Industrial Minerals Mining and Processing

Figure 1.1. Relationship between static, velocity, and total pressure [adapted from ACGIH 2010].Air traveling through a duct at a specific velocity will create a corresponding pressure known asthe velocity pressure (VP). Velocity pressure is the pressure required to accelerate the air fromrest to a particular velocity. It only exists when air is in motion, always acts in the direction ofairflow, and always has a positive value. For ventilation purposes, VP is measured with a testprobe facing directly into the airstream. The algebraic sum of static pressure and velocitypressure is total pressure (TP) [Hartman et al. 1997], as expressed by the following equation:where TP = total pressure, inches wg;SP = static pressure, inches wg; andVP = velocity pressure, inches wg.TP SP VP (1.1)The ACGIH handbook, Industrial Ventilation: A Manual of Recommended Practice for Design,[ACGIH 2010], gives a number of definitions and equations that are useful for describing airflowin an operation's ventilation system. The handbook also details fundamental characteristics inrelation to blowing and exhausting air through a plant ventilation system. A handbook fromMartin Engineering, Foundations: The Practical Resource for Cleaner, Safer, More ProductiveDust & Material Control [Swinderman et al. 2009], also devotes a chapter to the control of airmovement, including a section on effective measurement of air quantities. Finally, arecommended journal article is "Dust Control System Design: Knowing your Exhaust AirflowLimitations and Keeping Dust out of the System" [Johnson 2005].10 Fundamentals of Dust Collection Systems