Abstract
All pumps must be designed to comply with or meet the needs of the system. The needs of the system are recognized using the term Total Dynamic Head (TDH). The pump reacts to a change in the system. The elements of the TDH consist of four heads: Hs (the static head), Hp (the pressure head), Hv (the velocity head), and Hf (the friction head). The sum of these four heads is called the total dynamic head. This chapter also describes how to determine Hs and Hp and calculate Hf and Hv. The engineers Hazen and Williams derived their formula, a variation on the affinity laws, and introduced a correction factor for friction losses of about 15%. The H & W method is the most popular among civil and design engineers. It is the method to calculate friction losses that is required by most of the municipal water agencies. This chapter explains the Darey/Weisbaeh Formula and the Bachus & Custodio Formula, and the variable elevations, dynamic pressures, variable resistances, short-term resistance changes, and long-term resistance changes. Pumps in parallel and pumps in series are detailed individually and also the combined parallel and series pump operation.
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