Mechanical (Questions & Answers)

Summary Centrifugal pumps perform many important functions to control the built environment. The physics and basic mechanics of pumps have not changed substantially in the last century. However, the state of the art in the application of pumps has improved dramatically in recent years. Even so, pumps are still often not well applied, and become common targets in retrocommissioning projects where field assessment and testing can reveal significant energy savings potential from optimizing pump performance. Typically, retrocommissioning finds that pump flow rates do not match their design intent and that reducing flow rates to match load requirements or eliminating unnecessary pressure drops can save energy. As the example below illustrates, decisions made during the design phase have implications throughout the operating life of the building. Although fully optimizing any design will require some effort after installation, the prevalence and magnitude of the savings that are commonly found in retrocommissioning and ongoing commissioning begs the larger question: How much greater would the savings be if pumps were selected and applied optimally during the design phase?

Purpose of this Guide to pump procurement This Guide provides an introduction to the very complex subject of the selection of pumps. It is aimed at anyone who wishes to purchase or select a pump and, at the same time, wishes to save money on their energy bill. Almost invariably, this saving will be far more than the first cost of the pump. The reader may be the end user, a contractor, or a consultant. This Guide provides the reader with the basic principles of pump procurement, giving pointers to the pump type and performance they should consider. Pumps are divided into their main types, then their basic construction and performance are considered, their principal applications are described, the basic principles of pump selection are explained and, last but not least, target efficiencies are set to help minimize energy usage. The hope is that both pump users and the environment will benefit.

Objectives Understand pump fundamentals Understand the probable root causes of degradation or failure associated with various pump problems Understand the state-of-the-art technologies to upgrade existing designs to achieve improved operation and life Learn how to determine where a pump is operating and how to modify its performance to achieve optimum performance