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| How can any Building System be explained? Our first answers is: by FLOW DIAGRAMS: A well-conceived flow diagram will be beneficial to all users, particularly the owner's present and future operation-and-maintenance personnel. This alone should be adequate incentive for designers to devote extra thought to preparing and revising flow diagrams so that they quickly communicate the design intent. The following are benefits of a well-designed flow diagram: * It allows owners, architects, and others to quickly understand a system. For use in presentations during the proposal or schematic phase of a project, it could be annotated to show equipment capacities, flow quantities, entering-and leaving-fluid temperatures, pump data, and system pressures. * It is an excellent means of communicating a system to others, including the designer's supervisors, quality-control reviewers, draftspersons, specification writers, control-system designers, owners, operators, installers, service technicians, code personnel, and test-and-balance and commissioning personnel. * It enhances the understanding of individuals involved in designing, commissioning, optimizing, and troubleshooting the overall system and the control system, as well as individuals involved in modifying those systems in the future. * It serves as a training aid for designers, plant operators, and maintenance personnel. * It is a valuable aid to installers. Installers who understand intent and function often do a better job not only of installing, but of testing, commissioning, troubleshooting, diagnosing, and servicing systems. * It can serve as an easy check for takeoff (materials listing) and ordering of piping components, including valves, instrumentation, piping specialties, balancing taps, heat tracing, chemical feed taps, and control/building-automation-system sensors. * It can be a valuable aid in the value and energy engineering of a system, as it makes apparent the locations where central-plant isolation valves are beneficial, where pump valves and equipment valves in series may be omitted, where check valves are required, and, in some cases, where check valves serve no purpose. * Pressure or pressure drop may be added to the diagram temporarily to provide the motivation necessary to redesign the system in an effort to reduce parasitic pumping power. * It can be useful in evaluating how the system will perform at part load or in an emergency. * It can be an aid in determining if a system can be economically balanced and rebalanced. * It can be used for recording temperatures and pressures (BMS) in an effort to understand the system and correct problems. Figure 1 (below) is an example of a chilled/condenser water flow diagram that does not instantly convey a clear picture. It defies quick comprehension and is an obvious candidate for improvement:  Figure 1 Figure 2 (below) is a simple revised version of the same flow diagram, one that would be more useful to reviewers, installers, operators, and troubleshooters.  Figure 2 Figure 3 (below) illustrates the type of flow diagram that GNACE used on one of the completed projects. It is not easy to interpret it without a great deal of study and reviews.  Figure 3 Why are the flow diagrams so important in a project? Whom will it benefit? Will it result in a better installation? Will it improve operation and maintenance? Will it decrease design risk or liability? These questions lead to an examination of who might use a flow diagram. Such individuals are:
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 | There is a philosophy in addressing technical problems: If you can't draw a picture of it, you don't understand it. The reverse is also generally true. The flow diagram ... enables the Engineer to achieve understandable simplicity and readily identify designed-in problems, serves as an aid to the installing agents in interpreting construction diagrams, and provides an invaluable tool in the ongoing operation and diagnostic servicing of system problems. The flow diagram, well-developed, will immediately reveal the design philosophy of the system. George Nestor, P.E. Principal George Nestor Associates Consulting Engineers. |
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GNACE Main Office: 986 Middle Tpke. Storrs, CT 06268 USA Tel: (203) 981-3815, Fax: (860) 429-6400 New York, NY: (917) 805-7666 Norwalk, CT: (347) 421-3090 E-mail: Info@GNACE.com |
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