ASME EA-2G-2010 pdf download

ASME EA-2G-2010 pdf download.Guidance for ASME EA-2, Energy Assessment for Pumping Systems.
1 GeneraL 1.1 Scope This guidance document provides an application guide on how to utilize ASME EA-2, Energy Assessment for Pumping Systems. This guidance document pro- vides background and supporting information to assist in applying the Standard. 1.2 Purpose ASME EA-2 does not provide guidance on how to perform a pumping system energy effciency assess- ment, but sets the requirements that must be performed during such an assessment. EA-2 was written in a form suitable for a standard, with concise text and without examples or explanations. This document was devel- oped to be used in conjunction with the standard to give basic guidance on how to fulfll the requirements of the standard. This document is only a guide and does not set any new requirements. ASME EA-2 can be used with or without this document. 2 introduction to PuMPinG SySteMS 2.1 overview Pumping systems are used widely worldwide to pro- vide cooling and lubrication services, to transfer fuids for processing, and to provide the motive force in hydraulic systems. In fact, most manufacturing plants, commercial buildings, and municipalities rely on pumping systems for their daily operation. In the manufacturing sector, pumping systems represent 27% of the electricity used by industrial systems. In the commercial sector, pump- ing systems are used primarily in heating, ventilation, and air-conditioning (HVAC) systems to provide water for heat transfer and water pressure boosting of domes- tic potable water. Municipalities use pumping systems for water and wastewater transfer and treatment and for land drainage. Since pumping systems serve such diverse needs, they range in size from fractions of a horsepower to several thousand horsepower.
It is important to keep in mind that pumping systems are often parts of larger systems, such as complex indus- trial processes or HVAC systems. Therefore, potential impacts on the larger systems should be considered when evaluating pumping systems. 2.2 components Typical pumping systems contain fve basic com- ponents: pumps, prime movers, piping, valves, and end-use equipment (e.g., heat exchangers, tanks, and hydraulic equipment). A typical pumping system and its components are illustrated in Fig. 1. 2.2.1 Pumps. Although pumps are available in a wide range of types, sizes, and materials, they can be broadly classifed into the two categories: positive dis- placement (PD) and centrifugal. These categories relate to the manner in which the pumps add energy to the working fuid. Positive displacement pumps move a set volume of liquid per revolution or stroke, and pressure is developed as the liquid is forced through the pump discharge into the system. Centrifugal pumps work by adding kinetic energy to a fuid using a spinning impel- ler. As the fuid slows in the discharge passage of the pump, the kinetic energy of the fuid is converted into pressure. Centrifugal pumps include axial (propeller), mixed-fow, and radial types.
2.2.4 Valves. The fow in a pumping system may be controlled by valves. Some valves have distinct posi- tions, either shut or open, while others can be used to throttle fow. There are many different types of valves; selecting the correct valve for an application depends on a number of factors, such as ease of maintenance, reli- ability, leakage tendencies, cost, and the frequency with which the valve will be open and shut. Valves can be used to isolate equipment or regulate fow. Isolation valves are designed to seal off a part of a system for operating purposes or maintenance. Flow- regulating valves either restrict fow through a system branch (throttle valve) or allow fow around it (bypass valve). A throttle valve controls fow by increasing or decreasing the fow resistance across it. In contrast, a bypass valve allows fow to go around a system compo- nent by increasing or decreasing the fow resistance in a bypass line. A check valve allows fuid to move in only one direction, thus protecting equipment from being pressurized from the wrong direction and helping to keep fuids fowing in the right direction. Check valves are used at the discharge of many pumps to prevent fow reversal when the pump is stopped. 2.2.5 Seals and Sealing Systems. The point at which the shaft penetrates the pump casing, known as the stuffng box, provides a leak path that must be sealed. This area is normally sealed using packing or mechan- ical seals. For systems in which fuid leakage is not a signifcant concern, packing is usually used because it is much less expensive and requires less sophisticated maintenance skills. Mechanical seals provide supe- rior sealing, but they are typically more expensive and harder to repair or replace. Most pumps sold today are provided with mechanical seals. Auxiliary systems are sometimes necessary to control the environment in which the seal operates.