ASME EA-2G-2010 pdf free.Guidance for ASME EA-2, Energy Assessment for Pumping Systems.
2.2.2 Prime Movers. Most pumps are driven by electric motors. Although some pumps are driven by direct current (dc) motors, the low cost and high reli- ability of alternating current (ac) motors make them the most common type of pump prime mover. Energy- efficient motors are standard in today's marketplace, and "premium efficiency" motors are widely available in common sizes and enclosures. In high run-time appli- cations, improved motor efficiencies can significantly reduce operating costs. However, the assessment's focus should typically be on a systems approach, where atten- tion to systems issues such as component sizing, pip- ing configuration, and maintenance practices typically identifies the greatest energy savings opportunities. A high efficiency motor usually operates at a higher speed than an older, less efficient motor. The pump might therefore create higher pressure and flow and consume more energy if no other changes are made to the system. When changing to a more efficient motor, system effects should therefore be taken into account. Steam turbines and other devices, although much less common, are also used to power pumping systems.
2.2.3 Piping. Piping is used to contain the fluid and carry it from the pump to the point of use. The critical aspects of piping are its dimensions, material type, and cost. Since all three aspects are interrelated, pipe sizing is an iterative process. The flow resistance of a pipe at a specified flow rate is highly dependent on pipe size, and decreases as the pipe diameter gets larger. For example, increasing pipe diameter by 10% can result in a pressure drop of more than 60%。However, larger pipes are heav- ier, take up more floor space, and cost more than smaller pipe. Similarly, in systems that operate at high pressures (for example, hydraulic systems), small- diameter pipes can have thinner walls than large- diameter pipes and are easier to route and install.
2.2.5.2 Mechanical Seals. Mechanical seals are typically used in applications that call for superior sealing. The effectiveness of mechanical seals is highly dependent on correct installation and a continuously clean operating environment. Mechanical seals have two primary failure mechanisms: degradation of the face material and loss of spring or bellows tension, which allows the faces to separate more easily. Degradation of the seal face is usually caused by debris that wedges into a seal face and causes damage. To minimize the risk of this type of damage, mechanical seals are often serv- iced by special flushing lines that have filters to catch debris. Seal faces are held together by a force that is usu- ally provided by springs or bellows. However, compres- sive properties are often lost because of fatigue, fouling, and/ or corrosive environments, which degrade spring and bellows materials. To minimize fatigue loads on mechanical seals, the seal must be precisely aligned so that spring movement is minimal during each shaft rev- olution. For more information on mechanical seals, see reference [6] in Nonmandatory Appendix A. ASME EA-2G pdf download.