tailieunhanh - Ebook Centrifugal pumps - Design operation and maintenance: Part 2

centrifugal pump design and construction, pump hydraulics, forces in centrifugal pumps, centrifugal pump operation and characteristics | 6 Pump specification and selection Centrifugal pumps are used for a wide variety of applications. These applications may or may not be critical in nature. In some instances, it suffices to buy a pump off-the-shelf merely on the horsepower rating of its motor or by its overall dimensions. The pumps procured in the above manner may not provide the best fit of the pump to the application, but the penalties associated with such a mismatch may not be significant. However, in process industries, the pumps have to perform vital functions on a continual basis. In difficult environments, there are significant penalties associated with downtime and maintenance costs. It then becomes important to specify the process and its requirements. This aids in a selection of a pump, which is designed and manufactured with features such that it can operate under specified conditions in a reliable, efficient, and cost-effective manner. A good pump specification is often considered as the foundation or the basis of pump reliability over its years of operation. It is the first document prepared for a pump by the user and is often the most vital. A pump specification is a document that is preceded by: • System analysis (covering the hydraulic aspects) • Mechanical requirements. Preparation of a pump specification document is a multidisciplinary team effort, which involves the process engineers, mechanical engineers, contractors, and the pump vendors. Once a pump specification has been laid out, it is followed by a bid request, a bid analysis and this process finally culminates with the selection of the right pump. Failure to define or specify the pump completely for the anticipated process conditions often results in poor operating experience and high maintenance costs. In any pump specification, the following process requirements are of prime importance: • • • • Maximum differential head at the specified flow rates Available Net Positive Suction Head, NPSH-a Anticipated flow range or the

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• Applied multivariate statistical analysis
• Statistical analysis
• Multivariate analysis
• Multivariate linear regression models
• Canonical correlation analysis
• Distance methods
• Several multivariate means
• Sample geometry
• Random sampling
• Instrumental analysis
• Units and measurements
• Mathematical concepts