3.8.2    Pump selection

The pump is the heart of the pumping system. Its choice is driven by the need of the process which could be, first of all, a static head and a flowrate. The choice also depends on the system, the liquid, the characteristic of the atmosphere, etc.
In order to obtain an efficient pumping system, the choice of the pump has to be done so as to have an operating point as close as possible to the best efficiency point as indicated in Figure 3.35.

Figure 3.36 shows the ranges of total head as a function of the pump capacity for a given speed in different types of pumps.
It is estimated that 75 % of pumping systems are oversized, many by more than 20 %. Oversized pumps represent the largest single source of wasted pump energy.
When choosing a pump, oversizing is neither cost nor energy efficient as:
●the capital cost is high
●the energy cost is high because more flow is pumped at a higher pressure than required. Energy is wasted from excessive throttling, large by passed f lows, or operation of unnecessary pumps.
Where oversized pumps are identified, their replacement must be evaluated in relation to other possible methods to reduce capacity, such as trimming or changing impellers and/or using variable speed controls. Trimming centrifugal pump impellers is the lowest cost method to correct oversized pumps. The head can be reduced 10 to 50 percent by trimming or changing the pump impeller diameter within the vendor's recommended size limits for the pump casing.

The energy requirements of the overall system can be reduced by the use of a booster pump to provide the high pressure flow to a selected user and allow the remainder of the system t o operate a lower pressure and reduced power.

3.8.6    Motor and transmission

See Electrical motor driven sub-systems, Section 3.6. Note that it is important to match the right pump for the task (see Section 3.8.2) to the correct size of motor for the pumping requirements (pumping duty), see Section 3.6.2.

3.8.2    泵浦的選用

泵浦是泵輸系統的核心，首先它的選用是基於製程的需要、靜壓水頭高度及流量。同時也要考量系統結構、輸送的流體及大氣的特性等。
為了能得到一套有效率的泵輸系統，可以參見圖3.35來選用泵浦，其運轉點盡可能靠近最佳效率的那點。
圖3.36表示不同型式的泵浦在一定轉速下，各泵浦的功能以水頭高度表現時的區間範圍。
顯然有75%的泵輸系統是過大的，部分還大了20%。過大的泵浦規格是泵浦浪費能源的最大源頭。
選用過大規格的泵浦既不省錢也不節能：
●投入資本很高
●能源成本很高，因為迸出的流量超過其需要的壓力。超過的流量和壓力將之節流及調壓或由旁通閥回流，或讓不需要的泵浦運轉等是很浪費能源的。
當確認泵浦過大規格時所需做更換處置前，必須先評鑑其是否可以其他方法來降低容量，例如調整或更改轉子葉片或使用變速控制。調整轉子葉片是離心泵浦改正規格過大最省錢的方法。在供應商建議的外殼尺寸限制內調整轉子葉片直徑，其水頭高度可以降低10~50%。
利用一台增壓泵浦提供高壓流量給特定使用者，而其他系統內使用者則使用較低壓且不需要太大動力的流體，這樣可以減少整體泵輸系統需要的能源。

3.8.6    泵浦的驅動馬達和動力傳輸

請參見3.6節電動馬達驅動子系統，要注意泵浦要與工作匹配(3.8.2節)，泵輸需求要和泵浦的規格大小吻合(3.6.2節)。

None reported.

無

The applicability of particular measures, and the extent of cost savings depend upon the size and specific nature of the installation and system. Only an assessment of a system and the installation needs can determine which measures provide the correct cost-benefit. This could be done by a qualified pumping system service provider or by qualified in-house engineering staff.
The assessment conclusions will identify the measures that are applicable to a system, and will include an estimate of the savings, the cost of the measure, as well as the payback time.

一些特別的使用方法及節省的成本端視設施和系統的規模與特性而定。只有評鑑過系統及設施才能決定其正確的成本效益。此評鑑可由合格的泵輸系統服務供應商或合格的公司內部工程師來執行。
評鑑結論可用來辨明系統該使用何種方法、估計節省的成本、實施成本及回收年限等資料。

Pumping systems often have a lifespan of 15 to 20 years, so a consideration of lifetime costs against initial (purchase) costs are important.
Pumps are typically purchased as individual components, although they provide a service only when operating as part of the system, so a consideration of the system is important to enable a proper assessment of the cost-benefit.

通常泵浦系統有較長的使用年限(15~20年)，所以全使用年限的成本和初設成本間的考量是很重要的。
一般而言，泵浦都是單獨採購的，雖然在系統內可提供部分功能，但系統在評估成本效益時，泵浦的購置成本應考量在內。

Energy Efficiency (2009) 3.8.2、3.8.6