如何正确选泵

译文：
1、根据装置的布置、地形条件、水位条件、运转条件、经济方案比较等多方面因素 2、考虑选择卧式、立式和其它型式（管道式、直角式、变角式、转角式、平行式、垂直式、直立式、潜水式、便拆式、液下式、无堵塞式、自吸式、齿轮式、充油式、充水温式）。卧式泵拆卸装配方便，3、 易管理、但体积大，4、 价格较贵，5、 需很大占地面积；立式泵，6、 很多情况下叶轮淹没在水中，7、 任何时候可以启动，8、 便于自动盍或远程控制，9、 并且紧凑，10、 安装面积小，11、 价格较便宜。 3、根据液体介质性质，确定清水泵，热水泵还油泵、化工泵或耐腐蚀泵或杂质泵，或者采用不堵塞泵。 安装在爆炸区域的泵，应根据爆炸区域等级，采用防爆电动机。 4、振动量分为：气动、电动（电动分为220v电压和380v电压）。 5、根据流量大小，选单吸泵还是双吸泵：根据扬程高低，选单吸泵还是多吸泵，高转速泵还是低转速泵（空调泵）、多级泵效率比单级泵低，当选单级泵和多级泵同样都能用时，宜选用单级泵。 6、确定泵的具体型号，采用什么系列的泵选用后，就可按最大流量，放大5%——10%余量后的扬程这两个性能主要参数，在型谱图或系列特性曲线上确定具体型号。 利用泵特性曲线，在横坐标上找到所需流量值，在纵坐标上找到所需扬程值，从两值分别向上和向右引垂线或水平线，两线交点正好落在特性曲线上，则该泵就是要选的泵，但是这种理想情况一般不会很少，通常会碰上下列几种情况： A、第一种：交点在特性曲线上方，这说明流量满足要求，但扬程不够，此时，若扬程相差不多，或相差5%左右，仍可选用，若扬程相差很多，则选扬程较大的泵。或设法减小管路阻力损失。 B、第二种：交点在特性曲线下方，在泵特性曲线扇状梯形范围内 ，就初步定下此型号，然后根据扬程相差多少，来决定是否切割叶轮直径，若扬程相差很小，就不切割，若扬程相差很大，就按所需Q、H、，根据其ns和切割公式，切割叶轮直径，若交点不落在扇状梯形范围内，应选扬程较小的泵。 选泵时，有时须考虑生产工艺要求，选用不同形状Q-H特性曲线。 A、 如：要将液位输送到必须维持一定液面高度的容器中去， B、 此时变稀 C、 望量有较大的变化，而 D、 扬程变化很小， E、 为次应选用平坦H-O曲线的泵。 F、 有如：把石油送到管式加热炉中去， G、 若工作中流量变化小， H、 则炉管中易产生结焦现象。要避免这种情况， I、希望但流量略有减小时， J、 管中油的压力有较大增加， K、 使刚要形成的焦疤被较高液流压力冲刷掉， L、 这时，宜选用Q-H曲线较为徒降的油泵。 7、泵型号确定后，对水泵或输送介质的物理化学介质近似水的泵，需再到有关产品目录或样本上，根据该型号性能表或性能曲线进行校改，看正常工作点是否落在该泵优先工作区？有效NPSH是否大于（NPSH）。也可反过来以NPSH校改几何安装高度？ 8、 对于输送粘度大于20mm2/s的液体泵，一定要把以水实验泵特性曲线换算成该粘度的性能曲线，特别要对吸如性能进行认真计算或较核。 9、 确定泵的台数和备用率： 对正常运转的泵，一般只用一台，因为一台大泵与并联工作的两台小泵相当，（指扬程、流量相同），大泵效率高于小泵，故从节能角度讲宁可选一台大泵，而不用两台小泵，但遇有下列情况时，可考虑两台泵并联合作： 流量很大，一台泵达不到此流量。 对于需要有50%的备用率大型泵，可改两台较小的泵工作，两台备用（共三抬） 对某些大型泵，可选用70%流量要求的泵并联操作，不用备用泵，在一台泵检修时，另一抬泵仍然承担生产上70%的输送。 对需24小时连续不停运转的泵，应备用三台泵，运转，一台备用，一台维修。

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原文：
1, according to device layout, terrain conditions, water conditions, operating conditions, economic programs, and other factors more 2, consider selecting horizontal, vertical, and other type (pipe type, rectangular type, angle-type, angle-type, parallel type, vertical type, vertical, submersible, they demolished type, liquid type, non-plug type, self-priming, gear type, oil-filled type, filling water temperature type). Horizontal pump assembly disassembly easy, 3, easy management, but bulky, 4, higher prices, 5, be a greatStainless teel diaphragm pump area; vertical pumps, 6, in many cases impeller submerged in water, 7, at any time can be Start, 8, to facilitate the automatic or remote control of mood, 9, and the compact, 10, installation of small size, 11, the price is cheaper. 3, according to the nature of the liquid medium to determine the clean water pump, heat pump also pumps, chemical pump, or corrosion resistant pumps or impurities pump, or using non-clogging pumps. Pump installed in the blast area should be based on an explosion regional levels, using explosion-proof motor. 4, vibration is divided into: pneumatic, electric (electrical voltage into 220v and 380v voltage). 5, according to flow size, menu, or double-suction pump suction pump: According to the head height, menus or multi-suction pump suction pumps, high-speed pump or a low-speed pump (air conditioning pumps), multi-stage pump more efficient than single-stage pump is low, elected to a single pump and multi-stage pump also can be used, it is desirable selection of a single-stage pump. 6, determine the specific pump model, adopted after the series of pump selection, you can press the greatest flow, zoom 5% - 10% margin of the head after the performance of these two main parameters in the model spectrum or a series of characteristic curves of the determine the specific type. The use of pump characteristic curve, the horizontal axis to find the required flow value, find Engineering Plastic diaphragm pumpthe lift on the vertical axis value, from the two values were cited upward and vertical or horizontal line to the right, the intersection of two lines fall exactly on the curve, then the The pump is to select the pump, but this ideal situation will normally be small, often run into the following situations: A, the first: the top of the intersection of the characteristic curve, indicating flow to meet the requirements, but the head is not enough time, if the head very similar, or a difference of about 5% can still choose, if the head is far too small, then select a larger head pump. Or trying to reduce the pipeline pressure drop. B, second: below the intersection in the characteristic curve, the pump characteristic curve within the fan-shaped ladder on the initial set of this model, and then lift the difference to decide whether to cut impeller diameter, if the head difference is small, not cutting , if the head a big difference on the desired Q, H,, according to its ns and cutting formulas, cutting impeller diameter, if the intersection does not fall within the fan-shaped trapezoid, to be elected head of smaller pumps. Pump selection, and sometimes need to consider the production process requirements, selection of different shapes QH characteristic curve. A, such as: to maintain a certain level to be transmitted to the liquid height of the container to go, B, time-thinning C, Wang greater amount of change, while D, head very few changes, E, for the meeting should use a flat H-O curve of the pump. F, like: the oil sent to the tube furnace in go G, if the flow of work, little change H, then the furnace tube coking phenomenon is easy to produce. To avoid this situation, I, want to, but slightly reduced flow rate when J, tube pressure of oil in a larger increase in K, so that the formation of coke was about to a higher flow pressure scar was washed away, L, then, should choose a more believers QH curve down to the pump. 7, pump model is established on the pump or the transmission medium of physical and chemical media, similar to the water pump is required and then to the product catalog or samples on the basis of the performance table, or the performance of the model curve Xiaogai to see whether it fell in the normal operating point Pump priority area? Effective NPSH is greater than (NPSH). NPSH Xiaogai can also turn to the geometric mounting height? 8, for conveying the viscosity is greater than 20mm2 / s of liquid pumps, must take the test pump water characteristic curve to convert the viscosity of the performance curve, in particular, the performance of the smoke as they carefully calculated or more nuclear. 9, determine the number of pump station and standby rate: On the normal functioning of the pump, generally only one, as a parallel work of the National Taiwan University, pumps and two small pumps rather, (refer to head, flow the same), large pumps more efficient than the small pump, it is optional from the energy AL alloy diaphragm pumppoint of view, rather a National Taiwan University, pumps, instead of two small pumps, but the case of the following conditions may be considered co-operation of two pumps in parallel: A great flow, a pump not reach the traffic. For the required reserve rate of 50% of large pumps, the pump can change the work of two smaller, two spare (a total of three lift) For some large-scale pumps, the choice of 70% of the pump flow requirements of parallel operation, do not spare pump, pump repair in a single, another lift pump remains committed to the production of 70% of the transmission. Required 24 hours of continuous non-stop operation of the pump, should be back three pumps running, a spare, a maintenance.