1. ISO 13709 section 8.3.3.6 testing can cause problems in older pump designs; 2. Modern designs with the following are preferred: 5 or 7 vane impellers with 180° volutes; 6 vane impellers with 168° volutes; Impeller eye diameter minimized in relation the target Nss value. 3. Avoid large impeller trims as these promote recirculation and give a false indication of the true BEP (shockless) flow; 4. Slotted bull rings offer a superior balance of recirculation suppression vs. NPSHr increase compared to plain rings.
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机译：1. ISO 13709第8.3.3.6节试验可能导致旧泵设计中的问题; 2.具有以下设计的现代设计是优选的：5或7个叶片叶轮，180°蜗壳; 6个叶片叶轮，蜗壳168°; 叶轮眼直径最小化目标NSS值。 3.避免大型叶轮装饰，因为这些促进再循环，并给出真正的BEP（无震）流动的错误指示; 4.与普通环相比，开槽的公牛戒指提供了卓越的再循环抑制与NPSHR增加的平衡。
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