max liquid level elevation 在压头计算中指什么? 回复 3# lily99 抱歉，刚才有事，没细看。 jeff 说的对，应该是指最大的液体吸上高度（超过此高度，泵就会气蚀）。 至于shut off head 是指泵出口关闭的情况下离心泵产生的最大压头。shut-off head is the maximum head generated by a centrifugal pump with zero flow and relatively less power. 提供下述一段，供参考。虽然较长但不难理解。 shut-off " head is a condition,when a centrifugal pump runs with discharge valve closed. -when a serviced pump is to be tested for its performance , we arerunning pump with different discharge condition to ensure that the pumpis capable of performing as designed. -shut-off head is the maximum head generated by a centrifugal pump with zero flow and relatively less power. because it has to overcome very small head[upto discharge valve],less frictional losses and inertia loads. -so, shut off head is a part of the charactoristic curves. #caution: dont run the centrifugal pump for a prolonged period in shut-offcondition ,or else the liquid will get vaporise and pump will run dryand damaged the important part of the pumps like mechanical seal/glandpackings,bearing ,etc. #it is a standard operating procedure "to operate a cf pump with closeddischarge valve during start-up after proper priming to minimise theheavy loading of the liquid column .as the pump gain its normalspeed,gradually open the discharge valve .like-wise , when stopping apump,close the discharge valve and then stop the pump. #at its bep(best efficiency point) the pump should be running between 80% and 85% of its shutoff head. #"head pressure" on the other hand is more complicated. "head" may be simply defined as any resistance to the flow of a pump. when pump manufacturers list the headpressure, they are referring to the vertical discharge pressure head.described in very simple terms, a pump's vertical discharge"pressure-head" is the vertical lift in height (usually measured infeet of water) at which a pump can no longer exert enough pressure tomove water. at this point, the pump may be said to have reached its"shut-off" head pressure. when you look at a flow curve chart for a pump, the "shut-off head" is the point on the graph where the curvedline becomes horizontal as the flow rate at that point is zero. thehigher a pump's head pressure, the more powerful the pump.查看更多
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