| 摘要 |
PURPOSE:To reduce power necessary for management operation of a pump and to prevent biting of foreign matter by feeding compressed air into the interior of vertical pump under management operation and mixing foam air into water in pump even under shutt-off operation. CONSTITUTION:At first, the delivery valve (not shown) located in the downstream of a column pipe 5 is fully closed. Then compressed air is fed from a compressed air source 12 through a pressure feed pipe 11 into the interior of vertical pump 2 to lower the water level in the vertical pump 2 until the lower portion of an impeller 8 is submerged. Upon rotation of the impeller 8 under this state, water and air are agitated to produce two phase flow of gas and liquid where foam air is mixed in water. Consequently, apparent density of fluid in the vertical pump 2 will lower to reduce driving force even when shut-off operation is continued while biting of foreign matter between the impeller 8 and casing 6 is prevented through lubrication of water.
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