2012 Volume 18 Issue 1 Pages 35-43
An traditional pipeline system for water pumping and conveyance has designed to include a flywheel and other facilities for suppressing negative pressure to a depth of 7 m or below in order to prevent water column separation. If the occurrence point of water column separation and the influence of the separation on the pipeline can be accurately identified, an optimal design can be adopted for each pipeline, which permits water column separation to occur without inflicting damage. Field experiments were conducted for evaluating water column separation during a pump power failure and the resulting water hammer pressure caused by recombination of the columns. The effect of implementing a general-purpose check valve or the non-water hammer pressure check valve was investigated. When restarting a pump after a sudden stop, it was found that a pressure rise can be suppressed by opening the bypass valve of the non-water hammer check valve. In addition, it was found that using an independent air choke valve to draw in air during times of negative pressure prevented the spread of the negative-pressure region and thus suppressed water column separation. The field experiments revealed that safety of pipeline is ensured by preventing recombination of the separated water columns, at the regions where water column separation is generated by the negative pressure.
