超大型蜗壳式离心泵站启停过程水锤防护研究

Research on water hammer protection in start-stop transition process for ultra-large water supply pump station

超大型蜗壳式离心泵站与常规离心泵站相比,其设备和管道规模有很大不同,如出水流道常布置虹吸管及真空破坏阀以满足快速断流,其水锤防护措施需要特别关注。以国外某供水泵站为例,研究水泵依次启动和停机时的水锤现象,分析其水力过渡过程的特点,提出超大型蜗壳式离心泵站的安全启停操作流程。首先,泵站机组一般逐台依次启动,并采用满管启动方式以防启动水锤,启动成功后应尽快打开蝶阀以避免泵后超压;其次,多台机组正常停机或事故停机时,均需采用两阶段关阀保护,但不宜同时启用真空破坏阀联合防护,保持驼峰一定负压反而会降低倒转转速,且流道不会发生水柱分离;最危险工况是机组同时停泵且只有一台蝶阀拒动的情况,此时只能启用真空破坏阀快速断流,以防该机组在停泵压力驱动下飞逸转速超过上限。

Compared with the conventional pump station,the watehammer phenomenon of ultra-large centrifugal pump station is different.For example,siphon and vacuum breaker are often set in the outlet channel to cut off flow.Therefore,its water hammer protection needs special attention.Taking a foreign water supply pump station as an example,this paper studies the water hammer phenomenon when the pumps start in turn and stop.Based on the analysis of characteristics of transition process,the safe start-stop process is proposed.First of all,the pumps are generally started one by one,and full pipe start mode is adopted to prevent water hammer.The butterfly valve should be opened as soon as possible to avoid overpressure behind the pump.Secondly,two-stage valve closing protection should be adopted for shutdown of pumps,but it is not appropriate to use vacuum breaker simultaneously.Keeping negative pressure in siphon is benefit to reduce runway speed of the pump,and the water column separation will not occur.The most dangerous condition is that all the pumps shutdown simultaneously and only one of the valves refuses to operate unexpectedly.At this time,vacuum breaker should be used to prevent the runway speed of the pump exceeding the limit.