炼油化工装置水锤事故分析及处理措施

当蒸汽或可凝气体与过冷的冷凝水或冷凝液接触并冷凝时,冷凝水或冷凝液的体积仅为相同质量原蒸汽或可凝气体体积的几百分之一甚至千分之一以下,导致原气相区域变为低压区域。由于压差作用,周边的冷凝水或冷凝液将以极高的速度冲向该区域,产生瞬时压力很大的冲击,并沿管道内存有冷凝水的部位向外传播,引起水锤(水击)发生。水锤会严重影响工业生产,极易导致安全事故发生,必须引起高度重视。结合几个具体实例说明了水锤事故的危害,分析了水锤事故发生的原因并提出了改正措施。对于蒸汽和冷凝水系统,水锤产生的压力和破坏程度是管内蒸汽压力、冷凝水过冷度、形成的汽泡尺寸、汽泡内不凝气体含量的函数。一般而言,产生的压力和破坏程度随前3项的增大而增大,随后一项的增大而降低;不应将蒸汽送至含过冷冷凝水的管线中;在发生水锤事故时应首先关闭蒸汽进料阀,再打开冷凝水放凝阀。对于可凝气体和冷凝液系统,在设计或操作时应避免可凝气体快速冷凝而引起的水锤事故,特别是对塔压热旁路控制方案,应做到冷凝液和热旁路气体分别进回流罐液相和气相部分,两者互不混合。

Analysis and treatment measures of water hammer accidents occurring in refining & chemical plants

When steam or condensable vapor contact with its colder condensate or condense, the volume of condensate or condenses is less than 1/100 to 1/1 000 of the volume of original steam or condensable gas with same mass, which lead to the original gas-phase region changing to the low-pressure region. Due to the pressure difference, the surrounding condensate or condenses descend on to this phase at a very high speed, producing a large instantaneous pressure and spreading out the parts of the pipe with condensate water, causing water hammer. Water hammer seriously affects the industrial production and causes safety accidents, which should be highly emphasized. By combining with several specific examples, this study illustrates the hazards of water hammer accidents, analyzes the causes of the accidents, and puts forward the correction measures. For the system of steam and condensate, the pressure and damage induced by water hammer is a function of steam pressure, condensate subcooling degree, bubble size and quantity of noncondensable gases. In general, the induced pressure and damages increases with the increase of the first three items, and decreases with the increase of the latter item. Steam should not be sent to the pipeline containing the cold condensate. When a water hammer accident happens, the steam feed valve should be closed firstly, and then the condensate discharge valve should be opened. For the system of condensable vapor and condensate, water hammer caused by the rapidly condensation of condensable vapor should be avoided in design or operation. Especially for the tower pressure hot vapor bypass control scheme, the subcooled condensate and the hot bypass vapor should be introduced into the liquid and gas phase of the reflux drum, respectively.