蒸汽管道水击简介

1、1第一页，共83页幻灯片2 水击的定义 造成水击的原因 水击现象的避免和处理第二页，共83页幻灯片3水击 水击又称水锤，是由于蒸汽或水突然产生冲击力，使锅筒或管道发生音响和震动的一种现象。例如，当输出的蒸汽与管道内的积水相遇时，部分热量被水迅速吸收，使少量蒸汽冷凝成水，体积突然缩小，造成局部真空，因而引起周围介质高速冲击，发生巨大音响和震动。当水击的管道被空气或蒸汽阻塞时，水不能畅通，也会发生音响和振动。第三页，共83页幻灯片4水击的冲击力可超过1000 psi.第四页，共83页幻灯片5600 psig/ 41bar - 750F/ 399CSteam can easily condense

2、where there is no flow. In this example, steam is flowing in the top line (steam header) from left to right, but the lower leg is blocked; therefore there is no flow in the lower leg.Heat is continuously lost through piping, and without the flow of steam delivering heat, the steam in the lower leg c

3、ools and condenses.第五页，共83页幻灯片6SteamHot CondensateSub-cooled Condensate620F540F580FA closer look at the condensate lying in the line reveals the contents are layered by differences in temperature. However, when the hot condensate layer is disturbed and the steam contacts the sub-cooled condensate, t

4、he steam rapidly condenses.Steam is isolated from the sub-cooled condensate by the hot condensate layer. This allows the steam to slowly condense into hot condensate which slowly cools into sub-cooled condensate.第六页，共83页幻灯片7However, doing this will almost certainly result in water hammer. Possibly s

5、evere enough to cause the line or valve to fail, resulting in personnel injury or death.第七页，共83页幻灯片8The following example shows what happens when this valve is opened to drain the condensate.Steam to User第八页，共83页幻灯片9 This rush of steam flowing above the condensate, results in a wave of condensate to

6、 form.第九页，共83页幻灯片10第十页，共83页幻灯片11第十一页，共83页幻灯片12第十二页，共83页幻灯片13This forms a pocket of steam surrounded by cooler condensate.The wave expands and forms a seal around the pipe.第十三页，共83页幻灯片14Now if we take a close look at the hot condensate layer, youll notice it has been disturbed and no longer insulates

7、 the steam from the sub-cooled condensate.Since the wave of condensate has sealed the line, the rapidly condensing steam pulls a vacuumAs discussed earlier, when steam contacts sub-cooled condensate, it rapidly condenses. Steam Header PressureVacuumThis results in an immediate flow of condensate tow

8、ard the vacuum at a very high rate (100+ mph).第十四页，共83页幻灯片15第十五页，共83页幻灯片16第十六页，共83页幻灯片17第十七页，共83页幻灯片18第十八页，共83页幻灯片19第十九页，共83页幻灯片20第二十页，共83页幻灯片21Since water does not compress, the slug of condensate in a 50 psi system can easily exceed 1000 psi at the point of impact (the valve you opened) or anywher

9、e along the shockwave.After the impact, a rebounding wave is formed, pushing condensate back in the opposite direction.第二十一页，共83页幻灯片22第二十二页，共83页幻灯片23第二十三页，共83页幻灯片24第二十四页，共83页幻灯片25第二十五页，共83页幻灯片26第二十六页，共83页幻灯片27第二十七页，共83页幻灯片28第二十八页，共83页幻灯片29第二十九页，共83页幻灯片30第三十页，共83页幻灯片31第三十一页，共83页幻灯片32第三十二页，共83页幻灯片33第三

10、十三页，共83页幻灯片34第三十四页，共83页幻灯片35第三十五页，共83页幻灯片36第三十六页，共83页幻灯片37第三十七页，共83页幻灯片38第三十八页，共83页幻灯片39第三十九页，共83页幻灯片40第四十页，共83页幻灯片41第四十一页，共83页幻灯片42第四十二页，共83页幻灯片43第四十三页，共83页幻灯片44第四十四页，共83页幻灯片45第四十五页，共83页幻灯片46First, check and see if the line has sub-cooled condensate. This is best done by using a temperature gun. If

11、 the bottom of the line is more than 40F cooler than the steam, you have sub-cooled condensate.Next, since the magnitude of condensation-induced water hammer is directly related to the difference in up-stream pressure and the vacuum created by the sub-cooled condensate, we need to reduce this differ

12、ential pressure.So how do you remove the condensate from the lower leg without water hammer?Also, with the steam isolated from the line, the vapor space left when draining the sucondensate will pull air from the atmosphere. The steam contacting sub-cooled condensate is the cause of the water hammer.

13、 With air taking the place of the steam, this driving force is eliminated.In other words, isolating the line from the steam header and depressuring it to the atmosphere will reduce the diffierential pressure to almost zero.第四十六页，共83页幻灯片47第四十七页，共83页幻灯片48第四十八页，共83页幻灯片49第四十九页，共83页幻灯片50第五十页，共83页幻灯片51第五十

14、一页，共83页幻灯片52Next, open a bleeder at the highest point of the line to depressure line.第五十二页，共83页幻灯片53第五十三页，共83页幻灯片54第五十四页，共83页幻灯片55第五十五页，共83页幻灯片56第五十六页，共83页幻灯片57第五十七页，共83页幻灯片58Now that the line is about 0 psig, if a vacuum is formed by the contact of sub-cooled condensate and steam, the strength of a

15、ny water hammer will be minimal.第五十八页，共83页幻灯片59第五十九页，共83页幻灯片60第六十页，共83页幻灯片61第六十一页，共83页幻灯片62第六十二页，共83页幻灯片63第六十三页，共83页幻灯片64第六十四页，共83页幻灯片65第六十五页，共83页幻灯片66第六十六页，共83页幻灯片67第六十七页，共83页幻灯片68第六十八页，共83页幻灯片69第六十九页，共83页幻灯片70Now that the line is drained, steam can be introduced to warm the line.第七十页，共83页幻灯片71第七十一

16、页，共83页幻灯片72第七十二页，共83页幻灯片73第七十三页，共83页幻灯片74Once the line is has been heated for the designated time, the line can be placed back in service.第七十四页，共83页幻灯片75第七十五页，共83页幻灯片76第七十六页，共83页幻灯片77第七十七页，共83页幻灯片78第七十八页，共83页幻灯片79第七十九页，共83页幻灯片80第八十页，共83页幻灯片81蒸汽管道内水击的原因：蒸汽管道内水击的原因：在送汽前未进行疏水在送汽前未进行疏水和暖管和暖管。送汽时主汽阀开启过快或过大。送汽时主汽阀开启过快或过大。锅炉负荷增加过急或发生满水、汽水共腾等事故