蒸汽管道水擊簡介

1、1第一頁，共83頁幻燈片2 水擊的定義 造成水擊的原因 水擊現(xiàn)象的避免和處理第二頁，共83頁幻燈片3水擊 水擊又稱水錘，是由于蒸汽或水突然產(chǎn)生沖擊力，使鍋筒或管道發(fā)生音響和震動的一種現(xiàn)象。例如，當(dāng)輸出的蒸汽與管道內(nèi)的積水相遇時，部分熱量被水迅速吸收，使少量蒸汽冷凝成水，體積突然縮小，造成局部真空，因而引起周圍介質(zhì)高速沖擊，發(fā)生巨大音響和震動。當(dāng)水擊的管道被空氣或蒸汽阻塞時，水不能暢通，也會發(fā)生音響和振動。第三頁，共83頁幻燈片4水擊的沖擊力可超過1000 psi.第四頁，共83頁幻燈片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.第五頁，共83頁幻燈片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.第六頁，共83頁幻燈片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.第七頁，共83頁幻燈片8The following example shows what happens when this valve is opened to drain the condensate.Steam to User第八頁，共83頁幻燈片9 This rush of steam flowing above the condensate, results in a wave of condensate to

6、 form.第九頁，共83頁幻燈片10第十頁，共83頁幻燈片11第十一頁，共83頁幻燈片12第十二頁，共83頁幻燈片13This forms a pocket of steam surrounded by cooler condensate.The wave expands and forms a seal around the pipe.第十三頁，共83頁幻燈片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).第十四頁，共83頁幻燈片15第十五頁，共83頁幻燈片16第十六頁，共83頁幻燈片17第十七頁，共83頁幻燈片18第十八頁，共83頁幻燈片19第十九頁，共83頁幻燈片20第二十頁，共83頁幻燈片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.第二十一頁，共83頁幻燈片22第二十二頁，共83頁幻燈片23第二十三頁，共83頁幻燈片24第二十四頁，共83頁幻燈片25第二十五頁，共83頁幻燈片26第二十六頁，共83頁幻燈片27第二十七頁，共83頁幻燈片28第二十八頁，共83頁幻燈片29第二十九頁，共83頁幻燈片30第三十頁，共83頁幻燈片31第三十一頁，共83頁幻燈片32第三十二頁，共83頁幻燈片33第三

10、十三頁，共83頁幻燈片34第三十四頁，共83頁幻燈片35第三十五頁，共83頁幻燈片36第三十六頁，共83頁幻燈片37第三十七頁，共83頁幻燈片38第三十八頁，共83頁幻燈片39第三十九頁，共83頁幻燈片40第四十頁，共83頁幻燈片41第四十一頁，共83頁幻燈片42第四十二頁，共83頁幻燈片43第四十三頁，共83頁幻燈片44第四十四頁，共83頁幻燈片45第四十五頁，共83頁幻燈片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.第四十六頁，共83頁幻燈片47第四十七頁，共83頁幻燈片48第四十八頁，共83頁幻燈片49第四十九頁，共83頁幻燈片50第五十頁，共83頁幻燈片51第五十

14、一頁，共83頁幻燈片52Next, open a bleeder at the highest point of the line to depressure line.第五十二頁，共83頁幻燈片53第五十三頁，共83頁幻燈片54第五十四頁，共83頁幻燈片55第五十五頁，共83頁幻燈片56第五十六頁，共83頁幻燈片57第五十七頁，共83頁幻燈片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.第五十八頁，共83頁幻燈片59第五十九頁，共83頁幻燈片60第六十頁，共83頁幻燈片61第六十一頁，共83頁幻燈片62第六十二頁，共83頁幻燈片63第六十三頁，共83頁幻燈片64第六十四頁，共83頁幻燈片65第六十五頁，共83頁幻燈片66第六十六頁，共83頁幻燈片67第六十七頁，共83頁幻燈片68第六十八頁，共83頁幻燈片69第六十九頁，共83頁幻燈片70Now that the line is drained, steam can be introduced to warm the line.第七十頁，共83頁幻燈片71第七十一

16、頁，共83頁幻燈片72第七十二頁，共83頁幻燈片73第七十三頁，共83頁幻燈片74Once the line is has been heated for the designated time, the line can be placed back in service.第七十四頁，共83頁幻燈片75第七十五頁，共83頁幻燈片76第七十六頁，共83頁幻燈片77第七十七頁，共83頁幻燈片78第七十八頁，共83頁幻燈片79第七十九頁，共83頁幻燈片80第八十頁，共83頁幻燈片81蒸汽管道內(nèi)水擊的原因：蒸汽管道內(nèi)水擊的原因：在送汽前未進行疏水在送汽前未進行疏水和暖管和暖管。送汽時主汽閥開啟過快或過大。送汽時主汽閥開啟過快或過大。鍋爐負荷增加過急或發(fā)生滿水、汽水共騰等事故