Specialized in manufacturing compensators, expansion joints, baffle doors

选金属膨胀节，最怕什么？怕客户电话里只说一句“给我报个DN600的价”。报完价就问“为什么这么贵”。因为选型参数不全，厂家只能按最保守、最大规格来报价，这价钱能不高吗？

那怎么办？想买到合适的膨胀节，先别急着报口径，把下面5件事搞清楚。

别急着报口径，先算清楚管线要吸收多大位移

膨胀节的核心功能就是吸收位移。位移量没算明白，后头全是白搭。

管线的热膨胀量，一般按管材线膨胀系数乘以温度差再乘以管线长度来算。碳钢的线膨胀系数大约是0.012mm/m·°C，不锈钢稍高一点。举个例子：一条30米长的碳钢管线，介质温度从20°C升到200°C，轴向热膨胀量就是30×180×0.012＝64.8mm。

这还没完，安装时的环境温度、设备振动、管道基础沉降产生的位移也得算进去。你要是只知道管径，不知道怎么算，就找厂家要一张《管道热位移速查表》，对着查就行。但前提是，你得把管线走向图准备好，固定支架和滑动支架的位置标清楚。

介质、压力、温度：决定波纹管材质和层数的三件套

这三个参数放在一起看，波纹管的材料、壁厚和层数就基本定了。

介质这头，普通蒸汽、热水、压缩空气，用304不锈钢就够了；含氯离子的介质，得用316L；脱硫烟气这种强腐蚀工况，往往得选耐蚀合金或者干脆上非金属膨胀节。介质成分一定要写全，别只说一个“烟气”，烟气里的SO₂、NOₓ、粉尘含量不一样，腐蚀性差好几倍。

压力高，壁厚就得加；温度高，材料许用应力下降，补偿量也受影响。比如压力1.6MPa、温度350°C的蒸汽管道，通常得用2~3层波纹管；同样是这个温度但压力降到0.1MPa，单层就够了。层数越多，刚度越大，价格也越高，没必要盲目追求多层。

另外说一句，导流筒这东西别漏了。气体介质流速高，不加导流筒，波纹管容易被冲蚀。介质含颗粒物的话，导流筒前端的防磨结构也要考虑。

轴向、横向还是角位移？选通用型还是铰链型

位移方向没搞清，选出来的结构肯定不对路。

管线主要沿管线方向伸缩，就是轴向位移，选通用型波纹膨胀节，也叫轴向型膨胀节。要是管线走了个L型或Z型弯，水平方向和垂直方向都有位移，这时候单个轴向型就搞不定了，得考虑复式铰链横向型膨胀节，或者两个铰链型膨胀节配合着用。

角位移常见于设备连接处，比如汽轮机排汽口、风机进出口。这种工况下铰链型膨胀节或复式拉杆型是不错的选择。

怎么判断？说白了就一句话：顺着管子方向伸缩选通用型；管子拐弯了、接头处有偏转，就得用带铰链或者复式结构的。别指望着用一个通用型把啥位移都吃了，那叫硬扛，不叫补偿。

拉杆、铰链还是压力平衡？约束结构关系支架受力

膨胀节的作用不光是“能伸缩”，还得“受力可控”。

波纹管在压力作用下会产生一个巨大的推力，这个推力如果全甩给固定支架，支架得做得多粗壮？所以膨胀节内部要有约束结构来分担——这就是拉杆、铰链、压力平衡这些结构存在的意义。

通用型膨胀节不自带约束，内压推力得靠主固定支架扛。管线走向复杂、支架不好做的地方，用直管压力平衡型膨胀节或曲管压力平衡型膨胀节，它们能把内压推力抵消掉，作用在支架上的力就小得多。水泥厂和电站的管道上经常用这种。

有人认为选带拉杆的膨胀节就能替代固定支架。不是的。拉杆约束的是膨胀节自身的位移，不是把管道的推力全消了。支架该做的还得做，只是受力大小不一样。

高温烟气、大口径、真空管道：特殊工况怎么加料

工况一特殊，标准产品往往就顶不住了，得“加料”。

高温烟气，温度到600°C以上，金属波纹管基本没法用——材料蠕变和氧化腐蚀会迅速缩短寿命。这时候选非金属膨胀节（织物纤维膨胀节）更合适，耐温高、柔性好，还有一定的吸音隔振效果。脱硫烟道里也经常用非金属膨胀节，配合烟气挡板门一起用。

大口径管道，比如DN3000以上的烟道或风道，金属波纹管制造成本高，重量也大，施工吊装都费劲。这种工况下矩形非金属膨胀节是更常见的方案。当然，如果客户指定要金属的，那就得用大口径厚壁膨胀节，加强环和边板都得加厚。

真空管道又不一样了。真空工况下波纹管要承受外压，抗失稳能力是关键。空冷岛真空管道上经常用到双铰链膨胀节，结构上多一道约束，稳定性好。真空专用软管在波纹管外面加装金属网套，也是这个道理。

给厂家一张选型参数表，比来回打电话高效得多

跟厂家沟通的时候，把下面这些信息一次性给全：

• 管道通径DN、连接方式（法兰还是焊接）
• 位移类型和数值：轴向、横向、角位移各是多少mm/度
• 介质名称和成分，尤其是有腐蚀性成分的
• 设计压力MPa、设计温度°C、操作温度°C
• 安装位置示意（直管段、弯头附近、设备接口）
• 固定支架和滑动支架的布置情况
• 有没有保温层、有没有外护套要求

这些信息给全了，厂家半小时就能把方案和报价做出来。省下来的时间，比来回打电话催问效率高多了。

金属膨胀节这东西，没有“万能型号”，只有“适不适合”。选型参数清晰、工况边界明确，厂家才能给你配出靠谱的方案。如果拿不准，就直接把参数表发给厂家——方案成不成立，让工程师给你判断。

金属膨胀节怎么焊接？这个问题看着简单，实际上坑特别多。前两天碰到个客户，拿回去的膨胀节装上去没俩月，焊缝根部就渗漏了。拆开一看，典型的组对错边量超标+热输入过大，把薄壁波纹管烧穿了。

干这行的人都清楚，金属膨胀节焊接和普通管道焊接完全两码事。波纹管壁薄、刚度低、对热敏感，稍不注意就是焊缝裂纹或者烧穿。今天咱们就按实际干活的经验，把这5个关键点说透。

1. 焊接前先看材质：焊材选错直接废件

别拿到管子就开焊。先搞清楚材料是304、316L、Inconel还是碳钢。这几类材质的焊接工艺相差十万八千里。

咱们站里的通用型波纹膨胀节，波纹管大多用304或316L不锈钢，这类奥氏体不锈钢好焊，但要注意控制层间温度，不超过150℃最好。高温轴向型膨胀节有的用Inconel合金，比如Inconel 625或800H，这种材料必须用镍基焊丝，像ERNiCrMo-3，而且要严格控制热输入，不然高温下焊缝的耐腐蚀性能直接报废。碳钢相对皮实，但预热和焊后保温不能省。

选焊材之前，对照产品资料查清楚波纹管和接管的材质。产品用什么料，焊材就跟着匹配，别凭经验瞎猜。

2. 坡口与组对：薄壁件最怕错边量

膨胀节端口和接管组对时，坡口角度、钝边、间隙这三样必须按工艺卡来。波纹管壁薄，通常只有0.5mm~3mm，坡口开大了直接熔穿，开小了根部又熔不透。

实际干活时，很多人栽在错边量上。规范要求错边量控制在壁厚的10%以内。啥意思？比如壁厚2mm，错边量就不能超过0.2mm。超过这个数，焊缝根部容易出现未熔合，表面看着像焊上了，其实内部有分层，一打压就漏。

组对的时候用专用夹具，不要拿手扶着点焊固定。波纹管本身不能承受集中载荷，组对时要是硬掰，波纹变形就废了。

3. 焊接方法怎么选：氩弧焊打底是标配

薄壁波纹管全氩弧焊，这是铁律。氩弧焊热输入可控，电弧稳定，能保证背面成型。大口径厚壁膨胀节这类厚壁件，可以氩弧打底+手工电弧焊填充，效率高，但打底那层必须氩弧焊。

注意，填充和盖面焊接时，电弧不要直接对着波纹管，尽量靠近接管侧，这样能减少高温对波纹管的损伤。焊接电流要按材质和厚度调整。304不锈钢，1mm左右的波纹管，电流控制在50~70A。Inconel材料就要低一些，还得用背面保护气体。

焊接方法没有千篇一律的套路，但有一条原则：热输入越小越好，速度越快越好，焊丝越细越好。

4. 焊接顺序和变形控制：先纵缝后环缝

波纹管最怕什么？焊接飞溅和电弧划伤。飞溅落在波纹上，就是个腐蚀起点。所以焊接前，波纹管表面一定要用保护布或者白铁皮挡住。

焊接顺序上，先焊纵缝，再焊环缝。纵缝是波纹管本身的焊缝，有图纸要求的必须氩弧焊，焊完要修磨平整。环缝焊接时，对称施焊或者分段退焊，这样做是为了减少局部热量堆积。分段退焊，每段200~300mm，焊完一段冷下来再焊下一段。

现场焊接时，膨胀节内部要通保护气体。有人说省钱不通，结果背面成型一塌糊涂，氧化皮一片一片掉。记住，背面成型不好，焊缝寿命直接打对折。不锈钢波纹管背面用氩气保护，纯度不低于99.99%。

5. 焊后检查与试压：别省那一步

焊缝外观检查只是第一步。咬边、表面气孔、弧坑裂纹，这些肉眼能看见的肯定不合格。但更关键的是内部缺陷，必须按标准做无损检测。

电站行业用波纹膨胀节、压力管道用的膨胀节，焊缝一般要求100% RT或UT。RT就是拍片子，UT是超声。有条件的用相控阵，效率更高。咱们站里焊完的膨胀节，只要客户要求，提供完整报告。

试压也是同样的道理。金属膨胀节试压要带约束装置，防止波纹管过度伸长。试压时先低后高，逐步升压。压力表要校验过的，量程要是试验压力的1.5~2倍。水压试验时，要排净内部空气，不然压力不稳。

金属膨胀节怎么焊接？其实核心就一句话：把波纹管当成精密件对待，每个参数都较真。焊接这活没有捷径，但按照上面这5步走，废品率能降一大半。别嫌麻烦，返工的成本比焊接时的细致功夫高得多。

前两天碰到个做热网设计的工程师，拿着图纸问我：“膨胀节角位移的单位是什么？怎么图纸上有的写°有的写mm？”我一看，他那个膨胀节选型样本上，角位移一栏标注的是“±5°”，另一家给的却是“±12mm”。要是把这俩直接对比，非得出事不可。今天就把这个参数掰开揉碎讲清楚。

角位移到底是什么？先分清它与横向位移、轴向位移的差别

膨胀节在管道里干的活，说白了就是吸收位移。位移分三种：轴向位移是沿着管道轴线方向的伸缩，横向位移是垂直于轴线的错动，而角位移——是膨胀节两端法兰之间发生的相对转动。你可以把它想象成管道“折了一下腰”，这个折角的大小，就是角位移。

理解这个很关键。很多人把角位移和横向位移混为一谈，其实两码事。横向位移是平移，角位移是旋转。比如一台设备因为热膨胀向上抬了20mm，连接它的管道如果拐个弯，那膨胀节实际承受的可能是好几度的角位移，而不是简单的20mm横向位移。你光给厂家报一个“横向位移20mm”，人家真没法给你选型。

角位移的单位只有度（°）吗？为什么有些图纸上写的是毫米？

标准的角位移单位就是度（°），这个没什么好争的。但为什么有些图纸上写毫米？因为很多厂家样本里，角位移是用“等效横向位移”来表示的。啥意思？就是把这个角位移换算成波纹管某一端的弧线位移量。

弧长等于半径乘以弧度。如果波纹管的回转半径是500mm，角位移是2°，那对应的弧长就是500×2×π/180≈17.5mm。但这里有个大坑：不同的膨胀节结构，回转半径根本不一样。同样是2°角位移，在单式铰链膨胀节上和一个大尺寸复式铰链横向型膨胀节上，换算出来的毫米数可能差好几倍。

所以看到图纸上写mm，先别急着换算。你要搞清楚这个mm到底是从哪来的，是厂家按自身产品结构算出来的等效横向位移，还是指波纹管某一点的摆动弧长。要是拿这个mm直接当角位移去选型，那就等着现场装不上吧。

从波纹管结构看角位移的产生：单式铰链与复式铰链为何不同

角位移不是平白无故产生的，它得靠铰链结构来引导。单式铰链型膨胀节，就是波纹管两端各装一个铰链，只能在一个平面内转动，吸收角位移的能力很有限。而复式铰链横向型膨胀节，有两组铰链，中间还有一段接管，波纹管可以发生更复杂的变形，能吸收较大的角位移和横向位移。

再比如空冷岛真空管道上用的双铰链膨胀节，那结构就更讲究了，两个铰链配合波纹管，专门对付大面积水平管道的热膨胀。你看，同样是角位移，单铰链和双铰链能吸收的量级完全不一样。所以选型时别只看一个“角位移2°”就完事，还得确认是什么结构。你给厂家提个角位移4°，人家复式铰链轻松搞定，但你拿单式铰链去扛，波纹管迟早失稳。

角位移数值怎么读？工程选型中常见单位误区与换算陷阱

拿到一份膨胀节参数表，角位移一栏写着“±6°”，你直接读成“正负6度”就对了。但有些设计院出的管道布置图，会把角位移标注成“6mm/m”，这就容易懵了。6mm/m其实是斜率，换算成角度就是arctan(0.006)≈0.34°。可别把它当成单纯的6mm位移。

把样本上的角位移单位“°”看成弧度。谁要是把5°当成5 rad，那选出来的膨胀节能扭成麻花。记住，工程上角位移默认单位就是度，不是弧度，也不是毫米。

那怎么核对厂家给的吨位对不对？告诉你个土办法：你先算出管道所需的总角位移，然后看厂家样本上每个波纹管的允许角位移，再乘上铰链的组数。如果是单式铰链，一个波纹管扛一个角位移；如果是复式铰链，每组铰链分担一部分。别指望一个波纹管能吃下所有角度。

选型实战：角位移与拉杆、铰链结构的配合关系，以及如何向厂家提资

拉杆和铰链是膨胀节的“安全带”。拉杆负责承受内压推力，防止波纹管被压力顶开；铰链负责约束位移方向，让角位移老老实实沿着设计好的平面走。没有拉杆和铰链，光一个波纹管，根本没法单独吸收角位移。

所以选型提资的时候，你需要给厂家提供这几样东西：管道通径、设计压力、设计温度、介质，还有角位移的大小和方向。角位移一定要写清楚是“度”，并说明是哪个平面内的转动，最好附一张简图。别只甩一句“需要吸收角位移”，厂家不是神仙，猜不出你的管线走向。

通用型波纹膨胀节本身不吸收角位移，它只能靠波纹管自身的柔性硬扛，扛多了寿命骤降。真要吸收角位移，选复式铰链横向型膨胀节或专用的铰链型膨胀节。你想省那点钱，将来波纹管开裂换管，麻烦更大。

膨胀节角位移的单位是什么？标准答案就一个字：度。但搞懂它背后的结构逻辑、换算陷阱以及和铰链拉杆的配合关系，选型才不至于翻车。下次再看到样本上写mm，多问一句“怎么换算的”，比闷头选型靠谱得多。

Are expansion joints metal or not? Don't answer in a hurry

Is the expansion joint metal? Don't rush to answer "yes", and don't insist on "no". Everyone who has worked on pipelines knows that the expansion joint is not a single material at all. It is a family with various members, including all-metal, pure non-metal, and rubber and PTFE. You only ask "Is it metal?" It's like asking "Is the car burning oil?" The hybrid car shook its head when it heard it.

Expansion joints are both metallic and non-metallic. Metal expansion joints are the mainstream, but non-metallic expansion joints are better in some working conditions. If you only look at the material to draw a conclusion, nine times out of ten, you will step on a pit.

From bellows to non-metallic expansion joints, what is the difference in materials

The core of metal expansion joint is corrugated pipe, which is generally stamped with stainless steel and alloy steel, and absorbs the thermal displacement of pipe by elastic deformation of metal. The general corrugated expansion joint, high-temperature axial expansion joint and corrugated expansion joint for power station industry of this station are all representatives of this road. The bellows can be made into single layer or multi-layer, and the guide tube and tie rod can be added. The more complicated the structure, the stronger the compensation ability.

What about non-metallic expansion joints? Take rectangular non-metallic expansion joints and non-metallic expansion joints (fabric fiber expansion joints) for example. The main body is several layers of fiber fabric, with thermal insulation cotton sandwiched in the middle, and both ends are fixed with metal flange frames. Rubber compensator and PTFE compensator are more direct, even the bellows are not used, all depending on the flexibility of rubber or PTFE material.

As soon as the materials are changed, the performance logic completely changes. Metals rely on ductility to carry displacement, while non-metals rely on fabric deformation and internal structure sliding. Metals can carry hundreds or thousands of degrees of high temperature, but non-metals can't carry that high temperature, but they have good thermal insulation performance, are not afraid of acid-alkali corrosion, and even have a much longer life than metals in some media.

Metal expansion joint and non-metallic expansion joint, what problems do they solve

High temperature, high pressure and large displacement compensation. Steam pipeline, power station boiler air supply system, cement kiln head and tail, the temperature in these places is always five or six hundred degrees Celsius, and the pressure is not low. Only metal bellows can withstand it. For example, the metal corrugated expansion joint in the cement industry is specially designed for this working condition. There are also directly buried (fully buried) expansion joints, which have to bear external pressure and groundwater when buried in the soil, and non-metals can't do this job at all.

What about non-metallic expansion joints? It does not take the high-temperature and high-pressure route, and its home field is large-size, low-pressure, vibration isolation and noise silencing occasions. For example, the desulfurization flue has a cross-section of several meters wide. Do you try it with a metal bellows? Costs are frighteningly high and processing is difficult. At this time, the rectangular non-metallic expansion joint came on the field, which was easily done. Another example is the fan inlet and outlet. The rubber compensator can absorb vibration and reduce noise. PTFE compensator is the nemesis of strong corrosive media. The metal is directly wasted when it meets hydrochloric acid and concentrated sulfuric acid, but PTFE is unscathed.

See? No one is superior to anyone, only whether it is suitable or not. You take the metal expansion joint to catch the corrosive acid, and it will be perforated in three months; Take the non-metallic one to carry the high-temperature steam and burn it through directly. Wrong choice, no one can hold up.

Don't just look at the material when selecting the model. These working conditions are more critical

There is a big circle in front. In fact, the core is one sentence: don't worry about "whether the expansion joint is metal or not", first find out your own working conditions. What is the medium? How hot is the temperature? How stressful? Is the displacement axial, lateral or angular? How wide is the pipe size? Is there enough installation space for tie rods? These are the hard indicators that determine the selection.

Take an example. The same thermal pipeline, with a temperature of 200℃ and a pressure of 1.6MPa, has no problem choosing a metal expansion joint; However, if the medium is sulfur-containing flue gas, the temperature is not high, but it is easy to crystallize and block, then non-metallic expansion joint is more suitable. For example, when the installation space is limited, the rotary compensator and the lateral expansion of the double hinge save energy and a lot of space, but they are all metal. Do you want to use non-metal instead? There are no doors.

Stress is also a key watershed. Non-metallic expansion joints usually withstand low pressure, generally from several kilopascals to tens of kilopascals, and metal expansion energy saving bears several megapascals or even higher. Choosing the wrong material can lead to premature aging or pipeline cracking and leakage. Two days ago, I met a customer, who chose a non-metallic one for cheap. As soon as the operating pressure came up, the fabric bulged and scrapped directly. Therefore, the material is only the appearance, and the working condition is the essence.

Common Myth: Are expansion joints, compensators, metal hoses the same thing?

Many customers call the expansion joint compensator, which is no problem. The two are different names for the same type of equipment. But metal hoses are different. Some people always mix them together. Expansion joint is a section of flexible connection in the middle of rigid pipeline, welded or flanged at both ends, mainly absorbing displacement; A metal hose itself is a bendable tube for use in vibrations, deflections, or situations where frequent movement is required. The price, structure, and use are all different. There are metal hoses, PTFE-lined metal hoses and vacuum special hoses in this station. They are two product lines with expansion joints, so they can't be mixed.

Another myth is to use bellows as expansion joints. In fact, bellows is only a flexible component in the expansion joint, and there must be bellows in the metal expansion joint, but the bellows itself is not equal to the expansion joint. Similarly, a non-metal expansion joint also has a metal frame in it, and you can't say it is a metal expansion joint just because it comes with a metal frame. Therefore, the standard answer to the question "Is the expansion joint metal?" Is two words: look at the model.

Next time someone asks you if the expansion joint is metal, you directly ask him: Which kind are you asking?

Two days ago, the equipment supervisor of a thermal power plant called me, saying that the non-metallic expansion joint at the outlet of their induced draft fan was leaking, and the noise at the scene was so loud that the air volume was obviously not enough. He asked me if I wanted to replace it with a new one directly. I asked him not to rush to change it, and checked it in order, and finally solved the problem for less than 500 yuan. I have seen too many similar cases. Today, I will write the investigation ideas clearly. If you encounter them, just follow them.

Air leakage is no trivial matter: energy consumption and corrosion will come to your door

Let's talk about the harm first, otherwise you don't take it seriously. The most direct impact of non-metallic expansion joint leakage is the increase of fan power consumption. If a part of the sealed flow rate of the flue gas system is missed, the fan has to increase the power to make up. A simple comparative data: for every 1% increase in air leakage rate, fan power consumption increases by about 2% to 3%. It is normal for the air duct matched by a 300,000-kilowatt unit to consume hundreds of kWh of electricity an hour. The extra electricity bill in one year is enough to replace several expansion joints.

Even worse is corrosion. When the flue gas leaks out, along with the condensed water, sulfur dioxide and chloride ions are all attached to the surrounding pipelines and equipment surfaces. We have seen a case where the pipe bracket was next to the air leak point. In less than half a year, the corrosion layer of the bracket peeled off like fish scales. If you really have to wait until the equipment is thoroughly corroded before repairing it, the cost is not to be stopped by another expansion energy saving.

Find the leakage point first: Look at it with a flashlight, and you will know it with the smoke method

There is no need to guess the location of the air leak, it is just those few places.

First, the skin surface. The skin of non-metallic expansion joint is a fabric fiber layer, which is washed and aged in high-temperature smoke for a long time, and is most prone to tiny cracks and even holes. Use a flashlight to stick to the skin slowly, and see that the light transmitting point is the leakage point. When the crack is fine and can't be seen, take a piece of paper and rub it on the surface of the skin. The place that is sucked is the air leakage point.

The second place, the flange seal. Where the flange surface is connected with the steel pipe, the sealing gasket is aged and deformed or not compacted during installation, so the gap will come out. This is not easy to find by looking outside. Take a smoke pipe and walk along the flange to see where the smoke drifts.

The third place, the beading. The bead is used to press the skin tightly on the flange frame. When the bolts on the bead are loose or the bead itself is deformed, the skin will come out of the groove, and the air leakage is not small. None of these locations are difficult to check. It takes ten minutes.

Emergency treatment: Patches and bolts have their own specifics

Find the leakage point, and decide whether to fill or replace it depending on the situation.

Small cracks or pinholes on the skin can be patched with high-temperature repair tape or silicone cloth, which can last for a while. Note that the surface is cleaned before repairing, and the dust and oil stains are not wiped off. The tape is also a white sticker, and it will fall off after a few days. This method is suitable for temporary repair, and it is no problem to last until the planned shutdown for maintenance, but it is not a long-term solution.

If there is an air leak caused by a loose bolt, don't screw it when you come up. Let's first see if there are any signs of displacement on either side of the flange-thermal expansion will pull the bolts loose, especially in the thermal power plant case I mentioned earlier. The normal practice is to loosen the bolt, adjust the natural position of the expansion joint, and then tighten it symmetrically according to the standard torque. Direct hard screwing may deform the pressing strip, or tear the skin folds, which is really the worse the more you repair it.

Radical cure plan: change when you should, don't make up for it blindly

What circumstances don't make up? The skin is aging and hardening in a large area, the surface cracks are densely packed, or the flange and bead have been deformed. At this time, it is not something that can be solved by repair. It's safer to replace it directly with a new one.

Rectangular non-metallic expansion jointIt is suitable for rectangular air ducts, such as the inlet and outlet of induced draft fan and the inlet and outlet of desulfurization tower;Non-metallic expansion joint (fabric fiber expansion joint)It covers circular and special-shaped pipes, and the fabric fiber skin itself is the core sealing layer and displacement compensation layer.

Don't just look at the interface size when selecting a model. The three parameters of medium temperature, working pressure and displacement amount determine the number of layers and material structure of the skin. For example, if the flue gas temperature is 200 °C or less, a conventional combination of silica gel cloth + glass fiber is sufficient; If the smoke temperature exceeds 350℃, fluororubber or ceramic fiber layer should be considered. The pressure is simple. Generally, the pressure of flue gas duct is not high, but it should be noted that the skin is easily deflated under negative pressure conditions, so a supporting skeleton has to be added.

Don't forget matching inspection: lax baffle door will aggravate air leakage

Expansion joint air leakage is sometimes its own problem, but half the probability is related to supporting equipment. Two days ago, I met a customer. The expansion joint was replaced with a new one or leaked. After checking it, the problem was in the upstream and downstream baffle doors.

The desulfurization flue gas baffle door or ordinary flue gas baffle door is not closed tightly, which causes the system pressure fluctuation during operation, and the skin of the expansion joint is repeatedly agitated, and fatigue cracks appear. Double-seal structures such as circular baffle doors (double seals) and double-seal single-axis circular baffle doors, although the sealing grade is high, the wear of the sealing surface must be checked regularly. It is best to open and close the manual plug-in type insulation door or the electric plug-in type insulation door once when the machine is shut down for maintenance to see if there is any sticking. The whole air duct is a system, and the expansion joint is just one of the links. It protects the duct, and you have to protect it.

Routine Maintenance: Spend Your Effort at Usual Times

At the end of the day, non-metallic expansion joints shouldn't wait until there is an air leak to attract attention. During daily inspection, take a flashlight to see if there are any scratches or cuts on the surface of the skin, especially pay attention to whether there are any places scratched by the insulation iron sheet. The torque of the flange bolt is checked every six months. Don't be too troubled. The standard requires that the torque value be as much as it is. Don't rely on the feel. The fixing bolt of the guide tube is also easy to loosen. After falling off, the high-temperature smoke directly washes the inner layer of the skin, and the wear speed is more than ten times the normal.

According to JB/T 12235-2015 standard, in the inspection items of non-metallic expansion joints, the skin condition, flange connection and the integrity of the guide tube are listed. If you do maintenance in the front, it is very common for an expansion joint with passing quality to last three or five years, and the air leakage problem has nothing to do with you. If we wait for the air leak to deal with it, then the money for repairing it is almost enough to buy a new one.

So, what should I do if I encounter air leakage in non-metallic expansion joints? First, reassure yourself and go through it in the above order: find the leakage point, assess the severity, deal with it urgently, change it when you need to, check the supporting equipment, and then adjust the daily maintenance strategy. In most cases, there is no need to go to war at all.