A flue master's lesson: It turns out that the non-metallic compensator of expansion joint is the "carrying the handle"
Last summer, I went with an old flue master to fix a flue pipe. The master's surname is Li. He has worked for twenty years, and his hands are covered in calluses. When I went to the scene, I saw that the metal expansion joint of the pipe was cracked, the interface was smoking, and the surrounding ground was black and ashy. The master squatted down, took a flashlight to shine on it, and sighed, "Another pot to save money." He told me that this place had changed the bellows once before, but the manufacturer said that the metal one could withstand the high temperature, but it collapsed after only half a year. I said what to do? He pointed to a dusty pipe beside him and said, "Do you see it? That one that has been used for three years is a non-metal compensator. It is nothing wrong." I was stunned for a moment. This thing looked like it was made of cloth. It was really more durable than metal?
To put it bluntly, non-metal is not a "cloth pocket", but a stacked technology
Later, I specially checked the information, only to realize that the "non-metallic compensator" mentioned by the master is actually what we often call "non-metallic compensator of expansion joint", also called fabric fiber expansion joint. The biggest difference between it and metal expansion joint is that metal absorbs energy by corrugation deformation, but it can't bear corrosion and frequent vibration; Non-metallic materials are superimposed layer by layer by layer by flexible materials (such as silica gel, fluororubber and glass fiber cloth), which can not only withstand high temperatures, but also absorb multi-directional displacement-laterally, axially and angularly, and can be eaten. And guess what? The state has also issued a special standard for non-metallic expansion joints: JB/T 12235-2015, in which the technical indicators and test methods are clearly written. To put it bluntly, this thing is not a "cloth pocket fool", but has strict industrial norms.
The products in this station are quite complete, such as "non-metallic expansion joints (fabric fiber expansion joints)" and "rectangular non-metallic expansion joints", all of which are for flue gas pipes. There are also "rubber compensators" and "rubber PTFE compensators", which are specialized in dealing with acid-base corrosion. What the master repaired that time was the flue gas pipe, which was high in temperature and contained sulfur, so the metal one couldn't bear it. It would be worry-free to replace it with a rectangular non-metallic expansion joint. I was still curious at that time: How do I install this thing? He told me that when the non-metallic compensator is installed, the tie rod nut must be aligned, not screwed too tightly, and there must be room for thermal expansion and contraction. The function of the expansion joint tie rod is to limit protection and prevent excessive stretching. Tsk, these details are written in a bunch of books, so it's better to watch the master do it once on the spot.
Power stations, cement plants and desulfurization systems- -the "main battlefield" of non-metals
Speaking of application scenarios, non-metallic compensators are especially used in power stations, cement plants and desulfurization systems. For example, it was mentioned in the article "Metal Corrugated Expansion Joints in Cement Industry", but non-metallic ones are actually more suitable for dusty and corrosive environments. Think about it, the flue gas from the desulfurization tower is wet and sour, and the metal one will rust through in a few years. Non-metallic because the material itself is corrosion-resistant, coupled with the multi-layer sealing structure, the life is longer. A customer told me that their factory used to use metal, which was changed once every two years, and it lost more than 100,000 yuan once it stopped production; After changing to a non-metallic compensator, there was no incident in four years. After this calculation, who would choose the wrong one?
"How to choose the model and size of the expansion joint?" I told him that the non-metallic compensator depends on three parameters: diameter, temperature and pressure. The size should be according to the pipe drawing, don't blindly estimate. Also, if the medium in the pipeline is viscous particles, the guide tube must be thickened-the specific function of the expansion joint guide tube is to protect the flexible layer from being washed. In addition, don't forget that the non-metallic compensator itself does not bear pressure, but only compensates for displacement, so the pipe supports and hangers have to keep up. If the flange is not tightened during installation, or the gasket is leaking, then no matter how good a compensator is, it will be useless. It's like wearing shoes. Shoes are good shoes. If you don't put your feet in the right position, you will still sprain your feet.
Master's Golden Quote: Hard when you should be hard, soft when you should be soft
So you see, behind the lesson of a flue master is actually the re-understanding of "flexibility" in the whole industrial pipeline system. Metals have the rigidity of metals, and non-metals have the softness of non-metals. The key is to use them in the right place. Later, the master took over the job, and all recommended customers to use non-metallic compensators, especially flue gas pipelines and desulfurization systems. He said to me, "Don't just believe that metal is more robust. That's called a stereotype. Whether something is good or not depends on the working conditions. Just like us, hard when it should be hard, soft when it should be soft, that's the real skill." I pondered, and this truth made sense anywhere. If you are worried about the thermal expansion and contraction of pipes now, you might as well take a look at the column of "Non-metallic expansion joints" in our station. Anyway, don't wait for the pipe to crack before regretting it-the maintenance cost is enough to buy several compensators.