Why are non-metallic compensators almost all custom made?
Simply put, the standard is simply not enough. Think about it, the flue gas temperature in the flue of the power station is always five or six hundred degrees, the medium at the tail of the cement kiln is still corrosive, and the pipe sizes at the inlet and outlet of the desulfurization tower are even more varied-round, square and special-shaped. If you look through the JB/T 12235-2015 standard, you will understand that this standard only stipulates technical requirements, test methods and inspection rules, and the size and shape are not limited at all. Therefore, non-metallic compensators (that is, we often call non-metallic expansion joints) are born custom parts.
"Can you buy a spot install?" I said that if you are not afraid of air leakage or short life, you can try it. But to be honest, the on-site flange spacing, medium temperature and displacement all don't match, and the spot stock will have to be scrapped if it can't last a maintenance cycle. Do you think the money was spent unjustly?
What are the key parameters?
Let's talk about the size first-circle, rectangle and special shape can be made. Like this site'sRectangular non-metallic expansion jointIt is specially equipped with rectangular pipes. More flexible material: silicone cloth, fluorine tape and PTFE film can be selected for the fabric fiber layer, and the temperature range is from-40℃ to 1000℃ full coverage. Whether the inner filling layer is ceramic fiber or rock wool depends on the temperature resistance and heat insulation requirements. There is also structural customization: Do you want a deflector? Do you want to bring a flapper door? For example, this site'srubber compensatorAndRubber PTFE compensatorOne is flexible and the other is corrosion-resistant. Where it is used depends on the working conditions.
By the way, stress levels are also key. 0.1MPa is sufficient for normal working conditions, but some vacuum pipes (such as air-cooled islands) need to be usedSpecial hose for vacuumThat kind of sealing structure, otherwise it will deflate when vacuumed.
The customization process is actually four steps
In the first step, you throw over the pipe parameters: diameter, medium, temperature (including long-term operating temperature and instantaneous maximum temperature), pressure, axial/transverse/angular displacement. In the second step, according to the parameter selection, we use the formula to calculate the stiffness and compensation amount-this can't be slapped on the head. Referring to the formula for calculating the stiffness of the expansion joint mentioned in the previous question and answer, we have to use the data to speak. The third step is to make drawings for you to confirm: the number of flange bolt holes, the length of the guide tube and the position of the tie rod are clearly marked. The fourth step is to do pressure test and displacement test before the production leaves the factory to ensure no leakage.
The whole cycle is fast one week, and the slow one is determined according to the complexity. Such as matchingDouble-sealed round flapper doorOrElectric plug-in insulation doorThis kind of assembly will take longer, after all, it needs to be linked to test.
Customizing the three easiest pits to step on
The first pit: only report the temperature but not the instantaneous maximum temperature.There is a customer of a power plant whose flue gas is usually 300℃, so he chose ordinary silicone cloth. As a result, the temperature rushed to 500℃ when starting and stopping, and the silicone cloth directly burned through the end of a pot. Remember that instantaneous temperatures can be twice as high as long-term temperatures, and material selection must be counted as peak values.
The second pit: ignore installation space.The flange spacing at the site is small, the compression amount of the non-metallic compensator is not enough, and it will die when installed, and the displacement will all be converted into pipeline stress, and the weld will crack. Therefore, we must measure the flange spacing before customization to leave a margin for pre-compression.
The third pit: forgetting to consider particulate matter in the medium.If the smoke is dusty, the fabric layer will be worn out quickly. What to do? The guide tube must be thickened or welded with cemented carbide. We have encountered customers in the cement industry who did not add deflectors and changed them twice in three months. Later, it was changed to a guide tube with surfacing layer, which took two and a half years. These problems are particularly common in power station industry and cement industry projects, and we have dealt with them too many times.
How is it used in the industry?
Power station boiler outlet, forHigh temperature axial expansion jointCombined with rectangular non-metallic expansion joint, it absorbs three-way displacement-think about it, when the boiler starts and stops, the pipeline expands thermally, contracts coldly and vibrates, and the metal bellows alone can't bear it at all. The flue gas pipeline at the tail of the rotary kiln in the cement industry has frequent heat exchange, and the fabric fiber expansion joint is the most reliable because of its strong vibration absorption ability. In the desulfurization system,Flue gas baffle doorAndDesulfurization flue gas baffle doorSupporting use-baffle door to isolate smoke, non-metal expansion joint to compensate displacement, both do not delay.
And vacuum pipes, such as air-cooled islands, have to be usedDouble hinge expansion joint for air-cooled island vacuum pipelineThat structure can withstand negative pressure while also absorbing angular displacement. Each industry has its own set of customized logic. To put it bluntly, it is to translate the working condition parameters into materials and structures-the medium temperature determines the fiber layer, the particulate matter determines the guide tube, and the pressure determines the sealing structure.
Do non-metallic compensators support customization? Of course it is supported, and it has to be customized. If anyone tells you to "buy the spot", you have to be more careful-80% of them have never touched the pit of high-temperature dusty pipes.