1. What exactly does the "range" of non-metallic expansion joints mean? -Three core parameters determine whether you can use
"How many degrees do you carry for non-metallic expansion energy saving?" Of course, temperature is important, but if you only stare at this one number, you will most likely flip over. The "range" of non-metallic expansion joints, to put it bluntly, is the intersection of three dimensions:Temperature, size, medium。 Either one is less, and there can be problems with installing it-either it leaks in a few months, or it can't be installed at all. Two days ago, I met a customer and chose a fabric fiber expansion joint resistant to 500℃. As a result, it was sulfur-containing flue gas, which was corroded and worn in three months. Do you think he was wronged or not? Not injustice, because he didn't ask the media at all.
2. Temperature range: How many degrees can the fabric fiber carry? Which gear is the rubber compensator suitable for?
Let's startNon-metallic expansion joints (fabric fiber expansion joints)。 The main materials are glass fiber, ceramic fiber, polytetrafluoroethylene and other composite layers, and the continuous use temperature is between-40℃ and 600℃ under normal working conditions. A short-term peak can rush to 700°C, but only if the medium does not contain corrosive components. Whilerubber compensatorBy rubber elasticity to compensate the displacement, the upper temperature resistance limit of general EPDM is about 150℃, and the fluororubber (FKM) can reach 250℃. Note that after the temperature resistance of the rubber compensator exceeds 200℃, the life of the rubber compensator will drop off by a cliff. Don't expect it to last for a few years. Example: Non-metallic expansion joint for high-temperature fan export in cement industry, with a temperature of about 350℃, 3 layers of ceramic fiber + fluororubber sealing layer are selected, which has not been changed for five years; If you switch to a rubber compensator, it will carbonize in three months.
3. Size range: From the small round tube of DN50 to the rectangular non-metallic expansion joint several meters wide, where is the boundary?
The size depends on the shape of your pipe section. For circular pipesNon-metallic expansion joint, the smallest caliber can be made DN50 (e.g. some cooling water pipes), what about the upper limit? I've seen DN5000 on the flue of large power stations, or even bigger. However, the most asked is the rectangular pipeline-such as the inlet and outlet of desulfurization tower in power plant and the flue gas pipeline at the tail of cement kiln, which must be used at this timeRectangular non-metallic expansion joint。 This kind of product can be as wide as 5 meters, 6 meters, or even more than ten meters on one side, but it is limited by the tensile strength of fabric materials. If it exceeds 8 meters wide, it needs to be reinforced by a middle partition. Another detail: the non-standard size rectangular expansion joint mold opening fee can not be low, it is best to confirm the drawings before ordering. Is there an upper limit? There is no absolute ceiling in theory, but it is difficult to transport too much, and on-site installation is also a job-you can't tear down half a wall for an expansion joint, can you?
4. Medium and working condition range: desulfurization flue gas, cement dust, hot air of power station-different industries have different requirements for materials
-Desulfurization flue gas: The flue gas after wet desulfurization contains sulfuric acid and sulfurous acid condensate, which is extremely corrosive and must be usedPTFE compensatorOr non-metallic expansion joints lined with fluororubber. Ordinary rubber compensators are scrapped in a month.
-Cement dust: High-temperature dusty gas, severe abrasion, wear-resistant guide tube should be added inside the non-metallic expansion joint, and the outer layer of high silicon oxide fiber should be matched.
-Hot air in power station: The medium is clean but the temperature fluctuates greatly (300~450℃). Just choose aluminum silicate ceramic fiber cloth + stainless steel wire mesh reinforcement layer. Low cost and long life.
Again, some working conditions have both corrosion and high temperature, such as waste incineration flue gas. At this time, it has to be compounded with multiple layers: the outer layer is temperature resistant, the middle is heat insulated, and the inner layer is anti-corrosion. Don't try to save trouble, save money and change more later.
5. The easiest pits to step on during model selection: the practical details not written in the standard JB/T 12235-2015
The national standard JB/T 12235-2015 does stipulate the technical requirements of non-metallic expansion joints, but some pain points are not mentioned-or not mentioned in detail enough. For example:Configuration of flow guide tube。 The wind speed of many on-site pipelines is very high (for example, above 15m/s). If the guide tube is not added, the flue gas will directly wash the fabric layer and wear it out in a few months. However, the standard only says that "it is advisable to set the guide tube", but does not say when it must be set. Another examplePre-stretch installation: Non-metallic expansion joints usually have pre-stretched quantity when they leave the factory, and the tie rod needs to be loosened after installation. Many people forget this operation. If you forget, the expansion joint is useless. Andlimit screwProblem: The screw that is locked during transportation must be loosened after installation, otherwise the displacement will all eat on the frame. These details will not be marked on the drawings, but each one directly affects the life span.
6. Three-step self-inspection method: Quickly judge whether your pipeline system is suitable for non-metallic expansion joints
Step 1: Look at the pressure. The withstand pressure of non-metallic expansion joints is usually 0.1~0.3MPa. If it exceeds 0.5MPa, you must use it with caution, or even change the metal expansion joints directly. How stressed is your system? Is it more than 0.5MPa? If it exceeds, replace the metal corrugated expansion joint or sleeve pipe expansion joint as soon as possible.
Step 2: Look at temperature + medium. Summarize the media composition table, find the highest temperature point, and then compare the material resistance table. For example, 80 ℃ benzene-containing medium, rubber compensator is definitely not working, and must be lined with PTFE. Don't guess by your feeling.
Step 3: Calculate displacement. Non-metallic expansion joints are good at absorbing axial and angular displacements, but don't count on torsional displacements. If your pipe has a large twist or lateral misalignment, prioritize tie rod type or hinge type metal expansion joints. If you are really unsure, find a sample station to the scene to gesture, which is more useful than reading the manual. In just three steps, 80% of the unsuitable options can be screened out. Remember, selection is not about filling in forms, but about settling accounts-get it right and save years of trouble; Miscalculated, disassembly and assembly once saves more money than you did in the first place.