Are non-metallic expansion joints belonging to raw materials? I was stunned. You might think that with "non-metal" in the name, it should be some kind of material, right? Actually, it's not. Non-metallic expansion joints, such as "non-metallic expansion joints (fabric fiber expansion joints)" and "rectangular non-metallic expansion joints" in our station, are all finished compensators that have been processed, which are used to absorb the thermal displacement and vibration reduction of pipelines. Raw materials refer to unassembled things such as steel plates, rubber and fibers, and expansion joints are a functional component made by combining them. These two are completely different from the same concept. If you get mixed up, you will not get the right purchase.
What is the core material? Don't be biased by the name
The main materials of non-metallic expansion joints are non-metallic composite materials such as fabric fibers, rubber and polytetrafluoroethylene. For example, "rubber compensator" and "rubber PTFE compensator" use rubber and PTFE layers. These materials themselves are raw materials, but after a series of processes such as cutting, vulcanization, molding and flange connection, they become an independent equipment. Think about it, the band part of "non-metallic expansion joint (fabric fiber expansion joint)" is made of multiple layers of fiber cloth and rubber. Can this be called raw material? No, this is the finished product made by a set of crafts. To say that it counts as raw material is as outrageous as saying that a car is iron ore.
Where is the boundary between raw materials and finished products?
Break up the difference again. For example, you buy a bundle of carbon steel pipes, which are raw materials, and use it to bend, weld, add bellows, and finally get a "universal corrugated expansion joint", which is the product. Similarly, although the name of non-metallic expansion joint sounds like a material, it already has the parameters of complete interface size, compensation amount and temperature resistance grade. When you purchase, what you need is to select the type, not take a piece of cloth and cut it yourself. So, don't be taken off by the word "non-metallic" in the name. If you buy the non-metallic expansion joint as a raw material and let the construction team cut it on the spot and then stick it to the pipeline, there will definitely be a big problem-the pressure level and compensation amount are completely wrong, leakage is still a trivial matter, and if the pipeline stress is cracked, it will be a safety accident.
The application scenario is the most telling
Non-metallic expansion joints are especially common in electric power, cement and chemical industries. For example, although the name of the "metal corrugated expansion joint in cement industry" in our station is metal, the "rectangular non-metallic expansion joint" is the main force in the air duct and flue of cement plant-because it is corrosion resistant, light in weight and can absorb multi-dimensional displacement. The desulfurization system of power plants is also inseparable from it, such as the "desulfurization flue gas baffle door" used with non-metallic expansion joints. Think about it, if it is used as a raw material, the construction team will paste fiber cloth directly on the pipe? That leaked in less than three days. In actual projects, non-metallic expansion joints are purchased as finished products, with standard flange connection sizes, and they can be bolted on directly on the spot.
How to avoid pits in purchasing? Three main points
First, get the drawings or parameters, and first make it clear whether you want "non-metallic compensator" or "non-metallic ring belt". The ring belt belongs to a spare part and can be replaced separately, which is regarded as a semi-finished product, but the whole expansion joint body is still a product. Don't purchase spare parts as whole machines, and don't treat whole machines as spare parts. Second, pay attention to the implementation standard-a common question and answer in our station mentioned that the national standard for non-metallic expansion joints is JB/T 12235-2015, which stipulates that it must be a finished product after type test. So next time the supplier tells you that "non-metallic expansion joints are the raw materials made of fiber cloth", you can directly say back: Is JB/T 12235 written as a product standard or a material standard? Third, look at the product label. Regular non-metallic expansion joints will be marked with the model, compensation amount, pressure grade and factory date when they leave the factory, but raw materials do not have these.
One more long-winded word
The non-metallic expansion joint is not a raw material, it is a professional pipe compensation device. Understand this positioning, and selection, quotation and acceptance will not be chaotic. If you still want to know the detailed comparison between it and metal expansion joint, or the specific installation method, you can look through the information of "rubber compensator" and "high-temperature axial expansion joint" in our station-those are real industry cases.