First, let me answer the most straightforward question: Non-metallic compensators are not universal
It's not like standard flanges or bolts, which can be fitted when you take them to the right size. The design logic of non-metallic compensator (that is, we often call non-metallic expansion joint and fabric fiber expansion joint) is tailor-made around the working conditions-temperature, pressure, medium, displacement and installation space, each of which directly determines the structural selection and material matching.
If you take a non-metallic compensator used in the flue of a power plant and install it on the cold air duct of the cement industry, something will probably happen. It's like buying shoes, size 42 feet will make do with a size 43, but let you run a marathon in rain boots, try it?Are non-metallic compensators universal? The answer is clear: not universal.
Then why do some people always think it's "universal"?
Because from the appearance, the non-metallic compensator is just a circle of skin and frame, which seems to have little technical content. Actually, the skin is a layered structure: fluororubber, silicone rubber, PTFE, ceramic fiber, fiberglass cloth, and each layer has its own task-temperature resistance, corrosion resistance, pressure bearing, sealing.
Although they are all non-metallic expansion joints, the number of skin layers can differ by several layers between those used behind the smoke baffle door and those used next to the high-temperature axial expansion joint. The same is true for rubber compensators and rubber PTFE compensators. The PTFE layer is specially used to deal with strong corrosive media. If you use an ordinary rubber compensator to pass concentrated sulfuric acid, it is not a type selection, but a mine planting for the pipeline.
Let's talk about the displacement compensation ability
Axial expansion, lateral deflection and even angular displacement can be done, which is incomparable to metal corrugated expansion joints. But how much it can absorb depends on the design. Rectangular non-metallic expansion joints are usually used in rectangular smoke ducts, and another set of algorithms is matched with circular baffle doors.
You can't regard all non-metallic compensators as universal parts just because of the nominal "large displacement". The pre-deformation amount, the setting of the guide tube and the stiffness of the frame given in the design all directly affect the actual compensation effect. Two days ago, I met a customer who used the double-hinged expansion joint originally designed for air-cooled island vacuum pipeline on ordinary hot air pipeline. As a result, the vibration exceeded the standard-that thing was metal, not an occasion where non-metallic compensators could be replaced casually. On the contrary, non-metallic ones could not be used everywhere.
The installation location and environment cannot be ignored
Non-metallic compensators are common in desulfurization systems, dust removal systems, power station flues and cement production lines, because of large temperature fluctuations, dust and corrosive gases in these working conditions. But if you use it on pipelines with vacuum requirements, you have to weigh it-the non-metallic skin has limited pressure bearing capacity, and it is easy to deflate under negative pressure conditions. At this time, you may have to look at the vacuum special hose or the external pressure single axial expansion joint.
In other words, before selecting a non-metallic compensator, first list the working condition parameters clearly: what the medium is, how high the temperature is, whether the pressure is positive or negative, whether there is acid-alkali corrosion, which is the displacement direction of the pipeline, and whether there is any space limit in the installation position. Only when these parameters are all together can the manufacturer give you the appropriate skin material and structure. If one parameter is missing, the scheme may deviate.
In the final analysis, the non-metallic compensator is a "non-standard custom" flexible connector
It does look similar in many industries, but material formulations, structural details, and connection methods vary widely. The real professional approach is to find the manufacturer to come up with a plan with the working condition parameters, instead of taking a photo to draw a ladle with a gourd. The national standard JB/T 12235-2015 only stipulates the technical requirements and test methods, and does not say that you can install it everywhere if you buy a standard product.
Are non-metallic compensators universal? — Not universal. But you treat it like a custom piece, and it can dry better than a metal compensator under the right conditions. When it comes to model selection, it is never about looking at pictures, but about data.
Next time someone tells you, "Just buy a nonmetallic compensator and install it", ask him: What is the working temperature? Does the medium contain sulfur? What is the displacement amount? If he can't answer it, you can treat it as a joke.