1. Why can high-temperature resistant non-metallic compensators withstand high temperatures? Materials are key
To be honest, when many people come into contact with this thing for the first time, their first reaction is: Can something made of fabric and rubber hold hundreds of degrees of high temperature? Don't worry, let's look at the materials first. High-temperature resistant non-metallic compensators usually adopt multi-layer composite structure, the core of which is the flexible fabric layer in the middle, such as silicone rubber coated glass fiber cloth, polytetrafluoroethylene film and ceramic fiber felt. Silicone rubber itself can withstand temperature to about 250°C, but with the addition of glass fiber and ceramic fiber, the working temperature is directly raised to 600°C or even above 1000°C. And guess what?"Non-metallic expansion joint (fabric fiber expansion joint)" mentioned in the product information of this siteThe more layers, the stronger the heat insulation and temperature resistance.
There is also a layer that is easily overlooked-the internal deflector. Many non-metallic compensators will be equipped with metal guide tubes, which not only guide the airflow to reduce erosion, but also block the high-temperature smoke from licking directly to the fabric surface. This thing is kind of like armor, minimizing the damage from heat radiation. So you see, the confidence of high temperature resistance is not blown out, but layered materials.
2. Temperature upper limit and pressure level: Don't just listen to propaganda, look at national standards and actual measurements
Some manufacturers in the market say that their products can carry 1200°C, but when you ask about the pressure level, they hesitate. According to the National Standard for Non-metallic Expansion Joints JB/T 12235-2015, the upper limit of working temperature of non-metallic compensator is related to the medium, pressure and displacement, not just by looking at the numbers. How do the measured data come from? Take a practical case: The outlet pipeline of the rotary kiln in a cement plant isRectangular non-metallic expansion jointWith a medium temperature of 850°C and a pressure of ±3kPa, the fabric loop belt was changed once after more than two years of continuous operation.
In terms of pressure, non-metallic compensators are naturally inferior to metal because of their flexible structure, so they are generally used in low-pressure flue duct systems (within 0.1MPa). But it has a unique skill: it can absorb multi-dimensional displacements (axial, radial and angular), and it has minimal thrust on the pipe. So don't use it as a pressure vessel, it's more like an elastic soft joint.
What about the performance of high temperature resistant non-metallic compensator? Bottom line: look at the working condition match. For scenarios below 600°C, low pressure, and large displacements, it is much more reliable than a metal compensator.
Third, just with the front of the metal compensator: who is more cost-effective and who is more durable?
Two days ago, I met a customer who insisted on using it on a 300°C flue.High temperature axial expansion jointI asked him why he didn't use non-metallic ones. He said he thought the metal was durable. As a result, the metal bellows should not only choose heat-resistant alloy steel (the cost doubles), but also consider the corrosion problem, and there are many welding points, which makes maintenance troublesome.
Under the same caliber, the price is generally only 1/3 to 1/2 of that of metal. More importantly, its installation accuracy requirements are low, and the on-site cutting adjustment is not distressed. Moreover, it is convenient to repair-if the fabric ring belt is broken, it can be replaced directly, unlike metal bellows that have to dismantle a bunch of flanges. What about longevity? Under normal working conditions (the temperature is lower than the design value, and the medium has no corrosion), the fabric layer can be used for 5-8 years, which is much longer than the fatigue life of metal bellows at high temperature.
But it's not without its flaws. Non-metallic compensators are afraid of sharp hard objects scratching, afraid of direct burning by open flame. So it fits flue gas, hot air, dust ducts, not steam ducts (unless specifically designed). When selecting a model,Product Center of this siteCompare the parameters well, and don't mess with the Mandarin Duck Spectrum.
4. Selection and rollover site: size, displacement and installation direction must not be missing
Let me tell you the truth. In order to save trouble, a steel mill bought a non-metallic compensator and installed it directly. As a result, the fabric burst after one week's operation. Why? The amount of displacement is not counted correctly! The thermal expansion length of the pipe is calculated to be 50mm, and the compensator they bought can only absorb 30mm, so it's weird that it doesn't burst.
Diameter (DN size), compensated displacement (axial/transverse/angular), operating temperature。 If one is missing, it can overturn. Such asRectangular non-metallic expansion jointIt is used on rectangular flue. When installing, it should be noted that the direction of the guide tube must be consistent with the flow direction of the medium, otherwise the guide tube will be washed askew and the fabric will be directly exposed to the high-temperature airflow. There is also the installation direction: non-metallic compensators usually can't withstand pressure thrust, so the tie rod bolt should be adjusted to the appropriate tension (refer to the FAQ "How to adjust the tie rod nut of the expansion joint"), and it can't be screwed to death or too loose.
In addition, where to choose the location is also very particular. Try to avoid installing it behind the elbow or in the turbulent zone downstream of the valve, otherwise the airflow impact will shorten the fabric life. If you can't avoid it, then install an internal anti-scour board (some manufacturers design it as standard, and some have to be customized). You bought the compensator with or without a deflector? This is inSpecific Function of Expansion Joint Guide TubeThere is a detailed explanation in the Q&A, so it is recommended to take a closer look before placing an order.
5. How many years can the life span last? Practical recommendations for maintenance and replacement
The lifetime of non-metallic compensators is greatly affected by temperature fluctuations. If the medium temperature is stable, the aging of the fabric layer is slow, and it is normal to use it for 6 years. However, if it starts and stops frequently and the temperature rises and falls sharply, it may have to be changed in 3 years. Simple maintenance: check the fabric surface every six months for any cracks, aging and brittleness, and any leakage traces. By the way, use a flashlight to see if the internal guide tube is deformed or fallen off.
Once you find bulging or partial ablation of the fabric, don't hesitate to change it quickly. Note when changing: Before dismantling the old ring belt, first confirm that the pipeline has cooled down and relieved pressure, safety first. When installing the new ring belt, the strip bolts should be symmetrically tightened to prevent uneven force. If you can't handle it yourself, go directly to the manufacturer for after-sales service. Many non-metallic compensator suppliers provide on-site replacement services.
After all, what is the performance of high-temperature resistant non-metallic compensators? Depends if you know how to use it. Temperature resistance of materials is a hard index, while installation and maintenance is a soft effort. Get these points thoroughly, and it is definitely the "utility pie" in your plumbing system.