What exactly is a non-metallic compensator for cold air duct? What's the difference between it and a metal corrugated compensator
To put it bluntly, there is low-temperature air in the cold air duct, but the temperature difference when the equipment starts and stops is still not small. The thermal expansion and contraction of the pipeline makes the metal parts easy to fatigue and crack. The non-metallic compensator relies on the soft absorption of displacement by the fabric fiber and rubber composite layer, and can also withstand corrosion. And guess what? In the cold air duct system of many power plants and cement plants, the one in our station is usedNon-metallic expansion joint (fabric fiber expansion joint), this thing is half lighter than the metal one, and the installation is hassle-free. Metal corrugation compensator (such as in a stationUniversal corrugated expansion joint) It is suitable for high-temperature and high-pressure media, but non-metal is the king of cost performance in the occasion of low-pressure and low-temperature, frequent start-and-stop of cold air duct.
Core Structure Dismantling: Don't be fooled by the word "non-metal"
The outer layer is a fluororubber or silicone rubber coating for sealing and temperature resistance, the middle is a glass fiber or ceramic fiber reinforcement layer to provide strength, and the inner layer has a flow guide tube (refer to our siteFunction of Expansion Joint Guide TubeQ&A) to prevent airflow scour. Some square air ducts still have to be matchedRectangular non-metallic expansion jointThe flange connection is fixed with a pressure plate. Two days ago, I met a customer who asked if this thing could be used on the flue gas duct. I said no. The temperature and corrosiveness of the cold air duct and the flue gas are completely different, so they have to be replacedDesulfurization flue gas baffle doorThat kind of product. Have to mix it? I'll leak it out for you in three months.
The three easiest pits to step on when selecting a model
First, just look at the temperature and not the pressure.Although the temperature of the cold air duct is low (usually no more than 250℃), the fan outlet may have positive pressure. If an ordinary fabric compensator is selected, it will be a matter of time before the bulge leaks. Take the one from our stationNon-metallic expansion joint (fabric fiber expansion joint)Speaking, the structure with reinforcing ribs or steel wire rings must be selected under positive pressure conditions, otherwise it is only a matter of time before the fiber layer is stretched and deformed, and the seal fails.
Second, ignore installation space.Some sites have cramped spaces and require non-metallic compensators to absorb both axial and lateral displacements. In this case, structures with tie rods or hinges must be selected, similarCompound hinge transverse expansion jointThe design ideas. There was a project before, the space at the corner of the cold air duct was only 200mm, and only non-metal pull rods could be used-the function of the pull rod is to put it bluntly to limit excessive displacement and prevent the compensator from being pulled off. The specific adjustment method can be turned over in the stationHow to adjust the tie rod nut of expansion jointThe Q&A.
Third, buy small factory goods for cheap.The national standard JB/T 12235-2015 for non-metallic expansion joints has clear requirements for sewing strength and flange flanging. Without that process, the service life will be directly halved. For example: the flange width of a qualified compensator is at least 30mm, and the sewing needle length is controlled within 5mm. Small factories may cut corners to 15mm and the needle length is 10mm, and the edge will open as soon as the wind blows. You save those hundreds of dollars in exchange for a year's shutdown for maintenance. Which one is cost-effective?
Install and maintain those doorways
Does the screw of the expansion joint need to be removed? — According to the situation. If the cold air duct compensator leaves the factory with a transport screw, it must be loosened or disassembled after being installed in place, otherwise the displacement will not be absorbed, and the equipment will be pulled directly when it is opened. But if it is an adjustment screw (similarHow to adjust the tie rod nut of expansion jointQ&A), which is used for cold tightening or pre-stretching, and the compensation amount must be calculated according to the installation temperature. For example: when the ambient temperature is 20℃ and the pipeline operating temperature is 150℃ during installation, the compensator needs to be pre-stretched by 20%, and the tie rod nut has to be screwed to the corresponding scale.
The non-metallic compensator is afraid of sharp objects scratching, so the welding slag must be cleaned when welding the flange, otherwise the fiber layer will be cut when the wind blows during operation, and the air leakage rate will rise exponentially. I have seen the most exaggerated case. After the customer welded the flange, the slag was not cleaned. Three months later, a 5cm hole was broken at the bottom of the compensator, and the air leakage directly made the fan consume 15% more power.
When should I change? Don't wait for a leak to fix it
Non-metallic compensator life is generally 3-5 years, but depends on the working conditions. If you find cracks in the outer coating, corrosive exudates on the surface, or abnormal vibrations during operation (perhaps the internal fiber layer has broken), consider replacement. Contrast the metal expansion joint (refer to our siteMetal expansion joint weight tableAndMetal hose size comparison table), the disassembly and assembly of non-metal is simple, without moving the pipeline, just loosen the flange bolts and replace them with new parts, and the downtime can be compressed to half a day. And the cost is low, a setNon-metallic expansion joint (fabric fiber expansion joint)The price is only about 1/3 of the metal bellows, and the maintenance fee saved is enough to buy several sets.
In the final analysis, choosing a cold air duct non-metallic compensator is three words: depending on the working conditions. Temperature, pressure, displacement, space, none of them can leak. When you're not sure, go through the stationFunction of Expansion Joint Guide Tube、Function of expansion joint tie rodThose questions and answers, or directly ask the manufacturer to select the parameter table. Don't wait for a leak before repairing it. That's a waste of money.