1. What exactly is the general nonmetallic compensator used for? — — First see the essential difference between it and the metal compensator
"Isn't your non-metal expansion joint just a soft joint? What's the difference between it and a metal bellows?" This sounded quite common, but if you really thought so, the choice of model would most likely flip.
Universal non-metallic compensator (also called non-metallic expansion joint, this site products are classified asNon-metallic expansion joint (fabric fiber expansion joint)Andrubber compensator) The essential difference with the metal compensator is not "soft or not", but "how to compensate". Metal compensators (e.g.Universal corrugated expansion joint) By the deformation of the bellows to absorb the displacement, it bears the pressure thrust and has high structural strength; However, the non-metallic compensator relies on the flexural deformation of fabric or rubber, and hardly produces elastic reaction force. In other words, metallic compensators are "hard carry" and non-metallic compensators are "come along".
Large displacement, low pressure, high temperature flue gas, corrosive media. Think about it, how many days can metal bellows last in the face of high temperature sulfur oxides? Rubber compensators or rectangular non-metallic expansion joints with laminated fabric fibers can hold it instead. So don't come up and ask, "Which is the function of this universal non-metal compensator better than the metal one"-it's not the same track at all.
2. Disassembly of three core functions: displacement absorption, vibration isolation and noise reduction, corrosion resistance and temperature resistance
The functions of general non-metallic compensators, to put it simply, are three, but each one is particularly specific.
First, absorb displacement.The pipe expands when it is heated, shrinks when it is cold, and deviations caused by installation errors. If these displacements are forcibly transmitted to the equipment, flanges collapse and welds crack, which is nothing new. The non-metallic compensator can easily absorb axial, lateral and even angular displacement, and the key is – it creates no thrust. Like inCorrugated expansion joint for power station industryWhere you need to withstand high pressure, you can't use non-metallic ones; However, in the case of low pressure and large displacement of smoke duct, non-metallic ones are simply tailor-made.
Second, vibration isolation and noise reduction.When the fan and compressor are turned on, the whole pipeline is shaking. Metal bellows also dampen vibrations, but non-metallic materials (rubber, fabric) have much better damping properties. When you touch the running rubber compensator with your hand, you can clearly feel that it is "eating" the vibration like a gummy piece. Those air ducts in the steel mill are connectedRubber PTFE compensatorAfter that, the noise can be reduced by 5-8 decibels, which is not metaphysics, but the characteristic of the material itself.
Third, corrosion resistance and temperature resistance.It depends on the specific material. Fabric fiber expansion joints (a type of non-metallic expansion joints) can withstand high temperatures above 600℃, and have good resistance to acidic gases such as SO₂ and NOx-because the substrate is coated with glass fiber + silicone rubber or polytetrafluoroethylene. The temperature resistance of rubber compensator is worse, generally 80-120℃, but it is better in chemical corrosion and wear resistance. You let the metal compensator go to the flue after the desulfurization tower? Three day piercing. The non-metallic ones can run for three to five years instead.
3. Don't just look at the price when selecting: Should you choose fabric fiber or rubber material under different working conditions?
Many people ask, "How much is the cheapest non-metallic compensator?" I usually ask, "What is the temperature of the medium in your tube? Is there any acidic substance?" A large number of questions were asked.
Fabric fiber expansion joint(That's what this site saysNon-metallic expansion joint (fabric fiber expansion joint)) The main battlefield is high-temperature smoke. For example, the kiln tail of cement plant, the boiler outlet of power station and the hot air duct of iron and steel plant, with a temperature of 300-1000℃, must be superimposed with multiple layers of fabrics. The inner layer is insulated with ceramic fiber, the middle layer is reinforced with glass fiber, and the outer layer is sealed with fluororubber or silicone rubber. This structure is also divided into single layer and multi-layer, and the places with high pressure have to be supported by stainless steel wire mesh.
rubber compensator(includingRubber PTFE compensator) is more suitable for low temperature, humidity and corrosive liquid occasions. For example, desulfurization slurry pipeline, sewage treatment plant, acid-alkali pipeline of chemical plant. Rubber materials include nitrile, chloroprene, ethylene propylene and fluororubber, which are resistant to different media. PTFE-lined rubber compensator (rubber PTFE compensator) can withstand almost all strong acids and alkalis, but the temperature resistance is 200℃ to the end.
Look at the temperature and the medium. Don't choose the rubber one because it is cheap, and the flue temperature will burn through directly as soon as it comes up; Don't use all fabric fibers for insurance. As a result, doubling your budget is not corrosion-resistant. Isn't this truth very simple? But in practice, nine of the ten selections flipped over on this.
4. Those easy pits in installation and operation and maintenance-should the tie rod be dismantled? What is the use of a deflector?
When ordinary non-metallic compensators leave the factory, they mostly carry a few screws-the so-calledtransport tie rod。 The function of this thing is to pre-press or pull the compensator to prevent deformation in transit. Many installation teams save trouble, and they are welded directly with the tie rod, and they are not even dismantled after installation. And the result? The compensator is locked by the tie rod, and the displacement that should be absorbed is not absorbed at all. The stress of the pipe is concentrated at the interface, and it is torn soon. So when you encounter one with a tie rod (such asLarge tie rod expansion jointThat kind of structure), be sure to loosen the tie rod nut or remove it directly after installation. How to tune it? In the FAQHow to adjust the tie rod nut of expansion jointThe conclusion is: first loosen to the free state, and then adjusted according to the pre-deformation amount required by the design, not the tighter the better.
Againguide tube。 A stainless steel deflector is often added inside the non-metallic compensator, note that it is not for good looks. The guide tube has three functions: First, it protects the non-metallic fabric from being directly washed by high-speed airflow (it will leak if it is worn out); The second is to guide the smooth transition of airflow and reduce vortex; The third is to reduce the wear and corrosion of the inner wall of the compensator by the medium. In design, the direction of the guide tube must be consistent with the airflow-the direction of the arrow is the direction of the airflow, which must not be reversed during installation. Once, the customer installed the guide tube backwards, and as a result, the airflow directly tore the fabric layer, which was a big loss.
If the skin (fabric layer) on the outside of the non-metallic compensator is damaged, bulging or leaking, don't think about repair welding directly. Non-metallic materials are afraid of high temperatures, and the welding torch will burn through when touched. The correct approach is to temporarily seal with high-temperature resistant silicone rubber first, and then replace the entire compensator module. Metal parts (flange, angle steel) can continue to be used, but non-metallic parts must be replaced with new ones.
5. From power stations to cement plants: Several application cases in typical industries to help you understand its true value
It's not enough to talk about theory alone. Let's talk about two real scenes.
Power Station Industry: Boiler Smoke Duct.A 300MW coal-fired unit, the flue from the boiler outlet to the denitrification inlet, the cross section is 4m ×3m, the medium temperature is 350℃, and it contains sulfur. The original metal corrugated expansion joint was corroded and worn in two places in half a year, and more than 1 million yuan was lost when the furnace was shut down for maintenance. Later replaced withRectangular non-metallic expansion jointThe outer layer is glass fiber cloth coated with fluororubber, the inner layer is ceramic fiber felt, and the stainless steel guide tube is added. It has not been changed for 3 years, and because the non-metal has stronger ability to absorb displacement, the force of the pipe support has also decreased. After calculating this account, although the one-time investment is 30% higher, the whole life cycle cost is lower.
Cement industry: Kiln tail smoke chamber.The kiln tail temperature of the rotary kiln in cement plant is as high as 1000℃, and it also carries a lot of dust and corrosive gas. This place can only be usedNon-metallic expansion joint (fabric fiber expansion joint)And with multiple layers of insulation. A 5000t/d production line, four round non-metallic expansion joints, with a diameter of 2.8m, are installed between the kiln tail and the decomposition furnace. It is opened and inspected every year during overhaul. The inner fabric layer is intact, only the surface has slight crust. Compared with the situation where the metal compensator next to it needs to be replaced frequently, the maintenance of non-metal is much less.
AndDesulfurization flue、Dust removal pipeline in iron and steel plant、Hot blast furnace in chemical plant…Almost every industry with high temperature, large displacement and corrosive media can see the shadow of general nonmetallic compensators. It is not dazzling, but without it, the reliability of the whole system will drop immediately.
So when someone asks you "what is the function of the universal nonmetallic compensator", you tell him directly: it is the joint, buffer and protective cover of the pipeline system. Choose the right one, worry-free; Wrong choice, bad.