Did you really choose the right non-metallic compensator for primary flue gas pipes?
How "tricky" is the working condition of a flue gas? Temperature, corrosiveness and dust content can make the ordinary compensator "lie flat" directly. The primary flue gas temperature at the boiler outlet often fluctuates between 140℃ and 180℃, and it can instantly rush above 200℃ when it encounters start-stop conditions. The flue gas contains sulfur and chlorine, and when it meets water vapor, it is an acidic condensate, and the metal parts are gnawed through in minutes. There is also dust-the primary dust content of blast furnaces or power plants is often tens of grams per standard cubic meter, which is extremely abrasive. In this environment, metal expansion joint? Tsk, a life span of two years is considered a high incense. Therefore, non-metallic compensators are commonly used in the industry-but note that not any "cloth bag" can carry it.
Why can non-metallic compensators "overcome rigidity with softness"?
Structurally, it has no corrugated metal layer at all, and relies on composite fabrics (such as polytetrafluoroethylene and silicone rubber-coated fiberglass cloth) plus multiple layers of thermal insulation cotton and sealing film. It is not afraid of acid and alkali, has good elasticity, can absorb multi-directional displacement, and the key is fatigue resistance-think about it, the thermal expansion in rectangular pipes is generally released by angular displacement and lateral displacement, and the metal bellows is prone to stress cracking, while the non-metallic fabric layer runs smoother and smoother. Moreover, it has light weight and low requirements for pipe supports. Two days ago, a cement factory customer told me, "Before used metal, every six months leakage; If you replace itNon-metallic expansion jointIt hasn't been changed once in three years. " — That's the reality.
There are pits in the selection, so don't be fooled by the word "non-metal"
Rectangular non-metallic expansion joints are suitable for large diameter rectangular flues, rounded shapes are also available. However, the primary flue gas pipeline often has positive pressure, and the sealing requirements are high, so the guide tube and heat insulation layer must be in place. In order to save money, some manufacturers only use a layer of aluminum foil cloth + glass wool, which will carbonize and fall off in a few months at high temperature. The correct approach is: the inner layer is reinforced with stainless steel wire mesh ceramic fiber blanket, the middle is sandwiched with high silicon oxide cloth, the outer skin is coated with PTFE fiber glass cloth, plus anti-corrosion metal frame. And don't forget to match the guide tube-what is the specific function of the guide tube? It mainly prevents smoke from directly washing the skin, while reducing the flow resistance.
Non-metal vs. metal, which one to choose?
Many purchases ask "which is cheaper". If I want to say, the later maintenance fee is enough for you to buy three sets if you choose the wrong one time. Metal bellows are okay in low temperature, low pressure and clean media; However, non-metal is the only correct solution to the hot, dirty and corrosive working condition of flue gas. Moreover, non-metal has a big advantage: easy disassembly and assembly. You calculate that to replace a metal expansion joint, you have to cut, weld and re-insulate, and the downtime is at least two days; Non-metal directly open the flange bolt to change the skin module, and it can be done in half a day. The difference in maintenance costs is not a little bit. But be warned,The national standard for non-metallic expansion joint is JB/T 12235-2015。
Installation and maintenance – a lot of people are rolling over here
When you leave the factory, the manufacturer will pre-stretch a certain amount. Don't rush to screw the nut to death when you go to the site, and leave a thermal displacement margin. The direction of the arrow of the expansion joint? Generally point to the flow direction of the medium, don't install it backwards. For details, you can see what we have sorted out beforeThe direction of the arrow of the expansion joint refers toDescription of. Also, although the non-metallic compensator allows certain installation errors, the tube must be centered, and too much deflection will lead to skin wrinkles and shorten the life. In terms of maintenance, it mainly depends on whether the skin is aging and cracked, and whether there is dust accumulation. It is recommended to check the external skin surface once a quarter, and shine a flashlight on the back to see if there are light-transmitting holes-it should be replaced when the light is transmitted.
Having said so much, the core is one sentence: it is almost the "only solution" to select a non-metallic compensator for a flue gas pipeline, but we must look for the three-layer composite structure + qualified guide tube. Don't be fooled by low-priced goods. Sooner or later, the money saved will turn into maintenance bills. If you're still struggling, consider this question: Can your pipeline withstand unplanned downtime losses due to compensator failure?