Foreign non-metallic expansion joints are not as simple as the three words "foreign brand"
As soon as many purchasers see the word "import", the barrage of "good quality and long life" automatically pops up in their minds. But the non-metal expansion joint is completely different from the metal compensator. Metal depends on corrugation deformation to carry hard, non-metallic depends on flexible fabric to absorb heat displacement. Foreign manufacturers do accumulate in multi-layer composite structures, but don't just stare at the beautiful curve chart in the brochure. Have to ask clearly: How many layers is the skin? Thermal insulation in the middle? Where are fluororubber and polytetrafluoroethylene used? These directly determine how many years the expansion energy saving lasts.
The "non-metallic expansion joint (fabric fiber expansion joint)" and "rectangular non-metallic expansion joint" of our site are also the same principle, but the application scenarios and process details are different. If you look at foreign samples side by side with domestic drawings, the structure is quite different, but you can't see how many processes people have stuffed between fabric layers. Therefore, in the first step of model selection, don't rush to compare brands. First, ask for people's cross-sectional views, and take them apart layer by layer.
From JB/T 12235 to ASTM/EN: How standard differences affect actual selection
There is a national standard for non-metallic expansion joints in China, which is JB/T 12235-2015. Foreign countries take ASTM or EN system. But to be honest, the name of the standard can't bluff the expert-the standard is only the lowest threshold, and the key depends on how far the manufacturer implements it. For example, for the displacement test, some domestic manufacturers can give a theoretical calculation value. Some foreign brands will do fatigue tests according to actual working conditions, simulate tens of thousands of thermal cycles, and then dump the measured data to you. The gap between the two can only be truly felt after your equipment is online and running for two years.
What about that? Ask suppliers to produce third-party testing reports, and don't trust verbal promises. Temperature resistance and pressure resistance parameters may be written exactly the same in the domestic and imported instructions, but the margin is hidden in the details. It is also nominal to 300°C. People may use 350°C silicone cloth as the outer layer, while domestic products may use 250°C in order to save costs. So don't just stare at the numbers on the table, ask about the test conditions.
Power Plant Desulfurization, Cement Kiln Tail, Flue Gas Pipeline: Comparison of Typical Application Scenarios
Foreign brands have a lot of experience in the three fields of desulfurization system, cement kiln tail and flue gas pipeline, because their industry started early and their case database is thick. The medium in the desulfurization system contains acidic corrosive gas, and the skin must bear the tossing of dilute sulfuric acid; The cement kiln tail is high temperature and dust, and the fabric layer is easily worn down; The flue gas pipeline is large displacement and low pressure, which requires extremely high fatigue life.
But this is not to say that domestic production can't match it. For example, the "desulfurization flue gas baffle door" and "high-temperature axial expansion joint" in our station are specially designed to match these working conditions. The key is that you have to know which one your working conditions are closer to-is it mainly high temperature? Corrosion-dominated? Or is it displacement-dominated? Don't use a general-purpose model as a panacea, that's the real pit.
Pits that are easy to step on during model selection: displacement, pressure and media corrosiveness are all indispensable
Some people only look at how much displacement the expansion energy saving absorbs, and ignore that the pressure thrust will destroy the pipe support. This is not alarmist. I have seen a project with my own eyes, and the expansion excerpt is quite "accurate". As a result, as soon as the pressure comes up, the fixing bracket is directly deformed. Some people just stare at the temperature resistance value, forgetting that the sulfide in the smoke will accelerate the aging of the rubber layer of the skin. You say it was wrong or not?
There are also installation direction, guide tube setting, flange sealing surface-these details are clearly marked in foreign samples, but on-site installers don't necessarily look at them. No matter how good the foreign non-metallic expansion joint is, it will still leak if it is installed backwards and the guide tube is misaligned. Think about it, is this the truth? Selection is not just picking a model. You have to do the stress analysis of upstream and downstream pipelines together.
Domestic substitution and import coexist: when to choose foreign brands, when to choose domestic is enough
If the project requires international certification, or the owner designates an imported brand in black and white, it must be used if it should be used, and don't go through the contract. However, if it is only conventional thermal displacement compensation, domestic non-metallic expansion joints are fully competent. The delivery period is short, the after-sales response is fast, and a phone person will arrive if there is a problem. The imported ones will wait for customs declaration and sea shipping, and a month will pass.
Two days ago, I met a customer who insisted on designating a European brand. As a result, the delivery date was delayed for four months, and the whole project was stopped waiting. And guess what? Finally, the domestic one arrived in two weeks, and there is no problem with the operation until now. Alas, why bother? Choosing the right or not the expensive is what a mature engineer should do. The working condition parameters in your hand are much more valuable than the brand logo.