First, the core value of metal expansion joint: it is not just "compensating displacement"
When many people mention metal expansion joints, their first reaction is "absorbing thermal expansion". Yes, this is the basic skill. But its benefits go beyond that – vibration and noise reduction, preventing pipeline thrust from damaging equipment, adapting to complex spatial layouts…To put it bluntly, it is the "flexible joint" of the entire pipeline system. Without it, as soon as the high-temperature steam pipe is hot, the flange weld will crack; When the equipment vibrated, the whole pipeline shook. Two days ago, I met a customer. The pump unit in the factory building always had problems. I changed the machine seal three times, and finally found that the pipeline stress was not eliminated. Add a universal corrugated expansion joint, and the problem is solved directly. So don't underestimate this thing. It is an "invisible life-saving talisman" in power stations, cement, chemical industry and desulfurization industries.
Second, how to "save life" of metal expansion joint under high temperature and high pressure working conditions
The thermal expansion and contraction of pipelines are physical laws, and hard carrying will only lead to accidents. Metal expansion joints rely on bellows structure and absorb displacement by elastic deformation. For example, high-temperature axial expansion joint, which is specially used to deal with axial expansion and contraction; The transverse expansion joint of compound hinge solves the transverse offset. For example, the corrugated expansion joint used in the power station industry has a steam temperature of five to six hundred degrees and a pressure of more than ten MPa. Ordinary rubber compensators can't bear it at all, so stainless steel or heat-resistant alloy metal bellows must be used. Here's a key point: the deflector. Many customers don't know what it is for-it can guide high-speed airflow away, prevent the bellows from being directly washed, and its life can be several times worse. To put it bluntly, if you choose the right model and material, the metal expansion joint is the "fuse" of the system.
3. Selection of different scenarios: from power station to cement, don't choose the wrong one
And guess what? Many people hold an expansion joint parameter and want to be universal in all occasions. That's a dream. In the flue gas pipeline of power station industry, the temperature is high and the pressure fluctuates greatly. Double-sealed single-axis circular baffle door is commonly used with large-diameter thick-walled expansion joint. In the cement industry, there is much dust and severe wear. The metal corrugated expansion joint in the cement industry has to be lined with wear-resistant lining. There are also desulfurization flue gas baffle doors, which are highly corrosive, and lined with PTFE hose or PTFE compensator is the correct solution. As for the vacuum pipeline of air-cooled island, the double hinge expansion joint of air-cooled island vacuum pipeline has to be used to resist negative pressure. So don't think about it once and for all, you have to choose according to the medium, temperature, pressure and displacement direction. If you are not sure, go directly to the manufacturer for the model selection table, or refer to the metal expansion joint weight table to estimate the model.
4. Installation does not mean completion: those pits of installation and post-maintenance
The screw must be removed! Many novices are afraid of trouble, so they leave the tie rod nut unremoved. As a result, the expansion joint can't expand and contract freely, so it is installed for nothing. The role of the expansion joint tie rod is to protect the bellows during transportation, and once in place, it must be loosened or removed. There is also the direction of the arrow-that is the direction of the medium flow, and the guide tube will block if it is installed backwards. Also pay attention to the coaxiality when installing, deviation will lead to stress concentration. What about post-maintenance? Regularly check whether there are cracks and corrosion points on the surface of the bellows, especially the external pressure single axial expansion joint with external sleeve, which is easy to accumulate water and rust. To put it bluntly, three points for selection and seven points for installation, and the remaining ninety points for daily inspection. Don't wait until it leaks before replacing it, it will be expensive.
V. Life and cost: How long can an investment last?
The design life of metal expansion joints is usually calculated by the number of cycles, such as 10,000 or 20,000. How long can it actually run? Depends on working conditions. It is also stainless steel bellows, which may be fine for more than ten years when used on clean steam pipes; Used in desulfurization flue gas containing chloride ions, it will be perforated in half a year. So don't just look at the price, but whether the material matches. For example, vacuum special hoses are used in high vacuum systems, which have extremely strict requirements for leakage rate, and are expensive but must be used. Rubber compensators are cheap but have limited temperature and pressure resistance. The initial investment of metal expansion joint is high, but the frequency of maintenance and replacement is low, and the whole life cycle cost is cost-effective. You taste, you taste. Finally, let me add: the expansion joint and the compensator are the same thing, so don't be fooled by different names. Anyone who knows the business knows that if you choose the right thing, the system will be safe and stable; Wrong choice, headache every day.