Do you really understand the role of corrugation compensator?
What is the corrugated compensator (also called expansion joint and compensator in the industry) used for? Simply put, it is a flexible joint that absorbs all kinds of displacements and stresses in the pipeline system. Don't underestimate this function. The pipeline can run for tens of meters. When the temperature changes, it expands and contracts. If it is hard, the weld will collapse and the flange will leak, which is a loss of real money. So figuring out its specific role is more important than anything else.
I met a customer two days ago. The steam pipe has been used for two years, and the flange interface began to leak. When I removed it, I saw that the bellows were cracked. After asking, I found out that the displacement was not counted at all in the original selection, so I bought a general-purpose corrugated expansion joint to deal with it. Alas, I have seen many cases of this kind, and I have one feeling: if I don't understand the function of the corrugated compensator, I will have to pay tuition sooner or later.
First role: to compensate for thermal displacement-this is the skill of eating
Steam pipes, hot water pipes and flue gas pipes, the temperature goes up and down, and the pipes stretch and contract. For example, corrugated expansion joints are used in the power station industry, and hundreds of degrees of steam can easily be expanded and contracted by several millimeters to tens of millimeters, which are all absorbed by bellows. Another example is the metal corrugated expansion joint in the cement industry, which is transported by high-temperature clinker and has a larger displacement. Calculate, a 30-meter steam pipe, the temperature difference is 200℃, the linear expansion coefficient of steel is 0.012mm/m·℃, and the optical axial elongation is 72mm. Hard solder dead? The weld stress has already exceeded the yield limit.
When selecting the model, it also depends on axial displacement, lateral displacement or angular displacement. Like a straight tube pressure balance expansion joint, which is specially used to deal with axial expansion and contraction; Curved tube pressure balance type expansion joint, used at the bend of pipe system, absorbs angular displacement and transverse displacement. A few days ago, there was a desulfurization project, and the pipe system turned around. The design institute used three double hinge transverse expansion joints, and all the displacements were eaten, and the site passed at once. So don't use the general-purpose model to deal with all working conditions, that's called laying mines.
The second function: vibration reduction, noise reduction and impact resistance-bellows can also be used as shock absorbers
As soon as pumps, fans and compressors are turned on, vibration is transmitted along the pipeline, which not only annoys the noise, but also loosens the pipe frame and cracks the weld. Corrugated compensator can eat a part of vibration energy, especially rubber compensator and rubber PTFE compensator, which have good flexibility and obvious vibration isolation effect. Metal hoses also do this job, such as the double hinge expansion joint of air-cooled island vacuum pipeline, which has to bear the vacuum negative pressure and absorb the vibration of the pipeline. And guess what? The pipeline on the air-cooled island of the power plant vibrated at a ridiculously high frequency. Without this thing, the welds would crack in fatigue within three months.
I have seen a cement factory where the fan outlet pipe used a non-metallic expansion joint (fabric fiber expansion joint). The original noise was 90 decibels, but it dropped directly below 75 decibels after replacing it. Why? Fabric fiber expansion energy-saving absorbs multi-directional displacement, and at the same time converts vibration energy into heat energy and dissipates it. Tsk, that's a lot easier than adding a soundproof cover.
Third function: solve installation deviation and facilitate maintenance-less quarrel with field workers
It is impossible to install the pipeline on the spot-if it is slightly crooked by a few millimeters, the stress will be great if it is hard connected. Corrugated compensators absorb these installation errors and allow the pipes to connect smoothly. Especially for large-diameter pipes, it is common for flanges to mismatch. I have seen a chemical plant, DN1000 pipeline, which was misaligned by 8mm during on-site welding. It was adjusted by a universal corrugated expansion joint + tie rod, but it was not reworked. Otherwise, cutting and re-welding, the construction period is at least three days.
In addition, during equipment maintenance, such as manual plug-in insulation doors and electric plug-in insulation doors, a section of pipe needs to be removed. The corrugated compensator can provide additional telescopic space, so there is no need to move the pipe. Think about it. As soon as the expansion joint is compressed during overhaul, the space will come out. After replacing it, it will be stretched back, which will save trouble. Without this function, the entire pipe gallery would have to be demolished.
The fourth role: material adaptation under special working conditions-not all pipes eat the same set
Chemical industry runs acid and alkali, with PTFE-lined hose or PTFE compensator, corrosion resistance. Why? PTFE can carry almost all strong acids and alkalis, but ordinary rubber is scrapped in one month. What about high temperature flue gas pipes? It is necessary to use non-metallic expansion joints (fabric fiber expansion joints), which can withstand the temperature up to 1200℃ and can absorb multi-dimensional displacement. In wet desulfurization environment such as desulfurization flue gas baffle door, acid and alkali resistance and leakage prevention have to be considered. Two days ago, in a power plant desulfurization project, a rectangular non-metallic expansion joint was equipped next to the flue gas baffle door, which was both acid-and alkali-resistant and anti-condensation. After two years of use, nothing happened.
The directly buried (fully buried) type expansion joint is specially used for buried pipelines, which takes into account both resistance to soil pressure and compensation for thermal displacement. Some customers use ordinary expansion joints to bury the ground cheaply, but they are crushed by the soil in half a year-that is called the gain is not worth the loss.
Finally, talk about the selection idea: don't let the corrugated compensator take the pot
It is not just buying a corrugated compensator to solve the problem, but it has to be matched according to the medium, temperature, pressure, displacement direction and installation space. For example, large-diameter thick-walled expansion joints are used in high-pressure pipelines, external pressure single axial type is suitable for long straight pipes, and compound hinge transverse type is suitable for pipe systems with many turns. The attachments of the guide tube and the tie rod are not decorations-the guide tube protects the inner wall of the bellows from being washed by high-speed media, and the tie rod limits excessive displacement. Understand these, and the selection will not overturn.
What does a corrugation compensator do?To put it bluntly, it was four words: Keep the life of the dao. If you choose the right one, the pipeline will run as steady as an old dog for more than ten years; The wrong choice will make you doubt your life every three days. Therefore, the next time you choose a model, don't just look at the price. First, calculate the displacement, check the medium and ask about the working conditions-this is a serious business.