Is the metal expansion joint model? The answer is yes, and there are enough models to make your scalp tingle. The reason is simple-pipeline working conditions vary widely, and it is simply unrealistic for one model to dominate the world. Temperature, pressure, displacement direction, medium corrosiveness, any variable changes, the required expansion joint has to be replaced. Two days ago, I met a customer and asked, "Is there a universal expansion joint?" I can only tell him: The universal type you want is actually just one of the models, and you have to make the diameter, pressure and wave number clear, otherwise you can't install it.
Classification by structure and compensation mode, which is the most commonly used division method
The axial type expansion joint is specifically responsible for absorbing the thermal expansion and contraction of the pipe along the axis direction. Like the most commonUniversal corrugated expansion jointAnd when the pipe diameter is large and the pressure is highExternal pressure single type axial type expansion joint-This structure can hide the bellows in the external shell, avoid the medium directly washing the wave crest, and is suitable for high temperature steam pipeline. Lateral and angular types deal with lateral displacement and angular deflection.Compound hinge transverse expansion jointThe lateral displacement is absorbed by the cooperation of two sets of hinge groups, and is often used at the corner of L-shaped or Z-shaped pipes. Pressure balanced type (Straight pipe pressure balanced expansion joint、Curved tube pressure balance type expansion joint) can offset the blind plate force generated by internal pressure, and is suitable for high-pressure large-diameter pipelines, such as the main steam pipeline of power plants. Each structure has its applicable scenario-if you choose the wrong one and install it, it will either be broken or leaked. Think about it, if a DN600 steam pipe is incorrectly installed with an axial type without pressure balance, the blind plate force can push the fixing bracket down.
More targeted by application industry and media
The power station industry has dedicatedCorrugated expansion joint for power station industryThe material and fatigue life requirements are according to the DL/T standard; The cement industry has its ownThe metal corrugated expansion joint in cement industry is wear-resistant and high-temperature resistant, and the problem of dust accumulation has to be considered. In the desulfurization system, the flue gas contains sulfide and moisture, and the common metal expansion joint can't bear the corrosion at all, so it has to be usedDesulfurization flue gas baffle doorCooperateNon-metallic expansion joints (fabric fiber expansion joints)。 At high temperatureHigh-temperature axial expansion joint, the working temperature can reach above 800℃, the bellows must use Inconel 625 or GH3030. Large-diameter and thick-wall situations, such as hot air ducts, have to beLarge-diameter thick-walled expansion joint, the wall thickness should be enough, and a guide tube must be added to prevent vortex erosion. And vacuum pipes, like those used for air-cooled island vacuum pipesThe double hinge expansion joint of air-cooled island vacuum pipe, the ordinary model can't bear the negative pressure at all-the bellows will be sucked flat. The standards and material requirements of different industries vary greatly, so don't mix them. Two days ago, a chemical factory used the model selected for the steam pipeline on the acid pipeline, and the result was perforated in two months.
Classified according to special functions and materials, it specializes in treating various "difficult and complicated diseases"
PTFE-lined hoseAndPTFE compensatorSpecially dealing with strong corrosive media-lined with PTFE, it can withstand almost all strong acids and alkalis, but the temperature cannot exceed 200℃.Special hose for vacuumIt has reinforcing ring and special sealing structure, which can ensure that the bellows will not be unstable under negative pressure.The directly buried (fully buried) type expansion joint is directly buried underground, and the shell has been treated with anti-corrosion and waterproof, which is suitable for directly buried heating pipelines without compensation.rubber compensatorAndThe rubber PTFE compensator is good at absorbing vibration and noise-the rubber section can reduce the vibration transmission of the pipeline, and it is most used in the fan inlet and outlet and pump outlet pipelines. These special models are often not found in ordinary selection manuals, so they have to be customized with manufacturers. You said that if a heating pipe buried under the road surface uses an above-ground expansion joint, it will rust through in half a year. Is this the truth?
Then how do you understand the doorway in the model?
General expansion joint models include nominal diameter (DN), pressure class (PN), wave number, material code, connection mode and other information. For example, "DN200 PN1.6 304 8 wave" can basically describe aUniversal corrugated expansion jointCore parameters-diameter 200mm, pressure 1.6MPa, material 304 stainless steel, 8 waves. But don't expect to conquer the world with a string of letters. Manufacturers usually provide detailed size diagrams and technical parameter tables. When selecting a model, check the displacement (axial, transverse and angular), fatigue life (how many cycles can withstand in the design life) and the guide tube design-these are more critical than the model itself. If the guide tube is installed backwards or the material is wrong, the high-speed airflow will directly split the bellows. There is also the adjustment of the tie rod nut, which should be locked before installation and loosened after operation, otherwise it will limit the displacement.
Finally, a suggestion: Don't think about the model yourself
The actual working conditions (medium, temperature, pressure, displacement direction and quantity, connection mode) are sorted out clearly, and directly thrown to professional manufacturers to let them match the most suitable model. After allMetal expansion jointOnce installed wrong, the cost of replacing is much more expensive than buying a new one-you have to stop the pipe, empty it, cut it, and re-weld it, not counting the loss of construction time. Remember, the model is the result, and the working condition is the source. You tell me what medium is going through your pipeline, how high it is, how much pressure it is, which way it goes, how much it moves, and I can tell you to use itCompound hinge transverse type orStraight pipe pressure balanced type. Don't be too troublesome. The more you fear trouble, the easier it is to get into trouble.