Don't be confused by the name-what exactly does "processing" mean?
To put it bluntly, it is to turn the metal sheet into a bellows by hydraulic pressure, spinning or rolling, and then weld the flange, connector, tie rod and other accessories. 90% of metal expansion joints on the market are made in this way, but the fatigue life of bellows from different processes can be two or three times different. Like what we always sayUniversal corrugated expansion jointMost of them are hydroformed, and the uniformity of wall thickness is good; WhileLarge diameter thick wall expansion jointIt is often necessary to take the route of spinning or cold push molding. Why don't you use hydraulic pressure? Hydroforming requires high molds, with a large caliber and doubling of equipment investment, so small factories can't bear it at all. Although the spinning molding is slow, it can make the effect of gradual wall thickness-suitable for high-pressure scenarios. Therefore, before selecting a model, it is far more reliable to find out the manufacturing process first than to look at the number of fatigue times on the sample.
Type selection is not spelling parameters, working condition matching is more important than anything else
Temperature, pressure, medium, compensation amount, these four are indispensable. Two days ago a customer tookHigh temperature axial expansion jointGoing to go steam, it turned out the medium contained sulfur and the bellows perforated in a few months. Later, it was found that the corrosion resistance of 316L stainless steel in sulfur-containing steam was not enough, so duplex steel or PTFE-lined steel should be used. So don't just look at the model, it's time to goPTFE-lined hoseOrPTFE compensatorDon't save that little money. Used in power station industryCorrugated expansion joint for power plant industryAnd cement industryMetal Corrugated Expansion Joints in Cement IndustryAlthough they are all metal shells, the design emphasis is completely different: the high voltage of the power station should be calculated as the rigidity of the bellows, and the cement should be wear-proof and dust-proof. There are particles in the medium? The guide tube must be thickened, otherwise it will wear out after half a month of high-speed washing.
A detail that is easily overlooked: the configuration of the deflector and the tie rod
The guide tube not only guides the flow of the medium, it also protects the inner wall of the bellows from being washed by high-speed particles. We talked about it in our FAQSpecific Function of Expansion Joint Guide TubeTo put it bluntly, it is to sacrifice yourself to protect the bellows-if the guide tube is worn out, it will be replaced with hundreds of pieces, and the bellows will be broken with thousands of pieces. What about the pull rod?Correct installation method of expansion joint of large tie rodThere is a saying in it-the tie rod nut must be loosened after pre-tensioning, otherwise it is equivalent to locking the expansion joint. Alas, I have seen no less than ten times when I forgot to loosen the nut after installing it on the spot. As a result, once the temperature rose, the bellows couldn't expand and contract, and the flange collapsed directly. AndFunction of expansion joint tie rod, mainly to bear the pressure thrust to prevent the bellows from over-stretching, but the tie rod does not loosen, which is equivalent to handcuffing the bellows.
Which industries love to use machining to form metal expansion joints?
Electric power, petrochemical, metallurgy, cement and municipal heating basically can't run. But the pain points of each industry are different: power plant desulfurization systemDesulfurization flue gas baffle doormatchNon-metallic expansion joint (fabric fiber expansion joint)More, because of corrosion resistance and low-temperature smoke resistance;Double hinge expansion joint for air-cooled island vacuum pipelineSolves the problem of large displacement and vacuum sealing-vacuum leakage is the key, and the double hinge structure can absorb multi-directional displacement;Direct buried (fully buried) type expansion jointSpecially deal with the thermal expansion of underground pipelines,External pressure single type axial typeCan withstand greater external pressure. The wrong type is chosen, from leakage to cracked pipe. There was a thermal company beforeCompound hinge transverse expansion jointWhenStraight pipe pressure balanced expansion jointUsed, as a result, the pipe thrust was not offset, and the bracket was directly deformed.
Buy expansion joints don't just look at the price, life and after-sales are the big head
The service life of the expansion joint depends on the material of the bellows and the number of fatigue designs-the normal general-purpose type can reach more than 1000 times, but the installation deviation or water hammer impact is directly discounted in half. Therefore, regular manufacturers will give fatigue life curves. We haveMetal expansion joint weight tableAndMetal hose size comparison tableThe purpose is to let customers choose according to the actual working conditions. You have to take itCompound hinge transverse typeTo beStraight pipe pressure balance typeUse it, even the gods can't save it. AndRotary compensator、Sleeve type pipe expansion jointThese types have their own applicable scenarios, so don't buy cheap brands. The same size of corrugated pipe, the difference in price is 3 times, the material thickness and corrugated shape are different, and it will crack in half a year on the spot.
Finally, install and acceptance
Arrow direction of expansion jointIt refers to the flow direction of the medium. If the guide tube is installed backwards, it is the plug, which directly holds the pressure. AndDoes the screw of the expansion joint need to be removed?The transport screw is used to fix the bellows to prevent transportation deformation, and it must be removed after installation-but many installation teams try to save trouble and keep it. As a result, the bellows can't be expanded and contracted, and the flange collapses with a bang. Tsk, this kind of low-level mistake happens every year. Remember to check the model, size and pressure level during acceptance. It is best to do pre-stretching or pre-compression. Don't save these minutes. In addition,How to adjust the tie rod nut of expansion joint？ After pre-stretching, loosen the nut to the specified gap, and click it with a micrometer. Don't loosen it for two turns by feeling.
Processing metal expansion joints looks simple, but there are many pits. From the process to the selection, from the guide tube to the tie rod, every detail is linked to the lifeblood of the site. Remember one sentence: working condition matching is a hundred times more important than parameter stacking.