Let's talk about a question that many people ignore: What is the difference between single wave and multi-wave?
Most of the expansion joints we usually come into contact with are multi-wave-the more ripples, the greater the compensation amount. This intuition is right. However, there is one exception: when the pipe space is limited, or when it needs to withstand higher internal pressure and axial force, multi-wave becomes a burden. Circular metal single-wave expansion joint, to put it bluntly, means that the bellows has only one circle of peaks and troughs, which has a simple structure, but has high rigidity and strong pressure bearing capacity. Not long ago, I met a customer who was doing a power station project. The temperature of his steam pipeline was 450℃ and the pressure was 2.5MPa. At first, he chose a multi-wave expansion joint, but the bellows became instable and collapsed directly during the test run. Later, it was changed to a single wave, and the problem was solved. Do you say that multiple waves add to chaos on some occasions?
Where is the structural hardcore of a single-wave expansion joint?
Its core is that single-layer or double-layer metal bellows. The material is usually 304, 316L or Inconel 625, which is resistant to high temperature and corrosion. Compared with multi-wave, single-wave design is more "rigid"-wave height and wave distance are calculated by stiffness (refer to this siteStiffness and Calculation Formula of Bellows）。 Because there is no extra wave crest, the ability to resist plane instability is stronger, and it is especially suitable for working conditions with large external pressure or axial force. This site'sExternal pressure single axial expansion jointIn fact, it is very similar to the idea of single wave, except that single wave is the ultimate simplification. In addition,Universal corrugated expansion jointThere is also a single wave option in, but many people don't pay attention.
Don't think that single wave can only be made with small diameter-large diameter and thick wall can also be made
Many people stereotype that single wave can only be used in small pipes below DN50, wrong. This site hasLarge diameter thick wall expansion jointFor this kind of product, the single wave structure can still be above DN1000. The key lies in wall thickness and waveform design. For example, used inMetal Corrugated Expansion Joints in Cement IndustrySome preheater pipes have high temperature and dust, and multiple waves are easily blocked by dust accumulation. The inner wall of single wave is smooth, and the guide tube is well matched (refer toSpecific Function of Expansion Joint Guide Tube), and instead more durable. Think about it, how hard is it to overhaul a cement plant once? One less downtime saves hundreds of thousands.
The two easiest pits to step on in model selection: insufficient compensation amount and excessive stiffness
Think that the single wave compensation amount is small and it can't be used at all. In fact, a single wave can work withCompound hinge transverse expansion jointOrCurved tube pressure balance expansion jointTo be used in combination-transfer displacement through hinges or tie rods, so that the single wave bears axial displacement, and lateral displacement is done by other structures. The second pit: too much stiffness causes the pipe thrust to exceed the standard. Single-wave stiffness is high, and if the pipe support design does not keep up, it is easy to transmit force to the equipment. Therefore, the selection must be checkedHow to adjust the tie rod nut of expansion jointAndDoes the screw need to be removedThese details, avoid problems in the installation phase. Many projects are planted in thinking "almost OK".
Installation and maintenance say two real things: How much trouble does single-wave expansion save energy?
Because of the simple structure, the single-wave expansion joint does not need to be pre-stretched like multi-wave (unless special requirements) when installing, just center and tighten the flanges at both ends. In terms of maintenance, there are few single wave leakage points, and the probability of bellows rupture is low. If it is used on flue gas pipes, match this station'sDouble-sealed single-axis circular baffle doorOrFlue gas baffle doorCan effectively isolate and overhaul. For service life, refer toService life of expansion jointQuestion and answer, single wave can be used for 10 years in a non-corrosive environment. There was a chemical plant that took 8 years to change, and it didn't leak once during this period. How much labor was saved?
To sum up: The round metal single-wave expansion joint is not a panacea, but it is more reliable than multi-wave in scenarios with high pressure, small space and high stiffness requirements
If you have a project on hand, you might as well look through this siteUniversal corrugated expansion jointAndExternal pressure single axial expansion jointPage, look at the parameters.