At the installation site, it was found that the metal expansion joint was so long. Can you cut off a section with a cutting machine and then weld it? This kind of problem is actually quite common, especially when there are errors in on-site piping. But the answer is clear: absolutely not. It's not a matter of whether you can or not, it's risking the whole plumbing system.
Take it apart to see what's in the metal expansion joint
Based on our stationUniversal corrugated expansion jointFor example, the core component is the bellows-through a specific wave design and wall thickness, it is elastically deformed to absorb the thermal displacement of the pipe. The wave height, wave pitch and number of layers of bellows are calculated by special software before leaving the factory. You cut off a section, which is equivalent to tearing up the designed stress distribution diagram. Not to mention the auxiliary parts such as the guide tube and the tie rod. Their cooperation with the bellows is fixed, and there is no place to weld after cutting.
Why don't you just cut a piece and weld a flange on it? If you think about it, each section of corrugation of the bellows has a corresponding stiffness value, and a sudden change in stiffness will form near the weld after cutting. During operation, the pipeline is repeatedly stretched and compressed, and that position is the stress concentration zone. It is only a matter of time before fatigue cracks.
What happens to cutting and welding? Three hard injuries
First, local stress concentration.When the bellows leaves the factory, the force is uniform, and the stiffness of the weld changes suddenly after cutting off a section, which is equivalent to tying a dead knot on the rubber band. It will break after a few pulls, not to mention high-temperature and high-pressure industrial pipelines. Second, the sealing property is directly scrapped. Metal expansion joints (e.g.Corrugated expansion joint for power station industry) Usually used in steam, hot water and other media, even micron-scale cracks can cause leakage. After you cut and then weld, the weld quality can catch up with the original factory integral molding? Third, the amount of compensation returns to zero. The axial displacement and lateral displacement of the original design are all wrong. When the pipeline expands, there is nowhere to release it, ranging from equipment vibration to pipeline pull-off-this kind of thing has occurred in many accidents in power plants and chemical plants.
You saw off the shock spring of the car once, can it still drive normally? A truth.
What's the right thing to do? Don't move the welding gun, use your brain
If the length is not appropriate, the best solution is to change the specification directly. There are various types in our site:External pressure single type axial type、Compound hinge transverse type、Straight pipe pressure balance type…From the design stage, the dimensions should be calculated according to the actual pipeline route. Take before installationMetal hose size comparison tableOrExpansion Joint Weight TableCheck, contact the manufacturer for customization if necessary. If I really bought the wrong thing, I would rather return it than move the welding gun-no matter how expensive the return freight is, it is cheaper than the maintenance cost of pipe burst.
What should I do if I find it is long after I have installed it? Check the tie rod nut first. The expansion joint tie rod is originally used to adjust the pre-deformation, and the proper adjustment of the tie rod can compensate for the small installation error. How exactly to adjust? We had a question-and-answer article about it earlierHow to adjust the tie rod nut of expansion jointThe core principle is to twist both sides synchronously, and don't twist the bellows. If it's too different, change it honestly.
Can rubber or non-metallic ones cut? Not either, but for different reasons
thatrubber compensatorOrNon-metallic expansion jointCan you cut it? The rubber PTFE compensator is a flexible material, which can barely make do with heat sealing or bonding after cutting, but the strength is greatly reduced. The metallic ones are completely different —Sleeve type pipe expansion jointBy the sliding compensation of the inner and outer sleeves, if you cut off a section, it will destroy the sliding surface and get stuck. Remember one principle: All corrugated expansion joints (includingHigh temperature axial expansion joint、directly buried expansion joint、Large diameter thick wall expansion jointetc.), any cutting and welding modification is strictly prohibited after leaving the factory. This is the iron law of the industry, and there are no exceptions.
We still have one in our stationFlue gas baffle door、Round flapper doorThese products have different structures, but they can't be changed on the spot. Pipeline safety is not a child's play. If you save hundreds of dollars, you may lose tens of thousands of maintenance costs-you can calculate this account yourself.
Something real in the end
Instead of thinking about how to cut, it is better to make an order on the spot. Use a laser rangefinder to measure the distance between the pipeline joints once, and then compare the installation length of the expansion joint. Really worry, send the pipeline routing diagram to the manufacturer and let the technician help you choose the model.
If you have installed it wrong, check if the tie rod nut can be adjusted? As mentioned earlier, small errors can be adjusted. If it's much worse, don't hesitate to return it for an exchange. Remember: the expansion joint is the cartilage of the piping system, and you cut and weld it, and the whole system goes head-to-head. Something is going to happen.