What Exactly Are Round Metal Expansion Joints? The factory sells more than just a bellows
Many people think that a circular metal expansion joint is a bellows, and it is done by welding it to the pipe. It's so simple. The streets are full of factories. In fact, the expansion joint is a key component used to absorb the thermal displacement of pipelines, compensate for installation errors, and reduce vibration and noise. High-temperature and high-pressure corrosive occasions such as power stations, cement and desulfurization all depend on it to save their lives. What the factory sells is not a pipe, but a complete set of displacement compensation schemes-from bellows material, wall thickness, wave number, to the matching of guide tube, tie rod and flange, each of which directly affects the life of the equipment.
For example, if you see aCorrugated expansion joint for power station industryIt may have a guide tube to reduce scouring and a tie rod to restrict lateral displacement; Replace withMetal Corrugated Expansion Joints in Cement Industry, the material has to be replaced with high-temperature resistant alloy, and the wave distance has to be encrypted. These details, laymen simply can't see.
When selecting a factory, look at the process first: bellows forming, heat treatment and welding these hard indexes
If the craftsmanship is not up to standard, the product is a time bomb. Look at forming first-hydroforming and roll forming are two ways: hydraulic is suitable for thick-walled, non-standard and large-diameter parts, such asLarge diameter thick wall expansion jointWave pattern is full and stress distribution is uniform; The rolling efficiency is high, but the wall thickness thinning rate should be strictly controlled, otherwise the corrugated root will easily crack.
Then there's the heat treatment. After the bellows is formed, there is residual stress inside. If it is not removed, it will not take long for stress corrosion to crack. Regular factories have solution treatment or stress relief annealing furnaces, and the temperature curve can be checked. Not to mention welding-the weld between bellows, flange and guide tube must be inspected by RT or PT, otherwise the pipe will collapse directly after desoldering.
How to pick between different industries? Product Differences in Power Station, Cement and Desulfurization Scenarios
The pipeline of power station has high pressure and large temperature fluctuation, so it should be selectedHigh temperature axial expansion jointOrStraight pipe pressure balanced expansion jointSo that a large amount of axial displacement can be absorbed without generating thrust. The cement industry has a lot of dust, and the temperature fluctuates high and low. The bellows must be equipped with wear-resistant guide tubes, and the material should be at least 316L starting. It is best to useMetal Corrugated Expansion Joints in Cement IndustryThis specially designed wave plate thickness should be thickened.
The desulfurization scene is the most disgusting-the flue gas contains sulfide, the temperature repeats up and down the acid dew point, and ordinary stainless steel will rot in a few days. Must useDesulfurization flue gas baffle doorMatching expansion joint, or PTFE-linedPTFE compensator。 And guess what? Some factories use 304 stainless steel to impersonate 316L, which is perforated in half a year. Therefore, before signing the contract, we must clarify the material grade and require a warranty.
Factory service capability is equally important-non-standard customization, installation guidance, after-sales guarantee
Pipeline working conditions are all kinds of strange, and standards can't cover them at all. Such asDouble hinge expansion joint for air-cooled island vacuum pipelineFactories with this kind of non-standard parts, complex structure and no design ability, will only change the size of the general type, and either tie rod interference or insufficient compensation when installed.
Installation guidance is also critical-the direction of the arrow of the expansion joint refers to the direction of the medium flow. Should the screw be removed? Depending on the working condition: the pre-tensioned screw must be removed before the compensator works, otherwise it is equivalent to not being installed. Some factory instructions are written like heavenly books, so it is better to send a technician directly to the site. encounterLarge tie rod expansion jointInstallation, level and moderation are almost stuck, and you don't know without a master staring at you.
After-sales, don't just look at the length of the warranty period. Most factories have a one-year warranty, but the real problems happen after two or three years. Reliable factories will make life estimates and even provide testing services-for example, measure the wall thickness of the bellows for you every year, and replace it in advance if it is found to be thinned to a dangerous value. This is not a value-added service, it should be.
Several common pits to help you avoid processing plant traps
- Pit One: The offer is ridiculously low.You get what you pay for, the material of corrugated pipe is several thousand yuan per ton, and there is also a price difference in welding labor. If the price is more than 30% lower, either cut corners or use inferior boards.
- Pit 2: Claim "full models in stock".You think it's convenient to have it in stock? Most of the expansion joints are made by order, and the size, material and wavenumber are customized. Only the general type can be in stock. If you really want to buy in stock, you can ask if there is anyUniversal corrugated expansion jointInventory, but don't expect it to be used on specific projects.
- Pit 3: There are no actual cases.Official website of the factory said that "products are widely used in electric power and cement", but when asked for a list of cases, he hesitated. Find a factory for power station projects, you have to see if he hasCorrugated expansion joint for power station industrySupply records of.
- Pit 4: Ignore flange standards.Many factories are equipped with national standard flanges by default, but the actual pipeline may be American standard, Japanese standard or non-standard. If the flange bolts are not spaced in advance, it will be more troublesome if they can't be welded on site.
Alas, I met a customer two days ago, and I bought a batch of expansion joints cheaply, but it broke within a few months of installing it. When disassembled, the weld of the bellows did not penetrate at all, and the thickness of the guide tube was not enough. Find a factory again, the construction period is delayed for two months, and the loss is more than ten times the money saved. Therefore, when choosing a factory, don't just look at the price, craftsmanship and service are indispensable.