Don't rush it yet, you have to figure out what kind of expansion joint you have on hand-metallic or non-metallic? Why? Because the connection is completely different.
Metallic such asUniversal corrugated expansion joint、High temperature axial expansion jointGenerally with flanges or direct welding; Non-metallic imageNon-metallic expansion joint (fabric fiber expansion joint)Most of them are compressed by flanges and cannot be welded. You open the product information and take a look. IfRectangular non-metallic expansion jointThat is, hold down the frame by bolts, and don't think about moving the welding gun. Two days ago, I ran into a customer who held a non-metallic expansion joint and insisted on welding-the result? The skin burned through, and the whole production line stopped for three days. You say it was wrong or not?
The most commonly used flange connections, 8 out of 10 use this.
First align the pipe flange with the expansion joint flange, and put a sealing gasket in the middle. Note that the material should be temperature-resistant and corrosion-there are often sulfide in the flue, and ordinary rubber gaskets can't stand it. Then twist the bolts diagonally, don't tighten them at once, and gradually apply force in 2-3 passes. Tip: Don't mess with the bolt tightening torque according to experience. There are standard values for different calibers and pressure grades. You can refer to this siteMetal expansion joint weight tableThe torque recommendations included in. After screwing, check the flange clearance with a gauge, and uniformity is qualified. If the gap difference exceeds 0.5mm, it means that the flange surface is crooked and has to be leveled again. Don't be too troublesome, this step saves you from crying when the air leaks in the back.
If you encounter high temperature conditions (such as power station boiler flue), welding connection is more reliable.
When the expansion joint leaves the factory, it usually has a transport screw or tie rod locked. These temporary fixings must be loosened or removed first. Otherwise, once the temperature rises after welding, the expansion joint can't move, and it will be damaged directly. Symmetric segment welding is recommended to reduce thermal deformation during welding. Do NDT after welding? Don't bother, the flue leak is no joke. And guess what? Two days ago, a customer welded the tie rod directly without removing it. As a result, the bellows was torn during the test run and lost a lot. How to dismantle it specifically? You can refer to the question and answer of this siteDo you need to remove the screw of the expansion jointIt is very clear in it.
Flue expansion joints rarely exist alone, and devices such as flue baffle doors and plug-in insulation doors are often connected next to them.
It is recommended to install the expansion joint first and then the baffle door, as the expansion energy saving absorbs the installation deviation. encounterDouble-sealed single-axis circular baffle doorFor this heavy equipment, the expansion joint should be spaced enough between it, otherwise the expansion joint will be squeezed when the valve is opened and closed. And,Manual plug-in insulation doorWhen the guide rail is installed, it should be aligned with the center line of the expansion joint. If the deviation exceeds 2mm, it is easy to get stuck. If you're not sure, look through this siteCorrugated expansion joint for power station industryCase, in which even the installation clearance has a reference value.
Don't rush the smoke after installation, you have to do a few steps to check.
First, make sure that the flow direction arrow on the expansion joint is consistent with the flow direction of the medium-this arrow is not a display, and reverse will cause the guide tube to be washed out and worn. Second, check whether all the tie rod nuts have been adjusted to the working position (how to adjust? Refer to Q&A of this siteHow to adjust the tie rod nut of expansion joint）。 Third, for installations that require pre-stretching or pre-compression (such as steam pipes), it should be adjusted according to the design value. Generally, the bellows spacing is measured with a micrometer. After doing this, slowly increase the pressure and temperature, and observe if there are any leakages. Don't be at full load as soon as you come up. Run in low-pressure conditions for 30 minutes first, and then rise again if there is no abnormality.
Finally, let's avoid a few pits for you:
- Don't use the expansion joint as a pipeline support, it only compensates for displacement without force, and a guide bracket must be set beside it. If you are lazy and don't install it, the pipe's own weight can deform the expansion joint.
- The skin of the non-metallic expansion joint is easily burned by welding slag, so it is necessary to take precautions when welding and cover it with fireproof cloth. If it isDesulfurization flue gas baffle doorBecause the medium is highly corrosive, it is recommended that the material be upgraded toPTFE-lined hoseOrPTFE compensator。
- If you are not sure which connection method to choose, just flip through this siteCorrugated expansion joint for power plant industryAndMetal Corrugated Expansion Joints in Cement IndustryCase, just follow it. Don't think about it for yourself. Predecessors have stepped on more pits than you have traveled.