Let's start by talking about how important the skin is
Don't look at it as a layer of soft connection. In the flue system, if you don't have it or install it incorrectly, the stress, vibration and leakage of thermal expansion and contraction will make your head big in minutes. The rectangular non-metallic expansion joints and non-metallic expansion joints (fabric fiber expansion joints) on our station rely on this layer of skin to absorb displacement and seal. And guess what? Many masters tried to save trouble when they installed it, but as a result, it cracked and leaked within half a year, and the money had to be stopped for change. So before installing, you have to make it clear that this skin is not just tied up and done.
One is to compensate the thermal displacement of the pipeline, and the other is to seal the flue gas in the pipeline. If it is not installed well, for example, if the strip is pressed too tightly, the skin will be marked, or if it is stretched too tightly without leaving a thermal expansion margin, the high-temperature smoke will tear directly as soon as it comes up. Who do you think takes the blame?
Many people don't take the steps of preparation before the start of construction seriously
Let's see if the flange surface is flat first. Take the ruler against it. If there is deformation or welding slag in the flange, fix it with an angle grinder. Don't be lazy. If the flange surface is uneven, the pressure on the skin will be unevenly stressed, and the gap will leak sooner or later.
Then check whether the skin material is correct-the high-temperature flue must be a temperature-resistant layer, and the corrosive medium must be lined with fluororubber or PTFE compensator. For example, the desulfurization flue contains sulfide, and the ordinary fabric fiber skin can't last for three months, so it must be lined with PTFE. If the smoke baffle door on your side is also linked, you have to consider the installation sequence. Don't leave the gap between the skin and the baffle door small-if the gap is not enough, the skin will be scratched when the baffle door is opened and closed, and it will be scrapped directly.
In addition, are the bolts, strips and sealants all ready? Don't miss this or that halfway through. Especially sealant, many on-site pictures save trouble with ordinary glass glue, which melts as soon as it heats up and bakes, so it's better not to hit it.
Start to install, the most critical details: how to tighten the strips and bolts
Most people twist to death when they come up, and as a result, the skin is strangled with marks, and it cracks from the strangulation mark in the later stage. The correct way is to pre-tighten the diagonal gradually and add it to the specified torque in three passes. Up to 30% torque on the first pass, 60% on the second pass, and 100% on the third pass. Don't bother, it's the same as an engine head bolt.
There is also a pit-the skin should not be stretched too tightly, and there has to be a margin for thermal expansion. The lateral displacement of the rectangular non-metallic expansion joint may reach tens of millimeters at high temperature. If you pull the skin as flat as the drum head, it will tear directly as soon as the temperature rises. How to leave an allowance? When installing, let the skin sag a little naturally, or according to the pre-stretch/pre-compression data given by the manufacturer.
If you are installing a rectangular expansion joint, pay special attention to the position of the four corners. The arc should be smooth and the folds should be flattened, otherwise the first bad thing about stress concentration is the corner. Many rollover cases are that the corners are not handled properly, and the holes are torn from the corners after less than a month of operation.
Don't be in a hurry to finish the work after installation, you have to do an airtightness check
Spray the bolt holes and skin overlap with soapy water. If there are bubbles coming out, it means that the seal is not tight, and you have to refill or re-tighten it. Don't believe what "it feels like it doesn't leak when you touch it with your hands"-the smoke is high pressure and can't be touched by your hands.
In addition, check whether the guide tube is in the right position. The function of the guide tube is to guide the airflow to the center of the pipe, so as to avoid directly washing the inner wall of the skin. If it is skewed, the airflow will hit the skin directly, and its life will be greatly reduced. If this flue is also equipped with a smoke baffle door or an electric plug-in insulation door, remember to close the door to full open position before doing the test, and don't let the door blades scratch the skin. After closing the door, the edge of the door panel may deform the skin top, which is a false leak.
Finally, talk about a few common rollover cases on the spot
Someone has reversed the direction of the skin installation-the direction of the arrow marked by the manufacturer refers to the direction of the medium flow. If the skin is installed backwards, it will rotten within two months. It is common sense that the direction of the arrow must be consistent with the direction of the smoke flow, but there are people at the scene who don't look.
Others have too hard skin when installing in winter, and hard breaking causes the inner layer to break. At that time, it couldn't be seen, but it was exposed as soon as it heated up-the smoke came out of the crack, and the whole sealing layer became a "jet". Solution? Heat it slightly with a hot air fan and reinstall it, which is much more flexible. Or put the skin in a warm warehouse overnight in advance, and don't work directly in the open air at minus ten degrees.
After all, skin installation is a meticulous job. You plan for a while, and the maintenance work order at the back is enough for you to fill in for a year. Choosing the right product is equally important. The rectangular non-metallic expansion joints and fabric fiber expansion joints on our station are pre-opened and marked according to the standard, so you can't go wrong with them. If you are really unsure, flip through the installation instructions in the product manual, or call technical support directly to ask. Don't think about it yourself, the time saved is not enough to rework a downtime loss.