Let's break a data first
The expansion joint of the desulfurization flue of a power plant leaked after 3 months of hot operation because the sealing surface was not cleaned when the skin was installed, and it was directly shut down for emergency repair, resulting in a loss of less than 2 million yuan. In fact, 90% of leakage faults are buried in the installation stage-either the screws are not evenly tightened, or the skin overlap direction is reversed. You spent thousands to buy imported fluororubber skin, but it cracked after installing it for half a year. Do you feel distressed? Therefore, the installation is really not just a few workers to do it according to the video.
Material selection is the first step and the easiest step to roll over
The flue medium temperature fluctuates greatly, from normal temperature to 350℃ or even higher, and dew condensation and corrosion will occur below the acid dew point. Don't expect one skin to take all conditions. For example, the original flue gas section at the inlet of the desulfurization tower, with a temperature of 160 °C + and a high concentration of SO₂, must be coated with a composite skin reinforced by tetrafluoroethylene (PTFE) interlayer + glass fiber cloth, with a thickness of at least 3 mm; However, the temperature of the net flue gas section is low, but the wet corrosion is strong, and the silica gel-based skin can bear it more. In terms of pressure, generally, the positive pressure does not exceed 5kPa. Just leave 1.5 times the safety margin when selecting the type. Don't blindly thicken it-if it is too thick, the flexibility will be poor, and the extrusion stress will be large.
Preparation work before installation, to put it bluntly, three words: clear, flat and dry
The old residual glue, welding slag and rust skin on the flange surface must be shoveled clean and polished with an angle grinder +100 impeller until the metallic luster is exposed. Check the unevenness with a ruler. If the gap exceeds 1mm, it has to be welded or polished. Otherwise, the local stress of the skin will be concentrated after compression, and it will be perforated in a few months. Clean sealing surfaces also have to be degreased – wipe them twice with acetone and let them dry for 30 minutes. Don't use gasoline to save trouble, the residual oil film will corrode the rubber. Another point that is easy to overlook: the chamfered burr at the edge of the flange bolt hole, which will cut the skin if left untreated.
The installation steps look simple, but the practical pit is the most
Put the skin flat on the flange first, and pay attention to the flow direction marks-the arrow must point in the direction of the airflow, and the lap should be downwind, and the upwind will be blown up. After the bar is placed, the bolt tightening sequence is served: pre-tighten diagonally from the middle to both ends, and hit to the final value with a torque wrench three times. How much torque? Look at the value given by the skin manufacturer. Generally, M12 bolts are 50-70N·m, but don't die on the numbers-screw the same bolt three times, with an interval of 15 minutes for each pass, so that the skin stress is released. You tighten it all in one breath, and as soon as the hot state expands, the middle of the skin bulges, the bolts are loose, and it dries for nothing.
Two days ago, a customer told me that they leaked after two months of installation
I said you should check it-it is probably that the strips are deformed or the bolts are not tightened again. The flue is hot and cold alternately, and the bolt will relax after thermal expansion. It must be tightened again immediately after the first temperature is raised to the working temperature and before the machine is stopped to cool down. Another classic mistake: skin folds. If the skin is too tight or too loose during installation, it will be deflated under hot state or by wind pressure. The correct way is to leave 2% ~3% of the pre-relaxation amount at room temperature and flatten it by pressing strips. Remember one principle: the working state of the skin is tension, not compression, and don't let any position buckle when installing.
Acceptance cannot be checked alone
After installation, spray soapy water on the flange joint, fill the air side with 0.02MPa compressed air, and observe that there is no bubble for 1 minute. More specific practice: infrared thermal imaging is used for hot state detection. After the temperature is booted up to the design temperature, it is scanned point by point, and the place where the temperature difference exceeds 5℃ is directly marked for rework. Daily maintenance depends on two indicators: one is that the fixing bolts are no longer loose, and the other is that there is no bulging or cracking on the skin surface. Under normal working conditions, the life of fluororubber skin is 3~5 years, and that of silicone skin is 2~3 years. If you pretend to be particular, it will be fine to last for two more years; Blind installation will have to be dismantled in half a year-you calculate the artificial materials, which one loses more?