Don't rush it yet-find out what kind of expansion joint you are facing
There are only two types of expansion joints in the flue:Non-metallic expansion joint (fabric fiber expansion joint)AndMetal rectangular expansion joint。 Non-metal is light, one person can move it, and there are few flange bolts, but there is a problem: flange bolts are easy to rust, especially in the flue gas environment after wet desulfurization. The metal ones are much heavier, such as those used in the power station industryCorrugated expansion joint for power station industryOr one of thoseLarge-diameter thick-walled expansion joints, one piece alone weighs several hundred kilograms, and you have to use a sling or even a forklift. Two days ago, a customer called and said that he dismantled the non-metallic expansion joint as metal, and took a crowbar to save trouble. As a result, the fabric layer was torn to pieces, which cost him a waste of money. So before you start, look down at the nameplate, or take a photo and send it to the manufacturer (such as us) to confirm, which is better than tearing it down.
You can save half of your effort when you do enough preparations
Make sure the flue is out of service and the temperature has dropped to normal temperature-don't do it at high temperatures, because the residual stress of the expansion joint will injure people. I have seen a master who was in a hurry and went to dismantle the unit as soon as it stopped. As a result, the thermal stress in the metal bellows was released at once, and the bolts collapsed, almost hitting his eyes. So this step really can't be saved. Then close the baffle door to cut off the upstream and downstream. The flapper doors here could beFlue gas baffle doorOrManual plug-in insulation doorIf conditions permit, it is best to add a lock card after the closure dies. Tool list: hydraulic wrench, crowbar, sander (handles corroded bolts), sling (essential for metal parts), loosening agent, dust mask. Safety first, don't skip this step.
The disassembly steps are divided into four steps
Remove the insulation around the expansion joint and the guide tube (if any). We talked about the function of the deflector before in the question and answer. It protects the bellows from being washed by high-speed dust, but it often hinders the disassembly of flange bolts when disassembled, so remove them first. Step 2: Loosen the tie rod nut. Note: If you do not plan to replace new parts, do not disassemble the pull rod completely, and mark the position first to prevent displacement. How to adjust the specific tie rod nut, please refer to our previous Q&A (How to adjust the tie rod nut of the expansion joint), the principle is the same. Step 3: Disassemble bolts one by one along the flange – starting diagonally to prevent deformation caused by stress release on one side. Non-metallic bolts are easy to handle. If metallic bolts rust to death, spray loosening agent first and try again after half an hour. Step 4: Use a crowbar to disengage the expansion joint as a whole or in sections. If it isCompound hinge transverse expansion jointPay attention to the direction of the hinge and don't pull it hard. Its hinge is fixed and can only swing in a specific direction. Deadpull will break the hinge fastener.
The easiest pit to step on when dismantling
Three pits, one of them is enough for you.
① Don't smash the bolts hard if they are rusty.Soak in loosening agent for half an hour, or bake in oxyacetylene (fire cannot be used for non-metallic pieces, as the fabric layer is flammable). If you still can't twist it after baking, then use a sander to grind off the nut and replace it with a new bolt.
② Ash and scale may accumulate inside the metal expansion joint.Especially after the long-term operation of the unit, the ash in the flue will be deposited in the bellows trough. Disassemble the instant dust and choke people, and prepare a dust mask. Once I didn't wear it, ash poured directly into my throat and coughed for a week.
③ The fiber material is fragile after the non-metal expansion joint is removed.Don't let it fall into the flue during recovery, otherwise it will block the downstreamFlue gas baffle doorOrDouble-sealed single-axis circular baffle door。 Use a large garbage bag to cover and remove, and seal it directly after removing.
After removing it, it doesn't mean it's done
Vintage inspection is the main event. See the bellows for cracks, corrosion perforations-especially forUniversal corrugated expansion jointOrExternal pressure single axial expansion jointThe corrugated pipes of these two types of products are directly in contact with flue gas, and the corrosion is the most serious. Non-metallic depends on the aging degree of the fabric layer. If you rub it with your hands, the powder will fall off, which means that it should be changed. If only the sealing surface is worn, you can only change the sealing gasket; If the corrugation fails, replace it with a new one directly. There are corresponding product models to choose from on our website, such asRectangular non-metallic expansion jointOrHigh temperature axial expansion jointIt is fine to adapt gas, hot air and boiler flue. If you are not sure yourself, take a photo and send it to us to help judge-we can know at a glance after taking the end face, flange bolt hole distance and bellows thickness. Remember, don't just look at the outside. Some internal cracks are invisible to the naked eye. Use hydraulic test or coloring to detect flaws.
Finally, let's be honest
Flue built-in expansion joint removal is not routine, once or twice a year at most. If you are not a professional maintenance team, it is recommended not to act recklessly-especially in the high-temperature and high-pressure flue gas system. Once the expansion joint is installed in the wrong direction or the seal is not done well, it will leak when the machine is started. If you have disassembled it and want to install it yourself, don't forget to relock the tie rod and pre-stretch it. For specific operation, please refer to our previous Q&A "Correct Installation Method of Large Tie Rod Expansion Joint". When installing, pay attention to the direction of the guide tube must flow towards the medium, otherwise the fluid will directly flush the bellows, and the life will be directly reduced by half. In addition, the selection of flange gasket is also particular. Ceramic fiber pads are commonly used for non-metallic expansion joints, and graphite winding pads are used for metal expansion joints. These things seem small, but if they leak, they are all dry for nothing.
Tsk, after saying so much, it is actually a sentence: find out the type, do a good job of protection, dismantle it according to the process, and decide whether to replace it or repair it after dismantling and inspecting it. If you are unsure, feel free to contact us-anyway, we have sold expansion joints for so many years, and there are drawings, models and installation videos, which is better than worrying about rusty bolts alone.