Flue Inlet Expansion Joint Replacement? Follow these 5 steps, save trouble and reliable

1. Before replacing, these preparations can save you half the detour

To be honest, the position of the flue inlet expansion joint is usually the "weak link" of the whole flue gas system-high temperature, corrosion and vibration, which occupy all three things. If you dismantle it directly, you will probably have to rework it. What about that? Make the preparations solid first.

Step 1: Shutdown, listing, and confirming safety.Don't be too long-winded. The residual flue gas in the flue gas system may be toxic (such as sulfur dioxide), so it must wait until the system is completely cooled and the ventilation is replaced. Get an electrician to put an electric valve related to the expansion joint (e.g.Electric plug-in insulation doorOrFlue gas baffle door) Turn off the power and hang up the "Manned Work" sign.

Step 2: Measure and take photos.Take out the tape measure and write down the flange spacing, the center distance of the bolt hole and the diameter of the bolt hole of the old expansion joint. It's best to take a few panoramas and close-ups with your mobile phone-in case you can't select the model later, you can also let the manufacturer look at the pictures and give suggestions. Don't ask me how I know. I met a customer two days ago. Only after dismantling did I find that the size was wrong. I just waited for three days for the goods.

Step 3: Prepare all tools and materials.Wrenches, crowbars, lifting hoists (some expansion joints are quite heavy, such asMetal rectangular expansion jointOrLarge diameter thick wall expansion joint), sealing gaskets, new bolts and nuts, torque wrenches. By the way, if you're replacingNon-metallic expansion joint (fabric fiber expansion joint)Don't forget to bring a utility knife and a beading tool.

Confirm the weight of the expansion joint with the manufacturer in advance. Don't lift it by hand. It is no joke to hit your foot.

Second, dismantle the old expansion joint, don't force it, first get these three details

Old expansion joints are often pasted to death by soot and corrosive materials. You want to hard-pry? There is a high probability that the flange surface will be damaged, and the new parts at the back will leak when installed. So pay attention to these three points when dismantling:

• Remove the pull rod or limit first.Many expansion joints have tie rods (e.g.Large tie rod expansion jointOrUniversal corrugated expansion joint), you have to loosen these screws first, but don't disassemble them all-leave two diagonal bolts to prevent the expansion joint from suddenly bouncing off and hurting people. Then remove the remaining bolts one by one. For how to adjust the tie rod nut, you can refer to the content previously talked about in our station.
• Clean up surrounding dust.Use a blade or vacuum cleaner to remove smoke and rust from the flange surface. If it is not cleaned, the new sealing gasket will not be compressed firmly, and it will definitely leak air in the future. And guess what? Many people ignore this step. As a result, the smoke leaked out during the trial operation, and they had to be disassembled and reinstalled.
• Check the flange surface for any deformation.Old metal rectangular expansion joints orRectangular non-metallic expansion jointIf it runs for a long time, the flange may warp due to thermal stress. If the deformation is serious, you have to consider replacing the flange or trimming it on site. Don't put the new piece directly on the deformation flange, it's wasting your effort.

Third, choose a new expansion joint: metal rectangle or non-metal? Determine according to the working conditions

This step is the easiest to struggle with. In fact, the judgment standard is very simple. Just ask yourself three questions:

1. What is the flue temperature?If the continuous temperature exceeds 400℃, basically you can only selectMetal rectangular expansion jointOrHigh temperature axial expansion joint。 If the temperature is below 200°C,Non-metallic expansion joint (fabric fiber expansion joint)evenrubber compensatorThey are competent, and the vibration isolation and sound muffling effects of non-metals are better.

2. Are there any corrosive media?The wet flue gas after desulfurization contains sulfur and chlorine, which is very corrosive. At this timeNon-metallic expansion joint(EspeciallyRectangular non-metallic expansion joint) orPTFE-lined hoseClass products are more resistant to corrosion. Don't use ordinary stainless steel bellows, which will wear you in a few months.

3. Is the displacement that needs to be compensated large?If that amount of thermal expansion of the pipe is large,Compound hinge transverse expansion jointOrCurved tube pressure balance expansion jointCan absorb multi-dimensional displacements. However, if you only replace the inlet expansion joint partially, it is usually enough to choose the single axial type or the general-purpose type-the specific size can be checked according to the expansion joint model and size table in our station.

Selection is a technical job. If you are really unsure, measure the parameters and send them to the manufacturer. Don't pat your head. After all, aMetal rectangular expansion jointIt is not cheap to replace it, and it is more troubling to buy the wrong one.

4. Install the new expansion joint, and one step of positioning, centering and tightening is indispensable

I got the new piece, so don't rush to attack the flange. In this order:

Step 1: Hoist and position.Use a hoist or crane to lift the new expansion joint to the installation position and gently place the flange surface. Pay attention to the direction of the arrow on the expansion joint-we talked about it earlier,The direction of the arrow of the expansion joint refers toThe medium flow direction, don't install it backwards, otherwise the guide tube will become a resistance or even cause the bellows to be damaged.

Step 2: Alignment adjustment.Use a ruler or level to check that the expansion joint is aligned with the flue centerline. If the deviation exceeds 2mm, you have to adjust the gasket or move the position. EspeciallyMetal rectangular expansion jointThe flange is very rigid, and if you tighten the bolts correctly, you will sprain the bellows.

Step 3: Tighten the bolts.First put on all the bolts by hand, then tighten them with a torque wrench in diagonal order in fractional intervals. Don't screw to death all at once! Gradually add to the prescribed torque in three times. If it isNon-metallic expansion jointThe tightening strength of the strips and bolts should be uniform, and do not tighten and loosen at the same time, otherwise the fabric layer is easy to wrinkle and leak. Does the screw on the expansion joint need to be disassembled? Note: After installation, if the expansion joint has a temporary limit screw for transport, remember to remove (or at least loosen) it, otherwise the expansion joint will not work properly.

5. Do a comprehensive inspection before trial operation to avoid rework

Don't rush to light the fire when it's finished. Spending half an hour doing these things can save the next three days of rectification time:

• Review bolt torque.I just screwed it in separate times, and confirm again whether all the bolts have reached the specified torque. Loose bolts come off more quickly during vibration.
• Check the seal.If you can see the flange gap, measure it with a gauge; If the sealing gasket is exposed, it should be even. ForNon-metallic expansion jointAlso check the fabric for wrinkles or scratches.
• Check the surrounding lines.The expansion joint is replaced, are there any other pipe supports nearby that have been displaced? Is there a flapper door (likeDesulfurization flue gas baffle doorOrSingle-axis double-flapper door)' s trip is blocked by new pieces? By the way, manually try to see if the baffle door opens and closes smoothly.
• No-load trial run.Let the system run at low temperature for a while (such as 50℃) to check for air leakage and abnormal noise. After confirming that there is no problem, gradually raise the temperature to the working temperature. After the working temperature is raised, stop the machine and check the bolts again-the bolts may loosen after thermal expansion and need to be tightened again.

After the whole process goes down, the replacement of the flue inlet expansion joint is actually not so mysterious. It is nothing more than full preparation, careful disassembly and assembly, reasonable selection and inspection in place. Is that the truth? If you follow these five steps, you won't overturn. If you encounter something unsure in the actual operation, feel free to look through the product information on our site, such asMetal rectangular expansion joint、Non-metallic expansion jointThose pages, parameters and installation precautions are clearly written.