How to do the lining of high-temperature flue expansion joint? 5-step practical guide, you can judge after reading it yourself

Step 1: Find out whether or not your flue expansion joint needs to be lined-just look at these 3 signals

Don't buy materials and find someone to install them as soon as you come up. Ask yourself first: Does this thing lack lining? To be honest, under many working conditions, the original expansion joints (such as the one in our stationHigh temperature axial expansion jointOrMetal rectangular expansion joint) When you leave the factory, you already have a layer of protection. If you add another layer, it will get in the way.

Then when do you have to add lining? Just look at these three signals:

• Signal 1: The medium temperature exceeds the design upper limit of the metal bellows。 For example, if the flue gas temperature exceeds 600℃, ordinary stainless steel bellows can't hold it for a long time, and will oxidize and embrittle. At this time, the liner is for life-saving.
• Signal 2: The medium is strongly corrosive or has hard particles。 If there is sulfur dioxide, hydrogen chloride in the smoke, or dust particles are ground like sandpaper, the surface of the bellows will be dried through in minutes. Add a layerPTFE-linedOr a ceramic fiber liner, which is equivalent to wearing a body armor on a bellows.
• Signal 3: You find that the expansion joint has appeared local wear, discoloration and air leakage。 Then don't hesitate, quickly add lining or just replace an expansion joint with lining (such as oursNon-metallic expansion joint (fabric fiber expansion joint)OrPTFE-lined hose）。

You see, the signal is that simple. If they all fit, then go down.

Step 2: Choose the lining material, don't follow the trend blindly, and take the seat according to the temperature, medium and pressure (with common collocation)

If you choose the wrong material, it will be white if you install it. Two days ago, I met a customer who lined the desulfurization flue with ordinary rubber. As a result, it was baked into slag in three days. You say it was wrong or not?

Temperature, medium, pressure。 Let me give you a lazy matching table:

• Below 200℃, no corrosion-with a general-purpose rubber liner (e.g.rubber compensatorThe inner lining of). Simple, cheap, and sufficient.
• 200~400℃, with slight corrosion— — UpperPTFE-linedOr PTFE lining (like oursPTFE compensator）。 Enough temperature resistance, first-class corrosion resistance.
• 400-800 DEG C, the flue gas contains particles- -Ceramic fiber/aluminum silicate fiber lining, matchingNon-metallic expansion joint (fabric fiber expansion joint)Use, light and resistant to high temperatures.
• Above 800℃, high pressure or strong wear-directly with a metal liner (such as heat-resistant alloy tiles), or withHigh temperature axial expansion jointThe inner lining structure comes with it, so don't change it yourself.

The liner of positive pressure pipeline should be pressed tightly, and the liner of negative pressure pipeline should be prevented from flattening. To put it bluntly, when you choose materials, report the design pressure and medium flow rate to the manufacturer (such as our family) by the way, and ask them to match you with a suitable thickness. Don't place an order by reading a post on the Internet, and there is no place to cry if you regret it.

Step 3: Before installing the liner, confirm these 4 details in advance to save rework after installation

What are you most afraid of when installing? I am most afraid of finding that the size is wrong, the seal is not tight, or it interferes with other components. When the time comes to dismantle and reinstall, the labor cost is more expensive than the material cost. So before you start, take out your tape measure and drawings and check these 4 points:

• 1. Whether the size of the liner and the diameter of the expansion joint match。 The outer diameter of the liner is 5~10mm smaller than the inner diameter of the expansion joint (leaving space for thermal expansion). If it is too big, it will be stuck directly when the temperature comes up, and the expansion joint can't move. What is it called an expansion joint?
• 2. Should the deflector be kept?Many expansion joints (such asMetal rectangular expansion joint) Bring your own guide tube, and the liner should avoid the installation position of the guide tube, or remove the guide tube first and then install the liner. Don't be stupid, just cover the guide tube, and then the airflow will be turbulent and the wear will be more serious.
• 3. Welding location and process。 If the liner needs to be welded in place (such as a metal liner), be sure to make sure the weld is smooth and burr-free, otherwise these bumps are the abrasive of the future. In addition, do a welding process evaluation before welding, don't burn through the bellows.
• 4. Seals and Pressing Methods。 How to seal the gap between the liner and the pipe? With a gasket or a strip? If it is a flanged connection, check that the flange surface is flat and the bolt holes are aligned. And guess what? Once a buddy failed to correct the hole, and the hole was expanded on the spot. As a result, the flange was deformed and leaked, and it took three days to toss.

Step 4: After installing the liner, do a quick check against these 5 points to ensure that there is no problem

Don't close the flue door in a hurry after installation. First, take the flashlight and wrench, and check it in order:

• Point 1: Appearance-Are there any bulges, wrinkles or damages on the surface of the liner? Especially for non-metallic liners, the fiber layer cannot be torn.
• Point 2: Displacement space— — Manually pull the expansion joint (or simulate the direction of thermal displacement) to see if the liner will get stuck and pulled. If the liner limits the normal expansion and contraction of the bellows, it is equivalent to turning the expansion joint into a rigid connection.
• Point 3: Fastener Torque— — All compression bolts, tie rod nuts (refer to our Q&AHow to adjust the tie rod nut of expansion joint) All have to be screwed to the design torque, don't loosen or too tight.
• Point 4: Sealability— — Use soapy water or smoking agent to check for leaks around flange joints and welds. If there are bubbles or smoke floating out, it means that it is not sealed tightly.
• Point 5: Guide tube centering-If there is a guide tube, the liner cannot cover the outlet of the guide tube, and the flue gas flow must be smooth. Otherwise the local vortex will tear the liner apart.

If these items are fine, you can safely put the system in. Do you feel confident in your heart?

Step 5: Regular maintenance after operation Remember 3 key actions, and the lining life will last at least one year longer

Get it installed, check it out, and you think it's all right? Wrong! The liner is most afraid of "leaving it alone".

Actually, there are three actions for maintenance, which is very simple:

• Action 1: Visual inspection once a quarter— — After shutting down, disassemble the inspection port to see if the liner is discolored, peeled off or partially thinned. Focus on high temperature areas and airflow impact surfaces.
• Action 2: Liner thickness measurement once a year— — Use an ultrasonic thickness gauge or caliper to measure several points at the position where the liner is most prone to wear (such as the back arc of the elbow and near the baffle door). If the thickness wear exceeds 30% of the original value, it is ready to be replaced.
• Action 3: Repair minor damage immediately— Don't wait until it's broken before replacing. The non-metallic lining can be glued with high temperature glue, and the metallic lining can be partially surfaced. Repair it one day early and replace it one year late.

High temperature flue expansion joint liningIs your "second line of defense", protect it, your expansion joint (whether it isCorrugated expansion joint for power station industryStillMetal Corrugated Expansion Joints in Cement Industry) to withstand the thermal expansion and contraction for you. Look, after these 5 steps, can you judge yourself? Next time you encounter problems with flue expansion joints, don't scratch blind again.