Step 1: Find out the "temper" of your original flue-temperature, pressure and corrosiveness are indispensable
Don't be in a hurry to place an order, turn out the drawings at hand first. The original flue of the power plant is no joke. The flue gas temperature is usually between 80 and 180℃, and the operating pressure is either slightly negative pressure or positive pressure. The medium carries corrosive components such as SO₂ and water vapor. Think about it, if you buy the wrong expansion joint and it leaks within two months of installing it, how bad it would be?
Which parameters should I take specifically?
- Flue gas temperature: What's the highest? How long does it last? This determines whether you choose non-metal or metal.
- Operating pressure: The non-metallic expansion joint can completely withstand the slight negative pressure, and the metal joint can be used if the positive pressure is high.
- Media composition: Sulfur-containing gas corrodes metals, but non-metallic fabric fibers are very resistant.
- Sectional shape and dimensions: The original flue is basically rectangular cross-section, so it is likely to be used laterRectangular non-metallic expansion joint。 Take a ruler to measure the length and width, and then find out the direction of displacement-is it axial expansion or lateral misalignment?
Tips: If you don't have drawings on hand, go directly to the scene and take a few photos, and measure the hole spacing of flange bolts. Don't guess by your feeling, otherwise you won't be able to install it when you buy it, and it will be troublesome to return it.
Step 2: How to choose the type? Metallic or non-metallic? The key is corrosion and temperature
The desulfurized flue gas in the original flue has high sulfur content, high humidity and not particularly high temperature (generally not more than 180℃). In this caseNon-metallic expansion joints (fabric fiber expansion joints)Is an absolute mainstream choice. Why? Because of its good corrosion resistance, large compensation, and labor-saving installation-one person can almost move it. The disadvantage is that the life span is shorter, and you have to change it in 3~5 years.
Then when did you use metal? If the flue gas temperature exceeds 200℃, or the pipeline needs to bear pressure (such as positive pressure above 0.1MPa), then you have to go upCorrugated expansion joint for power station industryYeah. Note that the "corrugated expansion joint for power station industry" of this station is specially designed for the working conditions of power stations, lined with anti-corrosion layer, and don't buy it as an ordinary metal corrugated pipe. However, metal is expensive and troublesome to install (it has to be matched by a crane), and once the wrong material is selected (for example, no anti-corrosion lining is made), it will corrode faster than non-metal. How do you choose? Simple:Temperature below 200℃, slight negative pressure, corrosion → rectangular non-metallic expansion joint; High temperature, bearing pressure → corrugated expansion joint for power station industry.
Hey, two days ago, a peer asked me: Can you use a rubber compensator instead? I said don't make trouble, rubber is soft above 80℃, and the original flue is generally more than 100 degrees. Using rubber is to cause trouble for yourself. Our station hasrubber compensator, but that's for room temperature water pipes, don't get confused.
Step 3: Before hands-on installation, deal with these "small details"-guide tube direction, pull rod, pre-compression
I bought something back, so don't rush to fight it up. Look at the direction of the arrow on the product first!Specific Function of Expansion Joint Guide TubeIt is to guide the flow direction of the medium and reduce the vortex wear, and the arrow must be consistent with the flow direction of the medium. Install backwards? Just wait for the ripples to fray.
Furthermore, don't rush to dismantle the tie rod. Many people make this mistake-they loosen the tie rod nut when they get it, and as a result, the expansion joint bounces open at once, and the back can't be installed. The correct way to do this is to follow the FAQ"How to adjust the tie rod nut of the expansion joint"In the steps, first pre-compress to the design value (generally marked when leaving the factory), then put the expansion joint in the middle of the flange, and then install the bolts. How to screw the bolts? Pre-tighten diagonally and twist to the specified torque two or three times. Don't screw to death once, otherwise the flange will deform and leak.
attention: If yesCorrugated expansion joint for power station industryRemember to check whether the lining anti-corrosion layer is damaged, and the guide tube must be welded firmly. If it isRectangular non-metallic expansion jointTake a closer look at whether the fabric layer has scratches and blisters. If so, go directly to the manufacturer to change it. Don't feel bad about the construction period of those days.
Step 4: Install the flapper door? Don't let the expansion joints "fight"
The original flue system is usually equipped withFlue gas baffle door(For example, this site'sDesulfurization flue gas baffle doorOrRound Flap Door (Double Seal)、Single-axis double-flapper door）。 The installation distance between the expansion joint and the baffle door should be at least 200mm. Why? Because both will displace during thermal expansion and contraction, leaving enough space to not squeeze each other. And guess what? Last week a client putCorrugated expansion joint for power plant industryIt was installed in the opposite direction, close to the baffle door. As a result, as soon as the temperature rose, the expansion joint directly stood against the baffle door, and the door could not be closed in place. Finally, it was disassembled and reinstalled, and a day's work was wasted.
First install the baffle door, fix the position, then install the expansion joint, and finally connect the pipeline. If the site space is really limited, you can useCompound hinge transverse expansion jointTo absorb multi-directional displacement, this thing can flex and stretch, suitable for narrow areas.
Step 5: There are three points for daily maintenance-see, listen and touch
It's done after installing it, and you still have to raise it. Remember three words: see, hear, and touch.
- look：Rectangular non-metallic expansion jointIs there any blistering, delamination, and hard surface?Corrugated expansion joint for power station industryIs there any crack or rust in the bellows? Has the deflector been worn out?
- Listen: Get close to the expansion joint and listen for a hissing air leak. If there are words, it means that the seal has failed, so stop the machine for inspection quickly.
- Touch: Use the back of your hand close to the surface (don't stick it directly, be careful of burning) to feel whether the temperature is abnormally high. Local overheating may be caused by internal blockage or biased medium flow.
Non-metallic expansion joints are checked every six months, and metallic ones can be checked once a year. If you find a leak, don't repair it with a welder yourself-the non-metallic one can only be replaced as a whole, and the metallic one can be replaced with the corrugated section (provided that you buy accessories from the original factory). In addition,Service life of expansion jointRefer to the question and answer of this site: about 5 years for non-metals and about 10 years for metals. When the deadline reaches, stock up in advance. Don't wait for it to be broken before buying it. Have you calculated how much electricity bill you will lose when you shut down for a day?
Well, after these five steps, you should have a spectrum in your heart for the selection, installation and maintenance of the original flue expansion joint. If you are still unsure, directly flip through the product information of this site, such asHigh temperature axial expansion joint、Straight pipe pressure balanced expansion jointThese special models are also described in detail for special working conditions. Remember: Choose the right, install the right, and raise the right, so that the expansion joint can serve you honestly for several years.