Step 1: Find out the temper of your flue first-don't leak temperature, pressure and medium
When choosing flue canvas expansion joint, the most afraid thing is to pat your head. Two days ago, a customer called in a hurry, saying that he couldn't install it after buying it. After asking, he found out that the actual temperature in the flue could reach 600℃, and the maximum temperature resistance of the ordinary canvas expansion joint he bought was only 200℃. Isn't this a waste of money? So the first step is to find out the "details" of the flue:
- Temperature:The continuous operating temperature and instantaneous peak temperature should be written down. For example, the temperature of desulfurization flue of power plant may only be about 80℃, but the flue of cement kiln tail can soar above 400℃. The temperature determines what material is used for the canvas layer-silicone cloth, fluorine cloth or ceramic fiber cloth.
- Pressure:Positive or negative pressure? Approximately how many kPa? If the pressure is not large, ordinary fabric layer is generally used. If the pressure is high, steel wire rings or reinforcing ribs must be lined.
- Media:Are there acidic gases in the smoke (SO₂, NO₂)? Are there any dust particles? In the case of strong corrosion, PTFE or corrosion-resistant coating should be selected. Dusty, the inner layer should be wear-resistant.
Write down these parameters, and then compare them with the specification table of "Non-metallic Expansion Joints (Fabric Fiber Expansion Joints)" on this site, and you can basically lock the materials used. And guess what? Many people find it troublesome, so they buy the general model directly. As a result, it is leaked in half a year, which is not worth the loss.
Step 2: Measure and shape – rectangle or circle? How to match the flange interface?
The parameters are clear, and the next step is the size. Take a tape measure and measure the outer diameter or length and width of the flue interface. Note:Is it to measure the outer edge of the flange or the inner diameter of the pipe?This has to do with the way the expansion joints are connected. There are two common ways to connect:
- Flanged connection:You need to provide the bore diameter, hole spacing, bolt specifications of the flange. The "rectangular non-metallic expansion joint" and "circular baffle door" of this station are equipped with standard flanges, but if yours is a non-standard flange, you have to say in advance that you should be equipped with drilling holes.
- Socket connection:Some flues are directly fitted, leaving an allowance for the size.
Simple shape-choose circle if the pipe is round, and rectangle if it is square. But there is a pit: the flue is obviously square, but the expansion joint is bought into a round shape. As a result, the flange doesn't match, and it has to be returned and replaced. Alas, don't make such low-level mistakes.
Plus, length is critical. The installation length of the flue canvas expansion joint determines its amount of compensation. Generally speaking, you have to calculate how much displacement you need to reserve per 10 meters of pipe. If it is not accurate, you can refer to the question and answer of "Expansion Joint Model and Size" on this site, which has common specifications.
Step 3: Checklist before installation-Don't rush to the wall, do these few things first
When things arrive, don't unpack them directly and go to the flue. Confirm whether the model, specification and connection size are consistent by comparing the invoice and the physical object. Then check the appearance:
- Is the canvas layer broken, bulging, degummed?
- Is there any scratch or deformation on the flange surface?
- Are the bolt holes aligned?
- If you have a tie rod or limit screw, see if they are in the factory preset position (some expansion joints have the tie rod locked at the factory and should be loosened after installation).
The inner lining of non-metallic expansion joints (such as PTFE) must not be creased, otherwise it will easily tear during operation. You don't want to leak as soon as you put it on, do you?
Step 4: Get Installed-Step by Step From Hoisting to Bolt Tightening
Installation is actually not complicated, but pay attention to the order. Take the flange connection as an example:
- Hoisting and positioning:Use a sling or hoist to lift the expansion joint to the installation position. Be careful not to strangle the canvas directly with wire rope, which will make marks.
- Centering flange:First align one side flange with the pipe flange, thread a few bolts, do not screw to death. Then adjust the position of the other side to ensure that the expansion joint is not twisted.
- Fastening Bolts:That's the key. Don't screw one bolt at a time.Diagonal alternating tightening。 For example, for four bolts, first screw the upper left, then the lower right, then the upper right and lower left, and gradually apply force. The reference standard of torque is generally to tighten it half a turn to one turn with a wrench after it can't be twisted by hand.
- Release the limiting device:If the expansion joint leaves the factory with a transport limit screw or tie rod nut, remove or loosen it after installation. Otherwise, it won't be able to stretch freely, which is equivalent to being packed for nothing. You can take a look at the question and answer of "How to adjust the expansion joint tie rod nut" on this site.
If it is installed horizontally, make sure that the expansion joint is adequately supported to prevent sagging. If installed vertically, prevent gravity from stretching the canvas.
Step 5: Keep an eye on these points daily, and the canvas expansion joint will be used for two more years
Put it on doesn't mean it is once and for all. For daily inspection, focus on these places:
- Canvas Surface:Is there any cracking, stiffness, discoloration? These are aging precursors. Especially near the heat source, it is easy to fail early.
- Flange Bolt:Is it loose? The bolts are easy to withdraw under high temperature vibration, so tighten them regularly.
- Displacement Amount:Use a ruler to measure the actual expansion and contraction of the expansion joint to see if it is within the allowable range. If it is found to be stretched too long or pressed too short, there is something wrong with the pipe support or guide.
- Corrosion point:If the medium is corrosive, check for any leakage at the joint between the flange and the canvas. This site has "PTFE-lined hose" and "PTFE compensator". If the corrosion is serious, you can consider replacing it.
If water or dirt accumulates in the flue, clean it regularly so that no debris accumulates in the folds of the expansion joints. Otherwise accelerate wear and tear.
Step 6: When should I change? Just look at these three signals
Flue canvas expansion joint is not a permanent piece, and its life is generally 3-5 years, depending on the working condition. When should I change? Don't wait for it to completely leak before replacing it. Look at these three signals in advance:
- Signal 1:Fine cracks or blisters appear on the surface of the canvas. This is a sign of fatigue aging of materials, and it won't last long.
- Signal 2:Obvious air leak. Can hear a hissing sound, or check for leaks with soapy water. Small leaks can be repaired, but large areas of damage can be replaced directly.
- Signal three:Heavily deformed. For example, the expansion joint is stretched like a lantern, or compressed into a wrinkle, indicating that it has exceeded the design limit and the internal structure may be damaged.
If you find these signals, don't hesitate to change them quickly. After all, flue leakage can affect efficiency at least, and cause safety accidents at worst. Remember to choose the same model or upgraded model when replacing-for example, ordinary canvas was used before, but now it can be replaced with ceramic fiber cloth with higher temperature resistance in the "non-metallic expansion joint" of this site.
Well, after this process goes down, you should have a good idea of the flue canvas expansion joint from selection to replacement. Just do it, no mistake. What are the other questions? Welcome to leave a message, or directly take a look at the "FAQ" and product page of this site, which contains more dry goods.