From selection to installation of catalytic flue expansion joint: 5 steps to get high temperature flue compensation
The catalytic flue is no joke. The temperature is always five or six hundred degrees, the flue gas carries sulfur and catalyst dust, and the pressure is still high and low. If you buy an ordinary expansion joint at random, it will leak in three months. When the time comes, it will be stopped and replaced, and the loss will be enough for you to buy several good sets. What about that? Don't worry, follow these five steps, and your catalytic flue expansion energy saving will run steadily for three to five years.
Step 1: Find out how "ruthless" the working conditions you encounter are first
Your catalytic flue, is it running for a long period or intermittently? Is the temperature 450℃ or 680℃? That's a big difference. I have seen a customer who marked 400℃ on the drawing. After actual measurement, the peak value rushed to 650℃, and as a result, the metal expansion joint directly creeped and failed.
So in the first step, you have to find out the temperature, pressure, displacement and corrosion components of the medium at the site. It is best to flip through the design drawings, or look for the process for data-what is the temperature? Axial displacement or lateral displacement? Is there any acidic condensate? These directly determine whether you should choose a metal expansion joint or a non-metal expansion joint.
Don't forget to look for wet sulfur in the smoke. If the flue gas temperature drops below the dew point after desulfurization, there will be condensed acid, and ordinary stainless steel 316L can't withstand chloride ion stress corrosion. That's when you have to consider the non-metallic scheme.
Step 2: Don't just look at the price when selecting a model, but look at the "physique"
Now that the working conditions are clear, then take the right seat. If the flue temperature exceeds 400℃, our first choiceHigh temperature axial expansion jointOrCorrugated expansion joint for power station industry— — These two models are high-temperature resistant, and the corrugated pipe material is stainless steel 316L or Incoloy 800, which can hold up. If the flue gas is high in sulfur and there is a risk of condensation, it must be consideredNon-metallic expansion joint (fabric fiber expansion joint)OrRectangular non-metallic expansion jointThey are corrosion resistant, are not afraid of condensing acid, and can compensate for multi-directional displacement.
Don't use metal expansion joints in an environment with wet sulfur smoke, otherwise chloride ion stress corrosion cracking is waiting for you. Alas, two days ago, a colleague complained to me that they bought ordinary metal for cheap, but it cracked in half a year, and it was corroded. Do you think it's a loss or not?
If space is limited and lateral compensation is required, you can look atCompound hinge transverse expansion jointOrCurved tube pressure balance expansion joint。 These two can handle large lateral displacements without taking up too much space.
Step 3: Don't be in a hurry after the goods arrive, and do these things
Expansion joint to the site, first unpack to check the appearance. See if there are any shipping bumps that cause bellows to deform or non-metal layers to break. Then check the model and size-is the "high temperature axial expansion joint DN800" you ordered right for the flange? Look if the design temperature, pressure and displacement on the label are consistent with your working conditions.
Be sure not to remove the transport screws (that is, those that limit displacement) before installation. Otherwise, the expansion joint will expand and contract itself during the hoisting process, which is easy to be damaged. How to deal with it specifically? You can refer to the method in our FAQ-keep the screw locked before installation, and then loosen and adjust after the pipe is aligned.
Before installation, adjust the deviation of the pipe, and don't use the expansion joint to forcibly correct the deviation-it is only responsible for compensating the thermal displacement, not used as a wrench. I have seen this mistake too many times. It was hard screwed on, and it leaked within two months.
Step 4: When installing, these details determine the lifespan
Install the fixing bracket and guide bracket first. The fixed bracket should be welded to the pipe, and the position is determined according to the design drawing, usually at both ends of the expansion joint. The guide bracket ensures that the pipe can only move in the axial direction and cannot deviate. Then hoist the expansion joint, and the bolts should be symmetrically tightened when the flange is butted, twice or three times to the specified torque.
If it is a non-metallic expansion joint, the flange surface must be cleaned and the gasket placed straight to prevent air leakage. The most common mistake in this step is that the expansion joint is installed between the two fixed brackets, and as a result, it can't be expanded or retracted at all. The correct way to do it is: one end is fixed, the other end is free, and the middle is used with a guide bracket. Regarding the adjustment of the tie rod nut, you can refer to the method in our FAQ-loosen the tie rod nut to half of the designed displacement during installation, leaving a thermal expansion margin.
Also, don't forget to check the matchingFlue gas baffle doorOrDesulfurization flue gas baffle doorThey also have to be installed in place together, and the moving parts should be coated with anti-jamming agent to prevent rust death later.
Step 5: How to manage after running? Don't wait for a leak to fix it
See if there is any abnormal noise, vibration, flange leak? Check the weld and bellows surface with soapy water or a leak detector. If you find that the fabric layer of non-metallic expansion joint is damaged, discolored or bulging, stop the machine quickly and replace it. Don't drag it.
The metal expansion joint should pay attention to whether there is dust accumulation at the root of the bellows, and the corrosiveness of the dust will double after absorbing water. In addition, the matching smoke baffle door should also be moved regularly to prevent sticking. Two days ago, I met a customer. The non-metallic expansion joint of their catalytic device was not inspected for two years. As a result, the fabric layer was worn out by catalyst dust, and the whole flue smoked. Alas, if you had done a quarterly cosmetic inspection, you wouldn't have had this problem.
Choose the right type, install the right position, and check frequently, and your catalytic flue expansion energy saving will run steadily for three to five years. Is that the truth? Feel free to chat about your experience in the comments section!