How to choose and install wet desulfurization flue expansion joint? Teach you 5 steps to avoid pits
To be honest, all the brothers who have worked on desulfurization projects know that the flue expansion joint looks inconspicuous. Once something goes wrong, it really leaks and pulps, and it takes two days to shut down for emergency repair. Two days ago, another customer called me and told me that the expansion joint at the outlet of the desulfurization tower they just installed tore in less than three months. When I asked, good guy, the selection was completely guessing, and the tie rod was not even adjusted when it was installed. How injustly do you say the money was spent?
I'll talk to you todayWet desulfurization flue expansion jointHow to choose and how to install. If you don't talk, go directly to the dry goods. After five steps, you will be sure to step less than half the pit.
Step 1: Find out how "toxic" your flue is-first find out the working condition parameters
Before choosing the expansion joint, the first thing is not to turn the sample, but to go to the site to find out the working condition parameters. To put it bluntly, you have to know how "poisonous" your flue is.
TemperatureIs the most basic. The net flue gas temperature after wet desulfurization is generally 45~60℃, but don't think that this is over-if there is no GGH installed in front, or there is bypass flue mixing, the temperature may instantly rush above 120℃. The non-metallic expansion joint you choose at room temperature will have to burn through at once.
pressureWhat? The outlet of the desulfurization tower is usually negative pressure, but positive pressure shock may occur when the fan fluctuates or starts and stops. Not stressed? That's not necessarily the case. Some systems also have booster fans, with positive and negative pressures alternating. If the expansion joint is not designed with sufficient rigidity, it will be deflated at once.
Media compositionEven worse. The flue gas after wet desulfurization contains a large amount of water vapor, SO₂, SO₃ and chloride, and slurry droplets will also be brought out. The pH value is as low as 2~3, which is extremely corrosive. If you choose regular carbon steel bellows, that's equivalent to loading a ticking time bomb into the flue.
displacement amountDon't ignore it either. What is the axial and lateral displacement of flue due to thermal expansion and contraction? Are there any dead spots in the direction of the pipeline? You'd better measure this data with a ruler, or let the design institute give it to you. When he was unsure, he would rather choose a bigger compensation amount than to cause trouble for himself just to save a few hundred dollars.
After obtaining the working condition parameters, compare the materials such as Corrugated Expansion Joints for Power Station Industry and Metal Corrugated Expansion Joints for Cement Industry on the product page of our website, and first frame a rough temperature and pressure resistance range. Don't be too troublesome, this step can save 80% of the after-sales problems.
Step 2: Don't be blind in the selection of types-metal or non-metal? You will understand by looking at these three points
"For desulfurization flue, we must use non-metallic expansion joints, which have good corrosion resistance!" That's true, but it's not absolute. If you think about it, if your flue diameter is particularly large (say, more than 3 meters), or the installation space is limited, non-metallic is really good-lightweight, strong ability to absorb multi-dimensional displacement, ourNon-metallic expansion joints (fabric fiber expansion joints)AndRectangular non-metallic expansion jointThat's what we do.
But on the other hand, if there is high temperature (more than 250℃), high pressure (more than 0.1MPa) in the working conditions, or there are strict requirements for air tightness, then metal bellows may be more reliable. Like the one in our stationUniversal corrugated expansion joint、High temperature axial expansion jointWeather-resistant steel or even stainless steel, with wear-resistant layer lining, can also withstand the desulfurization environment.
How to choose? Look at these three:
- Look at the temperature: Lower than 250°C for a long time, preferential non-metal; Above 250°C, on metal.
- Look at displacement: If it is necessary to absorb axial, transverse and angular multi-directional displacements at the same time, non-metal is the first choice; Mainly absorbing axial displacement, metal bellows are more economical.
- Look at space: If the installation space is narrow and the long tie rod cannot be arranged, the non-metal is more flexible; Plenty of space and longer life for metal bellows.
In addition, note that there is often a large amount of condensed water in the wet desulfurization flue. If the non-metallic expansion joint is selected from rubber (such asrubber compensatorOrRubber PTFE compensator), be sure to confirm the acid resistance, don't be corroded by chloride ions. On the other hand, the metal bellows should pay attention to the installation of a guide tube to avoid the slurry directly washing the corrugations.
Step 3: Three things to do before installation-don't wait for installation to find an air leak
Okay, the selection is done, and the goods have arrived at the site. Are you going to hoist and weld them directly? Wait! There are three things you must do before installation, otherwise it will be too late to regret the air leak after installation.
First, check the direction arrows of the expansion joints.Our expansion joint products are generally marked with arrows to represent the flow direction of the medium or the direction of installation. Such asThe direction of the arrow of the expansion joint refers toIn the direction of medium flow, if you install it backwards, the guide tube becomes a baffle, which not only does not divert the flow, but also accumulates dust and aggravates wear. Don't laugh, I've seen cases of acting backwards.
Second, check whether the guide tube is firm.The function of the guide tube is to guide the smoke through smoothly, while protecting the bellows from being washed. Before installation, you should shake it with your hand to see if there is any welding desoldering and loose rivets. If the guide tube itself is not strong, it will fall off in less than a month after installation, and then get stuck in the corrugated gap, directly destroying the expansion joint.
Third, remove the transport fixtures.Many expansion joints will temporarily fix the bellows with screws and steel wires when they leave the factory to prevent deformation during transportation. It must be removed at the scene, otherwise the expansion joint will not be able to expand and contract normally. Especially for some large tie rod expansion joints, the tie rod nut is locked when it leaves the factory, and it needs to be adjusted according to the design after installation. Regarding tie rod adjustment, our website has a special article "How to adjust the tie rod nut of expansion joint", which is recommended that you read it first.
Before installation, be sure to clean the pipe interface, and no welding slag, burrs and sharp objects are allowed, otherwise the fabric layer of non-metallic expansion joint will be directly scratched, or the surface of metal bellows will be scratched. Scratched bellows are in corrosive fumes and perforate in a few days.
Step 4: The Two Details That Are Easiest To Roll Over During Installation-Tie Rod and Deflector
The installation process looks simple, just weld the expansion joint to the middle of the pipe flange. But the devil is in the details, and here are two places where rollovers are particularly prone.
Tie rod adjustment-not tightening and done
A lot of people getLarge tie rod expansion jointOrCompound hinge transverse expansion jointAs soon as I saw that there were many nuts on the tie rod, I screwed them to death. And guess what? As soon as the system runs, the pipeline expands thermally, and the tie rod is held firmly. The expansion joint can't compensate for the displacement at all, which directly leads to the corrugated pipe being cracked.
According to the design drawings or product description, adjust the tie rod nut to the designated position (generally there will be pre-tension or pre-compression amount). If there is no drawing, a simple experience is to keep a gap of 2~5mm between the tie rod nut and the ear plate, so as to ensure that the expansion joint is free in the cold state and limited by the tie rod in the hot state. Adjustment method Our station question and answer "How to adjust the expansion joint tie rod nut" has a detailed description, you can refer to it.
Orientation of the guide tube-Never install it backwards
The role of the guide tube is to allow the flue gas to flow smoothly and reduce turbulence and scouring. The direction must coincide with the flow direction of the medium, and the inner diameter of the guide tube is usually slightly smaller than the inner diameter of the pipe, creating a gentle slope. If you install it backwards, the flue will form a vortex at the inlet of the deflector, which not only increases drag and vibration, but also throws slurry particles onto the ripples, accelerating corrosion.
So how do you see the direction? Generally, the bell mouth of the guide tube is directed toward the medium, and the small mouth is directed toward the outlet. If the product is not marked, you just touch it with your hands-the inner wall of the guide tube is smooth, and there should be no welding nodules on the upstream surface.
Step 5: Where to look for daily inspections? Three places have problems and quickly change them
Installed and finished? Then you're wrong. The wet desulfurization environment is harsh, and the expansion joint is a wear part, so regular inspection is indispensable. You just have to keep an eye on these three places, and you can be warned in advance.
- Weld and flange joints: This is the old location that is most prone to leaks. Use soapy water or leak detector to test once a month, and mark the bubbles immediately. Especially at the welding between metal bellows and end pipe, once cracks appear, they must be shut down and replaced.
- Bellows surface: Pay attention to whether there are rust spots, depressions or bulges in metal bellows; Nonmetallic expansion joints pay attention to whether the fabric layer is blistered, delaminated, and hardened. Especially close to where the slurry splashes, the corrosion tends to start at a small point and slowly expand.
- Guide tube state: Observe whether the guide tube is worn or perforated through the manhole or endoscope. If the guide tube is broken and the smoke directly impacts the ripples, it is not far from the leakage. It is recommended to do an internal inspection at least once a year.
Also, don't forget to check if the tie rod nut is loose. Long-term vibration will cause the nut to fall back and make the expansion joint lose its limit. If you are usingCompound straight pipe bypass pressure balanced expansion jointFor this kind of complex equipment, it is best to screw all the bolts every quarter.
Okay, after five steps, do you think the wet desulfurization flue expansion joint is not so mysterious? In fact, as long as the working conditions are thoroughly understood, the type is selected correctly, the installation is carefully done, and the inspection keeps up, it will not be a problem to use this thing for three to five years. If you are still unsure, please feel free to flip through our website aboutWhat is the difference between metal expansion joint and corrugated expansion joint、Specific Function of Expansion Joint Guide TubeThese articles, or just talk to us technology. After all, equipment is dead, people are alive, one more question, ten fewer steps.