Find out your flue operating conditions first-temperature, pressure and displacement must not be less
What are you most afraid of when you do selection? Afraid of slapping your head. I've seen many brothers who are engaged in equipment. When they came up, they asked, "How much is your expansion joint?" After asking about the working conditions, they looked confused. Brother, this thing is not to buy cabbage. The temperature difference is one or two hundred degrees. If you choose the wrong model and blow up the pipe, it's too late to cry.
What's the maximum temperature? Is it persistent heat or intermittent? What about pressure? Don't leak either positive or negative pressure. The most important thing is the amount of displacement-that is, which way and how far the pipe will run after the flue expands and contracts. Lateral displacement, axial displacement and angular displacement are written down in categories. To put it bluntly, if you can't even come up with these data, then the selection is basically a chance.
Tips:If the flue is vertical, don't forget the displacement caused by gravity, it is reliable to count it in. In addition, some drawings of old factories don't match the actual situation at the scene. Don't be lazy, take a ruler to measure the actual installation space.
Select products according to working conditions-high-temperature axial type for high-temperature section, transverse type of compound hinge with large displacement
With the data in hand, the next step is to take your seat. Our product line is quite complete, but it's not stuffed in it blindly. For example, in the high-temperature section of the converter flue, the flue gas temperature is always hundreds or even thousands of degrees higher, and ordinary general-purpose corrugated expansion joints can't bear it at all. That's when you have to chooseHigh temperature axial expansion jointThe materials and structures have been specially treated, which can withstand high temperatures and axial compensation.
What if there are many turns and large displacements in the flue? For example, the flue changes from horizontal to vertical, and the pipe can be twisted by several centimeters when it expands and contracts by heat. The simple axial type can't stand it, we have to goDuplex hinge transverse type expansion joint. They work in groups of two (or more), and the hinge structure absorbs lateral displacement and helps you digest angular displacement. We have moneyDouble hinge expansion joint for air-cooled island vacuum pipelineIt's a similar principle, but it's used elsewhere.
There are also those situations where internal pressure thrust is needed and there is no room for fixing brackets, which can be consideredStraight pipe pressure balanced expansion jointOrCurved tube pressure balance expansion jointAnyway, we're all in stock. There is no shortcut to the selection, that is, take the working condition parameters and the product capability table right. If you are really unsure, let the manufacturer calculate the fatigue life-don't look at it as expensive, it is even more expensive when it explodes.
Check before installation-guide tube orientation and tie rod nut should not be removed, just look at the direction of arrow
When the product arrives at the site, don't worry about welding it up. Do a few things first: First, check the direction of the deflector. What's the deflector for? Protect the bellows from being directly washed by high-temperature smoke. If the direction is reversed, the smoke rushes directly to the bellows, and the life is directly cut in half. Then how to judge? Look at the arrows on the expansion joints!Arrow direction of expansion jointUsually pointing to the direction of the flow of the medium, where the arrow is pointed, the guide tube is pointed. Yes, it's as simple as that.
Second, tie rod nuts. Many newbies ask "Do you need to remove the screw of the expansion joint"— The score situation. If the expansion joint leaves the factory with a tie rod to fix the length to prevent transportation deformation, the tie rod nut needs to be loosened (not removed) after installation in place, so that the bellows can expand and contract freely. However, if the flue has not been fixed, or it needs to be limited during the debugging stage, don't move the nut. Remember the principle: the role of the pull rod is to withstand internal pressure thrust or limit, not for you to disassemble and play.
Note:Before installation, illuminate the inside of the bellows with naked eye and flashlight to see if there are any bumps and scratches. Once the metal bellows has pits, it is easy to crack due to stress concentration.
How to adjust it after installing it? — — Adjustment formula of tie rod nut: loosen first and then tighten, leaving enough pre-stretching amount
Guys, putting it on is only the first step, tuning is the key. How to adjust the tie rod nut? Let me sum up a formula for you:Loosen first and then tighten, leaving enough to pre-stretch。 What do you mean? First, loosen the locking nuts during installation, so that the bellows is in a free state; Then, according to the pre-stretching amount required by the design, tighten the nut to the designated position.
The operating temperature of the flue is high and the thermal expansion is large. When installing, a part of the bellows has to be pre-stretched, and after it heats up, it just returns to the middle position, so that the bidirectional fatigue life is the longest. How do you see the amount of pre-stretch? Generally, it will be written in the product manual, or ask the manufacturer. If not, it can be estimated as half of the total displacement (conservative point). When adjusting, it is best to use a torque wrench, and the nuts on both sides are screwed synchronously to prevent deflection.
Another situation is cold installation, hot operation, and the displacement is completely pulled out, so there is no need to pre-stretch, and the bellows can be directly put in a compressed state. This has to be the other way around-install without stretching, just adjust the nut just so that it is not loose or tight. Anyway, don't screw around, find out the working conditions first.
What to pay attention to in routine maintenance-metal hoses and corrugated joints are not bumped, and welds and guide tubes are regularly checked for wear
Let it go after installing it and tuning it? Brother, machines have to be maintained. The environment of the converter flue, high temperature, dust, vibration, everything greets the expansion joint. You go around at least once a month and see three things:Are there any cracks in the weld(in particular a fillet weld between the guide tube and the connection),Are there corrosion pits or wear on the outer surface of the bellows、Has the guide tube been worn out by the smoke。
In addition, there are many mentions in our product informationMetal hoseAndBellowsLike the one on your flueMetal hoseOrPTFE-lined hoseAnd don't ignore it. Their weak point is generally at the root of the joint, and it is easy to crack when it is vibrated. If you find a leak, change it quickly. Don't delay it.
When the furnace is shut down for maintenance, clean up the dust around the expansion joint. After absorbing water, dust will corrode stainless steel, especially sulfur-containing flue gas, which is called a ruthless. If conditions permit, make an external insulation for the expansion joint to reduce the temperature difference stress.
And guess what? I met a customer two days ago, saying that the expansion joint in their factory is still as new after three years of use. When asked, it is because they do regular inspections every quarter and deal with problems immediately. On the contrary, those who think "don't have to worry about it if you install it" often leak in less than a year.
Well, these five steps are enough for you to understand today. From working condition analysis to type selection, from installation to commissioning to maintenance, a line is strung down. If you are still unsure, welcome to our house to ask about technology. Remember,Converter flue metal expansionIn this matter, the effort is spent in the front, and the worry is relieved later.