Specialized in manufacturing compensators, expansion joints, baffle doors

What are the "upper displacement" and "lower displacement" on the drawing talking about?

To put it bluntly, the up and down displacement of the metal expansion joint is the "nod" or "head up" of the pipe in the vertical direction. The technical term is lateral displacement or vertical displacement. You take a design drawing of a steam pipe, which is marked "upward displacement 30mm", which means that the pipe will arch 30mm upward when heated. In turn, cold shrinkage or the underlying bracket settles, and the pipe sinks, that is, downward displacement.

When the temperature of the steam main pipe from the boiler rushes above 400℃, the pipeline will naturally expand. A straight pipe may extend axially, but when it is restricted by an elbow or a fixed bracket, the force runs vertically-the middle of the pipe bulges, and the expansion joint has to "swallow" this upward displacement. If one of the underlying brackets sinks, the direction of displacement is directly reversed. If you can't figure this out, the selection is blind.

Where does the up and down displacement come from? Temperature is the main cause, but not the only one

Temperature changes are the biggest drivers. Everyone knows the truth of thermal expansion and contraction, but there are still a bunch of "hidden players" in actual working conditions. The self-weight of the pipeline will push the bellows down, and the long-term settlement of the support will bring continuous downward displacement. Wind load and even earthquake will make the pipeline swing suddenly. Especially in power stations and cement industries-the diameter of the pipe is always one or two meters, and the temperature is high (Corrugated expansion joint for power station industryOften working above 400℃), the amount of up and down displacement easily reaches tens of millimeters.

Installation error. Two days ago, I met a customer. During on-site installation, I found that the pipeline was out of alignment. I just used a crowbar to push the expansion joint up, and the bolts crackled. And the result? It leaked after two months of running. Why? The bellows has already been subjected to the initial displacement in the installation stage, and the thermal displacement is superimposed during operation, which directly exceeds the limit. Therefore, you must include the "initial offset" when designing, and don't just stare at the theoretical value.

Up and down displacement vs axial displacement vs angular displacement-don't mix it up!

Many novices put the three displacement parameters together to calculate the general ledger, which is a big taboo. The axial displacement is the expansion and contraction of the pipe in its own direction, the upward and downward displacement is the swing in the vertical direction, and the angular displacement is the rotation at the joint. The mechanisms of the three are completely different, and they have to be seen separately when selecting the type.

Let's say,Compound hinge transverse expansion jointIt is specially used to absorb lateral (including up and down) displacement. Its bellows are arranged in pairs, and the direction is guided by hinges. WhileStraight pipe pressure balanced expansion jointMainly cope with axial displacement, you take it to carry it up and down, and the bellows will quickly twist and fatigue. Is the piping arrangement L-type or Z-type? The up and down displacement is often concentrated near the elbow, and it is useless to install the expansion joint on the straight pipe section. The correct way is to do the pipe system stress analysis first, run it through with Caesar II or similar software, and accurately calculate the displacement direction and magnitude of each point.

How to determine the value of up and down displacement? Formula or software?

Don't slap your head to estimate, and don't bother. In a simple case, the axial elongation is calculated by the coefficient of thermal expansion × pipe length × temperature difference, and then it is converted into vertical offset according to the geometric constraints of the pipe system. For example, a 10-meter-long pipeline has a temperature rise of 200℃, the linear expansion coefficient of carbon steel is about 12×10⁻⁶/℃, and the axial elongation is 24mm. If the pipe is fixed at both ends with an elbow in the middle, this 24mm will translate into up and down displacement-by how much depends on the angle of the elbow and the length of the arm.

Forget about complicated piping, use Caesar II or AutoPIPE. Especially those with smokeDesulfurization flue gas baffle doorPipes, temperature fluctuations are large, the medium is corrosive, and the displacement path may be strange. In addition, the "compensation amount" marked in the product sample is conditional-such asUniversal corrugated expansion jointUsually three values are given: axial, transverse and angular, but they are independent and cannot be used at the same time. If you use 30mm for up and down displacement, the axial compensation amount will have to be discounted. See the curve chart in the product data sheet for details.

When selecting, displacement direction and constraint structure are vital gates

In the case of large up and down displacement, the expansion joint with tie rod or hinge is the preferred choice. The function of the tie rod (refer to the question and answer in our station) is to bear the thrust generated by the medium pressure, so that the bellows can only concentrate on absorbing displacement and will not be broken by internal pressure. Such asLarge tie rod expansion joint, the tie rod limits the axial displacement and specifically allows the lateral (up and down) displacement to be effectively absorbed. On the other hand, if the up and down displacement is large but the ordinary axial type is used, the bellows will twist in the vertical direction, and the cracks will come particularly quickly.

When installing, don't forget to look at the direction of the arrow on the expansion joint-that arrow indicates the direction of media flow, and it must not be installed backwards. Only when the guide tube is guided in the correct flow direction can it protect the bellows from high-speed medium erosion. Installing the guide tube backwards is not only useless, but also will aggravate the wear. In addition,How to adjust the tie rod nut of expansion joint？ Generally, the tie rod nut is in a pre-tensioned or pre-compressed state when it leaves the factory. After installation, it needs to be loosened or tightened according to the actual displacement direction. The specific methods are available in our product description.

Too much up and down displacement? Don't expect an expansion joint to carry it

If the displacement exceeds 50mm or even hundreds of millimeters, it is difficult for a single metal expansion joint to balance the fatigue life and pressure bearing capacity. At this time, the combination scheme is more reliable. For example, install a firstCompound hinge transverse expansion jointAbsorb most of the up and down displacement, and connect one in seriesHigh temperature axial expansion jointProcessing temperature expansion and contraction. Or withNon-metallic expansion joints (fabric fiber expansion joints)With metal expansion joint-the flexibility of non-metal is better adaptable to multi-dimensional displacement, but it is not as resistant to pressure and temperature as metal. LikeRectangular non-metallic expansion jointIt is used a lot in flue gas pipes because it can absorb the three-dimensional displacement of up and down, left and right and axial at the same time.

Another way to think is to useRotary compensatorWith the tie rod structure, the rotation angle is used instead of linear displacement, which is suitable for scenes with limited space. Of course, how to build it needs to be combined with pipeline layout, media parameters and cost tradeoffs. In short, understanding "up and down displacement" is not a back definition-calculating the data accurately, selecting the right product, installing the position, and missing one link will cause problems.

What exactly is Lajin? It's not the same thing as a tie rod and a screw

Two days ago, I met a customer and called in a hurry: "The bellows on our site is cracked again. Hurry up and send me two expansion joints with tension bars!" Guess what? He already had a tie rod on his tube, but he used it as a tie bar.

A pull bar (also called a limit pull bar) and a pull bar are two different things. The tie rod generally appears on the expansion joint of large tie rod or the transverse expansion joint of compound hinge, and its main function is to bear the internal pressure thrust and control the bellows from swinging laterally. What about Lajin? It is more like a safety rope-the flanges at both ends of the expansion joint are connected with wire rope or flat steel to prevent the bellows from excessively extending or compressing under pressure. As for those screws that adjust the pre-deformation during installation, they are temporary and have to be removed after installing the pipeline (refer to the question and answer in our station "Do the screws of expansion joints need to be removed").

To put it bluntly, tie bars are permanent passive protection devices, while tie rods are structural parts under design conditions. Don't get mixed up, the consequences are serious.

Under what circumstances must Lajin be installed? Three core scenarios

Not all metal expansion joints have to be fitted with a tie bar. But when you encounter the following three scenarios, you can wait for rework without pretending.

Scenario 1: High pressure steam pipeline.With high steam temperature and high pressure, once the bellows accidentally fails (such as fatigue crack), the internal pressure thrust can instantly push the two ends of the pipe away by several centimeters or even tens of centimeters. The expansion joint with the guide tube is better, but if the straight tube pressure balance expansion joint or the external pressure single axial expansion joint has no tension bar restriction, the consequence is a flying tube. We did a post-event analysis for a power plant. One of their DN600 steam pipes used a universal corrugated expansion joint without a tie bar. As a result, the pipe was misaligned by 15cm after the bellows was torn, and the bracket was directly pulled down.

Scenario 2: Pipelines in earthquake-resistant or settlement areas.In chemical parks, earthquake fortified areas, or where the foundation has soft soil settlement, the pipeline will generate additional unexpected displacement. At this time, the function of the tie bar is not to absorb the displacement, but in case the bellows body is damaged, the tie bar can hold the bottom and prevent the pipe from disengaging. To put it bluntly, it is the last line of defense, similar to a safety rope. Like the metal corrugated expansion joint we supply to the cement industry, if the site passes through the factory building, we generally suggest installing tension bars.

Scenario 3: Large diameter expansion joint mounted vertically.The expansion joint is installed on the vertical pipe section, and the gravity plus the self-weight of the bellows will cause the bellows to stretch unexpectedly if the internal pressure fluctuates. This kind of thing is especially common in the double hinge expansion joint of air-cooled island vacuum pipeline-the bellows itself has to bear negative pressure under vacuum conditions. Once the selection margin is insufficient and there is no tension bar to limit the elongation, the bellows will easily be deflated or cracked.

Consequences of not installing tension bars: Pressure thrust can push the pipe flying

You think the bellows tear is just a minor problem? Wrong. How big is the internal pressure thrust? A simple calculation: DN500 pipeline, working pressure 1.0MPa, thrust = pressure × effective area ≈1.0× (π/4×0.5²) ≈196kN, that is, nearly 20 tons of force. This force is usually balanced by the rigidity of the bellows itself and the pipe support. However, once the penetrating crack appears in the bellows, the 20-ton force instantly loses its constraint and directly acts on both ends of the pipeline. Think about it, can ordinary supports and hangers block the sudden release of 20 tons of thrust?

On high-temperature, high-pressure, toxic and flammable media pipelines, it is equivalent to violating the regulations if the metal expansion joint is not equipped with tension bars. To put it harder, this is risking your life to save money.

By the way, some designers will confuse a tie bar with a tie bar, thinking that you don't need a tie bar if you have a tie bar anyway. Typical logical loophole: the tie rod is an active force-bearing part, and it will also fracture by fatigue. Lajin is a standalone secure backup, and the two do not conflict.

Everything will be fine with Lajin? Pits for installation and adjustment

Alas, loading Lajin looks simple, but in fact, there are many faults.

Pit 1: The preload force is adjusted too much.The tie bar is usually wire rope or flat steel with threaded adjustment at both ends. For the sake of "insurance", some installers tighten the tension bar tightly, and as a result, the compensation ability of the expansion joint is directly locked. The bellows should be expanded and contracted, but it can't move by the tension bar, so it can only absorb stress in frustration-the fatigue life plummets. This is the same as when you jam the retractors of your seatbelt.

Pit 2: Tie bar and bellows interference.Especially on large-diameter thick-walled expansion joints or rectangular expansion joints, if the position of the tension bar is not properly arranged, it will rub against the bellows surface. After the protective layer is worn off, the bellows wait for stress corrosion to crack. The FAQ of "How to adjust the tie rod nut of the expansion joint" in our station is very detailed, but the adjustment logic of the tie bar is similar: the gap should be reserved, and it can't be stuck to death.

Pit 3: The thermal adjustment is ignored.Some expansion joints are loose when installed in cold state, but the displacement changes after the pipeline heats up, and the tension becomes tight instead. The correct method is to adjust the expansion joint itself according to the designed cold tightness or thermal pre-bias, and then install the tension bar. After the tension bar is locked, the actual displacement margin of the bellows is left. We are inrubber compensatorAndUniversal corrugated expansion jointThis is emphasized in the installation instructions of.

How to judge whether the expansion joint on your hand needs to be installed with a stretch? Self-test checklist

Don't listen to the outside blind fooling, directly judge according to the following comparison:

• Is the pipeline medium pressure ≥0.6MPa? Yes → Suggested to install.
• Does the pipeline transport high-temperature steam (≥200℃) or flammable and explosive media? Yes → Must be installed.
• Are expansion joints used in settlement areas or earthquake fortified areas? Yes → Strongly recommended to install.
• Is the expansion joint mounted vertically and has a diameter ≥ DN300? Yes → Suggested to install.
• Is the existing expansion joint already equipped with a tie rod (e.g. large tie rod, double hinge type)? -There are tie bars but it is still recommended to evaluate additional tie bars, especially single hinges may not be able to constrain accidental failure elongation.
• The expansion joint on your hand isCorrugated expansion joint for power station industryOrDouble hinge expansion joint for air-cooled island vacuum pipelineSuch demanding products? When leaving the factory, it will usually be equipped with a stretch bar.

Then again, some customers like to buy their own wire ropes to tie on, which I don't recommend. The tension bar must be designed and checked together with the expansion joint, including the breaking tension, fatigue life and corrosion resistance grade of the tension bar-for example, the high-temperature axial expansion joint next to the desulfurization flue gas baffle door has to be made of 316L or even C-276, otherwise it will rust and break in half a year, and installing it is equivalent to white clothing.

So, should metal expansion joints be fitted with tension bars? My answer is: install it when you need to install it, and don't wait until the bellows are torn, the pipeline is misaligned, and the production is shut down for emergency repair. Leave professional matters to professional people, but at least you have to understand this logic, otherwise you won't know if you are fooled.

Let me give you a word: the non-metallic expansion joint is the compensator

Non-metallic expansion joints are a kind of compensator。 In the industry of pipeline compensation, the words "expansion joint" and "compensator" are mixed every day, and they all refer to the same thing-flexible joints that absorb thermal displacement and reduce vibration and noise. The names are different: "expansion joint" is biased towards structural form, while "compensator" emphasizes function. You flip through industry standardsJB/T 12235-2015 Non-Metallic Expansion JointsThe first page says clearly: "Non-metallic expansion joints, also known as non-metallic compensators". So stop worrying about the words, they're a family.

Then why is there stillrubber compensator、PTFE compensator、Fabric fiber expansion jointThese names? In fact, they are all subdivided down from the material and structure. On our stationNon-metallic expansion joints (fabric fiber expansion joints)It uses flexible materials such as silicone cloth, fluorine tape and glass fiber, which are specially used to deal with high-temperature smoke and corrosive gases. Rubber compensator mainly relies on rubber elastomer to compensate for displacement, weather resistance is poor but cheap. PTFE compensators focus on strong corrosive media, such as concentrated acid pipelines. They are all compensators in essence, but they wear different "coats" for different working conditions-different materials and different applicable scenarios.

What is the difference between non-metal expansion joints and metal expansion joints?

This question is often asked. Metal expansion joints (such as oursUniversal corrugated expansion joint、High temperature axial expansion joint) It can be compensated by the elastic deformation of the bellows, and it can bear high pressure. The pressure level is tens of MPa, but it can't bear corrosion and ultra-high temperature-stainless steel is a joke in front of wet chlorine. The non-metallic expansion joint has no metal corrugation, and depends on the flexibility of fabric and rubber, the temperature resistance can reachAbove 1000℃(Add thermal insulation layer), and it is also acid-and alkali-resistant. What's more, the displacement compensation is large-it can be eaten in both horizontal and angular directions. Two days ago, I met a customer who was doing cement factory renovation. The pipeline had a large thermal displacement and a lot of dust, so I finally chose oursRectangular non-metallic expansion jointIt is because ordinary metal bellows can't bear multi-directional displacement at all, and the rectangular cross section is more friendly to large air ducts.

Non-metal has weak pressure capacity, and the design pressure generally does not exceed 0.1MPa, so it is mainly used in low-pressure large pipelines. High-pressure applications still have to use metal bellows-each has its own strengths.

When must you use a non-metallic expansion joint? Three scenes can't run away

To put it bluntly, non-metallic expansion joints are specially prepared for certain extreme working conditions. First scenario:High temperature flue gas pipeline, such as boiler export and desulfurization tower import and export. With high temperature and sulfur in flue gas, it won't take long for metals to corrode and perforate, and the corrosion resistance and high temperature resistance of non-metals are just the right way. Second scenario:Large diameter low pressure pipelineLike the smoke duct of power plant, the diameter of two or three meters is very common. The metal bellows is expensive and laborious to install, while the non-metal is light, quick to install and convenient to maintain. Third scenario:Where vibration isolation and noise reduction are needed, such as fan import and export. Non-metallic materials have much better damping properties than metals, and can effectively absorb mechanical vibration and airflow noise. OurDesulfurization flue gas baffle doormatchNon-metallic expansion jointIt is a classic combination: the baffle door isolates the smoke, and the expansion joint compensates the thermal displacement of the pipeline. The cooperation of the two can reduce the air leakage rate to below 1%.

Don't just look at the name when you select a model. These parameters are the key

Non-metallic expansion joints are not take-all scenarios. It dividescircle、Rectangular(such as our rectangular non-metallic expansion joints), andFabric fiber type。 Four parameters are fixed when selecting:Temperature, pressure, displacement, medium corrosivity。 When sulfur-containing wet flue gas is encountered, fluorine tape material resistant to acid corrosion should be selected; High temperature dry flue gas, silicone cloth plus insulation layer is enough. In addition, don't ignore the installation details: the direction of the guide tube must be consistent with the flow direction of the medium-there is an arrow on the expansion joint, which will cause airflow erosion if installed backwards and be scrapped in advance. The tie rod nut is locked before leaving the factory, and then loosened after the pipe is installed in place, otherwise it is easy to tear the fabric layer during transportation or hoisting. This is where we areFAQ "How to adjust the expansion joint tie rod nut"It is very clear in.

Don't use non-metallic expansion joints as rubber compensators. The upper temperature resistance limit of rubber compensator is usually only about 120℃, while the non-metallic expansion joint (fabric fiber type) can reach 400℃ or even higher. The price is also quite different-it is not that others are expensive, but that the material cost is there. Wrong choice, three months of air leakage, all the money saved went into maintenance.

Having said so much, it is actually a sentence: the non-metallic expansion joint is indeed a compensator, but it is not a universal patch. Find out the working conditions, choose the right material, and install the deflector. This thing can last ten years. If you want to know the parameters in detail, you can flip through our websiteNon-metallic expansion joint (fabric fiber expansion joint)The product page is clearly marked in the data sheet.

Let's make it clear first: Is metal "thermal expansion and cold contraction" or "heat shrinkage and cold expansion"?

The opening chapter first solves an inevitable misunderstanding. Search "The role of heat-shrinkable and cold-expanded metal expansion joint?" on the Internet, a bunch of people think that metal pipes will shrink when the temperature is high, just like some alloys. What about the facts? Stainless steel and carbon steel used in most industrial pipelines follow thermal expansion and contraction honestly. Those very few abnormal bismuth-antimony alloys can't be used in our pipeline industry at all. So don't be literally taken off-the core mission of the expansion joint is to absorb the thermal expansion and contraction displacement of the pipe due to temperature change.

How does the expansion joint "eat" the thermal expansion and contraction?

Take this site'sUniversal corrugated expansion jointLet's use an analogy. Its bellows are like the bellows of an accordion. When the heating pipe becomes longer, the bellows are compressed; The cooling becomes shorter and the bellows is stretched. It just stretched and contracted, eating the displacement into it. The actual product will also be equipped with accessories such as guide tube, tie rod, limit bolt, etc. -the guide tube guides the flow direction of the medium to prevent high-speed airflow from directly washing the bellows; The tie rod and limit bolt control the displacement direction to avoid excessive stretching or instability of the bellows.

What about encountering high temperature conditions? For example, the temperature of steam pipes in power plants goes to five or six hundred degrees Celsius, and ordinary bellows have long been soft. This is the time to use itHigh temperature axial expansion jointHeat-resistant alloys (such as Inconel 625) and special wave patterns are designed to ensure elastic stability. And guess what? Some customers only want to be cheap when selecting models, and use ordinary bellows, which will crack and leak in a few months, which is not worth the loss.

Which expansion joint should I choose for different working conditions? Don't expect one model to conquer the world

High pressure and high temperature fluctuation of steam pipeline in power plants are the first choiceCorrugated expansion joint for power station industryAndStraight pipe pressure balanced expansion joint。 Why? Because the internal pressure will generate a huge axial thrust, ordinary expansion joints can't bear it. The pressure balance type cancels out the thrust through the internal structure, so that pipelines and equipment are safe.

What about buried pipes? Consider soil corrosion and axial thrust. At this timeDirect buried (fully buried) type expansion jointIt comes in handy-it comes with its own anti-corrosion layer and insulation layer, so you don't have to worry about it when you bury it. The flue air duct and desulfurization flue gas system in the cement industry have low temperature but large diameter.Non-metallic expansion jointOrMetal rectangular expansion jointIt is more cost-effective, can absorb multi-directional displacement, and the cost is low. If there is vibration or a location that requires frequent maintenance,rubber compensatorOrRotary compensatorIt's also a good choice.

Is that the case? With the right type, the system life difference can be ten years.

The easiest pit to step on during installation-the lesson of customer blood

Two days ago, I met a customer who tightened the tie rod nut on the expansion joint. As a result, as soon as the pipeline heated up, the bellows directly exploded, and the scene was terrible. Tsk, that's a typical mistake. Remember: the mounting bolts (those few screws) that the expansion joint is shipped with must be removed or loosened before it is officially put into operation! Tie rod nuts are meant to limit overstretching, not for you to lock up. The correct way is: adjust the tie rod nut to the designed length during installation, and the nut will naturally have a gap after the pipeline heats up.

In addition, the direction of the arrow on the expansion joint shell must point to the direction of the medium flow, and the guide tube should be directed toward the medium-if it is installed backwards, the high-speed airflow will directly flush and perforate the bellows. Also, the fixing brackets on both sides of the expansion joint must be firm, otherwise no matter how many expansion joints you install, the pipe will twist around like a snake, and it will be a matter of time before the flange interface leaks.

In one sentence: The expansion joint is the "expansion joint" of the pipeline

Just like bridges should leave joints to prevent heat expansion and damage, industrial pipelines rely on expansion joints to "breathe". Stop worrying about that "heat shrinkage and cold expansion"-choose the right type, install the right direction, leave enough space, and there will be no big problems in the pipeline system for 20 years. If you are still worried, flip through the product information of this site,Universal corrugated expansion joint、Straight pipe pressure balanced expansion joint、High temperature axial expansion joint…Each model has a clear working condition, just follow it.

Is the non-metallic expansion joint wire layer inside or outside? Wrong location, the consequences are serious

The wire layer is usually not in the outermost layer, but hides in the middle or inside. Many people look at the picture and think that the shiny layer outside is steel wire. In fact, it is an outer protective cloth or metal mesh sleeve. To be honest, I have encountered many customers who regard the steel wire layer as an anti-wear layer and have to ask for it to be put outside. As a result, it wore out in less than half a year. The real steel wire reinforcement layer-which we often call stainless steel wire mesh or galvanized steel wire mesh-is sandwiched betweenNon-metallic expansion joint (fabric fiber expansion joint)Between fluorine tape, silicone cloth and fiberglass cloth. The purpose is to give it a skeleton so that the soft non-metallic layer can withstand the positive and negative pressures in the pipeline, without bulging or deflating like a balloon.

Why do you have to add this layer of steel wire? To put it bluntly, the non-metallic expansion joint itself is a pile of fabric and rubber, and has limited tensile strength. When the internal pressure of the pipeline runs, there is no steel wire layer to cover the bottom, and the expansion joint will deform and fail directly. Wire layers are like steel bars in concrete, dispersing axial and radial forces. For specific data, you can refer to this siteNational Standard for Non-Metallic Expansion Joints JB/T 12235-2015Which clearly specifies the material and arrangement of the reinforcing layer. Also, something likeRectangular non-metallic expansion jointFor this large cross-section, the steel wire layer has to be densified and thickened, otherwise the stress at the square corners will be concentrated and it will be easy to tear.

However, the position of the steel wire layer is not static, it depends on the working conditions. For example, in the desulfurization flue gas pipeline, the medium contains acid and humidity. At this time, the steel wire layer usually leans against the inner layer, and several layers of corrosion-resistant polytetrafluoroethylene or EPDM rubber are wrapped outside to prevent acidic gas from directly corroding the steel wire. On the other hand, if the pipeline is running under negative pressure (such as the air cooling system of a power station), the steel wire layer has to be close to the outer surface, and the inner layer is used with a more flexible silicone cloth to absorb the negative pressure deformation. Two days ago, a customer in the cement industry asked, saying that they usedMetal Corrugated Expansion Joints in Cement IndustryGet used to it, and I am afraid that it will not be durable if it is replaced with non-metallic. I told him that if the layout of non-metallic steel wire layer is reasonable, the life span is not bad at all.

What are you most afraid of? I am most afraid of installing the steel wire layer in the wrong position. There was a power plant project before, and the installer saved the trouble by installing the non-metallic expansion joint in reverse, with the steel wire layer facing outward. As a result, within two months of operation, the outer fabric was worn out, the steel wire was exposed, rusted and broken, and the whole expansion joint directly leaked and stopped. In addition, there is also a situation that the steel wire layer is designed too inward and too close to the medium, and the high-temperature gas (over 400℃) burns the steel wire soft and loses its reinforcing effect. Therefore, when you buy, you must tell the manufacturer clearly about the medium temperature, pressure, positive and negative pressure, and don't just stare at the price. In the industry customer cases of this site,Flue gas baffle doorThe matching non-metallic expansion joint is specially aimed at the high-temperature dusty air flow to optimize the position of the steel wire layer.

Then how do you judge which category you should choose? Simple and rude method: Look at the nameplate or drawings. Regular manufacturers like us will make arrows on the flange on the non-metallic expansion joint to indicate the flow direction of the medium. If you are really worried, take a bright flashlight and take a look at the cross section-the reflection of steel wire mesh and the diffuse reflection of fiber cloth can be distinguished at a glance. If you buy it back and find that the steel wire layer is outside, and there is dust washing under the working condition, install the external sheath quickly. Finally, a reminder: Don't believe the nonsense that "the steel wire layer is universal inside and outside". The structural design of non-metallic expansion joints is calculated by stress. If the position is wrong, no matter how large the compensation amount is, it will be useless.