Specialized in manufacturing compensators, expansion joints, baffle doors

Find out first: What exactly is the skin non-metallic compensator?

Look at the name-skin non-metal compensator. Do you feel tall and confused when you hear it? In fact, to put it bluntly, it is the soft connector responsible for "flexible compensation" in the pipeline system. Structurally simple: a circle of metal flanges or carbon steel frames with a special flexible skin sandwiched between them, that's it. And metal expansion joints (like the one in our stationUniversal corrugated expansion joint、Metal rectangular expansion joint), the difference is bigger-those metals deformed by bellows, with high rigidity and small displacement, which are suitable for high-pressure clean media; The skin relies on the elastic deformation of fabric and rubber layer, which can compensate for large displacement in three dimensions and hardly transmit thrust. If you want to draw a picture, the left side is a rigid bellows, and the right side is a soft skin laminated structure. You will understand its "soft" truth at once.

Cough, in practical applications, flue gas pipelines, desulfurization systems, air ducts and other places have high temperature, strong corrosion, alternating hot and cold, and dust particles-do you let metal bellows carry it? It can't handle it for a few days before it cracks from fatigue. At this time, you have to rely on non-metallic compensators to play. So don't be fooled by the name, it's a flexible joint specialized in "dirty work".

Why can it withstand high temperatures and corrosion resistance? — — The mystery of the core material "skin"

The skin is not a piece of cloth, it is a composite of layers of materials. The most common is: the outermost layer is silicone cloth or fluororubber coated cloth, with glass fiber cloth and polytetrafluoroethylene film sandwiched in the middle, and a layer of acid-resistant rubber may be added to the inner layer. Each layer performs its duty-silicone cloth carries temperatures above 200℃, fluororubber is resistant to acid and alkali corrosion, glass fiber provides tensile strength, and polytetrafluoroethylene is anti-adhesion. Let's put it this way, the acid-alkali condensate and high-temperature steam in the flue gas pipeline have long been rusty through the single-layer metal plate, but the skin is forcefully supported by these laminated combinations.

Talk about the desulfurization system. Although the flue gas temperature after wet desulfurization drops to about 50℃, it contains a large number of sulfuric acid and sulfurous acid droplets. The fluororubber layer in the skin non-metallic compensator can directly resist acid-alkali corrosion, and the skin itself does not conduct heat, which can also reduce the heat bridge effect of pipelines. That's why our stationNon-metallic expansion joint (fabric fiber expansion joint)AndRectangular non-metallic expansion jointThe appearance rate in desulfurization projects of power plants and cement plants is so high. Is that the truth?

Don't step on pits in model selection: how much displacement with how thick skin?

You really can't slap your head when it comes to selection. Two days ago, I encountered the purchase of a cement factory, and I chose a thin skin for the air duct cheaply. As a result, it bulged and leaked in less than half a year-losing dozens of tons of cement output. There are three core principles: compensation amount, pressure level and medium temperature. Take the one from our stationRectangular non-metallic expansion jointFor those with large angular displacement, the skin has to be reinforced, and the number of glass fiber layers is increased from two layers to four layers; If the amount of axial stretching is large, the depth of the preset folds of the skin must be sufficient. The pressure level-low-pressure air duct (below 0.1MPa) can be reinforced with a single layer of skin, but if it is a positive pressure environment above 0.2MPa at the inlet of desulfurization tower, it is necessary to choose a double layer of skin and stainless steel wire mesh to reinforce it.

Medium temperature is a ruthless character. A silicone cloth-glass fiber combination is sufficient below 150°C; If it exceeds 300℃, you have to change the configuration of fluororubber-ceramic fiber. Real case: The raw material grinding ventilation pipe of a cement plant, the temperature is 280℃, the silica gel cloth skin is selected, and it will be layered in half a year. Later, it was replaced with fluororubber skin, and it is still in use for three years now. The wrong layer of material is selected, and the life difference is more than five times.

Install that little thing: to make it work, you have to untie it first

When installing a skin non-metallic compensator, the most taboo thing is "thinking that you can install it when you bring it". Remember three points, one less, and half the equipment will be scrapped.

• Transport tie rod must be removed: In order to fix the skin when the manufacturer delivers the goods, several temporary tie rods will be installed. Connect the pipe directly without dismantling it? Hey, the compensator can't move at all, the thermal expansion is all stuck in the pipes, and the equipment quickly deforms. After installation, confirm that the flange bolts are tightened, and immediately remove the tie rod.
• Pre-stretched (or pre-compressed): According to the design drawings, give the skin an initial displacement amount during installation. For example, if the pipeline is installed at ambient temperature, it will expand when the operating temperature rises, so the skin should be pre-compressed a little during installation, so that the compensation amount is enough. This value is given by the design engineer, so don't guess for yourself.
• Flange centering: The flanges on both sides of the compensator must be aligned parallel with a deviation of no more than 2mm. If forcibly straightened with bolts, the skin will be unevenly stressed, the angular deformation will exceed the limit, and the life will be directly cut in half. Besides, we have to talk to the people in our stationFlue gas baffle door、Round flapper doorIn case of cooperation, pay attention to the compensator to be installed downstream of the baffle door (according to the flow direction of the medium), so that in case of skin leakage, it will not directly rush to the sealing surface of the baffle door.

Once the installation is done, check again-is the tie rod removed? Is the flange bolt torque uniform? Is the pre-stretch amount in place? If this step is done wrong, the compensator will basically hang up. Tsk, we have seen too many cases of equipment being scrapped on site because we forgot to remove the tie rod.

How long is the lifespan? How to fix it if it is broken?

Under normal operating conditions, the design life of the skin non-metallic compensator is 3 to 5 years. But the actual life span is related to the conditions you serve-the medium contains acid and alkali, frequent start and stop, and large temperature fluctuations, so the life span will be shortened to one and a half years; If it is used to clean air ducts, it may be seven or eight years. How do you tell if it's time to change it? Two tricks on-site inspection: first, see if there is any bulging, delamination and cracking on the skin surface; Second, see if the flange bolt is loose (loose means that the skin creeps and deforms). As long as you find bulging or layering, change it quickly and don't delay it.

The first step is to loosen the flange bolt and remove the old broken skin (take care to protect the flange sealing surface). Step 2, clean the flange surface and apply temperature-resistant sealant (silicone rubber or fluorine rubber glue). The third step is to put on the new skin, pay attention to the direction not to install the reverse, and use the diagonal tightening method when tightening the bolts, and the torque is uniform. The whole process is done in half a day, and you don't have to stop production for too long. If there are multiple compensators in the pipeline system, it is recommended to replace them all at once, so as to avoid problems one by one in the future.

From our stationrubber compensatorAndRubber PTFE compensatorIt also belongs to the non-metallic category, but the structure is slightly different-the rubber compensator focuses on vibration damping, and the skin compensator focuses more on high temperature and corrosion. Which one to choose? It depends on the working conditions.

Find out if you want a non-metallic compensator

Two days ago, I met a customer who was anxious to buy a "large-diameter non-metallic compensator" on the phone. As a result, after chatting for ten minutes, I found out that he was using a rubber compensator on the spot, and the temperature had soared to 350℃-the rubber had been carbonized early. I've seen this happen a lot.

Non-metallic compensators (also called fabric fiber expansion joints) are completely different from metal bellows and rubber compensators. The metal bellows absorbs displacement by deformation of stainless steel corrugated body, and has high pressure resistance but limited compensation; Rubber compensator relies on rubber elasticity, corrosion resistance but fear of high temperature and high pressure. WhileNon-metallic compensatorThe main body is flexible loop belt (multi-layer fabric + fluororubber/silicone coating), and the frame is metal, which is specially designed to deal with high temperature, large displacement and low pressure working conditions. If you buy the wrong one, it will leak at least and the pipe will be broken at worst.

Then how to judge? Look at three indicators: the temperature is higher than 150℃, the pressure is lower than 0.1MPa, and the pipe diameter exceeds DN500-it is the home field of non-metals. If you don't believe me, check JB/T 12235-2015. It is clearly written in the standard.

The first step of model selection: medium, temperature and pressure, you dare to fill in these three numbers, and you will wait for problems later

The most common mistake made by purchasers is to say "probably" and "almost" when reporting parameters to suppliers. Tsk, if one of these three numbers is not accurate, the compensator will not be able to use it.

• Medium: Acidic condensate in the flue gas? The outer surface of the band must be filled with a PTFE anti-corrosion layer. Contains hard particles? The inner layer must be made of wear-resistant ceramic cloth. We have them in our stationNon-metallic expansion joint (fabric fiber expansion joint)Is specialized in dealing with this kind of working condition.
• Temperature: Don't just report "working temperature", but report "maximum instantaneous temperature". The instantaneous temperature of desulfurization flue in many power plants can rush to 400℃, and the ordinary silicone ring belt burns through directly. Here, you must confirm the number of layers of the belt material and the temperature gradient of the supplier-such as a three-layer structure: outer layer of fluororubber (250℃), middle layer of fiberglass cloth (550℃), inner layer of steel wire mesh (support).
• pressure: The design pressure of non-metallic compensator generally does not exceed 0.1MPa. If you report 0.2MPa, you have to use a metal frame with reinforcing ribs, or simply change the metal expansion joint.

You ponder, these three numbers are filled in, do you have to spend money on rework later?

When the caliber is large, the structure has to change accordingly: What is the difference between rectangular and circular design?

Many people think that circles and rectangles are just different in shape, and the choice is universal-a big mistake. After the caliber exceeds 1 meter, the design logic of the two structures is completely different.

Circular non-metallic compensator: Mainly used in round pipe flue, the ring belt is annular integral, and the flange is usually angle steel or flat steel coiled. Because the force is symmetrical, the band thickness can be relatively thin. However, it should be noted that the large diameter circular guide tube must be designed to be tapered, otherwise the fluid will scour the inner wall of the ring belt.

Rectangular non-metallic expansion joint: Square pipe flue is commonly used, such as sintering machine head in steel plant. The biggest problem with rectangular structures isCorner stress concentration。 The loop belt is easy to tear at the corner, so it should be molded with a special die when manufacturing, or a reinforcing layer should be added at the corner. In addition, the four sides of the rectangular frame should be designed separately with pressing strips, which can't be simply rounded.

If you are purchasing large diameter rectangular compensator, be sure to ask the supplier: How to seam the corner band? Is it a lap or a docking? Has the lap length exceeded 50mm? These details determine whether it will last five years or eight months.

What are the hard indicators hidden in the national standard JB/T 12235-2015 that purchasers must know?

Many purchases regard national standards as decorations. JB/T 12235-2015 "Non-Metallic Expansion Joints" I pick a few must-see hard requirements:

• Belt withstand voltage test: Before leaving the factory, an air pressure test of 1.5 times the design pressure must be done, and the pressure must be kept for 5 minutes without leakage.
• Displacement compensation amount mark: The allowable compensation amounts in axial, transverse and angular directions must be clearly marked on the expansion joint. Don't look at the unmarked.
• Flange flange length: The connection between the non-metallic ring belt and the flange must be flanged, the length of the flange shall not be less than 20mm, and fixed by pressing strips. The flanges are too short, and the ring band will slip out of the flange groove during the run.

By the way,Expansion joints and compensators are the same thing, it is also mixed in the standard, so you don't have to worry about the title problem.

Don't just look at the price: the supplier's manufacturing process, the number of layers of belt material, and the length of flange are the real skills

And guess what? Many small factories report bargains, the circle belt has only two layers of cloth and one layer of glue, and the flange flange is folded by 10mm. Loaded it up and ran for three months, leaked. You spend another amount of downtime changing it, which is three times more expensive than buying good goods.

How to judge the manufacturer's real ability? Ask three questions:

1. Number of belt material layers: At least three layers, the inner layer is high-temperature resistant fabric, the middle layer is heat insulation, and the outer layer is sealing anti-corrosion layer. What is the thickness of each layer? What grade of silicone/fluorine is used?
2. Flange flange length: The measured flange side length is not less than 25mm before it is considered qualified. Have you installed stainless steel strips at the flange? Is the spacing of the beading screws not greater than 150mm?
3. Frame welding process: Do corner welds of large-diameter frames do flaw detection? Did you do overall hot dip zinc anti-corrosion? These determine whether the frame will rust out within two years.

By the way, this kind of product in our site is calledRectangular non-metallic expansion joint, andNon-metallic expansion joint (fabric fiber expansion joint)All have been verified by multiple working conditions.

Acceptance of arrival and installation precautions: direction of guide tube, whether the tie rod nut should be removed or not, and how to pre-stretch

• Direction of guide tube: The guide tube must be directed downstream of the medium flow direction. When installed backwards, the fluid directly impacts the loop belt, and the hole is pierced in one week. There are generally arrows on the expansion joint to mark the direction, and if there is no mark, let the manufacturer make up.
• Do you remove the tie rod nut or not?Transport tie rods are used to prevent deformation during transportation and must be loosened or removed before installation. But note: Some designs have limit rods, and that one can't be removed. How to distinguish? Read the instructions. Really confused, just ask the manufacturer: "Does the screw of the expansion joint need to be disassembled?" Generally, the manufacturer will tell you clearly.
• Pre-stretching: The compensator needs to be pre-stretched to the specified length if there is a cold tightening requirement when the pipe is installed. The pre-stretching amount is carried out according to the design value, and after stretching, it is fixed with temporary supports, and then released after the pipe is connected. Don't pull blindly, pull the headband strap and scrap it directly.

Also, check whether the flange surface is flat and the sealing gasket is centered when installing. When tightening the bolts, tighten them diagonally and sequentially, and the torque should not be too large to prevent crushing the flange.

Purchasing is three things in the final analysis

First, confirm the medium/temperature/pressure, don't pat your head; Second, selecting the right structure according to the caliber and shape; Third, inspect the goods and check the process details. Do these three things,How To Buy Large Caliber Non-Metallic Compensator?This question is a sure thing.

If you are unsure of anything, you can directly compare the product information of this site, such asNon-metallic expansion joint (fabric fiber expansion joint)AndRectangular non-metallic expansion jointThe pages all have detailed parameters. Don't be afraid to ask, asking clearly saves money than buying the wrong one.

How harsh is the working environment of a high temperature expansion joint? The bellows itself can't carry it

Tell me the truth. Two days ago, the equipment supervisor of a cement plant called me and said that the expansion joint on their kiln tail flue cracked in less than four months. I asked him did you make castables? The other party was stunned for a moment. "You still need castables? Isn't the bellows able to withstand high temperatures?"

The flue gas temperature is often 800℃-1100℃, and some even rushes to 1300℃ instantaneously. There are also a lot of dust and corrosive gases (SO₂, NO₂) trapped in the medium. The stainless steel materials used in the bellows itself, such as 304 or 316L, will experience carbide precipitation, intergranular corrosion and cliff-like decrease in strength under long-term high temperature-this is called high-temperature failure. Even if you use a nickel-based alloy like Inconel 625, the surface temperature exceeds 650℃ and you have to stop.

Streaking bellows are consumables under high temperature conditions. What about that? It must be dressed with a piece of "armor"-castable.

The first layer of protection of castables: thermal insulation to prevent high temperature failure of corrugated pipes

Castables are first and foremost thermal insulation. Its thermal conductivity is typically between 0.3-0.8 W/m K, while the thermal conductivity of corrugated stainless steel is above 15 W/m K. What's the meaning? Castables can block most of the heat radiation and heat conduction. For example, we giveCorrugated expansion joint for power station industryWhen designing castables, the inner surface temperature should be controlled below 200℃, so that the yield strength of bellows can be maintained at the design value.

At the expansion joint at the outlet of the induced draft fan of a thermal power plant, the temperature of the outer wall of the bellows before castable was 480℃, and after 80mm thick lightweight mullite castable was placed, the outer wall dropped to 180℃. The lifespan has been pulled directly from 9 months to 5 years and still hasn't broken. Thermal insulation can't pass, and the rest is all nonsense.

The second layer of protection: diversion and anti-scour, blocking the wear of high-speed dusty airflow

You think only the heat is the killer? High-speed dusty airflow is the real "taking your life". The flow rate of the air duct on the cement production line is often 18-25m/s, which is mixed with clinker particles. When that thing hits the bellows, it is like sandblasting. The geometric structure of the peaks and valleys of the bellows itself is a "ash nest", and the dust accumulates in the valleys and rubs them repeatedly, and wears them out quickly.

After the castable is hit, a smooth flow channel will be formed on the inner side, without groove dead angles, and the airflow will pass smoothly. At the same time, the wear resistance of castable is 3-5 times that of ordinary carbon steel (high aluminum castable, Mohs hardness above 7). OurMetal Corrugated Expansion Joints in Cement IndustryBefore leaving the factory, the diversion design is done, but the diversion tube plus castable is the double insurance-the diversion tube blocks most of the frontal impact, and the castable fills the gap to prevent vortex erosion.

Think about it, if you don't hit castable, how fast will the bellows be worn out at the crest? We have measured that the unprotected bellows perforates in an average of 3 months at the outlet of the cement mill. After beating the castable, carry it for at least two years.

The third layer of protection: structural support and anti-corrosion, isolating corrosive media from the bellows

Acidic condensation in high-temperature smoke is a hidden killer. In some projects, the temperature drops below the dew point after the furnace is shut down, and SO₃ and water vapor combine to form sulfuric acid, which adheres to the inner wall of the bellows. Stainless steel is most afraid of chloride ions and concentrated sulfuric acid, pitting corrosion and stress corrosion cracking follow one after another. Castables are alkaline or neutral materials (such as corundum) that keep acidic media out of the bellows.

Additionally, the castable also provides structural support. Especially for large fluesNon-metallic expansion joint(Fabric fiber expansion joint), although it is temperature-resistant but has poor rigidity, the castable can fix the shape and prevent negative pressure deflation. InHigh temperature axial expansion jointThe castable layer can share a part of the axial pressure and reduce the stress concentration at the root of the bellows. It can be said that castable is not only a protective layer, but also a part of the load-bearing structure.

How to beat castables to be qualified? Construction details and material selection determine life

After discussing "why to fight", let's talk about "how to fight" next-there are more people stepping on pits here.

Material selection:Select different materials for different working conditions. High aluminum castable for flue gas temperature ≤800 DEG C; Corundum mullite for 900-1100 DEG C; High temperature resistant castables containing silicon carbide must be used above 1200℃. Don't listen to the manufacturers saying "general-purpose type", that's all fooling laymen. We giveDesulfurization flue gas baffle doorFor matching expansion joints, we should also consider acid resistance, and choose castables combined with low calcium aluminate cement.

Construction Details:First, the anchors must be welded firmly, 304 stainless steel anchor nails, with a spacing of less than 200mm, are distributed in a plum blossom shape. Second, before pouring, the bellows surface must be removed from rust and brushed with anti-oxidation coating. Third, curing-it can't be baked immediately after pouring. It must be naturally cured for 24 hours before baking according to the temperature rising curve (usually, the temperature is raised to 600℃ every 50℃/h for 4 hours). If the curing is not in place, the castable will crack and fall off, and dry for nothing.

Thickness control:Not that the thicker the better. Too thick will increase the weight and affect the compensation ability of the expansion joint. Experience value: 40-60mm in the center, and the edge can be as thin as 20mm. Use special molds to ensure uniform thickness. In addition, the end of the guide tube should leave an expansion gap, otherwise the castable will bend the top of the guide tube as soon as it expands.

To put it bluntly, playing castables looks simple, but in fact, it tests the understanding of working conditions and the seriousness of construction. We have seen too many customers buy castable paste by themselves, and the result is that slag falls in two months. I regret that I didn't find a professional manufacturer to mix itUniversal corrugated expansion jointThe castable scheme of.

Why Should High Temperature Expansion Joints Be Castable?Because the bellows is a "crispy skin" under the attack of high temperature, erosion and corrosion, the castable is the human shield that can carry and fight. No pouring, compulsory within six months; If you water it right, you don't have to worry about it for five years.

Find out how the outer skin is broken

The outer skin of large non-metallic compensators is damaged for the same reasons: aging, mechanical scratches and media corrosion. But which one is specific, directly determines how you fix it later. For example, if high-temperature flue gas runs in the flue gas pipeline for a long time, coupled with the erosion of acidic gases (such as SO₂ and H₂S), the skin will gradually become brittle and hard, and fine cracks will appear on the surface-this is called aging damage. If pulverized coal or particulate material is transported in the pipeline, high-speed scour will partially wear the skin, forming small holes or strip-like scratches-this is mechanical damage. There is also chemical corrosion, such as the wet flue gas behind the desulfurization tower. The pH value of the condensate is low, the skin is soaked, and the surface is blistered and delaminated.

Are there any curls around the edges? Did it change color? Is the interior insulation cotton exposed?If the skin has become brittle as a whole and drops slag when touched, it is of little significance to repair it. It is more cost-effective to directly replace the whole non-metallic expansion joint (fabric fiber expansion joint) or rectangular non-metallic expansion joint. Repairs are only valuable if they are localized piercings or scratches.

What preparation work can't be saved before patching?

Safety comes first. Shutdown, pressure relief, power failure – these three steps are the bottom line. Non-metallic compensators are usually used in the environment of high temperature, dust and corrosive media. If the knife is moved without relieving pressure, an accident may occur. After the pressure relief is completed, wait for the pipeline temperature to drop to the ambient temperature (generally lower than 40℃), and then use a blade to clean all the dust accumulation, loose fibers and residual glue layer in the damaged area to expose the fresh substrate surface. The surface should be dry without water stains or oil stains.

In terms of materials, the commonly used accessories in our station are fluororubber cloth, silicone cloth and stainless steel wire mesh, which can be selected according to the same color and material of the original skin. If we can get a sample of the old skin on site,Be sure to measure the total thickness and number of layers。 The outer skin of non-metallic expansion joints is usually a multi-layer composite structure, such as the outermost layer is fluororubber cloth, sandwiched with aluminum silicate fiber cotton in the middle, and the inner layer is reinforced with stainless steel wire mesh. If the thickness is poor, the strength of making up is not enough, and it is easy to tear twice in the later stage.

Hands-on repair, divided into three common situations

Small area perforation (less than 50mm in diameter)

Cut a piece of composite material 30-50mm larger than the damaged area, and stick one layer inside and outside. The inner patch is attached to the inside of the pipe (sticking through the opening), and the outer patch is covered on the outside. High-temperature vulcanized glue is used for adhesive, and epoxy resin glue can be used if it is not available on the spot, but attention should be paid to the curing time. After the patch is attached, press the edge with mechanical strips (such as stainless steel flat strips), fix them with bolts, and apply a layer of sealant on the back of the strips in advance. Pay attention to the ambient temperature: when it is lower than 5℃, the adhesive effect will be discounted, so you have to preheat the repair area to above 15℃ with a hot air gun in advance.

Large area tear

If the tear length exceeds 200mm, or there are multiple tears, the double-sided patch will not be enough. It is necessary to cut a brand new skin, an area larger than the damaged area,Lap width at least 100mm。 Note: The non-metallic compensator is a multi-layer structure. Each layer should be staggered, and the overlap seams of all layers should not be stacked together, which will create weak points. When cutting a new skin, stick it layer by layer according to the lamination order of the original skin-first stick the inner fiber layer, then stick the middle insulation layer, and finally stick the outer fluororubber cloth. Each layer is compacted with a roller to drain air bubbles. Finally, tighten with strips and bolts, and control the spacing of strips at 150-200mm. Don't forget to apply high temperature resistant sealant on the back of the strip and around the bolt holes to prevent air leakage.

Edge breakage

Broken edges are easiest to fix. The compensator presses the skin tightly on the metal flange by the pressing bar. If the edge is broken, the old pressing bar is directly removed, the damaged section is cut off, a new skin is replaced and inserted again, and then the pressing bar is used to screw the bolts. During operation, pay attention to the new skin to leave sufficient flange length, at least 50mm, the press strip should be evenly pressed, and the torque should be according to the recommended value given by the manufacturer (generally, the torque of M12 bolts is 50-70N·m).

Don't be in a hurry to turn it on after replenishing

After the repair work is finished, do an airtightness check first: get some soapy water and spray it on the repair area and the gap between the strips, turn on the low-pressure air source (or blow it with compressed air) to see if there is any bubbling. Conditionally, do a low-pressure airtight test, control the pressure at about 1.2 times of the design pressure, and hold the pressure for 10 minutes without dropping the pressure. Check the torque of the strip bolt again-the torque attenuation is the main cause of later leakage, especially the thermal expansion and contraction under high temperature conditions can easily lead to bolt loosening.

Finally,Record repair location, date, material model used on equipment ledger。 Focus on this patch area the next time you shut down for maintenance, because the life of patches is usually only 60% to 80% of the original skin. Don't expect to do it once and for all.

When should I just replace it with a new one?

Patching is not a panacea. If the following occurs, don't hesitate to replace it with a brand-new non-metallic compensator or rectangular non-metallic expansion joint:

• The whole skin has reticular cracks, which feel brittle and breaks as soon as it is broken-indicating that the substrate has aged in an all-round way, and it will break if it is repaired here and there.
• The internal insulation cotton layer has rotted to black slag, or it absorbs water seriously-the failure of the insulation layer will cause the skin to be directly exposed to high temperatures, and the life will be shortened.
• There are more than three leakage points, and the spacing is less than 500mm-this porous state indicates that the skin has been fatigued in a large area and cannot be repaired.

The non-metallic expansion joints (fabric fiber expansion joints) and rectangular non-metallic expansion joints in our station are shipped from the factory according to JB/T 12235-2015 standard, and the warranty period and life are much more reliable than those of repair parts. Don't save hundreds of dollars, and you lose tens of thousands at a time when you shut down. Do you think that's true?

1. Let's start with the structure: What is the difference between non-metallic waveform compensator and metal expansion joint?

Many people think "non-metal" is a cheap substitute when they hear it, but it's just the opposite. Non-metallic waveform compensator (also called in our stationNon-metallic expansion jointOrFabric fiber expansion jointInstead of a metal bellows, the main body is a composite of multiple layers of flexible materials-usually including silicone/fluororubber coated fiberglass cloth, PTFE film, ceramic fiber insulation, plus stainless steel wire mesh reinforcement. This structure gives it a natural ability that a metal expansion joint can't do:Barely transmitting thrust。

Think about it, although the metal bellows can absorb displacement, it will still produce elastic reaction force itself, which has additional requirements for the pipe support; The non-metallic compensator depends on the flexible deformation of the fabric, and the reaction force is very small, so it is especially suitable for those thin-walled pipelines or equipment interfaces that can't bear large thrust. Two days ago, there was a customer who made a dust removal system. The wall thickness of the pipe was only 3mm. Every time he drove with a metal expansion joint, the bracket was crooked and replaced with oursRectangular non-metallic expansion jointThe problem is solved directly.

2. Temperature resistance and corrosion resistance: What working conditions must it be?

Strong acid and alkali corrosion and ultra-high temperature flue gas. But nonmetallic waveform compensators happen to play in both fields. From our stationRectangular non-metallic expansion joint、rubber compensator、Rubber PTFE compensatorAll are targeted designs: the outer layer is made of polytetrafluoroethylene (PTFE) or special fluororubber as an anti-corrosion barrier, and the inner layer is made of ceramic fiber or aluminum silicate cotton as heat insulation. The long-term temperature resistance can be above 1000℃ (such as the smoke duct of power plants).

There is a customer in the cement industry. The temperature of the flue gas at the tail of their kiln fluctuates greatly, and it also contains sulfur. The metal expansion joint is perforated in one year. Replace it with oursMetal Corrugated Expansion Joints in Cement Industry？ Of course, it works, but the cost is high-later, non-metallic expansion joints were used, which saved half the cost and prolonged the life. The principle is simple: the non-metallic material itself is corrosion resistant and does not produce stress corrosion cracking.

3. Displacement compensation ability: large displacement and multi-direction are its home field

Metal expansion joints are usually good at axial displacement, while lateral and angular displacement depend on complex structures (such as compound hinge type and universal type). What about non-metallic waveform compensators? It is itself a piece of "soft connection" that can absorb axial, lateral and angular displacements simultaneously-as long as the structure is properly designed. For example, ourRectangular non-metallic expansion jointIt is often used in rectangular flues of power plants and steel plants, and can compensate for the deviation in various directions caused by thermal expansion and contraction.

Moreover, its compensation amount can be made very large, and some can reach more than 100mm. To reach this amount, a metal expansion joint of the same size may have to be made into several waves or even with a tie rod. So you have to ask what is the biggest feature of non-metallic compensators? One word:soft。 It can resist large displacements and is not afraid of multiple directions.

4. Hidden advantages of installation and maintenance: light, easy to change, and not afraid of installing wrong

Everyone who does engineering knows that the fault tolerance rate of equipment installation is very important. Non-metallic waveform compensators are usually 30%-50% lighter than metal expansion joints of the same caliber, which can be moved by one person, and are convenient for on-site welding or flange connection. More importantly, in case the pre-stretching is not accurate during installation, or the pipeline deviates, the forced adjustment of the metal expansion joint may screw the bellows; The elasticity of non-metal is good, and it can still work if it is slightly biased.

And in our product structure, likerubber compensatorAndNon-metallic expansion jointThey are all modular designs, and the inner lining, insulation and outer cladding can even be replaced separately-which layer is broken and which layer is replaced without dismantling the whole pipe. Don't underestimate this. The maintenance window period of power plants is so short. It may take half a day to weld a metal expansion joint. Once the non-metal one is tightened with bolts, it will take half an hour to get it done.

5. The easiest pit to step on when selecting a model: don't treat non-metals as a panacea

Having said so many advantages, I have to pour some cold water. Non-metallic waveform compensators do not work everywhere. First of all, its pressure bearing capacity is inherently weak, and it is generally used in low-pressure systems (usually below 0.1MPa, and higher special designs can reach about 0.5MPa). If you are steam pipes, high pressure oil pipes, honestly choose metal- -like oursUniversal corrugated expansion jointOrHigh temperature axial expansion joint。

Secondly, the fatigue life of non-metallic compensators is not as good as that of metal bellows-the fabric layer always has an aging period, and the general design life in the industry is 10-15 years, while the metal expansion joint can reach more than 20 years under ideal working conditions. In addition, some media contain hard particles (such as pneumatic ash transportation pipelines), and high-speed scour will wear the fabric. At this time, wear-resistant lining or direct metal has to be added. To sum up: When selecting the model, see the four parameters of pressure, temperature, medium and displacement clearly. Don't just listen to "non-metal is cheap" and use it indiscriminately. We have so many product lines in our station, fromNon-metallic expansion jointToHigh temperature axial expansion joint、Universal corrugated expansion joint, is to let you match on demand.

All right,What are the features of non-metallic waveform compensator?Simply put, it is: flexible structure, high-temperature corrosion resistance, multi-direction large displacement, worry-free installation and maintenance, but low pressure and limited life, so you must look at the working conditions when selecting the type. If you have a specific project on hand and aren't sure which one to use, feel free to flip through the product page on our site- -Rectangular non-metallic expansion joint、rubber compensator、Rubber PTFE compensatorThey all have detailed parameters, so just take your seat.