Specialized in manufacturing compensators, expansion joints, baffle doors

What is the price of non-metallic compensator? Find out what it is

What is the price of non-metallic compensator? Anyone who has been in the purchasing circle for several years has asked this sentence. But if you only focus on the quotes and compare the numbers, nine times out of ten you will step into a pit. To put it bluntly, the non-metallic compensator (also called fabric fiber expansion joint, rubber compensator) is not a standard screw, it is a customized flexible pipe fitting. It relies on glass fiber cloth, silicone cloth, polytetrafluoroethylene, fluororubber and other non-metallic materials to absorb the thermal displacement, vibration and noise of the pipeline.

Two days ago, I met a friend who was doing a flue gas desulfurization project, saying that the quotation ranged from several thousand to tens of thousands, and he was completely confused. In fact, the "value basis" of non-metallic compensator is hidden in its structure-ring belt, flange, insulation layer and sealing layer, each layer is a cost. Like what we always sayNon-metallic expansion joint (fabric fiber expansion joint)If the ring belt is coated with fluororubber, the price will be doubled directly; Made of ordinary silicone clothrubber compensatorIt's much cheaper. So don't cut fabric and fiber goods at the price of rubber, it's not the same thing.

The five elements are the vital gates of pricing, and the quotation sheet will not write them all

1. Material: Every layer of cloth is money

The outermost layer is corrosion-resistant fluororubber or polytetrafluoroethylene, the middle layer is glass fiber or ceramic fiber for reinforcement, and the inner layer may be high-temperature resistant aluminum silicate wool. And guess what? Compensators of the same size, with temperature resistance of 200℃ and temperature resistance of 1000℃, can have a cost difference of 3 times. OurHigh temperature axial expansion jointEven multiple layers of stainless steel wire mesh need to be sandwiched in the ring belt, and the price will naturally rise. And there's anotherPTFE compensatorPerfluorinated material is acid-and alkali-resistant, but it is difficult to process, and the unit price is close to that of metal parts.

2. Size: the bigger the more expensive, but not as linear as you think

The little guy with a diameter DN100 can do it for a few hundred bucks. But like the ones used in power plantsRectangular non-metallic expansion jointWith a side length of two or three meters or even larger, the light flange is thickened and the ring belt is widened, and the cost will rise exponentially. Moreover, rectangular parts are more material-consuming than round parts-if you taste it carefully, the same cross-sectional area, the rectangular circumference is longer, the amount of ring belt is more, and the mold fee is calculated separately. It is the norm that the price increases by 30% to 50% for each larger gear of size.

3. Working conditions: temperature, pressure, medium, one parameter and one pit

Working conditions are the deepest hidden cost assassins. Common air ducts, withRubber PTFE compensatorYou can handle it. However, if you encounter sulfur-containing flue gas, high-temperature steam, acid-alkali liquid, you have to change fluororubber coating or even full tetrafluorine lining. Pressure is also the key. Low pressure (below 0.1MPa) should be used with a single layer of ring belt, and medium pressure (0.1~0.5MPa) should be added with steel wire skeleton or even another layerUniversal corrugated expansion jointMetal mesh sleeve. Not to mention corrosive media – ourDesulfurization flue gas baffle doorWith the matching non-metallic compensator, the band must be resistant to SO₂ and chloride ions, which directly doubles the cost of this material.

4. Customized design: there is no "average price" for non-standard parts

Eighty percent of non-metallic compensators on the market are non-standard parts. For example, for smoke ducts in power plantsRectangular non-metallic expansion jointThe flange hole spacing, thickness and number of circle layers have to be according to the drawing. If you ask the manufacturer to change a size, open the mold, adjust the production line and change the blade, these hidden costs will be spread into the unit price. And something likeCompound hinge transverse expansion jointThe design with tie rod has high structural complexity and long processing period, so the price is naturally more expensive than the ordinary straight pipe type.

5. Installation and after-sales service: Free installation? never mind

Many quotations only quote the bare price. But think about it. When installing the non-metallic compensator, it is necessary to pre-stretch, adjust the parallelism of the flange and tighten the torque. If you don't pay attention, you will leak inside. OurElectric plug-in insulation doorThe matching compensator has to cooperate with the debugging sealing performance during installation. If the manufacturer packages installation, labor costs, travel expenses and hoisting expenses are added, it is not surprising that the price will rise by 20%. So don't just compare the bare price, ask clearly to the total price including installation in place.

Why are some non-metallic compensators more expensive than metal ones? Just take it apart and see

In the same project, the metal expansion joint was quoted at 10,000 yuan, while the non-metal one was quoted at 15,000 yuan. The first reaction is that the manufacturer is slaughtering you? Don't worry, just disassemble a non-metallic compensator and you'll understand. The core values of non-metallic compensators lie in "flexibility" and "corrosion resistance". Metal bellows are prone to stress corrosion cracking at high temperatures, whereas non-metallic bands consist of multiple layers of functional materials — such asSilicone cloth + ceramic fiber + PTFE film, each layer has a different role: heat insulation, sealing, and corrosion resistance. Moreover, the non-metallic compensator has no fatigue life limit (unlike metal bellows, which has cycle times), and the maintenance cost is low.

A power plant flue gas piping system, if usedStainless steel corrugated expansion joint, may corrode perforation in two or three years; Replace withNon-metallic expansion joint (fabric fiber expansion joint)Seven or eight years, no problem. If you calculate the general ledger, non-metals are more cost-effective. And something likeHigh temperature axial expansion jointThis specially designed non-metallic part, filled with heat-resistant fiber inside and covered with stainless steel mesh, has complicated processing technology and is no cheaper than metal parts.

How to avoid being pitted when purchasing? Three Practical Tips

Tip 1: Don't just look at the price, first see if the manufacturer has a "working condition confirmation sheet"
Regular manufacturers will confirm the medium temperature, pressure, corrosive components and displacement with you before placing an order. If the manufacturer comes up and quotes a fixed price, even without asking about the working conditions, 80% of them are fooling you with generic products. When we met a customer who said "just ordinary air", it actually turned out to be oily steam, and the ordinary rubber compensator bulged after three months.

Tip 2: Require to provide "three or more layers of band samples"
The ring belt is the vital gate of the non-metallic compensator. Good bands have high interlayer bonding strength and cannot be torn apart. You can ask the manufacturer to send a small circle band sample, take the blade to cut and see-if the layers are chipped, it is inferior quality goods. Also, check the flange material: the price difference between carbon steel and stainless steel is 3 times. Don't be confused by the low quotation of "carbon steel flange". Stainless steel or PTFE must be used when the working conditions are corrosive.

Tip 3: Ask about the warranty period and maintenance plan
Non-metallic compensators are most afraid of "leakage" (internal leakage). Be vigilant if the warranty period is less than 1 year. And if offset is found after installation, does the manufacturer provide on-site adjustment? One of our customers bought a compensator from a small factory. When it was installed, the tie rod was not adjusted properly, and it leaked after three months. The manufacturer didn't answer the phone. So before signing the contract, write "Installation Guide" into the terms.

You asked him, "How to ensure that the loop does not shrink at 800℃"? If the other party is hesitant, quickly substitute.

Want an accurate quote? Just have these four parameters ready

Stop sending "I want a non-metallic compensator" demands to manufacturers. If you give him these four parameters, he will make a quote in a second:

• Pipeline Media and TemperatureFor example, "flue gas, containing SO₂, the highest temperature is 650℃, and the long-term operation is 450℃".
• Design and test pressures: For example, "0.3 MPa, hydraulic pressure test 0.6 MPa".
• Nominal diameter of pipeline and connection mode: For example, "DN600, flange connection, flange standard HG/T 20592".
• Axial displacement, radial displacement and angular displacementFor example, "axial compensation amount ± 50 mm, transverse direction ± 20 mm".

If rectangular pipes are involved, add two more parameters: length-width dimensions and allowable deflection. With these, the manufacturer can match you with the most economical band structure (such as glass fiber or ceramic fiber, and whether to add stainless steel wire mesh), instead of directly quoting and estimating it higher. OurHigh temperature axial expansion jointAndRectangular non-metallic expansion jointAfter the customer provides the complete parameters, the quotation error can be controlled within 5%.

What is the price of non-metallic compensator? The key depends on how much you are willing to pay for reliability. Don't buy cheap supplies, customize when you need to customize. Remember, the loss of one shutdown is enough for you to buy ten compensators.

Take 10 minutes to figure out where the leak is

Hey, the metal expansion joint is leaking. This matter is big or small. But don't rush to dismantle it and replace it with a new one-take 10 minutes to determine the specific location and cause of the leak. And guess what? 90% of emergency replacements are actually wasted money.

Bellows body cracked, weld cracked, flange sealing surface leaked. The way to tell is simple: take a flashlight and see if the medium is seeping out of the corrugated folds, dripping out of the butt weld, or just popping out of the flange gasket. Different leakage points are handled in different ways. For example, if the sealing surface leaks caused by loose flange bolts, just tighten it diagonally with a wrench, without moving the expansion joint itself at all.

The first thing after discovering a leak: emergency isolation, don't blindly block

When a leak occurs, the first reaction is often to "plug it quickly". But it is very risky to plug leaks under pressure. What circumstances can be welded? What circumstances must be downtime? Let me tell you a practical case: a customer of a home appliance station had a pinhole-sized trachoma on the bellows of a high-temperature axial expansion joint. They wanted to spot weld it, but as a result, after a dozen welding arcs, the bellows was directly torn by stress concentration, and the whole pipeline was forced to shut down for two days. Loss or not?

If the medium is water, steam or low-pressure gas, the leakage point is less than 2mm and the corrugated pipe is made of austenitic stainless steel, it can be temporarily treated with a pressure plugging fixture. However, if the medium is high-temperature flue gas, corrosive gas, or the pressure exceeds 0.5MPa, the machine must be stopped and relieved before operation. Remember, safety always comes first, don't lose the whole system just to save half an hour of downtime.

Partial repair or overall replacement? Look at three conditions

After figuring out the leakage, the next step is to decide whether to repair or replace it. There are three bases for judgment: leakage location, severity and medium working condition.

• Local perforation of bellows: If the diameter of the perforation does not exceed 5mm, and there is no obvious thinning and fatigue crack in the surrounding metal, stainless steel can be used for repair welding. However, note that the oil stain and oxide scale must be cleaned before repair welding, and the welding electrode should be made of stainless steel welding electrode of the same grade as the base metal. After welding, local heat treatment should be done to relieve stress. Hey, there is a threshold for this job. It is recommended to find a professional welder to do it.
• Weld cracking: If the circumferential weld or longitudinal weld is cracked, it is basically impossible to repair it. Because the weld is the weakest link of the expansion joint, the heat affected zone will embrittle again after repair welding, and it will crack before long. In this case, just replace it with a new one.
• Under what circumstances must I replace it with a new one?— — When corrugated pipes have large-scale corrosion thinning, fatigue cracks (for example, metal hoses have been used for more than ten years), or the medium temperature exceeds 550℃ (for example, corrugated expansion joints used in power station industry run at high temperature for a long time), at this time, repair welding is to treat the symptoms but not the root cause. Especially for general-purpose corrugated expansion joints and high-temperature axial expansion joints, the specific fatigue life has been considered when designing, and the risk of overdue service is extremely great.

Don't step on the pit when changing the model: Why is it faster to change the same model?

Many customers think that if it is broken, they will buy the exact same one and replace it, which will save trouble. And the result? It leaked again after less than half a year of use. Why? Because the working conditions have changed!

Your original pipeline was hot water at 80℃, but later it was replaced by steam at 160℃. The general-purpose corrugated expansion joint of the same model is made of 304 stainless steel, and the upper temperature resistance limit is about 450℃, but the pressure resistance grade is different. The allowable stress of stainless steel will decrease at high temperature. If the displacement has not changed, the stress bearing by the bellows will exceed the standard. This is the reason why changing to the same model will break faster.

Therefore, when changing the selection, three parameters must be recalculated:Medium temperature, working pressure, pipeline thermal displacement。 In addition, you have to consider the accessory configuration: for example, is the guide tube intact? The function of the guide tube is to divert the medium and prevent high-speed erosion. If the guide tube is corroded and broken, the newly replaced bellows will soon leak due to erosion. In addition, how to adjust the tie rod nut? The function of the expansion joint tie rod is to limit the over-stretching or over-compression of the bellows. Before installation, the nut position should be pre-adjusted according to the design requirements (refer to the "How to adjust the expansion joint tie rod nut" we talked about earlier). Omitting these details is equivalent to laying mines in the new expansion joint.

Routine maintenance is ten times worry-free than post-event remediation

Having said so much emergency treatment before, in fact, what I want to emphasize most is: don't wait for it to leak before repairing it. If routine maintenance is in place, the probability of leakage can be reduced by 80%.

• Installation phase:Make sure to pre-stretch or pre-compress the metal expansion joint when installing it (depending on the type you buy). For example, the directly buried expansion joint is installed directly without pre-compression. As soon as the pipeline heats up, it begins to "grab the stroke", and the bellows quickly fatigues. Don't ask why, it's common sense in mechanics.
• Inspection of pipe supports and hangers:Many leaks are not a problem with the expansion joint itself, but rather a sinking of the pipe support or a loose thrust frame, causing the expansion joint to take extra thrust that it shouldn't have. It is more effective to inspect the hanger once a month than to stare at the bellows.
• Regular inspection of bellows appearance:Use the naked eye or magnifying glass to see the corrugated surface for corrosion pits, scratches and cracks. For corrugated pipes matched with high temperature axial expansion joints or flue gas baffle doors, it is recommended to permeation test (PT) every six months, and the remaining life of micro-cracks is assessed immediately.
• Log the run log:Write down temperature changes, pressure fluctuations, and vibration data for each start and stop. Hey, no one looks at these data at ordinary times, but once leaked, it is the most important basis for you to judge the cause of failure.

After all, what to do with a leaking metal expansion joint? Not by one-time "divine operation", but by daily careful maintenance and scientific selection. I hope this article will help you avoid detours.

1. Let's start with "non-metallic expansion joint"-what is an oversized non-metallic compensator?

To put it bluntly, the non-metallic compensator is what we often call the non-metallic expansion joint. The industry standard is calledNon-metallic expansion joints (fabric fiber expansion joints)For details, please refer to JB/T 12235-2015. How do you understand the word "oversized"? Usually refers to compensators with rectangular or circular cross-sections with a diameter of more than 1 meter or even larger. For example, the flue duct and desulfurization tower of thermal power plants are used for inlet and outletRectangular non-metallic expansion jointThe diameter is more than 3 meters ×5 meters at every turn. The main body of this type of product is not a metal bellows, but a combination of high-temperature resistant fabric skin, thermal insulation filling layer and metal frame. Its ability to compensate for displacement does not depend on corrugation deformation, but all depends on the flexibility of the skin and the sliding structure of the frame-to put it bluntly, "soft connection".

2. Compared with the metal compensator, what is the advantage?

Metal expansion joints (e.g.Universal corrugated expansion joint) It is indeed reliable on high-pressure and high-temperature steam pipelines, but when faced with high-temperature flue gas and corrosive media (such as wet flue gas after desulfurization), metal bellows are easily corroded or fatigue cracked. The advantages of super-large non-metallic compensators are precisely:

• Corrosion resistance-The fabric skin material is usually fluororubber, silicone rubber or polytetrafluoroethylene coated cloth, which is easy to deal with SO₂ and acid-base droplets;
• Large compensation displacement-It can absorb axial, transverse and angular displacements simultaneously, and does not produce metal fatigue problems;
• Light structure— — Large-size metal expansion joints are not only expensive, but also scary in weight. Only the frame of non-metal models is metal, and the overall weight can be saved by more than half.

Two days ago, I met a cement factory customer. The high-temperature fan pipeline at the end of the kiln was originally usedMetal rectangular expansion jointAfter less than a year of use, the air leaked. After replacing it with a rectangular non-metallic expansion joint, there was no problem for three years. Do you think it's irritating?

3. How to choose the site? Don't step on these pits.

The most common mistake to make when selecting a model is to only look at the caliber regardless of the medium temperature and pressure. The working temperature of super-large non-metallic compensator is generally limited by the skin. Ordinary silicone cloth can withstand the temperature of 150~200℃, and Teflon cloth can reach about 250℃. If it exceeds 250℃, ceramic fiber insulation layer has to be added. In terms of pressure, it basically does not exceed 0.1MPa, so it is only used on low-pressure pipes. In addition, the installation direction is also particular-many construction teams try to save trouble, lock the tie rod or install the guide tube backwards, and as a result, the compensator can't play a role. Remember:The guide tube is to be directed toward that direction of the medium flowThe tie rod nut must be loosened by a certain stroke after installation, otherwise it will be a dead knot. What about that? It is right to pull the skin with your hand after installation, and you can feel the looseness.

4. Which industries can't live without it?

Super-large non-metallic compensators are needed for the pipes in front and behind the boiler flue duct and the desulfurization flue gas baffle door. Although the temperature of the flue gas after desulfurization is only 50~80℃, the humidity is high and it contains acidic condensate, which will soon rot with a metal compensator. It is usually accompanied hereDesulfurization flue gas baffle doorUse it together. Cement industry: kiln tail preheater, dust collector import and export, high temperature (350℃ +), large dust, rectangular non-metallic expansion joint with wear-resistant lining can carry. The sintering machine and pellet shaft furnace flue gas pipeline in the steel industry are similar scenes. In additionDouble hinge expansion joint for air-cooled island vacuum pipelineThese kinds of special custom structures are used occasionally, but that's another way to play.

5. Routine maintenance-don't wait until you miss it.

The weakness of non-metallic compensators is skin aging. Under normal working conditions, the fabric skin can be used for 3~5 years, but if the environment is bad, it may be changed in 2 years. Usually, the inspection should keep an eye on the skin surface for bulging, cracking or leakage marks. If local damage is found, you can use high-temperature repair tape for temporary emergency, but it is best to replace the whole piece. In addition, the frame bolts must be tightened regularly-pipe vibration will cause the bolts to loosen and then the skin will be torn. By the way: Don't forget to remove the insulation cotton in the old skin when replacing it. The new cotton should be compressed evenly, otherwise the compensation amount will be discounted. Don't ask me how I know, anyone who has suffered a loss knows.

Why are non-metallic compensators almost all custom made?

Simply put, the standard is simply not enough. Think about it, the flue gas temperature in the flue of the power station is always five or six hundred degrees, the medium at the tail of the cement kiln is still corrosive, and the pipe sizes at the inlet and outlet of the desulfurization tower are even more varied-round, square and special-shaped. If you look through the JB/T 12235-2015 standard, you will understand that this standard only stipulates technical requirements, test methods and inspection rules, and the size and shape are not limited at all. Therefore, non-metallic compensators (that is, we often call non-metallic expansion joints) are born custom parts.

"Can you buy a spot install?" I said that if you are not afraid of air leakage or short life, you can try it. But to be honest, the on-site flange spacing, medium temperature and displacement all don't match, and the spot stock will have to be scrapped if it can't last a maintenance cycle. Do you think the money was spent unjustly?

What are the key parameters?

Let's talk about the size first-circle, rectangle and special shape can be made. Like this site'sRectangular non-metallic expansion jointIt is specially equipped with rectangular pipes. More flexible material: silicone cloth, fluorine tape and PTFE film can be selected for the fabric fiber layer, and the temperature range is from-40℃ to 1000℃ full coverage. Whether the inner filling layer is ceramic fiber or rock wool depends on the temperature resistance and heat insulation requirements. There is also structural customization: Do you want a deflector? Do you want to bring a flapper door? For example, this site'srubber compensatorAndRubber PTFE compensatorOne is flexible and the other is corrosion-resistant. Where it is used depends on the working conditions.

By the way, stress levels are also key. 0.1MPa is sufficient for normal working conditions, but some vacuum pipes (such as air-cooled islands) need to be usedSpecial hose for vacuumThat kind of sealing structure, otherwise it will deflate when vacuumed.

The customization process is actually four steps

In the first step, you throw over the pipe parameters: diameter, medium, temperature (including long-term operating temperature and instantaneous maximum temperature), pressure, axial/transverse/angular displacement. In the second step, according to the parameter selection, we use the formula to calculate the stiffness and compensation amount-this can't be slapped on the head. Referring to the formula for calculating the stiffness of the expansion joint mentioned in the previous question and answer, we have to use the data to speak. The third step is to make drawings for you to confirm: the number of flange bolt holes, the length of the guide tube and the position of the tie rod are clearly marked. The fourth step is to do pressure test and displacement test before the production leaves the factory to ensure no leakage.

The whole cycle is fast one week, and the slow one is determined according to the complexity. Such as matchingDouble-sealed round flapper doorOrElectric plug-in insulation doorThis kind of assembly will take longer, after all, it needs to be linked to test.

Customizing the three easiest pits to step on

The first pit: only report the temperature but not the instantaneous maximum temperature.There is a customer of a power plant whose flue gas is usually 300℃, so he chose ordinary silicone cloth. As a result, the temperature rushed to 500℃ when starting and stopping, and the silicone cloth directly burned through the end of a pot. Remember that instantaneous temperatures can be twice as high as long-term temperatures, and material selection must be counted as peak values.

The second pit: ignore installation space.The flange spacing at the site is small, the compression amount of the non-metallic compensator is not enough, and it will die when installed, and the displacement will all be converted into pipeline stress, and the weld will crack. Therefore, we must measure the flange spacing before customization to leave a margin for pre-compression.

The third pit: forgetting to consider particulate matter in the medium.If the smoke is dusty, the fabric layer will be worn out quickly. What to do? The guide tube must be thickened or welded with cemented carbide. We have encountered customers in the cement industry who did not add deflectors and changed them twice in three months. Later, it was changed to a guide tube with surfacing layer, which took two and a half years. These problems are particularly common in power station industry and cement industry projects, and we have dealt with them too many times.

How is it used in the industry?

Power station boiler outlet, forHigh temperature axial expansion jointCombined with rectangular non-metallic expansion joint, it absorbs three-way displacement-think about it, when the boiler starts and stops, the pipeline expands thermally, contracts coldly and vibrates, and the metal bellows alone can't bear it at all. The flue gas pipeline at the tail of the rotary kiln in the cement industry has frequent heat exchange, and the fabric fiber expansion joint is the most reliable because of its strong vibration absorption ability. In the desulfurization system,Flue gas baffle doorAndDesulfurization flue gas baffle doorSupporting use-baffle door to isolate smoke, non-metal expansion joint to compensate displacement, both do not delay.

And vacuum pipes, such as air-cooled islands, have to be usedDouble hinge expansion joint for air-cooled island vacuum pipelineThat structure can withstand negative pressure while also absorbing angular displacement. Each industry has its own set of customized logic. To put it bluntly, it is to translate the working condition parameters into materials and structures-the medium temperature determines the fiber layer, the particulate matter determines the guide tube, and the pressure determines the sealing structure.

Do non-metallic compensators support customization? Of course it is supported, and it has to be customized. If anyone tells you to "buy the spot", you have to be more careful-80% of them have never touched the pit of high-temperature dusty pipes.

A non-metallic compensator is a skin? Stop mixing up!

Is a non-metallic compensator a skin? If you go to the maintenance site and ask around, eight out of ten old masters may point to the layer of cloth and say, "Isn't this the skin?" But if you understand it this way, then the procurement and design links will lead to a big mess. Today, let's get this straight.

Find out one thing first: What exactly is a non-metallic compensator?

Start with the product name. Non-metallic compensators, also known asNon-metallic expansion joint、Fabric fiber expansion jointDefinitely not a single layer of fabric. It is a set of multi-layer composite flexible pipeline compensation device, which is specially used to absorb thermal displacement, reduce vibration and noise. To put it bluntly, it is a "system", not a "part". If you just take a skin to replace it, that's called changing the coat, not the compensator.

Two days ago, I met a customer, and urgently called and asked, "Your non-metallic compensator, if the skin is broken, can you only change the cloth?" I said yes, but I have to find out which layer you changed first. He was stunned: "Isn't it just a layer of skin?" – you see, this is the typical misconception.

Take it apart to see the interior

Take a complete non-metallic compensator apart, and you'll find something inside:

• outer layer: Skin (temperature-resistant and corrosion-resistant fabric layer), which is the "skin" that everyone is most familiar with.
• intermediate: Heat insulating cotton, sealing film. Insulating cotton is responsible for blocking high temperature, and sealing film prevents smoke from leaking out.
• inner layer: Wire mesh, flange frame. Wire mesh is used to enhance overall strength, and flanged frames are responsible for hard connections to pipes.

So, the skin is just the outermost layer of "skin", which is equivalent to a coat. There are also cotton-padded jackets, underwear and skeletons inside. When you say a person wears a down jacket, can you say that a down jacket is a person? A truth.

Function of skin and material selection

Temperature, corrosion, aging. Common materials are silicone rubber, fluororubber, PTFE fabric. The material selection must be based on the working conditions:

• Silicone rubber skin: Temperature resistance around 200℃, suitable for general smoke environment.
• Fluorine rubber skin: Temperature resistance 250-300℃, acid and alkali resistance, commonly used in desulfurization system.
• PTFE fabric: Higher temperature resistance, extremely strong corrosion resistance, but also expensive.

However, it is easy to cause problems by changing the skin without changing the overall structure. Take a real case: a power plant only changed the skin, and did not check whether the insulation cotton in the middle was hardened. As a result, after three months of operation, the internal insulation failed, the outer flange was baked and deformed at high temperature, and the whole set of equipment was scrapped. You say it's a pity or not?

Non-Metallic Compensator vs Skin: Don't Confuse It

The compensator is a complete set of components, including the frame, guide tube, insulation cotton, bead, bolts, and so on. The skin is just a replaceable consumable in it. It is true that only the skin can be changed when replacing, but the design selection must be based on the overall performance.

For example, you bought aRectangular non-metallic expansion jointThen its compensation amount, temperature resistance grade and pressure grade are all calculated for the whole structure. Looking at the skin thickness alone (such as 2mm or 3mm), the reference value is limited. Just like buying a car, you can't judge the performance of the whole car just by looking at the tire tread thickness, can you?

Why do people often call it wrong?

Because the repair site often only changes the skin. Over time, everyone thought that "compensator = skin". In addition, many small manufacturers sell skin as a standard product, and writing "skin compensator" on the drawing deepens the misunderstanding.

In fact, we have bothNon-metallic expansion joint (fabric fiber expansion joint)This typical representative, there are alsorubber compensator、Rubber PTFE compensatorAnd other variants, but their core advantages are in multilayer composite structures. Single-layer skin simply can't withstand the high-temperature and high-pressure smoke erosion.

Purchase recommendations

Don't just focus on the thickness and material of the skin, ask these points clearly:

• Insulation thickness: At least 50 mm or more, otherwise the heat bridge effect will burn out the flange.
• Frame Material: Carbon steel or stainless steel? Is the surface anti-corrosion treatment done?
• Installation dimensions: The flange bolt hole distance and the pipe center are high, all of which can't be wrong.

Standard referenceJB/T 12235-2015。 The overall temperature resistance and compensation amount are the key indicators. For example, if your working temperature is 400℃, you can't just look at the nominal 450℃ of the skin and place an order. You have to confirm whether the heat insulation layer and the sealing film can match.

If the next time someone asks "Is a non-metallic compensator a skin?", you can ask him rhetorically: "Then do you think people are clothes?"-this analogy is rough, but not rough.