Specialized in manufacturing compensators, expansion joints, baffle doors

1. Is the current market cold or hot? — — Real voices on both sides of supply and demand

What is the market of desulfurization non-metallic compensator? This question, I just talked with the purchase of several desulfurization projects last week. To be honest, the market is not simply cold or hot now, but sharply differentiated.

Look at the demand side first. In the final stage of ultra-low emission transformation of domestic thermal power, steel and cement industries, there are indeed fewer replacement parts for old projects, but what about new projects? In coking, chemical and waste incineration industries, desulfurization systems are still being launched. Especially for some central heating projects in industrial parks, the standard equipment of flue gas desulfurization is non-metallic compensator. From the inquiry volume, the first half of this year increased by about 15% compared with the same period of last year-mainly supported by small and medium-sized projects.

Look at the supply side again. Small and medium-sized compensator manufacturers are having a hard time. The price increase of raw materials is on the one hand, and more importantly, the payment cycle has been extended to 6 months or even one year, and many factories dare not take big orders. However, the head enterprises are expanding production instead, because end users are becoming more and more picky: not any non-metallic expansion joint can be exported to the desulfurization tower.

So you have to ask whether the market is hot or cold? For manufacturers who can come up with the new national standard and have actual operating performance, the order is scheduled for three months; For factories that are still making up numbers with old fabric fibers, they can only rely on low prices to grab bulk orders, and their profits are as thin as paper.

Second, driven by the policy, what hard indicators does the desulfurization system put forward for non-metallic compensators?

The environmental protection policy has not been loosened in recent years. In 2023, the Ministry of Ecology and Environment revised the Air Pollutant Emission Standard for Thermal Power Plants, which directly forced the upgrading of the desulfurization system. What used to be made do with metal expansion joints is now required to be replaced with non-metallic ones-for a simple reason: corrosion resistance, zero leakage, and the ability to absorb multidimensional displacement.

• Temperature resistance class must be defined: The temperature of the original flue gas side of desulfurization is generally 120~160℃, but it may rush above 200℃ when encountering bypass conditions. The skin of the non-metallic compensator (that is, the fabric fiber layer) must give a third-party inspection report to prove that it will not fail after continuous operation for 10,000 hours at the set temperature. Don't trust the manufacturer's verbal promise, ask for paper documents.
• Sealability Requirements: The new design code requires a compensator leak rate of less than 0.1%. By what? Multi-layer construction + fluororubber sealing layer. Like the one in our stationNon-metallic expansion joint (fabric fiber expansion joint)It is made of fluororubber, polytetrafluoroethylene and glass fiber fabric, and is sealed in three layers. Before leaving the factory, air tightness test is done one by one.
• Anti-corrosion requirements: The wet flue gas after desulfurization contains acidic condensate water, and the pH value can be as low as 2. If the interior of the compensator uses a carbon steel frame, it must be lined or enameled to a high standard. Some projects specify stainless steel frames lined with PTFE, which is costly but long-lasting.

These hard indicators directly determine the difference in procurement cost by more than 30%. But there is no way, the acceptance fails, and rework is more expensive.

Third, buy it or buy a metal expansion joint? — — The irreplaceability of non-metallic compensators in desulfurization scenarios

Why don't metal corrugated expansion joints be used directly for desulfurization flue? It is cheap and has a high pressure resistance.

Alas, I've seen this pit too many times. The diameter of the desulfurization flue pipe is large (DN1000~ DN4000 is very common), and it is low pressure (usually below 0.1MPa) and large displacement (axial energy reaches 50mm and transverse energy is more than 20mm). The metal corrugated expansion joint has two dead points under this working condition: First, the thrust is huge, and the pipe support can't stand it; Second, it is easy to crack by stress corrosion-the bellows has a thin wall, and it will crack in a few months as soon as chloride ions come.

The flexible structure can almost neglect the thrust on the pipeline; The multilayered laminated fabric fibers are inherently not afraid of dilute acids; But also can simultaneously absorb axial, transverse and angular displacement. More importantly, its noise reduction effect is incomparable to metal parts.

In the desulfurization project of sintering machine in a steel mill, the original design used metal rectangular expansion joint. After half a year of operation, it was found that the weld seam frequently leaked. Later replaced withRectangular non-metallic expansion jointNever had any problems. This is not to say that the metal expansion joint is bad, it is used in the wrong place. Desulfurization scenario, non-metal is just needed.

IV. Behind price fluctuations: Who is at work with raw materials, processing cycle and project account period?

In the last two months, the price of fluororubber has increased by 20%, and so has PTFE. These are the main raw materials for the compensator skin. Aluminum silicate fiber cotton is stable, but the labor cost is high-the daily salary of a good skin master is almost catching up with that of an engineer.

The processing cycle is another variable. The standard cycle of custom parts is 30~45 days from blanking to factory. However, if you require the frame to be hot-dipped zinc for corrosion protection, or the skin requires imported fluororubber (such as DuPont's Viton), the cycle will be directly stretched to more than 60 days. In case of a project that rushes to the deadline, the manufacturer's expedited fee can eat 5% of the profit.

Then there is the accounting period. The industry practice is "3-3-3-1": 30% for advance payment, 30% before delivery, 30% after installation and commissioning, and 10% after expiration of warranty. However, many owners delay the payment until after acceptance, and even settle it with acceptance bills. When manufacturers' cash flow is tight, they will either increase prices or degrade quality.

So when you see a 20% difference between the two quotes, don't rush to pick the cheaper one. First ask clearly: Is there any difference in raw material batches? How long is the processing cycle? How to negotiate payment terms? These things are the essence of price fluctuations.

5. A few honest words for purchasing and engineers: how to pick, how to test and how to save

Something dry at last. What is the market of desulfurization non-metallic compensator? Quotes are dead, people are alive. If you master the following points, you will be able to step less on pitfalls:

How to pick?

First, confirm the working condition parameters: temperature, pressure, displacement amount, and medium composition. Don't just give a caliber and ask the manufacturer to quote. Second, manufacturers are required to provide running cases of the same type of projects, preferably in the past two years.

How to test?

When the goods arrive on site, don't just look at the appearance. Cut a small piece of skin sample and burn it with a lighter: real fluororubber flame retardant, self-extinguishing from fire; The counterfeit ones will drip oil and emit black smoke. Put the compensator flat and measure the difference of diagonal length. If the difference exceeds 3mm, the welding deformation exceeds the standard. Also, check the gap between the guide tube and the bellows, not less than 20mm, otherwise it will be damaged by friction after operation.

How to save?

Don't think about saving money on materials – all the money saved will turn into repair costs. The real way to save money is to choose a standard sizeNon-metallic expansion jointAvoid non-standard customization. In addition,Desulfurization flue gas baffle doorPackaging and purchasing with the compensator can often negotiate discounts. Finally, sign a warranty agreement with a reliable manufacturer: if it is damaged by people during the warranty period, it will be replaced for free. That's a lot more practical than the 5% of your hard-earned money you save.

What is the market of desulfurization non-metallic compensator? In the final analysis, the market is not good or bad in the total market volume, but in how professional you are. Think about this industry thoroughly, and you can deal with it calmly no matter the ups and downs.

What is a non-metallic compensator unit? Understand these parameters, selection is no longer confused

Two days ago, a customer came over with drawings and said, "I want a DN500 non-metallic compensator with a compensation amount of 300". When we looked at it, the pressure was written "6", and there was no unit. When asked later, he thought it was 6 kilograms, but the actual requirement was 0.6 MPa. By an order of magnitude, the fabric layer will bulge or even tear if done at 6kg. You see, just one unit didn't write it clearly and almost scrapped a piece of equipment. So today, let's thoroughly understand "what is the non-metallic compensator unit".

Direct answer: What units exactly do non-metallic compensators use?

Customers often ask "What is the unit of non-metallic compensator?" Actually, they ask two meanings: one is what to measure the product size (such as diameter DN and length mm), and the other is what to measure the compensation ability (such as displacement mm and pressure MPa). Simply put, common units are:

• Diameter:DN (nominal diameter), such as DN100 and DN200, but it is not the actual inner diameter, so you have to look up the table. This site'sNon-metallic expansion joint (fabric fiber expansion joint)In the product parameters, DN corresponds to the flange connection size.
• Compensation amount:Millimeters (mm), and transverse, axial and angular displacements are all in mm or degrees (°). Note: Although the angular displacement is degree, the rectangular expansion joint is sometimes marked with the angular displacement, which is actually the flange deflection angle.
• Pressure:Megapascals (MPa), occasionally with kilogram force (kgf/cm²), 1 MPa ≈ 10.2 kgf/cm². The old drawings say "6K" and "10K" are Japanese standards, 1K ≈ 0.098 MPa, so don't get confused.
• Temperature:degrees Celsius (℃), the upper temperature resistance limit of non-metallic fabric compensator is usually between 200 and 1200 ℃, depending on silicone cloth, fluorine tape or ceramic fiber. For example, the temperature resistance of ceramic fiber is 1260℃, but the long-term work can only reach 1000℃-if the unit is wrong, the equipment will be scrapped in three months.
• Overall Dimensions:The length, width and height are all in mm,Rectangular non-metallic expansion jointIt is also divided into inner diameter, outer diameter and flange hole pitch. On the drawing, both L and B are mm, and the diameter of the center circle of the flange bolt hole must also be in mm.

When you select the model, these units are marked on the manufacturer's drawings. Don't regard DN as inches or kgf/cm² as MPa. Is that the truth?

Why is the compensator destroyed when the unit is wrong?

• Nominal pressure:PN6, PN10 and PN16 (unit bar or MPa) are commonly used in national standards, but "6K" and "10K" written on the old drawings are Japanese standards, and 1K ≈ 0.098 MPa. I have seen a purchase, holding the drawing of PN10, and the default is 10kgf/cm² (about 0.98MPa). As a result, the supplier does it according to 1.0MPa. The understanding on both sides is actually similar, but if it is higher, there will be problems. In fact, the national standard PN unit is bar, 1 bar =0.1 MPa, and PN10=1.0 MPa.
• Displacement Amount:Axial compression and tension are used in mm, transverse displacement is also used in mm, but angular displacement is used in degree. Rectangular expansion joints are sometimes marked with angular displacement, which is actually the flange deflection angle. For example, you require ±50mm, which is actually determined by the number of folds of the multi-layer fiber cloth. If you need 100mm, you have to widen the folds or increase the number of layers, but the pressure loss will also change.
• Installation Length:Includes flange thickness and compensator effective length in mm. On the drawings of products in the station, such as "rectangular non-metallic expansion joint", L and B are both mm.

So how to avoid it? A suggestion for not rolling over: When confirming with the supplier, write all the units clearly, such as "installation length 300mm, axial compensation amount ±50mm, working pressure 0.1MPa, medium temperature 350℃". Don't come up and throw a number, people can't guess your mind.

What is the difference between the units of non-metallic compensators and metallic compensators?

Some people think that the difference is not big, but in fact, the emphasis is different. Metal expansion joints (e.g.Universal corrugated expansion joint、Direct buried (fully buried) type expansion joint) is more concerned about the pressure grade and the number of ripples, and the units are mainly MPa and wave number. The core of non-metal compensator (also called fabric fiber expansion joint) is temperature resistance and corrosion protection, so the temperature unit (℃) and acid-base concentration (%) are more important.

Used in the cement industryMetal Corrugated Expansion Joints in Cement IndustryMainly cope with high-temperature dust, the pressure is not high, but the temperature may reach 800℃. WhileNon-metallic expansion joint (fabric fiber expansion joint)In the desulfurization flue gas baffle door system, to withstand the acid gas after wet desulfurization, "SO₂ concentration ppm" has to be added to the unit at this time. And guess what? Many purchases only focus on pressure units, ignoring whether the unit marked by the upper temperature limit is long-term operating temperature or instantaneous peak. For example, the high-temperature axial expansion joint is specially designed for power stations, and the temperature is marked accurately to ℃. However, if it is an export order, Fahrenheit (℉) should also be careful-1000°F ≈ 538℃. If it is used as 500℃, the fabric layer will be carbonized.

Three unit pits that are easiest to step on during model selection

Pit 1: Nominal diameter DN ≠ outer diameter of flange.The rectangular non-metallic expansion joint of DN200 has an inner diameter of 200mm, but the diameter of the center circle of the flange bolt hole may be 240mm. If you fit the pipe according to the outer diameter of the flange, it can't be installed. So you must look at it when choosing a modelRectangular non-metallic expansion jointDrawings, mark the flange hole spacing clearly.

Pit 2: The conversion of pressure units is reversed.A customer said "I want PN10", and the supplier defaulted to 1.0MPa, which the customer understood as 10kgf/cm² (about 0.98MPa). The result was similar, but a higher level would cause problems. In fact, the national standard PN unit is bar, 1 bar =0.1 MPa, and PN10=1.0 MPa. If you run into the daily standard "10K", that's another story.

Pit 3: "F" and "C" in the unit of temperature.Export orders are common degrees Fahrenheit (℉), 1000°F ≈ 538℃, if used as 500℃, the fabric layer is carbonized. On-site productsHigh temperature axial expansion jointDesigned for power stations, temperature labeling is accurate to ℃. So when you get the order, look at the unit first, and don't think inertially.

Contrast this site'sNational standard for non-metallic expansion joints(JB/T 12235-2015), which clearly specifies the parameter labeling requirements. Or call the manufacturer directly, don't guess for yourself.

One sentence summary: the unit is the compass of type selection, wrong all bias

The unit system of non-metallic compensator is not complicated, with diameter DN, compensation amount mm, pressure MPa, temperature ℃, plus a flange bolt hole distance mm. However, behind the value of each unit, there are different material layer thicknesses, wave heights and layer numbers. For example, the compensation amount of "non-metallic expansion joint (fabric fiber expansion joint)" is labeled ±50 mm, which is actually determined by the number of wrinkles of the multilayer fiber cloth. If you need 100mm, you have to widen the folds or increase the number of layers, but the pressure loss will also change.

Next time, ask "What is the non-metallic compensator unit?" First, turn through the product page of this site. The four fields of "nominal diameter, displacement, working pressure and working temperature" in the product parameter table are the answer. If you don't understand, just copy the parameters and send them, and we will help you correct them. After all, after more than ten years in this business, I have seen too many cases of rework because of mistakes made by the unit-it is really not worth it.

Why do non-metallic compensators need regular maintenance? Structural characteristics and working environment determine its vulnerability

Non-metallic compensator, also called non-metallic expansion joint or fabric fiber expansion joint, mainly absorbs heat displacement, vibration and noise reduction in pipeline system. It consists of a flexible fabric layer, insulation layer, sealing layer and metal frame. This structure is inherently "tender" than metal bellows-the fabric layer is afraid of high temperature aging, acid and alkali corrosion, and mechanical scratching. What about the work environment? Desulfurization flue gas, hot air pipeline, cement kiln tail... are all working conditions with high temperature, dust and corrosive media. If you think about it, it would be strange if you were burned by smoke and fire every day.

Two days ago, I met the equipment supervisor of a cement factory.Rectangular non-metallic expansion jointIt took two years to leave it alone. As a result, the smoke was directly sprayed out, and the production line stopped for three days. Replacing a compensator itself is not expensive, but the loss of downtime is hundreds of thousands a day. So don't wait for a leak to remember, regular maintenance is about spending a small amount to save a lot of money.

Daily inspection: see, listen and touch, find problems in three steps

You don't need any sophisticated instruments for daily inspections, just use your eyes, ears and hands well.

look

Stand at a safe distance and glance at the whole first. See if the fabric layers are bulging, cracking, delaminating? Is there any rust or deformation in the metal frame? Pay special attention to welds and connecting bolts – usually the first thing that goes wrong is a loose bolt, resulting in a loose seal. Also, see if the deflector (if any) has any signs of wear and tear from the media. You can flip through our previous articles for the specific function of the guide tube, which will not be expanded here.

Listen

A normal non-metallic compensator runs with little to no sound. If you hear a "hiss" of air leakage, or a "click" of metal friction, it is 80% because the seal is broken or the frame is misaligned. Note when listening: Is it in a position with large displacement? For example, near the elbow and next to the fixed bracket.

Touch

After the machine is stopped (or with insulated gloves), touch the surface temperature of the fabric layer with your hand. If the local temperature is significantly higher than the surrounding temperature, it means that the internal insulation may collapse or break, and the heat is transferred directly to the external surface. Don't be careless at this time, the high temperature will accelerate the aging of the fabric, and it won't take long to leak.

Practical maintenance: cleaning, tightening and anti-corrosion, one cannot be missed

What to do after finding a minor problem? Three steps: clean, fasten, and prevent corrosion.

Cleaning: Use a soft brush or compressed air to clean up dust and scale on the surface of the compensator. It is strictly forbidden to scrape with a hard metal blade-once the fabric layer is scratched, it is the future leak point. If the medium is viscous (such as desulfurization slurry), rinse it with clean water and dry it before subsequent treatment.

fastening: Check all connecting bolts and tie rod nuts. Note: How to adjust the expansion joint tie rod nut? It's not that the tighter you screw it, the better. The function of the tie rod is to limit the excessive displacement and at the same time ensure the design compensation amount. If you tighten too tightly, it limits the normal displacement, and the pipe stress will transfer to the weak link. Standard practice: Pre-tighten to the design value and then lock the loose nut. You can refer to the manufacturer's installation instructions, or the Q&A of "The Function of Expansion Joint Tie Rod" we wrote before.

antisepticMetal frames, especially carbon steel, rust quickly in wet or corrosive environments. Find the corrosion spot, polish and remove rust first, and then apply temperature-resistant anti-corrosion paint twice. Pay attention to avoid the fabric layer, the lacquer will swell and harden when it touches the fabric, which is not worth the loss. For stainless steel frames (such asDesulfurization flue gas baffle doorMatching compensator), check pitting and stress corrosion cracks, if they appear, it will be a big trouble.

How to deal with common faults? Leakage, deformation, aging, right seat

Leakage, deformation, aging. It is handled differently.

leak: Confirm the leak location first. If it is on the fabric layer, the small hole can be temporarily treated with a special patch of repair glue (be careful to be temperature and pressure resistant). Don't mend the big tear, just change the components. If the leak is at the connection of the metal frame to the pipe, check that the seal gasket is damaged or that the flange surface is flat. Don't screw the bolts when you come up-if they are uneven, they won't seal them even if they break them.

deformation: Bulging of the fabric layer of the non-metallic compensator, usually due to collapse of the internal insulation, or the operating temperature exceeding the design value. At this time, you have to stop the machine and open it to check the insulation. Don't think about patching, the internal structure is broken and the external fabric won't last long. In addition, the deformation of the frame (such as the corner of the rectangular compensator tilting) is generally caused by excessive pipe thrust or installation deviation, so it is necessary to recalculate the pipe stress and adjust the bracket.

Aging: The fabric layer has a large area of cracking, hardening and loss of elasticity. Don't hesitate to change it directly. Aging compensators have a sharp decrease in strength and may burst at any time. To judge the degree of aging, you can pinch the edge of the fabric with your hand-if it breaks when pinched, it is "osteoporosis".

From the beginning of installation, it determines the ease of later maintenance

This view may be a little counter-intuitive, but the fact is: if you don't install it correctly, the maintenance behind you will exhaust you. There was a chemical factory before,Non-metallic compensatorIt was installed very close downstream of the pipe elbow, and as a result, the compensator was subjected to additional bending moment during operation, and six were replaced in three years. Normal installation considerations include:

• Ensure that the pipes on both sides of the compensator are coaxial and the deviation is within the allowable range (refer to the model and size table of the expansion joint).
• The installation direction should be correct: Pay attention to whether the medium flow direction is consistent with the direction of the arrow of the expansion joint, and the insulation layer will be blown askew if it is reversed.
• Temporary supports to be removed: Tie rods or supports may be installed for the convenience of transportation when leaving the factory, which must be removed after installation, otherwise the compensator will not work.
• Pre-stretching (or pre-compression): If it is cold installation, the compensator should be pre-adjusted according to the ambient temperature. See the design drawings for specific values. If it is not adjusted, the compensator will bear additional tensile stress when the temperature is low in winter.

Think about it, these details are done in place, and the post-maintenance workload is directly halved. Didn't do it? Then just wait to wipe your ass every few months.

When is it time to get a new one? Don't cause trouble just to save money

Many bosses think that "continue to use it if it can still be used", but the non-metallic compensator not only decreases in performance at the end of its life, but also may suddenly burst. Then when do you have to change?

First, achieve the designed service life.According to the national standard for non-metallic expansion joints (JB/T 12235-2015), the service life under normal working conditions is generally 3-5 years. If it is overrun, it is recommended to do regular water or air pressure tests, but don't expect it to last long.

Second, irreparable damage occurs.For example, large-area ablation of fabric layer, serious deformation of metal frame, cracking of weld seam, etc. Don't think about welding and repairing-once the structural integrity of the non-metallic compensator is destroyed, the reliability after repair is greatly reduced.

Third, there is no cure for leakage.Patched more than three times and still leaking? Don't worry about it, get a new one. The indirect cost of leak repair per shutdown is much higher than the cost of replacement. Don't count this account? Ask the cement factory in front.

By the way, when replacing a new one, it is recommended to check the pipe bracket and adjacent equipment (such as flue gas baffle door, electric plug-in insulation door, etc.) simultaneously. Often, the old compensator is broken because the pipe displacement exceeds the standard, and the root problem is not solved, so the new one dies early.

Don't wait for the smoke to remember. Look, listen, touch regularly, tighten what should be tight, clear what should be cleared, and change what should be changed. The non-metallic compensator is actually quite solid-as long as you have given it "due care".

"Does the non-metallic compensator do heat insulation? I see that the metal bellows next door are covered with a thick layer, so I'm afraid of something going wrong." This problem is actually quite typical-I have seen too many people want to insulate non-metallic compensators as soon as they come up, and as a result, they not only spend money in vain, but also destroy the compensators. Today, let's make it clear when to add it and when not to add it.

1. Find out what material the non-metallic compensator itself is made of first

Non-metallic compensator (also called non-metallic expansion joint, fabric fiber expansion joint), the main body is laminated by flexible composite materials such as silicone cloth, fluorine adhesive tape and glass fiber. To put it bluntly, it is itself a set of multi-layer insulation structures. The temperature resistance of ordinary silicone cloth can reach about 200℃, and that of fluorine tape can reach above 250℃. In many operating conditions, the temperature resistance margin of the skin itself is sufficient.

Then why do some people always think they need to add insulation? Because everyone's mind is all about metal corrugated expansion joints-such asCorrugated expansion joint for power station industryOrMetal Corrugated Expansion Joints in Cement IndustryThe metal shell conducts heat quickly and must be insulated to prevent scalding and save energy. However, the skin of the non-metallic compensator itself is a bad conductor of heat. If it is piled up blindly for heat preservation, it may flatten the ripples and hinder the displacement, and the compensator will be scrapped in advance.

2. Under what circumstances must non-metallic compensators be insulated?

You can't talk to death. Under some working conditions, it is really impossible not to do heat insulation. There are three scenarios:

• High temperature operating condition: The medium temperature exceeds the allowable long-term use temperature of the skin. For example, the temperature of flue gas pipe is 400℃, ordinary silicone cloth can only carry 200℃, and fluorine tape can only carry 250℃-at this time, an insulation layer must be added on the outside of the compensator to reduce the surface temperature of the skin.
• Low temperature operating condition: likeDouble hinge expansion joint for air-cooled island vacuum pipelineThe medium is cold, and the outer wall is prone to condensation or even ice. What is done at this time is to keep the cold, not keep the heat.
• Human body protection: likeDesulfurization flue gas baffle doorThe temperature of the nearby non-metallic compensator may be less than 100℃, but it is safer to add a detachable insulation sleeve to prevent scalding. The environmental inspection also recognizes this.

What is the medium temperature? How much is the skin material resistant to temperature? What is the ambient temperature? The difference is calculated before we do it.

3. If the insulation is not done correctly, the life of the compensator will be directly reduced by half

Tsk, I met a client two days ago.Rectangular non-metallic expansion jointIt was covered with a layer of hard rock wool and then reinforced with cement. And guess what? The compensator barely stretched freely and ripped in a few months. The core function of non-metallic compensator is to absorb displacement. What is the difference between wearing a hard shell on it and welding it to death?

The insulation material must be soft and compressible, such as aluminum silicate fiber blanket. And it can't be pressed too firmly, let alone the insulation material can be stuffed into the corrugated gap-that is equivalent to jamming all the movable joints of the compensator. Remember an iron rule: leave at least 10mm gap between the insulation layer and the compensator, or use a metal shell for movable connection.

4. Correct practice: layered design + detachable structure

The standard practice is divided into three steps, and one step less may overturn:

1. Moisture-proof insulation layer: Wrap a layer of aluminum foil or Teflon cloth outside the skin of the non-metallic compensator to prevent moisture penetration.
2. Flexible insulation layer: Lay aluminum silicate fiber blanket, the thickness is calculated according to the temperature difference, generally 50-100mm.
3. Protective shell: Use stainless steel or galvanized iron sheet as the shell, but it must be made into the style of two-half buckle and fixed with buckle-convenient for disassembly and assembly during maintenance, otherwise the whole insulation layer will be smashed next time you change the skin.

Some high temperature operating conditions, such as we giveHigh temperature axial expansion jointThe plan is to directly customize the non-metallic compensator with thermal insulation interlayer-the thermal insulation cotton is pre-installed between the skin and the protective net when it leaves the factory, and only the butt flange is needed on the site, thus saving the trouble of on-site construction. Is it much less worry-free?

5. In the final analysis, heat preservation is not the end, temperature control is

Judge whether the non-metallic compensator should be insulated or not. Don't just look at the name. First calculate three sets of numbers: medium temperature, ambient temperature, and allowable heat loss. For example, the temperature of the flue gas pipe is 400℃, and the non-metallic skin can only carry 250℃, so insulation must be added to reduce the skin surface below 200℃. However, if the flue gas temperature is only 150℃, the skin itself can cope with it, and adding thermal insulation is a pure waste of money.

In addition, the overall insulation design of the pipeline system must be considered. Non-metallic compensators are often the weak points in the whole insulation link-many projects age and leak in advance because the insulation is not done well, and finally the whole system has to be reworked. So, when you are unsure, directly ask the manufacturer for the temperature-pressure curve, which is much more reliable than guessing.

If you are still unsure, welcome to inquire. Our sideNon-metallic expansion joint (fabric fiber expansion joint)、Double hinge expansion joint for air-cooled island vacuum pipelineThey are all with detailed technical parameters, and you can know whether you should do heat insulation or not.

1. Why can high-temperature resistant non-metallic compensators withstand high temperatures? Materials are key

To be honest, when many people come into contact with this thing for the first time, their first reaction is: Can something made of fabric and rubber hold hundreds of degrees of high temperature? Don't worry, let's look at the materials first. High-temperature resistant non-metallic compensators usually adopt multi-layer composite structure, the core of which is the flexible fabric layer in the middle, such as silicone rubber coated glass fiber cloth, polytetrafluoroethylene film and ceramic fiber felt. Silicone rubber itself can withstand temperature to about 250°C, but with the addition of glass fiber and ceramic fiber, the working temperature is directly raised to 600°C or even above 1000°C. And guess what?"Non-metallic expansion joint (fabric fiber expansion joint)" mentioned in the product information of this siteThe more layers, the stronger the heat insulation and temperature resistance.

There is also a layer that is easily overlooked-the internal deflector. Many non-metallic compensators will be equipped with metal guide tubes, which not only guide the airflow to reduce erosion, but also block the high-temperature smoke from licking directly to the fabric surface. This thing is kind of like armor, minimizing the damage from heat radiation. So you see, the confidence of high temperature resistance is not blown out, but layered materials.

2. Temperature upper limit and pressure level: Don't just listen to propaganda, look at national standards and actual measurements

Some manufacturers in the market say that their products can carry 1200°C, but when you ask about the pressure level, they hesitate. According to the National Standard for Non-metallic Expansion Joints JB/T 12235-2015, the upper limit of working temperature of non-metallic compensator is related to the medium, pressure and displacement, not just by looking at the numbers. How do the measured data come from? Take a practical case: The outlet pipeline of the rotary kiln in a cement plant isRectangular non-metallic expansion jointWith a medium temperature of 850°C and a pressure of ±3kPa, the fabric loop belt was changed once after more than two years of continuous operation.

In terms of pressure, non-metallic compensators are naturally inferior to metal because of their flexible structure, so they are generally used in low-pressure flue duct systems (within 0.1MPa). But it has a unique skill: it can absorb multi-dimensional displacements (axial, radial and angular), and it has minimal thrust on the pipe. So don't use it as a pressure vessel, it's more like an elastic soft joint.

What about the performance of high temperature resistant non-metallic compensator? Bottom line: look at the working condition match. For scenarios below 600°C, low pressure, and large displacements, it is much more reliable than a metal compensator.

Third, just with the front of the metal compensator: who is more cost-effective and who is more durable?

Two days ago, I met a customer who insisted on using it on a 300°C flue.High temperature axial expansion jointI asked him why he didn't use non-metallic ones. He said he thought the metal was durable. As a result, the metal bellows should not only choose heat-resistant alloy steel (the cost doubles), but also consider the corrosion problem, and there are many welding points, which makes maintenance troublesome.

Under the same caliber, the price is generally only 1/3 to 1/2 of that of metal. More importantly, its installation accuracy requirements are low, and the on-site cutting adjustment is not distressed. Moreover, it is convenient to repair-if the fabric ring belt is broken, it can be replaced directly, unlike metal bellows that have to dismantle a bunch of flanges. What about longevity? Under normal working conditions (the temperature is lower than the design value, and the medium has no corrosion), the fabric layer can be used for 5-8 years, which is much longer than the fatigue life of metal bellows at high temperature.

But it's not without its flaws. Non-metallic compensators are afraid of sharp hard objects scratching, afraid of direct burning by open flame. So it fits flue gas, hot air, dust ducts, not steam ducts (unless specifically designed). When selecting a model,Product Center of this siteCompare the parameters well, and don't mess with the Mandarin Duck Spectrum.

4. Selection and rollover site: size, displacement and installation direction must not be missing

Let me tell you the truth. In order to save trouble, a steel mill bought a non-metallic compensator and installed it directly. As a result, the fabric burst after one week's operation. Why? The amount of displacement is not counted correctly! The thermal expansion length of the pipe is calculated to be 50mm, and the compensator they bought can only absorb 30mm, so it's weird that it doesn't burst.

Diameter (DN size), compensated displacement (axial/transverse/angular), operating temperature。 If one is missing, it can overturn. Such asRectangular non-metallic expansion jointIt is used on rectangular flue. When installing, it should be noted that the direction of the guide tube must be consistent with the flow direction of the medium, otherwise the guide tube will be washed askew and the fabric will be directly exposed to the high-temperature airflow. There is also the installation direction: non-metallic compensators usually can't withstand pressure thrust, so the tie rod bolt should be adjusted to the appropriate tension (refer to the FAQ "How to adjust the tie rod nut of the expansion joint"), and it can't be screwed to death or too loose.

In addition, where to choose the location is also very particular. Try to avoid installing it behind the elbow or in the turbulent zone downstream of the valve, otherwise the airflow impact will shorten the fabric life. If you can't avoid it, then install an internal anti-scour board (some manufacturers design it as standard, and some have to be customized). You bought the compensator with or without a deflector? This is inSpecific Function of Expansion Joint Guide TubeThere is a detailed explanation in the Q&A, so it is recommended to take a closer look before placing an order.

5. How many years can the life span last? Practical recommendations for maintenance and replacement

The lifetime of non-metallic compensators is greatly affected by temperature fluctuations. If the medium temperature is stable, the aging of the fabric layer is slow, and it is normal to use it for 6 years. However, if it starts and stops frequently and the temperature rises and falls sharply, it may have to be changed in 3 years. Simple maintenance: check the fabric surface every six months for any cracks, aging and brittleness, and any leakage traces. By the way, use a flashlight to see if the internal guide tube is deformed or fallen off.

Once you find bulging or partial ablation of the fabric, don't hesitate to change it quickly. Note when changing: Before dismantling the old ring belt, first confirm that the pipeline has cooled down and relieved pressure, safety first. When installing the new ring belt, the strip bolts should be symmetrically tightened to prevent uneven force. If you can't handle it yourself, go directly to the manufacturer for after-sales service. Many non-metallic compensator suppliers provide on-site replacement services.

After all, what is the performance of high-temperature resistant non-metallic compensators? Depends if you know how to use it. Temperature resistance of materials is a hard index, while installation and maintenance is a soft effort. Get these points thoroughly, and it is definitely the "utility pie" in your plumbing system.