Specialized in manufacturing compensators, expansion joints, baffle doors

Find out what the silicone cloth is for in a non-metallic compensator-not a simple layer of cloth

When many people hear "non-metallic compensator silicone cloth", their first reaction is: Oh, it's a layer of cloth, which is padded in the middle of the flange to prevent leakage. Tsk, thinking so, the first step is missing.

The role of silicone cloth in non-metallic expansion joints (also called fabric fiber expansion joints) goes far beyond sealing. It has to carry three things at the same time: temperature, pressure and displacement compensation. For example, in the high-temperature flue gas pipeline, the temperature always goes up to 300℃, and ordinary rubber has long been baked. The silicone cloth has been treated with special coating, and the temperature resistance range is usually-60℃ to +300℃. Some models with glass fiber or ceramic fiber layer can withstand more than 600℃ for a short time.

More importantly, the silicone cloth is the core of the flexible compensation layer – it is responsible for absorbing the axial expansion and contraction, lateral offset, and angular displacement of the pipe. If you think of it as a simple gasket, it is equivalent to turning the whole compensator into an iron plate, and all the elasticity that it should have is gone. Two days ago, I met a customer, who said that it had leaked after installing it for only three months. When I took it apart, I saw that the silicone cloth was pressed into a dead fold by the screw, which didn't compensate at all. It's not that the product is not working, it's the wrong usage.

Rollover site before installation: the flange surface is not treated, the size is not checked, and the screw direction is reversed

Before installing non-metallic compensator silicone cloth, three low-level errors can scrap a good set of products.

The first, the flange face is not treated.The flange removed from the old pipe, which is all welding slag, rust and greasy, is directly installed with silicone cloth? That is equivalent to laying carpet on sandpaper-no matter how tight the press is pressed, the leakage point will appear instantly as soon as the medium flushes. Standard practice: Clean it with a wire brush or angle grinder to ensure that the flange surface is flat and smooth without bumps. If there is a pit exceeding 1mm, it must be repair welded and polished.

Second, the size is not reviewed.Don't say "about the same". When installing non-metallic expansion joints, the diameter of flange bolt holes, hole spacing and outer diameter of flange must be measured against the drawings. 5mm more, the bolt can't pass through; It is 3mm less, and the press strip can't cover it. In a case of a power plant, the workers put the silicone cloth on without measuring the hole distance. As a result, the bolts were twisted diagonally, and the silicone cloth was torn directly at the bolt hole, and it was scrapped before it was put into production.

Third, the direction of the screw is reversed.This one is the most hidden. Many non-metallic compensators are equipped with pressing bars and fastening screws on both sides of the flange. The threaded end of the screw should face the outside of the pressing bars to facilitate screwing the nut. However, someone tried to save trouble and threw the screw in from the inside. As a result, the nut was blocked by the flange when it was twisted halfway, and it couldn't be pressed tightly at all. In the end, it could only be disassembled and reinstalled, and the construction period was delayed for two days.

Core four steps: line drawing and positioning → strip pressing → bolt pre-tightening → symmetrical tightening, one step wrong reduces the life by half

So how on earth do you pretend? Don't mess around, go in this order, and rework if the order is wrong.

Draw line positioning.First, lay the silicone cloth flat on the flange surface, and draw a circle along the inner diameter and outer diameter of the flange with a marker to ensure that the silicone cloth is centered and not skewed. Especially for rectangular non-metallic expansion joints, the four sides must be symmetrical. If the offset is 5mm, the compensation amount will be offset by 10%. When drawing the line, pay attention to the fiber direction of the silicone cloth-the warp direction (length direction) corresponds to the axial displacement of the pipeline, and the weft direction corresponds to the lateral displacement. If this direction is reversed, the compensator is equal to uninstalled.

Strip compacting.The strip (usually angle or flat steel) should fit the flange and completely enclose the edge of the silicone cloth. The bead joints are staggered as much as possible to avoid weak spots in the same position. The bolt holes on the press strip must be aligned with the flange holes, and cannot be pulled hard.

Bolt pre-tightening.Many people are fast in this step, so they can directly use the electric wrench to fight it to the end. SO WRONG! Pre-tightening means to first screw all the bolts with a wrench until they just touch and eliminate the gap, probably until they can't be screwed by hand. Don't rush on the torque, there is also symmetrical fastening in the back.

Symmetrical fastening.That's the key. Tighten three times from center outward, diagonally crossed. The first screw to 50% of the design torque, the second to 80%, and the third to 100%. For example, M16 bolts, the recommended torque is 80~100N·m. Do you have to use a torque wrench and screw it by feel? The error can exceed 30%. In this way, the silicone cloth is uniformly stressed, the sealing surface is flat, and the service life is at least doubled.

Should the pre-stretching of silicone cloth be done or not? Don't be led off by the experience of the old master

"You should tighten the silicone cloth first, otherwise it will be loose and baggy when used." Is this correct? According to the situation.

Silicone cloth itself is a flexible material. If it is intentionally stretched during installation, the advantage is that it can apply tension in advance when the pipeline is cold, and it is not easy to wrinkle after thermal expansion. But the disadvantages are more obvious: excessive stretching, early fatigue of internal fibers of silicone cloth, accelerated aging and fracture at high temperature. Especially when the non-metallic compensator is used in high-temperature flue gas or steam pipeline, the amount of thermal expansion is inherently large, and the pre-stretching makes the silicone gel cloth bear additional stress in the hot state.

I checked the installation manuals of several mainstream manufacturers (including the information of rectangular non-metallic expansion joints on this site), and generally recommended:Not pre-stretched。 When the silicone cloth is installed, it can be kept in a natural flat state, and a small margin (1% ~2%) is allowed to cope with fine adjustment. Only when the displacement of the pipe is extremely large and the elasticity of the silicone cloth itself is insufficient, it is necessary to pre-stretch at the stretch ratio given by the manufacturer (usually not more than 5%). Master's experience may apply to old-fashioned asbestos gaskets, and silicone cloth is different. Don't blindly follow the trend.

Three pits that frequently occur in use: media scouring, temperature exceeding limit, and loose beading

Once installed and set and forget? Thinking too much. Three common problems in the running phase, pay attention in advance.

Media flushing.If there is high-speed dusty flue gas in the pipeline (such as desulfurization flue of thermal power plant), and the particulate matter washes the surface of silicone cloth for a long time, the coating will gradually wear out, expose the fiber layer, and then leak. Solution: Add a guide tube or wear-resistant liner inside the non-metal expansion joint (such as the wear-resistant liner matched by the desulfurization flue gas baffle door of this station). If not, then you have to check the windward side of the silicone cloth regularly, and if you find wear, patch the sheet immediately.

Temperature exceeded limit.The temperature resistance of silicone cloth has an upper limit. Some process pipelines occasionally overheat by dozens of degrees during operation, such as 300℃ in design, but 350℃ in actual fact. It may be okay once or twice, but repeated overheat will cause the silicone cloth to become brittle, hard and cracked. Don't expect it to bear the design limit. Over-temperature 10% may reduce its life by 50%. It is recommended to install temperature monitoring points or choose higher grade composite fabrics (such as ceramic fiber cloth + silicone coating).

The bead is loose.The bolts will slowly loosen under high temperature and vibration, especially when non-metallic compensators are used for fan inlet and outlet pipes. Check once a week and tighten the nut with a wrench. Some customers ignore it after installation. After half a year, the strips fell off, and the silicone cloth was blown by the airflow and torn instantly. This is called a small loss.

When is it time to change silicone cloth? Just look at these three points, don't wait for a leak before dismantling

Silicone cloth is not a permanent piece, so you should change it. Don't be reluctant. Three judgment criteria:

• Cracked or hardened surfaces.Press by hand, if the silicone cloth loses its elasticity, cracks will appear when it is gently broken, indicating that the coating has aged and failed. If you don't change it at this time, the next step will be penetrating leakage.
• Local bulging or delamination.The silicone cloth and the reinforcement layer disengaged and bulged like blisters. The reason is the infiltration of the medium or the action of thermal stress, and the bulge will rupture if it is continuously used.
• There are leakage marks at the flange bead.Even if it's just a wet mark, don't wait for a drip. Disassemble and check. If the edge of the silicone cloth has been corroded by the medium and become brittle, it must be replaced.

There is no fixed standard for the replacement cycle, but according to the industry experience of this station, under normal working conditions (temperature ≤250℃, no strong corrosive medium), silica gel cloth can be used for 2~3 years without problem. If the working conditions are bad, such as high sulfur content in flue gas or large pipeline vibration, it is recommended to stop the machine for inspection once a year. Don't wait until it leaks before removing it-at that time, even the flange may be corroded by the medium, and instead of a piece of cloth, the whole expansion joint will be replaced.

How to use non-metallic compensator silicone cloth? Treat it as a precision part of the system, not as a consumable. It takes an extra half hour to install and saves half a year to run.

First, understand the structure of the non-metal compensator before painting-it is not metal, so don't copy the ripple painting method

To be honest, I've seen too many people paint non-metallic compensators the same way they paint metal bellows. And the result? The drawing resembles a stiff pile of iron, completely ignoring the flexible nature of the fabric skin. The core structure of non-metallic compensator (that is, we often call fabric fiber expansion joint) is three layers: the outer layer is temperature-resistant fiber fabric (such as silicone cloth and fluororubber cloth), the middle is heat insulation layer (ceramic fiber blanket or rock wool), and the inner layer has an anti-corrosion lining. The frame is metal — usually a rectangular or circular flanged frame welded from Q235 or 304 angle steel, channel steel. The skin is fastened to the frame by beading and bolting, creating a soft connection segment that can be twisted. To put it bluntly, this thing is a "rigid and soft mix" structure: the rigid one is the upper and lower flanges, and the soft one is the middle section of fabric. When you paint CAD, you would be wrong to still paint the skin corrugated-the non-metallic compensator has no corrugations, it relies on the elastic deformation of the fabric itself to absorb displacement.

2. Confirmation of key parameters: pipe size, compensation amount, skin material and flange connection form

Before you start drawing, set these numbers to death. Otherwise, if you find out that the flange bolt hole is wrong in the middle of the drawing, it will be called a collapse.
Take-over size: OD or ID of pipe? Is it a circular duct or a rectangular air duct? For example, the power station industry commonly uses round shapes, while the cement industry has more rectangular shapes. Our site hasRectangular non-metallic expansion jointAndNon-metallic expansion joint (fabric fiber expansion joint)The two products have different dimensioning habits: circles are directly marked with DN, and rectangles are marked with length × width.
Compensation amount: What are the axial, transverse and angular displacements? The compensation capacity of non-metallic compensators is much greater than that of metals, and the axial energy can reach ±50mm or even greater, but you can't blindly paint too thick. There is a standard for the number of skin layers. Referring to the JB/T 12235-2015 standard mentioned in the FAQ of this site, the number of skin layers is generally 3~5, and the thickness of each layer is 0.5~1.5mm.
Skin material: Silica gel cloth + glass fiber for high temperature working condition, polytetrafluoroethylene coating cloth for corrosion working condition. Don't confuse material labeling-for example, this site hasRubber PTFE compensator, that is, rubber and PTFE compound, can't be written as pure fluorine tape.
Flange connection form: Angle steel flange or flat flange? Is the number of bolt holes a multiple of 4 or is it divided equally according to the air duct size? These data must be extracted from the form factor chart provided by the customer, or from the ready-made data on this siteModel and size of expansion jointLook for references in Q&A.

3. Drawing of two-dimensional engineering drawings: from the main view to the cross-sectional view, emphasizing the overlap between the frame and the skin

Two-dimensional drawings are the basis of production drawings. Open CAD, and set the layers: the structure line, the marking line and the section line are separated. Draw the main view first-usually the outer contour of the flange, draw a rectangle for a rectangle, and a circle for a circle. Then the cross-sectional view is the point: you have to cut at least A-A to express the skin lap structure clearly.
How to paint skin? Don't draw it as a continuous arc! The skin of the non-metallic compensator is not corrugated, it is composed of layers of fabric superimposed and pressed against the flange surface by beading and bolting. Therefore, in the cross-sectional view, the skin part should be drawn as several parallel lines (representing different layers of fabric), and both ends should be represented by a schematic diagram of pressing. The press bar is generally flat steel, with a thickness of 4~6mm and a width of 25~40mm. The bolt spacing is usually 150~200mm. This parameter should be confirmed with the customer, and then marked next to the cross-sectional view.
Also, don't forget to markguide tube。 If you are drawing a non-metallic compensator with a deflector (such as one used in a flue gas desulfurization system), the deflector direction must be clearly marked-the arrow points to the direction of the medium flow. There are special topics in the FAQ of this siteSpecific Function of Expansion Joint Guide TubeIf the guide tube is not installed in the right direction, the consequence will be to wear the fabric skin, and the life span will be directly cut in half.

4. Thoughts of 3D modeling: Using lofting and curved surface tools to simulate the twist and wrinkle of fabric skin

Three-dimensional drawings are mainly used to inspect assembly interference or show them to customers. But how to draw the folds of non-metal skin? Stumped a bunch of people.
What I do is: first build two upper and lower flange boxes (stretch solid), then between the two boxes withloftingCommand to generate a connector. However, don't loft directly into a straight contour-the skin will have natural wrinkles under pressure, so add several control points to the loft path to make the surface slightly bumpy. For example, in a rectangular compensator, the central area of the side of the skin can be retracted by 5~10mm to simulate the effect of depression under negative pressure. Of course, this is just a sign, and the real fold shape is ever-changing, but CAD modeling doesn't have to be completely real, so long as customers can understand "this is the flexible section".
For circular fabric compensators, you can useRotating surfaceOrsweepCommand, but pay attention to the thickness of the skin (0.5mm fabric layer can be ignored directly in three dimensions, too thin to show). The key point is to draw the metal parts such as flanges, bolts and strips clearly, and the skin is represented by translucent materials or maps, so that you can see which parts are soft at a glance.

V. Distinguishing Occasions: Drawing Differences between Rectangular Nonmetallic Expansion Joints and Circular Fabric Compensators

Rectangular non-metallic expansion joint (refer to this siteRectangular non-metallic expansion jointProducts) are usually used in flue gas pipes, which are large in size and can reach 5 meters in side length. At this time, the graphic should focus on the arrangement of reinforcing ribs of the frame-the angle steel frame needs to add vertical ribs in the middle of the long side to prevent the skin from bulging. In the cross-sectional view, draw the cross-section of the stiffener.
Circular fabric compensators (that is, we often call non-metallic expansion joints) are mostly used in small-diameter pipes. The flange is a circular ring and the skin is a cylindrical surface. The marking method is closer to the metal compensator, but it should be noted that round products usually need to be marked with "installation length L", which includes flange thickness + skin free length + strip height, while metal compensators generally only mark the length of corrugated section, which is different.
In addition, guide tubes are rarely used for round products (the flow rate of small-diameter pipes is fast, but the guide tubes increase the resistance), but rectangular products must be added with guide tubes in the desulfurization system to prevent dust accumulation. You have to distinguish between scenes when drawing.

6. Common marking traps-don't miss the direction of the guide tube, the thickness of the heat insulation layer and the hole distance of the mounting bolts

Finally checking, these are the most error-prone places:
Direction of guide tube: As mentioned earlier, the arrow points to the flow direction of the medium, and the front end of the guide tube should extend into the inside of the pipe, leaving a gap of 10~20mm between the rear end and the inner wall of the skin. This gap is not marked, and it is easy for workers to push the skin when they install it.
Insulation thickness: The insulation layer of non-metallic compensator is generally only written "xx mm" on the design drawing, but in actual production, customers may require two layers of ceramic fiber + one layer of air. You have to write clearly in the technical description of the drawing: total thickness, material and density of the insulation layer (e.g. 128kg/m³). Otherwise, if you buy the wrong purchase, the insulation effect will be discounted.
Installation Bolt Hole Spacing: The bolt holes in the flange must be marked with center distance and distribution. Circular flanges are generally marked with PCD (pitch circle diameter) and number, while rectangular flanges are marked with adjacent hole spacing and corner hole positions. Many novices only mark the outer contour size of the flange and forget to mark the hole distance. Consequences? It can't be installed on site, and rework takes time and loses money.
In addition,Length of overlap between skin and flangeIt should also be marked-usually 20~30mm, and the width of the strip covers the overlap area. This number is clearly marked on the partial enlargement of the drawing. Don't expect workers to guess for themselves. If they guess wrong, it is a quality accident.

Alas, in the final analysis, drawing a CAD drawing of a non-metallic compensator is completely two sets of ideas than drawing a metal. The metal compensator is deformed by corrugation, and the non-metal is stretched by fabric. You have to have that "soft box" concept in your head before you write. If you just want to draw a picture of a non-metallic expansion joint at hand, you might as well compare the above points and dismantle the structure before starting. The drawn picture in this way can be directly cut by the workshop master after reading it, which is more worry-free.

Once the nonmetallic compensator (that is, we often call the fabric fiber expansion joint) bulges, collapses or twists, many people's first reaction is to remove it and replace it with a new one. Wait a minute – deformed ≠ scrapped. Find out what kind of deformation it is first, and then decide whether to repair or replace it, which can save thousands of shutdown losses and spare parts costs. Today, let's get this out of the way.

Look at the form first, then look for the cause

Bulging, collapse, twisting, localized wear. The bulge is mostly caused by gas expansion inside the fabric fiber layer or damage to the inner lining; Collapse is mostly caused by negative pressure suction or condensate corrosion, which causes the fiber to lose elasticity; The twist is probably due to the misalignment of the pipeline during installation and the shear force of the compensator; Localized wear is common in particle-containing scouring of media. And guess what? Deformations that occur in the same location may have completely different causes. For example, the non-metallic compensator behind the desulfurization flue gas baffle door has been exposed to acidic condensate for a long time, and the fiber layer begins to eat away from the inside. The outside appears to be only slightly collapsed, but when it is disassembled, it is already layered inside. You just change your skin at this time? It's useless, we have to do it with the drainage device and the anti-corrosion coating.

Temperature overruns and pressure fluctuations: the number one killer

The design temperature resistance of non-metallic expansion joints is generally engraved on nameplates, but the local heat radiation or flue gas flow rate changes are often neglected in actual working conditions. Two days ago, I met a cement factory customer. The measured temperature in the pipeline was 50℃ higher than the design value, and the skin was directly carbonized and deformed-the surface felt like a charred biscuit. What about that? Check the heat source and insulation first, and don't dismantle the compensator as soon as it comes up. After lowering the local temperature and restoring the heat insulation layer, as long as the fiber is not broken, adjust the limit bolt (refer to the adjustment method of the expansion joint tie rod nut), so that the compensator can restore part of the pre-compression amount, and it can last for a while. The same is true for pressure fluctuations, especially near the position of electric plug-in type isolation door or manual plug-in type isolation door. The impact at the moment of valve opening and closing may make the compensator bulge instantly. Priority is given to checking the system pressure relief and valve action logic rather than hardening the compensator itself.

Installation deviation: a fault that is slowly worn out

When the pipe is matched, if the flanges at both ends are not in a straight line, the non-metallic compensator will be forcibly pulled to bear the shear force. This deformation is not visible to the naked eye in its early stages-it feels normal when you glance at it during your inspection. But after a few months of operation, one side of the compensator will appear with dense folds, like the wrinkles on the face of an old lady. Why? Because of the long-term uneven stress of the fabric fiber layer, local fatigue. The solution is simple: Readjust the pipe support to release the stress. Don't reinforce the frame of the compensator, it will only transfer the stress to a weaker place.

Corrosion and ash accumulation: comprehensive treatment of chronic diseases

Rubber compensator and rubber PTFE compensator are very common in chemical industry and desulfurization scenes. Rubber is corrosion resistant, but rubber PTFE compensator is easy to age and deform at high temperature. The materials of the two are different, and the processing logic is also different. If the rubber compensator bulges, it is likely that the oil or solvent in the medium penetrates into it and swells the rubber. At this time, you measure its hardness. If it becomes obviously soft, you have to change it. If the rubber PTFE compensator ages and hardens, and the surface cracks, it has to be replaced. However, there is an exception: if the non-metallic compensator behind the desulfurization flue gas baffle door collapses and deforms but is not broken, you can first check whether the drainage device is blocked, clean up the dust by the way, and then adjust the limit bolt to observe the operation.

What conditions can be "conservatively treated"?

If it is slightly bulged and not damaged, it can be saved in this way: the first step is to shut down for cooling and pressure relief; In the second step, gently poke the bulge with a screwdriver. If you feel that there is gas released inside (the fiber layer is just bulging, not tearing), you can adjust the tie rod nut to let the compensator restore a little pre-compression; The third step is to reduce the operation parameters of the system, such as lowering the temperature by 10℃ and the pressure by 0.05MPa, and running for 24 hours for observation. The bulge disappeared? Then keep using it, and arrange regular inspections. Remember: Nonmetallic compensators are different from metallic expansion joints in that their flexibility depends on the fiber layer, which must be replaced once the fibers break or delaminate. If you touch the deformed area with your hand, if it feels loose and baggy like linen, it means that the fiber has broken. Don't hesitate, according to JB/T 12235-2015 standard, continuing operation at this time will only accelerate the fatigue failure of the whole pipeline system-whether it is corrugated expansion joint or straight pipe pressure balance expansion joint, adjacent equipment may suffer.

What circumstances must be shut down for replacement?

Leaked, delaminated, metal frames and pipes detached. For example, the non-metallic compensator on the vacuum pipeline of the air-cooled island of a power plant began to leak after deformation, and the inspector didn't take it seriously. As a result, a month later, the adjacent transverse expansion joint of the compound hinge also cracked. Because after the compensator failed, no one absorbed the thermal displacement of the pipe, and all of it was pushed to the nearby equipment. You must pay attention to two points when replacing: First, the selection should match the original design-rectangular non-metal expansion joint or round fabric fiber expansion joint? The dimensions and interface flanges must be consistent; Second, don't use brute force to force the counter when installing, first adjust the pipe support and then install the compensator. And guess what? Many people try to save trouble. As soon as the new compensator is installed, the bolts are tightened, and as a result, the torsional stress is brought back to the compensator, which is wasting money.

What if the non-metallic compensator is deformed? To put it bluntly, there are three steps: first judge the form and cause, and adjust the limit bolts and working conditions if you can save them; If you can't save it, replace it strictly according to the standard, and repair the installation deviation and corrosion source together. Don't be lazy, and don't mess around. If you use the compensator right, it will last five years, but if you use it wrong, it will be wasted for three months.

How do you say non-metallic compensator in English? All three types of translation engineers use

Two days ago, a foreign trade buddy called me, and when he came up, he asked, "Hey, how do you say non-metallic compensator in English? I reported it to foreigners here, and they returned the email saying they didn't understand, which was embarrassing." This problem is actually very common, especially in the B2B circle. The Chinese product name you wrote was translated in the past, and foreigners didn't buy it at all. Today, we're gonna get this out of the way.

1. What is the use of understanding English terms? — — Foreign trade quotation, standard docking and technical documents can't be avoided

To be honest, there are only a few English words for non-metallic compensators, but if you use them incorrectly, big things will really happen.
Let's talk about foreign trade quotation first: the product name you quoted to the customer is "Non-metallic Compensator". the customer may think that you are talking about metal bellows, or directly ask "What's the material?". Because foreigners are used to calling them according to materials and structures, unlike us collectively referred to as "compensators".
Let's talk about standard docking: the official English name of non-metallic expansion joint is stipulated in the domestic JB/T 12235-2015 standard, but there is no such word in foreign standards such as EJMA and ASME. If you want to check the drawings with the European engineers, you have to use the terms they recognize, otherwise the other party will directly refund the order.
The technical document is the hardest hit area: "Fabric Expansion Joint" is written as "Non-metallic Bellows" in an installation manual, and foreigners have to think about it for a long time-does it mean cloth bags or the kind with metal mesh?
So, don't just look at one word. Behind it is the quotation success rate, technical communication efficiency, and the compliance of the whole project. If you get it right, you will save yourself a big deal.

2. The national standard has the final say: What is the official English name in JB/T 12235-2015?

Let's look at our own standards first. JB/T 12235-2015 "Non-Metallic Expansion Joint" clearly written: English name isNon-metallic expansion joint。 Note that "expansion joint" is used here instead of "compensator".
This standard tube is fabric fiber expansion joint (that is, the classification of "non-metallic expansion joint (fabric fiber expansion joint)" in our website). In structure, it is mainly rubber/fiber cloth + silicone cloth + thermal insulation cotton, which absorbs heat displacement by flexible materials.
So if the customer asks "Is there a national standard product?", you just throw this sentence : Non-metallic expansion joint per JB/T 12235-2015. Professional, nothing wrong with it.
But don't worry and be happy, the national standard is only for domestic use. If you send an inquiry to the United States, the other party will probably return to you "What's a non-metallic expansion joint? You mean fabric expansion joint?"

3. Expansion joint or Compensator? Can these two be mixed in English circles?

Don't mix. But you may not believe the reason.
In our Chinese context, "expansion joint" and "compensator" are exactly the same, as you can see in Article 14 of Q&A on this site. But in English, Expansion jointIs a common term in the industry, covering metals and non-metals; WhileCompensatorMore refers to "compensating devices", such as "pipe compensators" have a wider range, including Rotary compensators, sleeve compensators, and so on.
How do foreigners use it?
-People who engage in power generation, petrochemicals and HVAC, it is customary to say Expansion joint, especially equipment manufacturers.
-Boiler, flue, maybe Expansion joint for flue gas duct。
-For chemical pipelines, occasionally Compensator, but more common in European standards (such as DIN).
And guess what? I turned through hundreds of foreign inquiries. When 90% of foreigners look for non-metallic products, the key word is "Fabric expansion joint". So for the sake of insurance, write when quoting Non-metallic expansion joint/Fabric expansion jointDouble labeling is the most robust.

4. Don't just focus on one word: What products do Fabric, Non-metallic and Bellows correspond to?

There's a pit here that newbies are easiest to fall into.
Fabric expansion joint— — Fabric expansion joint, specifically refers to the compensator with fiber cloth/glass fiber/silicone cloth as the main body and without metal bellows. Typical products: "Non-metallic Expansion Joints (Fabric Fiber Expansion Joints)" and "Rectangular Non-metallic Expansion Joints" on our website. Flue gas, dust and low pressure scenarios are preferred.
Non-metallic expansion joint— — Non-metallic expansion joint, the range is slightly larger than that of fabric, and also includes rubber compensator and PTFE compensator. Like the "Rubber Compensator", "Rubber PTFE Compensator" and "PTFE Compensator" of this site are all of this kind.
Bellows— — Bellows, this basically refers to the expansion joint of metal bellows. However, some foreigners also call non-metallic ring structures "bellows", such as rubber bellows. However, most of the time, when you use bellows to report non-metallic products, the other party will mistakenly think that you want metal.
So to summarize:
-Fabric fiber type → Fabric expansion joint
-Rubber/PTFE type → Non-metallic expansion joint or Rubber expansion joint
Polytetrafluoroethylene type → PTFE expansion joint
-Don't use Bellows unless you are quoting metal Bellows (e.g. "Universal Corrugated Expansion Joints", "Corrugated Expansion Joints for Power Station Industry").

5. Practical suggestions: choose English names according to working conditions, and take stock of similar products of non-metallic compensators in this site

One thousand words, one thousand, one thousand, one thousand, one thousand, one thousand Let me give you a simple principle:
Look at the working conditions and set the keywords.
-Working conditions: flue gas, high temperature, rectangular pipe → in English Fabric expansion joint→ Corresponds to "rectangular non-metallic expansion joint" and "non-metallic expansion joint (fabric fiber expansion joint)" of this site.
-Working conditions: water, weak acid and alkali, flexible connection of pipeline → in English Rubber expansion jointOrNon-metallic expansion joint→ Corresponds to "rubber compensator" and "rubber PTFE compensator".
-Working conditions: strong corrosion, high temperature (PTFE) → English PTFE expansion jointOrTeflon expansion joint→ Corresponds to "PTFE Compensator".
As for other products, such as "metal hose", "PTFE-lined metal hose" and "flue gas baffle door", they are all metal systems or valve systems, so don't mix them into non-metal systems.
Finally, when you write an e-mail inquiry, include the title Non-metallic Fabric Expansion JointWrite the national standard number, size, medium, temperature and pressure clearly in the text. Foreigners can understand at a glance, and the quotation speed can be 50% faster.
Well, about "How do you say non-metallic compensator in English?" This matter, you shouldn't have to worry about it anymore, right? Next time you meet a customer and ask, just throw these words away, steady.

Find out what a "large-size" nonmetallic compensator is first

Many people ask "What are the large-size non-metallic compensators?" as soon as they come up, but they have to figure out the concept first. Large size, in the industry usually refers to pipe or air duct connections with a diameter or side length of more than 1 meter, or even to 5 meters or 10 meters. It is completely different from metal compensators-metal compensators absorb displacement by bellows, non-metal compensators use flexible bands, and the main body is made of fabric, rubber or PTFE composite. To put it bluntly, non-metallic is a layer of "soft connection", which can cope with multi-directional displacement at the same time, and is corrosion-resistant, high-temperature-resistant and light in weight.

And guess what? In places such as desulfurization flue of power plant and cement kiln tail, metal compensators can't bear corrosion and dust accumulation at all, while non-metallic compensators have become just needed. Therefore, don't stare at the selection of metal parts as soon as you come up, but first see if the working conditions are right.

By shape: What are the doorways of rectangle and circle?

Rectangular non-metallic expansion joint

Rectangular structure is mainly used in square flue and air duct. For example, the hot and cold air ducts of power station boilers and the inlet and outlet of desulfurization towers. OurRectangular non-metallic expansion jointThe frame is usually welded with angle steel or channel steel, and the loop belt is compounded with multi-layer fabric + insulating cotton + sealing film. This shape has the advantage of absorbing large lateral displacements and facilitating on-site installation. The disadvantage is that the pressure bearing capacity is weak, and it is generally only used in low pressure (≤0.1MPa) occasions. Two days ago, I met a cement factory customer. The size of the kiln tail flue was 3m ×4m, and the temperature was 350℃. Finally, I chose a rectangular non-metallic expansion joint, which took three years without any problems.

Circular non-metallic expansion joint

The circular structure is suitable for pipeline butting, with diameters ranging from several hundred millimeters to several meters. Unlike the metal bellows, the circular non-metallic compensator has no corrugated body, but is deformed by the wrinkles of the loop belt. It has the advantage of large axial compensation and is suitable for long straight pipes. Note that circular shapes also have to be connected with flanges or sleeves, so don't confuse them with metal hoses.

According to the material: fabric fiber, rubber, PTFE composite-how to choose different working conditions

• Fabric Fiber Expansion Joints (Non-Metallic Expansion Joints): The main material is glass fiber cloth, polyester fiber cloth, and then superimposed silicone rubber or fluororubber coating. The temperature resistance range is-40℃ to 450℃, and it can reach 600℃ in a short time. It is suitable for the high temperature and weak corrosion environment of power plant air duct and boiler flue. OurNon-metallic expansion joint (fabric fiber expansion joint)This is the type, the loop belt can be customized in layers and thickness.
• rubber compensator: The main body is synthetic rubber (e.g. butyl, chloroprene, EPDM). The temperature resistance is generally lower than 120℃, but it has excellent elasticity and can absorb vibration and noise. It is more used in pump inlet and outlet and air conditioning pipes. Note that rubber is afraid of oil and ozone, and lightning should be protected under working conditions.
• Rubber PTFE compensator: The rubber is lined with a layer of PTFE, which combines the elasticity of rubber with the corrosion resistance of PTFE. The upper temperature resistance limit is about 200℃, especially suitable for pipelines with strong acid and strong alkali media. This product is common in the chemical and pharmaceutical industries, such as ourRubber PTFE compensatorAndPTFE compensatorThe former is soft and the latter is rigid.

Select fabric fiber for high temperature and dust, select rubber for low temperature vibration, and select PTFE compound for strong corrosion. Don't be greedy and choose randomly, otherwise it will leak in three months.

Special scenario: desulfurization flue gas, cement kiln, power station air duct-what are the non-metallic compensators in these industries

Every industry has its own weird temper. Take desulfurization flue gas as an example. The temperature is not high (50-80℃), but the humidity is high and the acid-containing dew point corrosion is serious. At this time, anti-corrosion film (such as FEP or PFA) must be added to the fabric fiber band, otherwise it will rot for half a year. OurDesulfurization flue gas baffle doorIt is often used in conjunction with non-metallic compensators to form a sealed system.

In the flue of cement kiln, the temperature fluctuates greatly, from 200 ℃ to 500 ℃ instantaneously. The non-metallic compensator must choose high-temperature resistant ceramic fiber cloth, and increase the thickness of heat insulation layer. I have seen some manufacturers use ordinary glass fiber, and as a result, it hardens and cracks in a month.

The air duct of the power station is oversized (5 meters ×5 meters at every turn), and it needs to absorb axial, lateral and angular displacements. At this time, rectangular non-metallic expansion joint is the first choice, and the ring belt should be pre-compressed and installed, otherwise it is easy to tear during thermal expansion. Our product information also includesCorrugated expansion joint for power station industryBut that is for metals, and the selection logic of non-metals is completely different.

Selection and pit avoidance guide: size, compensation amount, temperature, pressure, one parameter is wrong, it is useless

• Dimensions: Measure the spacing between the outer wall of the pipe, do not press the inner diameter. To calculate the peripheral length of the rectangular piece, the width of the ring belt must be greater than the design displacement, otherwise it will be broken.
• Compensation amount: Axial, lateral and angular displacements should be listed separately. The compensation ability of non-metals is greater than that of metals, but it depends on the number of belt layers. In general, a single layer of fabric can compensate for ± 50 mm, and a multi-layer can compensate for ± 150 mm. Don't just look at the maximum value of the sample, but actually leave a margin.
• Temperature: Continuous operating temperature and instantaneous peak temperature are two concepts. When selecting the material of the ring belt, the peak value must not exceed the material limit. For example, silicone rubber coating is ≤250℃, and fluororubber is ≤280℃. If it exceeds, polytetrafluoroethylene or all fabric must be used.
• pressure: The withstand voltage of non-metallic compensators usually does not exceed 0.1MPa (about 1kg), but some reinforced types can reach 0.25MPa. Above this value, don't consider non-metals, and honestly go to metal expansion joints.

A steel mill chose a rubber compensator for use on a 300℃ flue gas pipeline, but it burst in two weeks-because rubber couldn't withstand the high temperature at all. Therefore, the parameters are not accurate, and no matter how cheap it is, it is a waste.

Installation and maintenance: Why are non-metallic compensators more delicate than metallic ones?

Non-metallic compensators are delicate because the bands are flexible and susceptible to mechanical damage. There are a few points to note when installing:

• The loop belt cannot touch sharp objects and is best protected when transported.
• Check that the loop strap is in good condition for scratches or air bubbles before installation. Don't wait until the bolts are finished to find an air leak.
• The flange connection should be symmetrically screwed, and the torque should not be too large, otherwise the ring belt will be crushed. Generally, it is sufficient to screw M16 bolts to 50N·m.
• After installation, adjust the tie rod or limit bolt to ensure that the initial pre-compression amount meets the design requirements. You can refer to our question and answer "How to adjust the expansion joint tie rod nut", which has the same principle.

In terms of maintenance, regularly check the surface of the ring belt for aging cracks, and measure the wall thickness every six months. Don't wait for a leak before replacing it. At that time, the flue is full of smoke, and it is difficult to repair it. Many factories will prepare a set of ring belts as wear parts and replace them at any time. Compared with the metal compensator, which needs to be replaced as a whole, the non-metal ring belt can be replaced separately, which is a money-saving advantage.

So, don't think it's delicate, use it in the right place, and it can save you a lot of downtime costs. The key is to select the type accurately and install it fine.