Two days ago, a customer who was doing a desulfurization project sent a drawing, which was clearly marked "Non-metallic Compensator Type A". He asked me: Lao Zhang, is this the same thing as the non-metallic expansion joint (fabric fiber expansion joint) in your shop? I said, don't be confused, this is the same thing, but the code name on the drawing is different. Type A non-metallic compensator, to put it bluntly, is the most basic round fabric fiber expansion joint.

Let's talk about the conclusion first: Type A is not mysterious, it is a round fabric fiber expansion joint

Talking about non-metallic compensators in the industry, there are two main categories: fabric fiber expansion joints and rubber compensators. Type A specifically refers to a circular structure with single or multi-layer fabric bands, flanged connections, and no guide tubes. Without those bells and whistles configurations, the structure is the simplest and the price is the most affordable. If you take over a flue gas pipeline project, you only write "Non-metallic Compensator Type A" on the drawing, without additional parameters such as pressure, temperature and guide tube. You can't go wrong with the standard parameters of "Non-metallic Expansion Joint (Fabric Fiber Expansion Joint)" of this site to quote.

Look at the structure: the three core components, the circle belt is the soul

The A-type body consists of three things: a loop (that is, a layer of fabric fibers), a metal flange, and a compression bolt. The loop belt is made of silicone or fluororubber coated cloth, glass fiber cloth and ceramic fiber cloth, and has a temperature resistance range of-40℃ to 400℃. It does not absorb the displacement by the deformation of the metal corrugation like the metal corrugated expansion joint, but by the flexible bending of the ring belt itself. This brings a huge benefit – the thrust on the pipe is so small that it is almost negligible. Is it much gentler than the universal corrugated expansion joint of metal?

The number of layers and thickness of the loop belt determine its temperature and pressure resistance. Under normal standard working conditions, three to four layers of composite are sufficient. In case of highly corrosive fumes, a fluororubber coated cloth must be arranged. The price will be a little more expensive, but the lifespan can double.

So what is the difference between it and Type B and Type C?

Type A is the basic model, Type B is the strengthened model, and Type C is the anti-pressure model.

• Type A: The most basic single-loop belt structure, suitable for low pressure (≤0.1MPa) and small displacement scenarios. Air duct, flue duct and dust collection duct are its home field.
• Type B: Install heat insulation layer or guide tube on the A-type basis. The function of the guide tube is to guide the high-temperature flue gas to directly scour the ring belt, so as to avoid the flame directly contacting the fabric layer. Type B is more reliable in high-temperature occasions such as cement kiln tail waste gas pipeline and boiler outlet.
• Type C: Add a stainless steel wire mesh reinforcement layer outside the A-ring belt to resist positive pressure conditions. For example, the pressure of the flue behind the flue baffle door may reach 0.15MPa, and Type C can hold it.

But don't get confused. The "non-metallic expansion joint (fabric fiber expansion joint)" of this site is the standard form of Type A. The "rectangular non-metallic expansion joint" is another category according to its shape, and its structure is completely different. Don't confuse it.

The most painful pain point in model selection: pressure resistance

The biggest weakness of Type A is that it can't bear high pressure. Think about it, no matter how thick the loop belt is, it is still fabric. The metal bellows can withstand the pressure of several MPa. Type A begins to tremble when it exceeds 0.2MPa. Therefore, it is only mixed in low-pressure systems: fan inlet and outlet, dust removal pipeline, desulfurization flue gas pipeline... These places have high temperature and great corrosion, and the metal corrugated expansion joint is prone to fatigue failure. I have done a project in a cement plant. The exhaust gas pipeline at the end of the kiln originally used metal corrugated expansion joints in the cement industry, but it cracked in less than half a year. It was replaced with a type A non-metallic compensator, and there has been no air leak in three years. Why? Because the fabric band is not afraid of repeated bending due to thermal expansion and contraction, the long-term high-frequency vibration of metal bellows is easy to produce stress concentration. Alas, this matter is to put it bluntly: choose the right place, and Type A is a treasure; Throw it on a high-pressure pipeline, and it is scrap metal.

Type A has minimal and almost negligible thrust on the pipeline. This means that you don't need heavy-duty brackets and guide brackets like metal expansion joints, and the steel money saved is enough to buy several compensators. Isn't it a good deal?

Record of Installation Pit Stepping: The 80% Torque Law

Last year, there was a power plant project, and the Type A non-metallic compensator installed by Party A itself tore apart after less than a month's operation. I went over and looked, boy, the bolts were tight and the bands were bulging. What's the problem? In the cold state, the ring belt is too tight, and as soon as the pipeline heats up and expands, the ring belt has no place to release stress and tears directly.

The ring belt is easy to be compressed and deformed during transportation, so the flatness of the flange surface must be checked first after arrival. When installing, pre-tighten the fixing bolts to 80% torque first, and do not screw them to death. After the hot state of the pipeline is stable, do secondary tightening. If you are constructing in winter, the ambient temperature is low and the ring belt is hard, the preloading force can be smaller, 70% is enough. When the summer is hot, the circle belt becomes soft, and then tighten it again. This thing is not about tightening as much as possible, but about leaving a margin for thermal expansion.

In addition, if there is dust or oil on the flange surface of the ring belt, it must be cleaned up. Otherwise, air will leak during operation and the compression bolt will loosen. Don't ask me how I know, it's all experience gained by tuition.

One sentence summary

Type A non-metallic compensator is the most common round fabric fiber expansion joint. Low pressure, low temperature and low thrust are its labels, and flue gas pipes and dust removal air ducts are its destination. If you only write "Non-metallic Compensator Type A" on your drawing, without additional pressure, temperature and guide tube, directly quote according to the standard parameters of "Non-metallic Expansion Joint (Fabric Fiber Expansion Joint)" on this site. Don't worry, you can't go wrong.

Find out what material the compensator ring belt is made of first, and the glue can be selected correctly

Nonmetallic compensators (also called fabric fiber expansion joints) are not a single piece of material. They are usually pressed together by several layers of composite materials-the inner layer is corrosion-resistant fluororubber or silicone cloth, the middle reinforcement layer is glass fiber or aramid fiber, and the outer layer is covered with a weather-resistant rubber coating. How much can the formula of different manufacturers differ? Just ask the supplier: some are mainly silicone rubber, some are fluororubber, and some are polytetrafluoroethylene (PTFE).

The glue doesn't match the substrate, and it is a fool to stick it on. For example, the surface energy of fluororubber is particularly low. Ordinary epoxy glue is coated with water, and it can't stick at all. It has to be coated with a special fluororubber treatment agent and then matched with special glue. So the first step, don't rush to buy rubber, ask your compensator supplier first: What rubber grade is used for the loop belt? They know best.

Common adhesives on the market, advantages and disadvantages are presented to speak human language

• Room temperature vulcanized silicone rubber (RTV silicone): Temperature resistance-60℃ to 250℃, good elasticity, suitable for low pressure, non-corrosive flue gas pipeline. Press the compensator body with your hand, which is soft, and RTV silicone is the most suitable. The disadvantage is that the intensity is not high, and it can't hold up in high-pressure situations.
• Neoprene adhesive (e.g. 801 glue): Initial adhesion is strong, the cost is low, and it will be firm once it sticks. However, the temperature resistance generally does not exceed 100℃, and it is easy to swell and soften when encountering oil. If you use it for temporary repair of room-temperature air ducts, it will work, but it won't work for a long time.
• Epoxy resins: High strength, resistance to chemical media, but hard after curing, no elasticity at all. The compensator itself needs displacement compensation, and the epoxy cracks as soon as it is stretched. If you really want to use it, you must make a flexible transition layer first.

There is also polyurethane glue, which is wear-resistant and oil-resistant, but it is afraid of ultraviolet aging, so it has to be covered outdoors. Before selecting glue, press the compensator body with your finger-silica gel is selected for soft, and epoxy can be considered for hard ones, but it must be fixed mechanically, otherwise it will crack when stretched.

Selecting glue according to working conditions is the core: temperature, medium and pressure must be missed

A few days ago, I dealt with a customer in a cement plant. Their non-metallic compensator was used in the high-temperature flue gas pipeline at the tail of the kiln, and the temperature was around 300℃ for a long time. I first used ordinary silicone gel, and it carbonized and fell off within two days. Later, it was replaced with high-temperature silicone sealant (temperature resistance 350℃), and then it was stabilized with mechanical striping.

If you are a desulfurization flue, the medium contains sulfuric acid and sulfurous acid. At this time, ordinary glue can't hold it at all, so you must use acid-resistant fluororubber special glue or PTFE lining special adhesive. Epoxy resin will slowly corrode away in this environment. Let's talk about pressure: low-pressure pipelines (less than 0.05MPa) can be wrapped with glue; In medium pressure (0.1-0.2MPa), it can't be held by glue alone, so it has to be matched with clamps or pressing strips.

Is that the truth? Glue is not a universal glue. If the working condition is wrong, no matter how expensive the glue is, it will be useless.

Construction details determine the success or failure of bonding. Don't ignore these steps

Surface finishing is a top priority. Wipe the adhesive surface clean with acetone or alcohol to remove release agent, oil and dust-if this step is not done properly, the rest will be for naught. Then sand it a little to add roughness. The surface of fluororubber has to be activated by a special primer, otherwise the glue can't hang.

The thickness of glue layer is controlled at 1-3mm. Too thick, slow to cure and easy to cohesive failure (the glue layer splits itself); Too thin, not enough adhesion, pull off. Don't be lazy about curing time: silica gel generally takes 24 hours to be completely vulcanized, and epoxy takes more than 8 hours, during which it can't be vibrated by force. If you encounter low-temperature weather (below 5℃), the performance of most glues is discounted, so you have to heat or change low-temperature products. If these details are not done, no matter how expensive the glue is, it will be useless.

Common causes of bonding failure and remedies, avoid detours

Interface detachment (the glue separates from the compensator), cohesive failure (the glue layer cracks itself), and the compensator body tears. Interface detachment is mostly due to poor surface treatment or wrong glue type selection; Cohesive failure indicates that the strength of the glue is insufficient or the cure is not thorough; The body is torn, that is, the compensator itself is aging and brittle, and no matter how good the glue is, it can't be saved.

If your compensator has been used for three or five years, and the ring belt has hardened and peeled, don't toss the viscose. It is more cost-effective to directly replace the whole non-metallic expansion joint (fabric fiber expansion joint). This station has ready-made rectangular non-metallic expansion joint and rubber compensator products, which are produced according to the standard JB/T 12235-2015, with supporting installation guidance, which saves worry and effort.

Before selecting glue, ask yourself-what temperature? What is the medium? How stressful? Once these three questions are clarified, the glue will naturally be chosen correctly.

Have you really figured out the role of acid and alkali resistant non-metallic compensators?

As the old saying goes, if you choose the wrong compensator, the pipe will be repaired every day. Especially when encountering acid-base media, a bunch of people come up and ask: Do you use metal or non-metal? Today, let's talk about acid-alkali-resistant non-metallic compensator, and explain its functions, doorways and pits. Don't be too long-winded, you will have a spectrum in your heart after reading it.

Let's start with the name: What is it?

To put it bluntly, compensators and expansion joints are the same thing-they are both devices used to absorb the thermal expansion and contraction, vibrational displacement of pipes. The "acid-alkali-resistant non-metallic compensator" is the kind that specializes in carrying corrosive media, and the material completely draws a clear line with metal hoses and corrugated expansion joints.

This kind of product is usually called in our businessrubber compensator、PTFE compensatorOrNon-metallic expansion joint (fabric fiber expansion joint)。 There are also compound types, such asRubber PTFE compensator, lined with PTFE outer bread rubber. There are many names, but the actual core is one: the main body is not metal, and it relies on polymer materials or fiber fabrics to achieve elastic compensation and corrosion resistance.

Isn't it better for metal compensators to withstand temperature and pressure? Just look down and you will see.

Acid and alkali resistance, why can't metals work, and how can non-metals do it?

No matter how awesome the metal is, it has to kneel when it encounters strong corrosive media such as concentrated sulfuric acid, hydrofluoric acid and wet chlorine. 316L stainless steel won't last a few days in front of hydrochloric acid, let alone ordinary carbon steel. Corrosion not only causes leakage, but also causes hydrogen embrittlement, stress corrosion cracking, especially headache.

Non-metallic materials take a different approach-Polytetrafluoroethylene (PTFE)Known as the king of plastics, except for molten alkali metals and high-temperature fluorine, he is almost not afraid of any acid and alkali;Rubber(Mainly EPDM, butyl and chloroprene) can carry dilute acid and alkali, and the price is cheap and elastic;Fabric fiber(Glass fiber, silicone rubber coated cloth) High temperature resistance, but mainly used to compensate for displacement.

For example, the flue gas in the desulfurization system is not high in temperature but contains a large amount of sulfurous acid and chloride ions.rubber compensatorOrNon-metallic expansion jointIt's much more reliable than metal bellows. And guess what? Some customers saved money on stainless steel, but as a result, it was perforated in half a year, and the renovation cost was twice as expensive as buying non-metal.

What kind of work does it do for you in actual working conditions?

Acid and alkali-resistant non-metallic compensator not only solves corrosion, its daily work includes at least the following three things:

• Displacement compensation:The axial, transverse and angular displacements caused by thermal expansion and contraction of pipelines and deviation of equipment installation are absorbed by corrugations or fabric wrinkles in non-metallic layers. Especially on rectangular pipes (such as flue of power plants and dust removal pipes of steel plants),Rectangular non-metallic expansion jointAlmost standard.
• Vibration isolation and noise reduction:The rubber material itself has damping properties, which can absorb the vibration transmitted by pumps and fans. On the contrary, metal bellows are easy to conduct high-frequency vibration.
• Sealing and pressure bearing:Many conditions require zero leakage. flangedRubber PTFE compensatorOrPTFE compensatorWith the special lining layer, it can withstand the pressure of 0.6~2.5MPa while preventing a drop of acid from seeping out.

Two days ago, I met a buddy who did chlor-alkali engineering. They directly usedPTFE-lined hoseDo pipe connections, but places with many elbows still rely onrubber compensatorSaid it had been used for five years without changing it-tsk tsk, worry-free.

Don't scratch at the selection: rubber, PTFE, fabric fiber, how to pick?

Many purchases ask "Which is best" as soon as they come up? There is no best, only the most suitable. I list a generic selection logic:

• The medium temperature is lower than 100℃, dilute acid and alkali, and the vibration is large:userubber compensator(EPDM or neoprene), which is cheap and has good vibration damping effect. But don't touch strong oxidizing acids (concentrated nitric acid, concentrated sulfuric acid) and organic solvents, the rubber will swell.
• Medium temperature-30~200℃, strong acid and strong alkali, requiring extremely high chemical resistance:UpperPTFE compensatorOrPTFE-lined hose。 PTFE is invincible in corrosion resistance, but has poor elasticity, limited displacement, and cannot be used in vacuum (easily deflated).
• Wide temperature range (-40℃ ~1000℃), large diameter rectangular pipe, containing dust and flue gas:chooseNon-metallic expansion joint (fabric fiber expansion joint)。 The structure is multi-layer fabric + insulation cotton, which can compensate for displacement and insulate heat. For example, high-temperature air ducts in power plant flues and cement industries are used more.
• It should be acid and alkali resistant and have good comprehensive elasticity:ConsiderationRubber PTFE compensator, lined with PTFE contact media, and the outer rubber plays a sealing and compensating role. The price is somewhere between pure rubber and full PTFE.

Isn't it a little messy? Simple note: the pieces with "PTFE" are corrosion resistant, the pieces with "rubber" are elastic and cheap, and the pieces with "fabric" are high-temperature and large-diameter. When selecting, be sure to give the composition, temperature, pressure and displacement of the medium. Don't just throw "acid and alkali resistance" and be done.

Installation and routine maintenance, say a few words if you have stepped on the pit

Say a thousand words and ten thousand, pretending to be wrong is equivalent to buying it for nothing. I've seen too many cases of compensators being scrapped early because of sloppy installation. Here are a few pits you have to bypass:

• The pre-stretch/compression is backwards:Non-metallic compensators usually leave the factory with installation length markings. Pre-stretching is required if the ambient temperature is lower than the design temperature during installation; Otherwise, pre-compression. Many people don't care about the hard installation of 3721, but as a result, it will either crack or explode once it runs.
• Ignore deflector and limit rod:Having a guide tube (e.g.expansion joint guide tube) Must ensure that the media flow direction is consistent with the arrow. Tie rod (expansion joint tie rod) is for transportation protection, and it should be loosened after installation, otherwise the compensator will not move. Otherwise, the stress concentration will tear off the takeover.
• Flange bolts are not screwed by torque:The rigidity of the sealing surface of rubber and PTFE is poor. If the bolts are tightened too tightly, the compensator body will be crushed, and if they are tightened too loosely, they will leak. It is recommended to use a torque wrench and tighten it symmetrically in 3 times according to the value given by the manufacturer.
• Daily inspection does not check displacement indication:Some compensators are marked with displacement scales. Glance at them every quarter. If you find abnormal deformation (such as exceeding the maximum stroke), quickly check whether the pipeline support and hanger have been displaced.

Finally, let's say it-the acid-and alkali-resistant non-metallic compensator, reliable suppliers and installation teams are much more important than the price difference saved. You save 500 yuan in purchase fees and may lose 5,000 yuan in discontinued production losses. Taste yourself.

aboutFunction of acid and alkali resistant non-metallic compensator?The core is four words: erosion and inflation. Choose the right materials, install the right method, and use it for another ten years without panic.

Why use a non-metallic compensator? These five scenes metal really can't do

Dry pipeline compensation has been in the business for a long time, and you will find a heartbreaking fact: metal expansion joints (such as metal corrugated expansion joints and metal hoses) are indeed solid, but when encountering high-temperature flue gas, corrosive media and super-large displacement, the shortcomings of metal are completely exposed-short fatigue life, high cost and limited installation. At this time, non-metallic compensators (that is, non-metallic expansion joints, including fabric fiber expansion joints, rectangular non-metallic expansion joints, rubber compensators and rubber PTFE compensators) have become life-saving straws. Why? Look down.

If metal can't carry it, why can non-metal carry it?

The greatest confidence of non-metallic compensators comes from the materials themselves. The temperature resistance range is ridiculously wide-some fabric fibers expand and save energy to work for a long time above 1000℃, and metal bellows start to swing when they reach 600℃. In terms of corrosion resistance, in the face of acidic and alkaline flue gas and desulfurization system, stainless steel can't bear pitting corrosion, but PTFE compensator is like nothing. More importantly, non-metals can absorb multi-dimensional displacements-eating them all in axial, transverse and angular directions, unlike metal bellows, which are prone to fatigue cracking. Think about it for yourself, as soon as the pipe vibrates, the metal bellows bends back and forth, and the stress concentration point will crack sooner or later; The non-metal loop belt is flexible and can be twisted how you want.

In addition, the weight is light, the load on the pipe support is small, and the installation is also hassle-free. The vibration and noise reduction effect is much stronger than that of metal-this is not metaphysics, fiber fabric itself has damping properties. Two days ago, I met a buddy in a cement factory. He used to use metal corrugated expansion joints, and the noise made workers complain. After replacing them with non-metal expansion joints (fabric fiber expansion joints), the noise directly dropped by 10 decibels.

Five scenes, metal is really bad

Specific to actual projects, non-metallic compensators are almost just needed in several industries, and hard metal is to find trouble for yourself.

1. Power station industry: front and rear of boiler flue duct and desulfurization flue gas baffle door

The flue gas temperature of the power station is high, and the sulfur-containing corrosion is heavy. In the desulfurization system, the temperature of the pipelines in front and behind the flue gas baffle door fluctuates greatly, and there is still a large amount of acidic condensate in the medium. Would you try it with a metal corrugated expansion joint? Corroded perforations in a few months. Non-metallic expansion joints (specifically rubber PTFE compensators or PTFE compensators) are acid and alkali resistant and can absorb large displacements. The desulfurization flue gas baffle door of this station is a standard flue configuration with non-metallic compensator.

2. Cement industry: hot air ducts at the head and tail of the kiln

At the head and tail of the cement rotary kiln, the temperature fluctuates drastically and the amount of dust is extremely large. The surface of metal bellows is easy to accumulate dust. Once the ash block falls off and gets stuck in the corrugation, the expansion joint will be wasted. The surface of the non-metallic compensator is smooth, the dust is not easy to adhere, and it can adapt to frequent temperature changes. Cement industry metal corrugated expansion joints are also available, but only in branch pipes with lower temperatures and less dust. Trunk hot air duct, honestly use non-metal.

3. Iron and steel industry: blast furnace gas pipeline, dust removal system

Blast furnace gas pipeline contains a lot of dust and corrosive gas. Although the temperature is not high (usually 300-500℃), the medium is extremely corrosive. The life of metal bellows here is generally less than a year. The non-metallic compensator (fabric fiber expansion joint) with the guide tube can effectively isolate the medium and easily double the life. The dust removal system is the home field of non-metals-low pressure, large displacement, serious wear, and the rubber compensator is cheap and doesn't feel distressed to change.

4. Chemical industry: acid-base media pipeline

Concentrated sulfuric acid and concentrated hydrochloric acid run in the chemical pipeline, and even if the metal hose is lined with PTFE, it is inevitable that there is a risk of pinhole leakage. The rubber PTFE compensator in the non-metal compensator is made of PTFE composite material as a whole, which is corrosion resistant and has no dead angles. Moreover, low-pressure pipelines do not need to bear much pressure, and non-metals are completely enough.

5. Rectangular large section flue

Many flue gas pipelines are rectangular, such as the inlet and outlet of desulfurization towers in power stations. Although the metal rectangular expansion joint can be made, it is expensive, heavy and difficult to install. Designed for rectangular flues, the rectangular non-metallic expansion joint is lightweight and compensates for less than half the price of metal. Which do you want to choose?

The structure is not so mysterious, and the core of the selection is a few points

Non-metallic compensators typically consist of non-metallic loop belts (fabric fiber, rubber or PTFE composite) and metal frames (deflectors, platens, bolts, etc.). The rectangular non-metallic expansion joint in our product line is specially equipped with rectangular flue, while the rubber compensator and rubber PTFE compensator are biased towards low-pressure, corrosive liquid or gas pipelines. Don't look at the fancy name when selecting the model. The core is to look at the medium temperature, pressure, chemical properties, and the displacement required by the pipeline. For example, the desulfurization system should not use ordinary rubber, but use an acid-and alkali-resistant PTFE compensator. Otherwise, the rubber will be softened by corrosion, and it will leak in less than two months.

It's not a panacea. High pressure and low temperature still depend on metal

Nonmetallic compensators aren't panacea either. If the pressure is too high (say over a few MPa) or the temperature is extremely low (cryogenic embrittlement), it won't be able to handle it. What about that? Metallic, such as general-purpose corrugated expansion joints or high-temperature axial expansion joints. There is no absolute choice of who is better or worse, only whether it is suitable or not. After all, the national standard JB/T 12235-2015 also makes it clear that non-metallic expansion joints have clear technical boundaries. What we do in engineering is to choose the most cost-effective plan within the boundaries.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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