Specialized in manufacturing compensators, expansion joints, baffle doors

Two days ago, a customer called and asked, "Which is the radial direction of the expansion joint?" I asked him back, did you use the arrow as a radial reference when you installed it? He froze for a moment. In fact, this problem is particularly typical. Many field engineers and technicians will confuse radial and axial directions. The consequence of confusion is very direct-the selection is wrong, the pipeline will still be broken after installation, and the compensator will be installed for nothing. Today, let's make this direction clear at once.

Let's make it clear: What is radial?

The radial direction of the expansion joint refers to the direction perpendicular to the centerline of the pipe, that is, the direction radiating outward from the center of the circle. For example, if you take a round tube, the direction along the length of the tube is axial, the direction around the tube is called circumferential, and the radial direction is along the radius, pointing from the inner wall to the outer wall. Used on expansion joints, radial displacement is the compression or stretching of the bellows in a direction perpendicular to the axis. For example, when the pipeline shifts up and down or left and right, the compensator bears radial displacement. Isn't it intuitive? But why do 90% of people do the opposite? Because everyone stares at the "axial direction", the main direction of thermal expansion and contraction, ignoring the lateral offset.

What does the direction of the arrow on the expansion joint mean?

Many products, such as general-purpose corrugated expansion joints and high-temperature axial expansion joints, will be marked with an arrow on the shell. This arrow points to the direction of the medium flow, and it also reminds you that the expansion joint mainly compensates for axial displacement-that is, thermal expansion and contraction in the direction of the arrow. Arrows are not radial markers. There are no arrows in the radial direction, because the radial displacement is absorbed by the lateral stiffness of the bellows, and the amount of radial compensation allowed by expansion joints of different structures varies greatly. And guess what? Some customers took the arrow as a radial reference, and forced the expansion joint to be crooked. As a result, the bellows was twisted into a twist before it was pressurized. Alas, sorry for the tube.

What kind of expansion energy saving carries radial displacement?

Look at the type. For example, the compound hinge transverse expansion joint is specially used to absorb transverse (radial) displacement. Its structure has two sets of bellows plus hinges, so that the tube can swing in the vertical direction. There are also expansion joints of large tie rod structure (such as straight pipe pressure balance expansion joints). The function of tie rod is to limit axial displacement and guide compensation force to radial direction. Conversely, like external pressure single axial expansion joint, its design mainly eats axial displacement, radial capacity is very weak. When selecting, if the direction is reversed, the bellows will be twisted, and the flange will be cracked. This is not to scare people. There have been enough accidents at the scene to write a case book.

How to judge in actual operation?

Here are three stupid ways for you to remember and not step on pits:

• First, look at the product nameplate or drawings.It will be marked with "lateral compensation amount" or "radial displacement", generally in millimeters. If not, look for the technical parameter table, which is written separately in the axial and radial directions.
• Second, find the guide tube of the expansion joint.The guide tube is usually along the axis direction. If there is a significant gap between the guide tube and the inner wall of the pipe, this expansion joint allows certain radial deflection. On the contrary, with minimal or even no clearance, it is a pure axial type.
• Third, look directly at the structure.There is a high probability that those with tie rods and hinges can eat radial, while those without such constraints are mostly pure axial. For example, in our products, compound hinge transverse expansion joint and straight pipe pressure balance expansion joint are good at radial compensation, while general-purpose corrugated expansion joint and external pressure single axial expansion joint should not be expected to carry radial direction.

Whichever of these three methods you use is better than blind guessing. One more detail: How to adjust the expansion joint tie rod nut? If you buy the model with a tie rod, be sure to loosen the tie rod nut to the designed position before installation, otherwise the tie rod locks the radial displacement and becomes a rigid connection. For specific adjustment methods, please refer to the FAQ of this site.

One last word of reminder

Don't use the radial direction as the axial direction, and don't expect a general-purpose expansion energy saver to hold a few millimeters of pipe misalignment. When installing, if you find that there is a deviation from the pipeline and forcibly tighten the expansion joint with bolts to make do, you are sentencing the bellows to death. The correct approach is to use double hinge transverse expansion joints or large tie rod expansion joints to specifically absorb this radial deviation. I really can't figure it out. Looking through the product information of this site, the displacement parameters of each model are clearly written-how much in the axial direction and how much in the radial direction, at a glance. For example, for straight pipe pressure balance expansion joints, the radial compensation amount is clearly marked in the selection table, so just follow the selection.

Alas, the direction is right, and expansion and energy saving will help you carry it for ten years; If the direction is reversed, it will leak in three months.

What are the expansion joint insulation liner structures? One article clarifies three mainstream schemes

The temperature of the medium in the high-temperature pipeline is always five to six hundred degrees, or even thousands of degrees. When the bellows is directly exposed to this environment, the material strength will drop by a cliff, and the fatigue life will not be sustained. The insulation lining is like putting an insulation suit on the expansion joint, separating the heat source from the bellows. Common scenes: smoke duct of power plant, cement kiln tail, blast furnace gas pipeline of iron and steel plant-if bare bellows are used in these places, they will have to be scrapped in a few months.

What are the expansion joint insulation lining structures? Don't worry, break up the three mainstream schemes and break them into pieces to explain them clearly, with real cases and product benchmarking.

Scheme 1: Lined Castable Structure

This stuff is most common in the cement industry and power station industry. To put it bluntly, a layer of high-temperature resistant concrete is poured on the spot inside the expansion joint, with a thickness of generally 50-150mm. The advantages are high temperature resistance (up to more than 1200 ℃), wear resistance and good integrity. The disadvantages are also obvious-heavy, and the curing cycle of castables is long, so it is anxious to die during emergency repair.

The "Metal Corrugated Expansion Joint for Cement Industry" and "Corrugated Expansion Joint for Power Station Industry" of our station are equipped with this structure as standard, and with the guide tube, it can effectively prevent the medium from directly washing the bellows. However, it should be noted that castable cracking is an old problem, which must be controlled by the design and construction quality of anchors. Two days ago, I met a customer of a cement plant. During the maintenance, I found that the castable was partially peeling off. It was found that the spacing between the anchors was too large. Later, the cloth welding was re-welded at a spacing of 150mm, and there was no accident again.

Option 2: Ceramic fiber/non-metallic insulation

This solution is much lighter, and is mainly used in high temperatures but non-abrasive media. For example, flue gas pipelines and desulfurization systems. The structure is simple: fill ceramic fiber felt or aluminum silicate wool between the bellows and the guide tube, and wrap a layer of stainless steel wire mesh on the outside.

Our "non-metallic expansion joint (fabric fiber expansion joint)" and "rectangular non-metallic expansion joint" use this idea. The advantages are fast installation, low cost and good thermal insulation effect (thermal conductivity below 0.1W/m·K). However, there is a pit-fiber materials are afraid of water vapor, and the performance of flue gas will decay when the moisture content is high, so it has to be matched with waterproof layer. How to prevent it? Usually a layer of PTFE film or stainless steel foil is added on the outside. If the budget allows, go directly to the "PTFE-lined hose" scheme, and you won't be afraid of sour gas.

By the way, don't think that you can choose just because the temperature and pressure are low. There was once a desulfurization project with a temperature of only 150℃, but the condensed water of wet flue gas soaked the ceramic fiber into mud, and it collapsed in three months. Later, it was replaced with aluminum silicate cotton + PTFE cladding, which has not been changed for three years now.

Option 3: Composite thermal insulation lining

This is a combination of the first two schemes, specializing in the treatment of various difficult and complicated diseases. For example, the medium is high temperature and dusty, or the temperature fluctuates violently periodically. Structurally, the innermost layer is castable anti-scour, the middle layer is ceramic fiber insulation, and the outer layer is guide tube to protect bellows.

Two days ago, a customer asked, saying that their pipeline temperature circulated from normal temperature to 800℃, and it cracked in the first week if only castables were used. Later, it was replaced with a composite structure and used it for three years without any problems. Well, the cost is 30% more expensive, but the life span has doubled by 5 times, which is cost-effective.

Composite structures are not simply stacked and done. The difference of expansion coefficient between the layers must be calculated well, otherwise it will be peeled off in layers after several cold and hot cycles. Solution? A layer of stainless steel expansion mesh is added between the castable and the fibers, and the elasticity of the mesh absorbs the displacement.

Don't just look at the temperature when selecting a model

Pressure, media corrosiveness, installation space and maintenance frequency must be considered. For example, desulfurization flue gas pipeline, the temperature is not high but the acid corrosion is strong, so it is better to choose non-metallic insulation layer with PTFE lining. Our "desulfurization flue gas baffle door" and "PTFE-lined metal hose" are for this working condition.

In addition, the thickness and material of the guide tube also directly determine the heat insulation effect-if the guide tube is too thin, it will easily be burned through, and if it is too thick, it will increase the cost. It is recommended that it be determined according to the medium flow rate and particle hardness, generally 304 or 316L, with a thickness of 3-6mm. If the medium contains hard particles (such as coal powder and slag), it is best to add a layer of wear-resistant lining plate, such as high chromium cast iron or ceramic patch, to the inner wall of the guide tube.

Don't forget to reserve access

Access port reserved for insulation liner. Many projects have installed expansion joints, but when they are broken, they find that the lining can't be changed. In the design stage, space should be allowed, or split structure should be used. Our Round Flap Doors (Double Seal) and Manual Insulated Doors have a quick-service design-bolted end caps that remove the liner module.

All in all, thermal insulation lining has no universal solution, it has to be tailored to the working conditions. If you are not sure, directly take the parameters to find the manufacturer to come up with a plan, and don't make it yourself. After all, if the bellows is burned through, it is not as simple as changing a piece-the loss of the whole pipeline may be hundreds of thousands.

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

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

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

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

1. Material: Every layer of cloth is money

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

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

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

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

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

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

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

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

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

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

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

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

How to avoid being pitted when purchasing? Three Practical Tips

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

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

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

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

Want an accurate quote? Just have these four parameters ready

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

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

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

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

Take 10 minutes to figure out where the leak is

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

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

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

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

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

Partial repair or overall replacement? Look at three conditions

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

4. Which industries can't live without it?

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

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

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