Specialized in manufacturing compensators, expansion joints, baffle doors

Two days ago, I met a customer. The corrugation of the expansion joint of a high-temperature steam pipeline in their factory was obviously a little crooked, but it didn't leak, so I wanted to last until the maintenance period. As a result, it didn't last until it broke in the middle of the night, and the whole line stopped. This is not an exception.

Three variations, distinguish first and then judge

Do you want to find out the deformation and scrapping standard of metal expansion joint? The first step is not to measure the dimensions, but to distinguish the deformation properties. Elastic deformation, can rebound after displacement recovery, this does not constitute scrapping; Plastic deformation is permanent deformation, and the wave distance can't go back if it is elongated. However, slight plasticity may not fail immediately, so we must continue to observe it. The real danger is instability deformation-the bellows buckles laterally or distorts in the plane under the action of pressure, and the corrugations seem to have been screwed, which is basically directly judged. GB/T 12777 and EJMA specifications give design guidelines, telling you how to calculate when designing, but on-site judgment depends on specific measurement and observation.

Hard indicators for on-site disposal judgment

On-site judgment on several hard indicators, reach any one directly change:

• The wave pitch variation of bellows exceeds the design value by more than 15%, or the wave height has obvious local depressions/bumps;
• Cracks, penetrating corrosion, pitting and perforation appear on the bellows surface;
• Signs of cracking in the connection or end welds.

These do not meet the condition of "making do with it". Many masters can make a rough judgment just by looking at the shape of the ripples-the troughs are squeezed together, the peaks collapse, and the ripples are obviously asymmetric-but it is more reliable to measure the wave distance with a caliper and check the gap between the troughs with a gauge.

Invisible deformation is more dangerous than thought

Pressure-induced plane instability and column instability. The manifestation of plane instability is that a certain wave bulge of the bellows is convex, as if it is blown up alone; Column instability is the whole bellows bending to one side. These two instabilities don't leak immediately, but the bellows have lost their ability to absorb displacement, and continued service will only accelerate fatigue fracture. In this case, it is recommended to replace it directly regardless of whether it leaks or not. If the lateral displacement exceeds the limit, which causes the end flange to deflect, it is necessary to combine the tie rod and hinge structure to judge whether it is damaged jointly-for example, the single hinge of the transverse expansion joint of the compound hinge is worn out, and the whole structure is stressed incorrectly.

Different working conditions have different scrap scales

The scrap scale corresponding to different working conditions varies greatly. In the high-temperature creep environment, even if the deformation of bellows is less than 15%, the cumulative creep deformation continues to increase, so the remaining life should be considered. Uniform thinning to the lower wall thickness limit in corrosive media is more dangerous than simple deformation. There are also stainless steel bellows that are prone to stress corrosion cracking in chloride ion environment-this kind of crack is often penetrating, and the appearance deformation may not be obvious, but it has been wasted. So don't just focus on the size, the material and media environment should be looked at together.

Pits that are easy to step on in practice

Someone screwed the tie rod nut to "correct" the deformation. As a result, the displacement that should be freely absorbed became a binding force, and the force distribution of the bellows changed completely, accelerating the failure. Others forcibly fix the bellows by welding steel plates on the outside-this operation will change the original flexible compensation path of the bellows. It looks like it is fixed, but it is actually creating a new stress concentration point. In addition, the guide tube wears out or falls off. Although the bellows itself is not deformed, the medium directly washes the trough, which will soon reduce the leakage, which is also an indirect signal of scrapping. In daily inspection, priority is given to the outlet of the guide tube, the low point of the bellows and the trough position near the bracket, which have the most problems.

Finally, give a bottom line

If your measured deformation data does not meet the standard, or you are unsure whether it is unstable, then it will be disposed of as scrapped. The cost of replacing a metal expansion joint is much lower than the cost of downtime for maintenance caused by pipe leakage. Especially for high-temperature axial expansion joints and straight pipe pressure balance expansion joints used in key pipelines, once the bellows fails, the consequence is not as simple as leakage. Don't wait until you miss it before you regret it.

Find out first: How did pre-compressed 50% come from?

When many on-site masters heard about the installation of expansion joints, their first reaction was to "press half first and then talk about it". Where did this habit come from? Some people say that it is to save trouble, some people say that they are afraid of insufficient heat expansion, and others think that the more they press, the more durable the bellows will be. Do you look through the design manual and find the "pre-compression 50%" rule? Can't find it. The expansion joint is not a spring, the displacement capacity of the bellows is a fixed stroke, and the pre-compression of 50% just hard presses the bellows to the middle position, which sounds like a "centering safety" and actually blocks both sides.

Two days ago, I met a customer and told me that the high-temperature axial expansion joint in their factory began to leak after less than half a year of installation. When I removed it, there was a crack at the bottom of the bellows trough. Ask how to pre-press it during installation? The answer is "pressed by 50% as usual". You calculate the actual thermal elongation of the pipe again, and it only takes 20% to press at full load. With this 50% pressed in, the bellows is in the wrong initial position from day one, and it would be weird if nothing happened.

Disadvantage 1: The axial compensation ability is sacrificed, and the bellows will be broken if the thermal displacement of the pipeline is slightly larger

What does it mean to pre-compress 50%? Assume that the rated axial displacement of the bellows is ±40mm and the total stroke is 80mm. If you press 40mm in advance, the remaining compressible stroke is only 0, and the stretching stroke is only 40mm. What if the actual thermal expansion of the pipe is 50mm? The bellows was either pressed to the limit or pulled overhead, and the crest of the wave cracked directly. Products such as general-purpose corrugated expansion joints and high-temperature axial expansion joints have a good displacement range when they leave the factory. The amount of pressure should be calculated according to the actual thermal displacement, which is not one size fits all.

Amount of pre-compression = (actual working displacement/2) - (displacement that has occurred at installation). It's better for you to press 50% when you come up, which is equivalent to throwing half of the compensation ability calculated by the design institute. For example, if you buy shoes in size 43, but don't wear a size 42, you still say "it will loosen after you hold it up"-who do you blame for worn feet?

Disadvantage 2: The corrugated pipe is in a high stress state for a long time, and the fatigue life falls by a cliff

Bellows absorb displacement by elastic deformation of wave peaks and valleys. Pre-compressed by 50%, the trough is pressed deeper, the crest is stretched more open, and the stress level does not rise linearly, but doubles up. For stainless steel bellows, the direct problem caused by high stress is stress corrosion cracking-even if there is a little chloride ion in the medium, the crack can penetrate the wall thickness in a few months.

Some people take "pre-compression can extend life" as an example, so don't be led off. What are the conditions for pre-compression to extend life? It is the amount of pre-compression that just offsets the cold tight displacement during installation, allowing the bellows to return to the middle position during operation. For example, the installation temperature of the pipeline is 20℃, the operating temperature is 200℃, and the calculated elongation is 60mm. When the pipeline is installed, it is pre-pulled or preloaded by 30mm, and it just completes half a cycle during operation. This is called "cold tightness", not "blind pressure". If you press 50%, if it does not match the calculated value, the bellows will always work in an over-limit state, and the fatigue life will be directly reduced by an order of magnitude.

Disadvantage 3: Instability or buckling is easy to occur after installation deviation and medium pressure are superimposed

In addition to absorbing displacement, bellows have to withstand the thrust generated by internal pressure. After 50% pre-compression, the initial deflection of the bellows is already present and a large chunk of the stability margin is eaten. At this time, once there is pressure fluctuation, water hammer, or even just normal pressure fluctuation in the pipeline, the bellows may become laterally unstable-the pipe itself does not move, and the bellows itself "bulges". Instability is not slowly leaking, but instantaneous twisting and deformation, and the whole pipeline system has to stop.

Particular attention should be paid to directly buried expansion joints and externally pressurized single axial expansion joints, which have strict limitations on pre-deformation. There is soil constraint around the direct buried type, and if it is pressed in the wrong direction, the lateral force of soil will directly crush the bellows; External pressure single axial type external pressure bellows itself works in the reverse state. If you precompress it by 50%, it will add insult to injury. The pre-deformation data in the installation manual are calculated by the manufacturer one by one, not copied.

So how much exactly should we pre-compress?

Amount of pre-compression = (actual working displacement/2) - (displacement that has occurred at installation). It is recommended that you copy this formula next to the device. For example: the maximum thermal elongation of the pipeline is calculated to be 80mm, and it has been elongated by 10mm at ambient temperature during installation, so the pre-compression amount is 80/2-10=30mm. This is called on-demand preloading.

If the pipeline has no thermal displacement at all, such as some lined pipelines, the pre-compression amount is 0, and compression instead creates stress. If it is cold after installation and heats up after operation, the pre-compression amount should be greater than 0. On the contrary, if it is installed in a hot state and cools down after operation, it has to be "pre-stretched", not compressed.

Finally, let's be honest

Expansion joint pre-compression is a technical job, not a matter of patting your head to set proportions. If you have installed a pre-compressed 50% expansion joint, quickly go through the running record to see if there are any abnormalities in temperature and pressure, and then squat down to see if there are any cracks, bulges or scratches on the bellows surface. If you find anything wrong, contact the manufacturer immediately for re-accounting. If you haven't installed it yet, you are unsure about the selection or installation. Don't be superstitious about the "experience value" of the old master. Find an expert who makes expansion joints to calculate it with a calculation book, which will save much money than changing the pipe afterwards.

First, let me answer the most straightforward question: Non-metallic compensators are not universal

It's not like standard flanges or bolts, which can be fitted when you take them to the right size. The design logic of non-metallic compensator (that is, we often call non-metallic expansion joint and fabric fiber expansion joint) is tailor-made around the working conditions-temperature, pressure, medium, displacement and installation space, each of which directly determines the structural selection and material matching.

If you take a non-metallic compensator used in the flue of a power plant and install it on the cold air duct of the cement industry, something will probably happen. It's like buying shoes, size 42 feet will make do with a size 43, but let you run a marathon in rain boots, try it?Are non-metallic compensators universal? The answer is clear: not universal.

Then why do some people always think it's "universal"?

Because from the appearance, the non-metallic compensator is just a circle of skin and frame, which seems to have little technical content. Actually, the skin is a layered structure: fluororubber, silicone rubber, PTFE, ceramic fiber, fiberglass cloth, and each layer has its own task-temperature resistance, corrosion resistance, pressure bearing, sealing.

Although they are all non-metallic expansion joints, the number of skin layers can differ by several layers between those used behind the smoke baffle door and those used next to the high-temperature axial expansion joint. The same is true for rubber compensators and rubber PTFE compensators. The PTFE layer is specially used to deal with strong corrosive media. If you use an ordinary rubber compensator to pass concentrated sulfuric acid, it is not a type selection, but a mine planting for the pipeline.

Let's talk about the displacement compensation ability

Axial expansion, lateral deflection and even angular displacement can be done, which is incomparable to metal corrugated expansion joints. But how much it can absorb depends on the design. Rectangular non-metallic expansion joints are usually used in rectangular smoke ducts, and another set of algorithms is matched with circular baffle doors.

You can't regard all non-metallic compensators as universal parts just because of the nominal "large displacement". The pre-deformation amount, the setting of the guide tube and the stiffness of the frame given in the design all directly affect the actual compensation effect. Two days ago, I met a customer who used the double-hinged expansion joint originally designed for air-cooled island vacuum pipeline on ordinary hot air pipeline. As a result, the vibration exceeded the standard-that thing was metal, not an occasion where non-metallic compensators could be replaced casually. On the contrary, non-metallic ones could not be used everywhere.

The installation location and environment cannot be ignored

Non-metallic compensators are common in desulfurization systems, dust removal systems, power station flues and cement production lines, because of large temperature fluctuations, dust and corrosive gases in these working conditions. But if you use it on pipelines with vacuum requirements, you have to weigh it-the non-metallic skin has limited pressure bearing capacity, and it is easy to deflate under negative pressure conditions. At this time, you may have to look at the vacuum special hose or the external pressure single axial expansion joint.

In other words, before selecting a non-metallic compensator, first list the working condition parameters clearly: what the medium is, how high the temperature is, whether the pressure is positive or negative, whether there is acid-alkali corrosion, which is the displacement direction of the pipeline, and whether there is any space limit in the installation position. Only when these parameters are all together can the manufacturer give you the appropriate skin material and structure. If one parameter is missing, the scheme may deviate.

In the final analysis, the non-metallic compensator is a "non-standard custom" flexible connector

It does look similar in many industries, but material formulations, structural details, and connection methods vary widely. The real professional approach is to find the manufacturer to come up with a plan with the working condition parameters, instead of taking a photo to draw a ladle with a gourd. The national standard JB/T 12235-2015 only stipulates the technical requirements and test methods, and does not say that you can install it everywhere if you buy a standard product.

Are non-metallic compensators universal? — Not universal. But you treat it like a custom piece, and it can dry better than a metal compensator under the right conditions. When it comes to model selection, it is never about looking at pictures, but about data.

Next time someone tells you, "Just buy a nonmetallic compensator and install it", ask him: What is the working temperature? Does the medium contain sulfur? What is the displacement amount? If he can't answer it, you can treat it as a joke.

What is the thrust when the blind plate is blocked? Calculation method of thrust of blind plate of expansion joint

When pipeline pressure test, purging or system isolation, once the blind plate is sealed, the medium pressure directly acts on the cross section of the blind plate. This force is transmitted along the pipe to the expansion joint, the bracket, and the fixing point. You go to the site and look at the pipe sections that have problems-the expansion joint tie rod is bent, the bracket is displaced, and the fixing point weld is cracked-nine times out of ten, the root cause is the blind plate thrust is not clearly calculated.

The essence of blind plate thrust is that the pressure acts on the area to produce an axial force. The formula is spread out in one sentence:F = P × A。 F is the blind plate thrust in N; P is the medium pressure in MPa; A is the effective pressure area of the blind plate in mm². However, in practice, how to take a and which value to use P are all particular.

The formula itself is not complicated, but the complexity lies in the value of the parameter

F = P × A, Anyone can write this formula. The difficulty is: Is the diameter of the blind plate calculated according to the inner diameter of the pipe or the middle diameter of the sealing surface?

In most cases, the blind plate is installed between two flanges, and the medium pressure acts on the gasket sealing position, which is the middle diameter of the flange sealing surface, not the inner diameter of the pipe. Take DN400 pipe as an example. The inner diameter is 400mm, and the medium diameter of the sealing surface may reach 410mm. The area difference between the two is about 5%. On high-pressure pipelines, this gap is converted into thrust of several tons.

If the expansion joint is close to the blind plate, the bellowsEffective areaIt should also be included in the calculation. The effective area of the bellows is the equivalent area of the axial thrust generated by internal pressure on the bellows. This value is directly given in the product sample, and it is taken according to the manufacturer's data, so there is no need to push it yourself. Universal corrugated expansion joint, straight pipe pressure balance expansion joint, compound hinge transverse expansion joint, all types of samples have this parameter. Can't find it? Call the manufacturer to ask for it, don't estimate it yourself.

Different types of expansion joints have completely different force paths

The same blind plate thrust, mounted on the general corrugated expansion joint and mounted on the straight pipe pressure balance expansion joint, the calculation result may be the same, but the force distribution is very different.

The universal corrugated expansion joint itself has no self-restraining ability, and the bellows will produce a great axial thrust under the action of pressure, which is all borne by the main fixed bracket. In other words, if the bracket can't hold it, the expansion joint will be installed in vain. Two days ago, I met a customer. The steam pipeline of DN500 in the workshop was pressure tested, and the blind plate was sealed. The general corrugated expansion joint tie rod next to it was directly bent into a bow, because the bracket was not designed according to the thrust.

Straight pressure balanced expansion joint is different. It relies on its own working bellows and balanced bellows to offset the internal pressure thrust. The blind plate thrust is mainly carried by the equipment itself, and the requirements for fixed brackets are much smaller. The double hinge transverse expansion joint bears the internal pressure thrust by the tie rod, but it can only absorb the transverse displacement, and the blind plate thrust will still be transmitted to the bracket. The structure of external pressure single axial type expansion joint determines that it has strong external pressure capacity, but it can't reduce the thrust of blind plate.

This expansion joint you used, can it withstand blind plate thrust, or can it only absorb displacement? This question is asked wrong, and there is all trouble behind it.

Several Key Corrections in Practice

The test pressure tends to be higher than the operating pressure. For pipelines with a design pressure of 1.0MPa, the hydraulic test may be 1.25 times or even 1.5 times. At this time, the blind plate thrust must be calculated according to the pressure test pressure, not according to the operating pressure. It is quite safe to calculate according to the operating pressure. When you press it, the bracket will be wasted directly.

The temperature correction cannot be ignored either. When high-temperature pipeline is running, the allowable stress of materials will decrease. If the allowable stress at normal temperature is used in the calculation of blind plate thrust, it must be reduced accordingly under high-temperature working conditions. How to take the safety factor? It depends on the type of bracket-the fixed bracket is generally 1.5, and the guide bracket and sliding bracket are 1.1 to 1.2. Don't blindly enlarge it, and don't stiffen a coefficient. How much should be taken according to the actual working conditions.

Example: A DN400 steam pipeline

Assume a DN400 steam pipeline with a design pressure of 1.6MPa and a hydraulic test pressure of 2.0MPa. The inner diameter of the tube is about 400mm, the middle diameter of the sealing surface of the blind plate is 410mm, and the area is about 132000mm². Calculated at 2.0MPa:

F =2.0×132000=264000 N, Approximately 26.9 tonne force.

That's not a small number, right? If a general-purpose corrugated expansion joint is installed on the pipeline, the main fixed bracket must solidly hold the thrust of 26.9 tons; If replaced with straight pipe pressure balance type expansion joint, the force of the support can be reduced greatly. This comparison tells you directly: the calculation of blind plate thrust is not just a mathematical problem, but directly determines the bracket design and expansion joint selection.

Three of the easiest things to overlook on the scene

First, is the temporary bracket near the blind plate strong enough during pressure test? Many temporary brackets are welded with several steel pipes, which look quite stable, but when calculated as thrust, it is completely insufficient. Don't save this.

Second, is the limit device that comes with the expansion joint adjusted in place before the pressure test? The tie rod of the double hinge transverse expansion joint is loose when it leaves the factory, and the nut must be locked tightly before pressure test. If you don't lock it tightly, the pull rod will push the bend directly during the pressure test, and it will be too late to cry.

Third, the blind plate should be positioned a little farther away from the expansion joint, so that the thrust can first pass through the natural corner of the pipe to digest a part. If it can't be avoided, it is necessary to add a temporary fixing bracket between the expansion joint and the blind plate.

Calculation method of blind plate thrust of expansion joint? After all, F = P × A, the formula itself is worthless. What is valuable is that you know when to use which P, which A, and who exactly carries the calculated force. Understand these, and then talk about the design of the bracket and the selection of the expansion joint, so that it is not easy to go wrong.

Nine times out of ten people in the dry plumbing business have dealt with expansion joints. But if you ask what the process principle of non-metallic compensator is, many people will be stunned for a moment, and then say vaguely: Isn't it just a piece of cloth sewn in a circle? Alas, if this is heard by the old master of dry craftsmanship, he can laugh angrily.

Non-metal compensators and metal expansion joints, who does whose work? The metal expansion joint absorbs the displacement by the deformation of the bellows, has high pressure resistance and long life, but it is sensitive to fatigue and has nothing to do with corrosive smoke. Non-metallic compensator is different, it relies on multi-layer flexible fabric to bear displacement, corrosion resistance, high temperature resistance, large compensation amount, especially suitable for large-diameter low-pressure pipeline. The non-metallic compensator can just catch the large displacement and corrosive medium that the metal expansion joint can't carry. The two are not a substitution relationship, but a division of labor relationship-metal work, non-metal really can't do it; Nonmetal work, metal really can't catch it.

Skin is not a piece of cloth: What role does each layer play in a multi-layered composite structure

The skin is the core of a non-metallic compensator, but it is never a single-layer structure. You go and take a look at the non-metallic expansion joint (fabric fiber expansion joint) of a regular manufacturer. The skin is at least four or five layers from the inside to the outside, and each does its own thing.

The innermost layer is a temperature-resistant layer, which directly contacts the medium, either silicone rubber glass fiber cloth or fluororubber composite cloth, which is responsible for one thing: blocking high-temperature smoke. In the middle is the insulation layer, usually with ceramic fiber blanket or glass fiber wool, to trap the heat and prevent it from jumping out. Further outside is the structural reinforcement layer, high-strength glass fiber cloth or polyester canvas, which bears the tensile force and ensures that the whole skin is not torn apart. The outermost layer is a weather-resistant layer, fluororubber or silicone rubber coating, which is anti-UV, anti-aging and rainwater erosion.

How to fit between layers? It's not just brushing glue and sticking it. There is a parameter called peel strength in the composite process. What range will be controlled by regular enterprises? There are test records before leaving the factory. You take a piece of skin that has been used for a year and tear it apart. If the layers are cleanly separated, then the composite pressure is not enough at the beginning, and the temperature is not in place.

Skeletons and frames: What makes soft connections hold up to the pressure? There's something special about it here

The skin itself is soft, so what does it rely on to keep its shape? By the skeleton. The frames of non-metallic compensators are generally divided into two types: one is a metal frame, welded with angle steel and channel steel, wrapped around the skin, and bearing the internal pressure thrust and moment; The other is an internal guide tube, which is inserted inside the pipeline to guide the flow direction of the medium and protect the skin from being directly washed by the airflow.

There must be a gap between the guide tube and the skin. Some people don't understand and think that the tighter you lean against it, the better the seal. On the contrary, the skin deforms when it works, and if the guide tube presses against it, it will wear out in a few movements. The size of the gap is particular, and it is calculated according to the displacement and medium temperature during design, not determined by slapping the forehead.

How to connect frame and skin? Most are compressed with strips and bolts. The spacing between bolts will not be too large, and it is easy to leak if it is too large; It's also not too small, too small to install troublesome. If you look at the four corners of the rectangular non-metallic expansion joint, that position is most prone to problems-there are many skin folds at the corners, and the pressing force is uneven. If you steal a little work, it will start to leak after a year and a half. Therefore, a better manufacturer will thicken the strip at the corner, or use an arc transition, which is a real skill in technology.

From blanking to molding: What are the key steps of the process of non-metallic compensator?

The blanking of non-metallic compensators is not difficult or simple. The round one is easy to handle, just expand it and count it as a fan; The rectangular one is troublesome. The four corners have to be cut, and the incision angle and overlap length are all particular. The material is not cut correctly, and the skin is full of pleats when it is loaded, and it won't take long to crack from fatigue.

In the molding stage, the most critical process is the press-fitting of skin and flange. Before pressing, a sealing strip should be placed on the flange surface, and then the skin should be placed on it, and the tension around it should be adjusted to be uniform, and then it should be gradually pressed with pressing strips and bolts. This "step-by-step" is important-you have to twist the bolts diagonally alternately and press them into place three to four times. If you press them too fast or too hard, the internal fibers of the skin will be unevenly stressed, and the local stretch will be overstretched, which will greatly reduce the life span.

What about welding? To say welding is also a key step. Should frame welds be fully welded or intermittently welded? Most manufacturers do intermittent welding, because the frame will deform during use, and full welding is easy to crack. However, the splicing corners of the frame must be fully welded, where the force is concentrated, and intermittent welding can't bear it. These details, the drawings won't tell you at all.

By the way, there is also the pressure test before leaving the factory. Pressure testing is not as simple as hitting it with an air pump to see if it leaks. According to JB/T 12235-2015 standard, non-metallic expansion joints should be tested for airtightness, and there are clear requirements for pressure holding time and test pressure. Some factories try to save trouble. Even if there is any bulge on the surface of the skin with the naked eye, it is done. What can this find out? The needle eyes and tiny holes in the inner fibrous layer are simply invisible to the naked eye.

Principle: Why is non-metallic compensator the first choice in power plant desulfurization and cement flue?

Say response to use. The temperature of the flue gas in the desulfurization system of the power plant is not extremely high, but it contains sulfur, chlorine and a large number of slurry particles, which is highly corrosive and abrasive. Metal Expansion Joints In this environment, bellows are quickly corroded and perforated. The skin of the non-metallic compensator is fluororubber composite glass fiber cloth, which is naturally acid-and alkali-resistant. In addition, the guide tube separates the airflow, and the use environment is bad. It can still last for three to five years.

What about the cement flue? Mainly due to large dust and large temperature fluctuations. The kiln tail flue gas can reach 400℃, and the temperature changes drastically when the machine is started and shut down. Thermal fatigue cracks of metal expansion joints are common under this working condition. The non-metallic compensator itself is flexible, and the thermal stress can't be transmitted at all. Moreover, the insulation layer of the skin can effectively insulate the temperature, and the frame temperature will not be too high.

There are also those installed next to the desulfurization flue gas baffle door at the flue outlet, which have a narrow space and complicated pipelines. The non-metallic compensator can be made into a rectangular and non-standard shape, which takes up little installation space and is convenient for maintenance. Would you like to try a different metal expansion joint? For such a large bellows assembly, there is simply not enough maintenance space.

To put it bluntly, the process principle of non-metallic compensator is not so mysterious, that is, the word "flexibility" is made to the extreme: the temperature, corrosion and displacement are all digested by multilayer composite materials, and then the pressure, erosion and structural stability problems are covered by metal frames and guide tubes. However, the more simple things sound, the more details hide the door. Those invisible press-fit tensions, compound temperatures, and bolt tightening sequences are the watershed that determines whether it will last for three or ten years.

When you purchased the non-metallic compensator, did you ask the manufacturer about the thermal aging data of each layer of material of the skin? If you haven't asked, remember to ask next time. With this question, half of the suppliers who only know how to fight prices can be screened out.