Specialized in manufacturing compensators, expansion joints, baffle doors

Why do you have to have regular inspections? — Don't wait until you miss it to regret it

Two days ago, I met a brother from a power plant. Their desulfurization tower was exportedNon-metallic expansion joints (fabric fiber expansion joints)Suddenly it was torn, and the hot smoke was wrapped in slurry and directly leaked out. After the production line was stopped for 3 days, the light loss was a small million. You say it was wrong or not? In fact, this kind of accident can be completely avoided-as long as it is checked regularly, it will only take a few hours to replace one if the signs of aging of the fabric layer and corrosion of the metal frame are found in advance.

Non-metallic compensators (also called non-metallic expansion joints and fabric fiber expansion joints) are widely used in smoke and air ducts, desulfurization systems and cement production lines, because they are resistant to high temperatures, corrosion resistance and can absorb large displacements. However, its soft belt is tossed by high temperature, dust, acid and alkali gases all the year round, and its aging rate is much faster than that of metal parts. When you see air leakage, smoke leakage and abnormal noise before dealing with it, the internal structure is often hurt. SoHow to check a non-metallic compensator?This problem is actually one of the core lessons of pipeline maintenance.

Appearance inspection: Seeing, touching and listening, three steps to find out the big fault

Look-scan details with your eyes

Standing on the side of the compensator, first look at the surface of the fabric for bulging, scratches, fluffing, and whitening. Bulging usually means debonding between layers, and scratches deep may have damaged the inner PTFE or rubber film. Pay special attention to the corners of rectangular non-metallic expansion joints-that position has the most stress concentration and is most likely to crack first. Look at whether the metal flange is corroded and the weld is cracked.

Touch-to feel with your hands

Put on the gloves and touch the circle along the surface of the circle band. If it feels hard and sticky locally, it means that the material has degraded. Rubber compensator or rubber PTFE compensator is especially afraid of this-it will be brittle and cracked when it is hard, and it will be corroded by the medium when it is sticky. The normal feel should be uniform elasticity and smooth surface.

Listen-Find abnormalities with your ear

When the equipment is running, get closer and listen to whether there is a hissing air leak or a puff bulge. Experienced masters know where they leak as soon as they hear it-the hissing sound is mostly due to the fabric needle eye being enlarged, and the puff sound may be the displacement of the internal cushion.

After these three steps are completed, 70% to 80% of the surface problems can be found out. However, some internal injuries have to rely on these methods.

Dimension and displacement compensation ability check-measure to know whether there is failure

Nonmetallic compensators are not only soft connections, they absorb the thermal expansion and mechanical displacement of the pipe. Think about it, the pipe can stretch tens of millimeters when it is hot, and it all depends on this soft guy's deformation to digest it. If it loses its elasticity due to aging, or does not leave enough margin during installation, the consequence will be pipe stress hard top, flange crack, or even equipment.

How to check? Simple: Measure the actual length and width of the compensator under shutdown, and compare with the factory design dimensions. If the amount of compression has exceeded 80% of the design maximum, or the amount of stretch is almost to the end, then you have to consider replacing it. Common standards, such as JB/T 12235-2015 "Non-metallic Expansion Joints", specify the displacement limit and fatigue life.

In addition, don't forget to look at the guide tube (if any) -the specific function of the expansion joint guide tube is to protect the fabric from being washed by high-speed airflow. If it corrodes and collapses, the compensator life is directly discounted in half.

Sealability and airtightness test-a dozen pressures, all leaks appear

The front ones are all visual and feel, and the real tough battle is the airtightness test. Especially in the desulfurization flue gas baffle door, air-cooled island system and other occasions with high sealing requirements, the high air leakage rate not only increases the energy consumption, but also may lead to scaling and corrosion of peripheral equipment.

Close the valves on both sides of the non-metallic compensator, seal one end with a blind plate, and give 0.05~0.1MPa compressed air to the other end (don't overpressure, the fabric can't bear to rush), and then coat each seam, flange surface and bolt hole with soapy water. Where bubbles are the leakage spots.

Before the test, confirm that the compensator has no obvious bulge or tear, otherwise it will collapse directly when the wind takes a dozen, which will be dangerous. The pressure holding time should be at least 5 minutes, and the pressure should not drop before it is qualified. If there are not many leaks, you can try to plug them with special repair glue; But if the fabric leaks in a large area, or several leaks are strung together, don't toss it, just replace it with a new one.

Judgment and treatment of common faults-which can be repaired by themselves and which must be replaced

Come on, go straight to the dry goods:

• Small scratches and slight fluffing on the fabric surface: Apply a layer with silicone rubber or fluororubber repair agent, and it can top for a while when it dries. However, the premise is that the covering layer is not damaged, and the medium temperature does not exceed the temperature resistance range of the repair agent.
• Air leakage due to loose flange bolts: This can be tightened by itself, and the torque value is tightened 2~3 times in diagonal order. Don't screw to death at once, it will easily deform the flange.
• Local bulging and delamination of circular zone: It indicates that the fabric and inner layer have been detached. Don't fix it, just change it. Because the bulge will get bigger and bigger and break sooner or later.
• Metal frame corrosion perforation: Look at the corroded area. If it is only a small piece, you can apply anticorrosive paint after repair welding and polishing; If a large area is thinned, the whole frame has to be replaced.
• Fabric distortion due to displacement exceeding limit: First check whether the pipe support is displaced or the original selection is too small. If it is a bracket problem, adjust the bracket; If it is a type selection problem, the expansion joint with a larger compensation amount must be replaced.

At the end of the day,How to check a non-metallic compensator?Not going through the motions, but turning "examination" into "diagnosis". Each inspection records the appearance status, size data, and leakage, and compares the historical trend. For example, the compression amount in the last quarter was only 40%, and this time it reached 60%, which means that the aging has accelerated-the spare parts replacement plan can be arranged six months in advance.

Don't wait for the smoke to panic. Follow this list, and your non-metallic compensator (whether it is a rectangular non-metallic expansion joint, rubber compensator, or PTFE compensator) will last three or five more years, and it will be perfectly fine.

First, find out what "too long" is all about-common cause investigation

Many people ask as soon as they come up, "What should I do if the metal expansion joint is too long?", but we have to first see whether this "too long" is not calculated correctly by design, or it is forced in during installation. There are three common reasons: First, the thermal elongation of the pipeline is considered large during design and selection, or the cold tightness is not considered at all; Second, there is a deviation between the actual center distance of the on-site pipeline and the drawing, such as support settlement and flange misalignment; Third, the factory length of the expansion joint itself is too large-for example, you ordered a general-purpose corrugated expansion joint, but the supplier delivered it according to the standard length, and did not customize and shorten it. Two days ago, a customer of a power plant took an external pressure single axial expansion joint. The actual installation space was only 300mm, but the one he bought was 400mm long. Do you think this can be installed?

Second, don't hurry to cut, try "adjust the installation position" and "change the bracket" first

The expansion joint is too long, and it is not the only way to cut. In many cases, adjusting the pipe bracket or adding a bias can solve the problem. For example, if your pipe has installation allowance, you can retract the fixing bracket a little, so that the connectors at both ends of the expansion joint extend more into the pipe. Alternatively, if the expansion joint has a tie rod nut (like a large tie rod expansion joint), try loosening the nut to allow the bellows to compress-be careful not to exceed the allowable amount of compression. Don't forget what the expansion joint guide does: it both protects the bellows and limits excessive compression. If you use a double hinge transverse expansion joint, it itself can absorb angular displacement through the hinge, and a slight adjustment of the angle can "eat" part of the length. If it doesn't work, you can add a short section to the pipe to fill up the space.

3. Wrong selection? Then switch to an expansion joint construction-recommended alternative

If the installation and adjustment can't be done, the problem is probably in the selection. At this time, it is necessary to change a more suitable model according to the pipeline displacement, pressure, temperature and other parameters. For example: you originally used a general-purpose corrugated expansion joint, but thought it was too long, so you can replace it with a straight tube pressure balanced expansion joint or a double straight tube bypass pressure balanced expansion joint, which is more compact in structure and has a shorter axial length. If it is a high-temperature steam pipeline, consider the high-temperature axial expansion joint, which has less corrugations, large stiffness and shorter length under the same compensation amount. There is also an extreme practice: instead of the axial expansion joint, the rotary compensator is a sleeve-type structure with a fixed length and is not affected by bellows compensation. Note, however, that rotary compensators are not suitable for high-pressure applications. Here is a reminder that you must check the pipeline thrust before changing the model, otherwise it is easy to pull the bracket.

4. The last way: Cut or return to the factory-but the risks must be clear

Some old masters say, "Saw off a piece of isn't it over?" Don't do this! Each wave of the bellows of the metal expansion joint is calculated according to the design pressure, and cutting will destroy the end structure and stress distribution, which directly leads to the instability or leakage of the bellows. Only a few circumstances are possible: if the manufacturer reserves a cut allowance and you have accurate welding process documentation on hand, you can short-circuit it-for example, large-diameter thick-walled expansion joints sometimes leave a straight edge section on the end tube, allowing you to cut off the excess and re-weld the joint. However, in most cases, it is recommended to contact the manufacturer directly to return to the factory for modification, or change to a customized length. For example, the directly buried (fully buried) expansion joint of this station is made according to the measured length of the construction site after leaving the factory, so there is no problem of being too long at all. Remember: cutting the bellows is equal to scrapping, and cutting the end pipe should also ensure the welding quality. Don't save small money and suffer big losses.

5. How to avoid "too long" from the beginning-3 key points in the design selection stage

Instead of remediating afterwards, it is better to get stuck in the front. First, when calculating the thermal elongation of the pipeline, it should be calculated according to the difference between the actual working temperature and the installation temperature, and don't leave too much margin; Second, preference is given to the type of expansion joint with compact structure-for example, in the pipe gallery with limited space, the double hinge transverse expansion joint or the curved pipe pressure balance expansion joint is much shorter than the single axial type; Third, before ordering, let the manufacturer produce according to the measured size on the spot, or mark the cold tightness on the installation drawing. For example, the corrugated expansion joints for power station industry and metal corrugated expansion joints for cement industry in this station all support non-standard customized length according to working conditions. In addition, don't ignore the non-metallic expansion joint (fabric fiber expansion joint), which occupies little space and is light in weight, and can replace the metal expansion joint under some working conditions.

How to pick the expansion joint manufacturer? A 10-Year Selection Consultant's Guide to Avoiding Pitfalls

Two days ago, I met a customer. As soon as he came up, he threw me a drawing and asked, "How much is this expansion joint?" I said, don't worry. Is your working condition steam pipe or flue gas pipe? What's the temperature? He was stunned for a moment and said, "Oh, it's just ordinary pipes. Can't you use your general-purpose corrugated expansion energy-saving type?"-I can run into this kind of conversation dozens of times a year. If you choose an expansion joint manufacturer, if you only stare at the price, you will probably roll over. Today, I'll talk to you about the pits I've stepped on and the thunder I've seen in these 10 years of selection.

1. Don't just look at price: product line breadth is the first sieve

Many purchases ask, "How much is your expansion joint per meter"-as soon as I hear this, I know that I am either a novice or just want to be cheap. What is the "universal price" of expansion joints? The same caliber,High temperature axial expansion jointAndThe materials and processes of general-purpose corrugated expansion joints are completely different, and the price difference is three or five times too normal.

Start with the thermal expansion and contraction of a pipe

When the steam pipeline was first started, the temperature soared from room temperature to 500 to 600 degrees, and the tens of meters long pipeline could be forcibly stretched by several centimeters. If you keep it from moving, it is common for flanges to collapse and welds to crack. At this time, the expansion joint comes in handy-to put it bluntly, it is the "breathing valve" of the pipeline, specifically designed to "eat" this deformation. Whether it is a metal bellows or a non-metallic fabric layer, the core principle is the same: it absorbs the displacement through its own elastic deformation, so that the pipe should expand and expand, shrink and contract, and the stress is all released on the expansion joint.

So the first question- -What does an expansion joint do?The most fundamental thing is to compensate for thermal displacement and prevent excessive stress in the pipeline system due to temperature changes. But if you think that is what expansion joints are capable of, you would be underestimating it.

In addition to displacement compensation, I also did three things

The high-frequency vibration of the gas turbine exhaust pipe makes your ears buzz when you stand next to it. Once the rubber compensator was installed in the middle, the vibration was directly isolated by more than half, and the noise was also reduced. When the flue gas baffle door and the expansion joint are used together, the air leakage rate of the desulfurization system can be reduced to the lowest-whether the sealing effect is good or not directly related to the energy consumption and emission of the whole system. To be honest, many times the candidate type is not designed to compensate for displacement at all, but is an expansion joint only because of vibration damping or sealing requirements. For example, textile fiber expansion joint is used in dust removal pipeline, mainly because of its vibration absorption capacity and air tightness. Don't underestimate these "side businesses". In actual working conditions, they are more important than the main business.

Metal, non-metal, rubber-three materials and three tempers

High-temperature steam pipeline in power station industry, the first choiceHigh temperature axial expansion jointOrStraight pipe pressure balanced expansion joint。 Why? High temperature resistance, high pressure, corrugated pipe material must be austenitic stainless steel. Cement industry dust removal pipeline, high temperature also contains dust, with metal rectangular expansion joints easy to accumulate dust and get stuck, this time has to be replacedRectangular non-metallic expansion joint-The fabric fiber layer has good flexibility and is not afraid of dust wear. If you encounter corrosive media, such as pickling tanks or chemical lines, PTFE compensators orPTFE-lined hoseThat's the right answer. Choose the wrong material and pierce it in three months. It's really not to scare you. I have seen a chemical plant that installed ordinary metal bellows on dilute sulfuric acid pipelines, and it leaked in less than two months.

Install that little trick

Two days ago, I met a client.Universal corrugated expansion jointThe screws were all disassembled, and as a result, the bellows collapsed directly during the pressure test-this kind of thing is really uncommon. The role of the tie rod is to limit the bellows from being excessively compressed or stretched during transportation and installation, not for you to disassemble and play with. When the expansion joint of the large tie rod is installed, the pre-tension is not adjusted properly, and the bellows directly exceeds the limit under the hot state, and the life is cut in half. The guide tube is installed backwards, and it is more pitty-the medium directly washes the inner wall of the bellows, and it takes less than a few months to wear out cracks. The specific function of the expansion joint guide tube is to guide the flow medium and avoid high-speed airflow or particulate matter directly hitting the bellows. Therefore, be sure to see the direction of the arrow clearly before installation, which is an indication of the flow direction of the medium, not a display.

The life span has to be calculated in detail

The national standard JB/T 12235-2015 for non-metallic expansion joints clearly states that the fabric fiber layer has a fatigue life limit, and it has to be replaced in 3-5 years. If the working condition of metal bellows is stable, it will be fine for 10 years or more. However, if you start and stop frequently or encounter water hammers, it is not unusual for you to crack in two or three years. Don't wait until the pipe bursts before replacing it-regularly check the bellows surface for corrosion points and abnormal displacement, which is stronger than anything else. Sleeve-type pipe expansion joints appear to be simple in structure, but the sealing packing ages quickly and has to be replaced regularly. Generally speaking, the service life of expansion joints is strongly related to four factors: type selection, installation, working conditions and maintenance. Don't expect it once and for all.

So back to the beginning question —What does an expansion joint do?It is more than simply "compensating for displacement". It is also a shock absorber, gasket, noise reducer, and can even save you a lot of equipment repair costs. The premise is that you have to choose the right material, install the right position, and use the right method.

1. First understand the core parameters: what do you think of stiffness, pressure, temperature and compensation?

I have been in this business for 20 years, and I am most afraid that I will fill in "high temperature resistance" directly on the selection list. There are only a few core parameters of bellows expansion joints, but each one hides pits.

stiffness— — Don't be fooled by the word "stiffness". Simply put, it is the ability of bellows to resist deformation. The greater the stiffness, the greater the thrust generated at the same displacement. If you choose an expansion joint with too high stiffness, the pipe bracket and fixing point may directly push through. This site has a special "Stiffness and Calculation Formula of Bellows", which gives the theoretical algorithm. However, when actually selecting the model, it is recommended to ask the manufacturer directly for the measured stiffness value on the sample, which is the real guy.

pressureAndTemperatureIt's a pair of conjoined babies. The pressure level is easy to understand. Which one should I choose between 0.6MPa, 1.0MPa and 1.6MPa? But as soon as the temperature rises, the permissible stress of the material drops. For example, the bearing capacity of 316L stainless steel at 400℃ and room temperature is quite different. Many peers only look at the design temperature, but ignore the "maximum working temperature × duration"-short-term overtemperature may be fine, and long-term operation at the critical point will directly cut the life of bellows in half. So chooseHigh temperature axial expansion jointWhen, not only look at the nominal temperature resistance value, but also confirm whether the number of corrugated layers and wall thickness meet the fatigue life requirements.

Compensation amountIt's a gimmick hit area. Some manufacturers mark "axial compensation ± 50mm", but that is the theoretical value calculated by multiplying the single wave compensation by the wave number. In fact, the pre-stretching amount, safety factor and cold tightness amount have to be deducted. The correct way is to first calculate the thermal elongation of the pipeline, then multiply it by the insurance factor of 1.2~1.5, and finally check it against the "allowable compensation curve" given by the manufacturer. Don't expect an expansion joint to overcome the world. If the compensation amount is too large, consider using itCompound hinge transverse expansion jointOrStraight pipe pressure balanced expansion jointTo share.

2. Don't pat your head when selecting models: high-temperature axial type, general-purpose type, straight pipe pressure balance type, working conditions determine the model

I met a customer two days ago. The temperature of the steam pipeline is 350℃ and the pressure is 1.0MPa. The direction of the pipeline is simple, but it is necessary to go upStraight pipe pressure balanced expansion joint。 Why? Because I heard that "the pressure balance type is good, and there is no blind board force". However, the pressure balance type has complicated structure, high cost and large installation space requirements. For the working condition that there is no strict thrust limit in the straight pipe section, it is purely a knife for killing chickens.

• High temperature axial expansion joint— — It is suitable for straight pipe sections with high temperature and large axial displacement. The temperature resistance can reach above 600℃, but it can only absorb axial displacement and cannot bear lateral or angular displacement. Note that its guide tube is standard to prevent high-temperature media from directly washing the bellows.
• Universal corrugated expansion joint— — It is often called universal type, which can absorb axial, transverse and angular displacement, and is suitable for pipelines with small and medium diameter, low pressure and temperature no more than 300℃. High cost performance, but the fatigue life is relatively short, so don't use high-frequency vibration occasions.
• Straight pipe pressure balanced expansion joint— — It is mainly used in places where the fixed bracket cannot bear the blind plate force, such as the inlet and outlet of steam turbine and the outlet pipeline of pump. It can balance the thrust generated by internal pressure, but it needs to reserve enough space when installing, and the two bellows need to act synchronously, which requires high welding and assembly accuracy.

Apart from that, there areCurved tube pressure balance expansion jointFits at the elbow,Double straight pipe bypass pressure balance typeSolve the problem of large compensation amount. I just want to tell you that there is no standard answer to model selection, only the working conditions determine the model. Don't save trouble, calculate the design parameters clearly, and then flip through the product library of this site. Each model has the corresponding application scenario description.

3. The three most common pits at the installation site: the direction of the guide tube is reversed, the pre-tension is forgotten, and the tie rod nut is randomly adjusted

If you choose the right model, it will still be useless if you mess up the installation. There are countless pits on the scene, and these three are the most typical ones.

The first pit: the direction of the guide tube is reversed.The function of the expansion joint guide tube is to protect the bellows and avoid direct scouring of the medium. However, many masters think that it is a flow direction sign when they look at the arrow-wrong, the direction of the arrow is the flow direction of the medium, and the open end of the guide tube must face the direction of the incoming flow. If it is installed backwards, the guide tube becomes a gas collecting chamber, and the medium forms a vortex in the tube, which intensifies the vibration, and the bellows is worn out in minutes. Regarding this point, there is a diagram in the question and answer of "Specific Function of Expansion Joint Guide Tube" on this site. It is recommended to take a look before installation.

The second pit: forgot to do the pre-stretch.For axial bellows expansion joints, if pre-tensioning (or cold tightening) is not done during installation, the expansion joints may be directly pulled to the limit after the pipeline heats up, and the bellows may be plastically deformed and scrapped. The amount of pre-stretch is generally half the amount of design compensation. For example, the design compensation amount is 80mm, and the pre-stretching amount is 40mm. How to pull? Use the pull rod and the nut to cooperate, don't pull hard, it is easy to hurt the ripples. Note: Remove the limit screw for transportation after pre-tensioning, otherwise the expansion joint will not work. Some expansion joints (such asExternal pressure single axial expansion joint) Comes with pre-stretching device, confirm before installation.

The third pit: the tie rod nut is randomly adjusted.What is the function of the tie rod of the expansion joint? It is clearly written in the question and answer-limit the excessive expansion and contraction of the bellows and prevent instability. However, some on-site masters think that tightening the nut means fixing, and loosening it means releasing. As a result, the tie rod is adjusted to a dead limit, and the expansion joint completely loses its compensation ability. The correct way is to adjust the nut to the design position according to the drawing before installation (usually with a gap), and then fine-tune it according to the actual needs after installing the pipe. EspeciallyLarge tie rod expansion jointThe tie rod is not a load-bearing part, but a limiting part. Don't use it as a hard support. There are also expansion joints with screws, asking "Do the screws need to be removed"? The answer is: the transport screw must be disassembled, and the tie rod screw remains but the position is adjusted.

4. Industry application comparison: how to set up corrugated expansion joints for power stations, metal corrugated expansion joints for cement industry and desulfurization flue gas baffle doors

Different industries, working conditions vary greatly, and the emphasis of type selection and installation is completely different.

Power station industry: The main steam pipeline, reheating pipeline and water supply pipeline are all large-diameter, high-pressure and high-temperature expansion joints, such asCorrugated expansion joint for power station industryAndDouble hinge expansion joint for air-cooled island vacuum pipeline。 The calculation of pipeline thrust in power stations is extremely strict, and compound hinges or pressure balance types are often used to release the thrust on steam turbines and boilers. Special attention should be paid to when installing: preheating before welding, and slow cooling after welding to prevent stress cracking in the heat-affected zone. Moreover, power station pipelines often have vertical sections, so guide brackets should be set to prevent the expansion joint from twisting.

Cement industry: The high-temperature fan outlet, kiln tail smoke chamber and decomposition furnace inlet and outlet of cement production line, the temperature is 350~500℃ all the year round, with large dust content and serious medium wear. You can't use ordinary stainless steel bellows at this time, you have toMetal Corrugated Expansion Joints in Cement IndustryIn particular, attention should be paid to the lining wear-resistant layer and multi-layer corrugated design. In addition, such occasions are usually associated withRectangular non-metallic expansion jointOrNon-metallic expansion joint (fabric fiber expansion joint)Used on flue gas pipelines, non-metallic materials are corrosion resistant and have high fault tolerance.

Desulfurization flue gas system: The flue gas after wet desulfurization has low temperature but acid corrosion, so it must be usedDesulfurization flue gas baffle doorMatching expansion joint. The most common thing here isDouble-sealed single-axis circular baffle doorAndRound Flap Door (Double Seal), cooperate withrubber compensatorOrPTFE-lined hoseTo isolate corrosive media. Note: The rubber compensator is not resistant to high temperatures and can only be used for clean flue with smoke temperature below 80℃; If the flue gas temperature fluctuates greatly, it is recommended to usePTFE compensator。 The length of the connection between the baffle door and the expansion joint should be sufficient, otherwise the expansion joint will be squeezed and deformed after closing.

5. There is a way to maintain: What is the impact on the service life of the expansion joint? Replacement cycle of rubber compensator and metal hose

Expansion joints are not permanent pieces, but they vary greatly in life. Main factors affecting longevity-by importance:

• Large temperature cycle-frequent start-stop process harms the bellows the most, because the number of thermal stress cycles directly determines the fatigue life.
• Medium corrosion-the chloride ion content exceeds 100ppm, 316L can't bear it, must be replacedPTFE-lined hoseOr higher grade stainless steel.
• Installation error-the initial stress caused by misedging and forced matching of the pipeline is equal to overdrafting the life every day.
• Vibration-Pipe vibration will accelerate the stress concentration at the crest of the bellows, which is prone to cracking.

thatrubber compensatorHow often do you change? Depending on working conditions. The rubber compensator used for desulfurization flue is subject to acid-alkali corrosion and ultraviolet aging, and generally needs to be inspected in 2~3 years. If you find that the rubber surface is hardened, cracked, or even delaminated, replace it immediately. WhileMetal hose(includingSpecial hose for vacuum) The replacement cycle is slightly longer, and it can be used for 5~8 years when there is no obvious corrosion, but the premise is to regularly check the outer surface of the bellows for pitting or wear marks.

Every overhaul cycle, open the insulation layer and visually check the bellows for pits, cracks and scratches; Touch the guide tube with your hand to see if it is loose; Whether the loosening spacer for the tie rod nut is still there. Don't wait until a leak is replaced, by which time you may have damaged nearby brackets and equipment.

To put it bluntly, the bellows expansion joint is worth ten years if it is selected correctly, but it will be scrapped if it is installed wrongly for ten days. I hope these experiences can help you step on fewer pits at the scene.