Specialized in manufacturing compensators, expansion joints, baffle doors

Metal expansion joint desoldering? Don't hurry to scold the manufacturer, the problem may lie in this

Two days ago, I met a customer who said that the metal expansion joint weld of their pipeline was cracked, and asked me if the quality was not good. Alas, who is not in a hurry when it comes to such things-media leakage, production line shutdown, or safety accidents. But let's say, don't rush to throw the blame on the manufacturer. For the problem of desoldering, we must first look at where the welding is located. Is it the bellows and end pipe connection? Or a deflector weld? Or is it a tie rod mount? The causes of desoldering in different positions vary a hundred and eighty thousand miles.

The cracking of the circumferential weld between the bellows and the end pipe is most likely due to fatigue or stress concentration. If the weld of the guide tube is cracked, it is mostly because the guide tube is worn through by the medium or the guide tube is installed backwards, causing the airflow to directly scour the weld. Tie rod bearing desoldering? You have to check whether the tie rod nut is loosened during installation, and whether the limit is regarded as a fixed support. And guess what? Many so-called "quality accidents" were checked over and over again. Either the installation team was fooling around, or the selection didn't match the working conditions at all.

The three most common pits for desoldering

First, fatigue.The pipeline system expands and contracts thermally every day, and the expansion joint expands and contracts repeatedly. Once the stress concentration at the weld exceeds the allowable value, cracks will slowly grow out. Especially the large-diameter thick-walled expansion joint or high-temperature axial expansion joint, the more extreme the working condition, the more sensitive the fatigue life. For example, the temperature of high-temperature flue gas pipelines in the cement industry often fluctuates above 400℃. Every time the bellows expands and contracts, the welds accumulate damage.

Second, corrosion.When there are chloride ions and sulfide in the medium, the weld seam will be corroded preferentially, and the strength will drop linearly. The expansion joint behind the desulfurization flue gas baffle door has a bad corrosion environment. If the right material is not selected or the corrosion resistance treatment is not done, the weld will become slag in less than half a year.

Third, the installation error.When leaving the factory, the tie rod nut was not loosened, the guide tube was installed backwards, and the cold drawing amount of the pipeline was not enough... These operations caused additional stress to be fully pressed on the weld. Many customers complained that "it took three months to desolder". As a result, when they went to the scene, they found that the direction of the guide tube arrow pointed to the opposite direction of the medium flow, and the airflow directly hit the bellows. Tsk, is this pot manufacturer wronged?

What about that?

Let's see the working conditions first. If it is a pipeline at normal temperature and low pressure, such as a general-purpose corrugated expansion joint, the cracking of the weld joint is probably a problem of the welding quality itself-the current is excessive, the welding electrode is wrong, and the groove is not handled properly. You have to re-weld if you should cut it off and re-weld it. Don't feel distressed. However, if it is a high-temperature steam pipeline or a high-temperature flue gas pipeline in the cement industry, desoldering is often a wrong selection. At this time, we have to consider changing the high-temperature axial expansion joint or the external pressure single axial expansion joint, so that the bellows can avoid the high-temperature area. Another situation: the displacement of the pipeline is too large, and the general-purpose type can't bear it at all, so it is necessary to use the double hinge transverse expansion joint or the straight pipe pressure balance expansion joint to share the stress.

On-site emergency treatment is also particular. Small cracks can be repaired in non-critical parts, but they must be welded with the same material electrode, preheated and controlled cooling speed. If the bellows itself is cracked, don't repair welding-the wall thickness of the bellows is thin, and it will burn through as soon as it is repaired, so replace it directly. In addition, it should be noted that before repair welding, check whether the guide tube is in good condition. If the guide tube is also worn out, the medium will directly wash the inner wall of the bellows, and desoldering is only a prelude. When replacing, it is best to check the adjustment status of the expansion joint tie rod nut simultaneously to ensure that the pre-tension or pre-compression meets the design requirements. As for how to adjust the tie rod nut? After screwing the nut to the limit position, reverse back half a turn to one turn, so that the expansion energy saving can expand and contract freely. Look at the design drawings for specific values, don't screw them blindly by hand feel.

Prevention is really worry-free

The selection stage is not cheap. When providing information to the design institute, write clearly the temperature, pressure, displacement and corrosive medium. For example, the expansion joint behind the flue gas baffle door has a high sulfur content in the medium, so corrosion-resistant alloy or PTFE-lined scheme must be used. In the installation stage, be sure to look at the direction of the arrow on the expansion joint (flow direction mark), and one end of the guide tube faces the direction of the medium. During the operation stage, check the appearance of the weld regularly, tap and listen to the sound, and do penetration testing if conditions permit. Don't forget, the life of the expansion joint is directly tied to maintenance-you let it run over the limit, and it will strike sooner or later.

In the final analysis, 80% of the desoldering of metal expansion joints are not deliberately cut corners by manufacturers. Find the root cause, prescribe the right medicine, change the type, repair the welding, don't curse your mother as soon as you come up. Pipeline safety depends on the cooperation of three rings of selection, installation and maintenance, and one less ring will lead to moths.

1. 非金属补偿器用在哪儿？别用错了地方。

非金属补偿器（也叫非金属膨胀节/织物纤维膨胀节）主要拿来对付烟气、热风、粉尘这类低压高温管道系统。说白了，金属膨胀节扛不住高温腐蚀或者大位移的地方，就该它上场。比如电站的脱硫烟气管道、水泥行业的窑尾废气管道、钢铁厂的高炉煤气管道，甚至垃圾焚烧厂的烟气净化系统——这些场合温度动不动五六百度，有的瞬时峰值能冲到1000℃以上，金属件早软了。

跟金属补偿器不同，它靠纤维织物和橡胶复合层来吸收位移，本身不产生推力，这一点在支架设计上能省不少事。但你要非把它装在高压蒸汽管道上？那就不对了——压力超过0.1MPa就得小心选型，别拿它当高压件用。我们站里有个客户曾经想把矩型非金属膨胀节用在2MPa的压缩空气管上，结果还没运行呢，织物层就鼓包了。

2. 安装前先搞清楚这4个参数，否则白干。

第一个是位移量——你得算清楚管道热胀冷缩到底偏移多少毫米，轴向、横向、角向分开算。很多现场图省事，张口就说“来个200mm的”，结果实际位移只有30mm，小马拉大车，织物褶皱老化快。第二个是温度——介质最高温度和瞬时峰值温度直接决定选哪一层织物：硅胶布耐温200℃左右，氟胶布能到300℃，再高就得陶瓷纤维了。

第三个是介质成分。有强酸强碱？那得加聚四氟乙烯内衬，也就是咱们站上的“橡胶四氟补偿器”或者“聚四氟乙烯补偿器”。第四个是安装空间——方形管道用矩型非金属膨胀节，圆形管道用圆形，别弄混。前两天有个客户拿着圆形的往矩形风道上焊，结果密封不严，返工半个月。你说冤不冤？

3. 安装步骤和那个最容易翻车的细节。

吊装到位→调整螺栓预拉伸量→焊接或法兰连接→拆除运输螺杆。但翻车最狠的是——运输螺杆什么时候拆？很多人一装好就拆，结果管道还没热，补偿器就被拉坏了。正确做法：等管道安装完毕、支架固定好、试运行前再拆。我们站的FAQ里专门提过“膨胀节的螺杆需要拆吗”，说的就是这茬。

另外，导流筒的方向必须顺着介质流向，箭头方向别焊反了。你猜怎么着？有家水泥厂把导流筒装反了，高温气流直接冲刷织物层，三天就穿孔。咱们站FAQ里也详细讲过“膨胀节的箭头方向”就是干这个用的。

4. 日常使用中，三个最容易忽略的坑。

坑一：让补偿器承重。非金属补偿器只吸收位移，不承重，管道重量全靠支架。哪怕一个弯头也要单独支架，别让它吊着。有的现场图省事，把阀门直接挂在补偿器上，不出一个月法兰就漏了。

坑二：忽视保温。外保温层不光隔热，还能防止冷凝水腐蚀织物层。但很多人觉得“反正能耐高温”就不包，结果外部结露，水渗进织物里，加速老化。冬天尤其明显。

坑三：小位移用大补偿器。有些人为了“保险”选超大规格，反而导致织物在低位移下褶皱、老化加速。按照JB/T 12235-2015标准，补偿器的工作位移最好控制在额定位移的60%-80%之间。你说用200mm的补偿器去吸收20mm的位移，那不是糟蹋东西嘛。

5. 什么时候该换？别等到漏了再拆。

非金属补偿器的寿命通常3-5年，但取决于工况。如果你发现织物层表面出现龟裂、硬化、分层，或者法兰螺栓松动后怎么也拧不紧（说明密封层已经塌了），那就得赶紧换。再一个信号——管道振动突然变大，或者周围有异响，可能是内部导流筒脱落。平时每季度检查一次外观，重点关注焊缝和织物搭接处。

想省事的话，橡胶补偿器比织物补偿器便宜，但耐温只有100℃左右，别搞混。碰到高温烟气还得用非金属膨胀节(织物纤维膨胀节)或者矩型非金属膨胀节。说到底，选型对了，安装对了，保养跟上，一个补偿器用个五年不是问题。

What is radial force? Why do so many people fall on this

Anyone who designs pipelines knows that the biggest function of metal expansion joints is to absorb heat displacement. However, when the radial force was mentioned, many people began to be confused. Radial force, to put it bluntly, is the force that pushes the bellows perpendicular to the axis of the pipe, from the center outward or from the outside inward. Wrong direction, light bulge, worse bracket collapse, pipeline twist. Two days ago, I met a customer. A DN600 steam pipe was equipped with a universal corrugated expansion joint. As a result, the radial force was not calculated accurately. After three days of production, the corrugated pipe bulged like a toad's belly. Alas, this kind of thing is not rare.

Radial forces under internal pressure: Outward expansion is mainstream, but not so simple

As soon as the pressure inside the pipe comes up, the bellows expands outward like a balloon-this is the most intuitive direction of radial force, pointing from the central axis to the outer wall. But don't think it's just evenly outward. withUniversal corrugated expansion jointFor example, the radial force generated by internal pressure will make the wave peak expand outward and the wave trough contract inward. The magnitude of this force is directly related to the pressure and wave diameter. If the medium is high temperature and high pressure steam, the radial force has to be doubled instantly. What's more troublesome is that this force will be transmitted to the whole pipeline system, and if the constraint is not good, it can push the fixing bracket askew.

Don't ignore end effects

Where the ends of the bellows are close to the end pipe, the radial force distribution will change abruptly. Stress is concentrated there, and the ripples are more likely to crack. So a lotHigh temperature axial expansion jointThickened walls or reinforcing rings may be provided at the ends in order to hold the non-uniform radial forces of this piece.

Radial force reversal under displacement condition: axial compression, transverse tension, direction change accordingly

Internal pressure is only the basic working condition, and what really makes the radial force "discolor" is displacement. When the pipe is heated and elongated, and the expansion joint is axially compressed, the relative positions of the peaks and valleys of the bellows change, and the direction of the radial force will be partially reversed-the place that originally wanted to be pushed out may be retracted inward at this time. Conversely, if it is a lateral displacement (such as a pipe route turning), the radial force will become a complicated state of "pulling and pressing at the same time". At this time, useCompound hinge transverse expansion jointOrLarge tie rod expansion jointCan effectively restrain and avoid the radial force runaway.

I've seen a case in the cement industry, usingMetal Corrugated Expansion Joints in Cement IndustryOriginally, the axial displacement was handled well, but the radial force reversal was not considered after the lateral displacement was added, and the spacing between the guide brackets was too large, so the bellows was directly twisted into a twist. Tsk, it's more expensive to fix than to buy a new one.

Differences in Radial Force of Different Types of Expansion Joints: From Universal Type to Pressure Balance Type

Different structural designs, the performance of radial force is very different.

• Universal corrugated expansion joint: The radial force caused by internal pressure is the largest. If there is no guide tube, the bellows will easily become unstable under high pressure.
• Straight pipe pressure balanced expansion jointAndCurved tube pressure balance expansion joint: Most of the internal pressure thrust is offset by balancing the bellows, and the radial force mainly comes from media flow disturbance and installation deviation, which is relatively easy to control.
• Compound hinge transverse expansion joint: The radial force is concentrated on the hinge structure, and the bellows itself is more stressed, but special attention should be paid to the fatigue life of the hinge.
• External pressure single axial expansion joint: On the contrary, its bellows is compressed on the outside, and the radial force generated by the internal pressure is squeezed inward, in the entire reverse direction. Don't get confused when designing.

You see, it is also called an expansion joint, and the direction of radial force varies widely. When you don't see clearly when you select the model, you have to cry at the scene as soon as you sign the drawings.

Common consequences of misdesigning radial forces: bulging, twisting, stent collapse

The radial force is not counted correctly, how serious are the consequences? Tell me a few real things:

• bulge: The internal pressure radial force is too large, the bellows peak excessively expands outward, and the material forms permanent bulge after yielding. Common inLarge diameter thick wall expansion jointAlthough the wall thickness is large, the stress is concentrated in the zone of abrupt curvature change.
• Twisted: The direction of the radial force is inconsistent during lateral displacement, causing the bellows to twist like twisting a towel. Generally occurs in the middle of long pipelines, when the spacing between guide brackets exceeds the standard.
• Stent collapsed: The radial force is transmitted to the fixed bracket through the end tube, and if the bracket is not designed according to the thrust, it will tear the base directly. There was a desulfurization flue project last year, usingDesulfurization flue gas baffle doorAndNon-metallic expansion jointCombination, just because the radial force is not counted, the fillet weld of the steel support is broken.

These problems can actually be avoided by preliminary calculation. The point is, you have to know exactly where the radial force is pushing.

How to judge the direction of radial force during installation? Look at arrows, calculate thrust, set guidance

Don't have time to do finite elements for on-site installation? There are shortcuts, too.

First, look at the arrows.Products in the station (such asUniversal corrugated expansion joint) Before leaving the factory, arrows are basically made, and the direction of the arrows is the flow direction of the medium, which also corresponds to the main direction of the radial force after installation-the flow direction side is the peak expansion side, and the reverse side is the trough contraction side. Don't act backwards.

Second, count thrust.The internal pressure thrust formula is not complicated: F = p × A (A is the effective area of the bellows). However, the radial force has to be multiplied by a coefficient, which is related to the shape and height of the wave. In the stationStiffness and Calculation Formula of BellowsThe detailed algorithm is listed in the question and answer, so just apply it directly.

Third, set the guidance.Whether the radial force can be controlled or not, the guide bracket is the key. normalUniversal expansion jointThe first set of guide brackets is required to be Direct buried (fully buried) type expansion jointIt is another set of calculation logic to consider the influence of soil lateral constraint on radial force.

How many hundreds can a piece of cloth carry? Talk about the underlying logic of the temperature range of non-metallic expansion joints

When many people come into contact with non-metallic expansion joints for the first time, they will think that this thing is just a piece of "cloth"? If you can hold a hundred or two hundred degrees, it will top the sky. But the reality is that in places such as cement kiln tail and boiler flue, it has to work in flue gas at 300 to 400 degrees Celsius or even higher. Isn't it a little counter-intuitive?
In fact, the truth is very simple: non-metallic expansion joints do not rely on a single layer of fabric to carry the temperature at all. Its temperature capability depends on the synergy of the entire composite structure-fabric, insulation, sealing layer, each with its own division of labor. But the outermost layer of cloth determines "whether you can carry it", and the hidden insulation layer inside determines "how long you can carry it". If you don't understand this logic, the selection is blind.

Silicone cloth, fluorine tape, polytetrafluoroethylene-where is the temperature ceiling of different fabric layers

Let's go straight to the hard goods. There are only a few kinds of fabrics most commonly used for non-metallic expansion joints, and the upper temperature limit is basically the industry consensus:

• Silicone cloth: The continuous working temperature is about 200~250 DEG C. The advantages are good flexibility and aging resistance, but once it exceeds 250 ℃, the silicone coating begins to decompose and the fabric becomes brittle. Therefore, silicone cloth is suitable for compensators from room temperature to medium temperature, such as air conditioning air duct and drying equipment.
• Fluorine tape: Can carry it to the beginning of 300℃. The high temperature resistance of fluororubber is stronger than that of silica gel, and it is also resistant to oil, acid and alkali. It is often used for the front flue of the desulfurization tower, but it won't work further up.
• Polytetrafluoroethylene (PTFE) film or coated cloth: This is the "carrying handle" in non-metallic fabrics at present. The long-term service temperature of pure PTFE can reach about 260℃, but the glass fiber cloth + PTFE composite layer after special impregnation treatment can reach 350℃ or even higher in a short time. Note, it is short-term. When continuous operation exceeds 300℃, PTFE will slowly soften and creep, resulting in leakage.

Many people look at this table and run to choose PTFE cloth, thinking that everything will be fine. Hey, don't worry-the fabric is only the first line of defense, and the real trick is in it.

Don't just look at the fabric: insulation and sealing structures are the real protagonists of high-temperature conditions

Two days ago, I met a customer, saying that his non-metallic expansion joint at the tail of the cement kiln leaked after less than half a year. On disassembly, the fabric layer is intact, but the insulation layer in the middle — ceramic fiber felt — has been sintered to powder by high temperatures. This is the typical "strong outside but dry inside".
The function of the insulation layer is to block the heat flow inside through porous materials (ceramic fibers, aluminum silicate wool, glass fiber felt). If the insulation layer is not thick and dense enough, the heat penetrates directly into the inner surface of the fabric, and the fabric soon becomes unbearable. A standard non-metallic expansion joint such as oursNon-metallic expansion joint (fabric fiber expansion joint)It is usually designed in 3~5 layers: an outer layer of fluorine tape or PTFE cloth, 2~3 layers of heat insulation felt in the middle, and an inner layer of corrosion-resistant sealing film (such as F46 film).
More critical is the sealing structure. At high temperature, the pressing force between the metal flange and the cloth surface will be loosened due to thermal expansion, so it is generally necessary to match stainless steel pressing strips and high-temperature sealing gaskets. Don't underestimate this. The root cause of many leaks is the failure of the seal at the flange, not the broken fabric itself.

Temperature and pressure are husband and wife, who has the final say when fighting? Synergistic Relationship Must Be Considered in Model Selection

When the temperature goes up, the pressure goes down. These two parameters are like a couple fighting-one is always pressing the other. For example, the same PTFE fabric compensator can withstand 0.3MPa at 200℃, and it may not even be able to withstand 0.1MPa at 300℃. Why? Because the strength of the fabric decreases with the increase of temperature, and at the same time the aging rate of the seal ring accelerates.
Therefore, when selecting the model, we must get the "temperature-pressure" combination of working conditions, instead of simply asking "how many degrees can this expansion joint withstand". For example:rubber compensatorGenerally used for normal temperature and low pressure (0.1~0.2MPa), andRectangular non-metallic expansion joint350 ℃ and slightly positive pressure are common in the boiler flue. If you throw the rubber compensator into the 250℃ flue, it will be wasted in less than a month. Conversely, if high-temperature resistant non-metallic expansion joints are used on high-pressure pipes, the flange connections will also be pushed open.

Cement kiln tail, boiler flue, desulfurization tower-three real cases teach you to calculate the applicable temperature

It's boring to talk about theory. Let's look at the case directly:

• Cement kiln tail: The typical temperature is 350~400 ℃, and the flue gas contains dust and alkaline substances. The selection scheme isNon-metallic expansion joint (fabric fiber expansion joint), PTFE impregnated glass fiber cloth for the fabric, three layers of ceramic fiber felt in the middle (20mm each), and an inner F46 film for corrosion protection. The sealing structure adopts stainless steel corrugated press strip + graphite gasket. The actual operating temperature is 380℃, the pressure is-3kPa, and the life can reach more than 2 years.
• Boiler flue: The temperature is generally 150~250℃, but an instantaneous peak of 300℃ may occur when starting and stopping. At this time, silicone cloth or fluorine tape is enough, and the price is also cheap. However, it should be noted that the boiler flue gas has a large moisture content, so waterproof fabrics should be selected, such asRubber PTFE compensator(lined with PTFE) can be solved well.
• Desulfurization tower import and export: The temperature is 80-120 DEG C, but the medium contains dilute sulfuric acid, which is highly corrosive. Conventional non-metallic expansion joint fabrics are prone to corrosion, so it is recommendedPTFE compensatorOr rubber compensator lined with PTFE, although the temperature is low, anti-corrosion is the first priority.

Do you see the doorway? Each working condition should be calculated separately: first set the temperature section, then look at the medium and pressure, and finally combine the number of layers.

Three-step self-examination method: You can also judge by yourself that non-metallic expansion energy saving can't be used in your working condition

Well, after talking about so many dry goods earlier, finally give me a grounded self-examination method, so as to save you from being fooled by sales:

1. Step 1: Find out the working condition parameters-Maximum continuous operating temperature, instantaneous peak temperature, medium (whether containing acid, alkali, particles), working pressure (positive or negative pressure?). These data are indispensable.
2. Step 2: Check fabric and insulation— — Take a product sample and ask what material the outer cloth is made of (silica gel? Fluorine glue? PTFE?), which kinds of felt are used for the insulation layer, and how thick each layer is. If the total thickness is less than 50mm, it basically can't bear long-term operation above 250℃.
3. Step 3: Look at the seal and connection structure-Is the flange surface flat or with stops? Stainless steel 304 or 316 for beading? Is the gasket asbestos rubber or expanded graphite? If the seal is not good, no matter how good the fabric is, it will be for nothing.

After these three steps, he felt confident in his heart. Finally, the national standard for non-metallic expansion joints is JB/T 12235-2015, which can be used as a reference when selecting. However, the practical application depends on practical experience. After all, the standard is only the lower limit.

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.