Specialized in manufacturing compensators, expansion joints, baffle doors

1. Why can high-temperature resistant non-metallic compensators withstand high temperatures? Materials are key

To be honest, when many people come into contact with this thing for the first time, their first reaction is: Can something made of fabric and rubber hold hundreds of degrees of high temperature? Don't worry, let's look at the materials first. High-temperature resistant non-metallic compensators usually adopt multi-layer composite structure, the core of which is the flexible fabric layer in the middle, such as silicone rubber coated glass fiber cloth, polytetrafluoroethylene film and ceramic fiber felt. Silicone rubber itself can withstand temperature to about 250°C, but with the addition of glass fiber and ceramic fiber, the working temperature is directly raised to 600°C or even above 1000°C. And guess what?"Non-metallic expansion joint (fabric fiber expansion joint)" mentioned in the product information of this siteThe more layers, the stronger the heat insulation and temperature resistance.

There is also a layer that is easily overlooked-the internal deflector. Many non-metallic compensators will be equipped with metal guide tubes, which not only guide the airflow to reduce erosion, but also block the high-temperature smoke from licking directly to the fabric surface. This thing is kind of like armor, minimizing the damage from heat radiation. So you see, the confidence of high temperature resistance is not blown out, but layered materials.

2. Temperature upper limit and pressure level: Don't just listen to propaganda, look at national standards and actual measurements

Some manufacturers in the market say that their products can carry 1200°C, but when you ask about the pressure level, they hesitate. According to the National Standard for Non-metallic Expansion Joints JB/T 12235-2015, the upper limit of working temperature of non-metallic compensator is related to the medium, pressure and displacement, not just by looking at the numbers. How do the measured data come from? Take a practical case: The outlet pipeline of the rotary kiln in a cement plant isRectangular non-metallic expansion jointWith a medium temperature of 850°C and a pressure of ±3kPa, the fabric loop belt was changed once after more than two years of continuous operation.

In terms of pressure, non-metallic compensators are naturally inferior to metal because of their flexible structure, so they are generally used in low-pressure flue duct systems (within 0.1MPa). But it has a unique skill: it can absorb multi-dimensional displacements (axial, radial and angular), and it has minimal thrust on the pipe. So don't use it as a pressure vessel, it's more like an elastic soft joint.

What about the performance of high temperature resistant non-metallic compensator? Bottom line: look at the working condition match. For scenarios below 600°C, low pressure, and large displacements, it is much more reliable than a metal compensator.

Third, just with the front of the metal compensator: who is more cost-effective and who is more durable?

Two days ago, I met a customer who insisted on using it on a 300°C flue.High temperature axial expansion jointI asked him why he didn't use non-metallic ones. He said he thought the metal was durable. As a result, the metal bellows should not only choose heat-resistant alloy steel (the cost doubles), but also consider the corrosion problem, and there are many welding points, which makes maintenance troublesome.

Under the same caliber, the price is generally only 1/3 to 1/2 of that of metal. More importantly, its installation accuracy requirements are low, and the on-site cutting adjustment is not distressed. Moreover, it is convenient to repair-if the fabric ring belt is broken, it can be replaced directly, unlike metal bellows that have to dismantle a bunch of flanges. What about longevity? Under normal working conditions (the temperature is lower than the design value, and the medium has no corrosion), the fabric layer can be used for 5-8 years, which is much longer than the fatigue life of metal bellows at high temperature.

But it's not without its flaws. Non-metallic compensators are afraid of sharp hard objects scratching, afraid of direct burning by open flame. So it fits flue gas, hot air, dust ducts, not steam ducts (unless specifically designed). When selecting a model,Product Center of this siteCompare the parameters well, and don't mess with the Mandarin Duck Spectrum.

4. Selection and rollover site: size, displacement and installation direction must not be missing

Let me tell you the truth. In order to save trouble, a steel mill bought a non-metallic compensator and installed it directly. As a result, the fabric burst after one week's operation. Why? The amount of displacement is not counted correctly! The thermal expansion length of the pipe is calculated to be 50mm, and the compensator they bought can only absorb 30mm, so it's weird that it doesn't burst.

Diameter (DN size), compensated displacement (axial/transverse/angular), operating temperature。 If one is missing, it can overturn. Such asRectangular non-metallic expansion jointIt is used on rectangular flue. When installing, it should be noted that the direction of the guide tube must be consistent with the flow direction of the medium, otherwise the guide tube will be washed askew and the fabric will be directly exposed to the high-temperature airflow. There is also the installation direction: non-metallic compensators usually can't withstand pressure thrust, so the tie rod bolt should be adjusted to the appropriate tension (refer to the FAQ "How to adjust the tie rod nut of the expansion joint"), and it can't be screwed to death or too loose.

In addition, where to choose the location is also very particular. Try to avoid installing it behind the elbow or in the turbulent zone downstream of the valve, otherwise the airflow impact will shorten the fabric life. If you can't avoid it, then install an internal anti-scour board (some manufacturers design it as standard, and some have to be customized). You bought the compensator with or without a deflector? This is inSpecific Function of Expansion Joint Guide TubeThere is a detailed explanation in the Q&A, so it is recommended to take a closer look before placing an order.

5. How many years can the life span last? Practical recommendations for maintenance and replacement

The lifetime of non-metallic compensators is greatly affected by temperature fluctuations. If the medium temperature is stable, the aging of the fabric layer is slow, and it is normal to use it for 6 years. However, if it starts and stops frequently and the temperature rises and falls sharply, it may have to be changed in 3 years. Simple maintenance: check the fabric surface every six months for any cracks, aging and brittleness, and any leakage traces. By the way, use a flashlight to see if the internal guide tube is deformed or fallen off.

Once you find bulging or partial ablation of the fabric, don't hesitate to change it quickly. Note when changing: Before dismantling the old ring belt, first confirm that the pipeline has cooled down and relieved pressure, safety first. When installing the new ring belt, the strip bolts should be symmetrically tightened to prevent uneven force. If you can't handle it yourself, go directly to the manufacturer for after-sales service. Many non-metallic compensator suppliers provide on-site replacement services.

After all, what is the performance of high-temperature resistant non-metallic compensators? Depends if you know how to use it. Temperature resistance of materials is a hard index, while installation and maintenance is a soft effort. Get these points thoroughly, and it is definitely the "utility pie" in your plumbing system.

Let's talk about the conclusion first: Is the non-metallic compensator resistant to high temperatures?

Resistant, and can carry better than metal compensators under some working conditions. But there is a premise-you have to choose the right material. When many people hear the word "non-metal", the first reaction in their minds is "plastic things are soft when exposed to heat". Tsk, that impression has to be changed. Non-metallic compensators (also called fabric fiber expansion joints and non-metallic expansion joints) are not simple plastic at all. Its main body is composite materials: multi-layers of fabric fiber cloth, rubber, fluoroplastics and insulation cotton are superimposed together, and each layer performs its own duties. Therefore, whether it is resistant to high temperatures or not depends entirely on which "formula" you pick.

The secret of high temperature resistance is hidden in materials: how many degrees can it carry from silica gel to tetrafluorine?

Let's take apart several kinds of fabrics commonly used in nonmetallic compensators, and the upper temperature limit is clear at a glance:

• Silicone cloth/fluororubber cloth: The continuous working temperature is 200℃ ~250℃, and it can reach 300℃ in a short time. Suitable for hot air duct, low pressure steam.
• Polytetrafluoroethylene (PTFE/Tefluoro): Temperature resistance range-200℃ ~ +250℃, but above this temperature, PTFE will decompose to produce toxic gases. This site'sPTFE compensatorAndPTFE-lined hoseIs a typical representative, suitable for corrosive media and low temperature occasions.
• Ceramic fiber cloth (aluminum silicate fiber): This thing is the real main force of high temperature resistance, and the long-term use temperature can reach more than 1000℃. With stainless steel wire reinforcement, it is commonly used in flue gas pipeline and boiler exhaust system. stationaryNon-metallic expansion joint (fabric fiber expansion joint)Use this kind of material in large quantities.
• Glass fiber cloth + silicone rubber coating: The common temperature resistance range is 250℃ ~400℃, taking into account both flexibility and sealing.

So you see, there are corresponding products for the temperature resistance span of non-metallic compensators from 150℃ to 1200℃, and the key lies in the thickness of the middle insulation layer and the number of fabric layers. Listed in the stationHigh temperature axial expansion jointIt belongs to the metal category, but if you need super-large displacement and high temperature, non-metals are more flexible.

The scenario decides the choice: Which kind to use for flue gas pipes? Which kind of high-temperature steam should I use?

Two days ago, I met a customer who was doing desulfurization project. When I came up, I asked, "Is the non-metallic compensator resistant to high temperatures? The flue gas temperature is 350℃". I said no problem, but it has to be equipped with ceramic fiber lining + stainless steel wire mesh reinforcement layer, and the outer layer is protected against acid corrosion with fluororubber cloth. This operating condition is selectedRectangular non-metallic expansion jointThe most suitable, can absorb three-dimensional displacement, flange installation also saves space.
Conversely, if it is high temperature steam (such as the main steam pipe of a power station, the temperature is 540℃), guess what?Non-metallic expansion joints N/A。 High-temperature and high-pressure steam has strong permeability, and the non-metallic layer is easy to bulge and delaminate. At this time, honestlyCorrugated expansion joint for power station industryOrHigh temperature axial type expansion joint. Non-metallic compensator is most used for low-pressure saturated steam (≤150℃) on steam pipeline. If it exceeds this number, metal compensator is the correct solution.

Compared with metal compensators, what is the advantage of non-metal high temperature resistance?

The upper limit of temperature resistance of metal compensators (such as stainless steel bellows) is very high. Ordinary 304 stainless steel can carry 600℃, and Inconel alloy can even reach 900℃. But nonmetallic compensators have a unique skill- -Thermal shock resistance。 Metals are prone to fatigue cracks under quenching and sudden heating, while non-metals are more solid because of their soft material and multilayer structure that can buffer thermal stress. For example, the temperature of the flue gas pipeline of the waste incinerator instantly drops from 800℃ to 200℃, and the metal expansion joint may crack in two or three years.Non-metallic expansion joint (fabric fiber expansion joint)It's normal to use it for five or six years. In addition, the non-metal compensator also has its own vibration and noise reduction function, and the metal compensator has to be added with an additional damper. But what about the cost? Non-metals have weak pressure bearing capacity, so they are generally only used at low pressure (≤0.1MPa), and they still have to be used when high pressure is neededUniversal corrugated expansion jointOrStraight pipe pressure balanced expansion joint。

Select and avoid pits: Don't just look at temperature, but also at pits such as pressure, medium and life

Many people think that "it's enough to withstand temperature", but it leaks after three months of installation. Why? The pressure is over the limit! The pressure rating of non-metallic compensators usually does not exceed 0.1MPa, and if there is a positive or negative pressure fluctuation inside the pipe, the flange sealing surface can easily be blown open. Besides, the flue gas containing acidic gas must be lined with PTFE or fluororubber, otherwise the fiber cloth will be corroded through. From our stationRubber PTFE compensatorIt is to solve this corrosion + medium temperature working condition.
There is also the problem of life-the fabric layer of non-metallic compensator is a consumable, and the normal life is 3~5 years, while the metal compensator can do it for more than 10 years. Therefore, if it is a key pipeline that runs non-stop for a long time (such as the main steam of a power plant), don't use non-metals cheaply; If it is an auxiliary pipe that is easy to maintain and replace (such as dust removal system and flue bypass), non-metal will be very fragrant. And don't forgetNational Standard for Non-Metallic Expansion Joints JB/T 12235-2015When selecting, compare the temperature-pressure curve in the standard, and don't use it beyond the parameters.
In one sentence: Non-metallic compensators do withstand high temperatures, but it depends on how high, what medium and how much pressure. Don't be fooled by the name, it's the exact opposite of "intolerant to high temperatures"-it's pressure, not temperature, that really limits positioning.

How to connect a metal expansion joint? Find out which model to use first

I received a phone call from a customer two days ago, saying that the steam pipe leaked only three months after installing the expansion joint. I asked him what model he used, and the answer was "just an ordinary metal expansion joint". Tsk, that's the problem —Method of joining metal expansion jointIt's not a matter of screwing a wrench. If you choose the wrong model, the rest will be for nothing.

The universal corrugated expansion joint is suitable for pipelines with axial displacement as the main; Large tie rod expansion saves energy and carries lateral displacement, but tie rod is the core; Pressure balance type (such as straight pipe pressure balance expansion joint and curved pipe pressure balance expansion joint) is specially designed to deal with high pressure and large diameter, so that the blind plate force does not spread outside. There are also high-temperature axial expansion joints, external pressure single axial expansion joints, double hinge transverse expansion joints... Each structure determines its joining method difference. If you use the high-temperature type as a general-purpose type, the bellows will burn through directly. This is not a joke, but a real thing.

Key checks before installation: Should tie rods and screws be removed or left?

Many masters get the expansion joint, and when they see the tie rod and adjusting screw, they mutter: Is this a transportation protection or a permanent part?

For universal corrugated expansion joints and high temperature axial expansion jointsThe limit tie rod and adjustment screw that came with the factory must be removed or loosened to the designed position before installation. Why? Because their role is to prevent the bellows from being overcompressed or stretched when transported and hoisted. After the pipeline docking is completed, if the tie rod is still screwed to death, the expansion joint will lose its compensation function, which is no different from a section of steel pipe. Two days ago, in a power plant project, the workers didn't dismantle the tie rod, and the bellows bulged directly during the pressure test-the pressure was carried by the tie rod, but the bellows was damaged.

The large tie rod expansion joint and the tie rod on the pressure balance expansion joint are structural parts and cannot be disassembled! Because the big tie rod has to bear the blind plate force generated by internal pressure, you remove the tie rod, and the bellows deforms instantly. Therefore, be sure to look at the nameplate and drawings before installation, and distinguish between "transportation limit" and "working tie rod".

Detailed explanation of installation steps: key points of centering, welding and fixing brackets

Step 1, Align. The pipe flange surfaces must be parallel, and the deviation must be controlled within 1-2mm. If you take the level to hit it, if the bellows is twisted, the life will be directly discounted by 50%. Step 2, welding. If it is a welded expansion joint, fix it by spot welding first, observe the deformation amount, and then weld it in layers, and the thickness of each layer does not exceed the diameter of the welding electrode. The welding current should not be too large to prevent the heat-affected zone from burning the thin wall of the bellows. It is recommended to wrap a damp cloth around the outer wall of the bellows for cooling. The third step is to fix the bracket. Remember one principle: the first bracket at both ends of the expansion joint must be a fixed bracket or a guide bracket to prevent the axial thrust of the pipe from pushing the expansion joint askew. EspeciallyDouble hinge expansion joint of air-cooled island vacuum pipeFor this large-size product, the spacing of brackets must be made according to the design drawing, and one less bracket may lead to hinge failure.

Many on-site diagrams save trouble, and the expansion joint is directly welded to the unfixed pipe. As a result, as soon as the temperature rises, the pipe drifts with the expansion joint, and the compensation amount is all wasted. And guess what? Finally reworked and removed, the bellows has been permanently deformed.

Differences in joining methods of different types of expansion joints

• Universal corrugated expansion joint: Axial displacement, remove the limit pull rod during installation to ensure the free expansion and contraction of the bellows. Pay attention to the direction of the deflector-the arrow must point to the direction of the media flow, otherwise the deflector will be washed off.
• Large tie rod expansion joint: For lateral displacements, such as L-pipe corners. The pull rod cannot be removed during installation, and the nut should be adjusted so that the pull rod is in the force balance position. The FAQ asks "How to adjust the expansion joint tie rod nut"? Generally, it is pre-tightened to 80% of the design length first, and then fine-tuned after the pipeline hydraulic pressure test.
• Straight pipe pressure balanced expansion joint: Working bellows and balancing bellows at both ends with tie rods in the middle. During installation, the three chambers must bear pressure at the same time, so the tie rod should never move. Moreover, this kind of expansion joint usually comes with its own fixed bracket, and only a guide bracket needs to be set on the spot.
• Curved tube pressure balance expansion joint: More complex construction for elbow sections that need to absorb combined axial and lateral displacements. Pay attention to the coaxiality of flanges at both ends when installing, deviation more than 2mm will cause bellows to twist.
• Compound hinge transverse expansion joint: Consists of two hinges and a set of bellows that absorb only the lateral displacement in the plane. The hinge pins must be lubricated during installation and are not allowed to withstand torsional torque.

And there's alsoExternal pressure single axial expansion jointIts bellows is on the outside, subjected to external pressure, and the installation direction has strict requirements. The exhaust hole on the housing must face upward, otherwise the condensate will not drain out-this is where many novices roll over.

Post-installation commissioning and acceptance: displacement inspection and leak test

Measure the length of the expansion joint in the cold state with a dial gauge or vernier caliper and record the initial value. Then introduce the medium (water or gas), slowly raise the temperature to the working temperature, and measure the length again to see if the actual displacement is within the design range. If the actual displacement is larger than the design value, it means that the pipe fixing bracket has failed or the spacing of the guide bracket is too large. If there is no change, congratulations, you may have forgotten to remove the limit rod.

Leak tests must also be done. For corrugated expansion joints used in power station industry or metal corrugated expansion joints in cement industry, it is usually required to hold pressure at 1.5 times the design pressure for 30 minutes without leakage. Small diameter can use compressed air with soapy water, large diameter can use ultrasonic leak detector. Pay special attention to weld seams and bellows crests-that is where cracking is most likely.

Method of joining metal expansion jointIt is not an isolated operation, it has to be matched with pipe design, support arrangement, and media characteristics. The stress analysis of the same model, used in steam pipes and used in flue gas pipes, is completely different. So, don't use "universal type" as a universal plaster. If you are not sure, flip through the product information on the station, or ask the manufacturer's technical engineer directly-it is much more troublesome than thinking about it yourself.

The customer asked "Does it count as equipment"? Find out what a non-metallic compensator is

Two days ago, a purchaser of desulfurization projects called and asked, "Does the non-metallic compensator count as equipment? Our boss asked me to go through the equipment procurement process, but the finance said that this thing is a pipe fitting, and I argued for a long time." This problem is actually quite typical. You say it is a pipe, it does fit on a pipe; But you say it's just a pipe fitting, and it comes with flanges, with deflectors, with insulation, and even with tie rods and limit devices. Tsk, everyone was confused.

Non-metallic compensator, also called non-metallic expansion joint, fabric fiber expansion joint, rubber compensator, rubber PTFE compensator, is essentially a flexible connection device. It is composed of skin (fluorine adhesive tape, silicone cloth, PTFE, etc.), insulation cotton, steel structure frame, beading and bolts. Unlike metal expansion joints, which absorb displacement by bellows, non-metals are deformed by fibrous materials and elastomers. It absorbs a large range of heat displacement, compensation directions, and can also be resistant to corrosion and high temperature. Its shadow is everywhere in the flue duct of power station, the flue gas at the tail of cement kiln, and the inlet and outlet of desulfurization tower. Does it count as a device or not? Let's look down.

Classification by Industry Standard: Does it fall under "Pipe Accessories" or "Equipment"?

Look at the national standard JB/T 12235-2015 "Non-metallic Expansion Joint". The standard name says "Expansion Joint", and the catalog is classified in the machinery industry standard, juxtaposed with pumps and valves. However, in GB/T 20801 "Pressure Pipe Code", non-metallic compensators are classified as "pipe components" (that is, pipe accessories). This brings up an interesting situation: from the perspective of pipeline system, it is just a flexible section of pipeline; However, from the manufacturing and design point of view, it has independent structural design, bearing pressure calculation and fatigue life evaluation.

Metaphorically, like a turbocharger on a car – it counts as an accessory on the engine, but when you buy it separately, it's a piece of equipment. The same goes for the non-metallic compensator: it is responsible for thermal compensation in the pipeline, but in fact its skin, insulation, frame and seal have to be designed individually according to the working conditions. Have you seen which tube sells for 1500 and still have to do finite element analysis? A non-metallic compensator will do. So from the perspective of engineering procurement, I prefer to treat it as equipment. Otherwise? You buy it as a pipe fitting, but it can't be installed on site. Who is responsible?

Compared with metal expansion joints, are the "equipment properties" of non-metals weak or strong?

Metal expansion joints (such as general-purpose corrugated expansion joints and high-temperature axial expansion joints) usually only use bellows and end pipes, and their structure is relatively simple. However, the structure of the non-metallic expansion joint is more complicated: the skin is covered with at least three layers (anti-corrosion layer, airtight layer and insulation layer), the inner lining has a guide tube, and the outside has a steel frame and compression bolts. If it is a rectangular non-metallic expansion joint, the frame is still a welded part, which involves blanking, assembling, welding and airtightness inspection. Can such a set of things be called pipe fittings?

Let's talk about shopping. You can select the metal expansion joint according to the nominal diameter, pressure and compensation amount, but for non-metal expansion joints, you have to provide the medium composition (acid fog? Wet smoke?), temperature range (what is the instantaneous high temperature?), three-dimensional displacement (axial, transverse and angular), and installation space size. Here, can you tell me which pipe fitting requires such complex technical parameters? Therefore, the "equipment attribute" of non-metallic compensator is not only weak, but stronger than that of metal expansion joint. It is essentially a customized flexible structural component.

From power stations, cement to desulfurization flue gas, how to identify and select the type on site?

Non-metallic compensators used in power station industry, such as corrugated expansion joints used in power station industry, sometimes choose non-metallic, but more of them are rectangular non-metallic expansion joints used in flue ducts. When selecting the model, focus on the temperature-the flue gas temperature at the boiler outlet can reach 450℃, and the skin must be made of fluorine tape plus multi-layer ceramic fiber. Both metal corrugated expansion joints and non-metals are commonly used in cement industry, but the dust at the outlet of the preheater is large and the temperature fluctuates drastically, so the fatigue resistance of non-metals is better. Desulfurization flue gas is more typical-flue gas has high moisture content and is corrosive, and it is often used with flue gas baffle door and desulfurization flue gas baffle door. When purchasing on-site, some units classify it as "valve accessories" and some as "boiler auxiliary machines". Very few are thrown directly to the hardware vault anyway.

I have seen a power plant buy the non-metallic compensator as an ordinary pipe fitting. As a result, after the arrival, the flange bolt holes didn't match, and the skin material was wrong. Finally, it returned it and redone it. It delayed the construction period for half a month. What are you saying this isn't a device? The equipment must have technical agreement, drawing confirmation and factory inspection report. The standard of non-metallic compensator clearly requires air tightness test and withstand pressure test, and each one should be done. How can pipe fittings get this treatment?

Conclusion: Non-metallic compensators are equipment-but don't buy them as regular pipe fittings

Do non-metallic compensators belong to equipment? The answer is: in terms of functionality and how it is used, it is the device. You can go through the equipment procurement process, file according to equipment management, write technical agreements, and accept the goods. But the key is not the status, but how to use it. If you regard it as equipment, you will naturally pay attention to the selection parameters, installation specifications and later maintenance; If you regard it as a pipe fitting, there is a high probability that you will ignore the details of the installation direction, the fixed bracket setting and the skin tightness control. And those details are precisely the key to whether it can be used for its full life.

Alas, at the end of the day, the name doesn't matter, it's important not to treat it like a pipe that can bend. Next time someone asks you, "Is the non-metallic compensator considered equipment?" Let him see the test clause of JB/T 12235-light air tightness pressure test, which is enough to draw a clear line between it and ordinary pipe fittings.

What the hell are fixed rods on non-metallic compensators for? Don't wait until the equipment breaks

Although it is called "non-metal", in fact, the skeleton and fixtures are still inseparable from metal. Many people thought that the bright fixed rod was used for lifting or convenient transportation-two days ago, a customer asked me if this thing could be removed, and I thought it was in the way. Disassembled? You try to disassemble it. As soon as the pipe heats up, the compensator will directly blow you into a balloon. The role of the fixed rod is far more important than you think.

The core task of the fixed rod is one word: limit

Limit excessive tension or compression of the non-metallic compensator in the axial direction (i.e. along the pipe direction). The non-metal loop strap itself is soft and elastic, but it can't stand hard tugging. When the pipe is displaced by thermal expansion and contraction, the compensator should absorb this displacement, but if the displacement exceeds the design value, the ring belt will be torn or folded. The retaining bar acts like a seat belt, telling you: At most you can run this far, and it will be dangerous further forward. In fact, both ends of the fixed rod are connected with connecting pipes or flanges, and a preset installation length is locked by a nut to ensure that the compensator works within a predetermined stroke range.

What's the difference between it and the tie rod on the expansion joint? That's a good question. Tie rods are usually used for metal corrugated expansion joints (such as the general corrugated expansion joints and compound hinge transverse expansion joints in our station). Its main function is to bear the blind plate force generated by internal pressure and prevent the bellows from being crushed to death by axial thrust. The fixed rod of the non-metal compensator is more to bear external loads and limit excessive displacement. In terms of material, the fixed rod of non-metallic compensator is generally made of carbon steel or stainless steel, and the surface is anti-corrosion treated. After all, the supporting flue gas and dust environment is often very harsh-such as the "flue gas baffle door" and "rectangular non-metallic expansion joint" in our product list, which are often used in desulfurization and dust removal pipelines. When corrosive gas rushes, if the pole rusts, the strength will drop, and something will happen.

How to judge if the fixed rod is adjusted properly?

Our product information mentioned the question and answer of "How to adjust the tie rod nut of the expansion joint". Although it is a tie rod, the adjustment logic of the fixed rod is similar. The core parameter is the mounting length-this length must correspond to the free length of the compensator in the cold state. For example, the working temperature of the pipeline is 300℃. When it is installed in a cold state, the fixed rod should be artificially compressed or stretched to a certain amount, leaving a margin for thermal displacement. You fit too tightly, there's no room to stretch when it's hot; Loaded too loosely, the loop straps sag when cold. Many on-site failures, nine times out of ten, are that the nut of this pole is not screwed correctly.

Another real case. A non-metallic compensator is connected in parallel next to our "metal corrugated expansion joint in cement industry" used in a cement factory to absorb the vertical displacement. On-site workers suspected that the fixed pole was in the way, so they dismantled it privately. Results After half a year of operation, the non-metallic ring belt was partially torn and the air leakage was serious. Change the ring belt and shut down for two days, resulting in hundreds of thousands of losses. Later, when the engineer checked, it was the lack of fixed rods that caused the deflection displacement to exceed the standard. Think about it, a pole costs hundreds of dollars, and a circle belt costs tens of thousands of dollars. This account is not unknown.

Finally, let's be honest

When selecting, don't just stare at the material and temperature resistance grade of the ring belt. The design and material of the fixed rod should also be checked. Especially for large-size rectangular non-metallic expansion joints, pole cross-section, thread specifications, and the strength of connecting ear plates at both ends have to be calculated. If you are not sure, read directly the article "National Standard for Non-metallic Expansion Joints JB/T 12235-2015" in our station, which clearly states the requirements for structural parts. With this pole, the compensator really locks the safety bottom line.