Take a look at the deformation scene first to judge whether it is "true necrosis" or "false fatigue"
When it comes to compensator deformation, 90% of people's first reaction is "it's broken, change it quickly". But have you ever thought that some deformations are actually normal displacements? For example, if the bellows is compressed or stretched at a certain angle, it can recover itself as long as it does not exceed the design limit. Don't call the manufacturer when you are nervous. Calm down first and do a physical examination yourself.
Specific operation:
- 1. Take a photo first to record the deformation state (front, side, local close-up). This picture saves big trouble when communicating with the technology later.
- 2. Touch the temperature of the deformed part with your hand and compare it with other positions of the pipeline. If it's ridiculously hot, it's probably overheat.
- 3. Check whether there are any signs of liquid leakage and air leakage around. There's a leak, that's really bad.
- 4. Confirm the design displacement parameters by comparing the model on the product nameplate, such as [Universal Corrugated Expansion Joint] or [Rubber Compensator]. The nameplate generally has the maximum compensation amount, temperature and pressure, write it down.
If it is only slightly twisted and there is no leakage, there is a high probability that the thermal displacement is not completely released, so don't scrap it in a hurry. Look at the pipe when it cools down, sometimes it retracts itself-believe it or not?
Step 2: Find out the "mine burial" during installation
Irregular installation is the number one culprit of compensator deformation. Look through the installation records of your home and focus on these 3 locations:
① Fixed bracket and guide bracket
Check if the retaining bracket is actually holding the pipe in place? Some construction sites are fooled with expansion bolts, and the pipeline is directly displaced when it is hot. Is the guide bracket spacing correct? For example, [metal hose] requires one guide per meter, and less will make the hose twist and form an S-shaped bend. Take a tape measure and measure it. It's over spaced? Hurry up and make up.
② Installation direction
Look at the arrow logo! [High-temperature axial expansion joint] and [straight pipe pressure balance expansion joint] have strict requirements on the flow direction, and installing it backwards is equivalent to making the bellows hard to resist the lateral force. Tip: Use a level ruler to measure whether the flanges at both ends of the expansion joint are parallel. If the error exceeds 2mm, you should readjust it. Almost, the transformation came.
③ Pre-stretching/pre-compression
The [Sleeve Type Pipe Expansion Joint] and [Rotary Compensator] usually leave the factory with a pre-stretch amount, and the locking device needs to be loosened after installation. Did you let go? If you don't release it, the compensator will be damaged as soon as the pipe expands. Two days ago, I met a customer who said that [double hinge transverse expansion joint] was seriously deformed. I asked him to check whether the transportation fixtures were removed during installation, but the result was really not removed... It would be fine after dismantling. Alas, this kind of wasted money is painful to spend.
Step 3: Calculate whether there is "anti-aircraft gun to fight mosquitoes" in the selection
If you choose small, you can't bear it, and if you choose big, you waste money, but it is more common to "choose the wrong type". Have you made any of these mistakes?
- The displacement of the pipeline is very large, but the [general corrugated expansion joint] is chosen instead of the [compound straight pipe bypass pressure balance expansion joint] or the [curved pipe pressure balance expansion joint] -as a result, the corrugated pipe is forcibly elongated, resulting in permanent deformation. Do you want to recover? There's no way.
- The medium is corrosive, but ordinary metal bellows are used, and [PTFE-lined hose] or [PTFE compensator] should be used. Corrosion causes thinning of wall thickness, and deformation comes. Have you looked at the inner wall with an endoscope?
- Under high temperature working conditions, non-metallic [rubber compensator] or [rubber PTFE compensator] is easy to age and bulge, so it has to be replaced with [corrugated expansion joint for power station industry] or [external pressure single axial expansion joint]. Don't try to be cheap, the money saved is all pasted and repaired.
Action checklist:
- Take out the site pipeline drawings and confirm the design displacements (axial, transverse, angular). Don't tell me that the drawings are lost... If they are lost, they will be measured.
- Compare the product parameter table you selected to see if the compensation amount is within the safe range (it is generally recommended to leave a 30% margin). It is common sense to leave an allowance, so don't use it at the limit.
- Medium temperature, pressure, corrosivity-three parameters must correspond one to one. For example, it is no problem to use [non-metallic expansion joint (fabric fiber expansion joint)] for flue gas pipelines, but after desulfurization, the wet flue gas has to use [desulfurization flue gas baffle door] with corrosion-resistant expansion joint.
Step 4: Check the medium and environment, don't let "warm water boil the frog"
Many times deformation accumulates slowly, not collapses at once. It's like boiling a frog in warm water, it's too late by the time you find out.
① Temperature exceeds limit
The actual operating temperature is more than 10℃ higher than the design, and the bellows of [metal corrugated expansion joint] will soften and creep, and the first deformation is irreversible. How to check? Use an infrared thermometer to measure the surface of the expansion joint, and continuously record the maximum temperature within 1 hour. Exceeding the design cap? Then you have to consider switching to a high temperature resistant model.
② Pressure fluctuation
[Rubber Compensator] is most afraid of frequent pressure shocks. The pressure rose sharply from 0.5MPa to 1.2MPa, and the rubber layer bulged directly. Operation recommendation: Install a buffer tank or pressure reducing valve before the expansion joint to reduce the water hammer effect. Otherwise, it would be useless if you changed a hundred.
③ Corrosion and wear
The acidic condensate in the desulfurization flue gas pipeline will corrode [flue gas baffle door] and [stainless steel corrugated expansion joint]. Check whether there is liquid accumulation at the bottom of the expansion joint, and install a drain port if so. [Cement Industry Metal Corrugated Expansion Joint] used in the cement industry, dust particles will wear the bellows wall, regularly use an endoscope to see the inner wall. Don't wait for a piercing to regret it.
Note:Don't just look at the expansion joint itself, the state of upstream and downstream equipment also affects the deformation. For example, if the [electric plug-in board insulation door] is not closed tightly, the medium will flow backwards, which will also make the compensator stress abnormally. Check is the valve closed tightly?
Step 5: How many pits have you stepped on in operation and maintenance?
Many deformations are man-made disasters, not natural disasters.
① "Pull" caused by misoperation
When pipeline pressure test, do you regard the compensator as a fixed point? Before the pressure test, the pipeline must be fixed with temporary support, otherwise the [large-diameter thick-walled expansion joint] will be directly deformed as soon as the pressure comes up, just like twisting. Winter parking and restarting, some pipes need to be preheated. It heats up quickly without preheating, and [Double Seal Single Axis Circular Baffle Door] or [Air Cooling Island Vacuum Pipe Double Hinge Expansion Joint] will twist due to thermal shock. You say it was wrong or not?
② Improper maintenance
The fabric fiber layer of [non-metallic expansion joint] is easy to accumulate dust, and if it is not cleaned for a long time, the dust will expand after absorbing water and crush the internal structure. Tsk, you think it's okay if it's dirty? The fastening bolts of [Rubber Compensator] should be tightened regularly. If they are loose, the flange surface will be offset and the rubber body will be torn. Twist the bolts in five minutes. Don't be lazy.
Action checklist:
- Before each start and stop, verify whether the media in the pipeline is emptied.
- Check the surface of the compensator once a quarter for cracks, bulges and corrosion spots.
- For [directly buried (fully buried) expansion joint], because it is buried in the ground, check whether the ground has abnormal uplift or subsidence. There was a bulge on the ground, and something was probably happening underneath.
Step 6: Do-it-yourself to check the three-step method without asking for help
If you haven't found the problem in the previous steps, use this process to do it yourself:
First knife: appearance + size
Use a vernier caliper or tape measure to measure the length, diameter and angle of the compensator. Compare factory drawings to determine the amount of deformation. For example, [metal hose] has an "S" shaped bend, indicating that it has been subjected to lateral force. Where do lateral forces come from? Check if there is a hanger beside it that is crooked.
Second knife: reproduction of working condition data
Adjust the operating temperature, pressure and flow change curves to see whether the high deformation period corresponds to a steep rise/drop. If the [Universal Corrugated Expansion Joint] is twisted, it is mostly due to the torsional load of the pipeline. Check whether there is a valve nearby to open and close quickly. Closing the valve quickly creates torque that the compensator can't handle.
Third Knife: Disassembly Verification
If convenient, remove the compensator and check the internal guide tube (refer to the Q&A "Specific Function of Expansion Joint Guide Tubes" on this site). The misalignment or fall of the guide tube will cause the medium to directly impact the bellows, resulting in local deformation. For [vacuum special hose], use soapy water to detect leakage, and the leakage point is often the deformation and cracking point. Spray with soapy water and where it bubbles is the problem, simple and rude.
Finally, a word:Compensator deformation is not necessarily a product quality problem. Many times, as long as you follow the above steps to troubleshoot, adjust the installation or operation, you can save a replacement fee. If you really can't find the reason, contact our technical support, bring your on-site photos and data, and we can analyze it together. Don't change it blindly. After changing it, it is still broken. That's bad.