Wrong compensator selection? Don't worry. Look here for the remedies

Wrong compensator selection? Don't worry. Look here for the remedies

Last week, a power plant customer called in an extremely anxious tone- -one of their high-temperature steam linesUniversal corrugated expansion jointSteam leakage began after less than three months of operation. When removed, dense cracks appear on the surface of the bellows, which is typical of overtemperature aging. When selecting the model, the medium temperature is regarded as normal temperature, and the actual steam temperature is 450℃, far exceeding the upper limit of 350℃ that the general-purpose model can bear. This kind of thing is too common on engineering sites, but don't panic, most selection errors have room to be remedied, provided you have to figure out where it went wrong first.

Section 1: What is wrong in the selection error?

• Temperature rollover: Use the general-purpose type as a high temperature, such as usingUniversal corrugated expansion jointTo carry high-temperature steam, the corrugated pipe material accelerates its creep at excessive temperature, and it will crack in a few months.
• Pressure rollover: The pressure level is selected low, and the pipeline is directly blasted as soon as it is pressurized-there is no regret medicine for this mistake, but it is more common to only look at the design pressure without considering the test pressure when selecting the type. The operating pressure is normal, and it collapses during the hydraulic test.
• Displacement type confusion: putAxial expansion jointHard-mounted on pipes requiring lateral displacement, or withExternal pressure single axial expansion jointDeabsorbing the angular displacement, the bellows quickly becomes twisted and deformed.
• Miscalculation of medium corrosion: Conveying sulfur or chlorine-containing media, but with ordinaryMetal hose, perforated lining after a few months. The right thing to do is usePTFE-lined hoseOrPTFE compensator。

These mistakes will not burst the pipe immediately, but fatigue cracks, leaks, and even pull-off will come to your door after hundreds of hours of operation. On-site inspection to see more: Is there any abnormal vibration in the pipe? Is there any bulging or rust on the bellows surface? Is there any abnormal noise at the flange connection? These small signs can help you "confirm the diagnosis" in advance.

Section 2: After diagnosis, remedy according to the situation

Not all mistakes have to be disassembled and reinstalled, and handling them according to situations can save a lot of money and time.

Case 1: Displacement Calculation Deviation
For example, the designed axial displacement is 20mm, and the actual thermal expansion of the pipe is 25mm, but it is still within 80% of the rated displacement of the bellows. At this time, you can adjust Expansion joint tie rod nutTo fine-tune the amount of pre-compression. For the specific adjustment method, refer to our previous"How to adjust the tie rod nut of the expansion joint"The core principle is to loosen the locking nut and rotate the tie rod to change the initial length of the bellows so that it works within the service interval. If the displacement deviation is too large, a limiting device can be installed to prevent over-stretching.

Case 2: Liner damage due to media corrosion
Conveying highly corrosive media but using ordinary metal hoses? Don't think about it, just change it. Remove the old piece and replace it with one of the corresponding material-such as PTFE-lined hoseOrPTFE compensator。 Note that the thickness of the liner should match the medium concentration and temperature, otherwise it will leak again after a few months. If you are not sure, send us the media composition list and temperature and pressure to help you check the corrosion resistance data.

Scenario 3: Insufficient pressure level
This is the worst thing. Don't make do with it-the high-pressure pipe blew up is no joke. The machine must be stopped, the compensator removed, and replaced with the same model but with a higher pressure rating. For example, the original one was 1.0MPa Straight pipe pressure balanced expansion joint, the actual system pressure is 1.6MPa, then replace it with 1.6MPa or 2.5MPa specification. By the way, check the pipe brackets and foundations for damage.

Section III: Temporary Emergency Measures

Before the spare parts arrive, one day of on-site shutdown may be hundreds of thousands of losses. Can you carry it? Yes, but only to "delay".

• Install external protective sleeve: LearnSleeve type pipe expansion jointThe structural principle is that an outer sheath is welded with a steel plate and sleeved at the leakage point, and a high-temperature-resistant sealing gasket is filled inside to temporarily seal the leakage. Note that this can only be used at low pressure and low temperature. Don't try it at high pressure.
• Reduce operating parameters: Pressure reduction and temperature reduction operation. For example, when the steam pipeline drops from 10MPa to 6MPa, and the temperature drops from 450℃ to 350℃, the stress energy of the bellows drops greatly. But remember to support the longest maintenance cycle (generally no more than three months), and then it must be changed.
• Handle flue gas baffle door sealing is not tight: If yesDesulfurization flue gas baffle doorOrDouble-sealed single-axis circular baffle doorWrong selection leads to lax sealing, you can temporarily replace the sealing packing, or adjust the bolt pre-tightening force of the compression mechanism. However, temporary measures treat the symptoms rather than the root cause, and the baffle door with corresponding specifications has to be changed for a long time.

Section 4: Pit Avoidance Guide during Re-selection

Each experience leads to wisdom. Before the next selection, honestly list the working condition parameters clearly, don't be too troublesome. Parameters that need to be noted include:

• Media composition: Does it contain sulfur, chlorine, acid and alkali? These direct decisions are made usingMetal hoseStillPTFE-lined hoseOrPTFE compensator。
• Temperature range: Maximum, lowest, normal operating temperature. High temperature separationHigh temperature axial expansion jointOrExternal pressure single axial expansion joint； For low temperature (such as air-cooled island vacuum pipe)Double hinge expansion joint for air-cooled island vacuum pipeline。
• Pressure rating: Design pressure and test pressure are two different things, according to the test pressure when selecting the model.
• Type and amount of displacement: axial, lateral, angular, the magnitude of each displacement. For example, if the pipeline needs large lateral displacement, you can chooseCompound hinge transverse expansion jointOrCurved tube pressure balance expansion joint。
• Pipe arrangement: For buried pipelinesDirect buried (fully buried) type expansion joint； Used in cement industryMetal Corrugated Expansion Joints in Cement Industry； For vacuum pipeSpecial hose for vacuum。

Filling in a selection form for these parameters and sending them to the manufacturer is 10,000 times better than remediating them afterwards. Don't use "probably" or "almost" to make up, data accuracy is the lifeblood.

Section 5: The most hassle-free way-find a manufacturer to do technical review

And guess what? Many customers sent us the parameters, but when they installed them, they found that they chose the wrong one-it turned out that the "medium temperature" was written as normal temperature in the parameter table, which was actually high temperature. In fact, before ordering, send the pipe drawing, media parameters and installation position photos, and our technical support will help you review the selection. Especially for these special operating conditions:

• Flue should be usedNon-metallic expansion joint (fabric fiber expansion joint)StillRectangular non-metallic expansion joint？ It mainly depends on the temperature, pressure and whether corrosion resistance is needed. The temperature resistance of fabric fibers generally does not exceed 250℃, and rectangular non-metals can be made higher.
• Double-sealed single-axis circular baffle doorAndElectric plug-in insulation doorHow to choose? The former is used when the smoke and air system needs to be sealed and isolated, and the latter is suitable for working conditions where the material needs to be completely cut off. The professionals can see the pits in the pipe arrangement at a glance.
• High temperature and high pressure large diameter pipeline, forLarge diameter thick wall expansion jointStillSleeve type pipe expansion joint？ The pressure resistance mechanism of the two is different. The former depends on the elasticity of bellows, while the latter depends on sliding seal. The wrong choice will lead to seal failure.

In the final analysis, compensator selection is not a puzzle, and the four dimensions of temperature, pressure, displacement and medium are indispensable. It doesn't matter if you are wrong this time. Follow the above scheme to remedy it step by step. Next time, give all the parameters and ask a professional to review it again, so you won't step on the pit again.