What exactly does the gasket do?
Many people think that the non-metallic compensator gasket is a "gasket", so long as it is installed without air leakage. In fact, whether it is a rectangular non-metallic expansion joint or a fabric fiber expansion joint, the gasket is the "life gate" of the whole compensator. It has to withstand alternating high and low temperatures, medium corrosion, and pressure fluctuations-if one mat is broken, the whole compensator may be wasted. I have seen a power plant. Just because the sealing gasket was made of the wrong material, in less than three months, the whole non-metallic expansion joint began to leak from the flange surface, and finally even the guide tube had to be replaced. You say it was wrong or not?
It is necessary to stick to high-temperature flue gas, resist condensing acid, and maintain elasticity when the pipeline is repeatedly displaced. Take the one from our stationRectangular non-metallic expansion jointSpeaking, once the seal of the flange surface fails, hot smoke will pop out, which will burn the insulation layer at least and cause equipment accidents at worst.
Material doorway: silicone, fluororubber, PTFE... Who should use it where?
This piece of material has many pits. A quick list of the common ones:
- Silicone pad: Temperature resistance up to and down 200℃, good elasticity, suitable for ordinary flue gas system. But don't go to the high temperature section, it will become brittle when it exceeds 250℃.
- Fluorine rubber pad: It can withstand above 250℃, and is resistant to weak acids and weak bases. It can be used occasionally in desulfurization system, but it still can't be exposed to concentrated sulfuric acid for a long time.
- Polytetrafluoroethylene (PTFE) mat: Almost any medium is not afraid, and the temperature resistance is 260℃. Disadvantages? Poor resilience, easy to permanently deform when pressed. So the people in our stationPTFE compensatorUsually PTFE is used as the inner lining, and the sealing gasket is also made into a composite structure wrapped in PTFE-a layer of elastic rubber is added inside and PTFE is covered on the outside, which is both corrosion-resistant and elastic.
- Rubber PTFE compensatorThe sandwich pad used is smarter: PTFE and rubber are superimposed, corrosion resistance and elasticity are not delayed on both sides.
Do not take ordinary rubber pads to high-temperature pipes. There was a client two days ago,Metal Corrugated Expansion Joints in Cement IndustryThe gasket was replaced with ordinary nitrile rubber. As a result, it was carbonized and cracked in three months, and the flange surface was completely black. Alas, the picture is cheap and suffers a big loss.
Three Signals of Gasket Failure
There are usually three signs that something is wrong with the gasket:
- leakage: If you see traces of media near the weld or flange surface, even a small strip, don't ignore it.
- Hardening or brittleness: It breaks as soon as it is removed, indicating that the material has aged. Sometimes it looks okay on the surface, but the inside is powdered.
- "Shrink" causes bolts to loosen: Not long after installation, the bolt torque dropped. This is mostly the compression permanent deformation caused by over-temperature operation or medium corrosion.
Where are the root causes of these problems? Over-temperature, medium corrosion and improper preloading force-the three culprits. The FAQ on our site has repeatedly mentioned itThe service life of the expansion joint is strongly related to the working conditionAnd the gasket is the same thing. Choosing the right material is more important than anything else.
Replacing the gasket: it looks simple, but many people step on the pit
Change the gasket, do you think loosening the bolts, putting on a new gasket, and tightening it is done? That's naive.
First, you must confirm the type of compensator. Such asElectric plug-in insulation doorOrDouble-sealed single-axis circular baffle doorThe sealing gasket is usually closely attached to the flange surface, so be careful not to hurt the guide tube when disassembling and assembling. Once the guide tube is deformed, the direction of airflow will be chaotic, and the pressure loss will rise.
Secondly, old mat remnants must be cleaned up. Especially the hardened blocks in the corners, flatten them with a small spatula and sand them again. Otherwise, it is a matter of time before the new pad is uneven and the air leaks.
Finally, the preload torque must be according to the manufacturer's recommendation. Too loose and leaky, too tight and crushed the mat. Previous FAQHow to adjust the tie rod nut of expansion jointThat article emphasized the principle of even tightening-the same applies to gaskets. It is recommended to tighten diagonally in three times with 20% afterburn each time, giving the mat a "breath" time.
Three parameters are selected: temperature, corrosion and displacement
So many materials and structures, how do you choose? Remember three core parameters:
- Medium temperature: High temperature scenarios (> 250°C) are preferably a composite mat containing ceramic fibers or a PTFE mat. Don't make do with silicone, it can't hold it.
- Corrosivity: The flue gas desulfurization system contains acidic condensate, so it is necessary to use acid-resistant rubber or PTFE coating pad. In our stationDesulfurization flue gas baffle doorAndRound Flap Door (Double Seal)In all cases, multi-layer sealing structures are used-a layer of acid-resistant rubber as the main seal and a layer of PTFE as anti-corrosion protection, which you can compare and refer to.
- displacement amount: Largely displacedRectangular non-metallic expansion jointThe gasket must leave sufficient compression allowance. Otherwise, as soon as the pipe expands and contracts, the mat will be directly cracked.
Too lazy to check the parameters yourself? It is much more reliable to find the manufacturer to come up with a plan directly with the working condition data than to search blindly on the Internet. After all, a set of compensators is tens of thousands of yuan, and a change of cushions is only a few hundred yuan. Don't lose a big deal.