Why should the non-metal compensator be installed in the furnace roller deviation correction system
I have asked many peers this question, and most of the answer is "absorption heat displacement". But then ask "Why non-metal?", and many people are vague. In fact, there are two core reasons: First, the temperature of the furnace roller area is high, the medium is complex, and the metal bellows can't withstand corrosion and repeated thermal fatigue; Second, the non-metallic fabric fiber layer can effectively isolate dust and harmful gas in the furnace, and at the same time, it can compensate for multi-dimensional displacement. Two days ago, I met the equipment supervisor of a steel plant. He said that the stainless steel expansion joint they used before cracked in three months, so we should replace it with oursNon-metallic expansion joint (fabric fiber expansion joint)After that, it lasted for two and a half years. Do you think this is a big gap?
What is the difference between the non-metallic compensator used for furnace roller correction and the ordinary non-metallic compensator?
Conventional non-metallic expansion joints (such as those used in flues) are mainly responsible for axial expansion and contraction, but in the scenario of furnace roller correction, the furnace roller will have horizontal offset and small angular displacement due to thermal expansion. At this time, the compensator has to have the ability of "correction"-to put it bluntly, it has to absorb both lateral displacement and axial displacement. Our design scheme is to add stainless steel wire mesh reinforcement layer inside the fabric loop band and reserve sufficient lateral compensation margin. There is a key parameter called "compensation vector" when selecting the model. Don't just look at the axial direction, but the lateral displacement must be counted, otherwise it will be decorated after installation. A user suffered this loss, and after installing it for a week, he found that the circle was bulging. After checking, it was found that the lateral displacement was not accurate.
Material selection is the easiest place to roll over
The temperature near the furnace roller is usually between 800℃-1100℃, and ordinary silicone cloth or fluorine adhesive cloth can't hold it at all. High silicon fiber cloth or ceramic fiber cloth should be used as heat insulation layer and coated with high temperature resistant coating. If you choose a conventional rubber compensator for cheap, it will carbonize and crack in less than a month. One of our customers used it on a cold-rolled annealing furnacerubber compensatorAs a result, it smoked on the third day, and later it was replaced with a custom high-temperature non-metallic compensator to solve the problem. Remember one sentence: the furnace roller correction scene, the temperature resistance rating should be high rather than low. Don't ask me why, asking is a lesson.
There are also quite a few pits during installation
Non-metallic compensators cannot be hard connected directly with bolts like metal expansion joints, otherwise the fabric loop belt is unevenly stressed and will tear in a few days. The correct method is to install limit bolts at the flange interface, pre-compress 15%-20% of the axial displacement first, and then fix it. In addition, the furnace roller deviation correction system usually needs to regularly adjust the roller spacing, and it is best to design the two ends of the compensator as live flanges, which is convenient for disassembly and maintenance. Last year, there was a case in which a factory did not leave the loop flange when installing it. As a result, the compensator ring belt was torn when the rollers were changed, and it took two more days of construction in vain. Do you think this wrongful money is worth it?
Lifetime and maintenance are a matter worth chatting about alone
The theoretical life of non-metallic compensators is generally 3-5 years, but it depends on the actual working conditions-if the atmosphere in the furnace contains sulfur and chlorine, the aging rate of the coating will double. It is recommended to check the outer surface every six months for cracks or bulges, and shine the inside with a flashlight to see if the fiber layer becomes brittle. There is a trick: press the loop belt with your hand when the machine is stopped. If the rebound is slow or there is obvious indentation, it means that the elastic layer begins to fail, and it is time to prepare spare parts. Don't wait until the air leaks before replacing it. At that time, the fluctuation of furnace pressure may affect the quality of the plate and strip. If a production line stops for one day, it will cost hundreds of thousands of dollars.
Can you replace it with a metal expansion joint? Don't make trouble
Some users will ask "Can you replace it with a metal expansion joint?" My answer is – stop it. Metal bellows will produce stress relaxation under high temperature, and after the lateral displacement of furnace roller deviation correction is large, the metal parts are easily stuck. OurNon-metallic expansion joint (fabric fiber expansion joint)AndHigh temperature axial expansion jointThere are completely two ways, the former is better than flexible compensation, and the latter is suitable for high temperature and high pressure pure axial working conditions. If you insist on using metal to correct the deviation, it is equivalent to letting the elephant dance ballet, and twisting its waist is considered light. So don't get bogged down, choosing the right thing is saving money.