Electrolytic aluminum workshop non-metal compensator, should fabric fiber or rubber be selected?
How "ruthless" are the pipes in the electrolytic aluminum workshop? High temperature, hydrogen fluoride, alumina dust, plus continuous vibration. Metal compensators can't last a maintenance cycle under this working condition-corrosion and fatigue cracking are common. Non-metallic compensators (also known as non-metallic expansion joints) are more durable choices. But here's the question: there are fabric fiber, rubber and rubber PTFE on the market. Which one can withstand the "destruction" of electrolytic aluminum?
Don't worry, let's break it up and talk. You choose the wrong material, from changing it once a year to cracking the pipe and discontinuing production-this is not a scare.
Look at the material first: fabric fiber vs rubber vs rubber PTFE
Fabric fiber type (officially called non-metallic expansion joint (fabric fiber expansion joint)) is mainly made of silicone cloth, fluorine tape and multi-layer glass fiber, and its temperature resistance can reach 300℃ or even higher, especially suitable for high-temperature flue gas pipeline at the outlet of electrolytic cell. However, the temperature resistance of rubber compensator (such as EPDM or neoprene) is generally no more than 150℃, and it is mainly used in low-temperature section or dust removal pipeline. Note: There is also a rubber PTFE compensator in this site, which is lined with polytetrafluoroethylene in rubber, which is specially used to deal with fluorine-containing flue gas in electrolytic aluminum workshop, which is highly corrosive. When ordinary rubber comes into contact with hydrogen fluoride, the inner layer will be corroded into a honeycomb shape, and it will leak in three months. Isn't that wasting water?
Key Parameter Displacement: Don't let the difference in expansion ruin the pipeline
The pipeline trend in electrolytic aluminum workshop is complicated, and multi-directional displacement caused by thermal expansion and contraction is common. What about rectangular pipes? Rectangular non-metallic expansion joints (this site has rectangular non-metallic expansion joints) are specifically used to absorb lateral and angular displacements of rectangular pipes, such as smoke exhaust branches between electrolytic cells. For circular pipes, general-purpose fabric fiber expansion joints are preferred. Note when installing: Do not install the guide tube in the reverse direction-the specific function of the expansion joint guide tube is to guide airflow and prevent dust accumulation. If the direction is reversed, it is equivalent to white installation. Think about it, can the compensator still telescope when the dust is stuck in the ripples?
Real case: three months vs two years
They used a certain brand of rubber compensator, and it leaked after only three months. When disassembled, the inner layer was corroded into a honeycomb shape by hydrogen fluoride. It took more than two years to replace the rubber PTFE compensator of this station. What's the problem? It is not that rubber is not good, it is that the selection does not consider the corrosiveness of the medium. The concentration of fluoride in the flue gas of electrolytic aluminum workshop is high, and ordinary rubber can't bear it at all-at this time, the fabric fiber expansion joint of rubber tetrafluorine or perfluorine rubber is the correct solution. In addition, the national standard for non-metallic expansion joints is JB/T 12235-2015. When purchasing, you must ask the manufacturer whether to implement this standard, otherwise it will be three-no products. How much trouble can you save by asking more when you buy it?
Don't step on the "general-purpose" pit
Some people tried to save trouble, and the whole workshop uniformly used a non-metallic expansion joint. As a result, the rectangular pipe used a circular compensator, which forcibly suppressed the expansion difference. Remember, the product line of this station is very complete: non-metallic expansion joints (fabric fiber expansion joints) are selected for circular pipes, rectangular non-metallic expansion joints are selected for rectangular pipes, and rubber PTFE compensators are used for cases where strong corrosion resistance is needed. When selecting, list four numbers: maximum temperature, medium composition (especially fluoride concentration), pipe diameter and three-way displacement. With these data to check the product parameters, it will basically not overturn. Tsk, it's that simple.
Maintenance points: Aging and loose bolts
Although non-metallic compensators are more resistant to corrosion than metallic ones, the fabric fiber layer will age. Check the surface once a quarter for bulging and damage, and pay special attention to loose bolts at flange joints-the workshop vibrates heavily, and the bolts are easy to loosen, resulting in leakage. In addition, how to adjust the expansion joint tie rod nut? Remember: The tie rod nut is locked during installation, and the tie rod can only be loosened to allow the expansion joint to expand and contract freely after the system runs stably. Don't be shocked, loosen the nut after installation, and the displacement of the pipe will directly break the compensator-the picture is too beautiful for me to look at.
In the final analysis, if you choose the right model, implement it according to the standard, and maintain it regularly, the nonmetallic compensator in the electrolytic aluminum workshop will be used for three to five years without any problem.