Two days ago, a purchaser from a chemical plant came over, saying that the line they transported sulfuric acid-containing flue gas had changed the metal bellows twice in half a year, and it was corroded like a sieve. He asked me if I had anything that could carry acid and stretch back and forth – and I directly pushed him the acid and alkali resistant non-metallic compensator. This thing is nothing new, but it is much more reliable than metal parts in corrosive media pipelines such as chemical industry, desulfurization and electroplating.
What is the "resistance" method of acid-alkali-resistant non-metallic compensator?
To put it bluntly, its core material is polytetrafluoroethylene (PTFE) or rubber PTFE composite layer, plus fabric fiber reinforcement. PTFE has excellent chemical stability. Except for molten alkali metals and fluorine, it is basically not afraid of any acid. With the structure of rubber compensator or rubber tetrafluorine compensator, it can not only compensate the thermal displacement of pipeline, but also block the penetration of sulfuric acid, hydrochloric acid and hydrofluoric acid. If you use metal expansion joints, welds and weaknesses that are broken by acid in minutes, non-metallic ones don't have that problem. And guess what? Some factories continue to use metal parts in order to save money, but as a result, they pierce in less than three months, which is not worth the loss.
What is the difference between its structure and ordinary non-metallic expansion joint?
Ordinary non-metallic expansion joints (that is, we often call fabric fiber expansion joints) mainly rely on rubber and fiber cloth to bear pressure, and their temperature and corrosion resistance are limited. The acid-alkali resistant type will generally be thickened with PTFE or PTFE layer in the inner lining layer, and the outer ring is sealed with high elastic rubber or silicone gel. In some cases, higher temperature resistance is required, such as the desulfurization flue gas temperature of about 120℃, so it is necessary to use PTFE compensator with high-temperature resistant rubber. Note that this thing can't directly replace the metal expansion joint to bear high pressure. If the pressure exceeds 0.5MPa, it has to be recalculated. Don't apply it randomly. The rectangular non-metallic expansion joint and rubber PTFE compensator on our station have corresponding acid and alkali resistance specifications, but the medium parameters must be provided to give the accurate model. If you don't believe me, try it. Ask the model directly without reporting the parameters, and no one dares to make a decision for you.
What is the most taboo when selecting a model?
That is, only look at the three words "acid and alkali resistance", regardless of temperature and medium concentration. In the same factory, the lining thickness and rubber formula of 30% hydrochloric acid and 98% concentrated sulfuric acid are completely different. Another, acid and alkali-resistant non-metallic compensator can usually only absorb axial displacement and a small amount of angular displacement. When the lateral displacement is too large, it must be used with a tie rod or guide tube. Alas, a customer tried to save trouble before and chose a general-purpose corrugated expansion joint to connect the hydrofluoric acid pipeline. As a result, the flange leaked first-this pot can't be dumped to the product.
What are the pits in installation and maintenance?
It is similar to ordinary non-metallic compensators, but there is a pit to note: the sealing gasket at the flange connection must be made of acid-resistant material. Many on-site diagrams save trouble with asbestos pads. As a result, the pipeline was fine, and the flange joint leaked first. In addition, the aging of non-metallic compensators is an inescapable fate, and direct ultraviolet rays will accelerate the aging of rubber. Outdoor installation must be shaded or covered. The life is generally 5-8 years, which is more frequent than metal parts, but it is better than corrosion resistance and worry-free, and the comprehensive cost is low. Is that the truth?
Finally, let's be honest
If your plumbing medium is not corrosive and the temperature is not high, it is more cost-effective to use a universal corrugated expansion joint or metal hose. However, if you encounter "hard stubbles" such as strong acid and alkali, wet desulfurization flue gas and electrolyte, don't hesitate to go directly to the acid-alkali-resistant non-metallic compensator. Although the price is 20% more expensive than that of ordinary non-metals, it avoids the toss of half a year's change-this account will be calculated by veteran chemical drivers.