On the impermeability of tetrafluorinated materials

This post was last edited by sifangok on 2017-9-10 14:18. What is inside the container? Operating temperature and pressure conditions? Where is the bulge located? Is the bulge present throughout the container?

The container medium is 68-72% nitric acid, at a temperature of 35-50 degrees and a pressure of 30-35 Kpa

Is there no expert to answer? Logically, there should be no problems with using PTFE in nitric acid. However, after more than a year of use, electrical spark tests showed conductivity at the PTFE welds; one of the equipment manufacturers even said that the components needed to be replaced. PTFE should not present any major issues at temperatures below 100 degrees, and my process conditions never exceed 80 degrees, even if that temperature is reached for only a short period of time. Moreover, there is no negative pressure inside the equipment. Could it be a quality issue with the tetrafluoride plate material?

Does the container need to be heated? If necessary, what method is used for heating?

An analysis has now been conducted on the causes of leakage in the PTFE lining; the main reason is that the welding process using electrodes for butt welding is not suitable for environments containing NO2 or N2O4. All leakage points are located at the edges of the welds, where carbonization occurs due to thermal expansion and contraction. Leakage is caused by NO gas penetrating through the welds. The electric spark test on the bulged PTFE sheet did not produce any sparks. So, in such a situation, what kind of manufacturing process would be suitable for these operating conditions?

The container temperature is determined by the temperature of the medium itself; one of the tanks contains 98% concentrated nitric acid, which includes NO gas

This post was last edited by Wuxi Teflon Anti-corrosion on 2017-10-19 08:43. Your question is not professional; 1. Penetration depends on factors such as molecular structure, thickness, density, and pressure. Nitric oxide gas will certainly be able to penetrate tetrafluoroethylene sheets, though the amount may be so small that it’s not detectable. Both HF and HC can penetrate tetrafluoride plates. Gas permeates more easily than liquid. 2. The impermeability of domestically produced PTFE sheets is not necessarily worse than that of imported PTFE sheets. Another property that is the same is density: materials with a higher density have stronger resistance to permeation than those with a lower density. Reason for the bulge: 1. Technical issue on the part of the manufacturer – the adhesive was not applied properly. 2. The temperature is higher than that of the glue. 3. Welding issues 4. Molecular penetration. Based on your situation, it’s likely one of the first three.

Most of the companies in China that deal with tetrafluoroethylene-based anti-corrosion solutions are of poor quality; their products are cheap and of inferior standard, and they just hire a few people to do the work. Since customers don’t have much knowledge in this area, suppliers take advantage of them by giving false promises. It’s better to consult reliable manufacturers – not all so-called anti-corrosion companies are capable of handling such tasks. Developing such equipment requires a solid technical foundation. You can consider reaching out to Shangpin Company, which is quite reputable in China

This post was last edited by od110 on 2017-11-16 at 14:22. I’m not familiar with this equipment; if there are bulges in the pipes, there are two possible reasons. First, the medium seeps through the lining and gets trapped between the steel components and the lining, resulting in bulges over time. Second, there might be a vacuum present.