Seeking cases and precautions related to the replacement of ion membrane and tank frame large gaskets

1. The edges should be properly treated to prevent the gaskets from shifting, sagging, or falling off due to inadequate treatment when they are applied； 2. It is advisable to prepare additional spare unit slots, as over the course of many years of operation, issues such as pinholes may cause the anode mesh to break, requiring repairs ； 3. Anything that needs to be replaced must be replaced, especially gaskets and the like that have reached their service life ； 4. Strictly prevent chlorine leaks in the plant; the impact on the cathodic coating is even more pronounced in such cases than in new cells, as the individual cells are wet ； 5. Follow the disassembly and assembly manuals strictly. Just because the old membrane is discarded when replacing it, it doesn’t mean care can be taken lightly; however, the electrolyzer is of primary importance and must not be neglected, otherwise frequent repairs will be required in the future, which will also cause trouble for those who carry out the work.

This post was last edited by paul2100 on 2015-6-4 19:27. I’d like to share my experience with these operations with everyone. 1. If maintenance is being carried out on a single tank, it is essential to secure the oil pressure in the other tanks as well. This includes tightening the nuts, as well as securing the inlet and outlet ports of the cylinder associated with that single tank. This is very important, truly very important. To prevent the oil pressure in one tank from affecting those in other tanks, if the locking nut is not in place, the oil pressure in the operating tank will drop. When the internal pressure in the tank exceeds the oil pressure, chlorine, hydrogen, alkalis, and saltwater will escape. We have experienced such an incident once. Of course, if all the electrolyzers are shut down for maintenance, this problem will not exist. 2. When opening or closing the electrolyzer, or adjusting the direction of the hydraulic handle, it is essential to release the pressure first; this is also very important. If pressure is not released, the electrolyte cell shakes quite severely, which has a significant impact on the membrane; the shaking may cause the membrane to leak. 3. After the cell is separated, if the gasket does not fall off, check it for signs of corrosion; if the corrosion is severe, the gasket should be replaced even if it doesn’t fall off. 4. When entering the electrolytic cell to clean the sealing surfaces, pay attention to personal protection; although the cell has been washed, there is still a considerable amount of alkali remaining inside the cathode. It’s best to blow it with compressed air first to remove most of the liquid, thereby preventing it from flowing down; if there is water on the sealing surface, they won’t stick together. 5. For membranes with a high leakage rate, after opening them, check whether there are burrs on the cathode electrode surface and whether the anode electrode surface is smooth. 6. In our case, the gasket for the slot frame needs to be stretched a bit more, so it’s necessary to determine a specific length – just how much to stretch it. It’s not easy to stick it on if it’s too short or too long. 7. If the sealing surface and gasket become dry, they must be applied immediately; otherwise, it will be impossible to apply them later. 8. The rest has been done in accordance with the operating procedures; any issues will be discussed later

The two people upstairs have covered it quite comprehensively; I’d like to add a few points: 1. The coating on the anode’s sealing surface needs to be repainted (this is not necessary for sealing surfaces made of titanium-palladium alloy). 2. The removed cell slot should be thoroughly inspected for the pole grid, including the corrosion condition of the edges around the slot. 3. Before disassembly, record the number; when installing, be careful not to mix up the unit cells in the oxidation zone with those in the reduction zone. 4. It is necessary to ask the ion exchange membrane supplier whether pre-treatment is required before installing the new membrane. 5. Other requirements are to strictly follow the instructions in the installation manual.

This post was last edited by paul2100 on 2015-6-4 at 19:26. Regarding the question from above about whether pre-treatment is needed before applying the film, I’d like to share some insights based on our experience: 1. For Asahi’s film, it needs to be taken out and placed in a solution with an alkali concentration of 0.4% one day in advance (as long as it’s done in advance; there’s no strict deadline specified). Previously, it was placed in a sodium bicarbonate solution at 1.8–2.2% (if I remember correctly), but our manager said that now sodium hydroxide is being used instead. 2. Asahi Glass films and Asahi Kasei films. 3. DuPont membrane: The DuPont membrane is removed on the spot, and the dry membrane is installed directly. We are Beihua Jimei Polar Distance Electrolyzer

Thorough inspection of the electrode surface, training on proper application of gaskets, inspection of the nickel strips on the cathode sealing surface

I agree with what was said above: when the electrolytic cell is opened, the nuts of the other cells remain locked. We called the police once; there was a low oil pressure reading, but no significant fluctuations； At the same time, when starting up with the new gaskets, it is necessary to apply a pressure of 90 kgf for one week, as required by the Japanese side. Once, we reduced the oil pressure and tightened the nuts ahead of time, which resulted in large fluctuations in the zero potential difference

Do you apply the shims directly onto the groove, or do you remove them first before applying? Those in this industry should know the requirements regarding gasket application. Let me tell you about what happened when we started operating the new trough this time. The cell gaskets produced in Tieling nowadays are softer than before; care must be taken when pulling them to control the force applied, otherwise they can easily deform and become unusable. Also, after installing the new gaskets, do not follow any advice suggesting that in order to optimize their performance, the oil pressure should be increased to 9.0 MPa at the beginning. We keep the temperature of the tank at 76°C and raise the oil pressure to 9.0 MPa; as a result, the gaskets in some of the tank compartments get pushed out, which leads to the need to shut down the system for maintenance (we use tanks manufactured by Beihua Machinery; other manufacturers’ tanks might differ). I’m just sharing this as an experience I’ve had. Just imagine: the new machine that the boss invested in yesterday was shut down by us today – I wonder what he must be thinking.

In the case of slotted membranes with zero spacing, it is possible to determine whether there is current bias by checking the degree of contamination of the ion membrane. I was not present when the ion membranes were removed during this major maintenance work; I went there after the removal and noticed that in the upper right corner of the anode side of some ion membranes, the color was lighter, with several brown spots covering an area of about 0.8 square centimeters – this suggests the presence of current bias.

This post was last edited by Du Xiaoping on 2015-6-12 at 12:37. The color in the upper right corner of some ion exchange membrane anodes is lighter – is it near the anode outlet? Determining the degree of contamination of an ion membrane by checking for current drift——I don’t know how to do it.

The degree of contamination varies depending on the area of the ion membrane; however, there are darker-colored spots in the direction of the anode outlet. I initially suspect that the anode weld points coincide with these spots, and this needs to be discussed further