Questions about reverse osmosis

Proper installation and removal of reverse osmosis membrane elements: There are specific requirements for the installation and removal of reverse osmosis membranes; improper handling can result in irreparable damage. The following are some guidelines regarding the installation and removal of these membranes. 1. Preparations before installing membrane elements ① Flush the system pipelines: If the system is brand new, it is necessary to thoroughly flush the system pipelines before installing the reverse osmosis membranes, in order to prevent debris, solvents, or residual chlorine from coming into contact with the membrane elements. ② Cleaning the pressure vessel: It is necessary to clean the interior of the pressure vessel before installing the membrane elements, in order to prevent dirt or debris from accumulating on the outer surface of these elements. It is recommended to soak a sponge ball in a 50% glycerin solution, then use an appropriate tool to scrub back and forth inside the membrane shell in order to clean its inner walls thoroughly. During the cleaning process, be careful not to let the tools scratch the inner surface of the membrane shell. 2. Installation sequence of membrane elements: Be sure to install the membrane elements in their corresponding pressure vessels.     ① Typically, membrane elements are stored in a 1% sodium bisulfite solution; they should first be thoroughly rinsed with pure water. ② The feedwater side of the membrane element features a concentrated brine seal ring; note that the installation direction of this seal ring is such that its opening faces upstream. The function of the concentrated water seal ring is to ensure that all of the raw water flows into the membrane element without any bypass flow. The flow rate of the raw water itself causes the opening of the concentrated water seal ring to press tightly against the inner wall of the pressure vessel for sealing. If the installation direction of the sealing ring is reversed, the raw water cannot be sealed properly, causing some of it to flow outside the membrane elements. This reduces the flow velocity on the membrane surface, leading to scaling and thus shortening the membrane’s service life. ③ Confirm that the O-ring is installed in the designated position on the connection fitting. During installation, make sure there are no scratches or contaminants on the O-rings and connection parts. Be careful not to install the O-ring twisted. If the connection leaks, raw water will enter the produced water, causing a decline in its quality. When installing on the water collection pipe, the O-ring and the surface of the water collection pipe should be wetted with pure water, distilled water, or glycerin to facilitate installation. ④ Remove the end plates on both sides of the pressure vessel to install the membrane elements. Install the adapter on the concentrated water side (downstream) of the water collection pipe of the first membrane element. Then, the membrane element is pushed in the direction of the raw water flow and installed inside the pressure vessel. When several membrane elements are installed in sequence, the next membrane element must be prepared for connection to the connectors before the preceding membrane element has fully entered the membrane housing. At the same time, be careful not to let the membrane element come into contact with the edges of the pressure vessel to avoid scratches; push it into the pressure vessel as parallel as possible. ⑤ After confirming that the adapter of the pressure vessel is properly connected, connect the concentrated water side end plate to the membrane shell. For the method of connecting the end plates, please refer to the manufacturer’s instructions for pressure vessels. ⑥ After installing the end plate on the concentrate side, the membrane element should be pushed again from the feed side to the concentrate side to ensure a complete and tight connection. Then, install the inlet side end plate; when installing it, pay attention to measuring the gap between the end plate and the adapter. If there is a gap, install a plastic (or other suitable material) gasket with an inner diameter larger than the outer diameter of the adapter and a thickness of 1/4”–1/8”, until the end plate cannot be fully installed. At that point, remove one gasket and then install the end plate properly. For the method of connecting the end plates, please refer to the user manual provided by the membrane shell manufacturer. 3. Disassembly of the membrane element: ① Remove the pipes surrounding the pressure vessel, and take off the end plates at both ends of the pressure vessel.    ② Push the membrane elements downstream from the raw water inlet, and remove them one by one on the concentrated water outlet side. Do not use a hard metal rod when removing the membrane element. ③ The storage methods for membrane elements are shown in Table 2. Failure to adhere strictly to these requirements may cause changes in membrane performance, so please pay close attention.

This description is a bit complicated; the actual process isn’t difficult – it simply involves pulling the membrane out of its housing, and this step is rather labor-intensive.