Maintenance and upkeep of reverse osmosis equipment during shutdown

Author: Hongjie Water

Once the reverse osmosis system is running, it should be kept in a relatively stable operating state as much as possible. Each start and stop of the system involves changes in flow and pressure, which generate mechanical stress on the membrane components. Therefore, if necessary, try to reduce the frequency of system startup and shutdown as much as possible, and normal startup and shutdown should also proceed smoothly. So how should reverse osmosis water treatment equipment be maintained and maintained after it needs to be stopped for a period of time? The length of downtime varies, and the maintenance measures are also different.

Shutdown precautions:

Considerations and maintenance methods for reverse osmosis system shutdown: 

1. After shutdown, rinse the system with reverse osmosis treated supply water, softened water, or product water; 

2. In order to maintain the performance of the system, the membrane components must always be kept moist; 

3. To prevent the growth of bacteria in pressure vessels, disinfection treatment should be carried out;

4. If the membrane components are contaminated, there may be a system malfunction, so chemical cleaning should be carried out before storage, which can remove dirt from the membrane components and effectively limit the growth of bacteria; 

5. The allowable temperature and pH range for storage in a pressure vessel: temperature range: 0-35 ℃, pH range: 3-7; 

6. The preservation solution is acid Sodium bisulfite (SBS) solution. The water used to prepare the preservation solution must ensure that it does not contain residual free chlorine or other oxidizing agents.

Steps for normal system shutdown:

Open the produced water discharge valve, open the bypass control valve of the high-pressure pump, reduce the inlet flow of the system, and slowly open the concentrated water control valve to reduce the pressure to around 30-40psi. Close the corresponding dosing device, and maintain this low-pressure flushing until the conductivity of the concentrated water is consistent with the conductivity of the inlet water. After 5-10 minutes of low-pressure flushing, the system stops. 

Within two days of shutdown:

Short term shutdown can be carried out according to normal shutdown procedures, but low-pressure flushing is required, and to prevent bacterial growth, flushing is required every 24 hours. 

Shutdown for 3-7 days: 

1. Short term shutdown for 3-7 days, at which time the reverse osmosis membrane remains in the RO system pressure vessel. The storage operation is as follows: 

(1) Flush the reverse osmosis system with water supply, while taking care to completely remove gas from the system.

(2) After filling the pressure vessel and related pipelines with water, close the relevant valves to prevent gas from entering the system. 

2. If the reverse osmosis pure water system is planned to be shut down for more than 168 hours for a long time, a cleaning system can be used to take shutdown protection measures. 

Precautions for long-term shutdown and maintenance of the system:

1. When the temperature is less than 15 ℃, rinse again every 5 days. During system shutdown, the temperature remains between 5 ℃ and 45 ℃. Low temperature is beneficial for the preservation of membrane components, but the system should be prevented from freezing and freezing.

2. For workshops without heating or other conditions, it is necessary to shut down the machine, drain all the water in the pump and membrane casing pipes, and take out the reverse osmosis membrane for separate storage.

• 3. The reverse osmosis membrane must be stored separately in a room equipped with electric heater, soaked with 1.0% Sodium bisulfite solution, but may freeze below 0 ℃; Adding 10% propylene glycol (glycerol) as a protective solution can provide some degree of antifreeze, but it can also freeze below -5 ℃. Therefore, it is recommended to store it at a temperature range of 5 ℃ to 45 ℃, not less than 0 ℃.