Cleaning, passivation, and disinfection of purified water pipelines
Release time:2022-11-10
The treatment (cleaning, passivation, disinfection) of storage tanks and stainless steel pipelines in the purified water system is divided into purified water circulation pre flushing → alkaline circulation cleaning → purified water flushing → passivation → purified water re flushing → discharge → disinfection.
During the cleaning, passivation, and disinfection of pipelines, it is not allowed to install ultraviolet lamps, sterilization filters, or filter media, and respirators are not allowed to be installed.
① Purified water circulation pre rinse:
Start the water production system. When about 500L of purified water is injected into the pure water tank, start the pure water pump for circulation. After 15min, open the water valves at each usage point and discharge while circulating. When the pure water in the pure water tank drops to a low level, close the pure water pump, fully open the drain valve of the pure water tank and the valves at each usage point, drain the accumulated water in the pure water tank and pipeline, and then close all the water valves at the usage points on the pure water tank and pipeline.
② Alkali solution cleaning:
l. Start the water production system to produce pure water (do not inject the produced pure water into the pure water tank), inject about 250L of purified water into the cleaning tank, add 2.5 kg of NaOH (chemically pure), stir evenly to make it a 1% NaOH solution, and transfer it to the pure water storage tank with a cleaning pump. According to the above preparation method, repeat the preparation of 1% NaOH solution and transfer it to a pure water storage tank through a cleaning pump. At this time, the volume of 1% NaOH cleaning solution in the pure water storage tank should be 500L.
2. Turn on the purified water pump and circulate 1% NaOH cleaning solution in the purified water tank and delivery pipeline for 2 hours. Open the valves at each usage point on the purified water pipeline, discharge for about 3 minutes, and clean the valves. Fully open the drain valve of the pure water tank, fully open all valves at each usage point, and drain the cleaning solution from the pure water tank and pipeline.
After the cleaning solution is discharged, close the pure water tank and valves at each water point, and prepare for rinsing with purified water.
③ Purified water rinse:
1. Start the water production system and inject the secondary reverse osmosis fresh water into both the cleaning tank for preparing alkali solution and the pure water tank. Use the cleaning pump to transfer the pure water from the cleaning tank to the pure water tank for cleaning.
2. When the pure water in the pure water tank reaches the neutral position, start the pure water pump and rinse the storage tank and pipeline for 30 minutes. Then, open the water valves at each usage point of the pure water delivery pipeline at the same time, making them in a semi open state, and clean the valves with pure water for 3 minutes. Close the pure water pump, open the drain valve of the pure water storage tank and the valves at each usage point to empty them.
3. After emptying, continue to prepare purified water and use the same flushing method as above to cycle and flush the storage tank and pipeline until the pH and conductivity of the pure water tank inlet are consistent with those of the pure water tank, as well as the total sending and returning pH and conductivity.
After flushing, all valves in the pure water tank and various usage points should be opened for emptying. After emptying, all valves in the pure water tank and pipelines should be closed to prepare for passivation.
④ Passivation:
1. Prepare a nitric acid storage tank and water pump, and connect the pipeline to the spray ball on the top of the pure water tank. Connect the secondary reverse osmosis fresh water to the acid tank.
2. Turn on the water production system to produce pure water into the acid mixing tank (pure water is strictly prohibited from entering the pure water tank), add nitric acid (chemically pure) to prepare 500L of 8% acid solution (or pH<1), start the water pump to transfer all the acid solution to the pure water tank.
3. Turn on the pure water pump to circulate 8% (pH<1) acid solution in the purification tank and delivery pipeline for 2 hours, and passivate the inner surface of the pure water tank with nitric acid solution through the spray ball at the top of the tank.
4. Within 2 hours of circulating the pure water pipeline with the above acid solution, open the valves at each point on the purified water pipeline and discharge for about 10 minutes to passivate the valve with nitric acid solution (when passivating the valve, a container should be used to contain the nitric acid solution, which should be poured back into the acid distribution tank and transported to the pure water tank).
5. After the cycle time is over, turn off the pure water pump, fully open the drain valve of the pure water tank, fully open all valves at each usage point, and drain the passivation solution from the pure water tank and pipeline.
6. After flushing, all valves in the pure water tank and various usage points should be opened and emptied. After draining the accumulated water in the pure water tank and pipelines, all valves in the pure water tank and pipelines should be closed to prepare for disinfection.
1.3% hydrogen peroxide preparation: Turn on the water production system, prepare purified water into the cleaning tank (strictly prohibited from entering the purified water tank), inject pure water (250L), add 30% 50L hydrogen peroxide into the cleaning tank, prepare a 6% hydrogen peroxide solution, and transfer it to the pure water storage tank through the cleaning pump. After the transportation is completed, inject pure water (200L) into the cleaning box and transfer it to the pure water storage tank, so that the concentration of hydrogen peroxide in the pure water storage tank is 3% and the volume is 500L.
2. Disinfection: Turn on the pure water pump and circulate 3% hydrogen peroxide disinfectant in the pure water tank and pipeline for 30 minutes, and disinfect the inner wall of the storage tank through a spray ball.
3. Disinfectant discharge: After the circulation of 3% hydrogen peroxide is completed, open the valves at each point of pure water use to a semi open state, allowing the disinfectant to disinfect the valves until the disinfectant is completely discharged. When the disinfectant cannot be completely drained, the pure water pump should be turned off and the drain valve of the pure water storage tank should be opened to drain the disinfectant.
4. Pure water final flushing: When starting the water production system to prepare pure water and placing it in the middle position of the pure water storage tank, start the pure water pump to circulate and flush the storage tank and pipeline for 30 minutes. Then, open the drain valve and various use valves of the pure water storage tank for emptying.
5. After emptying, continue to prepare pure water and transport it to the middle position of the pure water storage tank. Use the above flushing method to cycle and flush the storage tank and pipeline until the secondary reverse osmosis fresh water, pure water storage tank, total delivery, total return pH, and conductivity meet the standard requirements.