Circulating water pre-molding scheme

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Circulating Water Pre-coating Scheme

Ⅰ. Purpose of Circulating Water Pre-coating
Circulating water pre-coating is a process in which, after chemical cleaning, a pre-coating agent is added to the circulating cooling water while the system is in operation. As the water circulates, this agent forms a protective layer on the metal surfaces of the water-cooled equipment and the pipelines. Cleaning and pre-coating the circulating water system help to reduce corrosion in the pipes and various cooling equipment, improve the overall efficiency of the system, and protect the equipment and pipelines.

Ⅱ. Conditions and Preparation for Pre-coating
The existing circulating water system has completed its trial operation; all relevant pipelines have been connected, flushing has been done, and there is some flushing water remaining in the system. The source of water for this pre-coating operation is industrial water from a 1000-liter tank.
1. It is necessary to improve the power supply in the circulating water pump room. All three circulating water pumps must be ready to start, and they should be tested before pre-coating begins. The pump room must also have proper lighting and doors/Windows.
2. The industrial water inlet pipelines connected to the 1000-liter tank, as well as the pipelines for replenishing water into the circulating water tank, must be in place. Float level gauges must also be installed and calibrated accurately.
3. The water currently present in the circulating water tank and the 1000-liter tank must be drained completely, and industrial water must be used to fill both tanks.
4. Prepare 201.5 kg of Y508 chemical cleaning agent, 850 kg of Y518 pre-coating agent, and 88.5 kg of Y528 catalyst. Store these substances in a cool and dry area near the circulating water tank.
5. At the valve chambers at the end of the main circulating water pipelines, prepare 2 submersible pumps and temporary power sources for drainage purposes.
6. Prepare protective equipment: 2 sets of protective clothing, 2 gas masks, 2 pairs of water boots, 2 pairs of protective goggles, and 2 pairs of rubber gloves.
7. Prepare tools and equipment: 1 set of adjustable wrenches, several F-type valve wrenches, 4 walkie-talkies, and 3 pre-coating inserts.
8. The instrumentation and analysis departments must be prepared to provide support.

Ⅲ. Personnel Arrangement
1. One team leader who is responsible for coordinating the work of various teams and communicating with relevant departments. It has 5 pre-coating working groups under it. ⒉The Group 1 team consists of 2 members who are responsible for adding cleaning agents, film-forming agents, and catalysts to the circulating pool, monitoring the liquid level in this pool, and operating the valves that control the flow of recycled water into the cooling tower as well as those for discharging waste water. ⒊The team 2 consists of 2 members who are responsible for operating the two valves at the end of the main pipeline, carrying out waste discharge operations as instructed, and operating the submersible pump for drainage. ⒋Two members are part of Group 3; their task is to carry the necessary tools while inspecting the lines, making any necessary adjustments to the process, checking the condition of all connections, and tightening them promptly in case of any leaks. ⒌One member from Group 4 is responsible for monitoring the liquid level in the 1,000-liter tank, keeping records of it, and adding water to the circulation tank as instructed. ⒍One member from Team 5 (with shift rotation arranged if necessary) is responsible for all operations related to the circulating water pump, and must constantly monitor its operation. Any abnormalities detected should be reported to superiors; if necessary, the pump should be shut down and records kept. ㈣ Operation steps: The pre-coating process follows this sequence: discharge of wastewater → physical and chemical cleaning → discharge of wastewater → cyclic pre-coating → discharge of wastewater. 1. All team members take their positions; the 3 teams check the flow in the circulating water system, ensure that the inlet and outlet valves of all equipment are closed, and close the valve leading to the water cooling tower. The cross-connections between Structure 1 and Structure 3 are fully opened ； The two groups prepare for sewage discharge; once the process inspection is complete, they inform the team leader via walkie-talkie. ⒉The members of Group 5 checked the condition of the circulation water pumps, confirming that all pumps and accessories were in good condition and ready for operation. They opened the inlet valve of Pump C to start it, then slowly opened the outlet valve of the pump, paying attention to the pressure at the pump’s outlet. Once the outlet valve was opened to a certain degree and the outlet pressure stabilized, they used walkie-talkies to inform the team leader, who then instructed Groups 1 and 2 to open the drain valves in order to replace the water inside the pipes with industrial water. They also informed the members of Group 4 to add water to the tank ； Team 3 patrols the lines to check the condition of all connections. ⒊When the water discharged from the sewage outlet is basically clear, Teams 1 and 2 inform the team leader for confirmation; Team 3 is then instructed to open the inlet and outlet valves of all equipment and close the two cross-connected lines. Team 1 opens the valve leading to the water cooling tower. Once it is confirmed that the entire system has been thoroughly flushed, the pump is stopped. Teams 1 and 2 close the sewage discharge valves, and water supply is halted once the circulation tank is full. The team leader should contact the laboratory to have water samples analyzed for calcium ions, iron ions, and pH level, with proper recording of the results. ⒋The team leader instructed the members of Group 1 to put on their protective equipment and to add 201.5 kg of the Y508 physicochemical cleaning agent to the circulation tank at one time. After the addition was complete, they were told to start the pump so that the chemical could circulate within the system; Group 3 was tasked with monitoring the pipelines. ⒌The circulating water operates in a closed loop for about 10 hours. The members of Group 1 monitor the degree of turbidity in the water tank; when there is no change in turbidity over a certain period of time, they inform the team leader to contact the analysts for testing and confirmation. At this point, the levels of turbidity, calcium ions, and iron ions should be at their highest, with no changes over that period, after which the cleaning process is completed. The team leader instructed Teams 1 and 2 to start discharging waste. ⒍For this sewage replacement, the method of large-scale sewage discharge and large-scale water replenishment is used to replace the water within the system. Discharge occurs at two points at the end of the main pipeline, and at one point in the return pipeline at the circulation tank; discharge takes place at all three points simultaneously ； Open the two valves at the ends of Group 2 fully, and start the two submersible pumps to drain water; for Group 1, open the sewage discharge valve at the circulation pool. Group 4 should increase the water supply to the circulation tank; when the water supply volume is between 450 m3 and 520 m3, meaning the concentration ratio is less than 1.2 (the water supply volume can be calculated based on the liquid level in the 1000 m3 tank), the water supply should be stopped once the displacement process is complete. The team leader should then be informed to have Group 5 shut down the outlet of the circulation pump in order to stop the pump from operating. Groups 1 and 2 should also shut off the waste water discharge, and the team leader should be notified of this. ⒎After the replacement work is completed, the team leader shall contact the laboratory for analysis; at this point, the turbidity of the circulating water should be less than 20 mg/L, the calcium ion concentration in the water should be at least 50 mg/L, the total iron content should be less than 5 mg/L, and the water temperature should be above 15°C to meet the standards. ⒏Once the analysis showed that everything was satisfactory, the team leader instructed Team 1 to add 850 kg of Y518 pre-film agent and 88.5 kg of Y528 catalyst to the circulation tank at one time. Team 3 was asked to check the discharge lines and all connections to ensure they were closed properly, while the members of Team 5 started the circulation pump to carry out pre-film treatment of the system. ⒐After 3 hours of cyclic pre-coating, the team leader instructed one group of workers to hang the 3 test pieces in the designated locations in the tank. Approximately 2 to 3 hours later (the exact time depending on on-site observations), the test pieces were taken out for inspection; pre-coating was considered successful when there were no signs of rust on the pieces and a uniform colored film covered their surfaces. ⒑After successful pre-coating, the team leader instructed Team 3 to inspect the lines; once it was confirmed that everything was normal, the members of Team 5 remained to monitor the circulation water pump while the rest could leave. After 20–48 hours of circulation pre-coating, when the results were satisfactory, the team leader organized the personnel to replace the wastewater discharge system. ⒒After the replacement method in ⒍ is completed, proceed to the normal addition of corrosion inhibitors and scale inhibitors. ㈤ Precautions: ⒈ Personnel responsible for adding chemicals must wear appropriate protective equipment during operations to prevent accidents. ⒉Personnel in Group 1 must be careful while working in the pool to prevent falls into the water. ⒊Considering the water temperature requirements for physical cleaning and pre-coating, these two steps should be carried out during the day as much as possible. ⒋For the 5 groups of personnel, during the pump shutdown process, the standby pump should be started first; once the standby pump is running stably, then the operating pump can be shut down. ⒌All departments should give advance notice and prepare to cooperate.