The Water Distribution Automatic Control Management System in the Water Production Room is a pharmaceutical water distribution and transportation management system and equipment specially designed and manufactured by the Engineering Technology Department of Nanjing Novo. The control system uses Siemens automatic components as the main control elements, mainly consisting of Siemens S7-200PLC, M440 frequency converter and MCGS touch screen, supplemented by some on-site sensors such as flow rate, conductivity and temperature to control and record the quality of water. This system can meet the requirements of CGMP for pharmaceutical water distribution and transportation systems. The power and fluid part is composed of sanitary centrifugal pumps, pneumatic diaphragm valves,  pneumatic components and clean stainless-steel fluid pipe fittings. 

　　The purified water distribution control system mainly includes the control of flow rate, conductivity,  low-level alarm handling of the storage tank, pneumatic valves, etc. The electrical control consists of an electrical control cabinet, frequency converter, on-site sensors, various actuating components, PLC and touch screen. Pasteurization is adopted for purified water sterilization:when the water in the tank is heated to 80°C through an on-line heat exchanger, the sterilization timing starts. The sterilization time can be set manually, and automatic temperature control is achieved during the heating process. The injection water distribution control system mainly includes the control of flow rate, conductivity,  temperature, low-level alarm handling of the storage tank, pneumatic valves, etc. 

　　For injection water sterilization, pure steam or superheated water sterilization is adopted(superheated water sterilization:when the water in the tank is heated to 122°C through an on-line heat exchanger, the sterilization timing starts. The sterilization time can be set manually, and automatic temperature control should be achieved during the heating process). When the system enters the sterilization (SIP)state, the sterilization time can only be recorded after the temperature at the coldest point reaches 122°C. If the temperature during the sterilization process is lower than 122°C within the set time, the sterilization timing needs to be restarted. 

　　Data recording:Tank liquid level / Monitoring point temperature / Return water conductivity / Return water flow rate, original operating frequency, etc. The signals are printed and recorded through the configured chart recorder. 

Due to the needs of process production, the temperature of some injection water usage points needs to be reduced, such as waterr for batching, cleaning water, and water for otherproduction processes. When hot water usage points and low-temperature water usage points coexist in the same circulation loop and the number of low-temperature water usage points issmall, using a single-point heat-exchange system is a good option. The commonly used design concepts for single-point cooling mainly include two types:the  "single-point cooling systemafter the water usage point" and the   "Subloop cooling system". 

　　The single-point cooling system after the water usage point achieves thesingle-point cooling function by installing a heat exchanger aat the rear end of the water usage point. This systemuses a double-plate tube heat exchanger forinstant cooling. To prevent microbial contamination, pure steam can be used to intermittently sterilize the heat exchanger and the downstreampipeline. The main advantages ofthis design method are that the risk of contamination to the main pharmaceutical water system islow, and the system interface is very clear. It is mainly usedto reduce the temperature of injection waterat the waterusage points of equipment such as batching tanks and bottle-washing machines. However, since the heat exchanger is placed afterthe valve of the water usage point, the heat exchanger generally needs to be installed in a clean room, and there are high requirements for the cle anliness and installation space of the cleanroom. 

　　The Subloop cooling system realizes the function of the single-point coolingsystem through abranch pipe network. Inthis design, the heat exchanger is installed in parallel with the mainpipe network. When the water usage point does notneed water, this system can be sterilized with pure steam orsuperheated water in synchronization with the main circulation system. Thegreatest advantage of this design method is that it can achievefullautomatic control of the cold-water usage points and minimize the impact on the temperature fluctuations of the main pipenetwork system. The double-plate tube heat exchanger is generally installed in the technical mezzanine. Its requirements forcleanliness and space in the clean room are more favorable thanthe way ofinstalling the heat exchanger at the rear end of the water usage point. It is especially suitable for reducing the temperature of injection waterat open-type water usage points suchas equipment cleaning. The design concept can also be adopted for the liquid-preparation cooling water usage points with a high degree of automation. Its aesthetic design mode andautomatic control method have been accepted by most enterprises. Itshould be noted that, in order to reduce the microbial risk of the system, the number of cold-water usage pointsconnected in series on the branch pipe network of the Subloop cooling system should not be too large, so as to avoid the system contamination risk caused by the excessive length of thebranch pipeline and the long-term residence of cold water. 

　　The Subloop cooling system must install an orifice plate or a diaphragm valve on the main pipe network to create a certain backpressure to ensure sufficient turbulence in the branch pipe network system. For the injection water cold-water usage points designed with the Subloop cooling system, close attention must be paid to the impact of the cooling water side on the service life of the heat exchanger. When the heat exchanger at the cold-water usage point stops cooling, part of the cooling water remains at the shell-side of the heat exchanger. If the cooling water is purged and drained from the heat exchanger, a small amount of residual cooling water in the shell-side combined with air may cause corrosion on the outer side of the heat exchanger, thus affecting the service life and safety of the heat exchanger. Therefore, the US FDA "High-Purity Water Inspection Guide" recommends that when the heat exchanger is not in operation, the cooling waterin theshell does notneed to be discharged.