CIP (Cleaning in Place) cleaning systems, also known as CIP (Cleaning in Place), are widely used for in-place cleaning of pipes, tanks, and containers in modern large-scale pharmaceutical, dairy, brewery, pharmaceutical, canning, condiment, and general food plants, where high hygienic and environmental requirements are met.
CIP stands for Clean In Place, also known as online cleaning or cleaning in place. CIP systems, which operate without disassembling process equipment, provide a safe, automated cleaning process through simple operation. They have been widely adopted in industries such as food, beverage, and pharmaceuticals. CIP cleaning not only cleans machinery but also provides microbial control.
CIP equipment often has different components depending on its classification, but generally consists of tanks (drums), piping, heaters, pumps, control cabinets, and ancillary equipment. The entire system is typically constructed of stainless steel. The tank is used to store cleaning fluid, and the inner wall must be polished, with the inner surface Ra≤1.0μm; the outer surface Ra≤2.5μm, and can be treated as needed; the upper and lower heads are disc-shaped and elliptical, and the bottom seal can also be conical. The cone angle can be designed with reference to the repose angle for easy cleaning; the pipelines can be divided into water inlet pipelines, discharge pipelines, heating circulation cleaning pipelines, self-cleaning pipelines, etc. according to their functions; the control valves, online detectors, filters, cleaning heads and other configurations in the pipelines are equipped according to design requirements; the heater often uses plate heat exchangers and serpentine coils for indirect heating, and can also be directly heated with silent steam; the pump often uses centrifugal stamping type. The biggest feature of this type of pump is that the flow-through parts are polished, there are no dead corners, and it is easy to clean, so it is commonly known as a sanitary pump.
The Cleaning Principles of CIP Systems
The cleaning principles of CIP systems encompass multiple aspects, with chemical reagent reaction being the most important factor in determining CIP cleaning effectiveness. Manufacturers typically select appropriate detergents based on factors such as the nature and degree of contamination on the object being cleaned, the materials used, water quality, the cleaning method, cost, and safety. Commonly used detergents include acids, alkalines, and sterilizing detergents. Conventional acid-alkaline detergents typically contain 1%-2% nitric acid solution and 1%-3% sodium hydroxide solution. These detergents are typically heated at 65°C. It is used at 80°C, and chlorine-based disinfectants such as sodium hypochlorite are often used as sterilizers; thermal cleaning method is also one of the important principles. Under certain flow conditions, the higher the temperature, the smaller the viscosity coefficient and the larger the Reynolds number (Re). The temperature rise can change the physical state of the dirt, accelerate the chemical reaction rate, increase the solubility of the dirt, and make the impurity solution easier to fall off, thereby improving the cleaning effect and shortening the cleaning time; the dissolving effect of water cannot be ignored. As a polar compound, water has almost no dissolving effect on greasy dirt, but it has a certain dissolving effect on carbohydrates, proteins, and low-level fatty acids, and has a strong dissolving effect on electrolytes and organic or inorganic salts; in addition, mechanical action is also involved, which is an effect generated by mechanical or physical movement, such as stirring, pressure and friction generated by spraying cleaning fluid, all play a corresponding role in cleaning.
Factors in Selecting a CIP System
1) Equipment Contamination Level, Contaminant Nature, and Product Manufacturing Process
These factors are crucial in determining cleaning effectiveness. Failure to tailor CIP conditions to the specific characteristics of the equipment during cleaning can result in difficulties achieving optimal results or even excessive cleaning costs.
2) Types of Detergents
Currently, the food industry uses a wide variety of detergents, primarily acids and alkalis, with sodium hydroxide and nitric acid being the most widely used. Alkaline detergents are effective at removing contaminants high in protein content, but they can be corrosive to rubber gaskets and other surfaces used in food processing. Acidic detergents are effective at removing stubborn stains that alkaline detergents cannot, but they are somewhat corrosive to metals, requiring the addition of an anti-corrosion agent or rinsing with clean water. Other detergents include surfactants and chelating agents, but these are only used when specifically needed. For example, chelating agents can be used to remove metal ions when the cleaning water is high in hardness.
3) Detergent Concentration
Increasing the detergent concentration can shorten the cleaning time or compensate for insufficient cleaning temperature. Increasing cleaning agent concentration increases cleaning costs, and higher concentrations do not necessarily improve cleaning effectiveness. Therefore, manufacturers must determine the appropriate concentration based on actual conditions.
5) Cleaning Fluid Temperature
Generally speaking, for every 10°C increase in temperature, the chemical reaction rate increases by 1.5-2.0 times, resulting in a corresponding increase in cleaning speed and better cleaning effectiveness. The cleaning temperature should generally be no lower than 60°C.
6) Cleaning Time
Cleaning time is affected by many factors, including the type and concentration of the cleaning agent, the cleaning temperature, product characteristics, production pipeline layout, and equipment design. The cleaning time must be appropriate: too short a time will not effectively remove contaminants, while too long a time will waste resources.
7) Cleaning Flow Rate
Maintaining an appropriate flow rate is essentially about ensuring the flow rate of the cleaning fluid during cleaning, thereby generating a certain mechanical action. This is achieved by increasing the turbulence of the fluid, thereby enhancing the impact force and achieving a certain cleaning effect.
Key Points in Automatic Control and Cleaning Process Design
1) There are two methods for CIP system control: manual control and automatic control.
Manual control relies entirely on manual operation of valves, such as for functions like adding liquid, cleaning, draining, and temperature control.
Automatic control is achieved by the designer setting up the CIP system's instruments and meters to adjust parameters such as flow, temperature, concentration, pressure, and time, as required. This allows the designer to achieve optimal cleaning efficiency with minimal time, effort, and chemical consumption, according to the designated cleaning process. Given the potential harm to humans from cleaning solutions like acids and alkalis, and the importance of effective cleaning in aseptic production, automatic CIP control is particularly critical.
2) Key Design Points for CIP Systems
The key design principle is to base the design on the relevant cleaning process. In other words, designing a CIP system should begin with a thorough understanding of the cleaning process. First, the CIP system should clarify the cleaning target and the cleaning agent required. The number of cleaning agents determines the number of cleaning tanks. Next, the cleaning agent concentration (including water), temperature, pressure, speed, time, distance (from the cleaning tank), and Reynolds number should be determined. Finally, the cleaning sequence should be considered: what should be cleaned first, what should be cleaned last, which should be cleaned once, and which should be cleaned regularly. These principles form the basis for developing cleaning processes and selecting configurations. The key to a CIP system lies in its cleaning process. Equipment is the hardware, and the process is the software. Different cleaning targets (beer, beverages, juice, dairy products, liquid medicines, mineral water, food, cosmetics, etc.) require inherently different cleaning processes.
In summary, the CIP automatic cleaning system, with its unique advantage of enabling safe and automatic cleaning without disassembling the equipment, occupies an indispensable position in modern large-scale food, beverage, and pharmaceutical industries. From the perspective of system composition, the meticulous design and coordinated operation of various components provide hardware guarantees for efficient cleaning. Its cleaning principle integrates chemical reagent reactions, thermal cleaning, water dissolution, and mechanical action, ensuring a multi-pronged approach to cleaning effectiveness. In terms of selection factors, it is necessary to comprehensively consider factors such as the degree of equipment contamination, the type and concentration of cleaning agents, the temperature of the cleaning fluid, time, and flow rate to achieve precise cleaning. The key points of automatic control and cleaning process design emphasize the key role of automatic control and the necessity of scientific design based on the cleaning process. Only by fully grasping these aspects can the effectiveness of the CIP automatic cleaning system be fully utilized to meet the high requirements of various industries for hygiene and production environment.
