How to Prepare and Supply Cleaning Solutions for CIP

In a dairy plant, equipment hygiene is non-negotiable. Pipes, tanks, heat exchangers, and filling lines come into contact with milk every hour of production, making them highly susceptible to residue build-up, microbial growth, and mineral deposits. Cleaning-in-Place (CIP) is the industry’s answer – a method that cleans the interior surfaces of processing equipment without dismantling it, using controlled flow of water and chemical solutions. But effective CIP doesn’t just happen automatically. It starts well before the cleaning cycle begins: with the proper preparation and supply of cleaning solutions. How those solutions are prepared, stored, and delivered to the equipment makes all the difference between clean equipment and a hygiene failure.

Why cleaning solution preparation matters 🔗

A CIP system is only as effective as the solutions it uses. According to the Tetra Pak Dairy Processing Handbook, CIP achieves three levels of cleanliness – physical, chemical, and bacteriological – and each depends on the cleaning solution being the right chemical, at the right concentration, and at the right temperature. Get any one of these wrong, and the cleaning cycle either damages equipment or fails to remove residues and microbes.

Human errors in acid or alkali concentration are among the most common causes of premature equipment wear or reduced washing quality in dairy plants. Too little chemical, and biofilm survives. Too much, and surfaces corrode. This is why the preparation and supply of cleaning solutions is treated as a critical control point in modern dairy operations.

The three core cleaning solutions in a CIP system 🔗

Every CIP system works with three fundamental solution types, each targeting a different category of contamination.

Alkaline (caustic) solution 🔗

Sodium hydroxide (NaOH), also known as caustic soda, is the primary detergent in most CIP wash cycles. It works by saponifying fats – converting them into water-soluble soap – and breaking down proteins that cling to stainless steel surfaces after milk processing. Typical use concentrations range from 0.5% to 2.0%, though up to 4% may be used on heavily soiled surfaces. According to the Dairy Processing Handbook, alkaline cleaning is generally done at a minimum of 70°C to match the temperatures the product was exposed to during processing. Other commonly used alkalis include potassium hydroxide (KOH) and sodium carbonate.

Acid solution 🔗

After the alkaline wash, an acid cycle removes what alkalis cannot: mineral deposits, milkstone, and residual chlorine. Nitric acid (HNO₃) is the most widely used acid in dairy CIP, though hydrochloric, phosphoric, and citric acids are also used depending on the plant’s requirements. The acid solution is typically prepared in warm water (around 38-49°C) to achieve a pH of 3 to 4. Acid cleaning is recommended at 60-75°C. If the water supply contains silicates, the pH should not be allowed to drop below 5 to avoid silicate precipitation on surfaces.

Sanitizing solution 🔗

The final solution in the CIP sequence is a sanitizer, which eliminates residual microorganisms after all soils have been physically removed. Hypochlorite solutions (sodium, potassium, or calcium) have long been used as CIP sanitizers and are effective and economical. However, they can be corrosive to stainless steel over time. Increasingly, dairy plants are switching to peracetic acid (PAA) – a combination of hydrogen peroxide and acetic acid – which is effective against a broad spectrum of microorganisms including bacterial spores, leaves minimal residue, and is considered more environmentally friendly.

Two approaches to solution supply: centralized vs. standalone systems 🔗

How cleaning solutions are prepared and delivered to the equipment depends on the size and layout of the dairy plant. There are two main system configurations: centralized CIP systems and standalone (satellite) systems.

Centralized CIP system 🔗

In a centralized system, all cleaning solutions are prepared and stored at a single station, then distributed to the various processing lines across the plant. Water and detergent solutions are pumped from storage tanks in the central station to various CIP circuits, and the detergent solutions and hot water are kept hot in insulated tanks with temperatures maintained by heat exchangers.

A well-designed centralized CIP station typically holds separate insulated tanks for water, alkali solution, acid solution, and sanitizing solution. Each tank is equipped with temperature sensors and, critically, conductivity or pH indicators that continuously monitor solution strength. Tanks for acid and alkali solutions are typically made from SUS316L stainless steel with double-layer construction and polyurethane insulation to maintain solution temperature throughout the cleaning cycle.

The centralized design is particularly suited to large dairy plants where multiple processing lines need to be cleaned, often simultaneously. In such plants, all CIP operations are managed from a single location, with detergents delivered to various washing objects from one station or a coordinated group of stations. Spent solutions are returned to the recovery tanks, where their concentration is checked and adjusted before reuse – a practice that significantly reduces chemical and water consumption.

One important operational rule applies to all centralized systems: detergent solutions must be discharged when they become too dirty after repeated use, and storage tanks – especially the rinse water tank – must be emptied and cleaned at regular intervals to prevent them from becoming a source of contamination in an otherwise clean processing line.

Standalone (satellite) CIP system 🔗

Standalone systems, sometimes called satellite CIP units, are compact, self-contained cleaning stations placed close to the equipment they serve. Decentralized CIP is an attractive alternative for large dairies where the distance between a centrally located CIP station and peripheral CIP circuits would be extremely long, making heat retention and solution pressure difficult to maintain.

Rather than relying on a central storage facility, standalone systems use balance tanks for water and incorporate inbuilt heating elements to bring solutions up to the required temperature on-site. Chemicals are added via dosing pumps that inject concentrated acid or alkali directly into the water in controlled amounts. A simple standalone CIP system typically contains two heated and insulated stainless steel containers for acid and alkali solutions, a tube system with valves, and a concentration indicator.

Standalone systems are particularly common in small to medium-sized dairy operations, or in sections of large plants that are too remote from the central CIP station to receive solutions at the right temperature and pressure. Single-use (Type I) skids prepare a fresh chemical solution for each CIP cycle and discharge spent solution to drain – which is simpler but less economical. Reuse (Type II) standalone systems, by contrast, store and recirculate cleaning solutions across multiple cycles, adding fresh chemical doses to restore concentration as needed.

Key instrumentation for solution monitoring and control 🔗

Whether the system is centralized or standalone, maintaining the correct solution parameters requires reliable instrumentation. Every CIP skid includes tanks, pumps, heat exchangers, and instrumentation to automate the cleaning cycle, and solution quality is monitored in real time.

Temperature control 🔗

Temperature has a direct effect on how well cleaning chemicals work – molecules move faster and reactions proceed more efficiently as temperature rises. Temperature sensors in the tanks and in the return lines confirm that solutions are being circulated at the correct temperature. Solution temperatures should be randomly checked as they return to the CIP unit to ensure that heat is not being lost in transit through long pipelines.

Conductivity and pH monitoring 🔗

The concentration of cleaning solutions is typically monitored using conductivity meters, since dissolved alkalis and acids conduct electrical current in proportion to their concentration. The system automatically controls acid and alkali concentration and initiates compensation dosing when concentration drops below the set point. pH indicators provide a secondary check – particularly important for acid solutions, where the target pH range must be maintained precisely to avoid both under-cleaning and equipment damage.

Chemical concentrations should be tested periodically throughout the cleaning shift using test kits supplied by the chemical supplier, especially in plants without automated conductivity monitoring.

Solution preparation best practices 🔗

Getting solution preparation right is a matter of discipline, not just equipment. Several operational practices are essential for consistent cleaning outcomes.

Water quality: Potable plant water, deionized water, or water processed through reverse osmosis is recommended for CIP solution preparation. Hard water introduces calcium and magnesium ions that interfere with detergent activity and contribute to scale formation. Water hardness should be assessed before specifying solution concentrations.

Chemical dosing sequence: Concentrated acids and alkalis are always dosed into water – never the reverse – to prevent hazardous exothermic reactions and ensure even mixing. Dosing pumps deliver precise volumes of concentrate into the tank, and agitation ensures uniform distribution before the solution is circulated.

Solution reuse management: In many cases, the caustic wash can be returned to its tank and reused multiple times, significantly reducing water, chemical, and energy costs compared to single-use systems. However, reused solutions accumulate soil and their surface tension and cleaning efficiency can degrade. Research on NaOH solutions reused over several days in dairy plants shows that surface tension drops significantly with each reuse cycle, which directly affects cleaning performance. Solutions must be discarded and tanks refilled when contamination levels reach a threshold.

Separation of raw and pasteurized lines: It is advisable to separate CIP equipment used for raw product lines from pasteurized product lines to prevent the spread of surviving spores and bacteria from raw milk zones into hygienically sensitive areas.

Consequences of poor solution preparation 🔗

Failures in cleaning solution preparation have direct and measurable consequences. Improper cleaning and sanitizing protocols have resulted in high costs, product spoilage, equipment damage, and hospitalization of personnel in dairy processing facilities. Under-concentration means biofilm survives and re-contaminates the next batch of product. Over-concentration accelerates corrosion of stainless steel, shortening equipment life and increasing maintenance costs. Incorrect temperatures reduce chemical effectiveness, extending the cleaning cycle or leaving soils behind.

From a regulatory standpoint, dairy plants are subject to strict legal obligations around hygiene. Milk and milk products are among the most heavily regulated food categories globally, precisely because they are ideal growth media for pathogens. Maintaining properly prepared and controlled cleaning solutions is not just good practice – it is a legal requirement in most jurisdictions.

What do you think? Given that both centralized and standalone CIP systems have their own strengths, how should a medium-sized dairy plant decide which configuration best fits its layout and production scale? And considering that reused cleaning solutions degrade over time, what monitoring practices would you put in place to determine exactly when a solution has reached the end of its useful life?

References

1. https://www.spxflow.com/assets/pdf/apv-cip-systems-22003-05-02-2013-gb.pdf
2. https://dairyprocessinghandbook.tetrapak.com/chapter/cleaning-dairy-equipment
3. https://viravix.com/blog/cip-cleaning-in-food-production-enterprises/
4. https://www.csidesigns.com/blog/articles/5-steps-in-a-common-food-dairy-beverage-clean-in-place-cycle
5. https://agrochemusa.com/maximize-performance-efficiency-of-cip-routines/
6. https://fruitprocessingmachine.com/portfolio-items/cip-system/
7. https://filling-pasteurization.com/abfuelltechnik-zootechnika/cleaning-systems/cip-cleaning/cip-system-for-small-and-medium-sized-dairies/
8. https://runlaminar.com/blog/clean-in-place
9. https://www.bccdc.ca/resource-gallery/Documents/Educational%20Materials/EH/FPS/Food/DairyProcessingCleaning.pdf
10. https://www.researchgate.net/publication/271254246_Cleaning-In-Place_CIP_System_in_Dairy_Plant-_Review