Insights on Cleaning in Place (CIP) System

The Cleaning in Place cleaning principle has existed for around 50 years and is one of the standard methods for cleaning process-technical systems. It is mainly used in applications where critical hygiene requirements exist, such as in the food and beverage industry or pharmaceuticals. CIP refers to the use of a mix of chemicals, heat and water to clean machinery, vessels or pipe work without dismantling plant. The process can be one shot, where everything goes to drain, or recovery, which recycles most of the liquid. Overall, CIP can be a very efficient way of cleaning. 

Cleaning in Place (CIP) systems are designed to automate your cleaning process and efficiently clean and disinfect your enclosed processing equipment. Combined effects of chemicals, turbulence, energy and heat help remove solid, debris and microorganisms from pipework without manual cleaning.

Achieving the optimum cleaning results in the shortest cleaning window requires a combination of the right chemical regime and ensuring your CIP system is correctly configured.

The principles of CIP can be applied to any industry and plant where hygiene is critical; and the process is usually an integral part of any automated plant. Increasing Health and Safety legislation is set to make CIP more common, which is a good thing because a shiny surface on the outside of plant is no guarantee of cleanliness on the inside.

Even though CIP technology has come a long way from the first manually operated systems of the 1950s, they still rely on the same principles to clean the host system reliably. In 1959, Dr. Herbert Sinner created what is referred to as the Sinner’s Circle. Dr. Sinner was a German chemical engineer who headed the development of detergents for Henkel, the West German chemical and consumer goods company. His circle described the cleaning process as a combination of four components: time, chemistry, mechanical action and temperature.

    Fig. Sinner's Circle

Dr. Sinner used his circle to describe how different amounts of each component could affect the final cleanliness. In a CIP system, this results in a custom-tailored concentration of chemistry at a specific temperature which is circulated for a set amount of time. The mechanical action in this case is the velocity at which the cleaning solution is circulated as well as the pressure coming from any spray balls. Some systems will use higher temperatures and lower pressures. Others will use a high pressure flow to ensure a proper clean. The configuration of the plant and the nature of the contamination to be cleaned are key factors in determining the proper method. Depending on the product and the operator, a CIP cleaning is run between batches or it is run when the production system is switching over to a different product. Typically, a cleaning consists of a pre-rinse, a heated chemical cleaning, an intermediate rinse followed by a final rinse and then a sanitizing rinse.

CIP method highly depends on type of soil or food residue to be cleaned. Every industry has their own type of soil depending upon the product being processed. And hence it is recommended to have CIP Process to be designed accordingly. Selection of chemicals and their strength, chemistry of product and its interaction with different solutions, time of interaction of chemicals with process line etc. are to be considered while designing the CIP line. Soil also differ in nature; it can either be simple water soluble or can be water insoluble. Water soluble one’s are easy to clean as simple flush of water can dissolve them. Water insoluble soils are hard to tackle as they are again divided into organic and inorganic soils. Organic ones include fats, oils, grease, proteins, starch, and carbohydrates. Inorganic soils include minerals, salt deposits, millstones etc.

CIP is principally concerned with soil removal: soil being anything that should not be present in a clean vessel. Soil can cause tainting and can often be smelt. It can be visible (scale, foreign bodies,) or invisible in the form of bacteria, such as E Coli, or Yeast spores. The time needed to remove soil is at least 15 minutes using a suitable chemical (strength dependent on chemical supplier and product) at temperatures above 50 degrees C, but no greater than 75 degrees C because there is no advantage to be gained above this temperature.

CIP performs in two ways: – Single use cleaning CIP and recovery CIP. Single use cleaning is for that industries where the line gets way too dirty and chemicals once used can’t be further used due to high soil contamination in the chemical solution, but it is to be noted that they can be highly costly as new chemicals are to be used every time and they can have high environmental load as it is disposed and drained after every CIP Cycle. In Recovery CIP the process line is not so filthy and hence the chemicals can be collected and reused, though the equipment for recovering cleaning solution is more expensive.

Construction and components of the CIP systems

Important components of a CIP system are the measuring and dosing technology, the concentrate and user tanks as well as the heat exchanger. Acids and alkalis such as nitric acid and caustic soda are contained in several concentrate tanks of the system. The exact concentration of the user solution is adjusted in the user tanks by mixing with water. The caustic tank is equipped with a heat exchanger which ensures the desired temperature and thus the required viscosity of the caustic solution. Further components of the cleaning system are tanks for cleaning water and, depending on the application, tanks for ultrapure water or disinfectants such as peracetic acid. Another component of CIP System is  for spraying cleaning solutions into the equipment: spray balls.

CIP: Parameters to be considered

• CIP effectiveness depends totally on the correct functioning of the 5 T’s.

1. Titration (1.5%): It is always important to select cchemical concentration in the supply tanks and in the circuits is in accordance to our need. It should be able to remove any deposits and residue of soil in the process equipment’s. It generally lies in the range of 0.5-2% and the optimal one being 1.5%.
2. Turbulence (1.5m/s): Flow velocity in all parts of the system should be sufficient to cause turbulent flow. This should be around 1.5-2 meters per second, below this laminar flow will occur which will not yield effective cleaning.
3. Temperature (~70°C): Temperature of the cleaning solution and water at the beginning & end of the circuit is important to consider. Temperature impacts on the rate of chemical reaction. Typical temperatures can be around 85 Deg. C for cleaning solution but for water it should not exceed 70 Deg. C
4. Time (15 min): Duration of each step of the CIP procedure and the total CIP time can be one of the important factor that shall be determining the cleaning is achieved or not. The standard time span should be 15 minutes.
5. Technology (Design): Total design of the complete line including all circuits to and from the chemical and water tanks should be proper. Even fault in the equipment design can result in cleaning of the line. Any corners or buildup site in the equipment will not full fill the CIP.

Cleaning Agents

Commonly used chemicals for soil removal include Caustic Soda, Phosphoric and Nitric acids, Sodium Hypochlorite (Hypo) and Peracetic Acid (PAA). Caustic Soda is an alkali typically used at 0.5% - 2% volume. It reacts with the fats in the soil and softens it for removal. One downside is that Caustic Soda is not effective for removing scaling. In addition, sequestriants are often added to keep soiling in solution.

Phosphoric and Nitric Acids are used in detergent formulations for scale removal, often at lower temperatures than Caustic. These acids must be used with care as they can attack valve and pump seals. They are often used in dairies for one week in every 6 weeks to remove milk scale, and can be used after commissioning to remove installation debris.

Sodium Hypochlorite (Hypo) offers the advantage of a very low cost. It is used primarily for disinfection because its ability for soil removal is poor. The active ingredient of Hypo is Chlorine (Bleach). This can corrode Stainless Steel in high concentrations and will attack seals and personnel. It will also taint if not rinsed out; and is dangerous if mixed with acid, forming Chlorine gas, which is poisonous.

PAA is an equilibrium mixture of acetic acid and hydrogen peroxide. It is a powerful oxidising agent with an oxidation capacity higher than sodium hypochlorite and chlorine dioxide, and is comparable to the oxidative capacity of ozone. PAA at 75 mg/L is reported to successfully kill 100% of a 10(7) cell/ml yeast or bacterial population in 30- seconds.

Design Considerations for CIP Systems

When designing a CIP system, there are several design elements to keep in mind to ensure the constructed system fully performs its intended function. Some of the key design considerations include:

Capacity: The CIP system must be adequately sized to provide the flow and pressure needed to remove residue, reduce cycle times, and rinse effectively.

Utilities: The processing facility must have the utilities required to operate the CIP system.

Space requirements: Local codes and maintenance practices dictate the space needed for both portable and stationary CIP systems.

Drainage. Proper drainage is critical to cleaning operations. Drain utilities must be able to handle high discharge temperatures.

Processing time: The amount of time that a CIP system takes for its operations determines how many individual units are required to meet demand.

Temperature. If proteins are present inside the process systems, pre-rinse operations should occur at ambient temperature to remove as much protein as possible without denaturation.

Solution concentration and type. CIP systems employ different cleaning solutions and concentrations for different purposes. For example:

Caustic—also referred to as caustic soda, sodium hydroxide, or NaOH—is used as a detergent in most CIP cycles. Concentrations range between 0.5–2.0%.

Nitric acid is used for scale removal and pH level stabilization after a caustic wash cycle. It’s generally employed at concentrations of 0.5%.

Hypochlorite solutions are typically used as sanitizers.

Equipment surface characteristics: The internal finish of a CIP system can help or hinder the buildup of proteins and other contaminants within the system. For example, mechanical polishing operations create rougher surfaces than electropolishing operations, resulting in a higher risk of material adherence. When choosing a finish, it’s essential to choose one that minimizes the amount of mechanical and chemical damage experienced during cleaning operations.

The CIP process

Depending on the product produced and the degree of contamination of the production system, the complete cleaning process consists of different steps. In the first step, the CIP system rinses with water and removes the coarse soiling. Cleaning is then carried out with an alkaline concentrate. Rinsing with water removes the cleaning lye. With the help of acid, lime deposits can be removed in the next step. The acid is also rinsed out with water afterwards. Disinfectant solution is used in the following process step to kill microorganisms. Rinsing with water removes the disinfectant from the system.

CIP is a closed system where recirculating cleaning solution is applied (often with nozzles) that cleans, rinses and sanitises equipment. The CIP system is usually automatically controlled and the cleaning sequences are given the optimum timing for efficient cleaning of all parts of the plants.

Most CIP employs a similar set of operations, including:

• Pre-rinsing – to remove large debris and residues
• Detergent cleaning – to remove attached dirt and soiling using a caustic detergent
• Rinsing – to remove detergent and dirt
• Optional acid cleaning – if required to remove scaling or alkaline residues
• Rinsing – to remove the acidic cleaning agent
• Disinfection – heat or chemical treatment to disinfect the equipment
• Final rinse – to remove all traces of chemicals and prevent contamination.

    Fig. CIP Cycle

These steps may be combined or used in different ways. For example, using detergent at high temperatures may clean and disinfect equipment at the same time, or using steam may reduce the need for chemical detergents. Depending on the design of the system, and the risk of contamination, cleaning solutions may be reused multiple times or discarded immediately. 

While the actual cleaning regime used will depend on a number of factors, including the type of product and the design of the machinery in question, in many situations it is preferable to rely on water alone (together with temperature, pressure and agitation) rather than additional cleaning chemicals which could present a contamination risk. In general, the higher temperatures and greater kinetic energy provide more efficient cleaning, but the duration of the CIP cycle will be optimised according to the properties mentioned above. In general, the higher the temperature the more effective the cleaning. The effect of temperature optimization on fats, sugars and salts is good, while on proteins it is fair. The kinetic energy equates to whether the required flow of solution in the pipework is laminar or turbulent, or somewhere in between. In a process vessel, the cleaning effect is usually created by fixed or rotating spray heads.

Before starting production, the line is sterilized using disinfectants to inhibit any microbial activity to a certain level. It is always recommended to verify and validate all the cleaning procedure.

Repeatable, reliable, and effective cleaning in a manufacturing facility are prominent characteristic of the CIP system. Various influencing parameter are to be kept in mind as well as manipulated to achieve the required quality standard in manufacturing unit. The process can be validated hence it proves its authenticity. If proper care is taken in each stage of CIP including flow and temperature, it will provide safe environment for food manufacturing and processing owners.

 The time for rinse and wash cycles varies from five minutes to one hour. To ensure product quality, operators must use the appropriate amounts of cleaning solutions and make sure those solutions have been removed completely before the next processing run.

Where detergents are required, one of the most common is caustic soda (NaOH), although many other alkali- and acid-based chemicals are available depending on the nature of the product and residues which need to be cleaned. Alkali materials are generally more effective against proteins and fats, while acids perform better where salts need to be removed. For sugars, water remains one of the most effective cleaning mediums.

Spray Balls

Spray balls are the cleaning nozzles used for efficient cleaning of tanks, vessels and other containers of various shapes and sizes where cleaning solution cannot be reached.

Spray balls consist of a sphere of a hollow sphere of hygienic 316 stainless steel with precise hole perforating it. This forms an omnidirectional series of fluid jets as water is passed through at pressure. The jets will hit the walls of the tank, spread out and cascade downwards providing an effective cleaning action.

Spray balls are a simple device with no moving parts and hence are very reliable and required little or no maintenance. They are also cheap to purchase making them a cheap and reliable tank cleaning system that is deployed commonly in small to medium sized process vessels.

Water when confined its flow through small nozzles is pressurized and cleans surfaces effectively. Because of its sanitary design it is widely used in breweries, dairies and other food industries as well as in pharmaceutical and chemical applications where manual cleaning is not possible to avoid human caused error in cleaning and to reduce the downtime of the process.

Working Principle- Spray balls have numerous small holes, perforated partially or completely on its surface. It facilitates the efficient cleaning of process equipment by drenching the interior surfaces of the vessels with hot water and cleaning solutions at various velocities, thus making them suitable for CIP. Spray balls offer basic rinsing of the tank’s internal surface where each hole acts as a divergent spray which have whirling effect for removing soil in a turbulent way. Spray balls ensure that the process of cleaning is highly effective and it can be designed and automated to allow for maximum coverage. Several factors are need to be considered during cleaning process like coverage of the spray balls.

Types of Spray Balls

Based on the mode of operation spray balls may be static or rotary types:

Static Spray Ball: This particular spray ball is a permanent static mount, designed to direct multiple high-velocity jets against the tank wall which do not require more fluid. They are used primarily for rinsing tanks. They are inexpensive to purchase and are very robust.

Rotary Spray Ball: The cleaning fluid drives the spray head by means of specially positioned nozzles. The rapidly repeated impacts remove the soil and rinses it from tank surfaces. This results in optimum cleaning efficiency at low pressure in small to large sized tanks.

CIP and the requirements for pump technology

CIP cleaning processes place high demands on the pump technology used. The quality and performance of the rinsing pump are critical factors for the success of the cleaning process. The problems with the use of CIP are often due to a poorly functioning return system. This results in an increased use of cleaning agents as well as heat and working time. In addition, there is more waste to be disposed of.

To avoid this, it must be ensured that the return system returns the cleaning solutions quickly and efficiently. A poorly working or incorrectly set rinsing pump does not meet this requirement. It causes a backwater of the cleaning solution and a poor cleaning result. Only a reliable and powerful rinsing pump that is precisely matched to the desired flow rate ensures that fresh cleaning agent always reaches the surfaces to be cleaned and effectively removes the dirt.

The fluid velocity is of great importance for the cleaning result. For optimum results, the specified values must be neither exceeded nor undershot. If high-pressure cleaning heads are used, the pump technology used must provide the required working pressure.

The Bottom Line

The objective for most process environments is to maximize quality production time and minimize other activities and costs. The bigger and more difficult the cleaning job and the more frequent the cleaning cycle, the more cost effective CIP can be.

Some of the main economic benefits of installing a CIP system:

• More Production Time: Less production time lost to cleaning, more time spent making product.
• Product Quality: Reliable and repeatable cleaning leads to sustainable product quality and consistency, fewer product recalls, and higher brand confidence.
• Employee Efficiency: More labor time spent on productive, profitable activities.
• Utility Savings: Water and energy usage is reduced through repeatable cycle control.
• Lower Water Treatment Costs: The amount of effluent going to drain is greatly reduced.
• Lower maintenance costs – Properly cleaned equipment will potentially run longer between maintenance periods, which translates to more time producing product.