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Cleaning / CIP (Cleaning In Place) / SIP (Sterilization in Place)

Article index
 Two steps
 Plant design
 CIP process
 SIP process
Cleaning a food or beverage plant demands specific properties of the equipment and the installation.

Two steps

All liquids and solids, as well as build up, need to removed from the system. Only if the plant is really clean a successful sterilization can be done.

Sterilization is always the second step. If there are any microorganisms left alive in the system, the sterilization kills them. This step does not replace the cleaning.

Cleaning and sterilization can be done using different technologies. Traditional cleaning is manual and mechanical. In an automated food plant, state-of- the-art technology is Cleaning In Place (CIP). The plant does not need to be disassembled, the process stays closed.

To ensure that the parameters for time, temperature, flow and concentration are maintained, most CIP plants are fully automated. This ensures the best possible result from this process.

Plant design

A CIP plant consists of tanks, measuring and dosing devices. To adjust the temperature, a heat exchanger is integrated and typically two pumps (supply and return) are installed.

This basic design is used in nearly all food plants. The size and number of the tanks used vary due to several reasons. The basic CIP plants are single use systems. The water and detergent are not recovered, and go to the drain after use.

A standard CIP plant is built from one tank with post and pre rinse water (cold), a hot caustic tank and an acid tank. The liquid is pumped to the process lines with the feed pump and back to the CIP system with the return pump. The speed is 1.5 m/s. Sometimes the plant is cleaned counter the production direction. Other tanks for hot and cold caustic or acid can be added to increase the flexibility of the system.

Usually, the caustic and sometimes other agents, like acid and additives, are stored in concentrate tanks. The tanks need special attention to protect the environment. In several countries laws are set to ensure this. The chemicals need to be dosed very accuratately.

CIP process

A standard CIP process may look like this:

Step 1: Pre rinsing

As much as possible dirt should be flushed out of the system. To avoid build up due to crystallization or burning, the temperature is chosen close to the production temperature.

This is typically around room temperature or just slightly warm.

Step 2: Heating up the system

The system is heated up slowly, again to avoid degeneration or burning of fat or proteins in the pipe. It can be done with water or with caustics.

Step 3: Caustic cleaning

The caustic is pumped through the system with a temperature of around 90°C for a defined time. Parameters for a successful cleaning are:
  • Temperature
  • Velocity
  • Concentration
  • Time

The entire process is controlled via these parameter. If one of these parameters is not correct anymore, the cleaning stops and needs to be started again. The temperature is kept high by the heat exchanging system. To keep the concentration around 2.0%, concentrated caustics is dosed. Hot caustic cleaning is used to remove fat, proteins and organic build up. The high temperature supports the caustic effect, like the dosed additives do. The cleaning soluble needs to keep the solved dirt suspended. The concentration is usually measured with an inductive conductivity sensor and flow speed with a magnetic flow meter.

Step 4: Cooling down the system and rinse out the caustic

The plant is cooled down for sterilization or the next production. The caustic and solved dirt is flushed out of the system. The water can be stored and used for pre-rinse for the next cleaning.

Step 5: A complete cleaning cycle ends up with a cold acid flushing.

A light acid deletes the organic build up and stones. It neutralizes any remaining caustics that might have stuck in the system. Additionally, it kills microorganisms that might have stuck somewhere in the system.

SIP process

Sometimes cleaning is followed by a sterilization, SIP. Usually the same equipment is used similar to CIP. With SIP the aim is not to clean the system, but to kill microorganisms that may have survived the CIP. For the sterilization, hot water, steam or chemicals are used. Saturated steams with temperatures up to 140°C are strengthened by the use of disinfection agents (mostly acid, approximately 0,2%). After this step, the plant is left, for the night, weekend, or just to give temperature and acid the chance to work. Cooling down, we need to be aware of vacuum. Sometimes a hot system is directly filled up with the cold product. This means very large temperature changes.

Instrumentation is the heart of the CIP/SIP process; not only for process control, but also for the documentation that the cleaning was successful. Temperature is the most important parameter. Inductive measurement of the concentration and the flow measurement are the additional parameters that need to be documented.

To save the pumps from damage due to dry running, vibronic switches are used in front of both pumps. To run the plant in safe condition, the continuous level measurement ensures that an adequate supply of cleaning agent is available for the next steps.

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User comments

2009-07-07 10:18:36

Name: joost
was redelijk volledig, waar ik wel geen antwoord op heb is de snelheid waarmee het reinigingswater moet circuleren.

2009-07-08 10:54:11

Name: Editor
De snelheid wordt bepaald door de maximale grenslaag die gewenst is. De dikte van een grenslaag = 2Dh/ f(Re). Door deze grenslaag heen moeten door diffusie de micro-organismen van de wand komen en in de vloeistof wegspoelen. Uit testen is gebleken dat daarvoor in een 50 mm diameter leiding een stroomsnelheid van 1,5 m/s nodig is, maar voor andere afmetingen en vormen gelden andere snelheden. Voor meer informatie zou u contact kunnen opnemen met bv. Burggraaf & Partners.

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Cleaning a food or beverage plant demands specific properties of the equipment and the installation. Two steps All liquids and solids, as well as build up, need to removed from the system. Only if the plant is really clean a successful... read full description

Click for additional information about CIP - SIP