Dairy Engineering

Module 2. Bottle & cans washing and CIP cleaning equipment

Lesson 7
CIP AND DESIGNING OF SYSTEM

7.1 Introduction

Cleaning of dairy equipment and its sanitation are of utmost importance in dairy industry. Cleaning-in-Place (CIP) involves circulation or recirculation of appropriate water rinses and chemical cleaning and sanitizing solutions through plants and equipment which is maintained in the assembled state, such that all contaminated contact surfaces cleaned to acceptably high and consistently reproducible standards. It involves use of hotter, stronger and more soil aggressive chemical solution than manual cleaning. Filters and similar equipment should be taken out during CIP cleaning to prevent their damage.

For effective Cleaning the following aspects are important:

i. Design of plant, material used and ancillary equipment should be suitable for CIP cleaning.

ii. Cleaning procedure to be adopted depending on soil type, detergent type, concentration, temperature, contact time, type of surface.

iii. CIP cycle must effectively and automatically controlled with minimum of intervention, or unauthorized alteration

iv. Supervision is important although high degree of automation is available.

The favourable effect of increased temperature in cleaning may be attributed to:

i) Loosening of bond between soil and the surface, and increase in wetting.

ii) Greater turbulence because of decreased viscosity

iii) Increased solubilisation of more soluble constituents of soil e.g. lactose, mineral

iv) Increased chemical reaction rate which greatly increases the cleaning

It is a general observation that the minimum temperature should be about 3 - 5°C higher than the melting point of fat. The maximum temperature will depend upon the temperature at which the protein in the system is denatured.

The turbulence due to velocity of detergent has also a bearing on the cleaning efficiency. A velocity of 1.5 m/s is satisfactory.

The hardness of water must be below 50 – 60 ppm for effective cleaning. Presence of > 3 ppm of Iron and > 0.2 ppm of Manganese in water may even stain the surface. Hard water employed in cleaning leads to sludge or scale formation, which reduces the rate of heat transfer, clogs up jets, and leads to wearing of moving parts. Cleaning becomes difficult at above 200 ppm hardness.

7.2 Types of CIP Cleaning

Depending on the situation and scale, there are two types of CIP cleaning systems. They are single use and re-use systems. Use and throw of the cleaning solutions as single use system is not much in use. Now there are combined systems using advantages of both single use and reuse systems also.

7.2.1 Single use system

It is for cleaning one process circuit at a time with all liquids drained after use. This is generally called De-centralized system of CIP cleaning.

They are for small units close to the equipment to be cleaned. For example this type is used in HTST pasteurizer.

A Typical cycle has

i) 3 Pre- rinses of 20 sec. with gap of 40 sec to remove gross soil contamination.

ii) Cleaning detergent of certain temperature for 10 to 12 min.

iii) Rinse with warm water for 5 min.

iv) Rinse with acid solution, pH about 4.5 to 5.0, for 3 min.

v)Two rinses with cold water.

7.2.1.1 Cleaning media for cold milk equipment

i) Alkaline cleaning media 0.1-0.2% concentration

ii) Surface active and anti – foaming agents are added (up to 0.08%)

iii) Liquid chlorine sanitizing agent is also added up to 50 to 100 ppm

7.2.2 Re – Use CIP system

In this system, which is mostly Centralized Cleaning system, the cleaning solutions like acid, alkali are reused by circulation from tanks storing these solutions. The concentration and temperatures of the solutions is maintained in these tanks. Due to pre – rinses, detergents are not polluted much.

The following cleaning stages used in succession are possible and are used in practice depending on the nature of the soiling matter:

W →C→W

W→C→W→A→W

W→A→W→C→W

W→A→W→C→W→A→W

C= Caustic rinse; A= acid rinse; W= water rinse; water pre-rinse if W at the beginning, intermediate rinse if in the middle and final rinse if at the end.

An acid rinse can be omitted if there is no milk stone deposited, such as in can washing and storage tank cleaning. The position of the acid rinse in the sequence depends on the position of the milk stone, i.e. whether it is above, below or in the middle of the deposit.

For cleaning with acids based on Nitric acid, the concentrations should not exceed 5%. Temperatures of up to 100 °C and contact times of up to 1 hour are not hazardous. Temperatures of over 80 °C should not be used with nitric acid to prevent attack on gaskets.

At times, discolouration of surface (yellow, brown, dark blue) may occur at higher temperatures with alkaline as well as with acid cleaning, but this does not indicate that corrosion has taken place.

7.3 Automation of CIP Cleaning

As the operation of CIP cleaning is inherently hazardous and not without danger of leaking and causing harm to men and material, its operation is automated in most of the dairy plants. The tanks and fittings are shown in (Fig. 7.1)

Fig. 7.2 Automation of CIP cleaning

The sequence and timing of pumping of solutions are controlled by the PLC controller, which can be programmed. The sequence of cleaning solutions, the time of circulation can be chosen in the program. The operation is possible because of pneumatic valves both at inlet and outlet of the tanks. PHE is used for maintaining the temperatures of the cleaning solutions. The levels and concentration in each tank are sensed, filling up and concentration is maintained automatically, through controlled flow of concentrated cleaning solution, from a separate tank. The method of checking the concentration of cleaning solution is either by periodic sampling of the solution and testing in laboratory, or checking electrical conductivity of the solution on line.

Further, the CIP system must have sufficient pressure to be effective while cleaning the equipment. If two or three tanks are being cleaned, in addition to the pressure, the temperature loss also will be there. Hence, a PHE must also be provided to maintain the temperature to the required level. The hook up of the CIP system to the cleaning circuit of the equipment is shown fig 7.1. A CIP system may be of one or more cleaning circuits. Using a two cleaning circuit CIP system, two sections of a dairy processing plant can be cleaned simultaneously at same time.