Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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.0005 formation of deposits that may adversely affect

the operation of equipment.

0006 changeover to a different product;

0007 production shutdown over an extended period.

An example of a microbiological requirement for

cleaning would be a food process line where the

microbiological quality of the final product decreases

during production until the point where shutdown

and cleaning is required.

0008 An example of a process-related requirement for

open plant cleaning would be a freezer in which ice

build-up on the evaporator surfaces takes place, even-

tually resulting in a failure to maintain the desired air

temperature and flow velocity. The effect of this

would be to reduce the capacity of the freezer and

eventually reach a point at which the products are not

cooled to the required temperature, thus requiring

production to be terminated. A process-related re-

quirement for cleaning of a closed system would be

a pasteurizer, in which fouling of the heat transfer

surfaces takes place, eventually resulting in both

physical blockage of the heat exchanger and failure

to maintain the desired pasteurizing temperature. The

microbiological effect of the pasteurization process

would therefore be reduced below that required

for product safety, thus requiring production to be

terminated.

0009 There are a variety of mechanisms by which sur-

faces may become fouled, as shown in Table 1,and

the nature and composition of the resultant soil can

therefore also vary widely. Failure to clean effectively

may have serious implications in terms of product

quality and storage characteristics as well as process

operation and control. Figure 1 shows how a properly

cleaned process line can operate for a much longer

period of time before the microbiological quality of

the product becomes unacceptable, and the line must

be shut down and cleaned.

0010Clean equipment leaves microorganisms exposed

to disinfection agents such as hot water, steam, and

chemical disinfectants. Microbiological methods of

evaluation may be used to validate the condition of

the system after cleaning, and several countries have

recommended hygiene standards based on colony

counts per unit surface area. In addition to standard

microbiological techniques (contact plates, swabs) a

variety of more direct methods may be used to assess

the cleanliness and/or hygienic status of surfaces.

Scope and Philosophy of Cleaning Operations

0011Cleaning operations within any manufacturing envir-

onment are likely to involve a variety of surfaces,

materials of construction, and cleanliness require-

ments. Patterns of cleaning will also vary consider-

ably according to the environment, equipment, and

products. An initial classification is used to differen-

tiate between the types of surface that are to be

cleaned, product contact and nonproduct contact,

which may be defined as:

Concentration of

microorganisms/soil

Maximum acceptable

concentration

Residual level after

effective cleaning

Start

production

Start

production

Cleaning

necessary

Poor

cleaning

Time

Extension of

production time due

to effective cleaning

fig0001 Figure 1 Influence of cleaning efficiency on available production time.

tbl0001Table 1 Major fouling mechanisms

1. Chemical reaction Deposits formed at the surface by

chemical reactions in which the

construction material itself is not

a reactant

2. Crystallization Deposition/formation of crystals on a

surface

3. Particulate Accumulation of solid particles from the

fluid stream on the surface

4. Biological Deposition and growth of microorganisms

on a surface

5. Corrosion Corrosion of the surface itself which may

in turn promote the attachment of other

soil

6. Solidification Solidification of fluid components on a

surface

1386 CLEANING PROCEDURES IN THE FACTORY/Overall Approach

0012 Product contact surfaces These include all equip-

ment surfaces that intentionally or unintentionally

(e.g., resulting from splashing) come into contact

with the product, or from which product or conden-

sate may drain, drop, or be drawn into the main

product or product container. This includes surfaces

that may indirectly cross-contaminate product con-

tact surfaces or containers.

0013 Nonproduct contact surfaces These include all other

exposed surfaces. These may include surfaces associ-

ated with equipment such as support structures,

control panels, and external surfaces. They also

include surfaces related to the manufacturing envir-

onment.

0014 It is important to appreciate the importance of the

manufacturing environment as a potential source of

pathogens and/or spoilage organisms. Drains, drain

channels, walls, floors, and roofs near air intakes

have all been implicated as significant sources of

microorganisms.

0015 In certain situations, environmental cleaning can

only be carried out during a production shut-down

period and therefore can be difficult and costly. Be-

cause of this and the trend towards extended produc-

tion runs within the food industry, intermediate

cleaning is being considered more frequently. An

example of this is cleaning a line, while production

continues on an adjacent line in the same area.

0016 A further subdivision of cleaning operations is

whether the process is carried out dry or wet.

Dry cleaning

0017 Dry cleaning methods are primarily used where the

products are hygroscopic or where water can react to

form hard deposits that are difficult to remove. The

principal safety risk is that failure to control moisture

can permit the growth of pathogens, e.g., Salmonella

spp., in the food processing environment. Environ-

ments typically dry-cleaned include plants producing

flour, cocoa, dry milk products, dry soup and snack

mixes, and dry infant formulae.

0018 Dry cleaning is essentially the mechanical removal

of soils using sweeping, brushing, wiping, and

vacuuming. Vacuuming is in principle a desirable

system for removing dust and dirt. Disinfection

following dry cleaning may pose difficulties, although

alcohol-based disinfectants can be appliedand allowed

to dry off before equipment is reassembled.

0019 Additional wet cleaning in a dry area needs great

care, and it is usually best to remove equipment or

parts requiring wet cleaning to a separate area. The

wet-cleaned parts must be throughly dried before

returning to the dry area for reassembly.

Wet Cleaning

0020Wet cleaning, as its name implies, involves the appli-

cation of fluids, usually water based, to achieve the

desired cleaning result. This can be carried out in

place (CIP), where the plant remains assembled as

for production.

0021The other alternative is to clean using open plant

cleaning (OPC). In this case, the surfaces to be

cleaned have to be made accessible to the cleaning

fluids, which may involve the use of delivery systems

to enable the operator to deliver the necessary

cleaning fluids, e.g., lances, sprays, or dismantling of

the equipment to allow the necessary access. In add-

ition, some plant components may be physically

removed from the production area and cleaned separ-

ately in a designated cleaning area. This is termed

cleaning out of place (COP).

0022More complex process equipment may involve a

combination of OPC and CIP; for example, a pump

may be cleaned in place along with the rest of the line,

but if it is known that CIP is not fully effective, it may

be stripped down and cleaned manually before pro-

duction restarts.

0023Manufacturing environments may require a com-

bination of dry and wet cleaning. Dry cleaning using

scrapers, shovels, or brushes may be more appropri-

ate, particularly immediately after production, to

remove quantities of gross soil and thus reduce the

challenge to the wet cleaning process.

Factors Affecting Cleaning of Equipment

0024The equipment to be cleaned may be considered as a

set of unit components that may vary widely in terms

of volume, configuration, and geometry. There are

several interrelated factors that have a direct bearing

on the effectiveness and ease of cleaning process plant

(Figure 2). A key point to appreciate is that a system of

poor mechanical or process design may be unclean-

able, irrespective of the cleaning process imposed on it.

It is therefore essential that consideration of cleaning

should be integrated into the mechanical and process

design at an early stage rather than a final process to be

incorporated into an already fully specified plant.

0025The factors that can contribute to the efficiency of

a cleaning process are mechanical, thermal and chem-

ical activity – and the time for these to work. The

cleaning process is invariably a combination of these

factors, and different cleaning processes involve a

different balance of these factors, which has implica-

tions for the type of detergent to be used. For

example, a cleaning process carried out at a low

temperature with little mechanical activity would

require a more powerful detergent than one carried

CLEANING PROCEDURES IN THE FACTORY/Overall Approach 1387

out at a high temperature with a large amount of

agitation.

Plant-cleaning Options

Open Plant Cleaning (OPC)

0026 The function of OPC process is to clean and, where

necessary, disinfect all surfaces to an acceptably high

and consistently reproducible standard. A process

plant cleaned in this way is disassembled and/or

moved from its normal location for cleaning. This

also applies to plant that is opened up to make it

more accessible for cleaning manually or using some

form of delivery system such as a hose.

0027 The cleaning process consists of a number of stages:

0028 Preparation for cleaning Prior to cleaning, all food

and packaging material has to be removed from the

area, including pallets, crates, bins, etc. All food ma-

terial that can be reused further should be stored

away from the process area and packaging material

returned to the packaging material store. Only if all

this material is removed, will thorough and complete

cleaning be possible.

0029 Dismantle equipment Equipment should be dis-

mantled in order to expose the surfaces to be cleaned.

Small items or components may be removed at this

stage for cleaning in a dedicated wash area.

0030 Gross soil removal Before application of the deter-

gent, the gross soil has to be removed from the sur-

face. Detergent has little effect on soil layers several

millimeters in thickness or on large lumps.

0031 Gross soil removal can be achieved by different

methods as scraping, brushing, or spraying, but it is

not necessary for the line to be 100% visibly clean

after this step. It should be borne in mind that collect-

ing gross soil by scraping may be more effective than

flushing it to drain by pressure rinsing in terms of

reducing the loading and cost of effluent treatment.

Pressure rinsing could take more time and cause extra

problems of drain blockage.

0032Detergent application Detergent is applied to the

surfaces using mechanical aids to assist soil removal

including brushes or high- or low-pressure water

hoses as appropriate. The selection of detergent

should be done in conjunction with the supplier.

0033Rinsing Rinsing of the detergent residues and soil

can best be done under the same conditions as the

prerinse. The extra demand for this rinse is that, after

rinsing, the equipment should be 100% visibly clean.

The rinse water should be of potable quality

0034Disinfection In many applications, food contact

surfaces have to be disinfected after cleaning. The

choice of the correct disinfectant depends on a

number of factors, including:

0035type of microorganisms involved;

0036construction material of the equipment;

0037effluent system;

0038application of final rinse after disinfection.

0039Final Rinse It depends on the local situation as to

whether a final rinse after disinfection is necessary. In

some countries, adequate draining after disinfection

with approved disinfectants at approved concentra-

tions is sufficient. If a final rinse is required, the water

must be of potable quality.

0040Drying Liquids must be completely removed by

draining and/or drying, before the next startup can

be done.

0041Clearing Away the Cleaning Tools After cleaning,

the tools must be cleaned and (optionally) disinfected

Plant design

Materials, surface finish

Equipment design

Equipment installation

Geometry, presence of voids

Cleaning process

Detergent type & concentration

Temperature/flowrate

Water hardness

Process design

Quantity/type of soil

Age/moisture of soil

Composition of soil

fig0002 Figure 2 Factors affecting process plant cleaning.

1388 CLEANING PROCEDURES IN THE FACTORY/Overall Approach

and stored in a designated area (according to local

rules). It is helpful to have color coded cleaning tools

for special applications/areas (for example, black-

bristled brushes for drain cleaning).

Cleaning In-place (CIP)

0042 CIP may be defined as the circulation of chemicals

and/or water through the plant that remains assem-

bled as for production, such that all product contact

surfaces are cleaned and, where necessary, disinfected

to an acceptably high and consistently reproducible

standard.

0043 This process consists of up to three main stages:

0044 Product recovery/rinsing – removal of bulk prod-

uct from the system immediately after production,

or cleaning residues such as used detergents and

disinfectants after cleaning.

0045 Cleaning – removal of soil from product contact

surfaces.

0046 Disinfection – further reduction of relevant micro-

organisms in the plant by chemical or thermal

means, to achieve the desired hygiene standards

within the plant.

Hence, CIP may be taken to mean processes including

some or all of the above stages.

0047 Product recovery should be employed whenever

possible to reduce product losses and decrease the ef-

fluent chemical oxygen demand (COD). Product re-

covery may be achieved by simple purging with water

or, with a viscous product, more effectively by pigging.

0048 For disinfection, there are several options depending

on the microbiological requirements, construction

materials, and plant design:

0049 pasteurization, a thermal process that will inacti-

vate most vegetative organisms, including patho-

gens, but not heat-resistant bacterial spores;

0050 sterilization, a more severe thermal process that

destroys all microorganisms, including heat-resist-

ant bacterial spores;

0051 chemical disinfection, which, depending on the

chemical and the temperature used, may kill all or

only some of the microorganisms present.

It is possible to clean a plant by applying a simple ‘use

and dump’ procedure, whether or not making use of

additional equipment for preparing and pumping

cleaning liquids. However, considerable savings in

running costs may be achieved by installing an appro-

priate CIP system, which enables recovery and reuse

of rinse water and detergents and a more efficient

utilization of energy.

Economic and Environmental Implications

of Cleaning

Economic Implications of Cleaning

0052Cleaning costs are often closely associated with the

cost of the cleaning chemicals alone and less attention

paid to the other costs of the process, namely:

0053steam;

0054electricity;

0055water;

0056effluent;

0057labor;

0058plant downtime.

It is difficult to be specific as regards the cost of

cleaning, as this will depend on the type of plant

being cleaned, the cleaning process used, and the

relative cost of services, which will vary widely from

site to site. It is, however, generally accepted that in

open plant cleaning, the major cost factors are plant

downtime and labor. Where the plant downtime cost

is not included in the costing, the labor cost may be

60–85% of the total.

0059Although manual cleaning is widely accepted in

some industries as the only way of achieving reason-

able standards of cleanliness where vessel and pipe-

line cleaning is required, its inherent disadvantages

made the eventual implementation of CIP techniques

inevitable, and their use has confirmed the significant

benefits anticipated. CIP may incur additional capital

costs for equipment, but this can be minimized for

new lines by consideration of CIP during the design

stage.

0060Improved hygiene. Consistent, reproducible

cleaning schedules may be carried out and moni-

tored with a corresponding improvement in plant

cleaning performance and subsequent product

quality.

0061Cost savings. Optimal use of water, chemicals, and

steam results in lower cleaning costs.

0062Improved plant utilization and reduced plant

downtime. Tanks and pipelines can be cleaned as

soon as they are empty and refilled immediately

afterwards.

0063Reduced labor cost. A reduction in the need for

manual disassembly of equipment, coupled with

an increased use of automation leads to a dramatic

reduction in labor requirements.

0064Improved occupational safety. Less opportunity

for operators to come into contact with aggressive

chemicals.

0065Reduced effluent, minimizing volumes of waste

water. CIP systems can be used to monitor and

manage the reuse of cleaning waters and chemicals.

CLEANING PROCEDURES IN THE FACTORY/Overall Approach 1389

The cost of cleaning will depend on the plant being

cleaned, the cleaning process used, and the cost of

services, which will vary widely from site to site.

However, the additional costs incurred with manual

cleaning can be seen clearly in Figure 3, a cost break-

down of a labor-intensive manual operation and a

highly automated CIP process.

0066 The costs in Figure 3 are all shown relative to the

total cost of the single stage clean, which is taken to

be 1. The depreciation costs are very variable, and the

total costs of manual and CIP cleaning in this figure

are not the same.

0067 With a predictive costing model, it is possible to

compare the (total) cleaning costs for different

cleaning procedures and thus optimize the cleaning

process, which automatically results in water, efflu-

ent, and energy savings.

Environmental Implications of Cleaning

0068 Cleaning in the food industry will inevitably bring a

high amount of organic material into the effluent

system. In general, more than 95% of the organic

load consists of the soil, which is removed. Scraping

away gross soil and sending it to destruction, instead

of rinsing it to drain, could substantially reduce the

organic load that goes into the effluent system.

0069 Any environmental assessment of cleaning should

be considered in the context of the complete manu-

facturing operation and also include all types of

cleaning operations, both OPC and CIP. These are

likely to indicate that the majority of the biochemical

oxygen demand/chemical oxygen demand load on

the effluent plant is associated with product losses,

both during production, e.g., product leakage as

well as cleaning. The detergents used should contain

only biodegradable surface active agents and, if

possible, biodegradable sequestrants. For inorganic

materials, they should not contain fillers such as

chlorides and sulfates, which do not have any positive

effect on the cleaning. The technical information

sheet of the detergent should provide information

concerning the environmental effects of the detergent.

In addition, automatically preparing detergent solu-

tions has a cost-reducing effect, and instead of

manual preparation, it prevents overdosing.

0070The most attractive way of reducing the environ-

mental implications for closed systems is product

recovery by pigging. The so called ‘pig’ is sent, by

means of compressed air or water as the driving force,

through the pipeline and expels most of the product

from the system.

Conclusions

0071All forms of cleaning and disinfection are known to

play an increasingly important role in manufacturing

in all stages of processing right up to the packaging of

the final product. Because there is a trend towards

improved hygiene standards in food manufacturing,

cleaning/disinfection forms an essential component of

such improvements.

See also: Cleaning Procedures in the Factory: Types of

Detergent; Types of Disinfectant; Modern Systems;

Factory Construction: Materials for Internal Surfaces

Further Reading

Imholte TJ (1984) Engineering for Safety and Sanitation.

Crystal, MN: Technical Institute of Food Safety.

Karlsson CA-C (1999) Fouling and Cleaning of Surfaces –

The Influence of Surface Characteristics and Operating

Conditions. Lund, Sweden, Lund University.

Lelieveld HLM (2000) Hygienic design of factories and

equipment. In: The Microbiological Safety and Quality,

pp. 1656–1690. Gaithersburg, MD: Aspen.

Shapton DA and Shapton NF (eds) (1998) Principles and

Practices for the Safe Processing of Foods. Cambridge,

UK: Woodhead.

4 Chemicals

8 Steam/water

3 Electricity

11 Electricity

Labor 85

Manual CIP

13 Labor

17 Chemicals

Steam 28

31 Water

fig0003 Figure 3 Typical percentage cost breakdown for manual and CIP cleaning. (Figures are percentages of total cost, excluding

depreciation. Total costs of the manual and CIP operations are not the same.)

1390 CLEANING PROCEDURES IN THE FACTORY/Overall Approach

Wilson DI, Fryer PJ and Hasting APM (eds) (1999) Fouling

and Cleaning in Food Processing ’98. Proceedings of a

Conference at Jesus College, Cambridge. Brussels: Dir-

ectorate-General Science, Research and Development.

Modern Systems

H M J van Eijk and F A Majoor, Unilever Research

Vlaardingen, Vlaardingen, The Netherlands

Introduction

0001 In the design stage of a process line, the cleaning

requirements should already be taken into account.

A CIP-able plant should be designed in such a way

that cleaning and disinfection can take place in the

same line configuration as that during processing.

Unfortunately, in practice, this target cannot always

be reached; it is possible that some parts are not

cleanable in-place and thus require dismantling and

manual cleaning. Those parts have to be physically

separated from the system, and it should be realized

that reinstalling may result in contamination of the

cleaned process line. Implementation of a CIP system

depends on the type of process and whether the equip-

ment is suitable to be cleaned in-place.

0002 Resulting from this discussion, normally more

options can be defined. If some of those solutions are

equivalent, a detailed cost comparison should follow,

taking into account investment in equipment, running

costs, and, increasingly importantly, plant down time.

Options for central CIP systems

0003 In some cases, CIP of a plant can be done without the

addition of extra equipment. This could be appropri-

ate for small plants with only a few tanks and short

pipe runs. Cleaning liquids can be prepared in the

production equipment itself, e.g., in balance tanks of

pasteurizers. Possible disadvantages are that running

costs may be high because of losses of cleaning chem-

icals and process down time. Therefore, it should be

investigated in all cases whether possible savings in

running costs can justify the investments in additional

CIP equipment, normally consisting of extra tanks,

pumps and pipe runs.

‘Single-use’ CIP system

0004 Such a system (Figure 1) consists of one tank that is

used to prepare a certain cleaning solution at the

desired temperature. This can already be done when

the line is still in production, provided that there is a

good physical separation between the cleaning system

and the production system. After connection to the

process line, a centrifugal pump circulates the cleaning

solution through the part of the process plant that has

to be cleaned. The pipe system between tank and

pump contains a manifold through which optionally

cold or hot water or steam can be introduced into the

circuit. Prerinsing and postrinsing are once-through

operations; after passing the process equipment, the

rinse is discharged directly to drain. The cleaning

liquid may be circulated over the tank for a certain

period of time, but is also discharged to drain at the

end of the cleaning procedure.

0005The automation level of such systems can be kept

low; because of their simplicity they can be easily

operated manually. The advantage of these systems

is that time is gained during preparation of the

cleaning solution(s). The disadvantage of possibly

high running costs is still the same.

Single-use System with Partial Recovery

0006This system can be used under the same conditions as

above, but now the option of recovering fluids has

been added by the use of two buffer tanks (Figure 2).

Also, here, the detergent solution is normally dumped

after use, but when, after the prerinse, the residual

soiling is light, recovery of the cleaning solution in

one of the tanks may be considered. This may be used

one or more times for subsequent cleaning proced-

ures. When a disinfection step is required, there might

also be recovery of disinfectant in one of the buffers.

If detergent cannot be recovered, there is still the

possibility of recovering postrinse water, which can

be used for the next prerinse.

Optimal Reuse System with Maximum Recovery

(Centralized System)

0007This system contains sufficient tanks that several

fluids and solutions used in cleaning have their own

Water

Steam

Process

system

Detergent

(Disinfectant)

fig0001Figure 1 Flow diagram of a ‘single-use’ CIP system (types of

valves depending on specific local requirements).

CLEANING PROCEDURES IN THE FACTORY/Modern Systems 1391

dedicated buffer (Figure 3). In the simplest form,

there are at least two tanks; one for prerinse water

and one for detergent solution. Postrinse may be re-

covered in the prerinse tank, and the detergent can be

recovered (after a certain waiting time to prevent

dilution) in its own buffer. Extra tanks might be ne-

cessary for buffering, e.g., a disinfectant, descaling

solution or postrinse water.

0008 The benefits are clear; cleaning can start immedi-

ately after production stops, and the cleaning pro-

cedure can be executed without any interruptions.

Preparation of cleaning fluids of the right strength

and temperature can be done with separate circuits

to avoid any delay between cleaning stages. More-

over, there is a cost saving from the recovery of

water, chemicals, and energy, and, in some cases, by

the possibility to recover product (if this can be

reworked).

0009 An additional advantage is a better control over

the effluent costs. To run such systems in a safe and

efficient way, a higher level of automation is highly

preferred. This implies higher investment costs.

Partially Decentralized System

0010When, in a factory, a centralized CIP system (as de-

scribed before) is situated a long distance from the

various process systems, the efficiency of such a

system might be affected by the following factors:

0011large volume of liquid in long pipe runs, thus re-

quiring larger tanks and more energy input;

0012long time needed to purge out a liquid/replace it by

another (resulting in chemical loss);

0013when more cleaning loops are necessary, the costs

of pipe work increase dramatically.

To overcome this, a central CIP system can be

extended with satellites, which only serve one distinct

part of a process system (Figure 4). These satellites

can be rather simple, but should be able to receive the

required cleaning liquids from the central plant within

a reasonably short time, e.g., by means of a main loop

system with relatively small pipe diameters.

0014Depending on the situation, a decision can be made

on whether or not to recover liquids to be sent back to

Process

system

Detergent

Make-up

Disinfectant/

De-scaler

Make-up

Pre-

rinse

Post-

rinse

Water

Product

recovery

or waste

fig0003 Figure 3 Flow diagram of an optimal, centralized reuse CIP system with the possibility of maximum recovery (types of valves

depending on specific local requirements).

Water

Steam

Process

system

Detergent

(Disinfectant)

Disinfectant

(Pre-rinse)

fig0002 Figure 2 Flow diagram of a ‘single-use’ CIP system with partial recovery (types of valves depending on specific local requirements).

1392 CLEANING PROCEDURES IN THE FACTORY/Modern Systems

the central system. Such a system may offer particular

advantages, e.g., when preparation stages of a process

can be cleaned while, downstream, other process

equipment and filling machines are still in use. In

such cases, a centralized CIP system will require far

more safety measures (e.g., leak protected valves) or

should make partial cleaning unacceptable. Also,

parts that require more frequent cleaning could be

cleaned by satellite systems.

Logistic Aspects Affecting the Layout of the CIP

System

0015 Normally, a process plant will be cleaned at the end of

a (series of) production run(s). A logical sequence is to

start with complete removal of all loose product from

the process line by purging (optionally for recovery)

and prerinsing (to waste and/or to drain). This means

that the complete prerinse of the whole plant is done

before cleaning liquid is introduced. Usually, such a

rinsing procedure follows the same routing as the

process; starting from the introduction point of raw

materials, the process line is followed down stream

to the filling machine. Later on, the same sequence is

repeated with subsequent cleaning fluids. From a

control point of view, this is a good and simple

option, and moreover, only a few safety measures

are required. The only safety precaution necessary is

to physically separate the central CIP system immedi-

ately after the feed pump from the process system

during actual production. Another advantage is that

switching over from one stage to the next (e.g., pre-

rinse to detergent cleaning), has to take place only

once, so that any losses by mixing of liquids in the CIP

circuit are minimized. A typical example of such a

‘sequential’ system is presented in Figure 5.

0016A disadvantage of such a system is that, because of

this sequential procedure, the cleaning time might be

rather long. It can be regarded as a waste of time that

a prerinsed preparation vessel has to wait for the next

cleaning cycle because the finished product buffer still

has to be rinsed. Moreover, it is common practice to

start cleaning of an ingredient preparation depart-

ment directly after preparing the last batch. Fre-

quently, at that moment, processing and especially

filling of the product will still continue for a consider-

able time.

0017For these reasons, a process system might be split

up in individual smaller units. As mentioned previ-

ously such units should all be able to be physically

separated from the CIP system and from each other.

By doing this, the parts that are already out of pro-

duction can be immediately cleaned, resulting in a

considerable gain of time. An example of such a

‘unit cleaning’ system is presented in Figure 6. This

Detergent

Make-up

Disinfectant/

De-scaler

Make-up

Water

Buffer

Process

unit 3

Buffer

Process

unit 2

Buffer

Process

unit 1

Main CIP-system

fig0004 Figure 4 Flow diagram of a partially decentralized system with satellites (types of valves depending on specific local requirements).

CLEANING PROCEDURES IN THE FACTORY/Modern Systems 1393

may result in overlapping of cleaning cycles of various

parts of the plant, which are not compatible with each

other (e.g., one part requires detergent, another post-

rinse water). Again, this may give rise to undesired

waiting times. A solution is then to install more

cleaning circuits with feed and return pumps con-

nected to the same buffer tanks. Each of these circuits

is connected to a defined and separated part of the

process. This latter option is also the optimal practice

when parts of the process require a much higher

cleaning frequency than the total plant. To avoid an

extensive, complete safeguarding of the total plant,

such parts can be provided with their own dedicated

cleaning loop, connected to the same central CIP-

buffer tanks, with only one physical separation in

supply and return.

Systems for Open Plant Cleaning (OPC)

0018A wide range of systems are available for the delivery

of pressurized water and the application of detergents

in open plant cleaning. These systems vary in terms of

sophistication and investment. The selection will be

based on a number of factors, which can be broadly

classified on the basis of whether the operation being

carried out is a cleaning, disinfection, or rinsing step.

0019Hosing is one of the most usual ways of delivering

water, which is used as a cleaning agent. Pressure

systems are generally characterized as being either

low pressure–high volume or high pressure–low

volume.

0020Normally, for (warm) rinsing water, a ring main

system is available with tap points through the

Cleaning

Phase 5

Buffer

Ingred. 3

Mixing

Vessel

Cleaning

Phase 1

Cleaning

Phase 2

Cleaning

Phase 3

Cleaning

Phase 4

CONTAINER CONTAINER

Preparation

Ingred. 1

Preparation

Ingred. 2

Buffer

Ingred. 1

Buffer

Ingred. 2

Dosing

system

Final

process

Final

Product

buffer

fig0005 Figure 5 Typical example of a process line that is cleaned ‘sequentially’. All CIP inlets and outlets (triangles) are connected to the

same CIP circuit.

1394 CLEANING PROCEDURES IN THE FACTORY/Modern Systems

factory. If the gross soil removal is to be carried out by

pressure rinsing, warm water (50–55



C) at a pressure

of up to 20 bar is typically used. The temperature is

high enough to melt fats but not high enough to

denature proteins, which could result in burn on. A

pressure of 20 bar (with a flow of 20–30 l min

1

)is

sufficiently high to remove most of the gross soil

whilst minimizing risk of damage. The pressure is

low enough to prevent excessive aerosol formation

occurring, which could lead to microorganism-

containing aerosols being created, with the risk of

contaminating adjacent areas of the factory.

0021 Foam cleaning is a process that involves applying

detergent to a dirty surface as a foam. Provided that

the foam is stable and not too wet, it will cling to the

surface for a relatively long time (5–10 min), during

which time, physical/chemical attack can soften the

soil.

0022 The foam and loosened dirt are then rinsed away

from the surface. This is preferably done with a high-

pressurejet,providedthatthereisnodangerofspraying

electrical switchgear or similar water-sensitive equip-

ment.Inthis case, alow-pressuresprayor,occasionally,

a vacuum can be used to remove the foam.

0023Another cleaning method is gel cleaning. Gel

cleaning detergents are chemicals that are of low

viscosity as a 100% product. On dilution, however,

they gelate, and by this, they will increase the contact

time of the detergent on the soil (10–30 min for gels).

This prolonged contact time gives a much stronger

effect and therefore better cleaning results, or equal

results with rinsing at reduced pressure (5–20 bar).

Mobile Equipment

0024Detergent and disinfection can be carried out using

mobile equipment. Mobile foam or gel equipment

generally consists of a pressure vessel. The vessel

(50–100 l) is filled with detergent solution. The deter-

gent solution is forced by compressed air into a

mixing chamber and mixed with foam or gel. The

foam is applied to the surface via a hose and foam

lance provided with a vee-jet nozzle. The vee-jet

nozzle allows the application of an even and thin

foam layer. After the required contact time, the

CIP-

Supply

CIP-

Return

CIP-

Return

CIP-

Return

CIP-

Return

CIP-

Return

CIP-

Return

CIP-

Return

CIP-

Return

Buffer

Ingred. 1

Process

Vessel 1

Product

Buffer 5

Product

Buffer 4

Product

Buffer 3

Product

Buffer 2

Product

Buffer 1

Buffer

Ingred. 2

Buffer

Ingred. 3

Process

Vessel 1

Ingred. X

Product X

fig0006 Figure 6 Example of a ‘unit cleaning’ system. The various degrees of shading indicate some of the units that can be cleaned in

isolation of the rest of the plant, where production may continue during the cleaning operation. The circles indicate the places where

block-and-bleed systems are required. The individual units may be connected to different CIP circuits.

CLEANING PROCEDURES IN THE FACTORY/Modern Systems 1395