Thursday, April 21, 2011

Introduction to CIP and sanitation

Cleaning and sanitisation of process plant is one
of the most critical aspects of food processing to
ensure the health and safety of the consumer. Proper
cleaning is essential for the production of high quality
food products especially those with extended shelf
Cleaning-in-Place (CIP) is now a very common
practice in many dairy, processed food, beverage and
brewery plant replacing manual strip down, cleaning
and rebuilding of process systems. The primary
commercial advantage is a substantial reduction in
the time that the plant is out of production and the
ability to utilise more aggressive cleaning chemicals
in a contained environment which cannot be safely
handled with manual cleaning.
The definition of CIP is given in the 1990 edition
of the Society of Dairy Technology manual “CIP:
Cleaning in Place” as:
“The cleaning of complete items of plant or pipeline
circuits without dismantling or opening of the
equipment, and with little or no manual involvement
on the part of the operator. The process involves
the jetting or spraying of surfaces or circulation of
cleaning solutions through the plant under conditions
of increased turbulence and flow velocity.”
CIP is not simply the provision of a CIP bulk unit
but the integrated process and hygienic design of
the complete process. A CIP system will consist
of vessels for preparation and storage of cleaning
chemicals, pumps and valves for circulation of the
CIP chemicals throughout the plant, instrumentation
to monitor the cleaning process and vessels to
recover the chemicals.
Although CIP systems are usually fully automated,
the process is often a combination of manual actions
and automatic sequencing. This applies especially
to operations within a process plant where different
types and/or concentrations of cleaning chemicals
are utilised. For example, a membrane filtration system
with polymeric membranes would be damaged if
exposed to sodium hydroxide and nitric acid solutions
routinely used in most centralised CIP operations.
In the most simple application, CIP solutions can be
used once (single-use CIP) and then discarded to
drain, but this is very expensive in cleaning chemicals,
water use and effluent costs. Such operation is not
environmentally friendly and can only be justified if it
is essential to apply a single use system to prevent
microbiological cross-contamination of different
areas of the process plant. It is more usual to recover
cleaning solutions in a recovery tank and restore the
original concentration of the cleaning fluid, and then
to re-use the recovered solution. Such systems will
need to be monitored for the build-up of residual soils
and the cleaning chemicals replenished as necessary.
In some situations, membrane filtration technology can
be used to filter soil from cleaning solutions to enable
a further extension of useful life.
Although not always recognised as such, CIP is a
methodology to remove product residues from a
process plant. It is not a means of eliminating microorganisms
from the system. This is the role of the
post CIP sanitisation or sterilisation process using
either chemical sanitisers or the application of heat to
destroy micro-organisms.

Design for cleanability
The design of the process plant must conform to all
documented hygienic design criteria. It is not usually
possible to apply a CIP system to a process plant that
was not designed for CIP in the first place.
Such hygienic design criteria have been extensively
documented by the European Standard EN
1672-2 (2005), the European Hygienic Design and
Engineering Group (EHEDG) and also by such
bodies as the United States 3A authority.
The materials of construction of the entire process
plant must be resistant to the food and cleaning
chemicals to be applied, be non-toxic, smooth, nonporous
and free from crevices.
Materials of construction
The most common construction materials are
austenitic stainless steels such as AISI 304, 316
and 316L that display good resistance to corrosion
in most environments except those containing high
chloride content, especially under acidic conditions.
Products with high chloride contents require special
metals such as titanium or alloys such as Hastelloy.
Often forgotten are the elastomers used for seals and
gaskets that are necessary to seal various metal parts
of a process plant, for example heat exchanger seals
and pipe connections, and the effect that cleaning
chemicals can have on them. The same applies
to the use of plastics in hoses, sight glasses and
pump rotors. Such elastomers and plastics must be
resistant to the food product and the conditions in
which the cleaning fluids are applied. It must also be
demonstrated that there is no leaching of potentially
toxic components from the elastomers and plastics
Frequently used elastomers include:
• Nitrile rubber
• Nitril/butyl rubber (NBR)
• Ethylene propylene diene monomer (EPDM)
• Silicone rubber
• Fluoroelastomer (Viton)
Silicone and Viton are very effective at high
temperatures whilst it must always be remembered
that EPDM is not resistant to oils and fats. All plastics
and elastomer materials must be routinely inspected
as part of a preventative maintenance plan and
replaced at the first signs of brittleness. Brittleness
causes a reduction of elasticity and eventual failure of
the ability to safely contain process fluids.
Surface finish
A smooth surface is generally considered to be
easier to clean, while rougher surfaces require a
longer cleaning time due to deposit present in the
pits. A surface roughness of no greater than 0.8Ra
(the average departure of the surface profile from the
calculated centreline) and expressed in μm is required
by both the EHEDG and the US 3A authority.
Permanent welds are always preferred to
dismountable pipe couplings from a hygiene
perspective. Dismountable pipe couplings should only
be used when it is necessary to access a particular
part of the plant for maintenance.
Considerable attention is needed to the quality of
the welds and it is usual to qualify plant welders for
their ability to execute smooth and continuous welds.
In many situations, a proportion of the welds will be
inspected using X-ray techniques upon completion of
plant construction.
Rough welds can harbour product soils and are
difficult to clean.
Welds can be made automatically using orbital
welders or manually but in both instances the internal
surfaces must be purged with an inert gas such
as tungsten (TIG – tungsten inert gas) to avoid
contamination of the weld with air that might result in
a porous weld.
A typical welding fault is to attempt to weld two
pipelines together of different diameters. The diameter
of the smaller pipe must always be expanded to
match that of the larger pipe.
Dismountable pipe couplings
There are a variety of proven hygienic dismountable
pipe couplings available, including:
• DIN 11851
• ISS (International Sanitary Standard) or IDF
(International Dairy Federation)
• Clamp (to BS 4825-3)
• SMS (Swedish Metric Standard)
A final type, RJT, is not suitable for pasteurisation
or sterilisation systems due to the formation of a
crevice in the joint area, but is favoured on manual
swing bends at flow plates due to a wide dimensional
It is vital that all dismountable pipe couplings are
regularly inspected for leaks. It is equally vital that
the joints are not over-tightened as this can cause
irreversible compression and damage to the gaskets.
A common error is to combine metric and imperial
fittings on process plant resulting in a step in the tube
wall at the joint.

Other design features
Additional essential design considerations include the
following aspects:
• Adequate draining (sloping pipework, eccentric
reducers, correctly designed tank bottoms, and good
pipework support). The process plant should drain
to avoid microbiological growth and also to avoid
potential corrosion. Residues of product and/or cleaning
fluids can become further concentrated in a heated
environment. This applies especially to chloride solutions
where a level in excess of 50 mg/litre can become
highly corrosive. In the event that a plant cannot be fully
drained, it is preferable to leave it full of water after CIP,
possibly with the addition of a preservative
• Correct installation of instrumentation with minimal
dead space. Any transmitting fluid contained within the
instruments must be approved for food contact
• Vessels with correct internal angles/corners and no dead
areas. The welding seams of the vessels should not be
in the corners but beyond the corner (Fig. 1). Corners
should preferably have a radius in excess of 6 mm but as
an absolute minimum, 3mm
• Angles and corners of process plant should be well
radiussed to facilitate cleaning (Hasting, 2008)
• There should be good accessibility of all plant
components for ease of maintenance
Examples of poor hygienic design
The following must be avoided in order not to
compromise the hygienic integrity of the process
• Dead legs in pipelines due to poor valve arrangements
• Dead legs due to the branch not being in the direction
of flow as in the case of poorly installed temperature or
instrument probes
• Pressure gauges not being on cut back tees
• The use of concentric reducers which prevent the line
being drained or leave air pockets in the pipework.
• Pipework being looped over walkways
• Pumps being installed with the outlet wrongly positioned.
• Badly designed shaft seals and bearings. Wherever
possible, bearings should be mounted outside of the
product area to avoid contamination
Fouling of process plant
The processing of any food product results in fouling
of the process plant by the build-up of soil debris
on the surfaces - especially on those at which the
product is heated. Deposits can also form from the
water used to flush the plant.
When designing a CIP system, the following
information is necessary:
• Type of soil
• Amount of soil
• Condition of soil
The main soil types are:
• Fats (animal, vegetable, mineral)
• Proteins (numerous build-up from amino acids)
• Carbohydrates (sugars such as glucose and fructose,
and polysaccharides such as cellulose, starches and
• Mineral Salts (normally calcium salts)
For soil to be removed, it has to be soluble. Many of
the above soils are not water-soluble and therefore
require the use of other cleaning solutions.
Water soluble deposits include:
• Sugars and some salts