Thinking ahead - Controlling hygienic tank cleaning

Thinking Ahead
Controlling hygienic
tank cleaning
Using hygienic sensors to monitor tank cleaning
Article by Orsolya Sørensen, Alfa Laval Product Portfolio Manager,
Tank Instrumentation, Covers & Accessories and
Jens Andersen, Alfa Laval Product Portfolio Manager, Tank Cleaning
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Thinking Ahead
Controlling hygienic tank cleaning
Using hygienic sensors to monitor tank cleaning
Tank cleaning is a time-honoured tradition essential for producing high-quality foodstuffs
and beverages. Technological advances in tank cleaning have raised the standards
for food and beverage processing dramatically; the most drastic changes have
occurred within the last 50 years. To ensure the highest standards of hygiene, more
rigorous standards and tougher regulations are now in place not only for the tank
itself but for tank cleaning equipment.
The improvements to hygiene standards/guidelines are a direct result of equipment
users’ demand as well as support garnered through organisations, such as the European
Hygienic Engineering & Design Group (EHEDG), which share the common aim of
promoting hygiene during food and beverage handling, processing and packaging.
The guidelines put forth for hygienic design of food and beverage process equipment
essentially put all equipment manu-facturers on a level playing field by establishing
minimum standards for equipment quality.
With all equipment being equal, it stands to reason that proper control of the tank
cleaning process is the primary way to differentiate equipment based upon the level of
cleaning effi-ciency achieved. The objective: to get accurate, reliable and repeatable
tank cleaning results after the completion of each production cycle whether continuous
process or batch process is used.
There are several ways to achieve the desired tank cleaning results by controlling the
tank cleaning process. However, it is important to understand the process of tank
cleaning, the various tank cleaning methods and the product contained in the tank
before determining the best method of control to achieve optimal cleaning efficiency.
Traditional tank cleaning
There are various parameters that contribute to
effective tank cleaning. These are perhaps best
described by the “Sinner Circle,” which was
developed by chemical engineer Herbert Sinner
to illustrate how to obtain good cleaning results.1
Sinner defined four critical parameters that may
be combined in numerous ways and applied to
virtually any cleaning task, whether in a pipe, on a
floor or in a tank. The parameters are time, action
(or flow of cleaning fluid), chemistry and temperature, or TACT for short. All four parameters are
important to secure optimal cleaning efficiency;
however, how they are combined is decisive in
achieving optimal cleaning efficiency.
Controlling hygienic tank cleaning.
Using hygienic sensors to monitor tank cleaning.
Figure 1. The Sinner circle illustrating the
cleaning parameters of TACT
Action (flow)
Herbert Sinner defined four critical parameters – time, action (or
flow of cleaning fluid), chemistry and temperature, or TACT for short
– which are important to secure optimal cleaning efficiency.
Thinking Ahead
Applying effective chemicals or cleaning agents
and optimum temperature to the surface to be
cleaned weakens the bond between the soil and
the surface to a point where the available force
(or action) can remove the soil.2 The unknown
factor is the available force. Time, chemical
concentration and temperature can be controlled.
What is the available force, and how is it applied
to the surface? This depends upon the method
and technology used to distribute the cleaning
media in the tank.
One of the oldest methods of tank cleaning, the
“fill, boil and dump” approachFigure
is still used
1. by many
industries for various applications. This simple
cleaning method involves filling the tank with water
and chemicals and heating its contents to the required temperature. The mixture is kept in the tank
for a sufficient amount of time in order to allow the
chemicals and temperature to react with the soil.
The tank is then emptied or its contents “dumped.”
This is a very expensive and time-consuming
cleaning method, and the amount of force applied
is minimal.
a fixed location in the tank onto a fixed location
on the tank surface. As the jets hit the tank surface, they create an area, or footprint, where the
impact force and shear stress are active. After
impact, the jets change to cascades of cleaning
fluid, which run down the sides of the tank,
creating a free-falling film. This free-falling film
generates shear stress on the interior walls of the
tank in an uneven pattern. Here time, chemistry
and heat are the decisive factors that determine
when the tank is clean. The wall shear stress of
the free-falling film is fixed in the range of 1 to 5 Pa,
which is comparable to that present in a pipe in
which the liquid is pumped at a speed of 1.5 m/s.3
Image 1. Alfa Laval Static Spray Ball
The static spray ball gently
sprays cleaning fluid onto
the tank walls, enabling the
fluid to fall freely down the
tank wall and provide uneven cleaning coverage.
Tank cleaning
Tank cleaning-in-place (tank CIP) is a commonly
used cleaning method, which applies force to
the tank surface for the removal of soil without
having to open and enter the tank. There are three
different types of technologies used for cleaning
the tank interior:
1. Static spray ball (static cleaning device)
2. Rotary spray head (dynamic cleaning device)
3. Rotary jet head (dynamic cleaning device)
Whilst these technologies are not new, they have
been developed and improved over the past
50 years. The technological advances to dynamic
cleaning devices in recent years are noteworthy.
Some of the technologies have been tested and
approved by the EHEDG; however, most of the
equipment available today does not have approval
from any standards organisation.
All three technologies apply force to the tank surface in different ways and with different degrees
of efficiency. The level of efficiency for the different
technologies is determined by the impact force
(mechanical force) and the shear stress, which
significantly differ among the technologies.
Rotary spray head
Unlike the static spray ball, the rotary spray head
is a dynamic cleaning device. The flow of the
cleaning media released from the spray head
causes the spray head to rotate. This creates a
swirling movement, which enables the fluid to hit
the tank surface with an impact force that is higher
than the impact force of the static spray ball.
Image 2. Alfa Laval SaniMidget SB
Rotary Spray Head
The rotary spray head has a
higher impact force and higher
wall shear stress compared
to the static spray ball.
This reduces cleaning time.
Static spray ball
The static spray ball continuously disperses
cleaning fluid through each perforated hole from
Controlling hygienic tank cleaning.
Using hygienic sensors to monitor tank cleaning.
Thinking Ahead
The pulsating force and impact created provide a
com­bination of shear stress and variable falling
film of cleaning fluid that covers all the internal
surfaces of the tank. Compared to the static spray
ball, the rotary spray head reduces the amount of
cleaning time required to achieve the desired cleaning results.
Rotary jet head
Of the three automated tank CIP technologies,
the rotary jet head is by far the most effective
because it creates the highest impact force and
highest shear stress. The rotary jet head has
between one and four cleaning nozzles, each of
which disperses cleaning fluid through a well-­
defined jet. The rotary jet head rotates at a
predefined speed to provide a full 360-degree
indexed cleaning pattern. This ensures that the
tank surfaces are thoroughly covered after a
specified interval of time, which is dictated by the
actual configuration of the machine.
The impact force and subsequent coverage create a footprint that is much larger and wall shear
stress that is much higher than that provided by
a static spray ball or rotary spray head. The magnitude of the wall shear stress in a rotary jet head
footprint is approximately 104 Pa and decreases
to about 7.5 Pa at approximately 150 mm from
the impact centre.4 This is significantly higher
than the wall shear stress of between 1 and 5 Pa
in the free-falling film created by a static spray ball.
Image 3. Alfa Laval SaniJet 25 Rotary
Jet Head
The rotary jet head is by far the
most effective tank cleaning
technology available today.
Controlling hygienic tank cleaning.
Using hygienic sensors to monitor tank cleaning.
Wall shear stress in footprint creating by
impinging jet
Figure 2. Wall shear stress in footprint
creating by impinging jet
The wall shear stress in the footprint of an impinging jet from
a rotary jet head, with water temperature at 20°C and
pressure at 5 bar, is shown.
The water from each jet of the rotary jet head
creates a moving footprint on the tank walls in
the 360-degree indexed cleaning pattern (as
mentioned above). Because of the significantly
higher impact force of the rotary jet head and
subsequent increase in wall shear stress, it is
possible to predict the required cleaning time
more accurately when using a rotary jet head.
Chemistry and temperature are therefore no
longer the most important parameters for cleaning efficiency. Instead, impact force is the most
important parameter. By increasing the impact
force on the tank surface, it is possible to reduce
the time, flow, chemistry and temperature.
In other words, when using a rotary jet head in most
tank CIP scenarios, it is possible to cut the cleaning
time required, reduce the amount of cleaning fluids
used and realise energy savings because the
cleaning fluids do not need to be heated to high
temperatures in order to achieve optimal tank
cleaning efficiency.
Thinking Ahead
Figure 3 and 4. Comparison of static spray ball and rotary jet head tank cleaning machines
The Sinner circle for tank cleaning with a static spray ball
The Sinner circle for tank cleaning with a rotary jet head
Action (flow)
Figure 3.
Figure 4.
Adding the impact force of the rotary jet head results in savings in cleaning time, cleaning fluids and energy due to reduced
pump running time and less heating time of the tank cleaning fluid.
Reduction of cleaning time by 70% and
fluids consumption by 90%
Recent studiesv) indicate how the impact force
from a rotary jet head is distributed in the impact
area on the tank wall. The highest impact force
occurs at the centre of the impact area; it then
decreases by approximately 50% at a distance
of 40 mm from the centre of the impact area.
It is also important to note that the rotary jet head
effectively cleans high-viscosity products, such
as sticky foodstuffs, using water at ambient
temperature in just 15 seconds after the jets hit
the tank wall.
In many applications, using a rotary jet head can
reduce cleaning time by 50–70% and cut water
and cleaning fluid consumption by up to 90%
compared to using the conventional fill-boil-dump
method or static spray ball technology. It is then
easy to understand why so many companies are
considering new ways to optimise tank cleaning
performance yet maintain control over the tank
CIP process.
the rotary jet head clean-ing fluids hit the tank
surface with the right impact force in order to
ensure optimal cleaning efficiency.
The question remains: Is this possible to ensure
validation of the rotation and impact?
Real-time tank cleaning process control
Process control depends upon reliable real-time
in-line measurements using electronic sensors,
such as the Rotacheck sensor, to monitor and
verify the performance of a rotary jet head and
tank CIP. Various such devices are readily available today. However, it is important to consider
the response time of the device as well as its
ability to register the actual pressure at which
the jets hit the tank surface.
Because uptime is key to production efficiency,
optimising tank cleaning performance is critical.
It is therefore important to optimise the tank cleaning
process to ensure repeatable tank cleaning performance in the shortest possible amount of time.
Fast response time is critical in order to measure
the impact force of the water jets accurately and
reliably. A response time of less than 25 milli­
seconds is considered necessary to register a
jet hit against the tank wall; however, the response
time for many sensors is too long, exceeding the
25 milliseconds and therefore providing inaccurate measurements. Consequently, the sensors
do not measure the entire actual impact and
therefore do not properly validate the effect of
the jet. Furthermore, the signal remains “high”
on the sensor even after the jet has passed and
is no longer hitting the sensor.
Although tank CIP systems are automated,
these systems still require monitoring and control.
Temperature, flow rate and chemical concentration are among the critical tank cleaning process
control parameters. However, the performance of
the CIP system itself also requires monitoring and
control to ensure that it operates according to
design parameters. Take the rotary jet head tank
cleaning system, for instance; it is important that
Registering the actual pressure at which the jet
hits the tank surface is equally important. This
pressure is the actual impact force that the jet
exerts upon the tank surface. If the amount of
pressure applied to the tank surface decreases,
then the impact force decreases as well. As
the pressure decreases so too does cleaning
efficiency, which consequently causes the
cleaning time to increase.
Ways to control the tank cleaning process
Controlling hygienic tank cleaning.
Using hygienic sensors to monitor tank cleaning.
Thinking Ahead
Output unit (Pressure)
Output unit (Pressure)
Figure 5. Jet impact profile of
a rotary jet head when50passing a Rotacheck sensor
Output unit (Pressure)
Impact pressure at 5 bar
Impact pressure
at 5(Seconds)
Time (Seconds)
Impact pressure at 3 bar
Impact pressure at 3 bar
Typical pressure characteristics of a water
jet from a rotary jet head at 3 bar and at 5
bar are shown.
Impact pressure at 5 bar
Time (Seconds)
Impact pressure at 3 bar
Selection of the right CIP process control
Tank CIP process control optimises plant
hygiene and efficiency
Choosing the right system to monitor and control
tank CIP processes can be challenging. It is
important to define your objectives for monitoring
and control and to understand the available
options and advantages.
There are several ways to achieve optimal cleaning
efficiency for your tanks. To determine the right
tank cleaning method for your process, it is important to define the cleaning criteria, understand
the options available and consider the level of
cleaning efficiency and process control required.
Selecting the right tank cleaning method puts you
in control of the tank cleaning process and ensures
that the best cleaning results can be achieved in
terms of accuracy, reliability and repeatability.
Basic sensors transmit a simple logic signal to
the plant’s surface readout (SRO) system or control system, which indicates all jet hits and verifies
the operation of the rotary jet head. In addition to
signal transmission, some sensors also have a
clear visual light signal that is visible to operators
on the plant floor. Most are easy to install anywhere on the tank, even on a pressurised tank.
Advanced sensors, such as the Rotacheck+
version which carries the 3-A symbol and has
been EHEDG-certified, offer the same advantages
as basic sensors but include built-in intelligence.
This consists of a teach-in function where the
sensor records and stores the unique and actual
cleaning pattern for any individual tank cleaning
machine based upon its initial cleaning cycle,
which has the design parameters (set point) intact.
Every time a CIP process is initiated thereafter,
the sensor will compare the actual measurements
to the recorded pattern (set point). Operators are
immediately alerted during tank CIP if there is
any deviation from the initially recorded time,
pressure or registration of jet hits. This enables
operators to act immediately to remedy the
situation, thereby reducing the risk of losing
valuable production time.
Whilst manual tank cleaning may seem sufficient
for some processes, there are advantages to
switching to an automated system; these include
cleaning consistency, reduced labour costs and
increased production time. Enhancing automated
tank cleaning processes also has its advantages
in terms of less downtime, higher energy savings
and reduced water and cleaning fluid consumption.
Image 4. Alfa Laval Rotacheck
Electronic verification tools,
such as the Rotacheck
and Rotacheck+ sensors,
validate the proper function
of rotary jet heads during
tank cleaning.
With the right CIP sensor in place, the process is
under control.
Controlling hygienic tank cleaning.
Using hygienic sensors to monitor tank cleaning.
Thinking Ahead
The addition of CIP process control systems,
whether basic or advanced sensors, can further
enhance cleaning efficiency. The only way to validate that an automated tank cleaning system is
working effectively is to monitor and verify its
With so much invested in hygienic food and
beverage production, the additional expense of
hygienic sensors to validate the tank cleaning
process seems a small price to pay to ensure the
optimal cleaning efficiency.
Sinner, H. 1959. The Sinner Circle “TACT.” Sinner’s Cleaning Philosophy. Henkel.
Jensen, B.B.B. 2009. “May the Force (and Flow) Be With You: Importance of Flow in CIP.”
Food Safety Maga-zine, 14:28-31, 51.
Jensen, B.B.B. et al. 2011-2012. “Tank Cleaning Technology: Innovative application
to improve clean-in-place (CIP).” EHEDG Yearbook 2011-2012, pp. 26-30.
Therkelsen, Niels Vegger. 2012. “Methods to determine the efficiency of nozzles for cleaning process
equipment,” Master’s Thesis. BioCentrum-DTU, Technical University of Denmark.
Controlling hygienic tank cleaning.
Using hygienic sensors to monitor tank cleaning.
About Alfa Laval
Alfa Laval is a leading global provider of specialized
products and engineered solutions that help
customers heat, cool, separate and transport
products such as oil, water, chemicals, beverages,
foodstuffs, starch and pharmaceuticals.
Alfa Laval’s worldwide organization of 16,300
employees works closely with customers in
100 countries. Listed on the NASDAQ OMX
Nordic Exchange, Alfa Laval posted annual sales
of approximately 3,45 BEUR in 2013.
Orsolya Sørensen
Product Portfolio Manager, Tank Instrumentation, Covers & Accessories
Orsolya Sørensen is product portfolio manager for instrumenta­tion,
tank accessories, manways and tank covers at Alfa Laval Denmark.
She is passionate about innovative products and her expertise is
to bring industry solutions based on customer insights to market.
She had a wide variety of roles over a period of 14 years from
strategy consulting to business development manager. Her
qualifications include M.Sc. in Electrical Engineering from Budapest
University of Technology and MBA from Stockholm School of
Economics. Alfa Laval’s offering represents a full range of hygienic
instrumentation, tank equipment and tank cleaning technologies.
Contact: [email protected]
Jens Andersen
Product Portfolio Manager, Tank Cleaning
Jens Andersen has 8 years of experience in Tank Equipment
with Alfa Laval Denmark and has been portfolio manager for
Service and recently for the whole range of Alfa Laval Tank
Cleaning Machines for hygienic industries. He has managed and
commissioned large-scale industry installations, has extensive
experience in trouble shooting and training of staff at large global
companies. He has a deep understanding and knowledge of the
Cleaning-in-Place (CIP) process and has utilized his knowledge
and experience to consult large global players in hygienic
industries on how to optimize their CIP processes.
Contact: [email protected]
ESE02286EN 0115
How to contact Alfa Laval
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