Procedures & Guidelines
Guideline for assessing the appropriate cleaning
intervals for Tetra Therm Aseptic Sterilisers
FSQ-588012-0101
Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Table of contents
Introduction.............................................................................3
Cleaning-efficiency depends on several factors...................................3
Checklist for determining cleaning intervals ..........................................3
Some commonly encountered terms .....................................................4
Aseptic Intermediate Cleaning ...............................................................4
Final Cleaning In Place............................................................................5
Records.....................................................................................................6
Tubular Heat Exchangers (TTA Flex, TTA Primo) ..........7
General guidelines ...................................................................................7
Practical approach...................................................................................8
Plate Heat Exchangers (TTA Maxi) ....................................9
General guidelines ...................................................................................9
Practical approach................................................................................ 10
Direct steam injection (TTA VTIS, TTA PLUS ll) ............11
General guidelines ................................................................................ 11
Practical approach................................................................................ 12
Appendix................................................................................13
Checklists............................................................................................... 13
FSQ-588012-101
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Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Introduction
Cleaning-efficiency depends on several factors
Factor
Possible effect
Quality of raw product (air content,
microbial enzymes, undissolved
ingredients, salt content)
Stability
Type and configuration of equipment
Running time restriction
Type of product
Type of deposits (protein / fat / minerals)
Running time before cleaning
Thickness of deposits
Cleaning solution additives
Type of alkaline and acid
Concentration of circulating media
Hardness of water
Cleaning time
Cleaning result
Cleaning temperature
Cleaning liquid flow rates
Because of all these factors it is not possible to state precisely how long a UHT plant can be run
before it is necessary to clean.
The configuration of the processing equipment will also influence the type of cleaning problems
encountered.
Checklist for determining cleaning intervals
The following guidelines will help to establish the optimum running time and when ‘Aseptic
Intermediate’ (AIC) and ‘Final Cleaning In Place’ (Final CIP) should be carried out. It should be
noted that it takes time to find the optimum production-cycle and it requires the co-operation of a
motivated team. The exercise will have to be repeated until desired result has been achieved.
However the benefits will be:
• An increased running time (and therefore a better ratio of production to down time)
• Easier production planning
• A reduced risk of producing defective product
• Increased life time of equipment (especially valid for PHE)
• Decreased consumption of detergents (due to decreased frequency of cleaning)
The checklists found in the appendix will assist you in determining the production hours between
cleaning (AIC / Final CIP).
FSQ-588012-101
Page 3 of 15
Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Some commonly encountered terms
The common name for deposits in a product pipe as a result of the differential heating is
‘fouling’.
The heat differential will be the result of the difference of temperature between the heating
medium and the product being processed. This is usually referred to as ‘Delta-temperature’
( ∆-t).
The pressure differential between two points in the process is usually referred to as ‘Deltapressure’ ( ∆-p).
Aseptic Intermediate Cleaning
An aseptic intermediate clean (AIC) is carried out under production conditions i.e. production
temperature, flow and pressures are maintained during AIC.
The product is purged out with water and this warm rinse is typically followed by a 20 minute
alkali step. The AIC is then completed by a warm rinse.
A typical example of the aseptic intermediate cleaning steps are as follows,
although times and other parameters will depend on the particular
installation and verification of the cleaning effectiveness.
Step
Medium
Warm Pre-rinse
Water
Alkali Cleaning
NaOH
Water
Warm rinse
Time
Temperature
measured in the
holding-cell
Temperature
measured at
the return
5 min
(reaching prod. temp.)
~ 137 ºC
~ 40 ºC
1.5% - 2,5 % ∗
20 min
~ 137 ºC
~ 70 oC
To electrical
conductivity of
supply water
10 min
~ 137 ºC
Concentratio
n
~ 40 ºC
∗ Reference should be made to specialist supplier’s recommendation.
Pure or formulated detergents may be used
Note!
• It is not recommended to carry out more than two (2) Aseptic Intermediate
Cleaning cycles within the planned production time
• Normally AIC is not carried out with acid. This is because the aggressive
nature of the acid at these elevated temperatures will effect the plant
material
FSQ-588012-101
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Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Final Cleaning In Place
Depending on the kind of soil every step of a cleaning operation has an optimum operating
temperature. In general, for cold surfaces, alkali and acid cleaning are performed at 60-80ºC.
However, in UHT-process equipment, cleaning is performed at a higher temperature than
traditional cleaning. Typically the alkali clean will be approx. 137 ºC and the acid clean
approx. 105 ºC, measured in the holding-cell.
The product is purged out with water and this warm rinse is typically followed by a 50 minute
alkali step. After that another warm rinse typically followed by a 30 minute acid step. The
Final CIP is then completed by a warm rinse plus a final rinse at ambient temperature.
A typical example of the final cleaning steps are as follows, although times
and other parameters will depend on the particular installation and
verification of the cleaning effectiveness.
Step
Medium
Concentratio
n
Time
Temperature
measured in the
holding-cell
Temperature
measured at
the return
5 min
(reaching prod. temp.)
~ 137 ºC
~ 40 ºC
~ 70 oC
Warm Pre-rinse
Water
Alkali Cleaning
NaOH
1.5% - 2,5 % *
50 min
~ 137 ºC
5 min
~ 105 ºC
Warm rinse
Water
To electrical
conductivity of
supply water
Acid Cleaning
HNO3
1-1,5 % *
30 min
~ 105 ºC
~ 105 ºC
Water
To electrical
conductivity of
supply water
5 min
Warm rinse
Final rinse
Water
~ 40 ºC
~ 60 ºC
~ 40 ºC
10 min
Ambient
∗ Reference should be made to specialist supplier’s recommendation. Pure or
formulated detergents may be used
FSQ-588012-101
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Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Records
A Production record is to be filled in by the equipment operator. It shall be completed at
least every hour during production.
The reporting interval shall be shorter if the raw product quality is poor and the production
record shall contain all applicable production and cleaning parameters.
A Laboratory record is important to track problems due to dirty equipment. This record
shall include information on raw material and finished product quality.
The purpose of these records is to be able to trace the effects of the relationship between
production activities and the product attributes.
FSQ-588012-101
Page 6 of 15
Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Tubular Heat Exchangers (TTA Flex, TTA Primo)
Fouling will occur in:
• The protein stabilisation section where product is usually heated to between
• 85 °C – 100 °C
• In the final heater section where the temperature is at its highest
• In the pre-cooling section where the temperature starts high and is decreased from say,137
°C to 80 °C
The thickening of the deposit is indicated by an increasing ∆t between the temperature at the
inlet to the holding cell on product side and temperature at the inlet to heater on hot water side.
These two are normally indicated by TT 44 (Product temperature) and TT 9 (hot water
temperature).
As the thickness of the deposit increases the more difficult it is for the heat in the heating
medium to transfer to the product. The temperature of the hot water has therefore to increase
to provide enough heat for the product temperature to reach it’s set point, indicated by TT 44.
The thickening of the deposit is also indicated by an increasing pressure (normally indicated by
PI 3) before the heating section.
This is because the cross sectional area of product pipe decreases as the fouling occurs.
The product flow will remain unchanged but the velocity will increase.
The result of this is that there will be a decreased holding time in the
holding cell.
General guidelines
It is important to note that different filled products have different fouling
characteristics during processing. This will result in different cleaning
interval requirements. All tests should be made using a standard set-up, e.g.
product, hot water flow, equipment configuration etc.
An acceptable ∆-t can be 5 °C – 10 °C higher than the ∆-t for clean equipment.
For example if the temperature at the start of production at TT 44 is 137oC and at TT 9 it
is141°C then a rise to say, 146 – 151°C at TT 9 can be accepted before cleaning is
considered necessary
The Pressure difference is dependant on capacity (a low capacity gives a low pressure drop).
A pressure gauge with a low reading span makes reading easier for low pressure drops/low
capacities (0-10/25 bars).
An acceptable ∆-p can be 0,5 – 5 bar higher than the ∆-p for clean equipment.
For example if the pressure at the start of production is 5 bar at PI 3,
an acceptable rise would be to 5,5 – 10 bar at PI 3 before cleaning is considered necessary
FSQ-588012-101
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Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Practical approach
A practical approach to achieve optimum production/cleaning time for
sterilisers equipped with tubular heaters.
• The operator should complete a production record at regular, short intervals.
• When the ∆-t and the pressure reach their critical levels and it is time to clean, the
equipment should be stopped.
• Open the pipe from outlet of the heating section to holding cell
• Measure and record the thickness of the deposits
• Re-assemble the pipe and run the CIP.
• Record CIP parameters during the clean –Temperatures, chemical concentrations, time for
each step and flow rates
• After the CIP, re-open, the outlet pipe from the heating section.
• Measure and record cleaning result.
It should be noted that it may also be difficult to clean the protein stabilisation section and the
first part of cooler after the holding cell. These should be checked in a similar manner.
If the cleaning result is satisfactory then increase the set point for critical values of ∆-t and
pressure for next production. This will effectively increase the production time before the next
clean.
After the next production repeat the assessment process as described above.
Product quality has a significant impact on the running times and it is only
possible to increase production time if the product quality is in control and
is consistent.
FSQ-588012-101
Page 8 of 15
Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Plate Heat Exchangers (TTA Maxi)
This equipment is sensitive to fouling in the final heating section where the temperature is high.
The thickness of deposits is indicated by an increasing ∆-p (pressure difference) between the
product before and after the heating section. The pressure is normally indicated by PI 3.
This happens because the distance between plates decreases as fouling takes place. The
product flow will remain unchanged but the velocity will increase.
The result of this is that there will be a decreased holding time in the
holding cell.
General guidelines
It is important to note that different filled products have different fouling
characteristics during processing. This will result in different cleaning
interval requirements. All tests should be made using a standard set-up, e.g.
product, hot water flow, equipment configuration etc.
The Pressure difference is dependant on capacity (a low capacity gives a low pressure drop).
As a guide a maximum of 1.5 bar difference would indicate that the plant is ready for cleaning.
FSQ-588012-101
Page 9 of 15
Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Practical approach
A practical approach to achieve optimum production/cleaning time for
sterilisers equipped with plate heaters.
• The operator should complete a production record at regular, short intervals.
• When the pressure reaches its critical level and it is time to clean, the equipment should be
stopped.
• Open the pipe from the outlet of the heating section to holding cell. It may be necessary to
open the complete heating section.
• Measure and record the thickness of the deposits
• Re-assemble the equipment and run the CIP.
• Record CIP parameters during the clean –Temperatures, chemical concentrations, time for
each step and flow rates
• After the CIP, re-open, the plate heat exchanger
• Measure and record cleaning result.
Note!
There is risk associated with opening PHE in terms of damage to gaskets
and plates. This should only be done if considered to be absolutely
necessary.
A comparison of pressures and temperatures between different
productions can be made at start of production.
If the cleaning result is satisfactory then increase the set point for the critical value of pressure
for the next production. This will effectively increase the production time before the next clean.
After the next production repeat the assessment process as described above.
Product quality has a significant impact on the running times and it is only
possible to increase production time if the product quality is in control and
is consistent.
FSQ-588012-101
Page 10 of 15
Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Direct steam injection (TTA VTIS, TTA PLUS ll)
This equipment is sensitive to fouling in the final heating section where the temperature is high.
An increasing opening of the steam valve indicates the thickness of deposits.
This occurs because of fouling on the steam-injector, the temperature-transmitter
(TT 44), and constant pressure valve (V.30).
The opening of the steam valve is indicated directly on the valve and, if applicable, on
operators display.
As fouling takes place, the product flow will remain unchanged but the velocity will increase.
The result of this is that there will be a decreased holding time in the
holding cell.
General guidelines
It is important to note that different filled products have different fouling
characteristics during processing. This will result in different cleaning
interval requirements. All tests should be made using a standard set-up, e.g.
product, hot water flow, equipment configuration etc.
Use the steam valve as the indicator for the commencement of cleaning. An
acceptable maximum opening of the steam valve is 75% before cleaning
needs to be started.
FSQ-588012-101
Page 11 of 15
Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Practical approach
A practical approach to achieve optimum production/cleaning time for
sterilisers equipped with steam injection.
• The operator should complete a production record at regular, short intervals.
• When the steam valve reaches its critical level and it is time to clean, the equipment should
be stopped.
• Open the pipe from the outlet of the heating section to holding cell. Check for fouling of the
steam injector. Measure and record the thickness of the deposits
• Re-assemble the equipment and run the CIP.
• Record CIP parameters during the clean –Temperatures, chemical concentrations, time for
each step and flow rates
• After the CIP re-open the equipment
• Measure and record cleaning result.
If the cleaning result is satisfactory then increase set point for critical values for opening of the
steam valve for next production. This will effectively increase the production time before the
next clean. After the next production repeat the assessment process as described above.
Product quality has a significant impact on the running times and it is only
possible to increase production time if the product quality is in control and
is consistent.
FSQ-588012-101
Page 12 of 15
Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
Appendix
Checklists
FSQ-588012-101
Page 13 of 15
Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
FSQ-588012-101
Page 14 of 15
Guideline for assessing the appropriate cleaning intervals
for Tetra Therm Aseptic sterilisers
FSQ-588012-101
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