EQUIPMENT AND PROCESS VALIDATION

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EQUIPMENT AND PROCESS VALIDATION
For Batch and Continuous Ovens

• Seth Pulsfus
• Alkar Technical Development

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To meet FSIS Lethality Performance Standards

• Control and record (Appendix A)
• Cooking time ? 1min
• Cooking temperature ? 1?F
• Relative humidity ? 5
• Assure uniform heat penetration
• Probe in the coldest part of the oven

These requirements imply

• Recognize the sources of process variations
• Control these variations
• Prove (validate) process variations are under
  control

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Purpose of this presentation

• Review the sources of variation in thermal
  processes
• Equipment design
• Products loading
• Products shape
• Thermal processes
• Explain how to control thermal processes
  variations
• Describe equipment and process validation
  procedures

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OUTLINE
Equipment and Process Validation
Thermal Processes
Product Shape
Product Loading
Oven Design
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Small batch ovens,
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Large batch ovens,
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And continuous ovens
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Same basic design
Heating element
Main fan
Damper
Supply Duct
Return Duct
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Batch oven
Return ducts
Supply ducts
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4 variables control thermal processes

• Temperature (dry-bulb)
• Moisture (wet-bulb)
• Fluid velocity (air, water)
• Time

A thermal process, expressed in a cooking
schedule is a combination of some or all these 4
variables.
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Example cooking and smoking schedule
Bone-in Ham, 16-20 lbs., traditional smoke
Step Time Dry-Bulb
Wet-Bulb R.H. Dampers Smoke
1 2 3 4 5
72 --- --- 32 52
Auto Auto Closed Auto Auto
On
10 min 1.5 hr 3 hr 1 hr to 148º F core
110º F 0º F 0º F 130º F 150º F
120º F 150º F 160º F 170º F 175º F
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Dry- and wet-bulb measurement
Wet-bulb probe with wet sock
Water
Dry-bulb probe
Wet-bulb (psychometric) pan located in the
return duct
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Heat sources that generate the dry-bulb
temperature

• Direct-fired or indirect-fired gas
• Steam coil (indirect heat)
• Electric elements (indirect heat)

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Humidity sources controlling the wet-bulb
temperature

• Natural humidity
• amount of fresh air intake and hot air exhausted
• Steam
• Atomized water
• ? for dry-bulb temperatures lt 108F

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Oven components control process parameters

• Heat sources ? dry bulb temperature
• Fresh air and exhaust dampers, humidity valve ?
  wet bulb temperature
• Blower ? air velocity

The control system controls the oven components

• Heating elements
• Dampers, valves
• Blower
• Time (clock)

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Batch and continuous ovens share the same
components
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Batch oven airflow creates temperature variation

• Variation
• Top-to-bottom
• Side-to-side
• Front-to-back

How to get a uniform and balanced airflow?
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Balancing the airflow rotating dampers
Rotating damper blades
Main Fan
Return-throat opening
Air supply leg
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Oscillating air flow reduces temperature variation
Rotating Damper blades
Heating Equipment
Main Fan
Compensates top-to-bottom and side-to-side
variations
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How to adjust the breakpoint
Breakpoint
To lower the breakpoint, increase the gap between
the damper blades and the duct. To raise the
breakpoint, make the gap smaller
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To adjust front-to-back variations
Starting point for return duct balancing Return
slides adjusted so that total open area is 10
less than the area of return-throat opening.
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Preventive maintenance keeps ovens reliable
Daily checks

• Wet sock Change daily.
• Wet-bulb pan Check water flow rate and drain.
• Rotating dampers 90º out of phase and turn
  freely
• Compressed air Instrument air should be dry.

Desiccant should be blue
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Weekly Checks
Preventive maintenance keeps ovens reliable

• Calibration check Test dry- and wet-bulb probes
  against calibrated thermometer in bucket of
  hot water or in dry-block calibrator.
• Cleaning Verify that CIP in ductwork is
  working.
• Rotating dampers Check for free rotation,
  well-greased, proper chain tension, 90o
  out-of-phase.

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Monthly Checks
Preventive maintenance keeps ovens reliable

• Control system Full calibration at two
  temperatures (low and high)
• Bearings Inspect
• Steam cook valve Operating range 3 - 15
  psi
• Fresh air exhaust dampers Operating range
  3 - 9 psi
• Humidity valve Operating range 9 - 15 psi

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Quarterly Checks
Preventive maintenance keeps ovens reliable

• Lubrication
• Gas burner
• Cleaning system function
• Supply-air velocities

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OUTLINE
Equipment and Process Validation
Thermal Processes
Product Shape
Product Loading
Balance Airflow Preventive Maintenance
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Proper oven loading
Excess gap (gt 12) will create chimney effect
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Uneven product loading
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Partial load
Good !
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Partial loading of an oven
Good !
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Partial loading of an oven
Not good !
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Product carrier design affects air flow
Cross framing is located above 12
Framework blocks oven airflow
Poor Design !
Good Design !
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OUTLINE
Equipment and Process Validation
Thermal Processes
Product Shape
Even Oven Loading
Balanced Airflow Preventive Maintenance
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Product geometry affects heat transfer
L
Heat is transferred along the shortest dimension
Naturally-shaped products like bacon and bone-in
hams will inherently have more temperature
variation
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OUTLINE
Equipment and Process Validation
Thermal Processes
Uniform product size
Even Oven Loading
Balanced Airflow Preventive Maintenance
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Heat transfer in cooking processes its all
about the wet bulb temperature
TD Temperature Difference
Product Cross-section
The driving force for heat transfer is the
surface to core temperature difference
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Steam and hot water processes

• Process characteristics
• Forced convection (pumps or fans agitate the
  fluid)
• High heat transfer coefficients
• Heat transfer only
• Controlled by 2 or 3 variables
• Temperature
• Water agitation rate
• Time

? Uniform temperatures throughout the equipment
are easily achieved
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Example steam cooking programme
Molded Ham, 4x4 and 4x6
Step Time Steam temperature
1 2 3
1.0 hr 1.0 hr to 155º F core
120º F 140º F 165º F
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Forced air convection processes

• Process characteristics
• Lower heat transfer coefficients
• Simultaneous heat and mass transfers
• Controlled by 4 variables
• Dry air temperature (dry bulb temperature)
• Temperature at which water evaporates (wet bulb
  temperature)
• Air velocity
• Time

? Non saturated processes generate more
temperature variation
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Smoked Boneless Ham 4.25 diameter, fibrous
casings
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Smoked Sausage, natural casing, 32 - 34 mm,
traditional smoke
Step Time Dry-Bulb
Wet-Bulb R.H. Dampers Smoke
10 min 90 min 30 min 30 min 30 min to 158ºF
core
1 2 3 4 5 6
110º F 120º F 120º F 145º F 165º F 170º F
100º F 0º F 0º F 120º F 140º F 160º F
68 --- --- 47 50 78
Auto Auto Closed Auto Auto Auto
On On On
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Natural Casing Smoked Sausage Drying 30 minutes
Temperature
(F)
Time (hours)
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Continuous System, 3 - zone, Pork/Beef Wieners,
10/lbs
Zone Time Dry-Bulb
Wet-Bulb R.H. Dampers
25 34 67
1 2 3
18 min 18 min 18 min
150º F 165º F 190º F
105º F 128º F 173º F
Auto Auto Auto
Core temperature exit cook 170oF
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3-zone Alkar continuous frankfurters cooking line
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Expected temperature variations

• Front-to-back 2 - 3oF
• Top-to-bottom
• Bone-in hams 5 - 8oF
• Frankfurters 3 - 6oF
• Pressed hams 4 - 12oF
• Slicing logs 4 - 10oF

To reduce variation
Product Uniform shape, uniform load, adequate
spacing, adequate clearance, good rack
design Oven Balanced airflow, calibrated
control system Process In the last step,
wet-bulb set higher than target core
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OUTLINE
Equipment and Process Validation
High humidity final cooking step
Uniform products size
Even Oven Loading
Balanced Airflow Preventive Maintenance
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Batch Oven Performance Validation location of
temperature probes
Legend DB-R Dry-Bulb, return air
DB-S Dry-Bulb, supply air
WB-R Wet-Bulb, return air C
Core temperature probes
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Things to think about

• Frequency of validation tests
• Monthly, quarterly, six-month, annual
• Temperature probe location in oven
• Establish test protocol
• Establish number of probes required
• Temperature acquisition equipment
• Calibrate probes against dry-block calibrator
• Handheld, wireless (Datatrace, Ellab, Dickson),
  portable, or fixed
• What is the limit for probe accuracy? (RTD, t/c,
  thermistor)
• What is your temperature measurement procedure?

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when validating a process

• Check ovens before validating processes
• Review the maintenance records
• Select products taking into account their
  characteristics
• Size, shape, composition
• ? affect temperature variation
• Validate the most sensitive processes
• Worse case scenario

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and when validating an oven.

• Time limits for accurate IT temperature
  measurements
• Slicing logs (4.5") 10 minutes
• Bone-in hams 30 minutes
• Frankfurters 15 seconds
• Keep it simple
• Leave yourself some wiggle room (?1?F)

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SUMMARY
Validate processes /oven /product
High humidity final cooking step
Uniform products size
Even Oven Loading
Balanced Airflow Preventive Maintenance
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EQUIPMENT AND PROCESS VALIDATION
For Batch and Continuous Ovens

• Alkar Technical Development