The expression troubleshooting may sound quite dramatic. However, what is understood here as troubleshooting is in fact any intervention that changes the operational parameters in order to obtain the desired result. An operator of a spray dryer is exposed every day to situations where he has to decide what to do if, for instance, the final moisture content of the product is suddenly too high. This is also a kind of mini-troubleshooting intervention. On the other hand there are troubleshooting operations requiring great effort in analyzing the situation and proposing a strategy for tackling the problem. This may be the case if one of the more sophisticated properties of the powder is deviating from the specification, due to lack of dryer capacity, formation of serious deposits in the dryer, bacteriological problems etc.
It is impossible to give exact instructions for each case. However, the paragraph below presents at least some guidelines for the most typical problems. The first approach to most problems involves:
- careful study of the production documentation around the time when the problem appeared, especially:
- log-sheets to find out any deviations from usual operating conditions,
- maintenance log-books to find out what changes or maintenance work on the dryer or its components have been conducted,
- laboratory analysis records to find out if any change of product quality has been detected,
- check the calibration of the control instruments which may have some connection to the problem,
- check independently the laboratory results,
- conduct laboratory analyses of the properties, which may have some connection to the problem, but are not part of the daily routine analyses,
- interview the staff individually about observations and opinions.
Lack of capacity
Product quality
In a factory producing the highest quality products, small adjustments of the plant operating conditions are part of the daily routine in order to compensate for small changes in external factors, mainly air humidity and milk composition. Factors influencing individual properties are described in chapter 10. The most important product properties, i.e. moisture content, insolubility index, scorched particles and bulk density are usually detected by process control in 1 - 2 hour intervals. The key person to decide what action to take to re-establish the desired target powder specification is the operator.The task of the technologist is to follow the variations in incoming milk and powder quality and to recommend the operating conditions for the operators. However, it is not unusual that suddenly, without any obvious reason, quality exhibits a serious deterioration. A more extensive investigation must then be conducted following the guidelines presented in the introduction to this chapter and using the guidelines for all involved individual properties as described in chapter 10. One of the external conditions, which can fluctuate quite extensively and which may have considerable influence on both powder quality and capacity, is the ambient air humidity. It is surprising how little attention is paid in practice to this factor. A humidity-meter placed in the main air intake can eliminate the necessity for a powder moisture adjustment, thus enabling a preventive correction before a deviation appears.
Fig. 12.2 shows levels of air humidity during a two week period (February 1992) in New Zealand (North Island). It is interesting to observe that the daily variations are between 3 - 7 g/kg. The maximum humidity in this period was 21 and minimum 11 g/kg. This would mean that for a single stage spray dryer operating at a constant outlet temperature, the moisture fluctuations would be in the range of 0.86% (see Fig. 10.1) or alternatively it would be necessary to adjust the outlet temperature within the range of 4.3°C.
Deposits in the system
Fire precaution
Thickness of powder layer
in mm |
Temperature
°C |
Time
hours.min |
---|---|---|
10 | 204 | 00.08 |
20 | 173 | 00.40 |
30 | 156 | 01.00 |
40 | 145 | 02.10 |
50 | 133 | 04.00 |
60 | 128 | 06.30 |
70 | 122 | 10.15 |
80 | 115 | 14.00 |

Principles of good manufacturing practice
The use of computer for quality control and trouble-shooting
İçindekiler tablosu
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1.Introduction
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2.Evaporation
- 2.1. Basic principles
- 2.2. Main components of the evaporator
- 2.2.1. Heat exchanger for preheating
- 2.2.1.1. Spiral-tube preheaters
- 2.2.1.2. Straight-tube preheaters
- 2.2.1.3. Preheaters to prevent growth of spore forming bacteria
- 2.2.1.3.1. Direct contact regenerative preheaters
- 2.2.1.3.2. Duplex preheating system
- 2.2.1.3.3. Preheating by direct steam injection
- 2.2.1.4. Other means to solve presence of spore forming bacteria
- 2.2.1.4.1. Mid-run cleaning
- 2.2.1.4.2. UHT treatment
- 2.2.2. Pasteurizing system including holding
- 2.2.2.1. Indirect pasteurization
- 2.2.2.2. Direct pasteurization
- 2.2.2.3. Holding tubes
- 2.2.3. Product distribution system
- 2.2.3.1. Dynamic distribution system
- 2.2.3.2. Static distribution system
- 2.2.4. Calandria(s) with boiling tubes
- 2.2.5. Separator
- 2.2.5.1. Separators with tangential vapour inlet
- 2.2.5.2. Wrap-around separator
- 2.2.6. Vapour recompression systems
- 2.2.6.1. Thermal Vapour Recompression – TVR
- 2.2.6.2. Mechanical Vapour Recompression - MVR
- 2.2.7. Condensation equipment
- 2.2.7.1. Mixing condenser
- 2.2.7.2. Surface condenser
- 2.2.8. Vacuum equipment
- 2.2.8.1. Vacuum pump
- 2.2.8.2. Steam jet vacuum unit
- 2.2.9. Flash coolers
- 2.2.10. Sealing water equipment
- 2.2.11. Cooling towers
- 2.3. Evaporator design parameters
- 2.3.1. Determination of heating surface
- 2.3.2. Heat transfer coefficient
- 2.3.3. Coverage coefficient
- 2.3.4. Boiling temperature
- 2.4. Evaporation parameters and its influrence on powder properties
- 2.4.1. Effect of pasteurization
- 2.4.1.1. Bacteriological requirements
- 2.4.1.2. Functional properties of dried products
- 2.4.1.2.1. Heat classified skim milk powders
- 2.4.1.2.2. High-Heat Heat-Stable milk powders
- 2.4.1.2.3. Keeping quality of whole milk powders
- 2.4.1.2.4. Coffee stability of whole milk powders
- 2.4.2. Concentrate properties
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3.Fundamentals of spray drying
- 3.1. Principle and terms
- 3.1.1. Drying air characteristics
- 3.1.2. Terms and definitions
- 3.1.3. Psychrometric chart
- 3.2. Drying of milk droplets
- 3.2.1. Particle size distribution
- 3.2.2. Mean particle size
- 3.2.3. Droplet temperature and rate of drying
- 3.2.4. Particle volume and incorporation of air
- 3.3. Single-stage drying
- 3.4. Two-stage drying
- 3.5. Expansion of air bubbles during drying
- 3.6. Extended Two-stage drying
- 3.7. Fluid bed drying
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4.Components of a spray drying installation
- 4.1. Drying chamber
- 4.2. Hot air supply system
- 4.2.1. Air supply fan
- 4.2.2. Air filters
- 4.2.3. Air heater
- 4.2.3.1. Indirect: Gas / Electricity
- 4.2.3.2. Direct heater
- 4.2.4. Air dispersers
- 4.3. Feed supply system
- 4.3.1. Feed tank
- 4.3.2. Feed pump
- 4.4. Concentrate heater
- 4.4.1. Filter
- 4.4.2. Homogenizer/High-pressure pump
- 4.4.3. Feed line
- 4.5. Atomizing device
- 4.5.1. Rotary wheel atomizer
- 4.5.2. Pressure nozzle atomizer
- 4.5.3. Two-fluid nozzle atomizer
- 4.6. Powder recovery system
- 4.6.1. Cyclone separator
- 4.6.2. Bag filter
- 4.6.3. Wet scrubber
- 4.6.4. Combinations
- 4.7. Fines return system
- 4.7.1. For wheel atomizer
- 4.7.2. For pressure nozzles
- 4.8. Powder after-treatment system
- 4.8.1. Pneumatic conveying system
- 4.8.2. Fluid bed system
- 4.8.3. Lecithin treatment system
- 4.8.4. Powder sieve
- 4.9. Final product conveying, storage and bagging-off system
- 4.10. Instrumentation and automation
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5.Types of spray drying installations
- 5.1. Single stage systems
- 5.1.1. Spray dryers without any after-treatment system
- 5.1.2. Spray dryers with pneumatic conveying system
- 5.1.3. Spray dryers with cooling bed system
- 5.2. Two stage drying systems
- 5.2.1. Spray dryers with fluid bed after-drying systems
- 5.2.2. TALL FORM DRYER™
- 5.2.3. Spray dryers with Integrated Fluid Bed
- 5.3. Three stage drying systems
- 5.3.1. COMPACT DRYER™ type CDI (GEA Niro)
- 5.3.2. Multi Stage Dryer MSD™ type
- 5.3.3. Spray drying plant with Integrated Filters and Fluid Beds - IFD™
- 5.3.4. Multi Stage Dryer MSD™-PF
- 5.3.5. FILTERMAT™ (FMD) integrated belt dryer
- 5.4. Spray dryer with after-crystallization belt
- 5.5. TIXOTHERM™
- 5.6. Choosing a spray drying installation
- 6.Technical calculations
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7.Principles of industrial production
- 7.1. Commissioning of a new plant
- 7.2. Causes for trouble-shooting
- 7.3. Production documentation
- 7.3.1. Production log sheets
- 7.3.2. General maintenance log book
- 7.3.3. Product quality specification
- 7.3.4. Operational parameter specification
- 7.4. Product quality control
- 7.4.1. Process quality control
- 7.4.2. Final quality control
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8.Dried milk products
- 8.1. Regular milk powders
- 8.1.1. Regular skim milk powder
- 8.1.2. Regular whole milk powder
- 8.1.3. Whole milk powder with high free fat content
- 8.1.4. Butter milk powder
- 8.1.4.1. Sweet butter milk powder
- 8.1.4.2. Acid butter milk powder
- 8.1.5. Fat filled milk powder
- 8.2. Agglomerated milk powders
- 8.2.1. Agglomerated skim milk powder
- 8.2.2. Agglomerated whole milk powder
- 8.2.3. Instant whole milk powder
- 8.2.4. Agglomerated fat filled milk powder
- 8.2.5. Instant fat filled milk powder
- 8.3. Whey and whey related products
- 8.3.1. Ordinary sweet whey powder
- 8.3.2. Ordinary acid whey powder
- 8.3.3. Non-caking sweet whey powder
- 8.3.4. Non-caking acid whey powder
- 8.3.5. Fat filled whey powder
- 8.3.6. Hydrolysed whey powder
- 8.3.7. Whey protein powder
- 8.3.8. Permeate powders
- 8.3.9. Mother liquor
- 8.4. Other Dried Milk Products
- 8.5. Baby food
- 8.6. Caseinate powder
- 8.6.1. Coffee whitener
- 8.6.2. Cocoa-milk-sugar powder
- 8.6.3. Cheese powder
- 8.6.4. Butter powder
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9.The composition and properties of milk
- 9.1. Raw milk quality
- 9.2. Milk composition
- 9.3. Components of milk solids
- 9.3.1. Milk proteins
- 9.3.2. Milk fat
- 9.3.3. Milk sugar
- 9.3.4. Minerals of milk
- 9.4. Physical properties of milk
- 9.4.1. Viscosity
- 9.4.2. Density
- 9.4.3. Boiling point
- 9.4.4. Acidity
- 9.4.5. Redox potential
- 9.4.6. Crystallization of lactose
- 9.4.7. Water activity
- 9.4.8. Stickiness and glass transition
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10.Achieving product properties
- 10.1. Moisture content
- 10.2. Insolubility index
- 10.3. Bulk density, particle density, occluded air
- 10.4. Agglomeration
- 10.5. Flowability
- 10.6. Free fat content
- 10.7. Instant properties
- 10.7.1. Wettability
- 10.7.2. Dispersibility
- 10.7.3. Sludge
- 10.7.4. Heat stability
- 10.7.5. Slowly dispersible particles
- 10.7.6. Hot water test and coffee test
- 10.7.7. White Flecks Number (WFN)
- 10.8. Hygroscopicity, sticking and caking properties
- 10.9. Whey Protein Nitrogen Index (WPNI)
- 10.10. Shelf life
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11.Analytical methods
- 11.1. Moisture content
- 11.1.1. Standard oven drying method (IDF Standard No.26-1964 [32])
- 11.1.2. Free moisture
- 11.1.3. Total moisture
- 11.1.4. Water of crystallization
- 11.2. Insolubility index
- 11.3. Bulk density
- 11.4. Particle density
- 11.5. Scorched particles
- 11.6. Wettability
- 11.7. Dispersibility
- 11.8. Other methods for determination of instant properties
- 11.8.1. Sludge
- 11.8.2. Slowly dispersible particles
- 11.8.3. Hot water sediment
- 11.8.4. Coffee test
- 11.8.5. White flecks number
- 11.9. Total fat content
- 11.10. Free fat content
- 11.11. Particle size distribution
- 11.12. Mechanical stability
- 11.13. Hygroscopicity
- 11.14. Degree of caking
- 11.15. Total lactose and α-lactose content
- 11.16. Titratable acidity
- 11.17. Whey Protein Nitrogen Index (WPNI)
- 11.18. Flowability (GEA Niro [31])
- 11.19. Lecithin content
- 11.20. Analytical methods for milk concentrates
- 11.20.1. Total solids
- 11.20.2. Insolubility index
- 11.20.3. Viscosity
- 11.20.4. Degree of crystallization
- 12.Troubleshooting operations
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References