Handbook of Seal Integrity in the Food Industry

Michael Dudbridge has managed food manufacturing operations for major companies throughout his career. Roles have included factory operations and quality management as well as engineering and continuous improvement responsibilities.

• Introduction, xiv About the author, xvCHAPTER 1 Overview of sealing technologies, formats and systems, 11.1 Introduction, 11.2 The importance of packaging and seal integrity, 11.3 The sealing of rigid containers, 31.4 Hermetic seals, 31.5 Developments in the canning process, 41.5.1 Thinner materials, 51.5.2 New materials, 51.5.3 Additional protection of the container from secondary packaging, 61.6 Heat sealed packages, 61.7 What is a good seal?, 81.8 So … what is a good seal?, 101.9 Seal management in a packing operation, 121.9.1 Setting the required standards, 121.9.2 Second step – set up a testing system for seals in your business, 121.10 Testing systems, 131.10.1 Mechanical squeeze test, 131.10.2 Sniffer systems, 131.10.3 Vision systems, 141.10.4 Ultrasound systems, 141.11 How is a good seal made?, 141.12 Heat sealing, 151.12.1 Heated tooling, 151.12.2 Induction sealing, 151.12.3 Ultrasonic sealing, 161.12.4 Spin welding, 171.12.5 Hot gas/radiant heat sealing, 171.13 Non]heat sealing methods, 171.13.1 Cold sealing, 171.13.2 Adhesive sealing, 171.13.3 Solvent sealing systems, 171.14 Packaging materials, 181.15 Sealing parameters, 181.15.1 Sealing temperature, 181.15.2 Flow characteristics, 191.15.3 Surface printing, 191.15.4 Material strength, 201.15.5 Material structures, 201.16 Packaging systems, 211.16.1 Bag]making systems, 211.16.2 Pouch sealing systems, 211.16.3 Tray sealers, 221.16.4 Horizontal form fill seal (HFFS) systems, 221.16.5 Flow wrapping system, 231.17 The requirements of industry for seal integrity in its packaging systems – an overview, 241.17.1 Safety, 241.17.2 Containment, 241.17.3 Shelf]life extension, 241.17.4 Seal strength, 251.17.5 Accessibility, 251.17.6 Display attractiveness, 261.17.7 Portion control and multi]compartment trays, 271.17.8 Consumer confidence, 271.18 Industry sectors – some recent increases in seal performance requirements, 281.19 Making changes to packaging materials or systems, 29CHAPTER 2 The operation and design of tray sealing machines, 302.1 Introduction, 302.2 The principles of sealing preformed trays, 302.3 Types of tray sealing machines, 312.3.1 Small hand]operated machines, 312.3.2 Larger, more automated machines, 312.3.3 Very large tray sealing systems, 322.4 The components of a tray sealing system, 332.4.1 The tray handling system, 332.4.2 The top film handling system, 342.4.3 The sealing tools, 342.4.4 The grabber arms, 352.5 Tray sealing machine set]up, 372.5.1 The top tool, 372.5.2 The bottom tool, 372.5.3 The grabber arms for in]line machines, 392.5.4 Temperature settings, 392.5.5 Dwell times, 392.5.6 Top film feed, 402.5.7 Top film tension, 412.5.8 The in]feed stopper positions for in]line machines, 422.6 Maintenance of tray sealing machines, 422.6.1 Maintenance of the top tool, 432.6.2 The maintenance of the bottom tool, 452.6.3 Maintenance of the in]feed, grabber and out]feed systems, 472.6.4 Maintenance of the film handling system including the scrap take]up system, 492.7 Machine services, 492.8 The special case of modified atmosphere tray sealing, 492.9 The special case of controlled atmosphere tray sealing, 502.10 The trays used in tray sealing operations, 512.11 Top film used in tray sealing operations, 51CHAPTER 3 The design and operation of bag]making machines, 533.1 Introduction, 533.2 System overview, 533.2.1 The film handling system, 533.2.2 Back sealing system, 533.2.3 The filling process, 543.2.4 The top seal, 543.3 Types of VFFS machine, 573.3.1 Top and bottom sealing jaw design variations, 573.3.2 Back seal design variations, 583.3.3 The implications of the back seal for the overall seal integrity of the pack, 603.4 Components of a VFFS machine, 613.4.1 Film handling and forming system, 613.4.2 Multiple functions of the forming system, 623.4.3 The sealing jaws, 633.4.4 Support arms, 673.4.5 Exit conveyor systems, 683.4.6 Controls of a VFFS system, 683.5 VFFS machine set]up, 693.6 Maintenance of VFFS systems, 703.7 The feed of product into the VFFS, 703.8 Sealing jaw maintenance, 713.9 Jaw and back sealer heating systems, 733.10 Film forming system, 733.11 Calibration, 753.12 The special case of modified atmosphere packing with VFFS, 763.13 Packaging materials for VFFS systems, 773.13.1 Sealing surfaces, 783.13.2 Printed materials, 79CHAPTER 4 The design and operation of horizontal form fill seal systems, 804.1 Introduction, 804.2 The sequencing of an HFFS system, 804.2.1 Thermoplastic material introduced and heated, 804.2.2 Moulding of softened film, 814.2.3 Cooling and filling, 824.2.4 Sealing, 824.2.5 Cutting, 834.3 Types of HFFS machines, 844.3.1 Machines with two heating stations, 844.3.2 Machines with two moulding stations and two sealing stations, 854.4 Components and subsystems of HFFS machines, 854.4.1 The bottom film handling systems, 854.4.2 The moulding system, 864.4.3 The filling station, 884.4.4 The lidding section, 894.4.5 Labelling of the packs, 904.4.6 The cutting section, 914.4.7 The vacuum system, 924.5 Setting up an HFFS machine, 934.5.1 Temperature control of the heaters in the moulding section, 934.5.2 Positioning of the sealing heads, 944.5.3 Positioning of the star stamps, guillotine and rotary cutting knives, 954.6 Maintenance, 964.6.1 The gripper chains, 964.6.2 The sealing heads, 974.6.3 Seal area contamination, 974.7 Special case of modified atmosphere packing, 984.8 Films used, 100CHAPTER 5 The causes of seal integrity issues, 1015.1 Introduction, 1015.2 Background, 1015.3 Objective, 1025.4 Study methods, 1025.4.1 The interview, 1025.4.2 Shop floor study, 1025.4.3 Vacuum testing, 1035.4.4 Dye penetration testing, 1035.5 Companies studied, 1035.5.1 Category of food product, 1035.5.2 Product constituents, 1045.5.3 Size of factory, 1045.5.4 Intensity of production, 1055.6 Key results, 1055.7 Rate of seal failure, 1055.8 Discussion of the impact of poor seal integrity, 1075.9 Disposal and repacking of food, 1085.10 Disposal of packaging, 1085.11 Managing the sealing activity, 1085.11.1 Methods for monitoring the integrity of seals, 1085.11.2 Management of the standard operating procedures, 1105.11.3 Maintenance procedures, 1115.12 Conclusions, 1125.12.1 Robust filling methods, 1125.12.2 Standard operating procedures, 1125.12.3 Planned preventative maintenance, 1135.12.4 Seal testing, 1135.12.5 Rework of packs, 1135.12.6 Packaging materials, 1145.13 Moving forward, 1145.14 Lessons for packaging managers and supervisors, 114CHAPTER 6 Seal testing techniques, 1166.1 Introduction, 1166.2 Seal strength, 1166.3 Leaking seals, 1176.4 Seal appearance, 1176.5 Testing seal strength, 1196.5.1 Burst tests, 1196.6 ASTM International seal testing standards, 1206.6.1 Seal strength – ASTM F88 and F2824, 1206.6.2 Seal strength – ASTM F2824, 1226.6.3 Burst test – ASTM F1140, 1226.6.4 Creep test – ASTM F2054, 1226.6.5 Vacuum dye or dye penetration test – ASTM D3078, 1226.7 Pouch integrity testing, 1236.8 Seal strength by inflation and seal integrity testing (destructive tests), 1256.8.1 Burst testing, 1256.8.2 Creep and creep]to]failure testing, 1256.9 Leak detection, 1266.9.1 Pressure decay method, 1266.9.2 Vacuum decay method, 1276.10 Non]destructive tests, 1286.11 Shop floor detection of leaking packs, 1286.11.1 The mechanical squeeze test, 1296.11.2 The trace gas detection methods, 1296.11.3 Computer vision systems, 1306.11.4 Vacuum decay systems, 1316.11.5 Vibration and deceleration analysis, 1316.11.6 Ultrasonic systems, 131CHAPTER 7 Packaging materials and their impact on seal integrity, 1337.1 Introduction, 1337.2 What is a thermoplastic?, 1347.2.1 Molecular structure of thermoplastics, 1347.3 Commonly used sealable thermoplastics, 1377.3.1 High]density polyethylene (HDPE), 1377.3.2 Low]density polyethylene (LDPE), 1377.3.3 Linear low]density polyethylene (LLDPE), 1397.3.4 Polypropylene (PP), 1397.3.5 Polyvinyl chloride (PVC), 1397.3.6 Polyethylene terephthalate (PET), 1397.4 Co]polymers, 1407.4.1 Acid co]polymers, 1407.4.2 Ethylene vinyl acetate, 1407.4.3 Ionomers, 1407.5 Eco polymers, 1407.5.1 Polylactic acid (PLA), 1407.5.2 Polyhydroxyalkanoates (PHA), 1417.6 Adhesive and cohesive sealing, 1417.6.1 Intertwining of the molecules, 1417.6.2 Intermolecular forces, 1417.6.3 Adhesive sealing, 1417.7 Laminated packing materials, 142CHAPTER 8 Seal strength, 1438.1 Introduction, 1438.2 Seal strength – a definition, 1438.3 The implications of distribution, retail and domestic situations, 1448.3.1 Transit trials and simulations, 1448.3.2 The impact of temperature changes, 1458.3.3 The impact of pressure changes, 1468.3.4 Returnable transit containers (RTCs), 1478.3.5 Logistics route, 1478.3.6 Retail pressure, 1488.3.7 Transport home, 1488.4 Measurement of seal strength, 1498.4.1 Hot tack seal strength, 1498.4.2 Burst testing, 1528.4.3 The pull test, 153CHAPTER 9 Peelability and openability, 1549.1 Introduction, 1549.2 Peelable films, 1559.2.1 Delamination, 1559.2.2 Adhesive peel, 1569.2.3 Cohesive peel, 1579.3 Sealing machine set]up for peelable films, 1589.4 The age of the film, 1609.5 The design of the seal area, 1619.6 The selection of a peelable film, 1619.7 Product condition when sealing, 1619.8 Openability, 1619.8.1 Why consider openability?, 1629.8.2 The tear notch, 1629.8.3 The peel tab, 1639.8.4 Perforations and lines of weakness, 1639.8.5 Rip strip, 1659.8.6 Easy]open lids, 165CHAPTER 10 Resealing a pack, 16710.1 Introduction, 16710.2 Is it resealed?, 16710.3 Types of resealable packs, 16810.3.1 The clip]on lid, 16810.3.2 The dead fold system, 16910.3.3 The sticker system, 17010.3.4 The zip system, 17110.3.5 The velcro type system, 17110.3.6 The screw cap, 17110.3.7 The flip lid, 17210.3.8 Sports cap, 17410.3.9 Resealing using adhesives, 17410.3.10 Injection moulding, 17610.4 Single portion packs, 176CHAPTER 11 Seals for non]flexible packs, 17711.1 Introduction, 17711.2 Sealing systems for heat]processed cans, 17711.3 Glass jar sealing systems, 17911.4 Bottle sealing systems, 18011.5 Sealing methods for rigid containers, 18111.5.1 Preformed container and preformed lid, 18111.5.2 Preformed container and lid moulded into position, 18211.5.3 Preformed container and a clip]on lid, 183CHAPTER 12 Oxygen and moisture migration, 18412.1 Introduction, 18412.2 How does oxygen migrate through materials and how do we measure OTR?, 18512.3 Packaging specifications, 18512.4 The theory of diffusion, 18612.5 Measurement of OTR, 18712.6 MTR, 18812.7 Impact on MAP systems, 18912.8 Controlled atmosphere packaging, 19012.9 Impact of down]gauging of material thicknesses, 19112.9.1 Increased MTR and OTR, 19112.9.2 Packing machine operation, 19112.10 Barrier layers to improve OTR and MTR, 191CHAPTER 13 Tamper evidence technology, 19213.1 Introduction, 19213.2 Neck sleeves and paper bands, 19213.2.1 Tamper bands, 19313.2.2 Tamper evident screw caps, 19313.3 Induction sealed tamper evidence systems, 19313.4 Injection moulded parts, 19513.5 The screw cap with band, 19613.6 Test buttons on jars, 19613.7 Film overwrap for cartons, 19713.8 Stickers and paper labels, 197CHAPTER 14 Innovations in packaging to improve seal integrity and the detection of sealing issues, 20014.1 Introduction, 20014.2 Packaging materials, 20014.2.1 The LINPAC Rfresh Elite® system, 20114.2.2 Packaging shape and usability, 20114.3 Sealing systems, 20114.3.1 Laser sealing, 20114.3.2 The integrity seal, 20214.4 Detection systems, 20214.4.1 Seal scope, 20214.4.2 Modified atmosphere packaging, 20314.4.3 Carbon dioxide]sensitive labels, 20314.4.4 Multispectral imaging, 20314.4.5 Laser scatter, 20414.4.6 Polarised light, 20414.4.7 Multiple image analysis, 20614.4.8 Active and intelligent inks, 20614.4.9 Bump Mark, 20614.4.10 Smart labels, 206Index, 207