Safety and the Extrusion Coating Process

Transcription

1 Safety and the Extrusion Coating Process John D. Vansant DuPont Company (Presented by John L. Kelley) This is not an all inclusive guide to polymer processing and equipment operation safety. Please consult your polymer and equipment suppliers, as well as appropriate government and industry standards for specific recommendations and requirements. 1

2 Disclaimer The information herein is intended for guidance only While believed reliable, DuPont neither warrants or guarantees its completeness, efficacy or safety in use. It is intended for use only by competent personnel. The user accepts full responsibility for its use and fully indemnifies and holds DuPont harmless from any loss, claim damage, or injury arising out of its use regardless of cause, unless user shows such to have been caused directly by ill will or willful misconduct of DuPont. Also, no license is granted or implied, and no recommendation to infringe any patent is made. Overview Safety philosophy Elements of safe operation Material Safety Data Sheets Fumes, processing temperatures and exhaust systems Burns and personal protective equipment Rupture discs Coextrusion piping and polymer packing 2

3 Safety Philosophy Injuries and occupational health illnesses are preventable The goal is zero injuries or high potential incidents. Individuals are responsible for their personal safety and for the safety of those who work around them. 3

4 Elements of Safe Operation Hazardous Conditions Safe Design Safe Actions Dismantle & Remove Manufacturer Specified Operations Changes Safe Design Owner Specified Maintenance Changes Installation Decisions 4

5 Overhead Lifts High Voltage Nips Moving Webs Moving Carriage Hazardous Conditions Hot Surfaces Hot Polymers Poor Housekeeping Good Communication Risk Assessment Emergency Plans Safe Actions Safe Operating Procedures Management of Change Personal Protective Equipment 5

6 Elements of Safe Operating Procedures Personal Protective Equipment Lock-out requirements Interlock and Safety Device usage and inspections Signatures of Management and ALL Operators (read and understood) Communication Line of site and vocal response for nip closure and carriage movement Shift Change Changes to the Routine Reporting Problems 6

7 Management of Change Equipment changes or new equipment New materials Abnormal temperatures and pressures New procedures and procedure updates Risk Assessments and Hazard Reviews Risk Assessments Equipment Design Limits Potential Hazards, New and Old Procedures in place and adequate? Process Understood? Proper Representation Operator, Engineer, Safety, Management 7

8 Nip Hazards Never point or reach into a nip use a tool String-up is high risk time! All rolls are a potential hazard Tight gaps are just as hazardous Nip guards Loose clothing Flag with a tool High Voltage Electrical Hazards Heaters especially plate heaters Corona Treaters and wiring Motor Drives Control Cabinets Multiple Power Sources Lock, Tag, Clear, Try, Test 8

9 Higher Hazard Times Start-ups and String-ups Edge Trim Breaks Roll Wraps Roll Changes New Materials Maintenance End of Shift and Night Shift Protection from polymer burns Synthetic clothing can melt at extrusion coating melt temperatures Leather gloves can shrink to hands holding in heat Do not try to wipe molten polymer off skin First aid: cold water, lots of it? Do you have cold water near your extruder? 9

10 MSDS s How I read them Composition monomers additives * seek information on chemicals you don t know Hazards read all particular attention to inhalation and eye hazards MSDS (continued) First Aid Measures deepens understanding of the hazards Flash Point Hazardous Combustion Products indicates what could be given off as products of oxidation 10

11 MSDS (continued) Exposure Controls / Personal Protection Furthers understanding of the hazards Respirable dust Ventilation requirements Melting Point Assess potential for freeze-off MSDS (continued) Stability and Reactivity Conditions to avoid: temperatures above Decomposition HAZARDOUS DECOMPOSITION PRODUCTS Find safety information on decomposition products or consult an occupational health chemist or specialist. 11

12 Other Supplier Information Product data sheets maximum use temperature melting / freezing temperatures viscosity or melt index pressure build-up flow in rupture discs Product Safety Bulletins Polyethylene Smoke Products of oxidation 1 Carboxylic Acids Aldehydes Formaldehyde Acrolein - strong irritant Ketones Note: These products are present in virtually all hydrocarbon smoke including tobacco, wood etc. 12

13 Weight of Sample in % Typical Thermal Degradation of Polyethylene in Air by TGA A Degrees Celcius B C D Degradation of Polyethylene W eight of Sam ple in % Typical Thermal Degradation of Polyethylene in Air by TGA 10 C/min Degrees Celcius Rate of degradation increases with temperature and time Safe temperature limit is not obvious Keep temperatures as low as possible to minimize degradation and off gasses 13

14 Degradation of Polyester and EVOH Produces acetaldehyde Acetaldehyde syndrome Sweet smell Good Ventilation is essential Avoid large purge volumes - holds heat Avoid high rate purging Coextrusion with higher temperature resins can cause degradation in purge pans Polymer Smoke Evacuation Slot hoods should not allow leakage between hood and die Hood needs to capture smoke in both running and purge positions Refer to Industrial Ventilation 2 book for design information 14

15 Evacuation of Fumes Effectiveness depends on Capture Velocity Capture Velocity decreases as inverse square of distance from hood opening At twice distance - velocity is 1/4 Source: Industrial Ventilation 2 Flange Hoods to Increase Efficiency Flange increases capture velocity 42% with slot hood Flange decreases hood entry loss by 47% Source: Industrial Ventilation 2 15

16 Effective Purge Pan Ventilation Heat causes smoke to rise Turbulence expands the smoke as it rises Keep pan as high as possible and hoods far apart Rupture Discs Disc Threaded tube body 16

17 Rupture Disc Installations Keep tubes short freeze-off potential increased flow capacity lower cost Good Point away from operators Decomposed polymers can spray Protect coextrusion piping Verify flow capacity Heater Band Pipe Wall Bad Polymer Packing 3 Polymers are less dense when molten Form voids on cooling when contained Pipe cools more quickly - draws polymer from larger cavities - packing Can generate great pressure when heated - heats more quickly Heat and soak die and extruders before heating pipe 17

18 References 1. Villberg K.T., Veijanen A.K., Volatile organic compounds in LDPE films and air during extrusion coating Tappi J. 81(8):165(1992) 2. Committee on Industrial Ventilation, American Conference of Governmental Industrial Hygienists, Inc., Industrial Ventilation 20th Edition, Smith, D.J., Bayless, R.F., Safety considerations in the design and operation of polymer transfer piping. Report by Egan Davis Standard. 4. Gerald D. Godfrey, Black Clawson Co., Extrusion Coating and Laminating Safety Tappi Extrusion Coating for Engineers Short Course, February