Thermal protection


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Thermal protection

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  3. 3. INTRODUCTION The fire hazard is the most pervasive, be it home, work place or in the time of calamity. The most devastating are the result of fire hazard when a person’s clothing ignites. Wearing fire resistant garment reduces the burn injury and increasing the chances of surviving the flash fire. 3
  4. 4. Should Meet The FollowingRequirements Flame resistance . Fabric integrity . Good thermal insulation . Oil repellency . Easy cleanibility . Wearer acceptance . 4
  5. 5. Flame Retardant Fibre These fibres may be used solely or in blend form to arrive at optimum performance and cost. Chemically modified fibres and fabrics. 5
  6. 6. Measure for high temperatureperformance A high temperature textile is define as a material that can be used continuously at temperature over 200 c without losing its major physical properties. Another is LOI which is used to rate the flammability of fibre. LOI is %age oxygen level that must be present in oxygen/nitrogen mixture of air before the fibre would ignite and burn when exposed to flame. Fibre with LOI in the mid 20s and above is considered flame resistant. 6
  7. 7. Different Fibres Aramid fibres ( Nomex) . PBI ( Polybenzimidazole ) . Polyamide-imide ( Kermal ) . Polyimide fibres ( Lenzing P84 ) . Phenolic fibre ( Kynol ) . Chlorofibres . Polyphenylene sulphide fibres i.e PPF Semicarbon fibres. 7
  8. 8. Aramid Fibres Aramid fibres contains no flame retardant chamical i.e phosphorus or halogen. Nomex has good thermal stability and dose not melt. Nomex especially suitable for firefighters. Protective garments made from Nomex are also quit comfortable. Aamid fibre garment can be laundered and dry cleaned without any loss of flame retardency. 8
  9. 9. Polybenzimidazole PBI does not burn in air. PBI fabrics remain stable and maintain integrity. PBI retains its strength well when tested during exposure at elevated temperature. 9
  10. 10. Kermal Heat resistant and inherently non flammable fibres. It is non melting and non shrinking organic fibre which offer light weight and soft hand. It is high price but high performance fibre 10
  11. 11. Polyphenylene Sulphide fibre It is classified as non flammable . LOI is 34-35 . It dose not support combustion under normal atmospheric condition. In addition, its chemical resistance and ability to retain its physical properties under extremely adverse condition make it valuable for protective clothing. 11
  12. 12. Polyacrylate fibres It neither burns nor melts. It emits virtually no smoke or toxic gases. LOI is 43 . 12
  13. 13. Semicarbon fibres These fibres are produced by partial carbonization of PAN fibres, for e.g Celiox and Panox . Excellent heat resistance . Comfort to wear. 13
  14. 14. Chemically Modified Fibres AndFabric Special treatment are given to fibre and fabric to make them fire resistant , for e.g :- At the polymerization stage. By using some modifier. By surface modification . 14
  15. 15. Protective Clothing Firefighter protective clothing limit the dissipation of body metabolic heat. So protective garment has several layers :- Outer shell . Vapour barrier . Inner liner . 15
  16. 16. Design Features Coat and jacket . Collar . Front closure . Coverall or pants . 16
  17. 17. Effect Of Fabric Construction In hot environment or direct flame ( 150-250 g/m² ) For full installations (250-320 g/m² ) For workshop (320-400 g/m² ) Against molten metal (900 g/m² ) 17
  18. 18. Current ASTM Standards TPP, NFPA 2000, (the former ASTM D 4108), ASTM F 2700-08, ISO 9151, ISO 17492, CGSB ASTM F955 -07 : Molten Substances, ISO 9150, ISO 9185/BS373 18
  19. 19. ASTM standard ASTM F 2700‐08, Standard Test Method for Unsteady‐State Heat Transfer Evaluation of Flame Resistant Materials for Clothing with Continuous Heating (NFPA 1971 Thermal Protective Performance (TPP) test) ASTM F1939 ‐08, Standard Test Method for Radiant Heat Resistance of Flame Resistant Clothing Materials with Continuous Heating ASTM F 1060 ‐08, Test Method for Thermal Protective Performance for Protective Clothing for Hot Surface Contact ASTM 2701 – 08 Standard Test Method for Evaluating Heat Transfer through Materials for Protective Clothing Upon Contact with a Hot Liquid Splash 19
  21. 21. Chemical Protection Protective clothing cannot be made generic for all chemical applications, since chemicals vary in most cases and a particular CPC can protect only against a limited number of specific chemicals. Important considerations in designing chemical protective clothing are The amount of chemical permeation. Breakthrough time for penetration. Liquid repellency. Physical properties of the CPC in specific chemical conditions. 21
  22. 22. c  Chemical protective clothing can be categorized as encapsulating or non-encapsulating based on the style of wearing the clothing.  CPC is rated for four levels of protection, levels A, B, C and D from highest protection to normal protection. 22
  23. 23. Routes of Exposure 23
  24. 24. Requirements Chemical Protective Clothing Should Resist : Permeation , Degradation, Penetration. Durability Flexibility Temperature Resistance Service Life Clean Ability 24
  25. 25. Permeation Permeation is the diffusion of a chemical on a molecular basis through chemical protective clothing. This movement of the chemical through the protective material may not be readily noticeable because it occurs on a molecular or microscopic level. The time it takes the chemical to pass through the protective material until it is first detected by an analytical instrument is called the breakthrough time. 25
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  27. 27. Degradation The change in the physical properties of the material as a result of adverse effects of the chemical is called degradation. Physical properties may include material weight, dimensions, tensile strength, hardness. The most common observations of material degradation are Swelling, Loss of Strength or Deterioration. 27
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  29. 29. Penetration Penetration is defined as `the flow of chemical through closures, porous materials, seams, and pinholes and other imperfection in a protective clothing material on a non-molecular level. This definition is intended to accommodate both liquids and gases. Penetration of chemicals may take place through Zippers, Seams or Imperfections in Protective Clothing 29
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  31. 31. Textile Materials Ordinary textile materials are generally not considered suitable for protection against chemicals, however special non-coated textile materials are used for a variety of applications involving particulates and light liquid spray from relatively non-hazardous chemicals. Though woven textiles are not often found in chemical protective clothing, very tightly woven, repellent-treated fabrics can provide some very low minimum protection against liquid exposure. More common are nonwoven fabrics that have demonstrated barrier performance against particles and repellency of liquids. Two predominant examples of non- woven fabrics are flashspun polyethylene (Tyvek) and spunbond/ meltbown/ spunbond (SMS) polypropylene (Kleenguard). These textiles are used because of their relatively low cost and because the materials provide a structure of microfibers that filter out dry particulates and many water-based liquids. 31
  32. 32. Flash Spun Polyethylene Made from very fine, high-density polyethylene fibers, lightweight yet strong; vapor permeable, yet water- and chemical-resistant, as well as puncture-, tear- and abrasion-resistant. Tyvek® is formed by a fully integrated process using continuous and very fine fibers of 100% high-density polyethylene that are randomly distributed and no directional. These fibers are first flash-spun, then laid as a web on a moving bed before being bonded together by heat and pressure - without the use of binders. Extensive Temperature Range, Excellent Dimensional Stability: - 73°C (132°C). 32
  33. 33. SMS Polypropylene Breathable fabric multilayered laminate. The two outer spun bond layers are made of randomly deposited 15 – 20 micron diameter continuous polypropylene fibres which provide cloth-like comfort while also offering fabric strength, durability and abrasion resistance. The inner melt blown layer provides a filter barrier and is typically comprised of 1-3 micron diameter polypropylene fibres. The advantage of melt blown as the barrier layer is that it is permeable to both air and moisture vapour, meaning that both air and sweat vapour can pass through the garment to keep the skin cool and the wearer more comfortable in hot working environments. 33
  34. 34. Unsupported Rubber and Plastic Materials Normally, chemical protective clothing materials include supporting textile fabrics to provide strength. However, there are some CPC materials that do not include a fabric substrate. The rubber material or plastic is thick enough to provide sufficient strength for clothing use. Examples of polymers used in these materials are polyvinyl chloride and chlorinated polyethylene. Because the materials are continuous, they offer a barrier to liquids and can be used in the construction of CPC intended for protection against liquids and gases. 34
  35. 35. Micro Porous Film-Based Materials Microporous films have millions of microscopic pores per square inch of the film structure. In most cases, the pores are irregularly shaped with tortuous paths through the film. This material feature makes the film `breathable . The microporous films are generally glued or laminated to woven or nonwoven fabrics for physical support. Owing to their physical structure, these fabrics provide barrier performance against liquids but not gases. 35
  36. 36. Adsorbent-Based Materials These materials include adsorbents, such as activated charcoal or other sorbent materials. Activated Carbon : Activated carbon in very fine powder or granular form is useful to purify both water and air. Activated carbon has particular affinity to organic materials such as solvents used in printing inks and common coatings. 36
  37. 37. Development of Chemical Protective Clothing: The chemical protective clothing is formed by five layers, the outer shell made of polyester as it has low absorption of 2% and it provides a good strength to the fabric and polyester has a good resistance to lab grade chemicals. The inner layer is made up of cotton fabric as it gives good absorbency and comfort. The middle layer comprises of cotton non woven sandwiched with activated carbon. 37
  38. 38. Some other fabrics Coated nylon or polyester fabric. Coated with butyl rubber having base fabric varies between 250-500g/m². Multilayer sandwiched type :- Polymide or polyester is sandwiched between weldable pollyolefin films. Weight 100-150 g/m² 38
  39. 39. c The conventional chemical protective clothing was based on embedding activated carbon using adhesives and polyurethane foam with a activated carbon load of 120 – 160 GSM. These fabrics had low comfort properties of air permeability and thermal comfort causing stress to the wearer. 39
  40. 40. Needle Punching Technology 40
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  42. 42. Garment Design Features The type and location of Seams. The type, length, and location of the closure system(s). The type and characteristics of visors or face shields, if integrated into garments. The design of interface areas with other chemical protective clothing or equipment. 42
  43. 43. Seams 43
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  45. 45. Closure Systems Closures are typically the `weak link in the chemical protective clothing barrier. The simplest closures are zippers or a series of snaps. CPC designs use storm flaps to cover the zipper or snaps Liquid-repellent zippers are conventional zippers that use rubber or plastic coated tape instead of woven cloth on the sides of the zipper and that have a special chain (teeth) that are coated to limit liquid penetration. 45
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  47. 47. Garment Visors Visors are generally incorporated into suits to offer chemical barrier protection for the head and face area. In general, the visor is constructed from a material that provides clear undistorted vision as well as chemical resistance. The principal materials used in visor construction are polyvinyl chloride, polycarbonate, and polymethacrylate. Since the visor material must provide optical qualities, only transparent materials can be chosen as visors. When greater chemical resistance is required, the visor be made of a composite material that includes fluorinated ethylene propylene (FEP) laminated to PVC. 47
  48. 48.  cLevels of Chemical Protection 48
  49. 49. Level A Level A should be worn when the highest level of respiratory, skin, and eye protection is required. Level A is used when: Conditions are unknown. The hazardous substance has been identified and requires the highest level of protection for skin, eyes, and respiratory system. Operations are being conducted in confined, poorly ventilated areas. Work function involves a high potential for splash, immersion, or exposure to unexpected skin hazards . 49
  50. 50. Fully Encapsulating Suit With Self-Contained Breathing Apparatus. 50
  51. 51. Level B Self-contained breathing apparatus, Chemical protective clothing, gloves, and hard hat. Should be selected when the highest level of respiratory protected is needed and some degree of skin protection is required. Level B is the minimum recommendation for initial site entry. Level B protection is used when: Air contaminants are unknown. Air contaminants have been identified and the criteria for using APRs are not met. The atmosphere contains less than 19.5% oxygen. Direct contact does not pose a severe skin hazard. 51
  52. 52. Self-contained BreathingApparatus, Chemical ProtectiveClothing, Gloves, And Hard Hat. 52
  53. 53. Level C Level C should be selected when types of airborne contaminants are known, the concentrations are measured and the criteria for using air-purifying respirators (APRs) are met. Level C protection is used when: Criteria for the use of APRs are met. Air contaminants have been identified and concentrations measured. Direct contact does not pose a skin hazard. 53
  54. 54. Air-purifying Respirator, ChemicalProtectiveClothing, Gloves, Boots, AndHard Hat. 54
  55. 55. Level D Level D should not be worn on any site with respiratory or skin hazards. Level D is primarily a work uniform providing minimal protection. Level D protection is worn when: Atmosphere contains no known hazards. Work functions precludes the potential for unexpected exposure to hazardous levels of any substances. 55
  56. 56. Clothing, Boots, Gloves, And HardHat 56
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  58. 58. Various Test Method For CPC ASTM F1186-03 ASTM F1001-99a ASTM F739-99a ASTM F1383-99a ASTM F1407-99a ASTM F1194-99 ASTM F903-03 ASTM F2053-00 ASTM F2130-01 EN 943-1:2002 EN 467:1995 EN374-3:1994 EN ISO 6529 ISO 6530 (1990) ISO 13994 (1998) ISO 17491(2002) 58
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