moist heat sterilisation

    Cards (15)

    • moist heat sterilisation temperature 

      56 degrees celsius
    • is moist heat sterilisation used for pharmaceutical products?

      no
    • autoclaving
      moist heat temp > 100 degrees celsius can only be achieved under pressure, performed In autoclave - similar to domestic pressure cooker but better facilities for control
      organisms killed by a combo of temp, hydration, time
    • properties of steam in a closed container

      PV/T = constant
      Pressure
      volume
      temperature
      at constant volume pressure varies with temperature
    • different types of steam
      Superheated steam - water in the vapour phase and behaves like a gas, if temp decreases the pressure decreases
      supersaturated steam/ wet steam - in liquid phase made up of small droplets of water held in suspension by convection currents
      dry saturated steam - exists on the phase boundary, if you lower the temp it will condense ( only one suitable for sterilisation)
    • factors playing a role in dry saturated steam?

      • release of heat
      • hydration
      • penetration
    • 1.release of heat
      sensible heat - when exchanged, results in change of temperature
      latent heat - when exchanged, results in change of physical state - there is no temp change
      supersaturated steam - releases only sensible heat
      superheated steam - releases only sensible heat
      dry saturated heat - releases sensible and latent heat
    • 2.hydration
      dry saturated steam causes a moist heat reaction - rapid heat transfer
      superheated steam causes a dry heat reaction - slower heat transfer
    • 3.penetration
      dry saturated steam causes rapid penetration
      superheated steam causes poor penetration
    • design of autoclaves
      portable bench top sterilisers
      large scale sterilisers
    • bench autoclaves
      • easy to se
      • word well for small number of items
      • does not suffer from superheating as there is water in the vessel itself
      • inefficient if vessel gets too large - problems with heat loss and not effective for generating steam at large volumes
    • large scale autoclaves
      • use separate steam generator
      • often have a heated outer jacket - necessary for even heat distribution and cooling after autoclaving
    • different types of large scale autoclaves
      • gravity displacement autoclave- steam added from top, air is removed at bottom
      • porous load autoclave (vacuum assisted) - fitted with vacuum sumo to remove air before adding steam
    • what does autoclaving do?

      Autoclaves are used to sterilize and decontaminate items using pressurized steam to kill microorganisms and spores
    • stages of operation of autoclaving?

      • air removal and steam admission
      • heating up and exposure
      • drying and cooling - dry using vacuum and or heat from outer jacket and cooling shortens cycle
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