1 / 31

BASIC PRINCIPLES IN OCCUPATIONAL HYGIENE

BASIC PRINCIPLES IN OCCUPATIONAL HYGIENE. Day 2. 10 - VENTILATION. Dilution Ventilation. Reduces background concentration by adding fresh, uncontaminated air Small amounts low toxicity widely dispersed contaminants Diluted not removed from source

lovee
Download Presentation

BASIC PRINCIPLES IN OCCUPATIONAL HYGIENE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. BASIC PRINCIPLES IN OCCUPATIONAL HYGIENE Day 2

  2. 10 - VENTILATION

  3. Dilution Ventilation • Reduces background concentration by adding fresh, uncontaminated air • Small amounts low toxicity widely dispersed contaminants • Diluted not removed from source • Opening a roller door, blowing air into a room with a large fan

  4. Local Exhaust Ventilation (LEV) Systems Source: Adrian Hirst

  5. LEV • Most effective • Removes contaminant at source • Requires • Proper design • Maintenance • Training in proper use

  6. General Features of an LEV System Source: Adrian Hirst

  7. General Considerations Source: HSE

  8. Inlets/Hoods

  9. Hoods –Critical Component Main reasons why systems fail to protect • Incorrect type of hood is chosen (and could never provide sufficient protection) • The airborne contaminant isn’t contained or captured • LEV hood design doesn’t match the process and source(s) • Insufficient airflow (various reasons) Source: HSE

  10. Local Exhaust Ventilation Hoods Capture mobile Source: HSE

  11. The Three Basic Types of LEV Hood Enclosures Full Partial, small Room Partial, large Receiving Hot Capturing Source: HSE

  12. Enclosing Hood Source: HSE

  13. Capturing Hoods Process takes place outside hood, hood-induced airflow has to “capture” contaminant-laden air Side-draught captor hood (adapted from Hemeon’s Plant and Process Ventilation) Source: HSE

  14. Capturing Hoods The process, source and contaminant cloud are outside the hood Hood has to generate sufficient airflow at and around the source to ‘capture’ and draw in the contaminant-laden air (adapted from Hemeon’s Plant and Process Ventilation) Source: HSE

  15. Capturing Hoods – Interrelated Properties • Capture velocity, distance and zone • Process induced air movement and draughts • Airflow, velocity contours and flanges • Capture ‘bubbles’ • Capture curve • Capture zone and Working Zone Source: HSE

  16. Capture of vapour-laden air: evaporation Air velocity required at this point to “capture” vapour-laden air ~0.5 metres per second (m/s) Source: HSE

  17. Capture of vapour-laden air: drum filling Air velocity required at this point to “capture” vapour-laden air ~2.5 metres per second (m/s) Source: HSE

  18. Types of LEV used for Various Processes Source: HSE

  19. Capture Zone / Capture Bubble

  20. Movable Capturing Hood – Capture ‘Bubble’ Capture bubble Source: HSE

  21. Capture ‘Bubble’ Varies in Size Source: HSE

  22. Capturing Hood Capture ‘Bubble’ Source: HSE

  23. Capture Zone must Encompass Working Zone Capture zone Working zone Source: HSE

  24. Ductwork Ductwork carries the extracted air and the contaminant from the inlet to the air cleaning device. • Velocity important • Should be sufficiently strong • Well supported and capable of withstanding normal wear and tear • The number of changes of directions should be kept to a minimum • Should be made smoothly • Access to ducting may be required

  25. Duct Velocity Source: HSE

  26. Air Cleaners - Filters Source: Adrian Hirst

  27. Air Cleaners - Cyclones Source: Adrian Hirst

  28. Air Cleaners - Wet Cyclone & Induct Spray Source: Adrian Hirst

  29. Air Movers - Fans Axial Centrifugal Source: US EPA

  30. Discharge to Atmosphere Source: HSE

  31. Maintenance, Examination and Testing of Ventilation Systems In order to function correctly the LEV must be in good working order • Legal requirements • Regular maintenance • Thorough examination and testing

More Related