Industrial Ventilation notes

Dr Bromwich has had over 25 years experience in the design and evaluation of industrial ventilation systems:

  • Evaluation of ventilation systems in mines in the Northern Territory Department of Mines and Energy. He also ran “Ventilation Officer’s Course”  for mine managers.
  • Designed, built and commissioned a radon chamber for calibrating radon progeny instrumentation for use in underground mines. It was very differnmt from the ones at the Atomic Energy Comission at Lucas Heights in Sydney or at the Australian Radiation Laboratories in Melbourne (both organisations are now ARPANSA).
  • MSc Thesis at the London School of Hygiene and Tropical Medicine “Control of Solvent Vapours in a Paint Factory”, researching and evaluating novel approaches to industrial ventilation
  • At Griffith University he taught the  principles of industrial ventilation to over 2000 undergraduate students over 16 years as part of an introductory occupational hygiene subject.
  • Also ran a course for 4th year engineers and postgraduates “Ventilation for Contaminant Control”. Here, students were divided into “companies” and developed the skills to evaluate existing system in industry and present a costed “tender document” to solve the design problems.
  • He also wrote the revised section on Industrial Ventilation in the 2007 standard occupational hygiene text in Australia “Principles of Occupational Health & Hygiene – A Basic Guide for the Occupational Health & Safety Practitioner ” (Allen & Unwin 2007)
  • Short courses on Industrial Ventilation were conducted for the Queensland Department of Employment and Industrial Relations (Workplace Health and Safety) in 2005 and 2006.

Industrial Ventilation Laboratory

This is now historical – the laboratory is now offices, though the monitoring equipment has been kept.

A laboratory was developed at Griffith University for teaching and research

  • The Green Machine – a full scale industrial ventilation teaching rig and hoods
  • A half scale  experimental fume cupboard
  • A 4.8 m low speed glass  wind tunnel, with mannequin,
  • Two industrial ventilation teaching rigs (ex Worksafe Australia, refurbished)
  • Precision Manometer and Pitot tubes
  • Smoke Generators
  • Bruel & Kjaer (Innova)  1302 Multigas analyser and SF6 dosing system
  • HeaVent design software (Steven Guffey)

Industrial Ventilation

  • Evaluation of existing local exhaust ventilation
  • Design of industrial ventilation systems, concentrating on hood design

The Green Machine

The Green Machine is constructed from standard industrial ventilation ducting and bends, with custom fans, duct junctions air cleaning devices (filter, cyclone), many hoods and a stack. It also has a pneumatic conveying system. Some elements (like junctions and bends) have versions that are deliberately badly designed to demonstrate the effect of bad design. Most elements are powder coated green.

  • Fan and stack

Most elements of the green machine are wheeled to permit easy placement and storage. The stack almost touches the ceiling, so is rarely used inside as it blows the ceiling tiles about. The fan normally vents through a plate on the window as smoke from disco smoke generators or smoke tubes would make the laboratory uncomfortable. The fan is a radial bladed centrifugal fan driven by a three phase motor. A control unit synthesis three phases from a single phase supply, permitting the fan to run forwards and backwards at any speed.
Fan motor and synthesised 3-phase control unit

  • Slot hood

A thin plywood sheet coated with blackboard paint has a cut-out for the hood. It is placed so that airflow is along its surface and almost unaffected by its presence. This permits the airflows to be visualised with a smoke tube and drawn on the plywood. A air speed meter is moved along the air trajectories and contours at 0.5 m/s (reasonable capture of many contaminants) and 0.2 m/s (marginal capture) of contaminants. Flanges can be added to increase the capture distance, but this may obstruct tasks.
See Hoods for many more examples of hoods used with the Green Machine.

  • Experimental Fume Cupboard

A half scale experimental fume cupboard was constructed to simulate a wide range of good and bad designs, plus novel features not found on commercial fume cupboards.
Features include

  • Aerodynamic surface including sill, sash and surrounds of face can be quickly changed.
  • The vertical angle of the sash can be changed
  • The floor of the fume cupboard has 3000 holes to allow it to be used as a downdraft fume cupboard
  • The baffle position and gasps can be readily changed. Fully closed, the fume cupboard becomes downdraft fume cupboard.
  • Slots on the fume cupboard exhaust can be changed
  • Many parts are transparent for visualising airflows

To come: pictures

Low Speed Wind Tunnel

  • The wind tunnel took 4 years to design and two weeks to construct. The sides and top are laminated glass and the frame is powder coated steel. The tunnel is in two sections, each 2.4 m long. The opening is 800 x 800 mm. Each section can be wheeled through a doorway and taken in a lift.
  • The white cowl is made from expanded PVC, a material that can be welded with care using a special hot air gun.
  • In the picture, an Innova 1302 Multigas analyser capable of detecting ppb of SF6 (sulphur hexafluoride) is on the bench. A combination of SF6 tracer gas and smoke is used to quantify and visualise air flows.
  • A special plywood section can be seen in the middle of the wind tunnel. It is used for cross draft studies with hoods.
  • The wind tunnel is connected to a duct connect to a fan and stack five floors up. This ensures that trace gas contaminated air is not re-entrained in the incoming air.
  • The font cowl is surprisingly light and can be lifted with one hand.
  • Each section is easy to transport. Here it is being loaded into a passenger lift.
  • SF6 tracer gas and view under wind tunnel of turntable.
  • 100 mm PVC pipe conducts smoke from a disco smoke generator into the wind tunnel. This is facilitated by a “Lazy Susan” bearing on the turntable.
  • Simple connection of a smoke generator to the wind tunnel was found not to work well. A small air gap is needed in front of the smoke generator

Simple demonstrations of airflow past workers:

  • “Bruce” is upwind of the contaminant source, but air is entrained and he received a face full of smoke.
  • Note the classic eddies at the top of the picture.
  • Paradoxically, when Bruce is downwind, little of the smoke gets in his face. This is not always the case.
  • When Bruce is side-on to the airflow, almost no smoke gets in his face.
  • Tracer gas studies (picture on right) show a 200 fold reduction in exposure.
  • Bruce is made of flat plywood and this enhances the effect of being of upwind, downwind and side on to an airflow.