220 likes | 423 Views
Agenda. Why me?Design Guide ProjectRegulatory Responsibility AS4360 approach to managing riskSummary of Key Control Measures. Why me?. RiskTech Pty LtdIndependent risk management consultancyClients include:Weston MillingInghamsManildra GroupRidley. Peter McGeeBE (Env)Masters (FSE)Speci
E N D
1. Combustible Dusts – A Design Guide 2008 Australasian
Milling Conference
2. Agenda Why me?
Design Guide Project
Regulatory Responsibility
AS4360 approach to managing risk
Summary of Key Control Measures
3. Why me? RiskTech Pty Ltd
Independent risk management consultancy
Clients include:
Weston Milling
Inghams
Manildra Group
Ridley Peter McGee
BE (Env)
Masters (FSE)
Specialise in asset protection
Focus on insurable risk
4. Design Guide Project Inghams, Ridley, Weston Milling
Confusion regarding selection of electrical apparatus
Scope:
Design considerations for managing combustible dusts
Not limited to selection of electrical apparatus
Focused on a new mill, but can also equally be applied to an upgrade
Also provides ability to audit against for non-conformances
5. Design Guide Project Minimum Requirements
Driven primarily by regulation
Also includes common sense / easy to achieve controls such as maintenance and management controls e.g. housekeeping, no smoking rules and hot work permits.
Best Practice requirements
Driven primarily by insurance industry guides (FM Data Sheets, NFPA standards)
6. Regulatory Responsibility Key requirement:
Electricity Acts ? AS3000 (Wiring Rules)
? appropriate electrical apparatus in hazardous areas ? relevant hazardous area standards (pre-curser to AS61241)
7. Regulatory Responsibility Also OH&S Acts and Duty of Care to provide safe workplace
Only prescribed requirement in managing combustible dusts relates to electrical equipment
8. Hazardous Areas Standards revised/updated
Major change – separation between combustible dusts and flammable vapours
Complete new set of standards relating to combustible dusts – AS61241 series
9. AS61241 Key changes:
Zoning: 20, 21, 22
Dust Layers
Provides fire load;
Provides source for secondary explosion
11. Electrical Apparatus Primary device Ex tD
Also known as IP6X – similar to DIP.
Other devices include Ex mD, Ex pD, Ex iD.
NB: similar equipment in zone 20, 21, 22.
12. Selection of Electrical Apparatus – abridged version Where:
Dust Layers < 7.5mm
Max surface temp of equip 75°C < minimum dust layer ignition temp
Then:
Install IP6X, or IP5X for non-conductive dusts
IP 5X & 6X
13. Combustible Dusts – The Hazard Explosion can occur when:
Combustible dust present;
Suspended in atmosphere in correct proportions with air (O2); and
Ignition source is introduced
14. AS4360 Approach Risk = Likelihood x Consequence
Reduce Likelihood:
Avoid explosive atmosphere – i.e. avoid dust
Avoid ignition sources
Reduce Consequence:
Control consequences – i.e. manage explosion
15. Design Guide – Key Controls Plant Layout and Building Materials
Ignition Source Controls
Electrical apparatus (already addressed)
Dust control
Explosion Control
Specific equipment
Management controls and maintenance
16. 1. Plant Layout and Building Materials Limit the size of zones
Prevent dust accumulation
Exclude services (e.g. steam) from zoned areas
Limit access to zoned areas
Egress
Non-combustible building materials
17. 2. Ignition Source Controls Hot work - more strict controls in zoned areas
Static – maintenance continuity testing
Mechanical friction – prevent product accumulation at bearings
Foreign materials – cleaning equipment
Thermal decomposition
Process heat – failsafe thermostat controls
Hot surfaces – all surfaces < 100°C
18. 4. Dust control Reduce dust in suspension below the lower explosive limit (anywhere from 50-500g/m3)
Design is crucial:
Volume – sufficient to extract dust at pick up point;
Velocity – avoid deposits in ductwork
Air to cloth ration – consideration for maintenance
Safety factor
Extract at every point of change in product flow
Redesign when changes are made
19. 5. Explosion control Explosion venting should be primary method.
Vent externally;
Ensure no structures/equipment exposed
Suppression, containment, isolation, inerting other alternatives
20. 6. Specific Equipment e.g.
Bucket Elevators
Under-speed detection
Track control
Explosion venting
Grinding
Magnetic separation
Air/gravity separation
Monitoring for temperature and flow of air and grain
21. 7. Management Controls Housekeeping
Maintain dust layers <5mm at all times
Best Practice – audit program measuring layer thickness
Management of change
Training
Maintenance
Static earthing
e.g. painting over explosion vents
22. Summary Only regulatory requirement relates to selection of electrical apparatus
Electrical apparatus are only one of a number of design issues to be considered when controlling combustible dusts
Design changes provide the opportunity to consider these issues
23. Lets help avoid this!