Safety practicesto avoid dust explosions

W.V.PETER HUNTDIRECTOR & PRINCIPAL CONSULTANT,

WHAMCORP PTY LTDwww.whamcorp.com.au

BOARD MEMBER & PAST PRESIDENT,

AUSTRALASIAN INSTITUTE OF

DANGEROUS GOODS CONSULTANTS

www.aidgc.org.au

SUGAR DUST EXPLOSION AND FIRE(14 Killed, 36 Injured)

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Why?• Modification of conveyor which then confined dust

• Dust accumulated on floors and horizontal surfaces

• Inadequate emergency procedures (alarm & evacuation)

Due to a whole variety of causes, includingLack of management understanding & awarenessno training in dust hazards (supervisors & operators)no proper maintenancelack of control of changeno proper housekeepinginadequate alarm, evacuation, fire suppression

www.csb.com search for “dust” for incident reports, videos etc.

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What the law says – 2 steps.WHS ACT – Section 17

A duty imposed on a person to ensure health and safety requires the person:

(a) to eliminate risks to health and safety, so far as is reasonably practicable, and

(b) if it is not reasonably practicable to eliminate risks to health and safety, to minimise those risks so far as is reasonably practicable.

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WHS RegulationPart 3.1 Managing risks to health and safety

Clause 33 Specific requirements must be complied with

Any specific requirements under this Regulation for the management of risk must be complied with when implementing the requirements of this Part.

Examples.1 A requirement not to exceed an exposure standard.2 A duty to implement a specific control measure.3 A duty to assess risk.

i.e. if you’re told, then just do itWhamcorp Pty Ltd 5

Clause 34 Duty to identify hazards

A duty holder, in managing risks to health and safety, must identify reasonably foreseeable hazards that could give rise to risks to health and safety

Dust from organic material or metals has a foreseeable and well known hazard of fire or explosion, so you mustidentify potential sources of dust andidentify its properties with respect to dust explosion

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Risk control measuresWHS Regulation

Clause 36 - Hierarchy of control measures (3 steps, not 5)

If unable to eliminate risk, must control by

1) One or more of substitution, isolation, engineering controls

2) If risk remains, then administrative controls

3) If risk remains, then suitable PPE

Note, can use a combination to minimise risk

Clause 37 – Maintenance of control measures

Clause 38 – Review of control measuresWhamcorp Pty Ltd 7

Sugar elevator explosion, 24 Apr 2004At a 5- storey concrete building and 30 silos, the force of the blast tore the elevator casing open, smashed windows, damaged explosion arrestors, and caused extensive caramelisation in a 30-tonne storage bin. The building suffered some structural damage.

Hazards - mechanical sparks are well known ignition sources and elevators are well known for stirring up dust by air movement.

Control measure - elevator was designed with tracking monitoring to ensure wear would not allow the steel buckets to contact the steel casing and generate sparks

The cause was failure to maintain the control measure (tracking device) which allowed moving steel components to strike the steel casing generating sparks (today – see WHS Reg Cl 36 & 37)

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Back to WHS Act

In this Act, reasonably practicable, in relation to a duty to ensure health and safety, means that which is, or was at a particular time, reasonably able to be done in relation to ensuring health and safety, taking into account and weighing up all relevant matters including:

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Relevant factors(a) the likelihood of the hazard or the risk concerned occurring, and

(b) the degree of harm that might result from the hazard or the risk, and

(c) what the person concerned knows, or ought reasonably to know, about:

(i) the hazard or the risk, and(ii) ways of eliminating or minimising the risk, and

(d) the availability and suitability of ways to eliminate or minimise the risk, and

(e) after assessing the extent of the risk and the available ways of eliminating or minimising the risk, the cost associated with available ways of eliminating or minimising the risk, including whether the cost is grossly disproportionate to the risk.

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Reasonable knowledge about dust

(i) the hazard or the risk:any organic material or metal (anything which will burn or oxidise) in the form of dust presents an explosion hazard

(ii) ways of eliminating or minimising the risk:all the things in Step 1 of the hierarchy of control, including

isolation and good engineering design toprevent – e.g. eliminate ignition sourcesmitigate – e.g. explosion relief or suppression

in combination with Step 2, administrative control, includinggood housekeeping.

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WEST PHARMACEUTICAL SERVICES, 2003The Kinston NC plant manufactured rubber drug delivery components, so the cleanliness of the facility was a high priority (“GMP”, like food hygiene requirements).

As the zone above the suspended ceiling had a slightly lower pressure than the room it covered, a portion of the room air was drawn through the ceiling into the open space above.

Although the cleaning crew continually cleaned the areas around the equipment, there was a layer of polyethylene dust on top of the suspended ceiling, confirmed as the fuel for the dust explosion which killed 6 workers and injured 38, including 2 firefighters.

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West Pharmaceutical -damage was so extensive that the ignition source could not be identified

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Law again - Code of practice (WHS Act, Sec 275)

(2) An approved code of practice is admissible in the proceeding as evidence of whether or not a duty or obligation under this Act has been complied with.(3) The court may:(a) have regard to the code as evidence of what is

known about a hazard or risk, risk assessment or risk control to which the code relates, and

(b) rely on the code in determining what is reasonably practicable in the circumstances to which the code relates.

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Any CoP for combustible dusts?“Managing risks of hazardous chemicals in the workplace code of practice” Page 23 has 2 sections:

Dust explosion risksEffect of particle size on dust explosion risk

It refers to (i.e. incorporates):• AS/NZS 4745: Code of practice for handling combustible

dusts (and this references EN/ISO, NFPA and VDI standards)

• AS/NZS 60079.10.2: Explosive atmospheres – Classification of areas – Combustible dust atmospheres

So there is plenty of guidance available to you and the courtsWhamcorp Pty Ltd 15

Appendix I (2 pages) lists industries having fire & explosion risks, including combustible dusts

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e.g. half the identified agricultural industry processes are listed for dust

You’re not expected to read the table

“But the dust is not so thick in our plant”

NFPA Standard 654 includes a variety of good practices to prevent dust explosions. US CSB report of the polyethylene dust explosion:“The standard states that dust accumulations of just 1/32 of an inch thick (less than 1 mm) - an amount less than the thickness of a dime - create the conditions for a dangerous explosion and must be removed. “

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“The thickness of a dime”

US DIME AUS 5c US DIME AUS 5c

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A 5c piece! Surely not a serious hazard??

The Standard explains that a 1/32-inch (< 1mm) dust accumulation over the floor area of a room, if uniformly suspended, can create a 10-foot-high (3 m) cloud of optimal explosive concentration.

It warns that accumulations may be hazardous when they exceed just 5 percent of the floor area (e.g., on exposed beams and joists).

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Back to WHS Regulation

Cl 355 Specific control—fire and explosion

A person conducting a business or undertaking at a workplace must, if there is a possibility of fire or explosion in a hazardous area being caused by an ignition source being introduced into the area, ensure that the ignition source is not introduced into the area (from outside or within the space).

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Hazardous area classification

Needed to determine;

• If a hazardous area (HA) exists

•Extent and zoning of any HA

•Standard of electrical equipment in HA

•Hot work permits

• Input to change management

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Keep electric motors and equipment clean

Dust of any sort accumulating on electric motors, switchgear etc. acts as an insulator and can cause the equipment to overheat. Combustible dust overheating can cause a fire, which may lead to air movement stirring up dust which then explodes on ignition

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Hygiene and safety

HYGIENE requires cleanliness to avoid product contamination, so if dust falls on the floor, it’s not put back into the process and you can clean it up later, even much later.If it is constantly spilling, that does not matter.

SAFETY requires elimination of risk by avoiding dust outside equipment designed to hold it,so if dust falls on the floor, it has to be cleaned up immediately.If it is constantly spilling, action to prevent must be taken

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Supervisors & managers

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Hygiene and safety standards

Hygiene and safety are not incompatible

A common standard of control is simplest and best and must include:

• Design of process and equipment

• Operation (procedures and practices)

• Maintenance

• Management and supervision

• Control of change (modifications)

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Are there any questions

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