Explosion Prevention in Mines
Welcome
SAFA Workshop – Joy Smart Services Center – August 2015
Explosion Prevention in Mines
Welcome
Today’s programme:
3 x Presenters/Facilitators
Your participation and involvement is what will make it work
Ask – Argue – Challenge – Debate – Disagree!
Explosion Prevention in Mines
Welcome
Share your experiences – management can also learn
Share your concerns – others will listen
Obey some basic house rules:
Cell phones off or on vibrate – leave the room if you have to answer
No question is stupid – if you don’t ask, you won’t learn
If you think a question is stupid, you’re in the wrong room
Be prompt getting to the presentation room after the breaks
Explosion Prevention in Mines
SAFA in a Nutshell
A voluntary association of > 170 members
Exists to improve safety in Hazardous Locations – Communication!
Meets on a monthly basis – various workgroups and committees
Management – Executive – Ex Steering Committee – IS - MIE
Hold various functions around South Africa
Holds the chair of SABS TC065 – Explosion Prevention
Acts Nationally for IEC TC31 – Explosive Atmospheres
Has a core seat on SANC (SA National Committee for IEC)
Is the National Mirror Committee for the IECEx System
Participates internationally in both IEC and IECEx
Holds the Chair of AFSEC TC31
Registered with the Engineering Council of South Africa
Acts as a national forum for information sharing and debate
Explosion Prevention in Mines
SAFA in a Nutshell
Explosion Prevention in Mines
Why do we need it?
1942, a coal-dust explosion killed a full third of the workers, 1,549
people, at the Honkeiko coal mine in China
1906, an explosion at a coal mine in northern France, also known as
the “Courrières mine disaster,” killed 1,099 people, including many
children
1914, a gas explosion at the Mitsubishi Hojyo coal mine in Japan
killed 687 people, the deadliest mine accident in Japan’s history
1960, 684 miners were killed in the Laobaidong coal mine in the
northern Chinese province of Shanxi
1963, a coal mine explosion at the Mitsui Miike coal mine in Japan
killed 458 miners, while 833 others were injured
Explosion Prevention in Mines
1913, in southern Wales, a coal dust explosion killed 439 miners at
the Senghenydd Colliery, the worst mining tragedy in the United
Kingdom
1960, 435 miners were killed in South Africa’s Coalbrook mine
disaster, the country’s worst disaster in its mining history
1972, multiple explosions in the underground coal mine in Wankie
Colliery, Zimbabwe killed 426 people
1866, 388 people were killed in Oaks Colliery explosion near
Barnsley in Yorkshire, the second deadliest coal mining disaster in
the United Kingdom
1965, Dhanbad coal mine disaster in Jharkhand, India killed 375
miners
Explosion Prevention in Mines
China today…….
Official statistics for China 2014………….
Only 931 people killed in coal mines in 2014
1st time China has killed less that 1000……………..
Of the 931 deaths, 266 were the result of 47 methane explosions
This is a whopping 27.5% reduction on 2013!
However, only serious explosions have to be investigated….
A serious explosion kills 30 or more people…..
Fears have arisen that employers are hiding some deaths to avoid
being investigated…………..
Explosion Prevention in Mines
How do we calculate the costs?
On 20 April 2010, an explosion occurred on the Deepwater Horizon
oil rig in the Gulf of Mexico, destroying the rig entirely
11 workers were killed, many more injured
3.2 million barrels of oil were spilled into the ocean
Five years later:…………………
BP have agreed to pay the US government and five states $18.5bn!
This is on top of $36bn already paid!
The company in total is worth £80bn
Will be paying for the next 18 years!
Conclusion?
The cost of compliance is cheaper!
Explosion Prevention in Mines
How do we calculate the costs?
On February 18 2015, an explosion at the Exxon Mobil refinery in
Torrence California injured four workers (minor injuries)
The plant had previous citations for non compliance with safety
requirements, including the unit that caused the explosion
Fined $566,600
R6,800,000 !!!
Conclusion?
The cost of compliance is cheaper!
Explosion Prevention in Mines
Methane Explosions
What do we know about methane?
It’s colourless – you can’t see it
It’s tasteless – no taste
No odour – you can’t smell it
Approximately half the weight of air – it rises to the roof in steady air
Easily ignitable between 5-15% in air, only requires 0.21 mJ of energy
Auto ignition temperature of 580 degrees Celsius
Explosion Prevention in Mines
Methane Explosion Videos
Methane Bubbles………
Mythbusters…………
Methane explosions in mines can cause coal dust
explosions……….
Explosion Prevention in Mines
Coal Dust Explosions
Coal dust explosions are far more violent………….
Travel in the direction of the incoming air (Oxygen feed)………..
Blast wave and shock wave dislodge layers of dust
Coal dust explosions have destroyed entire mines
Best defence is prevention – no methane explosions!
Then Stonedusting
Suppressed explosion model
Explosion comparison
Explosion Prevention in Mines
Prevention Methods
The fire triangle – fuel + oxygen (air) + ignition source = BANG!
Dust explosions: Best defence: prevent methane explosions
Install stonedust barriers
Methane explosions: the number 1 defence is ventilation!
More air = less methane
Methanometers – what are the rules? Cutters vs Machine trip
Ex Protected Electrical Equipment: FLP and IS
Explosion Prevention in Mines
The Law
Explosion Prevention in Mines
The Law
The Mine Health and Safety Act, 1996 (Act No. 29 of 1996)
Regulation 10.2
The employer must take reasonably practicable measures to prevent
persons from being injured in any hazardous location as a result of
fire, explosion or the ignition of gas, dust, mist or vapour. Such
measures must ensure that –
Explosion Prevention in Mines
The employer must ensure that….
b) only explosion protected apparatus and systems certified for use in
a hazardous location in accordance with the South African National
Standard ARP 0108: 2005, "Regulatory requirements for explosion
protected apparatus", are used in any hazardous location
c) the selection of explosion protected apparatus used in any
hazardous location is done in accordance with SANS 10108:2005
"The classification of hazardous locations and the selection of
apparatus for use in such locations”
Explosion Prevention in Mines
The employer must ensure that….
d) the installation, inspection and maintenance of explosion protected
apparatus used in a hazardous location is carried out in accordance
with
SANS 10086-1 2005 "The installation, inspection and maintenance of
equipment used in explosive atmospheres Part 1 : Installations
including surface installations on mines”
and SANS 10086-2 2004 "The installation, inspection and
maintenance of equipment used in explosive atmospheres Part 2:
Electrical equipment installed underground in mines"
Explosion Prevention in Mines
The Law
Hazardous Locations:
According to SANS 10108:
Any location in underground coal mines where, under normal
operating conditions, there is a continuous presence of flammable
gas, measured at a concentration of 0,5% (volume fraction), or more,
in the general body of the air, including
a) a return airway
b) any location not more than 180m from any working face, and
c) any other location determined by risk assessment,
Shall be regarded as a hazardous location in terms of the relevant national
legislation
Explosion Prevention in Mines
Flameproof Equipment
What is a flameproof enclosure?
An enclosure in which the parts which can ignite an explosive
atmosphere are placed,
and which can withstand the pressure developed during an internal
explosion of an explosive mixture without damage,
and which prevents the transmission of the explosion to the explosive
atmosphere surrounding the enclosure
A flameproof enclosure is neither gas tight nor is it waterproof.
The constructional requirements are set out in SANS 60079-1
Explosion Prevention in Mines
Flameproof Equipment
How does a flameproof enclosure work?
Explosion Prevention in Mines
Flameproof Equipment
How does a flameproof enclosure work?
By cooling the hot gasses as they are forced out from the enclosure
Explosion Prevention in Mines
Flameproof Equipment
Explosion Prevention in Mines
Flameproof Equipment
Explosion Prevention in Mines
Flameproof Equipment
• Important requirements for flamepaths:
• Requirements of 60079-1: 25mm length : gap = 0.5mm max
12mm length : gap = 0.4mm max
Cover thickness
Material under the counterbore
Through hole diameter
Engaged thread length, type and quality
Material around the bolt
Bolt type and thread
Explosion Prevention in Mines
Flameproof Equipment
Explosion Prevention in Mines
Flameproof Equipment
Explosion Prevention in Mines
Flameproof Equipment
Surface finish for a flamepath face……
The surfaces of joints shall be such that their average roughness Ra
does not exceed 6,3 μm…………
Explosion Prevention in Mines
Flameproof Equipment
Explosion Prevention in Mines
Flameproof Equipment
Explosion Prevention in Mines
Flameproof Equipment
Test requirements – applies to all designs – (new or changed)
All designs must be tested by a SANAS accredited test laboratory
All new (or changed) equipment may must be type tested.
Subsequent production then takes place either under a quality
system or a batch testing process.
Explosion Prevention in Mines
Flameproof Equipment
Type testing tests the design for compliance with the standard.
Production commences under the manufacturers quality system
(audited by a SANAS accredited laboratory/certification system)
Initial and Surveillance audits of the manufacturer are carried out
regularly
Manufacturer is granted a “licence” or “mark” by the
laboratory/certification body
The type certificate (IA) contains no equipment serial number, and
The manufacturer can then manufacture the product for 10 years
Explosion Prevention in Mines
Flameproof Equipment
Batch testing done to SANS 96 and covers manufacturers with no
audited Ex quality system
Manufacturer must submit the full batch of product to the laboratory
According to the SANS 96 sampling tables, the lab randomly pick the
samples for test from the batch
The samples must undergo full testing as per the standard, which are
equal to the type test.
All samples must pass the test. The full batch is then approved, and
the serial numbers are entered on the IA certificate.
Explosion Prevention in Mines
Flameproof Equipment
Test requirements:
Documentation:
Drawings detailing all relevant flamepath information, including:
FLP gaps and flamepath lengths, material thicknesses etc…
Threaded hole detail (type of thread, depth, diameter etc…)
Manufacturers instructions for safe installation, operation, maintenance
Sample enclosure:
Populated with mock up components
All gland entries or openings blanked off (with FLP devices)
Facilities for gas entry and exit and ignition device
Machined to worst case scenario as per standards and drawings
Explosion Prevention in Mines
Flameproof Equipment
The lab examines the drawings for compliance with the standard
The sample is then verified for compliance with the drawings
Physical testing as required by the standard in the following
sequence:
Determination of the explosion pressure (reference pressure)
Overpressure test
Test for non-transmission of an internal explosion
Other tests as required – windows, cement, seals and grommets for
ageing, temperature rise tests, impact tests etc. etc.
Explosion Prevention in Mines
Flameproof Equipment
Explosion Pressure determination test:
The enclosure is filled with an explosive mixture of methane and
hydrogen, and adjusted for altitude.
The enclosure is made as gas tight as possible.
The explosive mixture is ignited and the pressure generated is
measured.
The potential for pressure piling is considered.
Explosion Prevention in Mines
Flameproof Equipment
Overpressure test.
The overpressure test verifies the structural integrity of the
manufactured enclosure.
The pressure applied is 1,5 times the reference pressure (for
fabricated welded units); or
4 times the reference pressure for enclosures not subject to routine
overpressure testing (castings or machined from solid).
Explosion Prevention in Mines
Flameproof Equipment
Overpressure test:
The tests are considered satisfactory if the enclosure suffers no
permanent deformation or damage that would invalidate the type of
protection.
In addition, the joints shall in no place have been permanently
enlarged.
(The enclosure undergoes an FLP inspection after the test)
Explosion Prevention in Mines
Flameproof Equipment
Bolt torque on flameproof enclosures:
All bolts are grade 12,9
A 12mm diameter bolt requires 145 Nm of torque to fasten properly
A mild steel enclosure threaded hole will suffer permanent damage
around 115 Nm
So why use grade 12,9 bolts?
Explosion Prevention in Mines
Flameproof Equipment
Typically, in an overpressure situation, the first thing to give way is
the bolts – the heads come off.
In cases where this has happened at Joy, the velocity demonstrated
by such bolt heads could have injured personnel.
Bolt shrouding – is it legally required?
Explosion Prevention in Mines
Flameproof Equipment
Test for non transmission of flame – (80% min gap)
Explosion Prevention in Mines
Flameproof Equipment
Explosion testing 1
Explosion testing 2
Explosion testing 3
Explosion testing 4
Explosion Prevention in Mines
Flameproof Equipment
Cables
What are the requirements?
Asymmetrical
Substantially filled
1 Cable Entry
2 Branching point
3 Sealing grommet
4 Flamepath
Explosion Prevention in Mines
Flameproof Equipment
Typical problems with flameproof equipment.
Missing or loose bolts – common but easy to fix
Damaged threads on the enclosure
Dirt between the flanges – gap too big
Damage to flanges
Missing cable glands or blanks – Including plastic plugs
Explosion Prevention in Mines
Staying Alive
Don’t be complacent, don’t be lazy. Enough people have died
Don’t just do what others do and assume they know better
Don’t give in to peer pressure
Ask your supervisor for a copy of SANS 10086-2
Read it and understand it – ask questions! Never stop learning!
Recognize that you are not the only person working on the
equipment
Explosion Prevention in Mines
Staying Alive
Take this thought home with you:
99.99% of flameproof equipment is safe when it arrives at the mine
It’s your job to keep it that way!