Explosion Prevention in Mines Welcome · 2015-08-26 · Explosion Prevention in Mines Welcome Share your experiences – management can also learn Share your concerns – others will

Explosion Prevention in Mines

Welcome

SAFA Workshop – Joy Smart Services Center – August 2015


Welcome

Today’s programme:

3 x Presenters/Facilitators

Your participation and involvement is what will make it work

Ask – Argue – Challenge – Debate – Disagree!


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


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


SAFA in a Nutshell


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


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


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…………..


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!


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!


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


Methane Explosion Videos

Methane Bubbles………

Mythbusters…………

Methane explosions in mines can cause coal dust

explosions……….

Methane Gas Bubbles Explosion!.avi

Mythbusters Blue Ice (Methane House Explosion).avi


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

Coal Dust Explosion and Suppression Modelling.avi

Comparison of suppressed and unsuppressed coal dust explosions.avi


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


The Law


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 –


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”


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"


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


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



How does a flameproof enclosure work?



How does a flameproof enclosure work?

By cooling the hot gasses as they are forced out from the enclosure







• 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







Surface finish for a flamepath face……

The surfaces of joints shall be such that their average roughness Ra

does not exceed 6,3 μm…………







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.



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



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.



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



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 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.



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).



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)



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?



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?



Test for non transmission of flame – (80% min gap)



Explosion testing 1

Explosion testing 2

Explosion testing 3

Explosion testing 4

Bang Box Demonstration.avi

Exd explosion test.avi

Explolabs cable flame transmit demo - slowed down.avi

Joy Fail.mpg



Cables

What are the requirements?

Asymmetrical

Substantially filled

1 Cable Entry

2 Branching point

3 Sealing grommet

4 Flamepath



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


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


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!

Documents

Explosion Prevention in Mines Welcome · 2015-08-26 · Explosion Prevention in Mines Welcome Share your experiences – management can also learn Share your concerns – others will