management feedback review sept 2014 - sacma feedback 27 5 2015.pdf · management feedback review...

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Management Feedback Review –

Sept 2014

CAP LAMP FEEDBACK MAY 2015

CM & EE Feedback session 27 May 2015

Presented by Darin Kruger

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Cap lamp Feedback May 2015

Agenda:

Failures and Vendor Feedback

Investigations

Potential Risk and Challenges

Findings and Recommendations

Conclusion & Way Forward

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Failures:-

• Typically a venting occurrence.

• All the units that we are aware of were on charge

(plugged into rack).

• No injuries or immediate threat to safety reported to

date.

• No damage to charging equipment reported to date.

• Lamp battery pack destroyed.

• Vendor advised following causes:

• Mechanical handling

• Charging voltage ripple

• Poor maintenance

• Battery life exceeded (500 cycles)

• Overcharging

• Over discharging

• High operating temperatures

To our knowledge all failures indicated above were on the

standard Safe-Lite unit supplied by Schauenburg.

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Investigation:-

A number of tests were carried out with a third party test facility to establish the main possible

causes of failures as against the extensive list the vendor had indicated.

•Mechanical handling – This remain a potential cause but has a low probability as these lamps

are used extensively across the platinum industry and only recently have the failures become

so evident.

•Charging voltage ripple – The vendor advised these lamps could be used on the existing lead

acid charging racks. We have put smoothing circuits onto most of the AAP charging racks to

get within the vendors recommendations. A number of tests indicated this potential cause is a

medium to high priority and has a bigger impact as the cells age.

•Poor maintenance – Based on our findings this was found to be a low probability issue as

most of the issues found on the failed lamps we inspected had no direct impact on the failure.

•Battery life exceeded (500 cycles) – This issue along with cyclic stress and intercalation of

lithium ions is potentially the major cause of failures.

•Overcharging – From our findings with the vendors recommended power suppliers this is

deemed a low probability.

•Over discharging – From our investigations the vendors circuit takes the low voltage into

account and cuts out 2.9V (TJL recommend 2.75V)

•High operating temperatures – The recommended range is -20˚C to +55˚C, from our findings

we believe this ambient temperature was exceeded and a very low probability.

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Investigation Issues for Concern:-

The Lithium Ion battery technology has been around for some years now but a great deal of study and

investigations into the technology, chemical reaction and environmental effects are being conducted at

present. What we are aware of is the following:

•The batteries have a limited shelf life even when stored strictly in accordance with OEM

recommendations - ambient 25˚C at 60% of charge voltage.

•The charge and discharge rate have a direct impact on the operating temperature of the cells which in

turn impacts the operational life of the Lithium Ion cells. The focus here is the charging racks and the

effect of ripple on the battery packs due to use of older lead acid charger racks.

•The buildup of “crystals (Dendrites)” on the insulating medium between the battery materials impairs the

effectiveness of the insulation performance and this buildup seemingly facilitates the breakdown of the

insulation and resulting short circuit.

•The over current “external protection” as designed by the cap lamp vendors and the Lithium Ion cells

cannot stop the chemical reaction and thermal run away once it has started, thus the present cell design

which incorporates explosive venting caps and internal PTC components.

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Investigation Issues for Concern:-

Temp (˚C) Reaction Identified Energy (J/g) Comment

120 - 130 Passivation layer 200 - 350

Passive layer breaks - solubilisation

starts bellow 100˚C

130 - 140 PE seperator melts -90 Endothermic

160 - 170 PP seperator melts -190 Endothermic

200 Solvents - LiPF6 300 Slow kinetic

240 - 250 LiC6 + binder 300 - 500 steady kinetic

240 - 250 LiC6 + electrolyte 1000 - 1500 Violent reaction

200 - 230

Positive material

decomposition 1000 Violent reaction

TABLE 1. Thermal stability of components used in a Lithium-ion battery. (SOURCE: Saft)

Due to the construction of the Lithium battery and the energy stored in

the cell there is an ongoing risk of a thermal run away situation.

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Investigation Design Features Cont.:-

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Charging and discharge characteristics

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Lithium Dendrite between anode and insulating material layer

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The electrodes of Lithium cells expand and contract during charging and

discharging due to the effect of the intercalation of the Lithium ions into and

out of the crystal structure of the electrodes.

This cyclic stresses on the electrodes will ultimately lead to the following:-

• Cracking of the particles making up the electrode

• Increased internal impedance as the cell ages

• Breakdown of the anode SEI layer

• Overheating and immediate cell failure.

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Various battery chemical makeup and breakdown characteristics

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Potential Risks & Challenges:-

• The Platinum mining industry has a significant Schauenburg cap lamp asset base.

• Many have reached a critical age where potential venting of failed Lithium Ion cells are likely to

occur during the charging cycle.

• This venting can result in a fire which could spread to other lamps in the cap lamp room under

extreme conditions.

• Vendor has been fully engaged in the process and they have been very co-operative during the

tests and investigative work by Anglo American Platinum.

• Other areas to be addressed for improved reliability of the current caplamps include:

o Improve storage procedures – temperature, storage charge, top up charge.

o Handling and mechanical shock and damage

o Charging ambient temperature control

o Over charging / Over discharging and associated extreme operating temperatures

o Improved technical specification and detailed data sheet.

o Review of emergency preparedness.

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In Conclusion, Way Forward:-

• Methodology and approach to implementation and roll out of new technologies in our mines.

• Industry work groups to address common challenges and issues.

• Cap Lamp Specific:-

• Replace existing cells with new chemical combinations.

• Track life cycle of the batteries for future replacement when due (don’t exceed life cycle and

understand the risks)

• Further investigation into the reduced charging voltage.

• Further investigation of thermal conditions under charging and discharging and improved thermal

protection.

• Investigate new and developing battery technologies.

• Improved emergency preparedness.

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THANK

YOU

management feedback review sept 2014 - sacma feedback 27 5 2015.pdf · management feedback review...

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