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d Trigger Action Response Plans in Trigger Action Response Plans in Underground Coal MinesUnderground Coal MinesTips, Tricks and PitfallsTips, Tricks and Pitfalls

David Cliff

Minerals Industry Safety and Health Centre

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Typical TARPTypical TARP

Level 1 - Normal Level 2 - Abnormal – tell Mgt Level 3 - really abnormal – tell Mgt Level 4 - Oops ! - Evacuate

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Fundamental principles

Simple and Robust Adequately resourced – personnel and equipment Focus on prevention and early detection -

validation, clarification and remediation Requires detailed knowledge of normality Triggers not set in stone should be reviewed and

revised as experience grows or conditions change High quality mine monitoring information Do not be afraid to ask for advice If the TARP mandates an action it must be carried

out promptly

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Establish range of normal values

Establish normal time dependence of concentrations and other indicators

Different norms for different circumstances and environments eg CO make vs retreat rate or face ventilation Q

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CO Make vs face advanceCO Make vs face advance

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0

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0 5 10 15 20 25

Tim e since se aling (h rs)

512 401 -402

Moura

512 vs 401-402

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Advisory Level

Action by ventilation officer and technical services personnel + inspections

Validation of readingsExtension of monitoring to other locations,

increase frequency and complexityInspection of area for leakage and other

abnormalityPrepare for inertisation or other control action

eg fly ash injectionSeek external advice as necessaryMonitor rate of change with time

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Recent episodes have been catalysed by the prolonged presence of oxygen in goaf areas where normally it would not be were it not for mining problems.

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Alert level

Advise mine management of potential for evacuation

Initiate control measures such as inertisation Prepare for evacuation

No unnecessary work undergroundPrepare for quick sealing of area of concernPeople to stay in close contact with surface

Monitoring frequency adjusted to rate of change of atmosphere.

Monitoring analysis needs to allow for any control measure effects – gas displacement or dilution

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Evacuation level

Orderly evacuation Key criteria is the potential for harm to the

workforce Timed to allow protection of equipment,

maintenance pumps etc Emergency sealing carried out if necessary

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Re-entry criteria

Conditions established objectively prior to incident – eg by risk assessment

May be modified based upon risk assessment Criteria for limited re-entry may be different to

those for return of work-force underground. Inertisation and other controls may mask

behaviour without necessarily controlling the incident.

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TARP actions

For all mandatory actions within TARPS there must be close out by a specified time.

Actions should not be just :Tell VO of gas concentrations – no other action

required by VOMine Manager notified- no other action required

Need audit of actions Proper record keeping

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TARP criteria

Values not set in stone – should be regularly reviewed Minimum at end of each longwall block or

extraction area.If situation stabilises without getting worse

consider revising advisory/alert TARPs.Avoid glib explanations and production driven

demand to change TARPs.Changes to TARPS should be documented and

justified.Changes may be up as well as down.

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TARP criteria

Basis for action should be severity of incident First level trigger is abnormality – significantly

above background level Second level trigger is significant and

worsening abnormality – not necessarily twice background level

Third level trigger is where there is real risk to personnel underground – not necessarily three times background level

Triggers vary from location to location and over time

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Panel returns

•Large air flow quantity

•Close to fresh air

•Unreliable deficiency ratios

• Absolute concentrations low and air flow dependant

•Only reliable indicator – CO make

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Physical Indicators

May be more sensitive than gas measurement to identify abnormality and locate emission points.

Must be supported by gas measurement

Change from normal is the detection criterion

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Areas of low or no airflow

Need norms to compare concentrations/indicators with.

Can use concentrations and ratios within limits of accuracy

Do not use text book triggers or norms established under different mining conditions or locations eg MG vs TG.

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LW101 Goaf Tube Bundle Sample Point Gas TrendTube 18 - 49 c/t MG Seal

0.0

5.0

10.0

15.0

20.0

25.0

12-Feb-99 04-Mar-99 24-Mar-99 13-Apr-99 03-May-99 23-May-99 12-Jun-99 02-Jul-99

Ox

yge

n (

%)

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

160.0

180.0

Ca

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(p

pm

)C

arb

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Dio

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x10

-2 %

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O2 CO CO2

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Indicators in areas of no air flow

Most ratios are measures of the conversion efficiency of oxygen to products of oxidation and are therefore essentially equivalent.

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multitude of deficiency ratios as they should all tell the same story.

Other ratios can be used to assist investigation not part of formal plan.

Ratios

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Site specific indicators

These are ratios or formulae involving various gas concentrations that have been shown to be a sensitive indicator of deviations from normal. E.g. H2 to CO ratio or CH4 to CO2.

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TARP review data

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CO ppm

H2

pp

m GR < 0.5

GR> 0.5

GR > 0.7

LEVEL 3LEVEL 2aLEVEL 2

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Quantify TARPS

Do not use adjectives or verbs to describe TARP“presence” or “trace” of ethylene“significant” concentration of hydrogen“abnormal” Graham’s ratio

Use numbers eg>10 ppm ethylene> 50 ppm hydrogen> 0.8 Graham’s ratio

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Know your indicatorsKnow your indicators

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Fundamental principles

Simple and Robust Adequately resourced – personnel and equipment Focus on prevention and early detection - validation,

clarification and remediation Requires detailed knowledge of normality Triggers not set in stone should be reviewed and

revised as experience grows or conditions change High quality mine monitoring information Do not be afraid to ask for advice If the TARP mandates an action it must be carried

out promptly