Rocky Reach Units C8-C11

Holistic Design Review Update

March 16, 2015

C8-C11 Holistic Design Review

• Purpose - To provide an update of the Holistic Design Review of C8-C11 turbines.

• No Board action is being requested.

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Last Update – Sept. 2014

• Holistic Design Review

– Anticipated completion Nov. 2014

• 1st Unit Outage Start – June 2015

• Project Budget: $42- $44 Million

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Holistic Design Review

• Objective

– To evaluate the stresses and fatigue lives of the major components of the turbine.

• Why

– To maximize the remaining life of the complete turbine. Are there other components that could fail sooner than expected?

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Holistic Design Review • Why

– Stress and fatigue calculations only performed for the turbine blades and hub by the manufacturer.

– Multiple components from C10 appeared to have been overstressed (piston rod, headcover, blade bushings, cylinder spider).

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Holistic Design

• Finite Element Stress Analysis (FEA)

– An engineering calculation used to determine stresses in the individual components at various operating conditions. The calculated stress is compared to a safe allowable stress.

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Holistic Design

• Fatigue Analysis

– An engineering calculation used to evaluate the components undergoing cyclical loading and to determine when a crack will start (fatigue life-years). Goal is to achieve a minimum of 30 years of additional service.

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Holistic Design

• Fracture Analysis

– An engineering calculation used to determine the time until a component undergoing cyclical loading will fail after a flaw (0.080” crack) has already started. Goal is to achieve a minimum of 30 years of additional service.

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Rocky Reach C8-C11 Turbines

Components in green are included in the holistic design analysis.

Green components – Stress and fatigue life met criteria. Red components did not meet stress or fatigue life criteria.

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Blue Components – Engineering evaluation is complete. Red Components – Engineering evaluation is ongoing.

Summary

• Additional FEA and Fatigue evaluation required for:

– Turbine shaft

– Wicket gates

– Piston rod

– Servomotor eye bolts

• Estimated Engineering Cost - $350k

• Anticipated Completion – Late May 2015

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Potential additional Costs

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– Modify Turbine Shaft, $320k for 4 units.

– Modify existing Wicket gates, $400k for 4 units; or

New wicket gates,

$3 Million for 4 units.

Potential Extra Costs

– Modify Link Pins $10k for 4 units.

– New Servomotor Eye Bolts $500k for 4 units.

– New Cylinder spider cover bolts $30k for 4 units.

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Total cost: range $1.6 M to $4.2 Million

Summary

1st Unit Outage Schedule Impact

• None expected for:

– Turbine shaft

– Wicket gates

– Servomotor eye bolts

• Uncertain:

– Piston rod (know more in May)

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Conclusion

Sept. 2014 Update

• Holistic Design Review – Anticipated completion

Nov. 2014.

March 2015 Update

• Holistic Design Review – Original scope completed

Jan. 2015.

– Additional analysis anticipated to be complete by May 2015.

• Required Budget (4 Units) – $43.6 to $48.2 Million

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• Current project Budget (4 Units) – $42 to 44 Million

Questions

C8-C11 Turbine Repairs O&M Improvement Items

• Considering New Blade Trunnion Seal Design

– Reduces risk of oil leak.

– Estimated Cost: $670k for 4 units

• Relocate Hub oil vent plug – Est. $80k, 4 units

• Redesigned Blade Dowel Plugs – Est. $60k, 4 units

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Next Update

• Proposed for Early June 2015

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