Transient Analyses
Pit 1 Governor and Pressure Relief Valve Testing
PG&E
suspected that the original flyball governors were no longer capable of
providing accurate control. Wear and erosion over time had resulted in
wall-thinning of the penstock, limiting the allowable pressure transients.
The owner wanted confirmation that the facility was safe for long-term, reliable
operation considering the age and condition of both the penstock and turbine
control equipment.
Devine Tarbell & Associates (DTA) planned and performed tests to assess the condition of the circa 1925 flyball governors and pressure relief valves (PRV).
Functional testing and transient analysis were performed at the site. Governor and PRV performance were well documented, and tests confirmed that pressure transients during load rejection events were unacceptable. Based on DTA staff recommendations, stop-gap measures were implemented for the interim period until a permanent solution could be adopted.
Governors have been replaced in conjunction with major overhaul of the PRV and turbine. If properly maintained, the turbine, governors, and PRV at this plant will operate reliably for another 40 to 50 years.