Hydro Plant Risk Assessment Guide

Test T2.3.15: Electrical Operators – Power Screws
Power screws are typically made of carbon or stainless steel with bronze mating nuts to avoid
galling. They should be exercised and inspected for such things as: wear on mating surfaces
(both screw and mating nut), straightness of screw, thread damage, corrosion, surface finish
condition, and brake condition (if equipped).
Table 37 – Power Screws
Adjustment to
Results
Condition Index Score
Good – Power screw in good condition, no major deficiencies. Add 0.5
Moderate – Power screw in serviceable condition, no deficiencies
that could compromise safety.
No Change
Severe – Serious wear, defect or damage that could compromise
proper operation of the gate or valve.
Subtract 0.5
Test T2.3.16: Electrical Operators – Drums and Sheaves
Hoist drums and sheaves should be checked for wear and general operating condition. Structural
deficiencies should have already been noted in the Structural Integrity section.
Table 38 – Drums and Sheaves
Results
Good – Hoist drum in good condition, no major deficiencies. Wire
rope is secured to drum correctly; wire rope is not over spooled
when gate is in the 100%-up condition.
Moderate – Drums and sheaves in service able condition with
normal wear.
Severe – Drum highly worn in grooves, alignment incorrect,
sheaves worn, cathodes not working correctly or used up.
Adjustment to
Condition Index Score
Add 0.5
No Change
Subtract 0.5
Test T2.3.17: Electrical Operators – Gearboxes, External Gearing, and Chain Sprockets
A gearbox should be operated through a full operation cycle and observed for abnormal sounds
that may indicate internal problems. Opening, draining, cleaning, and inspection of gearbox
internals may be justified. Lube oil may be sampled to test the condition. External leakage
should also be noted.
E11-32