Fist 2-7 Flashcards
In planning a major overhaul of a hydroelectric unit, one of the best sources of information is:
Maintenance records
Determining the condition of the equipment should be done by performing a thorough inspection of the unit
6-12 months before the planned overhaul
A list of ____ for all of the machine’s components should be made from the drawing information
Weights
If substantial welding is needed, then a ____ for the required repairs should be written and distributed to all personnel that will be involved in the welding
Welding procedure
Units with replaceable seal rings should have a ____ onsite
spare set
Shaft run-out readings, bearing temperatures, pressures and Permanent magnet generator (PMG) voltage are all part of:
Pre shutdown readings
Pre tear down readings include
Shaft alignment readings, guide bearing clearance, seal ring clearance, and generator air gap
To make sure parts are installed in exactly the same position from which they are removed, they should be _____ prior to removal
Match marked
The rigging to lift the thrust block should include (a) ____ so that the block can be kept level to prevent binding when it is lifted off the shaft.
Turnbuckles
After removing thrust and guide bearings, minor scratches and even some deep gouges can be adequately repaired by ____
the high spots from the babbitt surface.
Scraping
In most cases, the repair of ____ damage can be accomplished much more effectively with the runner removed from the turbine pit, as the runner can be positioned for easier access.
Cavitation
Where an overlay of a dissimilar material is being used. such as stainless steel over mild steel. enough material should be removed to allow at least ____ weld passes to be made.
Three
The interior bore of the packing box can be built up with ____ as long as the box is structurally sound
Epoxy coating
Bearing cooling coils should be thoroughly inspected and ______ tested
Hydrostatically
To find the unit’s center, the upper bridge and head cover should be installed after all the ____ parts have been removed. A ___
wire should be hung through the unit and
reference measurements taken from the stator, the turbine bearing housing, the packing box bore, and to trammel points in the draft tube.
Rotating; single
Dowels have a very ____ fit to prevent the components from shifting once the part is positioned
Tight
When doweled components are moved during the alignment process following the overhaul of a unit, ___ is necessary.
Re doweling
A more accurate method of measuring the preload of a coupling bolt is to measure the amount the bolt ____ as the nut is tightened.
Stretches
When aligning a unit, it is important to make the bearing centers all ___, the shaft must be perfectly plumb. This can be accomplished by installing the turbine bearing and shimming the shaft to center in the ___ bearing (s).
Concentric; Turbine
When setting clearances on upper and lower guide segmented shoe bearings, install a feeler gage to check clearance by
inserting the feeler gauge so that it extends all the way through the bearing
When working on wicket gate adjustment, the amount the servomotor travels after the gates contact each other is referred to as the ____
Squeeze
There should be ___ leakage upon the initial startup after the installation of new turbine shaft packing. The packing gland should be _____ evenly and in small steps until the
leakage is reduced sufficiently.
Generous; Tightened
A very thorough inspection of the _____
and the ____ should be made to check for any bolts, nuts, tools, etc.
Generating housing, spiral case
To prevent the damage that could occur from circulating currents passing through them the following are insulated from the frame and should be checked with an ohmmeter prior to startup:
upper guide bearing, thrust bearing, PMG
Operational readings should be taken once the unit has been determined to operate with no problems, they include:
Bearing heat run, shaft run-out readings, load rejection tests
