USBR FIST VOL. 2-1 Flashcards
(25 cards)
The rotating weight of the unit is transferred through the?
Thrust bearing, upper bridge, and stator frame to the foundation
Where is the thrust bearing located in an umbrella unit?
Below the rotor
There are typically three types of thrust bearings used in hydroelectric units, they are the?
Adjustable shoe, spring loaded bearing, and the self equalizing
The adjustable shoe thrust bearing uses a _____ under each of the shoes for adjusting the height and loading of the shoes
Jack screw
How does one install the thrust block?
It is heated to a predetermined temperature and lowered over the shaft, with the units on the jacks. The block is set on the thrust shoes, the rigging removed, and radial keys and keeper installed
With the block still hot the jacks are released to allow the…
Full weight of the unit to set the block in place against the keys
With the system on, it is possible for a couple of people to rotate a unit by hand or move the rotating components laterally on the thrust bearing. What are both required during the alignment process?
Both rotation and lateral movement
As alignment deviates, loading on the _______ will increase and so will vibration levels.
Guide bearings
Any increase in vibration from misalignment will decrease the?
Factor of safety for operation in severe circumstances
The concentricity of the stationary components can be checked by?
A single tight wire can be used as a plumb reference
No reading point deviates more than _______ inch from a straight line connecting the top and bottom reading point for shaft straightness.
.003
Plumb of center of shaft runout is…
.000025 multiplied by the length of the shaft from the highest plumb reading to the lowest plumb reading
What is offset?
The parallel misalignment between two shafts and occurs at the coupling between the generator and turbine shafts
What is shaft dogleg?
The angular misalignment of the turbine and generator shafts
How many plumb wires are used for alignment?
4 wires are hung 90 degrees apart
What is the first preliminary check?
With a dial indicator check the rise of each leg when loosing the mounting bolts
What is one of the most important things to be checked before any readings are taken?
Whether the shaft is free or not
How can you check the concentricity of the stationary components?
Temporarily install the upper and lower bridges and the head cover and take a measurement with a plumb wire and an electric micrometer
When the unit is assembled the concentricity of the stationary components can be checked by?
Taking clearance readings
Correcting the dogleg in the shafts requires?
Installing a shim pack between the coupling faces
The second method used for aligning hydro units with adjustable shoe thrust bearings is using the adjustable feature of the shoes only to achieve equal?
Loading
Move shaft to center in turbine bearing housing and move ______ to make it a plumb.
The top of the shaft
The final step in the alignment process is the installation and adjustment of the…
Guide bearings
To make the generator guide bearings concentric to the turbine guide bearings the _______ is used as a reference.
Shaft
