Allis Chalmers Flashcards
Although vertical Hydro-unit machines may be extremely large:
close tolerances must be maintained
The vertical Hydro-unit machine that has the thrust bearing and upper guide bearing located above the rotor is called:
Suspended type
On large low-speed vertical Hydro-unit machines, the rotor poles are secured to the rim by:
Driven tapered keys
On an adjustable-blade pump or propeller (Kaplan) type turbine, a hollow shaft is required on the electrical machine to:
allow oil pipes to be carried through the shaft from the oil head at the top of the unit to the turbine servomotor
On guide bearings, lubrication arrangements eliminate the need for an oil circulating system. The designated oil level is usually about ___ the length of the bearing above its lower end
1/3
Brakes are usually operated by compressed air at ____ psi. When used as jacks, the brakes are operated by an oil pressure of ___ psI.
75-100; 1000-3500
High-pressure bearing lubrication is frequently used to reduce:
Breakaway torque
The high-pressure bearing lubrication pump assembly uses a ____ to prevent starting the machine (hydro-unit) until the pressure is approximately 1000 psi.
Pressure switch
Prior to erection of the unit, the turbine or pump runner and shaft are centered and supported in a position at a specified distance usually ___ inch below the correct operating position.
1/4 to 3/4
During the alignment process, fins should be provided on the plumb bob to allow it to hang in a pail of heavy oil to dampen any swings and protect the plumb line from:
all strong air currents
Electric welding on any part of the machine is a serious hazard to bearings. A bearing surface can be damaged:
rapidly if welding current passes across it
In regards to Hydro-units, if possible all electric welding should be done:
Before bearings are assembled
The thrust bearing tub cooling coil should be water tightness tested to a water pressure of _____ % of normal working pressure
150
Precautions should be taken during assembly of the thrust bearings to avoid
All of the above
Segmental bearings made up of independently adjustable segments must be set to:
Proper elevation and clearance
To eliminate the possibility of shaft current, bearings and other parts should be:
Insulated
Check the insulation with a ___ volt insulation meter, if the resistance is less than ____ ohms inspect the insulation and make necessary corrections.
500; 20000
Before drawing the couplings together, their mating surfaces must be in alignment, parallel, clean and free from burrs. The couplings must be drawn up
evenly to prevent distortion
Coupling bolt tension can be determined by an accurate measurement of the bolt:
Elongation
To prevent plumb wires from swaying and twisting, the finned weights should be immersed in pails off
Oil
Check commutator ____ with a dial indicator rather than by visual observation.
Run out
Various instruments and relays and their associated equipment, wiring, piping and conduit should be carefully installed, making sure that it does
not short-circuit the bearing insulation
The rotating parts of the machine must be in ____ balance and may require the addition of weights to the motor
Dynamic
Before connecting the generator to the power system check
Phase frequency
If an operational check of the shaft run-out is required, make it after the generator.
Is operating under full load
