factors, may be loaded much higher than expected. The weight of each
component should also be considered when storing the parts so that the
allowable floor loading is not exceeded.
The following are general procedures for the removal of some of the
common parts of a hydrogenerator. The actual procedures used will probably
vary depending on the design of the unit.
Permanent magnet generator.
After disconnecting the wiring from the
PMG terminal block, remove the mounting bolts, being careful not to lose
the insulating washers and bushing. Center the crane over the PMG and lift
it off using eyebolts installed in the PMG case. Store the insulating gasket
between the PMG and the exciter housing with the PMG.
After removing the brushes, wiring, and exciter housing bolts, the
crane should be centered as close as possible over the exciter and the
rigging hooked up to the exciter housing. To prevent contact between the
exciter stator and rotor, strips of thick gasket material should be inserted in
the exciter air gap, or if possible, the entire exciter rotor may be wrapped
with gasket material.
The thrust block or thrust collar is fitted to the generator
shaft with a very tight fit and requires heat to expand it for removal. Prior
to removal, the unit should be jacked and blocked on the jacks so that there
is no weight on the thrust block. The oil should be completely drained, and
bearing housing covers and vapor seals should be removed to provide
access to the block. The rigging to lift the thrust block should include
turnbuckles so that the block can be kept level to prevent binding when it is
lifted off the shaft. If the design allows, the rigging should be attached and
adjusted before the block is heated. Some thrust block designs will not
allow this, as the radial keys must be removed before the rigging can be
installed. The heat should be applied quickly so that the block can expand
without transferring heat to the shaft. To accomplish this, several large
"weed burner" type propane torches or rosebud oxyacetylene torches
should be used. Care should be taken not to heat the rigging excessively.
The length of time required to heat the block will vary depending on the
"tightness" of the fit on the shaft and the condition of the mating surfaces
of the block and shaft. In most cases, when the block has expanded, it will
drop slightly, allowing the radial keys to be removed and the block to be
removed. Thrust blocks that rest on a shoulder on the shaft will not drop,
and the crane must be used to apply a slight upward force on the block
until it "pops" up. In these cases, a dynamometer installed in one leg of the
rigging can be helpful in preventing an overload on the rigging before the
block is expanded sufficiently.