8
stainless steel, a new design should be considered. For more information on
seal ring design and material selection, refer to
seal ring design and material selection, refer to
Generator air coolers.
If the inspection or maintenance records indicate that
the generator air coolers require repair, specifications for the repair work
should be prepared. If the repair work can be accomplished by plant
personnel, materials such as spare tubes and all of the tooling required for
retubing should be procured.
should be prepared. If the repair work can be accomplished by plant
personnel, materials such as spare tubes and all of the tooling required for
retubing should be procured.
Scaffolding.
Turbine pit scaffolding to provide access to the shaft coupling
and lower guide bearing, and draft tube scaffolding to provide access to the
draft tube and bottom of the turbine runner, are required for any overhaul. The
scaffolding must be designed to support the weight of several maintenance
personnel plus components from the unit, such as bearings or the runner cone.
Scaffolding should be designed, built, and installed in accordance with
Reclamation Safety and Health Standards and American National Standards
Institute (ANSI) Standard A10.8, "Safety Requirements for Scaffolding."
draft tube and bottom of the turbine runner, are required for any overhaul. The
scaffolding must be designed to support the weight of several maintenance
personnel plus components from the unit, such as bearings or the runner cone.
Scaffolding should be designed, built, and installed in accordance with
Reclamation Safety and Health Standards and American National Standards
Institute (ANSI) Standard A10.8, "Safety Requirements for Scaffolding."
Cribbing material.
Cribbing material for cribbing parts removed from the
unit should be procured. Large timbers in various lengths and widths should
be available to block up the parts, spread out the floor loading, and protect the
floor. 'timbers should be stress graded and rated for use as cribbing. Rough
lumber may not have the compressive strength for heavy components. In some
cases, special jack stands may be needed. If these are required, they should be
designed by an engineer competent in the field and fabricated well before they
are needed.
be available to block up the parts, spread out the floor loading, and protect the
floor. 'timbers should be stress graded and rated for use as cribbing. Rough
lumber may not have the compressive strength for heavy components. In some
cases, special jack stands may be needed. If these are required, they should be
designed by an engineer competent in the field and fabricated well before they
are needed.
Miscellaneous materials.
A good supply of steel plate, angle iron, steel bar stock,
etc., in various thicknesses and sizes should be on hand for fabricating special tools or
brackets that may be required during the overhaul. There are always items that have
to fabricated once the overhaul is in process, and delays can be avoided if the materials
are available on site
brackets that may be required during the overhaul. There are always items that have
to fabricated once the overhaul is in process, and delays can be avoided if the materials
are available on site
.
Ill. DISASSEMBLY
3.1
Preshutdown and preteardown readings
The purpose of preshutdown and preteardown readings are to determine the
condition of the unit prior to the overhaul so necessary repairs can be made during
the overhaul. Operational readings, such as vibration and temperature data, can
provide a signature of the condition of the unit before teardown. The preteardown
readings are also useful as reference data during reassembly. In taking the readings,
it is important that all readings are consistent. For example, the north, south, east,
condition of the unit prior to the overhaul so necessary repairs can be made during
the overhaul. Operational readings, such as vibration and temperature data, can
provide a signature of the condition of the unit before teardown. The preteardown
readings are also useful as reference data during reassembly. In taking the readings,
it is important that all readings are consistent. For example, the north, south, east,