up the disassembly and reassembly of a unit. Caution should be used in using
either hydraulic or pneumatic wrenches so as not to over or under tighten
Magnetic based drill.
A large magnetic-based drill can be especially useful
during an overhaul if any components must be slightly shifted and redoweled or
if there are other modifications to the equipment. Magnetic-based drills allow
fairly large holes to be bored accurately and also can be used in reaming dowel
Shaft packing or seals.
Whenever a unit is overhauled, the compression
packing of the main shaft and wicket gates should be replaced. Enough
packing should be ordered to allow for errors in cutting the packing. There are
a number of different types of packing available, so when choosing new
packing, care should be taken to ensure that it is the correct size and type for
the intended application. Be sure to take into account all the relevant
conditions the packing will operate under, such as shaft size and rotational
speed. Installing the wrong packing can result in excessive leakage, reduced
service life, and damage to the shaft or sleeve. Where mechanical seals are
used for the main shaft, a complete set of seal segments should be on hand in
case any of the segments are damaged during disassembly.
Micrometers and standards.
Inside and outside microm, along with a set of
standards for calibration, are essential for the overhaul of a hydrounit.
Micrometers are required to check diameters of main shaft bearings and
journals, wicket gate bushings and journals, and other wear parts to determine
if they are within tolerances. An electric micrometer may also be required for
unit alignment or installation of a boring bar.
Even if seal ring and wicket gate bushing replacement are not
planned, boring bars for both should be available just in case of an unexpected
situation. Suitable boring bars should be located and shipped to the jobsite
well before the overhaul. If boring is scheduled, the boring bars or accurate
drawings of the boring bar should be available well before the overhaul so that
any modifications, such as mounting brackets and boring anus, can be made.
On units with replaceable seal rings, a spare set of rings should be
onsite regardless of whether or not replacement is scheduled. On units where
the current seal ring design is questionable or where the rotating and stationary
rings are both