2. Spiral case and draft tube or pump casing and suction inlet
Annual. Check condition of interior coating and repair as required. Weld repair cavitation
damaged areas of draft tube liner. Inspect riveted and welded joints for leaks and corrosion and
repair as required. Check mandoors for leaks and condition of door hinges. The draft tube or
suction tube liner should be checked for voids between the liner and the concrete and grouted if
necessary. Any leaks between the concrete and the spiral case, pump casing, draft tube, or
suction tube should be monitored and, if excessive or if an increase is noted, the source of the leak
should be found and repaired. The spiral case is a pressure vessel, and the repair procedure must
take this into account.
Not Scheduled. If condition of interior coating is such that spot repairs are no longer effective,
sandblast and repaint entire surface. Draft tube liners severely damaged by cavitation may be
repaired by cutting out the damaged area and welding stainless steel plates in place that have been
rolled to the proper diameter.
3. Wearing Rings
Annual. Check top and bottom wearing ring clearances at four points, 90 degrees apart. Compare
to the design clearance and previous readings. If clearance is approaching 200 percent of design
clearance, schedule wearing ring replacement.
Not Scheduled. Remove runner or impeller and replace or renew wearing rings when clearance
exceeds 200 percent of design clearance. Wearing rings that are an integral part of the runner or
impeller or the casing in some cases may be built up by welding and remachined. Replaceable
wearing rings, in most cases, should not be built up by welding, as the heat of welding can induce
stresses or distort the rings. If the wearing rings are replaced, the stationary rings should be
supplied with an undersized inner diameter and bored concentric to the center of the unit.
4. Main Shaft Packing
Weekly. Check flow and pressure of packing cooling water. Check for excessive heat and for
leakage past the packing. Tighten the packing gland as leakage becomes excessive and grease the
packing box if and when required.
Not Scheduled. Remove old packing and lantern ring and thoroughly clean packing box. Check
packing sleeve for excessive wear and repair as required. Install new packing, staggering adjacent
rings so that joints do not coincide.
5. Mechanical Seals
Weekly. Check for excessive leakage. Properly installed mechanical seals should require very
little attention. Follow manufacturer's recommendations for lubrication during extended outages.