Continuous check of distortion using:
-- Dial indicators
-- Measuring seal clearances
-- Use of templates
Apply weld using a cross pattern or a temper bead technique. Cross pattern
welding should be arranged such that the final pass is in the direction of
water flow.
welding should be arranged such that the final pass is in the direction of
water flow.
Peen all passes except the top pass.
Apply post-weld heat stress relief.
"Grinding to Contour. Following the completion of welding, surfaces should be ground
to their proper profile. Profile should be checked using a flexible spline about 2 feet
(0.6 m) long. For large areas of repair, blade templates should be made.
to their proper profile. Profile should be checked using a flexible spline about 2 feet
(0.6 m) long. For large areas of repair, blade templates should be made.
gives guidelines for blade profile. The recommended upper limit surface finishes are
as follows:
as follows:
Head
Surface Finish
< 300 feet (91 m)
250 u in. (6.3 u m)
300-1000 feet (91-305 m)
120 u in. (3.2 u m)
1000 feet (305 m)
90 u in. (2.3 u m)
"When a large area of stainless steel is being applied to carbon steel over areas
greater than about 1 foot (0.3 m) square, witness holes should be ground through the
stainless steel to ensure that the overlay is at least 1/8 inch (3 mm) in thickness.
Grinding should extend slightly into the base metal and the holes etched with copper
sulphate to establish the interface between the carbon steel base metal and the
stainless steel overlay. Witness holes should be at about 18-inch (0.5 m) spacing.
After checking overlay thickness, all witness holes must be welded and ground to the
profile and finish of the surrounding overlay.
greater than about 1 foot (0.3 m) square, witness holes should be ground through the
stainless steel to ensure that the overlay is at least 1/8 inch (3 mm) in thickness.
Grinding should extend slightly into the base metal and the holes etched with copper
sulphate to establish the interface between the carbon steel base metal and the
stainless steel overlay. Witness holes should be at about 18-inch (0.5 m) spacing.
After checking overlay thickness, all witness holes must be welded and ground to the
profile and finish of the surrounding overlay.
"Weld Inspection. Welds made for cavitation pitting repairs are generally unstressed
from a structural point of view, therefore, soundness of the weld is not usually critical.
Nevertheless, there have been many examples where small defects or holes in the
stainless steel overlay on a carbon steel runner have led to large voids at the interface
between the overlay and the parent metal. These voids are
from a structural point of view, therefore, soundness of the weld is not usually critical.
Nevertheless, there have been many examples where small defects or holes in the
stainless steel overlay on a carbon steel runner have led to large voids at the interface
between the overlay and the parent metal. These voids are
believed to be a result
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