MIL-STD-2199A APPENDIX B
B.3.1 Shaft covering inspections. The shaft covering shall be inspected after application (before painting), at each drydocking, and during routine underwater hull inspections.
NOTE: If the shaft covering is so severely damaged as to preclude repair, the entire covering shall be removed and the shafting re-covered as a new installation by the procedures described herein. The covering is to be removed by machining using a blunted (bull nose) machine tool. Exercise extreme caution so as not to damage the underlying shaft surface when removing the GRP.
B.3.1.1 Post application inspection and repair. The following inspections shall be conducted after the GRP has hardened. Corresponding corrective actions shall also be accomplished pending results of the inspection.
B.3.1.1.1 Inspection.
a. Visually inspect the GRP, paying particular attention to the GRP-to-sleeve interfaces and those flanges coated with a resin formulation. Look for discoloration which may be evidence of overheating during cure, white laminate which indicates poor wet-out, air bubbles, pimples, or rough spots.
b. Tap suspicious looking areas with a coin. A dull or hollow sound indicates trapped air or de-bonded area. c. Slowly pass a high voltage spark tester over the entire coated area, with particular attention paid to the
suspicious areas. Pinholes are evidenced by bright sparks, which can be clearly distinguished from the purplish corona. (A suitable spark tester is shown in S9086-VG-STM-010/634.)
B.3.1.1.2 Corrective action.
a. Surface defects, such as areas containing isolated or scattered pinholes, pimples, or rough spots, shall be sanded smooth and recoated with resin used for the shaft covering.
b. Widespread area(s) of air bubbles or pinholes shall be repaired by sanding the GRP surface completely around the circumference and applying an additional ply of tape and resin to cover the defective area.
NOTE: Air bubbles or pinholes identified on flanges coated with a resin formulation shall be repaired by removing the resin in way of the defective area(s) and having the resin formulation re-applied (see A.2.3.2.e.2).
c. Area(s) which appear to be debonded or area(s) of white laminate shall be repaired as follows:
(1) Remove the fiberglass tape and resin, around the entire circumference of the shaft in way of each defective area, until fully bonded GRP is reached. A disc sander, Dremel tool (or equal), or suitable abrasive cutting tool may be used to score the GRP. The fiberglass cover in the damaged or defective area is to be removed with a disc sander after being scored. Exercise extreme caution not to damage the underlying shaft surface when removing the GRP.
NOTE: For those shaft sections to which the elastomeric coating was applied, make every attempt to remove the GRP only down to the coating layer. The GRP should be able to be peeled/torn away from the polysulfide coating, leaving the coating intact to the maximum extent possible.
(2) Bevel the edges of the GRP on both sides of each defective area 1 to 2 inches.
(3) For those shaft sections to which the elastomeric coating was applied, apply an additional layer of the coating (Second Coat - Black) over the entire shaft area(s) from which the GRP was removed (see A.3.2.2). Blend the coating layer onto the beveled edges of the GRP.
NOTE: A small quantity of Parts A and B can be mixed in the proper ratio and applied to the area(s) with a paint brush.
(4) Once the elastomeric coating is tack-free, it shall be spark tested. If there are any areas that spark, continue to brush coating onto the suspect areas and repeat spark test until a satisfactory spark test is achieved.
(5) Prepare a length of glass tape sufficient to provide a four-ply covering for each band to be repaired; for narrow repair sections, use 2- to 4-inch wide glass tape. Re-apply GRP over the area(s) from which it was removed in accordance with A.3.2.4. Ensure the GRP extends over the beveled edges and smoothly blends with adjacent GRP surfaces.
d. After cure, re-inspect each of the repaired areas with the spark tester and repeat respective applications as required until a satisfactory spark test is achieved.
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