MIL-STD-2199A APPENDIX B
B.3.1.2.2.2 Repair of unbonded GRP. If the shaft covering contains area(s) of unbonded GRP, whether evident or suspected, none of which produced a spark during the spark test, repair as follows:
a. Remove a band of GRP from around the entire circumference of the shaft, in way of each unbonded 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: Make every attempt to remove only the GRP such that the elastomeric coating layer is left intact to the maximum extent possible. The GRP should be able to be peeled/torn away from the polysulfide elastomeric coating in those areas in which the GRP remains partially adhered.
b. Bevel the edges of the GRP on both sides of each defective area 1 to 2 inches.
c. If, upon removal of the GRP from the unbonded area(s), it was discovered that the failed adhesion occurred at the shaft substrate (for example, the elastomeric coating and primer came off with the GRP) and bare steel is exposed, inspect the shaft steel for damage/deterioration as outlined in the applicable shafting TRS or MS and/or S9086-HM-STM-010/243 and repair accordingly. Otherwise, proceed to step f below.
d. Prepare the bare steel areas for application of the covering system in accordance with A.3.1.1 as applicable. e. Using a paint brush, re-apply the primer to all areas of exposed shaft steel in accordance with A.3.2.1 as
applicable.
f. If, upon removal of the GRP from the unbonded area(s), it was discovered that the failed adhesion occurred at the elastomeric coating-to-primer interface but the primer remains intact with no evidence of shaft corrosion/deterioration - OR - if primer was applied in step e above, apply a layer of the elastomeric coating (First Coat - Gray) over each area of primer (see A.3.2.2). Otherwise, proceed to step g below.
NOTE: A small quantity of Parts A and B shall be mixed in the proper ratio and applied to the area(s) with a paint brush.
g. If, upon removal of the GRP from the unbonded area(s), it was discovered that the failed adhesion occurred at the GRP-to-elastomeric coating interface (Second Coat - Black) and the majority of the black elastomeric coating layer remains intact - OR - if elastomeric coating was applied in step f above, apply a layer of the elastomeric coating (Second Coat - Black) in way of each band of removed GRP (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 shall be mixed in the proper ratio and applied to the area(s) with a paint brush.
h. Spark test the elastomeric coating once the coating is tack-free. 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.
i. 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 the 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.
NOTE: If the repair is accomplished with the shaft in place and the shaft line cannot be rotated, peel ply tape shall be applied over the last layer of GRP. Once the resin has cured, this ply is then peeled off, taking runs or sags with it.
j. After the resin has cured, re-inspect each of the repaired areas with the spark tester to validate the integrity of the covering system.
k. Upon achieving a satisfactory spark test, paint each repaired area in accordance with A.3.2.6.
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