Cooling-enhanced welding procedures may prevent heat damage to the paint on ships late in the ship construction process. NNS photo
This Navy Metalworking Center project identified modified welding procedures that will prevent coating damage during welding. The heat removal solution(s) developed in this project, in many cases, will keep the maximum temperature of the paint / steel interface below the threshold temperature that causes damage. These solutions, once approved, will result in modifications to existing welding procedures.
Small welds often are made late in the aircraft carrier construction phase after painting and outfitting have taken place. These welds can damage the paint on the opposite side of the structure being welded. Heat from welding can cause discoloration, delamination, charring, and smoking of the paint. In some cases, damage to the paint will not be readily observable from an examination of the area’s surface. However, the damaged paint will likely fail prematurely. To preclude this damage, paint is often removed from the opposite side of the substrate prior to welding. Newport News Shipbuilding (NNS) has identified approximately 60,000 hours of rework in tanks and staterooms due to final welds damaging the paint.
NMC, along with an Integrated Project Team consisting of Future Aircraft Carrier Program Office (PMS 378), Newport News Shipbuilding (NNS), and the Naval Surface Warfare Center-Carderock Division, identified the effects of typical welding processes on typical attachment/wall thickness combinations with standard Navy coating systems. This project also developed and tested several cooling techniques that will prevent the welding-induced damage to coatings for many of these combinations.
The labor to remove paint prior to welding and to repair areas of damaged paint can be very extensive, especially late in the outfitting process. The results of this project are expected to reduce rework labor by approximately 15 percent and lead to an expected cost avoidance of more than $585,000 per ship. It is anticipated that these solutions will also benefit several other ship classes.
The solutions developed in this project will likely appear as appendices to existing welding procedures. Ship fitters will likely be given the option to utilize the proposed cooling solution when welding certain combinations of wall thickness and attachment size. Implementation will take place after NAVSEA review / approval and after further testing at NNS to confirm repeatability of results. Implementation is targeted for the third quarter of FY12 at NNS during final outfitting of CVN 78.
Naval Surface Warfare Center, Carderock Division
Newport News Shipbuilding
PMS 378 Future Aircraft Carriers