A team of engineers at the Corrosion and Coatings Engineering Branch at the U.S. Naval Surface Warfare Center, Carderock Division (Potomac, Maryland, USA) has introduced a new standardized method of ship inspection that they believe will lead to lower maintenance costs.
The engineers created two maintenance-requirement cards (MRCs) that were uploaded onto the Planned Maintenance System (PMS) Viewer software. PMS Viewer is a document tool allowing users to search, view, and print ship-wide maintenance index pages.
These particular maintenance-requirement cards provide step-by-step instructions for inspections and repairs to topside platforms on naval ships. One card calls for an annual inspection of the exterior steel window-frame structure for corrosion, cracks, or shrinkage within the window sealant around the glass. If corrosion is excessive (more than 10% of linear area around the windows) or if the sealant is shrinking, cracking, or deteriorating, then the inspector should perform the second maintenance-requirement card for repair and preservation of the exterior window structure and sealant replacement.
According to Jamaal Delbridge, a materials engineer at Carderock, the inspiration for this project came from a proposal written by Brittany Preston-Baker, another member of the Carderock team and a part of the Corrosion Control Assistance Team (CCAT). When assisting with maintenance procedures on various platforms, CCAT members noticed windows that were shattered, sealant that was cracked, or other corrosion product around various window structures on ships.
Delbridge and Jim Wigle, the CCAT project engineering lead, developed the maintenance-requirement cards referencing the non-standardized procedure. The approval process for the cards took nearly six months. Once approved, the commodity specialists uploaded the cards onto PMS Viewer.
Delbridge says the only information on windows maintenance procedures that was previously available in PMS Viewer was for repairing window wipers and its associated parts, but nothing in regards to replacing the window sealant or repairing and preserving the ship’s exterior window superstructure. CCAT had already created a non-standardized procedure to preserve window structures and replace cracked sealants; it was just a matter of getting the procedure on a maintenance-requirement card in the PMS Viewer.
To understand if the corrosion issue was across the fleet, Delbridge inspected 14 ships, including Arleigh Burke-class destroyers, Wasp-class amphibious ships, and the Ticonderoga-class cruisers. The inspection discovered that corrosion issues were a greater problem with the destroyers. The bridge and the landing safety officer’s window structures were identified as having the reoccurring corrosion issues.
According to the engineers, several factors contributed to the corrosion issues: a corrosive environment; an engineering design flaw that enabled entrapment of fresh water and seawater on top the window seal; and ineffective repairs, such as painting over sealants and using high-impact tools causing the glass to shatter in some cases. After Delbridge started this task, he discovered that the window configuration had dissimilar metals.
“There were a lot of the corrosion issues,” he says. “The window frame on the inside was stainless steel, but you had carbon steel nuts and bolts that were connecting the ship superstructure, which is steel. That’s a recipe for galvanic corrosion.”
Cutting costs is always a goal for the fleet, and Delbridge says the developed maintenance-requirement cards will play a big role in achieving that goal by extending the service life of the exterior window structures prone to corrosion.
“These windows corrode within six months to a year,” he explains. “With this new MRC, not only will it give the right procedures, but you’ve extended the service life of these windows. You won’t have to do as much maintenance, which also means decreasing costs.”
Source: U.S. Naval Sea Systems Command, www.navsea.navy.mil.