Critical Controllable Pitch Propeller Repairs Performed on Military Vessels

CPP Propeller Blade Palm seal replacement

Supporting strategic military assets around the world is a critical task requiring specialized equipment and tools in many cases. When fully loaded supply vessels develop propulsion system failures and seal leakages, operators and owners turn to the experts in the field, the Subsea Solutions Alliance. While operating in the Indian Ocean, it was noted that one shaft line on a military supply vessel was losing oil from its propeller pitch control system. Once in port a dive inspection indicated that oil loss was coming from one of the propeller blade palm seals on the hub. With this critical leak identified, options were weighed. Considering the cargo that was onboard the supply vessel, this limited the locations the vessel could transit to, thus impacting the vessel’s schedule and operators budget. As the Subsea Solutions Alliance performed exactly the same repair on a sister vessel to the stricken vessel, a class approved procedure was already outlined and approved by the vessel operator and owner. Working together with the Original Equipment Manufacturer of the propulsion system, the Subsea Solutions Alliance developed a repair plan for this propulsion shaft line.

The first challenge in this unique repair was to get the personnel and equipment necessary to support this work to a remote location in the Indian Ocean. Working together closely with the client’s logistics personnel and the Original Equipment Manufacturer, the gear was shipped on Military aircraft as “military cargo”. Personnel travelled to the location via the military’s air command system. All of this logistics happened within days of the confirmation of the repair, thus requiring the
operations team within the Subsea Solutions Alliance to work closely with the owner’s representatives to provide the fastest and most cost effective logistical process. Once on site, the team performed an inspection dive on the vessel in the anchorage and began the preparation work on the propeller. Once the pier was available the vessel was moved along side and the intricate work began.

Working together with the Original Equipment Manufacturer, the pitch oil system was isolated and prepared for the performance of an in water repair. With the system properly arranged the propeller blade was released from the propeller hub without the ingress of seawater and without the release of pitch control oil to the environment. Once the blade was lowered away, the team found the defective seal, changed the seal ring and re-installed the propeller in accordance with the approved OEM and class approved procedure. The propeller blade bolts were then torqued to the proper settings and the system prepared for use.

Within 18 hours the blade seal was exchanged and the leak resolved. Within hours of our completion of work, the diver / technicians saw the stern lights on the horizon. The vessel left again on maneuvers with the problem resolved through an OEM and Class approved procedure. Bringing the repair process to the ship as opposed to the ship to the repair location is what the Subsea Solutions Alliance is all about. Performing this process in this case saved the client millions of dollars in direct costs and put the vessel back in service without delay!