Voyage Repairs: The Lost Art of the Wrench

When I first entered the fleet in 1988, it was unheard of to call for outside assistance on any kind of repairs unless ship’s force had already exhausted all means to correct the problem. However, by the end of my career in 2007 it had become the norm to call for help instead of trying to execute the repairs by ship’s force. Part of the driving force behind this trend are the technological leaps in the designs of today’s warships. However, I still believe that despite the technology, a well trained crew under strong leadership and a tailored quality maintenance plan can repair just about any piece of equipment if given the chance. Even if 90% of the sailors turning the wrenches have absolutely no experience, all you need is a seasoned Chief with a strong First Class Petty Officer to get the job done. Basically it boils down to trust. The internal chain of command has to trust that their crew can accomplish the task and convince the external chain of command to trust their decision to proceed with the voyage repairs.

My first significant experience with a voyage repair was on board USS AMERICA during Desert Storm. The ship was in the Red Sea Operating Area conducting air strikes when we were ordered into the Northern Arabian Gulf. The window of time to arrive on station was short and even at Flank Speed, we would only arrive about six hours before our first scheduled launch. As luck would have it, Number One Main Reduction Gear experienced a catastrophic loss of lube oil pressure. As a result, the shaft had to be locked which greatly reduced the maximum speed available for transit and a major loss of air power for the Coalition Forces. Fortunately, analysis of the logs and recreation of the problem allowed for a quick deduction as to the cause – the drive shaft for the attached lube oil pump had failed. Here was our dilemma, this was the original drive shaft that was installed when the ship was built. In theory, we had a bulkhead spare in one of the hundreds of store rooms – but the Supply Department’s records didn’t go back to commissioning. Our  other option was to contact General Electric in hopes that they had a spare. With parts in hand, we estimated a turnaround time of 8-10 hours. In the meantime, the shaft was still locked and we were rapidly approaching the go-no-go point for making it on station. Here is where my obsession with reading technical manuals first paid off. I knew where to find the bearing loading charts for the reduction gear, maximum output capacity of the steam driven lube oil pump if the governor was overridden, and the constant run abilities of the emergency lube oil pump. By running both the steam driven pump and emergency pump in parallel, we had just enough oil flow to feed the most dependent bearing at Flank Speed. This allowed us to keep the shaft in service while we found the replacement parts. I was one of MP Division’s Quality Assurance Supervisors so I was given the opportunity to design the work package for the repairs. I was also the work center Supply Petty Officer so my other main task was finding the drive shaft and all supporting parts and gaskets before the repairs could be effected. I approached this task from two fronts, get Supply Department to find the rumored bulkhead spare and contact General Electric. By the time we had the contract hammered out for General Electric to custom manufacture a new drive shaft from original blueprints, Supply found the bulkhead spare. So, we had one on the ship and one being manufactured and flown to the ship with. The repairs took just under 8 hours and we were able to conduct them on station. The lesson I learned from this first major repair of my career was that intimate knowledge of your equipment will allow for relatively quick assessment of the unknown problem and also help formulate a plan for accomplishing the repair without compromising the mission of the ship.

After the AMERICA I served on USS MCCLUSKY and USS STOUT where I was able to hone my skills of accomplishing the nearly impossible repairs without outside help. This led me to my final ship, USS NITZE where these skills would pay off and I was able to lead my crew to accomplish the most significant voyage repair of my career.

Shortly after departing from a week long port visit in Dubai, UAE the ship experienced a catastrophic failure of 2A Line Shaft Bearing. A failure of the aft oil seal resulted in a loss of over three quarters of the oil sump capacity. This loss of oil caused the bearing lining temperature to increase from 100 F to over 400 F in less than one hour. The bearing is constructed with a Babbitt lining. Babbitt is a soft white metal allow consisting of tin, lead, copper, and antimony with a melting point between 460 and 600 F. Close inspection of the bearing by removal of the casing end seals revealed that the bearing liner had melted and was extruding along the drive shaft. This casualty resulted in the loss of propulsion on one of the ship’s two drive shafts and drastically reduced the ship’s maneuverability and speed. Under normal circumstances, a ship that suffers this type of equipment failure would simply proceed into the nearest Industrial Repair Facility and have the repairs effected by a group of highly trained contracted workers. However, to do this, the ship would need to return to either Dubai or Bahrain and spend a minimum of five days in the repair facility while the bearing was replaced. This was not the ideal option on this particular day given our mission tasking and critical rendezvous the following week.

However, as it is often said, “fortune favors the foolish”. The offending bearing is carried onboard in the ship’s supply system, two of the ‘old salts’ in Engineering Department have many years experience conducting this type of maintenance, and two other ‘old salts’ in Deck Division are experienced riggers. But, none of these experienced sailors have ever attempted a task this daunting while underway with an inexperienced maintenance crew. Phone conversations with the ashore technical community assured the Captain and Chief Engineer that ship’s force was not capable of replacing the bearing, especially while at sea. After weighing the pros and cons of returning to port and letting the professionals tackle the job against the pros and cons of proceeding to our scheduled rendezvous and allowing the Chief to execute the repairs at sea, the Captain chose to gamble on his Chief and highly motivated, if inexperienced, Engineers and allow ship’s company to make the repairs while making best speed towards the next mission area.

The Line Shaft Bearing is used to support the weight of the propulsion drive shaft as it transits through the ship. This particular bearing, Number 2A, is located in the space known as Shaft Alley. Access to the Shaft Alley is through a vertical trunk that extends down three decks. The base of the bearing is mounted to a foundation approximately three feet above the deck plates with the top half flange at around five feet above the deck plates. The clearance between the top of the bearing housing and the overhead is less than three feet and is congested with piping from various critical fluid systems. To further complicate the repairs, access to the bearing is through tight passages of less than 3 feet wide with several sharp turns.

The first task was to remove the damaged bearing from its housing. First we had to cool down the bearing housing which three hours after the casualty was still too hot to touch. To do this, first the bearing top shell had to be removed. This shell weighs just over 900 lbs and is machine fitted to the top bearing half. Due to the space constraints, the housing could not simply be removed and placed on the deck plates, it had to be suspended from the overhead over the propulsion drive shaft. Preparing the site for the maintenance required removal of interferences at the work site and the path to be used to rig the damaged bearing out and new bearing in. The process of removing and suspending this housing required the use of five chain falls, three of which were used to suspend it from the overhead and took over five hours. Next the bearing oiling system had to be removed and inspected for damages. The oiling system is simply a large bucket wheel that drags oil from the sump and delivers it to the top of the bearing where the motion of the shaft draws the oil across the surfaces. This particular oil ring weighs just over 200 lbs and had to be lifted by hand. Luckily the oiling system had not suffered any collateral damages; a new one was not available. After removing the oiling system, the bearing top half was removed. The top half of the bearing weighs just over 600 lbs and required the use of another five chain falls (at this point, every chain fall on the ship was in use). While removing the top half of the bearing we discovered the extent of the damages. The bearing material had welded itself to the shafting across the entire surface. With the top bearing half removed the tasking shifted to removal of the bottom half of the bearing. To add to the difficulties associated with the fact that the bearing had welded itself to the drive shaft, the weight of the shafting had to be overcome. Additionally, with the bearing removed, the shafting required support while the housing and damaged shafting were cleaned and prepared for reassembly. The shaft was supported and raised 0.060” by hydraulic jacks from the Repair Lockers. While 0.060” may not seem like much, it is just enough clearance for removal and installation of the lower half of the bearing shell. However, due to the extensive damage, removal of the lower bearing required over eight hours and the use of sledge hammers.

During the removal of the damaged bearing, the new bearing was located and rigged into Shaft Alley. This too was easier said than done. The new bearing was located in one of the aft supply store rooms on the fourth deck and had to be rigged in their shipping containers to prevent damage while transporting to the top of the Shaft Alley access trunk. Five hours later, the new bearing halves were staged at the deck of Shaft Alley awaiting cleanup and preparation for installation.

Installation seemed to be proceeding smoothly until the new bottom half bearing became stuck half way through the installation. When lifting the shafting for the removal of the damaged bearing, wooden blocks were used with the hydraulic jacks to prevent damage to the shafting surfaces. Unfortunately, during the removal of the damaged bearing half the stresses caused by the sledge hammer blows caused the wooden blocks to fracture. These fractures allowed the shafting to settle just enough to prevent the new bearing from rolling into place. Quick thinking by the Damage Control experts provided the solution of using metal shoring from the Repair Lockers to support the shaft while the hydraulic jacks were repositioned, this time with metal blocks and rubber for additional support and protection. Once this hurdle was overtaken, the installation proceeded smoothly. Before the upper housing could be reinstalled, the oiling system had to be reassembled. This task was more difficult than expected due to the fact that the oiling ring needs to be installed precisely at 1.12” from the end of the bearing for proper operation. Fortunately, installed in the lower housing were four pins designed to align the oiler ring with the required clearance while securing it to the shafting. With the oiler ring installed, the next step was to set up a dial indicator to ensure the ring was installed properly and would not ‘wobble’ when the shaft rotated. To do this the ship needed to come dead in the water and rotate the shaft on the electric jacking motor. However, for the past 30 hours the ship had been making way at twelve knots with the shaft locked and at 100 % propeller pitch. This caused the shaft locking device to be over-torqued preventing its disengagement. Normally it takes less than a minute to disengage a shaft locking device. This time it took over twenty minutes of creative massaging for disengagement. By the time that the lock was safely disengaged, the ship had fallen too far behind schedule and could not remain dead in the water for another twenty minutes to conduct the testing. Instead, the trueness of the oiler ring was validated using precision measurement. Finally the final reassembly was completed and the testing could commence.

Testing was conducted by first rotating the shaft using the jacking motor while dumping fresh oil over the bearing to establish the initial oil film and verify the proper operation of the oiling ring. With the first test successfully passed, the shaft was rolled under the power of the opposing shaft and inspected for unusual temperature rises and noises. Next the shaft was rolled under the power of its associated engines at various speed ranges, each time checking for proper temperatures. With all tests passed the bearing and shafting were returned to unrestricted operation. In order to arrive at our next mission area on time, we needed to proceed at 25 knots for the next four days. During this time the bearing was closely monitored and performed flawlessly.

The total time for repair and testing by ships force was just under forty-four hours.

Basically, the problems facing mechanical failures in the modern fleet have less to do with advanced technology than they  do with failure to properly train the operators on how to predict, identify, and prevent failures. In the event that a failure happens, that same properly trained crew can, and will, effectively accomplish the repairs in less time than the average shipyard or contractor and at significantly less cost. Unfortunately, time is running out for the Fleet, the Chief is the expected expert on his or her associated equipment. However, with lack of training and rapid advancement programs, today’s average Chief’s Mess lacks the required technical expertise to do much more than recommend that any major repair be outsourced – even if it compromises the current ship’s mission.

 

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