The 2003 Dry-Docking of Ex-USCGC Taney
Paul Cora, Curator, Baltimore Maritime Museum
USCGC TANEY is a 327' Treasury Class Coast Guard Cutter built in 1935-36. She was in continuous service from 1936 until 1986 and is one of two vessels of this class preserved in museums. The ship was built as a steam driven, twin screw, single rudder steel vessel with a raked stem, flared bow and rounded stern. The riveted hull was constructed of half-inch-thick individually galvanized plates.
Prior to her 2003 yard period, TANEY was last dry docked in 1983 at the US Coast Guard Yard, Curtis Bay, Maryland. The underwater hull body portion of the 1983 dry docking report included the following:
2. Intended Scope of the 2003 Dry Docking
The primary goal of the 2003 dry docking project for USCGC TANEY was the stabilization and treatment of the ship's underwater hull body for the purposes of watertight integrity and long-term preservation. Based on the information contained in the 1983 report (especially the significant rivet problems) the museum opted to put off major work above the waterline in anticipation of extensive work necessary to address corrosion damage.
Negotiation and planning with the Industrial Department at the US Coast Guard Yard, Curtis Bay, began in the summer of 2001 with a goal of dry docking the ship in the fall of 2002. The initial spec drawn up by the Museum and Yard staff was as follows:
In the year prior to the actual dry docking the museum formulated working diagrams showing tank the arrangement, capacity and current condition of the ship's fuel, potable water and feedwater tanks, as well as simplified diagrams of sea chest locations for use in blanking these hull openings. These diagrams also aided Yard staff with formulating cost estimates for individual work items.
Approximately 3,000 gallons of residual Navy Special Fuel Oil (NSFO) remained in the ship's fuel tanks and a plan for cleaning tanks at TANEY's berth in the Inner Harbor was contracted out. The cleaning and disposal of residual fuel prior to the yard period was undertaken as a cost-saving measure and included donated tank-truck services. Tank cleaning was begun in the second week of January 2003 and the method proposed by the contractor was to use 3,000 PSI heated pressure washers to clean tank sides, followed by diesel fuel to dilute the residual NSFO in the tank bottoms to a point where it could be pumped into the tank truck. Tank cleaning was not successful, primarily due to the extreme low water and atmospheric temperatures which prevented the old fuel from liquefying to a pumpable state. Proposals to use the ship's existing fuel oil heating coils were judged to be impractical. An unsuccessful attempt was also made to raise the fuel tank temperature with portable copper steam coils tied to the ship's steam heating system.
The movement of TANEY to the US Coast Guard Yard was a multi-step process involving a wide array of donated services and equipment. The temporary removal of the 26-ton pedestrian bridge astern of the ship was partly donated by the Martin-Imbach Corporation, along with towing services provided by Smith's Shipyard. Martin Imbach also donated the use of a trailer mounted 60 kilowatt diesel generator adequate for supplying ship's lighting and power for the heating boiler. Towing for the movement from the Inner Harbor to Curtis Bay was donated by Moran Towing. Aboard for the trip to the Yard were approximately 50 invited guests and four Damage Controlmen from the US Coast Guard Training Center, Yorktown (VA) who volunteered as duty DC's for the trip.
4. Docking and Hull Cleaning
TANEY was dry docked on Friday 14 March 2003. Placing the vessel on the synchro-lift was a multi-hour operation which involved four distinct stages which began with the movement of the ship into position over the submerged lift via tugs, followed by the positioning the ship directly in line with the submerged blocks via rope winches. The third stage was the actual raising of the lift, during which the blocks were manually pulled into place by line handlers aboard the ship. The final stage was the movement of the ship on the blocking carriage to its designated position on the working portion of the ship lift.
TANEY on the synchro-lift blocking carriage next to an active buoy tender.
The first view of the underwater hull body revealed moderate marine growth with isolated areas of serious corrosion and pitting. Overall, most observers agreed that the hull appeared to be in better condition than they had predicted.
High pressure water blasting removes marine growth, old paint and corrosion from TANEY's hull.
Hull cleaning was achieved via 40,000 PSI hydroblasting and took approximately 11 working days to complete. The removal of marine growth and paint down to bare metal revealed an existing profile of 6 to 8 mils throughout the hull. The existing profile negated the planned slurry blast option. Some difficulty with completely removing the 1983 "Mare Island" system was initially experienced however the museum insisted on and ultimately received bare metal condition.
The finished surface condition of the shell plating following hydroblasting was visibly different from that of traditional grit blasting. Rather than a bright metal finish, the hull was left with a residual rust film which, according to Yard personnel, as well as other marine repair industry specialists, will still provide for excellent coating performance from modern "surface-tolerant epoxy" paints; the essential step is the elimination of loose "bloom rust" with 3,000 PSI pressure wash immediately prior to top coating.
3. Hull Patches
Despite fears of frequent through-hull perforations, especially at the waterline, there were relatively few during the hydroblasting process. The two most serious hull breaches caused were two 3-4" diameter holes in the shaft alleys, one each port and starboard Each of these holes was located directly beneath, or immediately adjacent to a bronze bilge suction pipe and was the result of long-term interior dissimilar metal corrosion. These holes were repaired with welded steel doubler plates (7/16" ABS Grade A mild steel). This repair was complicated by the proximity of the holes to Fuel Tank D-410-F, which contained residual fuel, on the centerline between the shaft alleys. Clearance was obtained from the marine chemist to locally clean the tank at the bulkheads adjoining the shaft alley. The chemist specifically forbade the use of inserted patches (as opposed to doublers) due to the risk of excessive heat build-up near the fuel tank during the cropping phase.
Holes in the bottom of the port shaft alley made by hydroblasting.
An additional hole, approximately 1/2" diameter was made in the shell plating in the Fireroom, starboard side at approximately Frame 75. This small hole was immediately outboard of a longitudinal and was not evident from inside the ship. This hole was repaired with Belzona 1111.
A 1/8" diameter hole was made in the engine room shell plating, approximately Frame 79, four feet starboard of the keel. This was not detected until the ship was fleeted and was repaired afterward with a steel doubler plate.
A small pinhole was made at approximately Frame 93 port, in the Auxiliary Machinery Room, approximately 3 feet below the discharge for the ship's distilling plant. This hole was discovered only after the ship was re-floated a second time and was repaired with a doubler plate welded inside.
The three pre-existing holes which were temporarily patched before dry docking were repaired with Belzona 1111 after the old patches were cut away and new steel nuts and bolts were inserted into the holes.
4. Weeping Rivets
Following hydroblasting, several weeping rivets were discovered in sections of the shell plating outside of full or partly full diesel, fuel oil, or water tanks. One weeping rivet was discovered on the extreme bow, starboard side, from which water was seeping from the forepeak tank. This rivet was pined with a hammer until closed and then patched with Belzona 1111. One additional rivet was weeping in the shell plating outside of Fuel Oil Tank D-421-F and was patched with Belzona 1291 stick putty. The Belzona 1291 putty was also used on weeping rivets from tank D-417-F.
Weeping rivets revealed by residual fuel streaks outside Fuel Tank D-417-F.
Belzona 1111 is applied over a weeping rivet by the Belzona tech rep.
7. Corrosion Treatment
The worst areas of corrosion were near the waterline from the stern to approximately Frame 50 (the shell plating forward of Frame 50 was not free of corrosion and pitting, but generally better than aft). Belzona 1111 "Super Metal" epoxy compound was applied to deep pits and visually wasted rivets in this area, and was followed by a two-coat belt of Belzona 5811 "Splash Zone" paint. The 5811 product was applied by roller to the area 12 inches above and 18 inches below the waterline. Each coat was approximately 10 mils thick. Surface preparation was overseen by the Belzona tech rep who specified that in lieu of grit blasting, areas to which Belzona 1111 would be applied should be mechanically cleaned of rust followed by xylene degreaser. Surface preparation for 5811 "Splash Zone" was the same as surface-tolerant epoxy paint. Belzona 1111 is applied over a weeping rivet by the Belzona tech rep. In addition to the most obvious areas of wastage near the waterline, the underwater hull body was carefully examined by museum staff and areas of badly wasted rivets and deep pitting elsewhere were identified for treatment with Belzona 1111.
Partly wasted rivet heads; the chalk line visible indicates that these were earmarked for Belzona 1111 application.
8. Ultrasonic Gauging of Hull Thickness
Ultrasonic testing was carried out on selected portions of the hull to sample the level of wastage. The primary areas tested were a section of the port and starboard midships along the wind/water area, shell plating around the holes made in the shaft alley, a sampling of the plating in the keel strake of the Auxiliary Machinery Room, the plating surrounding pit log opening, and a section in the Fresh Water Pump Room. The Auxiliary Machinery Room, Pit Log Room and Fresh Water Pump Room areas were targeted due to concerns from visible internal rust.
A summary of findings is as follows:
The permanent closure of sea chests was identified as an important step for the long term watertight integrity of the ship. During the planning stages the museum created drawings showing sea chest arrangement and location throughout the hull for use in cost estimates, and as a working guide for Yard welders. A total of eighteen sea chests were identified for permanent closure using welded steel plate.
No. 1 Main Condenser Discharge is prepped for blanking. Here a Yard welder uses a cutting torch to remove the sea scoop so that a steel insert can be fitted. Note the spot-application of Belzona 1111 to wasted rivets surrounding the sea chest.
Yard welders prepped sea chests by cutting away steel gratings and scoops where necessary then welded inserts made of 7/16" ABS Grade A mild steel over sixteen of the eighteen sea chests. The two exceptions were the emergency diesel generator suction and discharge located between Frames 119 and 128, just starboard of the skeg. These were not blanked due to the impossibility of cleaning and gas freeing the Emergency Diesel Generator Room bilge within the availability window. This bilge contained a considerable amount of residual diesel fuel which had seeped from the diesel engine over time.
Two transducers, port and starboard, at approximately Frame 45, were inspected and found to be intact. These were coated along with the hull.
No. 1 Main Condenser Injection shown with strainer removed.
A steel blank is welded in place.
10. Propellers and Shafts
The stern tubes received new packing which was tightened to prevent seepage. Yard staff advised that the packing could be re-tightened in time should seepage at the stern tubes recur.
TANEY's two 3,400 lb bronze propellers were permanently removed to decrease the potential for dissimilar metal corrosion near the screws. Had the Yard been unable to remove the screws, the secondary plan was to coat these along with the hull. The 1983 fiberglass wrapping on the propeller shafts aft of the stern tubes was found to be intact and received no further treatment.
The starboard propeller is removed.
11. Zinc Anodes
TANEY's in-service zinc arrangement from the 1980s called for a total of thirty-two 6"x12", 23 lb zinc anodes welded to the hull. 24 of these were clustered around the screws and rudder and another 4 were attached to each bilge keel. The museum developed an alternative zinc plan intended to better protect the entire hull over time, and which allows for zinc renewal by a diver. This plan called for a total of 40 anodes to be attached to the hull via welded stainless steel studs, approximately evenly spaced but avoiding riveted seems and fuel tanks which had not been gas-freed. 40-pound single strap zincs were substituted for the standard 23-pound plates. The plan originally called for zinc attachment to the aft skeg at four locations, but was modified in order to forgo the time and expense of gas-freeing the skeg. Instead, additional zincs were attached to the forward and aft propeller shaft struts. One zinc per side was also eliminated from the section forward of the bilge keel due to welding concerns near fuel oil tanks aft of Frame 51. A total of thirty eight 40 lb anodes were attached at the locations shown on the diagram.
A 40-pound zinc anode attached to the shell plating on TANEY's starboard bow.
Anodes attached to the starboard propeller shaft struts and shell plating above the shaft.
After hydro blasting, corrosion treatment, doubler plate, sea chest, and zinc stud welding was complete, two coats of Ameron 385 epoxy paint with a glass flake additive was sprayed over the entire underwater hull body from the keel to 12 inches above the waterline. Immediately prior to the application of the first coat, the hull was pressure washed to remove loose rust bloom and then allowed to dry.
25 gallons of Ameron ABC#3 ablative anti-fouling paint was donated for the project and a belt was applied approximately 18" above and below the waterline. Had anti-fouling paint not been donated, it is unlikely that the museum would have opted for this additional measure considering its high cost and relative ineffectiveness for stationary vessels.
Coating consumption over the approximately 14,000 -square-feet of underwater hull body was 150 gallons each of Ameron #385 red and black epoxy paint and 60 gallons of Ameron #880 Glass Flake additive.
The first coat of Ameron 385 epoxy paint with glass flake additive is applied to the hull. The glass flake additive is intended to improve coating durability.
After a one day delay due to high winds, TANEY was refloated on 8 April 2003. During this multi-hour operation the synchro-lift was lowered to a point one foot above TANEY's flotation waterline and held there while compartment checks were made. In the days prior to fleeting, all fuel tank manhole covers were removed and the tanks ventilated and checked for oxygen content so that entry for inspection was possible.
For the compartment checks twelve active duty personnel from the cutters MARIA BRAY and GALLATIN were recruited to assist the museum staff and Yard personnel with efficient compartment surveys, and with line handling. The group was divided into six two-man teams with each team responsible for an individual zone of several compartments and spaces.
During fleeting, one weeping rivet was discovered in the Auxiliary Machinery Room, port side, approximately Frame 92. Additionally, a pinhole leak in the shell plating was discovered in the Engine Room at approximately Frame 79 some four feet outboard of the keel. A wooden DC plug was inserted into this hole. Fuel tanks were inspected visually and two (D-409-E and D-413-F) that were suspected of containing weeping rivets and were entered. What was thought originally to be audible leaks proved to be the sound of water lapping against the outside of the hull. After the ship was returned to the lift, a doubler plate was welded to the hole in the Engine Room shell plating, and Belzona 1111 was applied to the weeping rivet in Auxiliary Machinery.
Two leaks were discovered in areas that had been covered by the blocks. One weeping rivet located outside fuel tank D-417F seeped residual fuel oil after hydro blasting and was cleaned and treated with Belzona 1291, and then coated. A pinhole leak in the bottom of the skeg also appeared at approximately Frame 130 as painters were applying the first coat of Ameron 385. The skeg was drained of the seawater, which had apparently seeped in, ventilated with compressed air, then the hole was welded closed
On 11 April TANEY was refloated for the final time and compartment checks were carried out as before. During these checks, a pinhole leak was discovered in the Auxiliary Machinery Room on the port side approximately three feet below the brine discharge for the ship's distilling plant. While the ideal solution was to return to the synchro-lift for the installation of an exterior doubler plate, availability was extremely limited. A plan was put forth by the Yard staff for a welded interior doubler followed by a diver-applied coat of Hycote 151 underwater coating to replace the Ameron 385 burned away during welding. The museum opted instead for the construction of an exterior portable cofferdam to fit the section of the hull containing the leak. Once pumped dry, the cofferdam allowed exposure of the shell plating outside the doubler so that a coating of Ameron 385 paint could be applied.
14. Additional Projects:
As funding became available, the museum was able to consider additional work projects above the waterline. The most urgent of these was the replacement of the yardarm on the ship's main (aft) mast which was badly wasted and in danger of detaching itself. After examination by estimators from the Yard structural shop, the museum opted to replace the entire yardarm with a new one fabricated to the specifications of the ship's 1964 tripod mast blueprint. Several proposals for reinforcing the existing yardarm with a series of welded doubler plates and stiffeners were considered, but estimates for these were no more cost-effective, and considerably less structurally sound, than complete replacement with new material.
The newly fabricated yardarm is installed in TANEY's aft mast.