A Solution to the Inherent List on Nimitz Class Aircraft Carriers

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3.2.1 Ease of Removal As mentioned previously, Perma Ballast® is removable. In fact, removal costs were ^ assessed as well for this project on a per tank basis. For <strong>the</strong> purposes of this <strong>the</strong>sis, all tank prepping costs for ballast removal by BTI were also calculated by Norfolk Naval Shipyard (Code 256). It was estimated that it would cost approximately $78,652 for labor and material <strong>to</strong> remove/reinstall accesses and interferences for one 8"" deck tank, and approximately $63,412 for labor and material <strong>to</strong> remove/reinstall accesses for one 2"^* deck tank. Ballast removal costs were also obtained from BTI. It was determined that it would be best for BTI <strong>to</strong> actually remove <strong>the</strong> ballast and dispose of it due <strong>to</strong> <strong>the</strong> high costs involved should a naval shipyard need <strong>to</strong> dispose of <strong>the</strong> ballast. For ballast removal, BTI will charge a fixed fee • of $100,000 for locating and utilizing <strong>the</strong>ir equipment and approximately $395 <strong>to</strong> remove <strong>the</strong> ballast per I<strong>to</strong>n. They also estimated approximately $65 per I<strong>to</strong>n <strong>to</strong> dispose of it. All pricing is based on disposal of 100% of <strong>the</strong> water used <strong>to</strong> re-slurry <strong>the</strong> material. I* For example, a 1.5 degree list correction would require approximately 400 I<strong>to</strong>n of ballast and would need <strong>to</strong> be removed from two 2"*^ deck tanks. This would result in a <strong>to</strong>tal removal ^ cost of $347,412 of which $284,000 is for <strong>the</strong> ballast removal and $63,412 is for removing and reinstalling accesses. It should be noted that this ballast addition is only as permanent a solution as it needs <strong>to</strong> be. For example, should future modifications entail replacing <strong>the</strong> old Nimitz island ^ with a new CVN 76 island, it would <strong>the</strong>n be desirable and cost effective <strong>to</strong> remove this ballast. 3.2.2 Evidence Perma Ballast® is non-corrosive Recently, <strong>the</strong> American Bureau of Shipping (ABS) required a sealift conversion vessel that installed this Perma Ballast® in 1984 <strong>to</strong> remove its ballast. Concern had arisen because a tank inspection revealed that corrosion coupons had undergone significant weight loss. ti 48
Corrosion coupons are placed in all tanks that have Perma Ballast® installed so that periodic tank inspections can be made <strong>to</strong> determine if corrosion exists. It turned out that <strong>the</strong> corrosion coupons were improperly attached <strong>to</strong> <strong>the</strong> manhole covers and only rested in <strong>the</strong> <strong>to</strong>ps of <strong>the</strong> beds of Perma Ballast®. The corrosion coupons should be hung on chains and buried within <strong>the</strong> bed of ballast. Over <strong>the</strong> years, <strong>the</strong> coupons were repeatedly exposed <strong>to</strong> air and water during inspections, ra<strong>the</strong>r than being properly re-installed in<strong>to</strong> <strong>the</strong> Perma Ballast®. ABS did report, however, that all 4 of <strong>the</strong> tanks were in perfect condition after <strong>the</strong> Perma Ballast® removal, almost 20 years after initial installation. Actual cost data was also obtained from this vessel. The cost <strong>to</strong> cut in<strong>to</strong> 8 compartments and remove <strong>the</strong> ballast was approximately $250,000. The cost <strong>to</strong> replace <strong>the</strong> steel and reweld <strong>the</strong> hull after <strong>the</strong> ballast was reinstalled was approximately $100,000. As one can see, <strong>the</strong> removal costs are relatively low and experience proves that corrosion will not be a concern. 49
Page 1 and 2: A Solution <strong
Page 3 and 4: A Solution <strong
Page 5 and 6: Table of Contents Abstract 3 Acknow
Page 7 and 8: 1.0 Introduction 1.1 Motivation Air
Page 9 and 10: class. Changes to
Page 11 and 12: classified into fo
Page 13 and 14: o Control the KG g
Page 15 and 16: the intact stabili
Page 17 and 18: for ships propulsion, respectively.
Page 19 and 20: combined with the
Page 21 and 22: 1.3.7 Ballast Addition 1.3.7.1 Wate
Page 23 and 24: 2% entrained air (by volume) in <st
Page 25 and 26: Tank name Tank volume Ballast type
Page 27 and 28: was successfully performed and <str
Page 29 and 30: of each tank's location was added,
Page 31 and 32: 2.3 Preliminary Decision-Making Cos
Page 33 and 34: All further costin
Page 35 and 36: 2.4 Structural Analysis One tank on
Page 37 and 38: this pressure. This resulted in a r
Page 39 and 40: 2.4.1 Structural Modifications 2.4.
Page 41 and 42: Main Deck Shell FR 165 - FR 180 Tra
Page 43 and 44: 2.4.1.3 Modifications to</s
Page 45 and 46: 3.1 Final POSSE Results The minimum
Page 47: Table 6: Final Cost, Weight Additio
Page 51 and 52: 5.0 Recommendations 1. As can be se
Page 53 and 54: References [I] Design Data Sheet 07
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Page 95 and 96: Stress Calculations: k = coefficien
Page 97 and 98: Stress Calculations: k = coefficien
Page 99 and 100:
FR 165 - FR 180 Transverse Bulkhead
Page 101 and 102:
Design of Plating for Surface Ships
Page 103 and 104:
Stress Calculations: k = coefficien
Page 105 and 106:
Main Deck Shell FR 165 - FR 180 Tra
Page 107 and 108:
Calculations to De
Page 109 and 110:
structural Analysis for Compartment
Page 111 and 112:
Page 113 and 114:
Calculations to De
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Calculations to De
Page 121 and 122:
Stress Calculations: Stiffening k =
Page 123 and 124:
Resulting Pressure on Shell Plating
Page 125 and 126:
Calculations to De
Page 127 and 128:
Stress Calculations for 227 I<stron
Page 129 and 130:
Resulting Pressure on Inner Longitu
Page 131 and 132:
Calculations to De
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Stress Calculations k = coefficient
Page 139 and 140:
Resulting Pressure on Transverse Bu
Page 141 and 142:
Calculations to De
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Page 147 and 148:
Stress Calculations: k = coefficien
Page 149 and 150:
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MATERIAL WORK SHEET PERMA BALLAST®
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A Solution to the Inherent List on Nimitz Class Aircraft Carriers

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