Text

Engine Rebuild Rept:Motor Vessel Columbia for State of Ak
	ML20098B599
Person / Time
Site:	River Bend
Issue date:	03/31/1981
From:	Jeffrey Jacobson; JACOBSON, J.O., TODD SHIPYARDS
To:	;
Shared Package
ML20093C471	List: ML20093C467; ML20093C472; ML20093C478; ML20098B538; ML20098B554; ML20098B571; ML20098B581; ML20098B599;
References
	NUDOCS 8409260170
	Download: ML20098B599 (58)
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ENGINE REBUILD REPORT Motor Vessel Columbia for State of Alaska Division of Marine Transportation Depart:aent of Public Works by Jon O. Jacobson 6869 Woodlawn N.E.

Seattle, WA 98115 for Todd Pacific Shipyards Corporation 1801 16th Avenue S.W.

Seattle, WA 98124 March 31, 1981 5409260170 840910 PDR ADOCK 05000458 G

PDR

INTRODUCTION The engines of the Motor Vessel Columbia were examined in late January, 1981 and a preliminary report describing their condition was prepared.

1 The present report is the continuation of the earlier work and desc::ibes the condition of the engines during rebuilding through March,1981.

Assessment of the initial data, tests performed, and conclusions drawn are the content of this report.

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TADLE OF CONTENTS Introduction.

.i Table of Contents.

. 11 List of Tables...

. iii List of Figures..................... iii I ENGINE BLOCKS.

. I-1 Bore and Counterbore Diameter.

. I-1 Counterbore Lip..

. I-10 Torque Level of 'lolte Holding the Blocks to the Base... I-12 II CYLINDER LINERS.

. II-l Changes in Diameters................... II-1 Changes in Clamping Capability

. II-6 III CYLINDER HEADS.

. III-1 IV NONDESTRUCTIVE TESTING.

. IV-1 Blocks.......

. IV-1 Base.

. IV-6 V ENGINE ALIGNMENT.

. V-1 Structural Alignment.

. V-1 Port Engine, Right Bank

. V-1 Port Engine, Lef t Bank.

. V-1 Starboard Engine, night Bank.

. V-10 Starboard Engine, Lef t Bank

. V-10 Port Engim, Base.

. V-10 Crankshaft Deflection.

. v-10

. V-II Petorquing.

. VI-1 VT CCNCLUSIONS.

.............. e......

. VII-1 VII RECCMMENDATIONS.

UII APPENDIX.

............... V!!!

f 11 1

TABLES Table 1.

Port Main Engine, M/V Columbia.......... I-2 Table 2.

Port Main Engine, M/V Columbia.......... I-3 Table 3.

Starboard Main Engine, M/V Columbia.

I-4 Table 4.

Starboard Main Engine, M/V Columbia...

. I-5 Table 5.

Crush, Starboard Main Engine..

. II-7 Table 6.

Counterbore, Port Main Engine.

. II-8 FIGURES Figure 1.

Cylinder Configuration, Engine Block

. I-6 Figure 2.

Upper Cylinder Liner.............. I-7 Figure 3.

Bore Diameter, Engine Diocks, December 19, 1980. I-8 Figure 4.

Counterbore and Stud Configuration.

. I-11 Figure 5.

Block to Crankcase Bolts, Starboard Main Engine, December 31, 1980...

. I-13 Figure 6.

Block to Crankcase Bolts, Port Main Engine, December 31, 1980.

. I-14 Figure 7.

Engine Block to Base Hold-down Force I-15 Figtte 8.

Permanent Liner Deformation, Bore Diameter, Starboard Main Engine.

. II-2 Figure 9.

Permanent Deformation of the Cylinder Bore and the Liner Bore, Starboard Main Engine.

. II-3 Figure 10. Average Difference Between the Block.and the Liner Bore Diameter, Starboard Main Engine.

. II-4 Figure 11. Liner Bore, Port Main Engine.

. II-5 Figure 12. Ncndestructive Testing, Starboard Main Engine.. r7-2 Figure 13. Nondestructive Testing. Port Main Engine.

. TV-3 Figure 14. Nondestructive Testing, Cylinder Block, Delanination Cracks....

. IV-4 Figure 15. Nondestructive Testing, Cylinder Block, Shear Cracks, Counterbore Lip...

. IV-5 Figure 16. Elevation of the Air Side of the Cylinder Block for the Right Bank, Port Main Engine... V-2 Figure 17. Elevation of the Exhaust Side of the Cylinder Block for the right Bank, Port Main Engine.

. V-3 iii

Figuro 18.

Elcvstion of tha Exhnu3t Sid3 of tho Cylindar Block for the Lef t Bank, Port Main Engine.

V-4 l

Figure 19.

Elevation of the Air Side of the Cylinder Block for the Lef t Bank, Port Main Engine.

V-5 l

Figure 20.

Elevation of the Air Side of the Cylinder Block for the Right Bank, Starboard Main Engine. V-6 Figure 21.

Elevation of the Exhaust Side of the cylinder l

Block for the Right Bank, Starboard Main Engine. V-7 Figure 22.

Elevation of the Exhaust Side of the Cylinder Block for the Lef t Bank, Starboard Main Engine.

V-8 Figure 23.

Elevation of the Air Side of the Cylinder Block for the Lef t Bank, Starboard Main Engine.

v-9 Figure 24.

Elevation of the Subbase of the Port Main Engine. V-11 Figure 25.

Crank Defisction. of the Port Main Engine, Hot V-13 Figure 26.

Crank Deflection of the Port Main Engine, Cold.. V-14 Figure 27.

Change in Crank Deflection for the Port Main V-15 Engine, Hot vs Cold....

Figure 28.

Elevation of Cylinder Blocks for Port Main Engine after Relaxing and Retorquing All Vo16 Structural Bolts.

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9 I

ENGINE BLOCKS The Enterprise engine has 16 cylinders in a V (veel configuration with two separate 8-cylinder blocks bolted to the base.

Individual cylinder liners are held in place by the clamping force of the head installation and are sealed at the bottom with multiple o-ring seals. The top of the liner is held in the block with a lip (.250 x 1.5 inch) that is clamped by the head. The block is counterbored to accept this lip.

A major concern of engine block examination was the deformation in the counterbore and the landing surface for the liner lip when compared to the original or design dimensions.

Data recorded during December,1980 and shown in Tables 1 to 4 (pp. I-2 to I-5) indicated the need for an in-depth look at the blocks. Also, one of the tie-bolts holding the blocks to the base had S*pT broken on n--==k=r 26, 1980. Upon replacement, all the tie-bolts had simply been retorqued to factory levels and a record kept of when the nuts had broken free.

$k The areas of the engine block examined, measured, and reported in this section are the following:

1) the diameters of the bore and counterbore,

2) the counterbore lip holding the cylinder liner, and 3) the torque levels of the bolts holding the blocks to the base.

Bore and Counterbore Diameters The firing surface of the block and bore and counterbore dimensions are shown in Figure 1 (p. I-6).

The corresponding dimensions for the cylinder liners are shown in Figure 2 (p. I-7).

Measurements of the diameter of the bore of the blocks were taken at perpendicular directions to show the degree to which the openings had deformed, symmetrically and non-symmetrically.

These values are plottei in Figure 3 (p. I-8) for both main engines.

The 3-9 o' clock direction shown in Figure 3 is in the longitudinal

l~2 Table 1.

Port Main Engine. M/V Columbia Counter-Liner Counter-Liner Block Laner 12-78 C21 Fee Crush bore Depth Flante Thick bore ID F1. CD TD CS Crush verksook 1

12

.003 1.5055 1.506 19.523 19.494 19.004-18.995 3

.0022 1.505 1.504 19.516 19.494 19.00s 18.994

.0055 6

.002 1.505 1.506 9

.0013 1.504 1.503 2

12

.005 1.5055 1.505 19.522 19.504 19.009 18.997 3

.0035 1.5 04 1.504 19.514 19.495 19.006 18.997 6

.003 1.504 1.507

.006

.0055 9

.0025 1.504 1.505 3

12

.006 1.513 1.506 19.522 19.499 19.010

.0059 3

.006 1.513 1.505 19.514 19.497 19.004

.0059

.0025 6

.005 1.5 15 1.505

.0G25

.006 9

.006 1.514 1.505

.0025 4

12

.003 1.503 1.505 19.518 19.497 19.010 18.998

.0053 3

.0045 1.5035 1.505 19.509 19.490 19.002 18.995

.0095

.005 6

.002 1.5045 1.506

.006

.009 9

.0035 1.503 1.504

.007 5

12

.003 1.504 1.504 19.524 19.495 19.012 18.997

.0075 3

.0027 1.3035 1.503 19.511 19.494 19.C03 18.996

.005

.005 6

.002 1.5035 1.5035

.006

.0080 9

.0023 1.504 1.504

.0075 6

12

.0025 1.504 1.507 19.525 19.497 19.011 18.995

.0075 3

.0025 1.5C5 1.503 19.512 19.496 19.008 18.991

.0072

.005 6

.002 1.5045 1.506

.005

.008 9

.0027 1.505 1.504

.008 7

12

.002 1.503 1.506 19.522 19.495 19.008 18.998

.007

.006 3

.0017 1.5045 1.505 19.515 19.494 19.005 18.997

.008

.0085 6

.002 1.505 1.506

.007 9

.0017 1.5055 1.507

.0075 l

8 12

.001 1.505 1.504 19.521 19.494 19.008 18.997

.004

.0035 3

.0015 1.505 1.504 19.514 19.493 19.006 18.994

.0105

.0105 6

.001 1.5055 1.504

.007 9

.001 1.506 1.505

.005 l

I l

I-3 t

Table 2.

Port Main Engine, M/V Columbia coinster-Liner Counter-Liner 81ock Liner 12-78 Cd Log Crueh bore Depth Flante thick bore ID F1. CD 1

CD Crush Workbook o

9 12

.004 1.505 1.505 19.520 19.494 19.006' 18.997

.3

.0027 1.504 1.505 19.516 19.495 19.005 18.997

.003 i

.003 1.504 1.505

.0CJS 9

.0017 1.504 1.505 10 12

.0025 1.503 1.505 19.520 19.495 19.008 18.998.005 3

.0028 1.502 1.505 19.516 19.494 19.005 18.996

.005 6

.0025 1.3025 1.503

.0065

.008 9

.0025 1.5025 1.503 11 12

.005 1.5035 1.504 19.523 19.498 19.009 18.997.005 3

.0037 1.5055 1.504 19.512 19.497 29.0 % 18.998.006

.0035 6

.001 1.509 1.504

.0065

.0065 9

.000 1.506 1.505

.006 12 12

.001 1.503 1.505 19.328 19.495 19.013 18.997.006 3

.0025 1.503 1.505 19.512 19.496 19.002 18.997.0055

.0055 6

.002 1.502 1.505

.0055

.007 9

.0018 1.504 1.505

.0055 IJ 12

.001 1.5065 1.502 19.526 19.493 19.012 18.997.005 3

.0007 1.507 1.503 19.512 19.493 19.003 18.997.005

.004 6

.002 1.505 1.502

.0075

.008

=

9

.0007 1.505 1.503

.0071 14 12

.002 1.505 1.505 19.525 19.495 19.010 18.999.0055 3

.0015 1.507 1.505 19.515 19.493 19.004 18.997

.004 6

.001 1.505 1.505

.004

.0065 9

.001 1.507 1.505

.004 15 12

.002 1.505 1.505 9.523 19.495 19.010 18.998.005 3

.0025 1.504 1.505 19.515 19.494 19.005 18.997.0055

.004 6

.002 1.505 1.505

.004

.005

)

9

.0022 1.505 1.505 l

.0042 I

16 12

.002 1.505 1.507 19.525 19.496 19.011 18.999.005

+

3

.0017 1.505 1.506 19.516 19.494 19.005 18.997.006

.0045 6

.001 1.507 1.506

.006

.006 9

.002 1.507 1.506

.0095 w

+ -,

I-4 Table 3.

Starboard Main Engine, M/V Columbia Counter-f.iner Counter-Liner Block Liner 12-78 gj, 'os Crush bote Death Flanne

hick bore ID F1. CD ID CD Crush Workbook 1

12

.005 1.502 1.305 19.520 19.499 19.007 19.001-3

.0045

.504

.303

.317 19.497

.004 18.995 6

.004

.301

.506

.009

.007 9

.0045

.502

.504 2

12

.005 1.303 1.304 19.522 19.501 19.009 18.997 3

.0035

.500

.304

.314 19.500

.002 18.995 6

.003

.304

.018

.0055 9

.0045

.504

.504 3

12

.004 1.503 1.505 19.526 19.010 3

.004

.303

.504

.313

.003 18.996 6

.004

.303

.506

.006

.007 9

.004

.304

.505 4

12

.004 1.304 1.506 19 325 19.012 18.997 3

.0035

.302

.306

.310 18.996 6

.004

.303

.307 19.001

.006

.0055 9

.004

.303

.306 5

12

.004 1.503 1.504 19.320 19.309 19.011 19.006 3

.005

.303

.309

.002 6

.004

.301

.504

.021

.045 9

.006

.504

.306 6

12

.006 1.301 1.306 19.322 19.498 19.009 19.001 3

.005

.301

.506

.3 12 19.443

.003 18.995 6

.005

.301

.305

.008

.0065 9

.006

.302

.506 7

12

.006 1.503 1.506 19.521 19.496 19.009 19.000 3

.005

.301

.306

.514 19.496

.004 18.999 6

.006

.302

.306

.001

.005 9

.0035

.303

.506 8

12

.006 1.503 1.507 19.519 19.500 19.008 19.002 3

.006

.501

.303

.316 19.492

.006 18.992 4

.005

.303

.506

.009

.0055 9

.0055

.503

.506

I-5 Table 4.

Starboard Main Engine, M/V Columbia ces ser-user con ser-uner Block user 12-78 CyJ, g crush bore Desth Ftante Tbick bore ID T1. CO ID CD Crush Workbook 9

12

.009 1.304 1.506 19.319 1*.006 3

.J075

.302

.306

.316

.006 6

.010

.303

.307

.006 9

.0095

.302

.002S

.0800 10 12

.005 1.302 1.506 19.323 19.009 3

.005

.303

.3 15

.004 18.999 6

.006

.304

.006

.005 9

.005

.303 11 12

.005 1.303 1.306 19.328 19.011 3

.0045

.303

.306

.313

.001 6

.003

.305

.007

.0055 9

.0C35

.3C2 12 12

.004 1.303 1.305 19.326 19.015 3

.005

.304

.305

.311

.003 6

.004

.305

.005

.0035 9

.004

.304

.306 13 12

.004 1.303 1.306 19.326 19.012 3

.004

.302

.305

.316

.002 6

004

.303

.306

.009

.0045 9

.004

.302

.303 14 12

.004 1.303 1.506 19.328 19.009 3

.0045

.302 1.304

.316

.001 6

.004

.304

.006

.0045 9

.003

.302

.306 15 12

.004 1.303 19.524 19.009 3

.004

.302

.315

.006 6

.004

.303

.003

.005 9

.0033

.500

.304 16 13

.005 1.304 1.504 19.323 19.007 3

.0033

.302

.304

.324

.006 6

.003

.303

.304

.004

.004 9

.0035

.303

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Figure 3.

Bore Diameter, Engine Blocks, M/V Columbia, December 19, 1980

I-9 direction of the block and the 6 - 12 o' clock direction is perpendicular to this. These directions are as if one is standing beside the engine to view the dimensions.

Figure 3 data show a gradual increase in all cylinder diameters and a pattern of non-symmetrical change similar for all four blocks. All the bore diameters have grown uniformly between.006 and.007 inch over the lifetime of the engine. This increase indicates an interstitial flow within the metal-lic structure of the block that has allowed a permanent change in dimensions.

Interstitial flow is an effect of creep whereby metal changes slowly in dimension in response to a stress below the yield point. Effects of creep N,

occur under several conditions. The conditions present in the Enterprise

\\

engine are increased temperatures associated with operating stresses to pro-duce a permanent strain on the interior surface of the block bore. Although the strain for unifdrm deformation-368 micro-inches corresponding to a strass of 11,000 psi-ir within acceptable limits for the cast iron material of the block, when combined with other deformations, its effects contribute to speci-fic forms of metallic failure.

In additi n to the uniform increase in all bore diameters, there is a pattern of non uniform deformation. While the cylinders at the ends of the i

blocks remain essentially circular the cylinders at the center show a gradual change to a maximum ovainess of.012 to.015 inch. This ovainess is a result of dimensional changes beyond the uniform increase in diameter to which all the cylinders are subject.

It indicates that the structural webs between the cylinders are subject to the effects of creep.

Because the center webs are heated during operation while the cuter por-TV..

i

'S l

tion of the end cylinders remain et room temperature, the effects of' creep will i

be seen more in the hotter than in the cooler regions. Creep has produced a t

1 maximum of approximately 1,000 micro-inch of strain with a corresponding stress

,.,,c, v-._

I-10 of 30,000 psi. A visual concept of this is to imagine adding an external clamp applied to the blocks to produce an equal but opposite stress on the engine in order to restore the cylinders to their circular shape.

Both uniform diameter increase and ovainess have resulted from metallic

'I'l creep.

Because the combined stresses (41,000 psi) are well above design limits for cast iron, metallic failure was expected in the intercylinder web areas cnd around the cylinder circumferences where the proximity of holes for cooling water and studs produce stress concentrations.

Metallic failure was found end is discussed in Section V, Nondestructive Testing.

Counterbore Lip The second major concern was the block's counterbore lip which holds the cylinder liner.

Excessively high stress due to liner clamping had caused metallic failure.

The bore of the block is nominally 19.000 inches and the counterbore, 19.500 inches.

The counterbore lip, with a width of.250 inch, must resist the force from pres:ressing the cylinder head studs.

When the total force generated by the studs is calculated, the compressive stress on the counterbore lip is in excess of 76,000 psi.

This value assumes the IG

.fE following:

1) the threads are well lubricated, 2) all forces are uniformly distributed, and 3) no out-of-trueness or other artifacts are present to increase this value. Because compressive stress occurred at an inside corner under tension, the corner was a prime area for inspection for metallic failure.

i Additional stress en the counterbore lip was caused by the near presence cf the termination of threads for the cylinder head studs as shown in Figure 4 (p. I-11).

Both counterbore depth and the beginning of the threads in the block are 1.500 inches below the block surface leaving only a.625 inch space between the two.

Because this space experiences extremely high stress concen- %

Iz tration it was exama.ied for the possibility of metal failure.

Various types were found.

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ggste 4 Cou"*

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I-12 Torque Level of Bolts Holdine *he Blocks to the Base on Septester 26, 1980, a bolt broke on the left rear block of the star-i board main engine. Temporary repairs were mada and the bolt was replaced on return to Seattle. During installation of the new belt, the torque levels of all block bolts were checked by noting when the nuts moved during a retor-quing procedure. The procedure used was to begin at one corner of the block and proceed down one side and back up the other. Figures 5 and 6 (pp. I-13

]

and I-14) show the recorded break-loore torque levels observed during this procedure and the force levels of preload in the bolts.

In Figure 7 (p. I-15), the force from the calculated preload by the four bolts surrounding each cylinder is compared to the maximum force generated by i

the firing pressure. The question is whether or not, in the partially torqued f

condition observed, there was sufficient structural iategrity in the prelcad i

foreas to keep the engine properly together.. The data show that for several cylinders on the starboard engine, preload force was inadequate, while on the port engine preload force was sufficient but not optimum.

l l

The biccks were removed from the base of the engine because of failures detected during nondestructive testing. Af ter the blocks were removed from i

both engines and the face of the base where they had been resting could be seen, the surface characteristics of the metal showed differences across the face.

Looking at the engine from the side, the top of the base beneath the blocks near the center of the engine showed a surface characteristic called fretting. Contiguous surfaces on the blocks showed similar fretting, like a corrosive etching. Where the pevious surface had been smooth, it was now rugged and irregular. No measurements were made.tsut the deepest groves were I

estimated at a millimeter (.040 inch).

Fretting is a corrosion-like wear of metal c. eurring when there is a small cyclic motion between two mating surfaces up.ter load.

In the case of

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3-13 T=d4 00 O

O O

T-2800 T=4500 T=4500 l

F=108,000#

F=67,200#

F=108,000#

4500 2800 4500 4500 O

O O

O 108,000 67,200 108,000 108,000 100 4

0 00 00 98,400 96,000 91,200 108,000 00 2

0 00 00 96,000 67,200 91,200 84,000 00 3

0 100 00

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96,000 88,800 96,000 88,800 100 3

0 00 00 98,400 84,000 72,000 76,500 4300 2500 4100 3400 O

O O

O 103,200 60,000 98,400 81,600 000 3 00 800 1 00 6,000 86,a00 A,200 81 00 000 3 00 - Broken, 3400 200-Replaced O

/,00 72, 00 9/26/80 ST,600 76, 00 l

l 71vuhael T = Torque (ft-lb)

F = Force (ft)

Figure 5.

Block to Crankease Bolts, Starboard Main Engine, December 31, 1980 i

I

I-14 T=

00 T=

0 T=

Oc T=

0 F=96,000 F=108,00C F=108,000 F=108,000 00 0

00 0

108,000 108,00C 108,000 96,000 00 00 00 4 00 96,000 108,00C 108,000 96, 00 00 50C 4500 4 00 108,000 108,00C 105,000 10,000 00 00 00 00 103,200 108,00C 108,000 108,000 i

00 00 00 00 98,400 108,00C 108,000 108,000 00 00 00 00 108,000 96,00C 108,000 100,800 00 00 00 00 100,300 108,00C' 96,000 91,200 00 00 00 00 93,600 108,000 9,600 93,600 l

Flvwheel T = Torque (ft-lb)

F = Force (ft)

Figure 6.

Block to Crankcase Bolts, Port Main Engine, December 31, 1980 J

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Engine Block to Base Hold-down Force l

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n.

I-16 the engines, motion, and consequently fretting, occurred because of the reduced 99 preload in the block bolts when the nuts were not fully torqued.

T Fretting did not occur solely because of reduced preload in the block bolts.

Although the pattern was similar in both engines, a greater amount of fretting was seen on the starboard engine where the lowest preloads were present.

There was also fretting in the areas where maxhnn= preloads were present. The author believes that a combination of lif ting of the blocks due to firing pressure and moment from the piston side thrust contributed to lif ting the blocks slightly more in the center of the engine than at the outside.

To reduce the possibility of fretting, maximum torque on the block bolts must be maintained at all times.

But, because of piston side thrust, it prob-ably cannot be eliminated, only minimized. The procedure by which the bolts are brought to full torque is critical and is explained under Encine Alignment, page V-12.

An ooservation of an interesting surface effect on the block face of the starboard engine requires mentioning. The lef t rear cerner of the lef t block had a circular etching with deep outward radiatino cracks up to 1/4 inch deep which appeared to be electrochemical 1y caused. The circular etching corresponded to a recess in the block, possibly a filled core. No other similar features were observed on the block.

I i

II CYLINDER LINERS The cylinder liners installed in the block can be removed and thus provide a renewable cylinder surface. Each liner is held in the block at the top by the bore and counterbore lip and at the bottom by the block bore.

The major holding force comes from the clamping by the head holding the liner against the counterbore lip. The radial tolerance between the cylinder liner and the block, nominally.005 inch, is removed during operation when the liner is heated. During operation, the surface contact pressure is estimated %b at 27,000 psi at the bore diameter (19.000 inches).

In addition to the metal-tcr-metal contact stresses at the bore and the counterbore lip, the liner is sealed at the top with a fire-ring inserted into a liner recess, a water seal in a head recess covering the edges of the block and liner, and at the bottom with multiple o-ring seals.

The cylinder liner problems studied were 1) changes in liner diameters, l

and 2) changes in clamping capability.

Changes in Diameters Because of deformation of the blocks, the cylinder liners, which must mate with the block for proper function, required examination.

These liners were measured at the same time as the blocks and their dimensions are shown in Tables 1, 2, 3 and 4 (pp. I-2 to I-5).

Bore diameters for the starboard and port main engines are shown in Fijures 8 and 11 (pp. II-2 and II-5).

The diameter changes indicating ovalness of the cylinder liners are less dramatic than those for the block and may not be overly significant. But the liners b

may not have been in the block in the same cylinder for the lifetime of the engine. Because deformation of the liners had to follow that of the block, the effects of permanent deformation were less. The liner and the blocks are probably of different material specifications and the liner material may not be as subject to creep as is the block.

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II-4 A comparison of the difference in deformation of the blocks and that of the cylinder linsrs is shown for the starboard engine in Figures 9 and 10 (pp. II-3 and II-4).

Figure 9 shows the average deformation of the block and the liners for each cylinder.

Figure 10 shows that the design clearance of

.005 inch had incrersed to a clearance of.009 inch. This difference explains why the lineria were easier to remove than when they were now.

Changes in Clamping capability The major stabilizing force for the cylinder liners during installation is provided by the clamping of the head on the lip of the liner. The lip is 19.500 inches outside giving a.250 inch support surface, and is nominally 1.500 inches high. Because of a small difference in dimensions the liner protrudes.004 inch above the block surface.

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called the " crush." When the studs holding the head in place are torqued to full value (3600 f t-lbs), the entire force of all bolts is borne by the liner

'j and the head is separated from the block surface.

When the engine was measured as recorded in Tables 1, 2, 3 and 4, it was found that the clamping capability-or er.Jh-had undergone dimensional changes.

Port main engine cylinder 3 had required machine work because of degradation.

The counterbore depth had been increased.013 inch and a spacer ring had been installed to restore the original crush.

(3 Measurements showed some loss of crush, possibly contributing to the failure of fire-ring seals. Data relating to crush has been abstracted from Tables 1, 2, 3 and 4 and presented in Tables 5 and 6 (pp. II-7 and II-8). ?5e liner lip is.001 to.002 inch deeper than specification. Discussions with ship personnel and measurements on new liners indicate they have been manu-l factured.002 inch larger than factory specifications providing a.006 inch I

designcrushheight./' The liners are maintaining their manufactured dimensions during their useful ' lifetime.

$I

II-7 Table 5.

Crush, Starboard Main Engine Counterborn Avg.

Less 1st.5 Liner Avg. Change

-3.75 1-9/4 2.25 2.75 18/4 4.5

.75 4

2-11/4 2.75 3.25 16/4 4.0

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.5 6-5/4 1.25 1.75 23/4 5.75 2.0 7

9/4 2.25 2.75 24/4 6.0 2.25 8 - 10/4 2.50 3.0 24/4 6.0 2.25 i

9-11/4 2.75 3.25 20/4 6.25 2.5 10 -

12/4 3.0 3.5 23/4 5.75 2.0 11 -

13/4 3.25 3.75 24/4 6.0 2.25 12 -

16/4 4.0 4.5 23/4 5.5 1.75 13 -

10/4 2.5 3.0 22/4 5.5 1.75 14 -

11/4 2.75 3.25 27/4 6.75 3.0 15 -

8/4 2.0 2.5 23 /4 5.75 2.0 16 -

12/4 3.0 3.5 17/4 4.25

.5 Avg. Value Avg. Loss =

Avg. Growth 1.50251 3.01 1.72 l

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II-8 I

i Table 6.

Counterbore, Port Main Engine Loss l

Average (i.e. +.5)

Liner Growth Avg. Crush l

1-19.5/4 4.875 5.375 21/4 5.25 1.5

.375 2-17.5/4 4.375 4.875 21/4 5.25 1.5

.875 3-5.5/4 13.75 14.25 21/4 5.25 1.5

-8.5 4-14/4 3.5 4.0 20/4 5.0 1.25 1.5 5-15 /4 3.75 4.25 16/4 4.0

.25

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.225 (excluding #3)

(excluding #3) i l

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1 II-9 Tables 5 and 6 show the counterbore depth of the starboard engine has increased by.003 inch and.005 inch for the port engine severely compromising i

the ability of the engine to fix the liners in place.

A design feature of the counterbore and lip may preclude avoiding the probles. The bece fmm the eight studs when tcrqued to 3600 ft-lbs must be borne on the.250 inch lip face producing a compressive stress in excess of 76,000 pai. This valbe is above the normal design limits for cast iron and, with the sharp interior corner, will be a source of recurring failure.

Section IV, Nondestructive Testing, discusses the failures observed.

These failures led to the decision to replace the. original blocks with new l

units. Because the design stresses were so high, there was no foreseeable way to prevent failures from occurring without a significant redesign of the liner-block landing surfaces.

e 1

9-l

III CYLINDER HEADS The cylinder heads on the main engines have shown an excessively high y'

failure rate. When the heads fail during operation, they are replaced with a new or reconditioned unit and the original is returned for renovation or scrap.

The problems identified by Alaska state personnel were warpage, crack-ing, loss of fire-ring seal, valve-stem blow-by, and the expected problems of valve wear.

Examination of the heads was confined to one unrefurbished head with G

2,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of use and two new heads. All units were visually inspected and j

the used head was sawed into quarter sectors for study. The valves were placed into the used head and the seat clearance checked with a.0015 inch guage.

Intake and exhaust closures showed no warpage.

Inspection of rebuild procedures at the.Duamish Machine Works indicated that some of the valve guides had come loose, allowing blow-by into the veilve chamber and possibly contributing to a misaligned seat closure. None of the heads currently being The maximum out ot-fla'tness was.002 J

reworked had problems with warpage.

inch with most measurements being.001 inch or less.

Interior surfaces of the new head showed weld repair in transition cor-

,C-nors excessive for a new casting.

It was surmised that the condition had been present in the used heads when they were new.

The used head, when cut, showed a weld repair en the firing face only partially filling a crack that extended through the entire thickness of the firing face.

Because of this repair and the amount of weld repair present in the head x-rays were used to further analyze the head. X-rays showed a few gas pockets from casting and two or three welds with minor defects. Overall, the repair procedures seem to have corrected the casting defects in the head and it is in reasonably

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l III-2 good condition. My opinion and that of Professor Paul Ford of the University i

of Washington is that the castings showed an excessive amount of casting flaws i

which, if not repaired, could produce head failures of undetectable and spuri-l ous occurrence. With the high cost of heads (dollars per pound) one would l

expect a higher quality product.

Inferences about the high frequency of head failure could be made with more specific historical infor: nation abcut the heads which were removed and

-refurbished or scraped.

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t IV NONDESTRUCTIVE TESTING The basic structural parts of the engine--the blocks and the bases--

were examined by nondestructive testing.

Testing began after presentation of a preliminary draft of the January 30, 1981 report.

Blocks The top surface of the blocks for both engines was tested. Data from ultrasound examination of the blocks are presented in Figures 12 and 13 (pp. IV-2 and IV-3) with details in Figures 14 and 15 (pp. IV-4 and IV-5).

Fractures seen most frequently were radial cracks extending out from the cylinder counterbore. The radial cracks were either in areas of stress con-centrations caused by holes for cooling water passage or stud drillings, or in the inter-web area between cylinders in the center of the block. The most destructive type of fracture was seen in cylinders 2 and 3 of the left bank of the starboard engine. Figure 14 shows the form of. the delamination crack where the cylinder liner lip was separating from the block structure. This 4

fracture prevented the liner from being properly installed and could have led to a catastrophic engine failure.

The fracture was caused by the following:

1.

high compressive stresses on the counterbore lip, 2.

localized stress condition from the combinations of sharp internal corner fer lip (1/32 inch radius),

j 3.

nearby drilling for waterjacket or stud,

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4.

termin.ation of stud threading at the same level, 5.

creep deformation, ar d 6.

fatigue.

l Because of the delamination erscks, one block was not serviceable, and so both blocks for the starboard engine were renewed.

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Nondestructive Testing, Cylinder Block, Delamination Cracks 4

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IV-8 The port engine, although showing radial cracks, did not have the dela-mination failure seen in the starboard engine. The port engine was renovated by boring the block to a larger dianter and resurfacing the counterbore lip to a consistent depth for all cylinders. When the first cuts were made on the counterbore lip, the exposed surface showed shear fractures extending downward in the counterbore lip. Specific ultrasound probes for curved surfaces con-firmed the shear fractures in cylinder 3 of the port engine. Cylinder 14 also had a shear fracture t.t the counterbore lip.

Base Using ultrasound nondestructive testing, the base of the engine was examined for fractures. Small radial fractures were detected, but not in areas that would severely compromise the integrity of the engine if refurbished with new blocks.

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V i

ENGINE ALIGNMENT l

i The alignment and trueness of engine surfaces were checked with optical t

sighting instruments. Flatness of the block surface, flatness of the exposed base, and trueness of the subbase along the ship structure were measured be-fore and after retorquing the structural bolts. The results of the retorquing 4

are discussed in quantitative terms in this section.

Structural Alignment Figures 16 to 23 (pp. V-2 to V-9) show the fore to af t elevation differ-ences for the block surfaces before removing the blocks from the engine.

These 1

measurements were taken on both engines in their pre-renovation condition with all tie bolts at their previous preload values. Before measuring, the base bolts were not checked nor were the block bolta changed from the values shown af ter retorquing when the broken block bolt was replaced (as described in Sec.

tion I).

The top a*d bottee f each block surface were recorded to verify the relative accuracy and to examind for surface twisting.

i Port Engine, Right 34 Q 4

Figures 16 and 17 (pp. V-2 and V-3) shv a sag in the middle of the engine l

from front to rear of.030 inch. Cylinder 4 shows a slight warping where the i

exhaust or top of the block is.S20 inch haut. the bottom side. All otrer cylinders follow a uniform trend. Warping ve.. a concern in setting up equip-4 ment to refinish the bore and countelbore sr inces.

Port Engine, Lef t Bank The elevations are shown in Figures 18 ar.d 19 (pp. V.4 and V-5).

The l

surface elevation shows the block surface was bowed upward and twisted in the l

center. Cylinder 4 rose.108 inch and twisted.018 inch downward in the center.

Cylinder 5 showed values nearly identical to those of cylinder 4.

Cylinders on either side of the center taper to a uniform elevation at each end. All curves 7----

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Elevation of the Air Side of the Cylinder Bloca for the Left Bank, Starboard Main Engine

V-10 return to zero at the ends because the measurements were taken using the ends as reference points. This bowing upward was a concern in the rebuilding.

Up-ward bowing was removed in the preliminary alignment procedure and it must be r % red for future maintenance procedures.

Starboard Engine, Right Bank Figures 20 and 21 (pp. V-6 and V-7) show a sag in the center of the engine and a slight twist with the block dropping on the exhaust side.

Starboard Engine, t.ef t Bank The lef t bank drops in the center and ' ' similar to the right bank for the rear half of the engine. See Figures 22 and 23 (pp. V-8 and V-9).

The front half of the engine is significantly different from the front half of the right bank.

It warped severely where the surface had some s-twists.

Severe delamination of the counterbore lip occurred in this region. The com-l l

bination of metal failure, loosened tie rods, and warped surfaces may be interrelated.

Port Engine, Base Optical sighting of the base of the port engine produced the data in 3

i Figure 24 (p. V-11).

It shows the elevation of the engine from front to rear i

for the right and lef t sides of the engine. The front half of the engine was flat with some variation, but nothing over.010 inch. The rear of the engine showed a dramatic difference between the right and lef t sides.

The left side returns to its zero point in a gradual fashion while the right side continues to drop to nearly.030 inch between cylinders 7 and 8.

The dropping of the l

base explains variations in crankshaft deflection data.

Crankshaft Deflection Measurements taken on crankshaf t deflection show the degree to which the crankshaf t is subject to bending during rotation as a result of misalignment

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Figures 25, 26 and 27 (pp. V-13, V-14, and V-15) show an effect of misalignment of the engine and indicate where problems may arise.

Figure 25 shows historical dats when the engine was hot and Figure 2 6 during rebuilding when the engine was cold. Deflection tolerance of.003 inch is allowed. The forward end of the engine, although changing sign

(+ or -), is within acceptable limits. The aft end of the engine, however, is outside acceptable limits in both hot and cold conditions. Figure 27 shows the comparison between hot and cold. The front end of the engine is within acceptable limits. At the rear, both readings are similar and thermal changes do not alter the out-of-tolerance readinga. Cold readings at the rear of the engine accurately represent hot reading for operating conditions.

Comparison between crankshaf t deflection data (Figures 25, 26 and 27 and subbase elevation data (Figure 24) indicdtes the rear of the engine is i

out of alignment. The engines should be aligned before putting them back in service.

Retorquinq The preliminary report (Appendix) recommended properly retorquing the block bolts of the engines during rebuilding. While the engines were access-ible, the base bolts were checked for proper torque and were found to be be-Iow acceptable limits. A13 structural bolts in the port engine were relaxed.

i and retorqued according to the procedure recommended by the Enterprise Com-l pany. Retorquing was done in a proper criss-cross pattern from the center outward in three graduated steps of increasing torque.

The surfaces of the blocks were checked agrin.

Figure 28 (p. V-16) shows the optical sighting of the port main engine l

blocks after relaxing and properly retorquing all the base and block bolts.

l Both block surfaces have a maximum of.010 inch of deflection and the pre-vious bowing, sagging and warping had been removed.

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Figure 27. Change in Crank Deflection for the Port Main F,ngine, l

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Figure 28.

Elevation of Cylinder Blocks for Port Main Engine Af ter Relaming and Retorquing All structural Bolts l

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i v-17 A major portton of the misalignment was due to inaccurate prestress within the engines resulting from a relaxation of torque in the nuts and an improper retorquing procedure during repair operations. The critical effect of proper gn-"

torque on all structural bolts mandates that proper torque be maintained in i

the future.

10 9

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VI i

CONCI,USIONS Observations of the condition of the M/VColumbia engines during rebuilding through March, 1981 led to the following conclusions:

Blocks.

Dimensional change in the blocks has occurred as a result of 4

creep. Replacement of the blocks with new units will result in the same problem and they will have to be replaced in three to ten years.

l1 Failure of the blocks is due to several conditions:

1) creep and fatigue which cause fractures; 2) excessive overload of the counterbore lip; 3) close proximity of cooling water holes which produces stress; and 4) close proximity of head retaining studs and thread termination for the studs at c cunterbore depth which produces a high stress concentration area.

R Gerquing. Moment from piston side thrust caused fretting between the block and base.

Improperly torqued tie roads for the blocks produced a poten-tially catastr:phic situation, and improperly torqued structural bolts thrpugh-out the engine produced severe dir.ansional changes.e l2, Alignment. The engines are misaligned in their current condition. __

v)

Heads. The heads are manufactured with castings having excessive flaws.

They appear to be adequately repaired during manufacture, but these flaws could be the cause of spurious failures.

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VII RECOMMENCATIONS REBUILDING Blocks:

Replace the blocks for both engines.

Retorquino:

Properly retorque all structural bolts.

Alignment: Realign both engines.

KEEPING OPERATIONS DATA Counterbore Lip: Survey the counterbore lip during major overhaul and when head and/or seal failures occur.

Engines: Obtain detailed operating data in the reassembled engines.

Heads:

Keep accurate historical data on head failures.

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1 VIII APPENDIX D EARY ENG ME REBUIM REPCRT O

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