DEC_Report_1518.105 _MTW_Dock_Trial_Loads_July_1 _2015.pdf

Diehl Engineering Company, PO Box 1573, Kingston, WA 98346 Phone: 360-297-8781 Fax: 360-297-8784 email: ediehl@diehlengineering.com

DIEHL ENGINEERING COMPANY

CONDITION FOUND REPORT 1518.105

VESSEL: USS MOUNT WHITNEY DEC REPORT NO: 1518.105

LOCATION: Victor Lenac Shipyard, Rijeka, Croatia

WORK ITEM: N/A

WORK DATE: 1 July, 2015 REFERENCES:

1. Lenac Contract 2015/513

2. GE LCC Main Reduction Technical Manual, Section 2-3-1

3. Waukesha Lineshaft Bearing Drawing for 20.75

Inch Dia. Shaft

4. DEC Report 1529.104

REPORT DATE: 8 July 2015

OWNER: US NAVY

CUSTOMER: Viktor Lenac Shipyard

CONTACT: Mr. Zoran Kosik TASK: Report on Measured Main Propulsion Shaft Bearing Loads After Completion of Dock Trial DEC REP: Eric Diehl

A. SUMMARY

1. DEC recommends the current alignment be considered acceptable.

2. DEC recommends that hot operating strain measurements be performed prior to the next drydocking.

B. BACKGROUND

1. DEC reported on completed alignment adjustments to the vessels main propulsion shaft bearing system in Reference 4.

2. DEC collected additional strain gage data upon completion of the dock trial.

3. The following will serve as a report on the results of the post-dock trial strain gage data.

C BEARING ADJUSTMENTS & STRAIN GAGE TESTING

1. Strain gage data was measured from the inboard strain gage locations while the vessel was pierside upon completion of dock trial on July 1, 2015 while the shaft was rotating in turning gear mode in the ahead direction.

2. The following conditions were observed when the post-dock trial strain data was collected:

- Fwd Gear Brg. Temperature: 96 deg. F.

- Aft Gear Bearing Temperature: 98 deg. F

- Forward Draft: 23 ft. 3 in.

- Mid Draft: 23 ft. 7 in.

- Aft Draft: 23 ft. 11 in.

3. DEC utilized our previously constructed in-water digital shafting model to convert the measured strains into bearing loads. See Table 1 for a summary of the measurements.

4. Projected hot operating bearing loads were calculated and are included in Table 1.

DIEHL ENGINEERING COMPANY

CONDITION FOUND REPORT 1518.105

Vert Horiz Vert Horiz Vert Horiz Vert Horiz Vert Horiz

Fwd Gear Brg lbs 78,000 28,179 3,905 24,500 -592 34,162 4,321 31,356 3,696 26,627 4,009 (150psi) psi 150.0 54.2 7.5 47.1 -1.1 65.7 8.3 60.3 7.1 51.2 7.7

Aft Gear Brg lbs 78,000 28,884 -5,320 34,145 1,048 21,662 -5,197 24,998 -4,934 32,014 -5,066 (150psi) psi 150.0 55.5 -10.2 65.7 2.0 41.7 -10.0 48.1 -9.5 61.6 -9.7 LSB 1 lbs 23,745 28,945 2,916 26,339 -101 31,968 3,186 31,454 2,600 27,597 2,893 (45 psi) psi 45.0 54.9 5.5 49.9 -0.2 60.6 6.0 59.6 4.9 52.3 5.5 LSB 2 lbs 23,745 22,930 203 24,130 1,546 22,216 46 21,901 397 23,890 2,222 (45 psi) psi 45.0 43.5 0.4 45.7 2.9 42.1 0.1 41.5 0.8 45.3 4.2 LSB 3 lbs 23,745 21,167 1,404 20,927 1,136 21,140 690 21,194 828 20,901 759 (45 psi) psi 45.0 40.1 2.7 39.7 2.2 40.1 1.3 40.2 1.6 39.6 1.4 LSB 4 lbs 23,745 22,860 -4,225 22,938 -4,138 22,380 -2,051 22,677 -3,219 22,647 -2,635 (45 psi) psi 45.0 43.3 -8.0 43.5 -7.8 42.4 -3.9 43.0 -6.1 42.9 -5.0 Total lbs n/a 153,008 -1,117 153,025 -1,098 153,570 995 153,622 -631 153,721 2,186

Gr Brg Load Diff lbs n/a -705 9,225 -9,645 -1,640 12,500 9,518 6,358 8,630 -5,387 9,075 -1.2% 16.2% -16.4% -2.8% 22.4% 17.1% 11.3% 15.3% -9.2% 15.5%

Notes:

2) Positive horizontal bearing load means the shaft pushes to port on the bearing.

Max Loads From

Builder

Bearing Location & (allowable psi)

% GBLD of Vert Sum

Current Cold Alignment, Measured June 30, 2015

1) Positive vertical bearing load means the shaft pushes down on the bearing.

After Dock Trials, July 1, 2015, Semi-Hot Condition

As-Measured, Ahead Direction

Projected Hot Operating

Table 1: USS MOUNT WHITNEY Measured Main Propulsion Shaft Bearing Loads, June 2015, Before & After Bearing Adjuistment

Ahead Direction Average, Projected Hot

Operating Astern Direction

D. DISCUSSION

1. Reference 2 includes a projected gear bearing vertical offsets of 0.009 – 0.011 inches from 80 F to the hot condition. Reference 2 does not state what temperature is considered hot operating condition. The thermal growth correlates to a temperature difference of about 40 degrees F for the reduction gear foundation eight (36 inches) and the coefficient of thermal expansion for steel.

2. The post-dock trial data had a temperature difference from cold of about 16 – 18 degrees F., and should therefore be considered a semi-hot condition.

3. From Reference 2, both the vertical and horizontal gear bearing load difference (GBLD) should be less than 10,000 pounds. This correlates to about 17% of the sum of the gear bearing loads. DEC normally considers the maximum allowable GBLD to be 25% of the sum.

4. The lineshaft bearings are disc lubricated, non-self-aligning Babbitt bearings. From Reference 4, the vertical load should be less than 23,740 pounds, which is equivalent to a projected unit load of 45 psi.

In Reference 4 DEC recommended that a unit load limit of 55 psi (29,000 pounds f) to be considered acceptable.

5. The projected hot operating bearing loads (based on a 40 degree delta temperature) from the post-dock trial (semi-hot) data and as-aligned cold data are both within the 10,000 pound difference criteria and are acceptable.

DIEHL ENGINEERING COMPANY

CONDITION FOUND REPORT 1518.105

6. The projected post-dock trial hot operating lineshaft bearing load on LSB1 is 49.9 psi, and is within DEC’s recommended 55 psi limit from Reference 4.

7. The post dock-trial projected hot bearing loads on LSB 2, 3 & 4 are below the 45 psi limit from Reference 3. See Table 1.

8. DEC therefore recommends the current alignment be considered acceptable.

9. The projected hot operating bearing loads are different from the post-dock trial data and as-aligned cold data. See Table 1. The difference in projected hot operating bearing loads from the cold and semi-hot conditions may indicate that actual thermal growth is greater than the Reference 3 amount. This should be verified by performing strain measurements in the full hot condition, which requires coming to full stop at sea after completion of a full power, engaging the turning gear, and immediately measuring strains.

10. The vessel will undergo an additional drydocking and hull repairs in about 18 months that will require additional realignment. DEC recommends that hot operating measurements be performed at some point prior to the next drydocking to determine if revised thermal growth calculations are advised for the future alignment efforts.