SHIP SYSTEMS ISE ADVISORY NO. 059-82
LPD-1 CLASS STERN GATE EMERGENCY RIGGING
NAVSSES PHILADELPHIA PA MSG 212142Z MAY 82
REF: A. SHIPALT LPD-405, REV 1, STERN GATE EMERGENCY RIGGING
B. NAVSEA DWG LPD 2-122-5500985, STERN GATE EMERGENCY RIG-
GING MODIFICATION
C. NAVSHIPYD PHILADELPHIA PA 061344Z MAY 82 (NOTAL)
1. SUMMARY: THE PURPOSE OF THIS MESSAGE IS TO ADVISE THAT THE
EMERGENCY STERN GATE RIGGING ARRANGEMENT CURRENTLY INSTALLED ON
USS RALEIGH (LPD-1) AND USS VANCOUVER (LPD-2), PER SHIPALT LPD-405, IS
SUBJECT TO POSSIBLE FAILURE DUE TO A MARGINAL FACTOR OF SAFETY
ASSOCIATED WITH ONE OF THE SHEAVES USED ON THE STARBOARD SIDE. A
RECOMMENDED MODIFICATION IS PROVIDED. END SUMMARY.
2. REFERENCE A WAS ISSUED TO MODIFY THE EXISTING LPD CLASS STERN
GATE EMERGENCY RIGGING. REFERENCE B WAS DEVELOPED BY SUPSHIP SAN
DIEGO AND WAS USED FOR THE INSTALLATION OF REFERENCE A ON USS
VANCOUVER (LPD-2). ALSO, NAVSHIPYD PHILADELPHIA PA RECENTLY USED
REFERENCE B FOR ACCOMPLISHING REFERENCE A ON THE USS RALEIGH (LPD-
1).
3. REFERENCE C NOTED A PROBLEM WITH ACCOMPLISHING THE SHIPALT
PER REFERENCE B. ONE OF THE EXISTING SHEAVE BRACKETS IS SUBJECTED TO
SUBSTANTIALLY MORE TORSIONAL LOADING WITH THE NEW RIGGING AR-
RANGEMENT SHOWN IN VIEW EL 17-C OF REFERENCE B. REFERENCE C
FURTHER NOTED THAT NAVSHIPYD PHILADELPHIA WAS DEVELOPING A MOD-
IFICATION TO REFERENCE B WHICH WOULD BE ACCOMPLISHED ON USS
LASALLE (AGF-3), CURRENTLY UNDERGOING ROH AT NAVSHIPYD
PHILADELPHIA THE MOD BEING DEVELOPED BY NAVSHIPYD PHILADELPHIA IS
TO STRENGTHEN THE SHEAVE BRACKET SUBSTANTIALLY SO THAT IT WILL BE
ABLE TO HANDLE THE LOADING SAFELY.
4. NAVSSES DISCUSSED THE ABOVE PROBLEM WITH SUPSHIP SAN DIEGO
DESIGN PERSONNEL AND IT WAS AGREED THAT THE BEST SOLUTION WOULD BE
TO CHANGE THE STARBOARD RIGGING ARRANGEMENT SO THAT IT IS SIMILAR
TO THE PORT ARRANGEMENT (SEE DETAIL 8-C ON REFERENCE B). NOTE, THE
PORT ARRANGEMENT UTILIZES A SNATCH BLOCK VS A FIXED SHEAVE AND IS
NOT SUBJECT TO THE TORSIONAL LOADING. THIS ALTERNATIVE FIX WAS
DISCUSSED WITH NAVSHIPYD PHILADELPHIA DESIGN PERSONNEL AND THEY
CONCUR WITH IT.
5. BASED ON THE ABOVE, NAVSSES RECOMMENDS THE FOLLOWING:
A. AT THE FIRST OPPORTUNITY MODIFY THE STARBOARD SIDE EMER-
GENCY STERN GATE RIGGING ON USS RALEIGH AND USS VANCOUVER SO THAT
IT IS THE SAME AS THAT ON THE PORT SIDE (DETAIL 8-C OF REFERENCE B).
B. ACCOMPLISH THIS SAME MOD ON USS LASALLE WHILE IT IS STILL IN
ROH.
C. UNTIL THIS MOD IS ACCOMPLISHED, EXTREME CARE SHOULD BE
USED IF THE EMERGENCY STERN GATE RIGGING MUST BE UTILIZED: NO
EXTERNAL LOADS (OTHER THAN THE GATE WEIGHT) SHOULD BE IMPOSED ON
THE RIGGING.
D. UPON ACCOMPLISHMENT OF THIS MOD, THE EMERGENCY RIGGING
SHOULD BE TESTED. TESTING IS TO INCLUDE A 200 PERCENT STATIC LOAD TEST
(THE GATE HORIZONTAL AND AN EXTERNAL LOAD OF APPROXIMATELY 80-90K
POUNDS PLACED ON THE GATE) AND A 150 PERCENT DYNAMIC LOAD TEST (THE
GATE HORIZONTAL AND AN EXTERNAL LOAD OF APPROXIMATELY 40-45K).
DURING BOTH TESTS THE HYDRAULIC SYSTEM DOCKING VALVE MUST BE
OPENED AND DURING THE DYNAMIC TEST APPROXIMATELY 2 FEET OF GATE
TRAVEL IN EACH DIRECTION IS REQUIRED TO VERIFY OPERATION.
6. FOR NAVSEA 5142/9413: RECOMMEND APPROPRIATE ACTION BE TAKEN TO
MODIFY REFERENCE B TO DOCUMENT THE ABOVE MODIFICATION.
REFERENCES A AND B SHOULD ALSO BE REVISED TO INCLUDE THE TESTING
REQUIREMENTS CITED IN PARAGRAPH 5.D ABOVE.
THIS ADVISORY APPLICABLE TO LPD-1 AND AGF-3 CLASSES OF SHIPS.
LPD-1