centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 NDT tests and laboratory examinations on samples taken from the fractured starboard side foundation structure of a container vessel steering gear C. Dellabiancia, M. Dellabiancia, P. Del Chiaro, L. Rolla, V De Luise, S. Rinoldi, C.T.S. Centro Tecnologico Sperimentale S.r.l. Ceparana (SP) ctssp@ctssp.com - ctssp.dir@ctssp.com – www.ctssp.com 1
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Marine steering gear system generalities Case of study Background Required inspection and laboratory analysis Main outcomes Results and observations Conclusion 2
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Marine steering gear system generalities The main control of the steering operations is given from the helm of any ship, similar to an automobile where the entire control of the vehicle’s “steer - ability” rests on the steering wheel of the driver. The ‘control force’ for turning is triggered off from the wheel at the helm, which reaches the steering gear system. The steering gear system generates a torsional force at a certain scale which is then transmitted to the rudder stock that turns the rudder. 3
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study - Background The case of study is related to a VESSEL CONTAINER CARGO built in 2003 having overall length of approximately 212m by roughly 30 wide weighing circa 34.000 t. 4
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study - Background The vessel had been drydocked in La Spezia for normal refitting and repairing operations on board and for the replacing of rudder’s shaft bushings and couplings. Soon after the end of the operations on board the steering gear has been tested to verify proper functioning before flooding the drydock. During this test a loud noise was heard coming from the steering gear room. Inspecting the main maneuvering room technical personnel documented a severe damage on the STBD’s thrust side foundation of the maneuvering cylinders, which was partly ripped off from the aft peak sewage tank top. 5
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study - Background The vessel had been drydocked in La Spezia for normal refitting and repairing operations on board and for the replacing of rudder’s shaft bushings The on board personnel declared that at the moment of the steering and couplings. gear testing none of the safety devices for the pressurized Soon after the end of the operations on board the steering gear has been tested to verify proper maneuvering system , such as safety valves on hydraulic cylinders and functioning before flooding the drydock. During pressure gauge on pump outlet, was activated this test a loud noise was heard coming from the steering gear room. Inspecting the main maneuvering room technical personnel documented a severe damage on the STBD’s thrust side foundation of the maneuvering cylinders, which was partly ripped off from the aft peak sewage tank top. 6
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study - Background 7
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study – STBD’s Thrust side foundation 8
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study - STBD’s Thrust side foundation During the first examination, performed directly on board, it was found evident the shiny appearance of the fracture surface; normally this morphological aspect is associated with poor toughness properties of the material 9
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study – Required inspection – NDT – MPI Nondestructive testing was required to verify the integrity of welded joints between PORT THRUST side foundation and AFT PEAK TANK TOP No evidence of macroscopic indication to be recorded was found with a superficial check performed by magnetoscopic examination, only marginally detected undercutting next to the beam’s toe. 10
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study – Required inspection – NDT – UT Volumetric nondestructive examination was required to verify the soundness of welded joints between PORT SIDE THRUST foundation and AFT PEAK TANK TOP The absence of fully penetration was observed by ultrasonic examination 11
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study – Laboratory analysis Soon after the NDT investigation on board it was decided for sampling part of the STBD foundation side to perform specific laboratory analysis with the main objective of verifying both chemical and mechanical characteristics of the material as well as the microstructure of the base material plate 12
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study – Sampling position M1 - M2 = macrographic examination of welded structure Tr1 - Tr2 = tensile specimens KV1 - KV2 = impact test specimens MICRO = micrographic examination 13
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study – Tensile test results Obtained values were within the prescribed limits for a normal strength steel Grade A – According to IACS Rules Reduction Tensile strength Yield point Elongation Area POSITION Rm Rp0,2% A5 Z (MPa) (MPa) (%) (%) TR1 412 248 35,8 65,7 TR2 412 247 37,2 67,3 REFERENCE VALUES 400 ÷ 520 min 235 min 22 - FOR STEEL GRADE [A] 14
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study – Charpy test results Obtained values were within the prescribed limits for a normal strength steel Grade A – According to IACS Rules Energy values Energy average value POSITION (J) (J) KV1 41 - 34 - 39 38 KV2 70 - 75 - 59 68 REFERENCE VALUES 27 min average value - longitudinal direction FOR STEEL GRADE [A] 20 min average value - transverse direction 15
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study – Macrographic examination Macrographic sample M1 position and appearance Lack of penetration Ammonium persulphate 10% Macrographic sample M2 position and appearance Lack of fusion Ammonium persulphate 10%) 16
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study – Hardness test results VERTICAL PLATE WELD METAL BASE PLATE Hardness test Vickers HV 10 Point 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Line 1 182 180 178 237 285 291 218 213 219 183 188 181 157 156 157 Line 2 166 161 170 208 218 263 226 208 212 176 154 158 140 138 140 Line 3 161 160 171 246 236 273 210 203 199 155 154 148 145 143 142 17
centro Certified laboratory UNI EN ISO 9001 : 2008 tecnologico BS OHSAS 18001: 2007 sperimentale s.r.l. Accreditated laboratory UNI CEI EN ISO/IEC 17025 : 2005 Nr.1588 Case of study – Chemical analysis VERTICAL PLATE Chemical composition verification has been carried out on macrographic sample M2 in order to analyze WELD METAL both base material and the weld metal BASE PLATE No evidence of composition anomalies was noticed. C Si Mn P S Cr Ni Mo Cu V Ceq (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) BASE PLATE 0,141 0,13 0,60 0,0189 0,0089 0,30 0,12 0,005 0,03 0,001 0,31 VERTICAL PLATE 0,141 0,27 1,31 0,0139 0,0038 0,33 0,06 0,004 0,03 0.001 0,43 WELD METAL 0,049 0,48 1,13 0,0134 0,0074 0,32 0,08 0,003 0,02 0,001 - 18
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