PSI - Issue 14

V Kiran Govind et al. / Procedia Structural Integrity 14 (2019) 435–441 Author name / Structural Integrity Procedia 00 (2018) 000–000

441

7

7. Development of new HC The design and development of a new Heavy Cable, based on above results, has been a challenging task. Some of the major technical challenges faced along with implemented innovative solutions which helped to overcome these challenges are provided in Table 7.

Table 7. Technical challenges and solutions

Sl No: Parameter

Technical Challenge Failure of optical lines during deployment retrieval cycle Water seepage in radial direction once outer sheath is broken Lose of concentricity and sheath failure

Implemented Solution

1

Optical lines

a) Replaced thermoplastic tube with Steel tube b) Reduced no: of tubes from 6 (each with 2 FO lines) to 4(each with 3 FO lines)

3

a) Introduced silicon rubber compound filling

Interstitial space inside core cable Outer Sheath

4

a) Changed sheath material from PU to HDPE b) Ensured 2.0 mm uniform thickness of outer sheath through cable length a) Diameter of inner armour wires increased from 2.0mm to 2.4 mm b) Diameter of outer armour wires increased from 1.6 mm to 2.0 mm c) Armor material changed from SS-316 to Extra improved Plow Steel (EIPS) a) Increased armour lay angle from 14.4 degree to 19.8 degree. b) Reduced armour lay length from 306 mm to 225 mm

5

Flattening of armour wires

Metallic Armour

6

Cable configuration

Lose of circular configuration under

extreme loading during deployment and retrieval

A new Heavy Cable was developed incorporating all the above design solutions. A sample of the new HC was subjected to cyclic testing as per Test No: 1 and Test No: 3. On analysis of the measured values, it was found that the endurance and performance of the cable is matching with that of the imported cable. The new HC has been inducted to the system and has underwent several successful sea-trials by now. Acknowledgements The authors would like to express their sincere gratitude to Group Director and members of Engineering Group, NPOL for their valuable inputs, support and guidance for cyclic testing of Heavy Cable. The authors also express their gratitude to M/s Apar Industries, Mumbai for facilitating the experiments at their factory premises. References Chapman, D.A., 1984. Towed cable behaviour during ship turning maneuvers. Ocean Engineering 11 (4) 327–361. Dowling, A.P., 1988. The dynamics of towed flexible cylinders. Part 1.Neutrally buoyant elements. J Fluid Mech 187,507–532. Bowers, W., 1973, High Strength-to-Weight Cable for Deep Ocean Projects, 22nd International Wire & Cable Symposium, 279 -285. Triantafyllou. M. S., 1991, Dynamics of cables, towing cables, and mooring systems, Shock and Vibration Dig., vol. 23,3 -8.