PSI - Issue 14

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

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Table 1. Technical Specifications of Heavy Cable Sl No Features Specifications 1 Overall diameter

Within array diameter of ~ 32 mm, Max. deployable length 500m

Length

2 3 4 5 6 7 8 9

Stowage condition

To be stowed in a winch drum of diameter 1m

Weight in air

~ 3.5 kg/m

Weight in seawater

Negatively buoyant

Connectivity

Sufficient no: of electrical/fibre optic lines

Breaking strength Water blocking

More than 150 kN

Water-blocking in Radial direction up to 50 bar pressure.

Min.Bending diameter

900 mmm

Armouring

Two layers of contra-helical, torsionally balanced metallic armour

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3. Observations from Sea-trials In a series of sea-trials of towed array sonar system, the structural integrity of Heavy Cable was found to be affected in following ways:- a) Flattening of circular cross-section at several locations over the deployed length b) Loosening and protrusion of armor wires and c) Failure of electrical and fiber optic lines On closer observation, it was noticed that the cable underwent severe bending at following regions during deployment and retrieval cycle:- a) 24 0 Angle of Approach over 65 mm diameter roller on winch spooler This condition happens when the spooler is at the extreme ends of the winch while deployment or retrieval. The spooler roller diameter is 65 mm and the cable bends at 24 0 as it comes/goes to the intermediate fairlead. This is shown in fig 2 a). b) Bending of cable at 90 0 angle at main fairlead This condition happens at the main fairlead during the deployment/retrieval of Towed Body (TB).During deployment, the entire weight of TTB i is hung on HC over 290 mm diameter rollers set at main fairlead along with an additional drag force generated by LC and array modules which are already in water. This is shown in fig 2 b) and c).

(a)

(b) (c) Fig. 2. Bending of HC at different locations during deployment and retrieval

In view of the above, it was planned to carry out detailed cyclic testing of sample cable simulating both the above conditions independently to verify the cause and study the effects of such flattening on functionality and life of the