UNDERWAY REPLENISHMENT NWP 4-01.4 - Historic Naval Ships ...

NWP 4-01.4introducing a weak link into the system for wincheswithout a slip clutch (see paragraph 2.6.6).2.6.2 Safety Factor. Rig fittings are normally designedwith an adequate factor of safety (about 2.25)based on the ultimate strength to prevent any deformationwhen the test loads are applied.2.6.3 Fitting Strength. Because of the nature of thematerial used, the fitting and supporting structure shouldnot carry away, unless a load of double the test value isapplied to them. Since twisting of cables, fatigue, corrosion,and welding can reduce the strength of fittings, the“test load” on the label plate must be adhered to rigidly.2.6.4 Static Load Test. The static load test shallsimulate actual operating conditions and shall be performedat the angle within the working range that willproduce maximum stress.2.6.5 Booms. If stress analysis indicates that anyboom or its related gear specified for RAS or FAS operationwill be more highly stressed when breaking thespan wire or the Burton whip, than when withstandingthe static load test for the boom, the boom or that portionof its gear shall be given a special test to demonstrateits ability to withstand stresses at least equal tothose indicated by the stress analysis.2.6.6 Ship’s Structure Protective Devices. Shipboarddamage caused by tightlining of wire ropes isprevented by weak links or winch drum slip clutches.2.6.6.1 Weak Link. A weak link is a fitting designedto fail at a predetermined load. It is introduced(1) between the receiving station’s supporting structureand the rig or (2) within the transfer rig. A weak linkcarries away completely at a load level low enough toprevent deformation of the supporting structure ordamage to the rig. Weak links are not required wherewinch drums have built-in slip clutches.WARNINGWeak links give no absolute assurance thatthey will fail at the anticipated level. This isbecause of condition, design, torsion ortwist loads, and dynamic surges.2.6.6.2 Slip Clutch. A slip clutch is a device builtinto a wire rope winch drum designed to slip at a presetload. When the load on the wire rope exceeds this presetload, the clutch allows the drum to rotate and thewire rope begins to strip off the drum. This continuesuntil (1) the wire rope load is decreased below the presetload and the clutch resets or (2) the bitter end of thewire rope comes off the drum.2.6.6.3 Guidance. When the static-tested load forthe attachment point, as shown on the latest weighttest memo, is less than the breaking strength of thetransfer rig to be used, a weak link or slip clutchmust be employed.WARNINGPersonnel Transfer Rig Exceptions: Weaklinks will not be used with any wire rope orsynthetic line, except when needed to attachthe hand-tended outhaul to a trolley inSTREAM mode (see Chapter 8). Onlyinhaul winches outfitted with a slip clutchshall be used for STREAM personneltransfer (see Chapter 8).2.6.6.4 Types of FAS Weak Link1. 7/8-inch (22.2 mm) spanwire weak-link end fittingwith a breaking strength of 35,000 lb(15,875 kg) — NAVSHIPS Dwg 803-22528562. 3/4-inch (19.0 mm) spanwire weak-link end fittingwith a breaking strength of 30,000 lb(13,608 kg) — NAVSHIPS Dwg 803-2252855.2.6.6.5 Types of RAS Weak Link1. 8,000-lb (3,628 kg) weak link — NAVSHIPSDwg 805-17491062. 13,000 to 15,000-lb (5,897 to 6,804 kg),STREAM system lightweight trolley, 1/2-inch(12.7 mm) inhaul/outhaul weak-link end fitting— NSN 2S 1450-01-067-56013. 13,000 to 15,000-lb (5,897 to 6,804 kg),STREAM system lightweight trolley, 3/4-inch(19.0 mm) inhaul/outhaul weak-link end fitting— NSN 2S 1450-01-067-56024. 25,000-lb (11,227 kg) pendant receiving stationweak link for stations tested to 25,000 lb (11,227kg) — NAVSHIPS Dwg 528-44049745. 50,000-lb (22,675 kg) STAR rig (highlineSTAR probe) shear pin — NAVSHIPS Dwg805-4629266.2-35 ORIGINAL