Lifelines are what stops someone going over the side. They're also the gear least looked at until someone falls against it. Don Casey, writing in SAIL, says that when a lifeline fails, the cause is usually corrosion.
What fails
Coated wire. Plastic-coated lifelines look tidy, but Casey says the coating can hide corrosion. Practical Sailor stripped the cover from one showing red rust stains and found more rust and broken strands in the middle sections. Both recommend bare 1x19 stainless wire.
Terminals. Practical Sailor says threaded terminals are weak points that often bend or break first, and that Type 304 swaged fittings, common on lifelines, corrode faster than 316.
Stanchion bases. Casey's number: 200 pounds pushed against the top of a 30-inch stanchion can put as much as 3 tons of pull on its base. Bases need oversized metal backing plates, and shoulder washers alone aren't enough. Bases that leak also feed water into a cored deck.
Gates and sheaves. Casey says gate hardware is susceptible to failure. Practical Sailor notes white plastic sheaves succumb to UV sooner than glass-reinforced ones.
How a surveyor checks it
Run a hand along each lifeline, feeling for broken strands, and look for rust stains in any coating. Check the tension: Casey says lifelines must never become slack. Look at each terminal for bent studs and cracks. Push and pull each stanchion: it shouldn't move. Inside, find the bases and look for backing plates, weeping and soft core.
What decides the grade
Whether it would hold someone. A broken strand, slack lifeline, bent stanchion or loose base is an A. Rust bleeding through a coating, or bases without backing plates, is a B. Stiff gates and tired sheaves are a C.