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post #41 of Old 09-26-2012
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Re: 35 year old standing rigging - but rigger says it's ok

Originally Posted by davidpm View Post
OK I think I got it.

The first couple of paragraphs says the the most wear with wire rope in crane service is rolling over the pulleys caused damage to wire.

Usually, fatigue breaks develop in segments of the rope surface that come into direct contact with a sheave or drum.

If that is the case then bad strands will show up before any other damage is critical in a crane.
With a boat since the wire don't move it can fail first in places that can not be seen.
That is a great articles, going to take me some time to fully understand. But what about the "chokers" that are often used with a crane? These chokers do not see a rolling load (although they would see a compression load) and the chockers usally have a crimp conection that creates an eye (see my previous post). And I still don't understand why sailboats do not have a better redundancy- know as "belts and suspenders" in the structural design trade. For example just because you break one wire on your rig should not bring your whole rig down, but it will based on the normal design of a sail boat rig.

Just saw this int the article, very interesting (would this pertain to sailboat rigging?):

"Two different philosophies have been used to effect rope retirement:
1. A Statutory Life Policy mandates rope retirement at certain prescribed intervals. (This means, the Statutory Life Policy places a maximum on the time a rope can be in service).

2. Retirement for Cause is based on retirement conditions that are evaluated periodically by nondestructive inspections. (This means, the Retirement-for-Cause approach requires that the rope must be retired when the deterioration exceeds a certain limit.)
Because a Statutory Life Policy is inherently wasteful, regulators have tended to adopt the Retirement-for-Cause approach wherever appropriate."

Last edited by casey1999; 09-26-2012 at 01:25 PM.
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