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Old 18-04-2006, 08:55   #1
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Location: Kemah, Texas
Boat: Slocum 37 Cutter "Little Dipper"
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Question Anchor Rode WLL or SWL Ratings

Is there an industry standard for rating the safe working loads or working load limits of rope and/or line? In researching this, have found ranges quoted from 8 to 15 percent, and, nothing specifying if that is a percentage of average tensile or breaking strength.

Very confusing... as bad if not worse than trying to decipher the various different percentage ratings of chain and shackles. I also discovered the rope industry might be moving to using breaking strength as the measure to help eliminate the widespread confusion. I emailed Samson Ropes Technical dept (my rope supplier) with the same question as above... no reply.

Anyone have the latest lowdown?
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Old 18-04-2006, 12:51   #2
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Rope SWL's depend on what it is being used for. If you're climbing on it for example the SWL is 10% of break load. Generally for use in a anchoring situation use 15-20% of break. Differing manufacturers use differing numbers but the above is a general rule.

Chains - Industry standard is 4:1 margin or 25% of break. This exludes US chains above a G30 or BBB. The HT 'seems' to be a 2.5:1 margin, know on will tell us but that number stackes with the Grades break loads.

Shackles - the 'rated' Green Pin type run at 6:1. The bog standard everyday ones are not rated in any way and have lowish loads so I'd use 4:1 maximum but prefer more i.e. 6:1 as well.

As a rule the SWL's are pretty standard worldwide, US excepted who do some strange ones.
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Old 18-04-2006, 13:51   #3
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Thanks for that Gmac. Appreciate your expertise regarding chains, shackles and line. Very confusing, especially when you attempt to make an online purchase. Many will advertise their shackles meet a certain govt standard but do not elaborate with ANY details.

After much frustration and misguided information, I did some digging and discovered the US federal govts "mil spec" standards for chain and shackles. Here is a link to that page.

It appears, at least according to the above link, glavanized ALLOY shackles or Grade B as reffered to by the US govt, offer a higher tensile strength than what they term as Grade A and would be more compatible with the WLLs of G4x chain.

Digging a little more, I found US manufactured Crosby shackles to be one of the most commonly available glavanized alloy shackles though in limited sizes. They're not stocked by many marine dealers but are readily available from outfits that support the towing, logging, shipping, heavy lifting and rescue equipment industries. The color of the pin does not seem to specifically identify any particular rating or strength... only that it MIGHT be rated... to what, who knows or by whom.

As an example, below is a link to a 4 wheel drive house that
lists what they describe as G40 shackles with a red pin showing a 1/2" with a WLL of 6000lbs. Little other data available other than a photo. Other red pin 1/2" shackles I found were only be rated at 4000 lbs WLL. Also noted that some highly rated alloy shackles have only galvanized pins.

Onward through the fog.
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anchor, rode

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