C-link in anchor chain - is mine OK?

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bluedragon

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Like a number of previous posters, our boat has a C-link join in the anchor chain (at 31m, so usually it's in the locker). There are it seems good C-links and bad C-links out there, but which have we got? The link seems to be stainless steel, looks well assembled and has "5/16ths" stamped on it, but nothing else. Should I be concerned?
 
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Should I be concerned?

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Well I would be. Such a link cannot possibly be as strong as the chain it is joining, if it were it wouldn't fit through the chain.

If you search the internet you should be able to find the breaking load of the chain and the link. The difference is eye-opening.
 
Towards the end of last year I fitted one on my anchor chain (assured by the chandler that it was as safe as houses). I've spent one sleepless night at anchor, thinking about how cheap it was, how much my boat is worth to me, and the cost of the alternatives (which are either to buy a new, unbroken length of chain, or to buy a tested shackle to join the two lengths).
I removed the chain and replaced it with anchorplait for the remainder of last season, and I'm just about to buy a proper length of chain before I set off anywhere this year. I prefer to sleep at night.
If you really can't afford a new length of chain, buy a tested shackle to join the two lengths.
 
when you said "a tested shackle"....

anchorshackle.jpg



But seriously, Cosalt have lots of shackles and joining links which are properly tested.

http://www.cosalt.co.uk/fish/trawxc.html
 
I'm looking to join two lengths of chain together. Not concerned about the windlass bit as happy to lift 1 foot of chain around the windlass by hand, but do want to get a strong link.

I looked at the coloured pin tested shackles (Jimmy Green sell them) - but what about these:
http://www.absoluteindustrial.co.uk/products.php?category_id=451

They look to have a massive breaking strain - 10mm is 5,400kg - which is more than the rated shackles other people sell (Jimmy Green's 10mm is 1 ton I believe) - plus being a flush pin the windlass won't mind it as much.

What do people think - good idea?

Jonny
 
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...what about these:
http://www.absoluteindustrial.co.uk/products.php?category_id=451

....

What do people think - good idea?

[/ QUOTE ]

No, because:

1) There's no mention of the strength of these being certified in any way;
2) They quote the breaking load, which always smacks of snake-oil when used in isolation, and is different to the failure load, which is different again to the load 'rating'.
3) There is no mention of WLL (Working Load Limit) or the older term SWL (Safe Working Load) which must by law be marked on shackles intended for lifting;
4) There is no mention of the standard to which they are manufactured.

(Oh, and they are stainless (alloy unspecified) as well, which wouldn't be my choice, but...)

I'm sure that you, like me, want a link that we can be as sure as we possibly can won't break.

There are two facets to that requirement: The link must be suitably designed and physically big enough to carry the loads in the anchor chain, and it must be manufactured in a consistent manner from good quality materials.

The 'big enough' bit is relatively easy: you have an 8mm steel chain (say), you just need a steel shackle / link / etc. that has the same diameter body (and material grade if it's a HT chain).

The 'good enough' bit is nigh on impossible. The best one can do is to is to use parts destined for industrial lifting use, where the dire consequences of failure mean that rigorous standards are imposed on the equipment and its manufacture. Even then, one needs to beware of 'counterfeit' shackles, etc. made cheaply, but with all the right markings (even the alleged manufacturer's name).

IMHO, it's a lot easier to get manufacturing and design defects with stainless steel than galvanised, which is a good reason not to use it unless you have to. I've also been on the wrong end of an HSE investigation into a parted stainless steel chain used for lifting in wet areas which has made me deeply suspicious of the material in these sort of applications.

As it happens, I'm looking to join two lengths of anchor chain, too. Franky, the quality of shackles, etc. available in my local chandleries is laughable, and certainly not suited to load bearing use. The best place for their 'C' links would be inside Christmas crackers.

I'd have no qualms using a properly certified galvanised shackle, but I too would like to be able to feed the join around the windlass with the minimum of fuss, so I intend to get a certified 'C' link from the local crane servicing company.

Sorry, soapbox away now /forums/images/graemlins/smile.gif

Vyv_Cox is the man for this if he's still around.

Andy
 
Andy,

Thanks for this - I PM'd Vyv as I recalled his article in YM on this topic. If you source a good C link then let me know!

The tested shackles from Jimmy Green look good, but would definitely not be friends with the windlass!

Jonny
 
Will certainly let you know on the 'C' link - I'll see "The Man" from the crane co. in the next couple of weeks.

I'm sure I've seen certified shackles with a flush head pin, but can't find them now. Gael Force do a good selection of tested shackles, too.

Andy
 
A post back in Feb gave some recommendations for certified C links. Crosby was one of the mfrs. I might try to track them down as I'd also prefer to avoid a shackle.

Having had a good look again at my S/S C-link, it is 8mm diameter and seems well made. Even if the break load is lower than the chain, I suspect in reality it's never ever going to see the sort of loads that'll cause it to fail...but on these forums we all default to the worst case scenario. Has anyone actually had a C-link fail in service???
 
I've found the post I recalled seeing (maybe the same one as you) where Vyv Cox talks about C link strengths- there's a source for them, and some interesting info on the strength of shackles.

here

There really should be some sort of FAQ for these forums.....

Andy
 
Thanks - I notice Vyv suggested a Wichard shackle - found some they do with a flush pin - the 10mm one has a working load of 1800kg and a breaking load of 4300kg (10mm Grade 30 chain has a breaking load of 4750kg so the shackle is almost to the standard of the chain) - the Selby C Links have a very simalar WLL and breaking load of the wichard from my googling!

Jonny
 
I just looked at the Jimmy Green tested shackles - 10mm chain has a breaking point of 4570kg, the proof load on their tested 10mm shackle is only 2 tons, SWL 1 ton - much lower. The 10mm shackles from Baseline etc whilst not certified, have a breaking point of 4,800kg.

Why are the tested shackles apparently so weak, or is it that the non-tested ones are subject to some marketing spin and would actually test much lower?

Also - any views on these:

http://baselinemarine.com/shopdisplayproducts.asp?id=34&cat=Rapid+Links

Very high breaking load (9000kg) and a 1800kg SWL (for the 10mm version).

Edit - Also just found this company www.s3i.co.uk - they do tested shackles in all shapes / sizes. They give suggest SWL and breaking points on the site, but will test individual shackles too (although they want £60 set up and 90p per shackle for testing and certificate).

Jonny
 
I've just ordered one the rapid links to terminate the chain and act as a back splicing ring for 16mm 3-strand rope. This size warp is too large for 8mm chain links, but I've got it on board and will use it if I can.

Re: the Jimmy Green shackles, I wonder if there is a difference bewteen "proof testing" and "breaking point"...that might explain the values.

PS - what is a 4-5 ton load going to do to your deck gear (or deck)!! Might be better if something breaks a bit earlier (heresy I know /forums/images/graemlins/tongue.gif /forums/images/graemlins/tongue.gif)
 
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I wonder if there is a difference bewteen "proof testing" and "breaking point"...that might explain the values.

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Ooooh yeeees....

Breaking load or ultimate failure load is the load at which the thing in question pulls to pieces.

Failure load *can* be confused with the above, but, correctly used, is the load at which the thing in question is permanently damaged - for example a chain link becomes elongated, or a shackle pin bends.

Working load limit (WLL) / Safe working load (SWL) / "load rating" is the maximum load which it is safe to apply to the thing in question. It is usually arrived at by dividing the failure load by a Safety Factor enshrined in some DIN/ISO/ASTM standard. WLL is the 'new', EU harmonised name for SWL. 'Load rating' is plain sloppy terminology.

Proof load is the load that is applied to the thing in question during manufacture to check that it doesn't break. It is higher than the WLL, but (by definition) it must be lower than the failure load. If everything else about the thing in question rings true, this is a useful indicator that there are no latent defects present which could develop (through corrosion or fatigue, for example) into a failure at a later date. This is most important with high strength alloys which are more prone to fatigue than low carbon steel.

For example:
Maximum Proof Load is 2.2 times the Working Load Limit. Minimum Ultimate Strength is 6 times the Working Load Limit from the Crosby site.

OK, I've had another glass of wine, but I'm still not sure how to write this next bit, but I'm braver, so here goes:

I looked at the 'coloured pin' shackles on the Jimmy Green site, and frankly they look like cr4p. When I read about them being proof tested, I want to cry! they probably are 'proof tested' in as much as every one is loaded up as it leaves the production line: those that don't break get a certificate, those that do break are probably melted down for another try.

If we talk about shackles specifically, the aim is to achieve the same strength in a complex, two part component as in a simple chain link. To do so requires careful control of the grain size of the metal; the grain flow of the metal during forging; the shape of the part; the surface finish, the heat treatment, the plating process, etc, etc, on top of starting with a good quality piece of the correct material. The 'coloured pin' shackle simply doesn't demonstrate the degree of precision necessary to achieve this - the metal forming is shoddy - the hole for the pin is too big, the transition from the eye to the loop is too abrupt, the shape is different on one side to the other, the thing isn't even straight!; the markings are shoddy, the plating looks shoddy (it looks like "make me shiny" BZP, not the full thickness of galvanising) - it smacks of cheap tat dressed up to mislead the partially informed and well intentioned: "...proof tested...", "...coloured pin...".

96ShackleColouredPin_comp.JPG


contrast this with a good quality shackle:

58g1.jpg


The surface is smooth; the shape is symmetrical; the transitions are smooth and gradal; the markings are crisp and raised, not stamped in; the pin fits the hole; it looks like it's galvanised... I could go on...

A properly made shackle should be a sculpture in miniature, and a pleasure to look at and handle.

I don't intend to cast any slight on Jimmy Green through this - most(?) chandleries offer the same thing. To get away from it, I think you need to get into commercial suppliers (chandleries or specialist lifting / handling companies) where legislation requires the use of properly made equipment.

Just for clarification, I don't have any affiliation with any of the companies mentioned - I've got some materials / metallurgy knowledge, but above all, I'm a manufacturing person.

Soap box is getting some hammer this week /forums/images/graemlins/smile.gif

Andy
 
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IWhy are the tested shackles apparently so weak, or is it that the non-tested ones are subject to some marketing spin and would actually test much lower?

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You've got it! /forums/images/graemlins/smile.gif

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Also - any views on these:

http://baselinemarine.com/shopdisplayproducts.asp?id=34&cat=Rapid+Links

Very high breaking load (9000kg) and a 1800kg SWL (for the 10mm version).

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Looks like the pukka stuff, but they are still using the old term SWL, not WLL. Breaking load should be higher for stainless than 'ordinary galvanised'. Don't know how well it would go around the windlass. Note that breaking load is >4 times WLL (SWL) - i.e. credible.

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Edit - Also just found this company www.s3i.co.uk - they do tested shackles in all shapes / sizes. They give suggest SWL and breaking points on the site, but will test individual shackles too (although they want £60 set up and 90p per shackle for testing and certificate).

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I've used S3I for standing rigging, and believe they know their stuff.

Just to clarify something: There's no way I'd bother with a test certificate for a shackle / link for my own use, but I would be more inclined to buy one from a supplier who was prepared to offer test certificates to a recognised standard for the same product - it's all about establishing the credibility of the supplier. If the shackle, etc. is supplied as suitable for lifting use, it should come with a certificate of conformity, anyway.

Whether it comes with a certificate of any sort or not, if it looks badly made, then it *is* badly made.

It really is a minefield.

Andy
 
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Has anyone actually had a C-link fail in service???

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When Hylas added his mark on these forums he used to say that he knew of poor quality C-links failing.

I had one for many years without any problem, but since it was looking a little rusty I changed it for a new one. Big mistake! The old one was considerably better.

The answer seems to be that C links are fine - so long as you go for a good one.
 
Thanks Andy, I have just ordered some of the shackles with a flush pin from S3I - as you say anyone who is prepared to test their shackles and produce a certificate carries more weight with me.

I am prepared for any problems with this link passing over the windlass, but being a flush pin I hope to have mitigated the problems as far as possible.

Thanks again

Jonny
 
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The answer seems to be that C links are fine - so long as you go for a good one.

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And that's my problem. I've got a stainless steel C-link that's been on the chain since before I owned the boat. I don't really want to take this off and perhaps replace it with something that might even be inferior!! The YM article gives a kind of green light (with caution) to SS links, so until I'm sure I have something better, it's staying on. I'm very rarely in a situation where the chain is highly loaded, and if it is there's a long nylon snubber is use. So 99% of times if the c-link is out of the locker it's to get scope in a deep anchorage, not to ride out a storm. I'll sit tight for the time being and just be aware it MIGHT be a weak link and take appropriate action if needed.
 
Personally I think this is sensible. The stainless ones seem to be much better than some of the mild alternatives. I don't like the idea of a stainless link in a galvanised rode and would replace as and when a good alternative is found, but in the mean time I would not lose any sleep (literally!) over it. When you look at the chain loads under normal anchoring conditions they are not that high.
 
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