Which size and type of chain?

[noelex 77]

Originally Posted by Cheechako

I dont understand the immersion concern, SS cant get oxygen depleted in immersed water... water has a lot of Oxygen in it!

Corrosion of stainless steel underwater is a very complex area that is a bit beyond the scope of this thread even if I actually understood the subject .

Crevice corrosion is only one of the mechanisms. If we look just at this corrosion mechanism as you say it is not a great factor in SS exposed to free flowing seawater, but say under the substrate where the shackle will spend much of its life the conditions are such that there is a greater risk, especially in the head and threads of the stainless steel pin. Here oxygen levels can be low where there is stagnate seawater. The head, or threads of the pin can corrode without any obvious signs. The risks of a serious loss of strength are not very high, but it is higher with the 630 grade stainless used in the HR shackles. G8 shackles do not have this problem. G8 is significantly stronger than 316 SS and similar in strength to the HR SS. I think one of the G8 shackles are are a superior choice and are a lower cost without any galvanic action with the zinc. (All this is assuming galvanised chain and anchor)

Originally Posted by Cheechako

If you weld heat treated chain dont you just create a soft weak link? It would have to be welded prior to not just galvanizing but also heat treating....

Yes good point. The idea is to get the chain manufacturer to install the larger link during the manufacture of the chain and as you point out this should be before heat treating.
It would be possible to get a local welder to install a larger link of say G4 steel the next size up (12mm for 10mm chain). The strength would be about the same. I think the welding could be done without effecting the heat treatment of the G7 chain, but the larger link would be ungalvanised, QC would be hard and it is not an option I would recommend.

[noelex 77]

Originally Posted by JonJo

Cheechako
One does wonder how West Marine customers cope with this issue as WM sell in 'random' lengths and have no facility to add extra links. The suggestion seems to be that people are either using undersize and incompatible strength shackles, or they get the local welder to add the links - which all seems to defeat the object of using the G7 in the first place.

If ordering G7 the ideal is is to get the manufacturer of the chain to add some larger links. This permits the use of shackles that are stronger than the chain which allows for some derating of shackle strength due to side loading. It also means you can reasonably use a large range of "ordinary" shackles which are readily available. (I would always use at least a good quality rated lifting lifting shackle)

However, without a larger link it still possible with a bit of care to fit a shackle with a rating around the same as the G7 chain.

For example with 10mm G7 the chain specifications are:
SWL 2100kg UTS 11000kg. The "hole" where the pin has to fit through is about 13.5-13.7 mm depending on galvanising thickness and how the link is welded.

The shackle options would seem to be:
Crosby 209A 7/16 WL 2750 kg "minimum" ultimate load 12300kg
(This has a pin size of 12.7mm so should just be OK on 10mm chain)

Crosby 209A 3/8 WL 2000 kg "minimum"ultimate load 9000kg

Whichard titanium ti 12mm WL 2800 kg BL 8000kg

Whichard HR 12mm WL 3600 kg BL 10000kg

So I would suggest doing the comparisons yourself for the size chain you wish to purchase and the availability of the shackles that can be obtained.

[JonJo]

It is interesting that a Crosby shackle has a completely different safety factor to a Witchard shackle - and both are different to the safety factor for the quoted chain. They are all in an anchor rode, to be used in the same environment, under the same type of load. Other manufacturers of gal G8 shackles used for lifting use a 6:1 factor and anchor chain 'usually' has a safety factor of 4:1, 3:1 for purveyors of G43, but that quoted above - approx 5:1.

Safety factors seem used simply to confuse.

I might tend to look at the minimum breaking load and then 'consider' WLL

In the example quoted the only shackle that is compatible with the chain is the Crosby 7/16th inch. All the others are under strength (based on minimum breaking strength).

The chain costs a fortune and the shackles, in comparison, peanuts, I would want my 'cheap' shackle to be stronger than the expensive chain - is this unreasonable or unrealisitic?

I'm not disputing the figures that Noelex quotes but I identify that the dimensions are, particularly of American imperial components, nominal and that one manufacturer's 7/16th inch is slightly smaller and another's slightly larger than the 'nominal' 7/16th inch. I'd be actually taking a shackle and checking it actually fits.

Safety factors themselves are an interesting can of worms.

Jonathan

[noelex 77]

Originally Posted by JonJo

It is interesting that a Crosby shackle has a completely different safety factor to a Witchard shackle - and both are different to the safety factor for the quoted chain. They are all in an anchor rode, to be used in the same environment, under the same type of load. Other manufacturers of gal G8 shackles used for lifting use a 6:1 factor and anchor chain 'usually' has a safety factor of 4:1, 3:1 for purveyors of G43, but that quoted above - approx 5:1.

Safety factors seem used simply to confuse.

I might tend to look at the minimum breaking load and then 'consider' WLL

Ideally the shackle has a higher WL and UL than the chain. This is quite easy to achieve with a larger link on G7. Without a large link you need to do some searching, but it is still possible to do (at least for 10mm chain) as the numbers show. I don't think we need be too concerned about West Marine customers at least if they read CF

The problem of saftey factors is an interesting one. Normally the WL would be the more important number to match rather than UL. However shackles used for different purposes have different saftey factors. A shackle used for lifting wants a more conservative saftey rating than a shackle used for less demanding applications.

It has been assumed that this is the only consideration in the selection of the saftey factor. I am not a metallurgist, or even an engineer, but common sense would suggest the standard deviation of results must also play a significant role. (If we could get some input from real engineers that would be great)

Different materials will have a different standard deviation in the UL numbers. Even different manufacturing techniques must play a role.

The WL also needs to be to be lower for chain than a shackle because there are multiple links.

Thus two shackles with an identical UL can have a different WL. If we are comparing like with like I think the WL is the more important number. Three shackles have a WL over the chain rating which widens the options although I would rather have more of a safety factor to ensure that the shackle never becomes the weakest link.

[noelex 77]

Originally Posted by JonJo

I'm not disputing the figures that Noelex quotes but I identify that the dimensions are, particularly of American imperial components, nominal and that one manufacturer's 7/16th inch is slightly smaller and another's slightly larger than the 'nominal' 7/16th inch. I'd be actually taking a shackle and checking it actually fits.

Checking it fits is a good idea, but I did not convert the data from imperial. The data was from Crosby themselves in metric.

[JonJo]

Noelex,

Interesting perspective.

As mentioned on this thread (and others), G3 chain has a safety factor of 4:1 - yet chain failure (of branded chain) is almost non existent when used in an anchor rode.

Stainless shackles, of which you are wary, have lower, WLL closer to min break strength, safety factor than gal HT shackles. - This implies thay are 'safer' than gal shackles (I'm with you, slightly uncomfortable)

When chain is proof tested the whole and actual chain is tested, shackles are batch tested 1 in 100, of 1 in 1,000 - or whatever. This might explain why some shackles have a 6:1 factor, but not why others have a 3:1 factor.

If WLL is the figure to watch - why would G3 chain in America and Europe have a safety factor of 4:1, G4 chain in Europe a safety factor of 4:1 but G43 chain in America have a safety factor of 3:1?

The suggestion is that G43 was originally used as a Transport Chain, which had a 3:1 safety factor and now that it is used as an anchor chain it has 'inherited' that same safety factor - in total contradiction to the rest of chain used for anchoring - makes little sense to me. Its an excellent marketing tool for purveyors of G43 - but looks slightly questionable.

Jonathan

[JonJo]

Originally Posted by noelex 77

Checking it fits is a good idea, but I did not convert the data from imperial. The data was from Crosby themselves in metric.

I was not casting aspersions on your maths - more on the 'roundings' used by manufacturers.

I should have some Crosby HT shackles in the next 10 days or so, gal, bow, 3/8th inch (as per your data) - I'll be checking then against the same specs you are quoting.

Jonathan

[noelex 77]

Originally Posted by JonJo

The suggestion is that G43 was originally used as a Transport Chain, which had a 3:1 safety factor and now that it is used as an anchor chain it has 'inherited' that same safety factor - in total contradiction to the rest of chain used for anchoring - makes little sense to me. Its an excellent marketing tool for purveyors of G43 - but looks slightly questionable.

That reason is often quoted and certainly makes sense.
However, it has resulted in people dismissing the WL rating and concentrating just on the UL.

The number with the most relevance our chain and our shackles is the minimum load where failure is a possibility. So the WL should be the most important factor if we can compare like with like specifications.

A shackle that breaks consistently at 8T is preferable to a shackle that might break at 5T for one sample and 12T on another, even though the latter has the the higher average UL.

This does have some practical application. If we consider these two shackles ignoring cost, corrosion etc which would you pick? The other question is the Whichard shackle "stronger" or "weaker" than 10mm G7 chain ? Are these differences in the ratio of WL to UL a result of a different standard, or are they as a result of a difference in the standard deviation of the UL data?. Whichard do not apply an identical safety factor to all their marine shackles which suggests they taking standard deviation and the amount of quality control into account when selecting the higher WL figure. Then again it could be just marketing

Crosby 209A 3/8 WL 2000 kg "minimum"ultimate load 9000kg

Whichard titanium ti 12mm WL 2800 kg BL 8000kg

Having said all of the above the most important thing is not to team your G7 chain with a no name cast shackle. Providing you are sensible (and hopefully these post at least make people think about the problem) most of these minor differences are academic rather than practical.

[JonJo]

You raise another query based on what seems to be an interesting recommendation.

You are suggesting use of Titanium as a critical 'joint' in the anchor rode.

Ostensibly it seems strong enough.

Have you based your recommendation, or suggestion, on actual practical experience? How does titanium react to prolonged immersion in seawater and on constant immersion and then exposure to oxygen. How does titanium react when constantly abraded by zinc (the galvanising), a Zn/Fe alloy, that alloyed layer and then steel underneath. How does titanium react when constantly snatch loaded?

No trick questions here - titanium is so little used in the populist marine industry I have seen no data to support, or not support, its usage in an anchor rode.

But why bother with titanium there are pretty high tensile strength aluminium alloys that might be cheaper, for example 7075 as used in the Anchor Right alloy Excel shank.

Jonathan

[HappyMdRSailor]

Wowsa....

I LIKE.... chain and all.... It's fun stuff... But the last few pages were like chain pron on crack... You guys know your shizzit....

[JonJo]

Originally Posted by HappyMdRSailor

Wowsa....

I LIKE.... chain and all.... It's fun stuff... But the last few pages were like chain pron on crack... You guys know your shizzit....

And a bit of thread drift never did anyone any harm

Sadly, I'm on foredeck tomorrow, racing, windward/leewards, and too much mental stimulus here will further destroy my concentration tomorrow.

Maybe the thread will get back on track or move to less 'geeky' topics

Jonathan

[HappyMdRSailor]

Originally Posted by JonJo

And a bit of thread drift never did anyone any harm

Sadly, I'm on foredeck tomorrow, racing, windward/leewards, and too much mental stimulus here will further destroy my concentration tomorrow.

Maybe the thread will get back on track or move to less 'geeky' topics

Jonathan

I can stress/strain/UTS/SWL/yeild/cycle/corrode/modulusahootie etc... with the best of 'em...

But I find my true calling to be self entertaining thread drifts...

have fun tomorrow... No bumps... No flags...

[noelex 77]

I have not used titanium in this application, but it seems entirely suitable.

Titanium's main advantage of low weight is of course not useful in this application but its high strength, and very high corrosion resistance are major assets.
It is not subject to crevice corrosion like stainless steel.

It is most noble of the metals (apart from gold and platinum) so there will be some loss of the zinc from the chain and anchor due to galvanic activity, but titanium forms a relatively non conducting layer on its surface so the effect is likely to be similar to using a stainless steel shackle. Stainless steel only gives a slight problem in this regard (due to the low mass of the shackle compared to the chain and anchor) and I would predict titanium to be similar.

The final drawback is cost, but considering the total cost of the chain and anchor the impact is minor especially considering the long life.

7075 aluminium is not very corrosion resistant and is not suitable for use underwater.

[HappyMdRSailor]

Originally Posted by noelex 77

I have not used titanium in this application, but it seems entirely suitable.

Titanium's main advantage of low weight is of course not useful in this application but its high strength, and very high corrosion resistance are major assets.
It is not subject to crevice corrosion like stainless steel.

It is most noble of the metals (apart from gold and platinum) so there will be some loss of the zinc from the chain and anchor due to galvanic activity, but titanium forms a relatively non conducting layer on its surface so the effect is likely to be similar to using a stainless steel shackle. Stainless steel only gives a slight problem in this regard (due to the low mass of the shackle compared to the chain and anchor) and I would predict titanium to be similar.

The final drawback is cost, but considering the total cost of the chain and anchor the impact is minor especially considering the long life.

7075 aluminium is not very corrosion resistant and is not suitable for use underwater.

Just one more very valid reason not to be carrying 200' of 10mm 14k... Bet you would be galvanizing like crazy...

[Blue Crab]

We had a commercial titanium vendor on CF for awhile. I hope he's lurking and will check in.

In the US mid Atlantic region at least, the commercial fishermen seem to use proof coil, as an example from marine supplier Paxton Co:

PEERLESS CHAIN "Grade 30" proof coil chain. Hot galvanized, low carbon steel. Priced and sold per foot. Cut to order chain cannot be returned. Size 1/4", Working Load Limit 1250, Feet Per Drum 400

Why wouldn't this be suitable for recreational boats? I suspect the answer relates to windlasses, but they're not retrieving chain by hand.