shackle tested

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kenp

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Looking for a shackle to attach the ground chain to the mooring rope, but what size shackle. If you have a 6 tonne boat and the shackle is said to be tested to say 6 tonnes does this mean that that is the minimum shackle you should have on your mooring or is more to do with being capable of lifting 6 tonnes.
 
I would just get the biggest shackle that will fit the chain! Even a quality tested shackle is likely to be fairly small money compared to the cost of the the whole outfit.
 
The important question is not the nominal strength, but how long it will last in a corrosive environment before it needs to be replaced. In that scenario, bigger is better - and so is quality of galvanising. Pay for quality - it will repay with a much longer service life.
 
'Tested' figure will normally mean the SWL value x2, usually 1/2 of the UTS. It is sometimes known as the Proof Load. In this case your shackle would fail at 12 tons but should not be used above 3 tons.

However, a 6 ton boat will never exert a 6 ton load on a mooring or anchor rode. Even the very conservative ABYC theoretical tables predict less than one ton and measured values are about half of that.
 
kenp said:
.... shackle is said to be tested to say 6 tonnes ....
Click to expand...

When buying shackles or other devices they are normally specified as having a Working Load Limit (WLL). This term is replacing the term Safe Working Load (SWL). The SWL is now used for the whole system e.g. you may use a 50t shackle in a lifting assembly because of the opening size, which is connected via sling (or chain) to a 10t shackle on the load. The SWL of that assembly is 10t.

The point I am making is that you need to understand what the specification is of the item that you are buying. I have bought many shackles and the term Tested is used on the certificate and it represents the so called SWL. This term is being replaced with WLL. So your tested to 6t shackle, may be rated for use at 6t. So what vyv_cox is stating may not be true (3t SWL) but it could be, so you have to be careful to understand what you are reading on the specification.

For and example see here where WLL is now used in a product catalogue: http://www.thecrosbygroup.com/html/default.htm

There has been a drive over the years to eliminate all the terms on loose items such that the figure you see is the maximum force that you can use the device to i.e. the consumer doesn't have a clue what they have been proof tested to, only the Working Load Limit that they can apply to the device.

As others have said buy the largest that will fit for wear and corrosion purposes.
 
BlowingOldBoots said:
When buying shackles or other devices they are normally specified as having a Working Load Limit (WLL). This term is replacing the term Safe Working Load (SWL). The SWL is now used for the whole system e.g. you may use a 50t shackle in a lifting assembly because of the opening size, which is connected via sling (or chain) to a 10t shackle on the load. The SWL of that assembly is 10t.

The point I am making is that you need to understand what the specification is of the item that you are buying. I have bought many shackles and the term Tested is used on the certificate and it represents the so called SWL. This term is being replaced with WLL. So your tested to 6t shackle, may be rated for use at 6t. So what vyv_cox is stating may not be true (3t SWL) but it could be, so you have to be careful to understand what you are reading on the specification.

For and example see here where WLL is now used in a product catalogue: http://www.thecrosbygroup.com/html/default.htm

There has been a drive over the years to eliminate all the terms on loose items such that the figure you see is the maximum force that you can use the device to i.e. the consumer doesn't have a clue what they have been proof tested to, only the Working Load Limit that they can apply to the device.

As others have said buy the largest that will fit for wear and corrosion purposes.
Click to expand...

I'm not saying you are wrong but I have googled ten marine shackle suppliers. These include ship, fishing and leisure suppliers. Some quote minimum break load, some quote another term that means the same and several quote SWL. None quote WLL.
 
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