Rated/unrated shackles

[Chris Lowe]

At my place of work we have an acoustic shell that is attached to a fly bar and flown when it is used. The shackles attaching this to the bar, and therefore bearing the load, have no rating for weight, only a rating for force (Nm). I was just wondering if this is legal to use as I have a feeling its not. I would appreciate it if anyone could tell me as I have a long standing argument with my Technical Manager on this subject. Thanks

[Simon Lewis]

Regulation 7 of LOLER states that the lifting accessory must be stamped with the SWL.

 

It should also be CE marked and have some form of identification to facilitate periodic inspection and record keeping.

[Chris Lowe]

Regulation 7 of LOLER states that the lifting accessory must be stamped with the SWL.

 

It should also be CE marked and have some form of identification to facilitate periodic inspection and record keeping.

 

 

ah lovely cheers. I had a feeling I was right on this matter but couldn't be sure. Cheers for the help

[Bryson]

Hang on.... Were you planning on using these devices on any other planets or planetary type objects? :P

 

Because if you're staying here, you can work out weight limits from force limits very easily. Weight is merely the force applied by gravity.

[Brian]

SWL = Safe Working Load. A Load is a Force applied to something and Force is measured in Newtons.

[Bryson]

Further to my post, in fact, Force is preferable, as it allows you to use those devices anywhere in the universe you like. You just need to know the local value of g.

 

:P

[Chris Lowe]

well I was planning on using them on my next visit to Mars. I hear its warm this time of year which is nice!! But they still have to have the SWL stamped on the piece of equipment?

[ChrisD]

Chris, I think the point here is that the SWL is actually a value which should be measured in Newtons. So these shackles ARE rated AND stamped, just in Newtons rather than Kg. To find out the rating in Kg, just multiply the Newtons by 9.8 (for Earth).

 

SO, although you see SWLs marked in Kg, they should actually be in Newtons. However, that's a totally different kettle of worms I really don't want to open.

[TomLyall]

To find out the rating in Kg, just multiply the Newtons by 9.8 (for Earth).

Divide. 1kg is 9.8 Newtons.

 

Are you sure it says Nm? That'd be Newton metres, and that's a unit of moment (torque).

[mumbles]

Chris, I think the point here is that the SWL is actually a value which should be measured in Newtons. So these shackles ARE rated AND stamped, just in Newtons rather than Kg. To find out the rating in Kg, just multiply the Newtons by 9.8 (for Earth).

 

SO, although you see SWLs marked in Kg, they should actually be in Newtons. However, that's a totally different kettle of worms I really don't want to open.

Seeing as how force = mass x acceleration (GCSE physics), then mass = force/acceleration. The acceleration is 9.81m/s/s, and the force is the newtons, so you should be dividing the force by 9.8, not multiplying. If you multiply, then your answer will be overestimating the SWL by a factor of almost 100.

 

EDIT: Oh beaten to it again.

[ChrisD]

Sorry, long day of ALevel physics. Good job someone checks my calculations.

 

Divide is absolutely right. 1N is approximately 100 earth grammes, or 0.1kg

[AndrewR]

well in an attempt to resolve this......

 

Climbing equipment like caribiners are normally marked with a breaking strain. This does not allow a safety factor. To derive a SWL from this divide the figure by 5 (this is the accepted safety factor, 5:1 for lifting equipment not lifting personnel, CE regs allow 4:1, and personnel lifting is normally 10:1. All of these are accepted code of practice figures and will vary depending on the specific operation)

 

So for caribiners as I use for hanging some black legs...

 

The caribiners are marked as 35 KN. or a breaking strain of 3567 Kg (ignoring decimals). Using a 5:1 safety factor it means the SWL is 713 Kg.

 

Its perfectly acceptable to use equipment that is only marked with a breaking strain, provided that its being used by a person competent to do so (i.e. someone who understands that they need to apply a safety factor and what that should be, and has demonstrated their ability to do so).

 

Yes it should be marked to allow individual identification, and should have a certificate of conformity to identify it to a batch no larger than 25 units (or individually). This should have been supplied by the manufacturer. And yes it should have a CE mark. Not that this will be relevant, as its climbing gear, not actually lifting equipment, so the CE lifting regs will probably not apply.

 

If its not already marked, get a sharpy and give it a number (most of my gear is so marked, on the advice of the insurance surveyor, as its all relatively lightly used). If it only has a breaking strain, get a 'competent person' to mark it with a SWL. (Regs just say it needs to be permannent)

 

If your employer can demonstate in its method and code of practise that it is taking all 'reasonably practible' steps to minimise risk, (detailing the method and reasoning for reaching a SWL for something with just a breaking strain, for example) then you should be fine.

 

If you really want to have an argument with the technical manager, read up on the subject. There are some good books out there (by Mr Chris Higgs for one!) Then ask to see the inspection schedule and the certificate of conformity for the caribiners (or similar paperwork showing safety factors etc)

 

In many ways I personally prefer having a breaking strain, it means I actually know the safety factor. Instead of wondering if its the CE 4:1 or the more normal 5:1 (which could be annoying when derating for personnel) And as they are often marked in newtons it makes you think more about dynamic loads too! In fact all of the shackles I have are just marked with a weight, not actually mentioning SWL. However the manufactuerers paperwork does explain that it is the SWL and what the factor is.

 

Oh and all mass calculations were made using nominal earth g at sea level. :P

[trussmonkey]

to add my two penny worth,

 

if your talking about climbing equipemnt and ppe etc then although the karabiner ( for example ) has a breaking strian stamped on it the actual SWL is only ONE PERSON (except in special cercumstances like rescues).

 

for more clarification on ppe and work equipment you can phone Dave Ellis at Lyon Equipment.

 

TM

[MartinGreen]

All dynamic lifting equipment should be marked and stamped with its WLL in KG or tonnes (metric not imperial), not in KN or any other measurement. This is stipulated within LOLER and the preferable marking system is within there also.

 

If you want to resolve the issue I would ask where the certificates for the shackles are and contact the supplier/manufacturer. The certificate should stipulate a WLL on the goods in either KG or tonnes. I have never seen lifting shackles rated in KN and think you should look to replace them in my opinion, assuming that they are actually being used for lifting and not suspension (which brings another argument entirely into play). Also bearing in mind the cost on shackles it isn't going to break the bank.

 

Please note that there is also a difference now between the WLL and SWL.

 

The Working Load Limit is what is usually stamped on equipment like shackles etc etc. However like in the case of BGV-C1 hoists for example the Safe Working Load on a hoist can be lowered when there is a larger safety factor applied or a competent person judges that there are conditions/factors in place that mean the Working Load Limit needs to be reduced. As a rule the SWL can never be higher than the WLL on a piece of equipment but it can be lowered.

 

And breathe!

 

P.S, whilst there could be validity in the KN rating the KG and t system means there are no calcs needed and its a one size fits all solution.

[Chris Higgs]

PPE is rated in terms of minimum breaking load. The employer's competent person then applies the required factor of safety to ensure the equipment is used appropriately.

Typically, PPE is only rated as a one person load as TM says, and rarely expected to be used to support two people except for example in the case of rescue. (This is a good example of what MG was referring to - the user makes a judgement about what the component will be doing and applies an appropriate factor of safety to ensure the component never carries a load that it is unlikley to be able to sustain safely)

 

Lifting equipment used over stages should be used with a safety factor of 8 to comply with BS 7905 and 7906 (with a few exceptions).

It seems highly likely to me that the OP's set up was provided and installed as a system; the components are fairly likely to be plenty strong enough.

A means of identification for inspection purposes may be more important the the SWL/WLL since it may be that the shackles mentioned will only be used to do this job. If they are multi-purpose (interchangeable lifting accessories) , then an SWL is definitely needed to allow the user to use them appropriately.

 

Any doubts, get the TM to speak to your insurance engineer and if necessary get an expert in to look at the shackles.

 

Nm is definitely not something you'd see on a shackle or a karabiner....

kN or kg (or even lbs or cwt).