Class A & B fittings (1 Viewer)

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Most fittings are marked class A or class B when you look at them - have seen some swivels marked class A/B - what does that mean?
 
BS EN 74 doubles have a SWL of Class A - 6.1kN and Class B - 9.1kN

All swivels have a SWL of 6.1kN.
 
I believe you can have class B swivels too....at least according to TG20 you can.

Yes, the class A/B marking is somewhat inconclusive. One interpretation is that it is class A and B compliant....I.e: a class B fitting....but that's just my/one interpretation - check with the manufacturer if you can find them!
 
I believe you can have class B swivels too....at least according to TG20 you can.

Yes, the class A/B marking is somewhat inconclusive. One interpretation is that it is class A and B compliant....I.e: a class B fitting....but that's just my/one interpretation - check with the manufacturer if you can find them!

Dangerous game taking a SWL from a manafacturer!
 
My understanding is A/B means A or B - but what's the point in that? Why not just put B?
Was informed by a Guru of the NASC technical committee it meant this - doesn't sound convincing though does it!
 
My understanding is A/B means A or B - but what's the point in that? Why not just put B?
Was informed by a Guru of the NASC technical committee it meant this - doesn't sound convincing though does it!

Yes that's my understanding in that it complies with A and B...but like you say why not just say B
 
we should forget all the A, B, or A&B bullish!t and make fittings like they used to be, instead of all this foreign tin, far to many failures lately.

cheap sh!te


rant :mad:
 
be carefull theyll be chinese copy and theyve stamped them AB as they dont know what it means.This has been highlighted before
 
The best advice is contained in TG17 and EN74
 
we should forget all the A, B, or A&B bullish!t and make fittings like they used to be, instead of all this foreign tin, far to many failures lately.

cheap sh!te


rant :mad:

Actually Jakdan - you're right - while us designers like the option of being able to design with both A & B (as we can get the extra strength when we need it by specifying B) we need to recognise very few companies control their stock to point that they would actually separate their A & B fixings - or go the the expense of only holding Class B fittings. Most of the time I see a mix of fittings on site so the risk is you specify B and get A!

We normally default to A in design but do sometimes specify B when we really need it but then flag this up with massive warning sysbols on the dwgs. After that I've no idea what happens...
 
The swivel is loaded at a 6.1kn b 9.1kn that is only to stop the slippage of the tube the pin is only loaded at 1.4kn (depending which way you use this fitting in theory it is only loaded at 1.4kn)
 
Not sure about that - if you put 9.1kN thru a swivel in slip you are putting 9.1kN also thru the pin in Shear. My understanding was that is why adding checks doesn't buy you double / triple the slip because the pin would fail.

Always open to new knowledge though - where did you get the 1.4 reference from?
 
It is impossible to put a check fitting on a Swivel of any Load because of the loading of the pin ( the answer to your question I have actually seen it tested in 1 of the factories where I was invited to see how they come to the Aquitaine of slip resistance of all kinds of fittings very interesting) where people would use a Swivel for a Spur they do not understand of the loading Shear,Tension and Compression and Bending you have 4 ways it can be loaded, depending on the location and the nature of the job
 
If you look at the shear area on a pin it would be tiny. Just using a simple 4V/pid^2 with say, an 8mm pin then a load of 40kN would become ~0.8kN in shear (not counting for any vector forces). A pin in this case should be a pure shear connection so if it's gone into bending then something has gone a bit wrong.

EDIT: Just to add thats not counting any additional F.O.S. either :)
 
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The slip resistance of a Double / Swivel is the Safety Factor 1.65kn x SWL 1.65kn x 6.1kn = 10.065 or 1.65kn x 9.1kn = 15.015, again it has a lot to do with your shock load of your Harness that must withstand a shock load of a 1 Ton/1000kg or 10kn
 
Nick - are you mixing Shear with Stress?

If you generate 6.1, 10.065 or 1M kilomegawaffles in slip then that is what you put in to the pin. This is why you can't excessively check swivels as you prevent them slipping but shear the pin in the process.
 
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