check fittings

aom said:
I see what you were getting at now Cala. I'm obviously not sure of the exact loads but I think Jason was right when he said it does reduce but it still ups the loads. If one is starting to just slip there will not be the same load on the next and practically nil on the third.

The usual disclaimer applies.:embarrest:

---------- Post added at 06:56 PM ---------- Previous post was at 06:53 PM ----------



That's a new one on me Swifty, I was always taught to turn the check upside down and at right angle to it's neighbour so it fits snug almost male and female like so it was tight.
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me too ,,,always upsidedown 45% NO DAYLIGHT ...
 
Karlj711 said:
Doing part two with John Ellis at the moment. It's 6.1kn for the double it's then reduced by 50% per check (complimentary) fitting. So the second fitting is 3.05kn & then 1.52kn so & so fourth from there. So basically by the time you reach the fourth fitting, in theory it's doing nothing.
Hope this helps.
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This is not logical and has to be wrong.

On your (the John Ellis) basis, a single puncheon on a single ledger with two check fittings has the loading capacity you have quoted.

However should the puncheon be on both chords of a beam with just one check fitting over one chord, it will be 6.1 + 6.1 + 3.05 which is substantially stronger using the same fittings.

Move on to doubled up beams over four chords and single fittings alone (no checks) become more than enough.

Once you have sufficient check fittings to get up around the design leg load of the relevant class of scaffold then any more just add self weight and increase the load unnecessarily.

Three fittings at 6.3kN (about 650 kilogramms) is 1950 kg which is your basic 2 tonne leg load, the basis of most scaffolding design.

Anyway, EN 12811 changed the SWL of a load bearing class B fitting from 6.3 to a notional value (for calculation purposes) of about 10kN
 
I think its to do with the supplementary/check fitting on ly have a tube running through one way so its not working to its full capacity.
 
Because of the ultimate strength limitations on the main coupler, a supplementary coupler arrangement is normally limited to the use of one main coupler plus one supplementary coupler, which could be expected to give the following maximum safe working loads:-

2no Class A Doubles – 12.50kN
2no Class B Doubles – 18.75kN

Don’t confuse a ‘check fitting’ with a ‘supplementary fitting’ – a check fitting is just that – a fail-safe.

A supplementary fitting is required where there is enough strength in the tubes, but not enough strength in a fitting to take the required live loads.

A gap should never be left in-between the main coupler and the supplementary (or check) coupler, as this could produce a dynamic force that may cause the second fitting to fail.
 
phil181 said:
A gap should never be left in-between the main coupler and the supplementary (or check) coupler, as this could produce a dynamic force that may cause the second fitting to fail.
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Nice informative post Phil and thanked by Simian.

But wrong regarding the gap, we have performed an impact test on two identical platforms one with check fittings touching and one with a 3mm gap between fittings.

The checks that were touching failed before the second fitting failed on the checks with a gap.

Before you all come back to this arguing your views do the test as we did.
 
Haha, Cala, I think that clears it up, is there anything else you wish to know.:embarrest:
 
No.. thats all perfectly clear now :eek:
 
its not just me then :worried:

---------- Post added at 05:38 PM ---------- Previous post was at 05:35 PM ----------

Maybe its like the " Ark of the covenant " and only the keeper knows it strengths and powers , passing on the knowledge and wisdom of the "class B" double with his last breath to the new keeper
 
haha, I'm watching mid-summer murder on 3 and I would say it had more to do with the pudding club.:nuts:
 
oh right, now the thread all makes sense.:nuts:
 
Or you could just read TG17:03 Identification of EN74 Scaffold Fittings.
 
Extracted fro TG14:03

Supplementary couplers are added where the estimated working force in a scaffold tube at its
connection point is greater than the maximum safe working load capacity of a single load-bearing
coupler.
Supplementary couplers are sometimes incorrectly referred to as check couplers, safety couplers,
or back-up couplers. Supplementary couplers are active couplers which add known strength to
the connection whereas check couplers are used to give added security in situations of high risk
to personnel.
Typical design applications where high coupler forces could be expected and which may require
the use of supplementary couplers are:-
Diagonal braces in the lower lifts of a scaffold
Suspended and slung scaffolds
Cantilever loading platforms
Lifting gantries
Truss-out and cantilever scaffolds
Loading towers
Falsework structures
Pedestrian bridges and walkways
Because of the ultimate strength limitations on the main coupler, a supplementary coupler
arrangement is normally limited to the use of one main coupler plus one supplementary coupler,
which could be expected to give the following maximum safe working loads:-
Supplementary coupler Maximum safe
working load
12.50kN
18.75kN
10.60kN
(NOTE: As recommended in clause 39.8.2 of BS 5973:1993 the advice of the coupler
manufacturer should always be sought.)

If the estimated force in the tube is in excess of these maximum safe working load figures, then
either further advice should be sought from the coupler manufacturer/supplier as to the load
bearing capacity of their particular couplers or an alternative scaffold design solution should be
sought.
Only right-angle couplers (also known as doubles) or swivel couplers should be used as
supplementary couplers. Putlog couplers (also known as singles or half couplers) should never be
used in this application.
Because BS 1139 does not contain any test requirements for supplementary couplers, it is
recommended that the coupler manufacturer's advice should be sought as to the suitability of his
couplers to act as supplementary couplers, the manner in which they must be used and the safe
working loads.
I Check Couplers
Typical design applications where high risk to personnel situations may arise and which may
require the use of check couplers are:-
Hanger tubes
Suspended or slung scaffolds
Truss-out scaffolds
Only right-angle couplers (also known as doubles) or swivel couplers should be used as check
couplers. Putlog couplers (also known as singles or half couplers) should never be used in this
application.
Where a combination of high coupler forces and a high risk to personnel simultaneously occurs, it
may be necessary to install a supplementary coupler arrangement plus a check coupler or an
alternative scaffold design solution should be considered.
 
With all the talk of check fittings going on, is there any thought of the load crushing the fitting/ s or the tube?
 
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