Beam clamp off axis

[TomHoward]

Does anyone know a beam clamp please that can be loaded in this axis:

 

I've got a beam which doesn't run vertical (vertical downwards load off a pitched roof rafter).

I guess the obvious thing would be to strop it, but there's a gas pipe runs alongside which looks like it might be in the line of the round sling.

 

Oh, and it's 22.5degrees off.

[Seano]

Crosby ITPKU gives you 100% WLL limit up to 45 degrees off-vertical to the side of the beam, 15 degrees along it's length (but could be up to 45 degrees depending on conditions - the catalogue is vague about that, you'd have to ask them). I don't know, but I suspect it's rather expensive.

 

Hackett WH-BC superclamp (other than the smallest one) offers a reduced WLL up to 45 degrees across the beam, but nowt along the length of the beam. The design is no different to any number of other clamps on the market.

 

Personally I wouldn't be over concerned about a relatively small fraction of the WLL off-vertical on any of those designs with a shackle built in, such as in your drawing. You'll be using a minimum 3 tonne clamp I guess, and looking at a load under about half a tonne? Of course this is just some random bloke on the internet talking here...

(You may find one of the manufacturers willing to tell you the same thing if you ask nicely, dunno. Or possibly a structural engineer, for a modestly eye-watering fee.)

 

Other options:

For a permanent installation some custom-fabricated metalwork attached to the beam with Linndapter flange clamps. I'm picturing a heavier duty version of the Linndapter based thingamabob Doughty do. (Which, come to think of it, might actually do you if you're talking about a very modest load.)

 

As you suggest, sling it. Soft-steel or round sling basket with an extra wrap won't slide down the beam at 22 degrees if it's clean and grease-free, nor will a choke.

Alternatively you could use gravlocks to clamp a short section of scaff tube across the beam to ensure a regular basket won't slide.

 

Alternatively alternatively you could hang your load from that tube with a half-coupler or whatever. One end if it's v light, or a small bridle between both ends for nice.

[TomHoward]

Thanks for that, if using a non-designed clamp with a shackle and loading to say 22degrees, would you document using it not as designed? Make your own 50% or 75% factor and justify it using that?

Slinging, the issue is this gas pipe. From the ground I can see the smallest crack of light between the beam and pipe but I'm just worried a round sling might foul the pipe and push against it.

 

Gravlocks and half couplers and eyes underneath would work. Especially as then I can straighten the eyes back to vertical as well.

[Seano]

.. would you document using it not as designed? Make your own 50% or 75% factor and justify it using that?

 

No, I'm not qualified for that. Either I'd be happy that the load is trivial, in which case I wouldn't bother to 'justify' anything in writing (the method statement would simply refer to the use of a beam clamp and leave it at that) -or- the load is significant, in which case I'd want a proper grown-up structural engineer involved.

 

Gravlocks and half couplers and eyes underneath would work. Especially as then I can straighten the eyes back to vertical as well.

 

What's going on with the gas pipe? I assumed from the OP that it was running perpendicular to the beam, but I guess not. Is it above, or to the side? Are you sure there's enough room to get in with a spanner to tighten a gravlock? It definitely needs to be properly nipped up.

 

A 1-tonne SpanSet is pretty skinny (almost disturbingly slim, when you're used to using 2t slings for everything). With a bit of patience you can feed one through a surprisingly narrow gap.

 

Doughty have a handy sheet for Gravlocks here: clicky.pdf

 

They're giving a pair a SWL of 600kg, based on the working loads given in BS5973 (I think - don't have access to a copy of that now) of 30kN hanging load, 10kN slip along the beam at a 2:1 FoS.

 

My unsubstatiated gut-feeling is that I wouldn't be particularly comfortable with much more than half of that tbh.

 

[Edit to add: some back-of-an-envelope sums kinda sorta confirm that - taking a worst case slip load of sin(22.5) x vertical load, and a v conservative 8:1 FoS, that 10kN translates to SWL 330kg odd.]

 

I don't know what the permissible shear load on a regulation bit of steel scaff tube is, but safe to say it'll be more than that so the limiting factor is most likely your half couplers. (Yes, definitely good practice to orient them to the load btw.) Even if you do bridle between two of them bear in mind that a hoist towing a wee bit one way or the other perpendicular to the beam could easily transfer most of the load to one clamp or the other so it'd be wise not to exceed the SWL of a single half-coupler, and if you're hanging a truss in that orientation it'd be worth taking time to place the pick-ups accurately.

[TomHoward]

Yeah the loads are low, under 100kg per point I expect.

The gas pipe runs along the side of the RSJ between the flanges to service a heater at the roof apex. It's clamped to the top flange of the RSJ about every 4ft with a clamp that holds it about 100mm down from the top but only just out, maybe flush with the outside of the RSJ flange. Going over the pipe would definitely compress it into the beam but the roundsling might just tuck underneath and not deflect it. The beam is 400mm height so there's plenty of room to mess around at the bottom with gravlocks.

[Seano]

Yeah the loads are low, under 100kg per point I expect.

 

Call it 120kg and that's 4% of 3000kg. If it were my gig I'd put it on a 3t clamp as per your drawing in the OP, check the beam is reasonably clean & not greasy, give it a wipe if necessary, nip it up tight (not *too* tight if you have the arms of a gorilla) and not give it a second thought. This being the BR, I expect someone will be along shortly to tell you how wildly irresponsible I am. ;)

[david.elsbury]

Is there anyone else who can't see a pic of a pipe?

[Seano]

Me. And everybody else I assume - there isn't a pic of the pipe.

Only pic on the thread so far is Tom's diagram of a beam clamp in the OP.

[TomHoward]

I did take a pic but it came out so poor because of a light next to it that you could barely make it out:

 

Illustration: (position approx - I've drawn it at the inside of the pipe being flush with the outside edge of the beam, which it is about.

 

 

Half the problem is usually 'looking' right. Whilst stropping it might miss the pipe, it might rub against it, and although in practice it's really unlikely to make any difference, if a year down the line some problem develops with that pipe no doubt there'll be someone suggests it'll be when we stropped it. For these reasons and it being gas I'm inclined just not to get involved with going anywhere near it and clamp onto the bottom of the beam.