spreader beam members: chain or tubing?

Hello vscid

The twin chain/spreader lifting beam combination system as shown in your picture has several advantages immediately apparent:

1. Storage space is much less than the square type frame alternative.
2. The chain acts partly in compression on the lower beam, thus is stronger than the square type frame alternative.
3. The lifting hook of the crane does not to be as accurately positioned, because the chain self-adjusts, during the initial part of the hoisting movement.

There are others, but the three above are the most advantageous.

Kind Regards....

greetings mr. sparky,

as usual a smack on answer, you can get it backed up even better from two sources

1) a set of industrial injury case settlemnts which have decided on why accidents in lifting electric motors killed or severly injured workers in two Ontario Canada manufacturing plants is available through that countries labor union of hoisting engineers

2) look at many of the ship buiding riggers manuals, those guys don't play around with anything welded to i beam other than the through bolted and welded u bolt sling sets columbus mckinnon puts out.

'da ber

But if I am lifting a heavy load, wouldnt the load swing more with a chain and thus input an additional dynamic load?

Hello "Guest",

Having been personally involved with, and observed many loading situations over 50+ years, the chain/rope strop/wire rope/strap combined with a spreader beam seems almost universal.

Thus it is not just a habitual usage, it must be best.

One major problem of using "square tube" for any load bearing application, is that internal weld joints are not easily inspected, unlike the "I Beam" spreader, welded lugs and chains as pictured.

Kind Regards....

If this beam shown in the picture, is loaded with say 3000lbs, and the CG of the load is offset from the pick point, by a certain distance 'x', can I apply beam equations to this situation? How would I determine the thickness of my beam? Is it safe to assume this beam as cantilever?

I agree with Sparkstation here. This beam/chain combination is a proven and economical design, plus it is very easy to make a quick visual inspection of all components. I should note that in the U.S.A. and many other countries; that documented periodic inspection of load-handling equipment is required by law.

Plus, the beam/chain design is very adaptable. Longer (but never shorter than design!) proof-tagged chains can be easily connected to the beam for situations that require a different approach-such as when there may be a partial overhead obstruction. I agree that the integrity of the seam welds of the steel tubing would be most difficult to verify.

As far as calculating the design characteristics required for the use of steel tubing? it would be a cantilever calculation for the most part, but a tensile calculation would be required as well in order to properly size the tubing/welds. And the danger of an underdesigned rig would be the sudden failure that would come without warning! Chain elongation/link thinning can be easily measured. One cannot say the same about the tubing and its required welds.

Me? I have moved a lot of heavy equipment and my money is on the commercially-available beam/chain rigging.

Best Regards,

Ing. Robert Forbus

No, I mean if I use the spreader I beam,for my calculations, would that be a cantiliver with one end fixed? Would that be a case of pure bending (when I apply the offset load on it) ?

Great question.

1) The adjust-ability of the chain, when in the field and not at the drawing board; is the primary advantage, (especially if it is being rigged from an elevated level and requires load adjustment, due to unforeseen conditions). At 45 degrees, (maximum safe efficiency of the inverted bridal legs) the chain can easily be shortened to accommodate the cantilever, safely and quickly adjusting the load to center, during test-pick.

2) Your spreader "legs" may be restrictive, (unless you build an adjustable version), which becomes costly and less desirable for ordinary use and adds weight, due to extra tubing.

3) Although box tubing is strong, pipe is a far stronger choice, as the diagonal loading can cause square stock to deform, should an accidental bump to the rigging, during lift. (It happens).

4) The dynamic of a shock, such as would occur during accidental crane malfunction, or when a rigged load re-adjusts, or worse yet, should a clevis or shackle fail altogether, would make the chain a better performer. This important factor allows dynamic shock to be absorbed; during catastrophic failure, or should the crane lower the ball below the triangle, when setting the load down. The tubing will still be ridged and will be tough to lower, without binding the clevis and shackle. You'll be giving very slight commands to your crane operator, just to lower the load so you can remove or adjust the leg, should it become necessary. Not safe.

5) The chain works a machine, (just as the wire rope), and the stock tubing may be considered a non-mechanical device; as it cannot react or flex very much or independently of the triangle, to which it is attached. The triangle becomes ridged and the tubing would remain a solid unit during critical failure, absorbing less inertia. Chain handles torsion far better than tubing, when you desire flexibility.

6) Proper load rated tubing will most certainly work, when engineered properly and has NO welded seam, (point of failure). The chain is "handy", just watch out for binding, twist, load rating certification and proper diameter for the shackle intended to hold the load. Twisted chain is a no no.

7) Chain sling or sling component use is governed by the U.S. Department of Labor OSHA regulations. In particular, Section 1910.184 governs the operation and usage of alloy steel chain slings and sling components. A chain sling or chain product must always be operated in strict accordance with federal OSHA regulations. Any user or operator of a chain sling device should be completely familiar with these OSHA requirements.

8) Your tubing legs would need to be engineered and certified for use on any Federal project, without a doubt. The engineer of your tubing legs, would assume all liabilities, should it fail; instead of a "known" chain manufacturer. This would not be considered best-practices; unless you are self-insured. Why bother with the added risk?

9) Draw-back:

Several shackle manufacturers use over-sized pins to accommodate for lower grade steel, therefore some rated chains will not allow the use of such low-quality devices, as they will not fit without binding the chain; (even if the load-rating-stamp on these shackles, can be assumed as accurate). No thanks to over-sized diameter shackles, thank you.

No matter what they say these shackles, (hate to call them that), are rated for, they are rarely batch tested to conform with the above standards and rarely conform to International load-lifting-standards; (as per a major US laboratory).

Rig The World.

I think the good reply to that question is an example showing a full design of a spreader bar to include all elements and factors of design with various types of sections attached with simplified sketches and stress analysis. In case of there is no available example, I appreciate if there is an internet site to include a text on that subject and similar stress analysis.

My problem is that I will be using this spreader beam (made of chain or tubing) to lift multiple parts (about 6 of them) ranging from 1000 lbs to 2500 lbs. (one after the other) . The CG of these parts however, are at different positions from each other and from the pick point. Would using a counterweight serve my purpose of balancing them?

Also, the chain introduces some swing (play) into the lift. I cannot tolerate much play while delivering my part. Hence, wouldnt a rigid structure like welded beams be advisable?

Okay, I think that I now see the reason for your post. You wish to produce a single item for specified material handling purpose-not a mass-produced or distributed item that may bring consequences due to unintended/improper use.

I think in that case that a weldment will be fine; just design it with a minimum safety factor of 200% and take into account dynamic loading-not just static loading. Another thing that will influence your design is the possible abuse it may encounter, i.e. someone accidentally tries to lift the device while it is still attached to a part that may be fixed. For that you may wish to place a limit on the amount of force that the lifting hoist can exert-through a fail-safe clutch (mechanical) or programmable current overload. That way your lifting fixture, as well at the conveyed part is safe from damage.

We are all careful with such things as we have yet to defy gravity-at least on a long-term basis.

Best Regards,

Ing. Robert Forbus