Which below-the-hook standard applies to your lift

Engineers reach for this question in the wrong order surprisingly often. The order that works is:

What is the thing? A device that hangs below the hook and is not part of the load is a lifting device, and the lifting device standards apply to it. A padeye welded to a vessel is part of the vessel: the code that governs the vessel governs its attachment, and a lifting device standard has nothing to say about it. A sling, a shackle or a hook is an accessory, rated by its own standard, and neither of the other two families applies.

Where is the lift? Design standards are national or regional. A device designed in one jurisdiction for use in another is designed to the standard of the place it will be used, and that is a contractual question as much as a technical one.

Who is imposing something on top? A marine warranty surveyor, a client specification, or a corporate standard can impose factors above whatever the design route asks for. Those are additional, not alternative.

Get those three answers and the standard is decided. Get them in the wrong order and you end up defending a choice made for the wrong reason.

1. 01Is the device below the hook, part of the load, or an accessory?

   Below the hook

   A lifting device standard governs the design. Spreader beams, lifting beams, C-hooks, coil grabs, vacuum lifters, magnet frames. Continue to the next question.

   Welded to or part of the load

   The code that governs the load governs the attachment. A padeye on a pressure vessel is a pressure-equipment attachment first, and its local shell stresses are a pressure-equipment problem. A padeye on a building steel member is checked to the steel code.

   An accessory between the two

   It is rated, not designed, by its own product standard. Slings, shackles, hooks, eyebolts, links. Your job is to work out the force and compare it with the rating.

2. 02Where is the lift taking place?

   United States

   ASME BTH-1 for design, ASME B30.20 for use. They are used together and neither is complete alone. BTH-1 derives its allowables through a design factor tied to a design category and a service class tied to expected cycles.

   European Economic Area

   EN 13155 for the load basis and proof, EN 1993 for the steel. EN 13155 deliberately does not carry member resistances, so a European route is always two documents.

   Canada

   There is no Canadian below-the-hook device standard. CSA S16 gives steel resistances but no lifting load factor, so the demand-side factor is a declared project value that somebody has to own.

   Australia

   AS 4991 for lifting devices, with AS 4100 for the steel. The same two-document structure as Europe, with a different pair of documents.

3. 03Is anything imposing factors on top?

   A marine warranty scope

   A marine operations standard sets the demand, on top of whichever resistance code you use. Dynamic amplification, skew load and consequence factors. These are additional to the design route, not an alternative to it.

   A client or corporate specification

   Read it before starting, not at the review. Client specifications commonly impose a minimum design category, a minimum design factor, or a proof-test regime, and they are the cheapest thing on this list to discover late.

   Nothing

   The design route's own factors are the whole demand side. Record that it is nothing, explicitly. An absence somebody confirmed is different from an absence nobody looked for.

Two consequences worth carrying:

The design category is a decision about knowledge, not about importance. The higher category exists for devices whose loads are less well defined or whose environment is less controlled. Choosing it because a lift feels important, rather than because the load is uncertain, produces a heavier device without addressing anything.

The service class is a decision about cycles. A one-off lift and a device that runs a hundred times a shift are different problems, and this is where that difference enters the calculation.

The European route therefore produces two families of check on one device: conditions under multiples of the rated load, from the harmonised standard, and member resistances, from the structural code. In the worked example below both appear, and it is the harmonised standard's conditions that come closest to governing.

There are three responses to that, and only one of them is defensible.

Borrow a factor from another country's device standard. Tempting, quick, and wrong, because a factor extracted from one document's scheme does not carry that scheme's other provisions with it. A design factor tied to a design category means something inside the standard that defines both.

Design to another country's standard outright. Perfectly reasonable, if the project agrees to it and it is stated. This is a contractual decision, not a technical dodge.

Declare the load factor as a project value. Somebody with authority states the factor, records why, and owns it. It is then visible on every result, and a reviewer can argue with it.

The third is what Xarpis does, and the behaviour is worth showing rather than describing.

Australia has a device standard, and which pair you need is decided before any of the engineering starts.

The device is the calculator's default arrangement: 10 t on a 6 m circular hollow section spreader, slings at 60 degrees from horizontal, with a 25 mm padeye at each end.

The route is part of the answer. A utilisation without the route named beside it is not a result, because the same steel produces three of them.

The relationship is a stack, not a choice:

1. The design route decides how a resistance is computed and what a check has to satisfy.
2. The marine warranty scope decides what demand goes into it, through factors on the load.
3. The client specification may raise either.

That is why an offshore lift point is heavier than an identical onshore one. Nothing about the steel or the code changed; the demand entering the same check went up.

1. The design standard cited alone. The US design criteria without the safety volume beside them. The device is calculated and its use is unaddressed.

2. The harmonised standard treated as a complete design code. It carries a load basis and proof conditions, not member resistances. A calculation citing it alone has not checked the beam against anything.

3. A lifting device standard applied to a padeye on a vessel. The attachment is part of the pressure equipment. Its local shell stresses are a pressure-equipment problem with its own accepted methods.

4. A factor lifted out of one scheme into another. A design factor tied to a design category is meaningless outside the standard that defines both.

5. The edition unstated. The European standard is now an amended 2020 edition; the US design standard is on 2023. A result that does not say which edition it was computed against cannot be re-checked.

6. A gap filled silently. The one that costs most. Where a jurisdiction has no device standard, the load factor is a decision. A calculation that supplies one without saying so has hidden the single most consequential input, and the reviewer has no way to know.