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AS 4991Pending revision

Lifting devices

A practical guide to below-the-hook lifting devices: define the device and duty, trace the load path, design for stability and fatigue, then verify, mark, inspect and control its use.

01

“Do we have to physically proof-load this custom lifting beam, or can calculations, FEA and NDT be enough?”

The verification question comes after the device, duty, load path and design basis are defined. A polished FEA image is not a substitute for a complete lifting-device lifecycle.

02

The practical answer

AS 4991 covers lifting devices that connect to a crane hook and handles design, device-specific requirements, testing or verification, marking, information, inspection, repair and care in use.

The device should be designed for its real duty, not only a single static lift. Load cycles, dynamic effects, off-centre loading, sling geometry and operating environment can matter.

Stability and control of the suspended load are part of the design problem, especially for lifting beams, adjustable devices and mechanisms.

Verification can involve proof loading or an alternative pathway where the Standard permits and the required evidence is produced. The correct route should be selected before manufacture, not after the workshop asks how to close out the job.

AS Applied rule of thumbChoose the scope, design basis and evidence pathway first. Do not start by hunting for a single clause, percentage or formula that makes the preferred answer work.
03

Where this Standard fits

Common starting points
  • Lifting beams and spreader beams
  • Custom below-the-hook frames
  • Plate clamps and friction lifters
  • Vacuum and magnetic lifting devices
  • Bulk-material grabs
  • Purpose-built attachments connected between the crane hook and load
Do not assume
  • The crane itself
  • Ordinary slings and rigging gear covered by other product Standards
  • A structural bracket merely because it has an eye hole
  • A reason to rate a device from FEA stress alone
  • Permission to proof-load an unknown device without engineering assessment
  • A substitute for lift planning and safe use of the crane system
04

Define the lifting device, duty and verification route early

The safest time to decide how a device will be verified is before steel is cut.

1Confirm it is a lifting deviceDefine the boundary between crane, hook, rigging, device and lifted load.
2Define load and dutyRated capacity, load cases, sling angles, centre-of-gravity variation, dynamic effects, cycles and environment.
3Trace the complete load pathEvery plate, weld, pin, lug, shackle interface and adjustment mechanism should have a clear force path.
4Check stability and useConsider rotation, tilting, accidental release, incorrect configuration and how operators know the device is locked or correctly assembled.
5Select verification before manufacturePlan proof loading or an accepted alternative verification route, including calculations, material evidence, NDE and inspection.
6Mark, document and inspectRated capacity, identification, configuration limits, instructions and ongoing inspection complete the lifecycle.
The most common failure is a broken chain of assumptions.

A good result needs the equipment definition, loads, design method, fabrication, inspection and operating limits to describe the same real system.

05

Key engineering concepts to understand

01

The load path must be obvious

A lifting device should not rely on unintended plate bending, partial contact or an assumed weld distribution that is not physically credible.

02

Rated capacity is configuration-dependent

Adjustable pick points, sling angles and centre of gravity can change forces even when the lifted mass stays the same.

03

Stability is a design requirement

The device and load should remain controlled through lifting and transport, not only at the instant of take-up.

04

Fatigue can govern reusable devices

Repeated lifting cycles and welded details require more thought than a one-off static load test.

05

Verification is broader than FEA

Model assumptions, material traceability, weld quality, dimensions, NDE and the real manufactured device all matter.

06

Marking prevents misuse

A device can be structurally adequate yet unsafe if users cannot identify capacity, allowed configurations or required attachments.

06

Detailed engineering case studies

The examples below show how the Standard changes a real engineering decision. They are not clause summaries or universal answers; each case starts with the equipment, task and evidence available.

Case study 1 · Custom lifting device

Workshop-made spreader beam for repeated maintenance lifts

01
Project context

A maintenance team needs a 5 t spreader beam for removing a motor every shutdown. The workshop proposes an RHS beam with welded end lugs and asks for an FEA report after fabrication.

Why this Standard matters

The lifting device needs a defined duty, load path, stability and verification route before fabrication. Retrospective analysis cannot create missing material traceability or controlled weld details.

What made the job difficult

  • Sling geometry creates compression and local lug forces not obvious from lifted mass alone.
  • The motor centre of gravity can vary with attached components.
  • The device will be used repeatedly over many shutdowns.
  • No marking or inspection plan has been proposed.

How the engineering review should proceed

  1. Define lifting configurations, rigging geometry, load distribution and credible eccentricity.
  2. Select the structural design basis and assess global members, local lugs, welds, buckling and fatigue-sensitive details.
  3. Choose and document the verification route before fabrication.
  4. Specify marking, instructions, inspection and configuration control for the completed device.
Practical outcome

The device becomes an engineered asset with traceable design, controlled manufacture, verification and lifecycle requirements—not a fabricated beam accompanied by a stress plot.

Also investigate
AS 3990 where adopted for structural designRelevant rigging standardsNDT and inspection procedures
Case study 2 · Plant modification for lifting

Adding permanent lifting lugs to heavy equipment

02
Project context

A site wants to weld four lifting lugs onto a large gearbox housing support frame so the assembly can be removed without slings around the body.

Why this Standard matters

The lug is only one part of the lifting device system. The parent structure and the load path through the equipment also need to withstand the new lifting case.

What made the job difficult

  • The equipment was not originally designed to be lifted from the proposed locations.
  • Load sharing between four points is uncertain.
  • The frame sees a different force direction during lifting than during operation.
  • The proposed welds are near existing fatigue-sensitive details.

How the engineering review should proceed

  1. Define the centre of gravity and credible unequal load distribution between lift points.
  2. Trace forces from each lug into the parent frame, not just through the lug plate itself.
  3. Check local plate bending, welds, frame stability and any temporary lifting orientation.
  4. Specify proof/verification, marking and an inspection basis for the new lift points.
Practical outcome

The final design may require local reinforcement or a different lifting arrangement. A strong lug attached to a weak parent structure is still an unsafe lifting solution.

Also investigate
AS 3990 / AS 4100 parent-structure assessmentEquipment OEM requirementsLift planning and rigging arrangement
Case study 3 · Configurable lifting device

Adjustable lifting frame with multiple pin positions

03
Project context

A fabrication business wants one adjustable frame to lift several products of different widths and centres of gravity. Telescoping beams and multiple pin holes create many possible configurations.

Why this Standard matters

The critical challenge is configuration control. A device can be safe in one setting and overloaded or unstable in another.

What made the job difficult

  • Not all pin positions produce the same member and connection forces.
  • Users may assemble asymmetric configurations in the field.
  • Wear at holes and pins affects long-term fit and load transfer.
  • Marking must communicate permitted configurations clearly.

How the engineering review should proceed

  1. Define every permitted configuration and exclude combinations that cannot be safely rated.
  2. Design positive locking and configuration identification so incorrect assembly is difficult.
  3. Assess the governing load effects across the full configuration envelope.
  4. Set inspection and rejection criteria for pins, holes, welds and telescoping sections.
Practical outcome

The engineering output should include a configuration matrix, clear WLL marking, assembly instructions and inspection criteria. Flexibility for the user should not create ambiguity about the safe load path.

Also investigate
Human factors and instructions for useProof/alternative verification routeOngoing inspection and repair controls
07

Common mistakes

Designing from lifted mass only

Sling geometry, eccentricity, dynamics and load distribution are omitted.

Calling a static stress plot verification

FEA is used without material traceability, weld assessment, buckling, fatigue or manufactured dimensions.

Adding lifting lugs to existing plant casually

The parent structure and load path are not checked for the new lifting action.

Proof loading an unknown device

A test is treated as a substitute for understanding brittle fracture, fatigue or hidden defects.

No configuration control

Adjustable devices can be assembled in unsafe positions without positive locking or clear marking.

Poor retirement criteria

Inspection finds damage but there is no documented repair or disposal pathway.

08

Information to gather before making the decision

Device type and boundary

Rated capacity and all configurations

Lifted load centre of gravity and variability

Rigging geometry and connection hardware

Dynamic and horizontal actions

Expected lift cycles and duty

Material grades and traceability

Weld details and fabrication method

Environmental exposure and corrosion

Verification and proof-load plan

Marking and operating instructions

Inspection, repair and retirement criteria

09

What should happen next?

1

New custom device

Design the device and verification route before fabrication begins.

2

Existing undocumented device

Quarantine or restrict use as appropriate until identity, materials, condition and capacity can be competently assessed.

3

Modified device

Reassess load path, duty, verification, marking and inspection as a new engineering change.

4

Repeated high-duty use

Define fatigue and inspection requirements from actual duty rather than relying on periodic visual checks alone.

5

Complex or novel device

Use project-specific lifting-device engineering and independent verification where consequence and uncertainty justify it.

Related AS Applied content

10

Source basis & limitations

  • This page explains design and verification logic without reproducing proof-load values, detail tables or device-specific requirements.
  • Safe use, rigging practice and crane operation require additional Standards and lift-planning controls.
Project-specific engineering

Need the Standard applied to real equipment?

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