DNV-ST-0373 covers the design, manufacture, and certification of lifting devices — the broad category of equipment used to handle and transfer loads on ships and offshore facilities. It complements the permanently-installed marine crane standard DNV-ST-0194 and the lifting operations standard DNV-RP-0232. Where ST-0194 governs cranes installed as class equipment on vessels, ST-0373 covers the design side of a wider range of lifting devices including below-the-hook equipment, lift points, spreader beams, and detachable lifting attachments.
The standard is relevant whenever lifting equipment is to be designed, fabricated, and marked with an SWL for use on offshore facilities or vessels — whether or not the equipment is subject to classification. It also interfaces with the EU Machinery Directive (2006/42/EC) for equipment placed on the European market.
1. Scope and Equipment Categories
DNV-ST-0373 applies to lifting devices designed for lifting and handling loads, including:
- Below-the-hook lifting devices: spreader beams, lifting frames, balance beams, C-hooks, coil lifters, vacuum lifters, and magnet lifters
- Lifting points and pad eyes: permanently welded or bolted attachment points on structures (for dedicated structural pad eyes, see DNV-ST-0378)
- Detachable lifting fittings: shackles, hooks, swivels, turnbuckles, chain links, and ring bolts when designed per this standard
- Sling assemblies when supplied as a complete certified set with an SWL
The standard does NOT cover:
- Permanently installed cranes (→ DNV-ST-0194)
- Offshore containers (→ DNV-ST-0378 and EN 12079)
- Wire rope slings (→ EN 13414-1), chain slings (→ EN 818), or textile slings (→ EN 1492) as standalone products
- Lifting operations (→ NORSOK R-002, DNV-RP-0232)
2. SWL, Rated Capacity and Equipment Rating
DNV-ST-0373 uses Safe Working Load (SWL) as the primary rated capacity for lifting devices. The SWL is the maximum load that the lifting device is certified to lift under its intended operating conditions.
| Term | Definition | Notes |
|---|---|---|
| SWL | Safe Working Load — the maximum load the device may lift in normal service | Marked on the device; the basis for proof load calculation |
| WLL | Working Load Limit — equivalent to SWL, used in EN and ISO standards for sling and rigging hardware | DNV-ST-0373 uses SWL; WLL is used in product standard complements (EN 13414, EN 818) |
| SWL at angle | Reduced rated capacity when a sling, hook, or shackle is loaded at an angle from the design axis | Must be specified where equipment is used in multi-leg configurations; sling factor applies |
| Dynamic SWL | Reduced rated capacity for dynamic (offshore) lifting in sea states above specified limits | Applies when the standard design load includes dynamic amplification; reducing SWL in heavy weather operations is an operational control |
SWL Marking Requirements
Every lifting device designed to DNV-ST-0373 shall be indelibly marked with:
- The SWL in tonnes (or kN)
- The standard reference (DNV-ST-0373) or the applicable product standard
- Manufacturer identification and serial or batch number
- Year of manufacture
- CE marking (if placed on the EU/EEA market under the Machinery Directive)
3. Load Cases (LC1–LC4)
DNV-ST-0373 defines four load cases that cover the range of loads encountered during the device lifetime. The load case framework aligns with DNV-ST-0378 and DNV-ST-0194 to provide a consistent load hierarchy across DNV lifting standards.
| Load Case | Description | Load Composition | Design Check |
|---|---|---|---|
| LC1 — Normal operation | Routine lifting in benign conditions; no significant dynamic effects | SWL × DAFop | Yielding (ULS); primary design case |
| LC2 — Offshore operation | Lifting in moderate sea state (Hs up to specified limit); dynamic amplification from vessel motion | SWL × DAFoffshore | Yielding (ULS); governs where offshore DAF > operational DAF |
| LC3 — Proof load | Static proof test load; verifies design margins | 1.25 × SWL | Yielding (local) permitted but no permanent deformation; full inspection after test |
| LC4 — Accidental / overload | Unintended overload event; device shall not fracture | Defined by the designer based on consequence; typically 2.0 × SWL for accidental scenarios | Ultimate capacity (fracture prevention); no serviceability requirement after |
4. Dynamic Amplification Factors
Dynamic Amplification Factors (DAF) account for the increase in effective load due to acceleration during lift initiation, vessel motion, and snap loading. DNV-ST-0373 specifies minimum DAF values; higher values shall be used when analysis or historical data indicates higher dynamics.
| Operation Type | DAF (minimum) | Notes |
|---|---|---|
| Onshore / quayside (LC1) | 1.05 – 1.15 | Depends on lifting equipment dynamics; 1.05 for slow controlled lifts, 1.15 for crane with high hook travel speed |
| Offshore, Hs ≤ 2.5 m (LC2) | 1.20 – 1.30 | Standard offshore operation; confirmed calm weather lift |
| Offshore, 2.5 m < Hs ≤ 3.5 m (LC2) | 1.30 – 1.50 | Moderate sea state; should be qualified by dynamic analysis |
| Subsea (through-water) (LC2) | 1.50 – 2.00+ | Entry through splash zone adds snap load risk; lower end for slow and controlled, upper end for dynamic operations |
where:
Fd = design load [kN or tonnes-force]
SWL = safe working load [kN or tonnes]
DAF = dynamic amplification factor (≥ 1.05 for LC1; ≥ 1.20 for offshore LC2)
γf = load factor (1.30 for LC1/LC2 ULS; 1.00 for LC3 proof test check; 0.90 for LC4 accidental)
5. Structural Design Check
DNV-ST-0373 permits both design by formula (simplified allowable stress method) and design by analysis (FEA with factored loads). The structural design check verifies:
Yield Check
where:
σSd = design Von Mises stress under factored load Fd
fy = specified minimum yield strength of the steel grade
Weld Design
All structural welds in lifting devices shall be designed as load-carrying welds. DNV-ST-0373 requires:
- Weld throat area sized for the full design load (LC2 governing for offshore devices)
- Weld quality: minimum weld class W2 (DNV-ST-0378 weld class equivalent) for primary load-carrying welds; fully penetrating butt welds preferred for critical connections
- NDE: visual examination of all welds; magnetic particle testing (MT) or penetrant testing (PT) of primary load-carrying welds ≥ 10% extent; 100% for proof-tested devices > 5 t SWL
Fatigue
Where lifting devices are used in repetitive operations (more than 20,000 cycles over the design life), a fatigue assessment shall be performed using S-N data per DNV-RP-C203. For most offshore lifting devices with lower cycle counts, a simplified fatigue screening based on the number of lifts and load spectrum is sufficient.
6. Proof Load Testing
All lifting devices shall be proof load tested before first use and after each major repair. The proof load requirement in DNV-ST-0373 follows the same principle as DNV-ST-0194:
| Condition | Proof Load | Hold Duration | Acceptance |
|---|---|---|---|
| Standard proof test | 1.25 × SWL | Minimum 5 minutes (static suspended load) | No permanent deformation, cracking, or visible damage; full visual inspection post-test |
| Low-temperature service (−20°C to −40°C) | 1.25 × SWL at ambient temperature; impact testing of material to service temperature | 5 minutes minimum | As above; material certification to include CVN at service temperature |
| After major repair (weld repair to primary member) | 1.25 × SWL | 5 minutes | Full NDE after repair, then full proof test and re-inspection |
The proof test must be witnessed by a surveyor (DNV or other classification society / third-party inspection body acceptable to the owner). The test certificate must record:
- Applied load (measured by calibrated load cell or certified test weight)
- Test duration and ambient conditions
- Surveyor name, authority, and signature
- Visual inspection findings post-test
- Statement of acceptance or rejection
7. CE Marking and Machinery Directive
Lifting devices placed on the European market are subject to the EU Machinery Directive 2006/42/EC. DNV-ST-0373 Edition 2 explicitly addresses the interface between the standard's design requirements and Machinery Directive compliance:
Machinery Directive Classification
- Lifting devices with SWL > 1 tonne, or any lifting device with a risk of falling (gravity), fall into Annex IV (high-risk machinery) and require EC Type Examination by a notified body before CE marking
- Lifting devices not in Annex IV may self-certify under the Machinery Directive using DNV-ST-0373 as the technical file basis
- The CE Declaration of Conformity must list all applicable Machinery Directive Annexes and essential health and safety requirements (EHSRs)
Technical File Requirements
A CE-marked lifting device requires a technical file containing:
- Design drawings with dimensions, materials, and weld details
- Structural calculation report (LC1–LC4 checks, fatigue if applicable)
- Material certificates (EN 10204 type 3.1 minimum for primary structural members)
- Weld procedure qualifications (WPS/WPQR)
- Proof test certificate
- NDE records
- Instructions for use (IFU) in all required languages
- Risk assessment per Machinery Directive Annex I
8. Periodic Inspection and Recertification
| Inspection Type | Interval | Scope |
|---|---|---|
| Pre-use visual inspection | Before each use | User (operator): visible deformation, cracks, corrosion, missing markings, wear on hooks/pins/load-bearing surfaces |
| Thorough examination | Annual (or after any incident) | Competent person: detailed visual + dimensional check; NDE where wear or damage is suspected; review usage records |
| Proof load re-test | Every 5 years, or after major repair, or after any incident that may have overloaded the device | 1.25 × SWL test witnessed by surveyor; full visual inspection post-test; recertification documentation issued |
| Maximum service life | Per manufacturer's specification; typical 10–20 years depending on material, use frequency, and environment | Retirement should be documented; de-rated SWL or scrapping with record |
Discard Criteria
A lifting device shall be removed from service if any of the following are observed:
- Visible cracks in any load-bearing component
- Reduction in cross-section due to corrosion or wear exceeding 10% of original thickness in primary members
- Bent or deformed hook, shackle pin, or structural member beyond elastic recovery
- Missing, illegible, or altered SWL markings
- Threads worn or stripped to less than 75% of original depth on load-bearing threaded connections
- Evidence of overloading: permanent deformation of any member, fracture of any weld
9. Common Pitfalls
- Designing to LC1 onshore DAF (1.05) for a device that will be used offshore — offshore lifting requires LC2 DAF (≥ 1.20) which significantly increases design load; a device designed only for onshore use may be understrength for offshore operations
- Specifying "1.25 × SWL" as the proof load but applying it to the rated capacity of a sling component rather than the device SWL — proof load must be 1.25 × the SWL of the complete lifting device assembly, not individual components
- CE marking a spreading beam as "Annex IV exempt" when SWL > 1 tonne — beams with SWL > 1 tonne are Annex IV machinery and require EC Type Examination; self-declaration of conformity is not sufficient
- Omitting the Instructions for Use from the CE technical file — the Machinery Directive requires IFU in all relevant market languages; omitting them is an immediate CE non-conformance
- Using a 5-year re-test interval as an absolute — if a device is used in a corrosive environment (offshore, subsea), annual NDE and dimensional checks are more appropriate than waiting 5 years for the proof re-test
- Relying on the proof test to catch design errors — the proof test at 1.25×SWL has only a ~25% overload margin; if the design load calculation contains a significant error (e.g. wrong DAF or load combination), the device may pass the proof test but fail at SWL under dynamic conditions
- Using FEA with factored loads for complex spreader beams rather than simplified formula design — for non-trivial geometry, FEA catches stress concentrations at pin holes and weld toes that hand calculations miss, and demonstrates adequate fatigue life for high-cycle applications
- Documenting all lifts over SWL × 0.5 in the device history log — enables the thorough examiner to identify patterns of high utilisation and schedule earlier re-test or retirement
Query DNV-ST-0373 in Leide
Ask about load case requirements, DAF selection, proof load specifics, CE marking obligations, or discard criteria — Leide retrieves the exact clause from the ingested standard.