Lift point - codes and standards comparison

This page provides an overview of five key standards used in the design, manufacturing, and operation of lifting equipment and structures.

We will compare and contrast these standards, highlighting their scope, applicability, and key requirements with a focus on design and load test factors.

It is worth noting that some of these standards provide guidance to account with operation specific conditions like environmental loads (sea state and wind), hoisting speed, load distribution uncertainty and more. The study below neglects most of these effects in an attempt at a like for like comparison. This highlights the importance of a dedicated structural analysis for each application.

Applicability

EN 13155 Crane - Safety - Non-fixed load lifting attachments

Applicable to onshore applications.

DNVGL-ST-0378 Standard for offshore and platform lifting appliances

This standard focuses on lifting appliances used on offshore platforms and structures. These are typically large, fixed structures like oil rigs, gas platforms, or wind turbines, anchored to the seabed.

DNVGL-ST-0377 Shipboard lifting appliances

This standard covers lifting appliances used on ships.

DNVGL-ST-E273 Portable Offshore Units

This standard specifically addresses Portable Offshore Units (POUs), which are temporary structures or modules transported to offshore locations for specific operations.

DNVGL-ST-N001 Marine Operations and Marine Warranty

Applicable when the focus is on the structural integrity of the vessel.

1 Offshore installations are usually fixed Structures: These are typically large, fixed structures like oil rigs, gas platforms, or wind turbines, anchored to the seabed.

Comparison

Below is a side-by-side comparison of the design and load test factors recommended in these standards when considering a 25 tonne padeye.

* This code gives preference to a test load from either to DNVGL-ST-0378 or DNVGL-ST-E273 as relevant.

Note: Two standards in this list also provide design guidance specifically for padeye design:

DNVGL-ST-0378, Appendix E
DNVGL-ST-N001, Appendix P.2

The following collapsible region shows a breakdown of the relevant sections, tables and assumptions used to determine the previous factors.

EN 13155

EN13155, section 5.1.2.2, risk coefficient: 1.4

EN 13001-2, section 4.2.2.2, dynamic factor on hoist load when hoisting an unrestrained grounded load in regular operation: 1.2

EN 13001-2, table 12a, partial safety factor: 1.34

Total design factor: 2.25

EN 13001-2, section 4.2.4, test load factor: 1.25

DNVGL-ST-0378

Appendix E, section E.1.4.1, load factor: 1.5

Appendix E, section E.1.4.1, test load factor: 1.2

DNVGL-ST-0377

Table 7-1, partial safety factor: 1.34

Table 7-1, global safety factor: 1.48

Section 7.2.3.2.2, dynamic factor: 1.4

Total design factor: 2.78

Table 7-2, test load factor: 1.43

DNVGL-ST-E273

Table 3-5, design factor: 2.25

Section 3.5.5, lift point additional design factor: 1.2

Total design factor: 2.7

Table 5-2, test load factor: 2.25

DNVGL-ST-N001

Section 4.4.3.4, consequence factor: 1.4

Table 5-10, load factor: 1.3

Total design factor: 1.69

Section 5.4.3.5, test load factor: 1.52

Observations

The previous load factors reveal an interesting and important point about the differences in how these codes approach safety. It seems counterintuitive that DNVGL-ST-N001 and DNVGL-ST-0378, dealing with the harsh marine environment, would have a lower load factor than EN 13155, which is often used for more controlled onshore settings.

Here's a breakdown of the potential reasons for this apparent discrepancy:

Different focus and scope

EN 13155: This standard focuses on the lifting accessory itself. The higher load factor (2.25) likely aims to cover a broader range of applications and potential misuse scenarios, including dynamic loads, shock loads, and variations in manufacturing quality. It's a more generalized standard for various lifting accessories.

DNVGL-ST-0378: Even though this standard deals with marine environments it is mostly applicable to fixed structures subject to lower dynamic loads (when compared to floating structures covered by DNVGL-ST-0377). Otherwise, what is said about DNVGL-ST-N001 below is also applicable to DNVGL-ST-0378.

DNVGL-ST-N001: As we've discussed, this standard focuses on the overall marine operation. The lower load factor (1.69) is applied within a broader framework of risk management and operational controls. This framework includes:

Detailed Planning: Extensive planning of the marine operation, including weather forecasting, sea state analysis, and lift simulations.
Competent Personnel: Use of experienced and qualified personnel for all stages of the operation.
Strict Operational Procedures: Adherence to well-defined procedures for lifting, transportation, and installation.
Marine Warranty Surveyor (MWS) Involvement: Independent oversight by an MWS to verify the suitability of the operation and adherence to best practices.

Accounting for dynamic effects

EN 13155: The higher load factor might be a simpler way to account for dynamic effects in a more general context, without requiring detailed analysis of specific operational conditions.

DNVGL-ST-N001: This standard encourages a more detailed analysis of dynamic effects, considering factors like vessel motions, wave-induced loads, and current forces. By explicitly analyzing these factors, a lower overall load factor might be justified.

Statistical basis and historical data

The load factors in each standard are likely based on a combination of theoretical analysis, historical data, and industry experience. Differences in these underlying data sets and assumptions can lead to variations in the chosen load factors.

Level of control and supervision

Marine operations under DNVGL-ST-N001 often involve a higher degree of control and supervision compared to more general onshore lifting operations covered by EN 13155. This higher level of control might allow for a lower load factor while maintaining an acceptable level of safety.

Tanking into account the above points, the seemingly lower load factor in DNVGL-ST-N001 doesn't necessarily mean it's less conservative. It reflects a different approach to safety, where a more detailed analysis of operational conditions and a higher level of control are used to justify a lower load factor. EN 13155, on the other hand, adopts a more generalized approach with a higher load factor to cover a wider range of applications and potential uncertainties.

Conclusion

The information provided in this article is intended for general knowledge and information purposes only, and does not constitute professional engineering advice. Lifting point design is a complex and highly specialized field. The specific requirements for each lifting application can vary significantly depending on factors such as the type of load being lifted, the lifting environment, the frequency of lifts, and applicable local regulations.

Therefore, we strongly recommend that you consult with QZM Engineering for any specific lifting point design or analysis. We have extensive experience in lifting point design and can provide tailored solutions to meet your unique needs.

Get in touch with us at enquiries@qzm-engineering.com .

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