§ 11 Loads, load effects and resistance
The design loads that will form the basis for design and operation of installations, systems and equipment, shall be determined. When determining design loads, the requirement to robust solutions, cf. Section 5, and the requirement to risk reduction, cf. the Framework Regulations Section 11, shall form the basis. The design loads shall ensure that installations, systems or equipment will be designed such that relevant accidental loads that can occur, do not result in unacceptable consequences, and shall, as a minimum, always withstand the dimensioning accidental load.
When determining design loads, the effects of fire water shall not be considered. This applies to both fire loads and explosive loads.
Installations, systems and equipment that are included as elements in the realisation of main safety functions, cf. Section 7, shall as a minimum de designed such that dimensioning accidental loads or dimensioning environmental loads with an annual likelihood greater than or equal to 1x10-4, shall not result in loss of a main safety function.
When determining loads, the effects of seabed subsidence over, or in connection with the reservoir, shall be considered.
Functional and environmental loads shall be combined in the most unfavourable manner.
Facilities or parts of facilities shall be able to withstand the design loads and probable combinations of these loads at all times.
Section last changed: 01 January 2015
Design loads as mentioned in the first subsection, comprise functional, environmental and accidental loads, inter alia fire and explosive loads, which form the basis for design and operation of installations, systems and equipment. As regards definitions of the terms design accidental load and dimensioning accidental load, reference is made to Section 3.
Functional loads as mentioned in the fifth subsection, mean, in the case of load-bearing structures, permanent and variable loads.
Dimensioning loads as mentioned in the third and sixth subsection, comprise functional, environmental and accidental loads, inter alia fire and explosive loads.
In order to fulfil the requirements related to load-bearing structures, the standards NORSOK N-001 and NORSOK N-003 should be used. In addition, NORSOK N-004 should be used for steel structures.
In order to assess the loss of main safety functions as mentioned in the third subsection, the standard NORSOK Z-013 Appendix B should be used.
The NORSOK S-001 standard should be used for accidental loads, in particular Chapter 5.6, in addition to other standards mentioned in these instructions. Special fire conditions such as jet fires, under-ventilated fires in modules, fire on the sea and the like may require additional calculation of fire loads / actions. For mobile facilities that are not production facilities, and that are registered in a national ship register, DNVGL-OS-A101 Paragraph 2 can be used as an alternative.
For facilities that are intended to leave the field due to bad weather forecasts, the values for environmental loads connected with the least favourable of the following factors may be used:
- Conditions on the field when moving,
- Conditions during moving,
- Weather conditions at the planned new location, with the specified annual likelihoods in NORSOK N-003.
For mobile facilities registered in a national ship register, the loads that the facility has been exposed to and the expected loads during the period for which the consent for use is applied for, should be taken into account.
To fulfil the requirement regarding loads, load effects, resistance and load combinations, the following standards should be used for pipeline systems: ISO 13623 Chapter 6 and DNVGL-ST-F101 Paragraphs 3, 4 and 5 for steel pipelines, DNVGL-ST-F201 Paragraphs 3, 4 and 5 for catenary metallic risers and API 17J Chapter 5 for flexible pipeline systems.
To fulfil the requirements regarding loads, NORSOK D-001 Chapters 5 and 6 and D-010 Chapters 4 and 5 should be used for equipment for conduct of drilling and well activities and other well-related equipment, for example drilling risers, compensators, well control equipment, completion equipment and intervention equipment.
To fulfil the requirement regarding loads, the NORSOK standard L-002, Chapter 6 should be used for pipeline systems in production plants.
If the loads, load effects or resistance factors are uncertain, measurements or model experiments should be conducted to increase the quality of the analyses. The NORSOK standard N-003 should be used for model experiments on load-bearing structures.