SY/T 10009-2002 Recommended practices for planning, design and construction of fixed offshore platforms - Load and resistance factor design method (Supplement 1)
Some standard content:
ICS 47.020.10
Registration number: 10478-2002
Petroleum and natural gas industry standard of the People's Republic of China SY/T 10009-2002
Replaces SY/T1MH9-1996
Recommended practice for planning, designing and constructing fixed offshore platform-Load and resistance factor design (Supplement 1)
Supplement I to recommended practice for pfanning, designing and constructing fixed offshore platform-Load and resistance factor design2002-05-28 Issued
National Economic and Trade Commission
2002-08-01 Implementation
API Recommended practice for planning, design and construction of fixed offshore platforms Chapter A Planning
A.1 Overview
A.2 Platform types
A.3 Operational considerations
A.4 Environmental considerations
Choice of design conditions
A.6 Platform reuse
A.7 Exposure classification
A.8 Platform evaluation
A.9 Safety considerations
Chapter ○
Detection levels
Detection frequency
Preselected detection areas
0.6 Records
Chapter R
Evaluation of existing platforms
Platforms Assessment causes
Platform exposure classification
R.4 Platform assessment data
R.5 Assessment process
Sea conditions, earthquake and ice standards/loads
Structural assessment analysis
Selected mitigation measures
R.9 References
Chapter S
Fire, explosion and accidental loads
Loads and resistance factors
Assessment process
Platform exposure level
Probability of occurrence
Risk assessment
SY/T 18009—2002bzxz.net
-Explanation of load-resistance factor design method (Supplement 1) ..…11
SY/T 10009-—2002
S.9 Fire and Explosion Interactions
Commercial External Loads
References
About A.7
Note R.1
Note R.2
Note on Exposure Classification
Note on Assessment of Existing Platforms
Causes of Platform Assessment
Note R.4
Platform Assessment Data
Note R.5
Note R.6
Note R.7
Assessed
Standards/loads for sea conditions, earthquakes and ice
Structural assessment and analysis
US Chapter 10 S Notes on fire, explosion and accidental loads Note S.2 Loads and resistance factors
Note S.7
Note S.8
Note S.9
Expansion of explosive blast
Legal interpretation S.10
Accidental loads ·
Appendix: Recommended practice for planning, design and construction of fixed offshore platforms - Design method for loads and resistance factors
SY/T 100092002
In order to meet the needs of developing offshore oil and gas resources in my country, China National Offshore Oil Corporation, on the basis of the original equivalent adoption of the American Society of Offshore Oil and Gas APIP2A-LRFD: 1993, the People's Republic of China offshore oil and gas industry standard "Recorniended practice for planning, designing and constructingfixed offshore alatform Loud and resistance factor design" (standard number SY/T 10009--1996), continues to adopt the Supplement 1 of the first edition of APIRP2A-LRFD: 1993 (February 197) as the standard of the People's Republic of China petroleum and gas industry. "Supplement 1 is a supplement to the original version. Compared with the original version, the main differences between this standard and the original version are: 1. The definition of operator is expanded as follows: Operator: an individual, manufacturer, company or other organization hired by the owner to perform the operation; 2. The definition of abbreviations is revised as follows:
-American Society of Civil Engineers
American Society of Mechanical Engineers
American Institute of Electrical Engineers
ASTM-American Society for Testing and Materials
American Petroleum Institute||t t||American Welding Society
American Institute of Steel Construction
International Association of Drilling Contractors
(USA) National Fire Protection Association
-Offshore Technology Conference
ACI—American Concrete Institute
NACE (USA) National Association of Corrosion Engineering 3. Recommended to replace the current Chapter A and Chapter O
4. Add Chapter R and Chapter S.
5. Add notes to Chapter A, Chapter O, Chapter R and Chapter S. For the convenience of users to consult the original The Chinese layout of this standard is consistent with the original text and has not been modified. When the laws, regulations and provisions of the government or other competent authorities of the country where the original standard is located are involved in the design, construction and use of offshore natural gas development projects, the relevant laws, regulations and provisions promulgated by the Government of the People's Republic of China or the competent government departments shall be approved: the environmental condition data used in the original standard shall be used as the most appropriate calculation method, and the one that is more suitable for my country's actual situation shall be used as a reference; otherwise, the environmental condition data and quantitative calculation methods that are in line with my country's actual situation shall be used. The units of calculation in this standard , mainly in legal measurement units, that is, legal measurement units are in front, and the corresponding values of imperial units are marked in brackets after them.
In order not to change the formulas, shape characteristics of curves, constants and coefficients in the original standard, if imperial units are used, the imperial single inspection shall still be used.
This standard is proposed and managed by China National Offshore Oil Corporation: The drafting unit of this standard: Development and Design Institute of Offshore Oil Research Center of China National Offshore Oil Corporation. Drafting person of this standard: Shi Zhongmin,
Chief examiner of this standard: Li Yushan,
SY/T 10009—2002
AI Recommended Practice for Planning, Design and Construction of Offshore Fixed Platforms Load Resistance Factor Design Method [Explanation of Supplement 1 API RF 2A -LRFI) Section 1 The edition has been modified as follows: 1. The definition of operator is modified as follows:
Operator: Individual, manufacturer, company and other organization used by the owner to perform the work. 2. The definition of abbreviations is modified as follows:
ASCE—American Society of Civil Engineers
American Society of Mechanical Engineers
AIEF——American Institute of Electrical Engineers
ASTM——American Society for Testing and Materials
American Institute of Petroleum
American Welding Society
American Institute of Steel Construction
International Association of Drilling Contractors
National Fire Protection Association
Offshore Technology Conference
American Concrete Institute
NACE—National Association of Corrosion Engineers 3. Replace the existing Chapter A and Chapter O, add Chapter R and Chapter S, and add the notes to Chapter A, Chapter R and Chapter S.
A.1 Overview
A.1.I Planning
Recommended Practice for Planning, Design and Construction of Fixed Offshore Platforms - Load Resistance Factor Design Method [Supplement 1]
Chapter A Planning
SY/T10009-2002
This publication serves as a guide for those involved in the design and construction of new platforms for offshore oil and gas drilling, production and storage, as well as the relocation of existing platforms. In addition, guidance is provided for the evaluation of existing platforms to determine, when necessary, whether the structure is "fit for purpose".
Before commencing actual design, careful planning should be made so that a practical and economical offshore platform can be built that can achieve the intended performance. Preliminary planning should include all the criteria on which the platform design is based. A.1.2 Design Criteria
The term design criteria as used herein includes all the requirements for use and environmental standards that may affect the design of the platform. A.1.3 Codes and Standards
This recommended practice is compiled from the point of view of public safety and largely adopts existing codes and standards adapted by engineering design and practice.
A.1.4 Operators
Here, an operator is defined as an individual, firm, company or other organization hired by the owner to perform the work. A.2 Platform Types
A.2.1 Fixed Platforms
A fixed platform is defined as a platform that extends above the water surface and is supported on the seabed by piles, extended foundations or other methods and can remain stationary for a long time for its intended purpose. A.2.1.1 Jacket platforms include:
a) A spatial steel frame welded from a guide frame or return pipe, which serves as a guide frame for pile driving and lateral support for piles. b) Piles: It permanently fixes the platform to the seabed and bears lateral and vertical loads. c) Superstructure: It includes trusses and decks necessary to bear operational loads and other loads. 4.2.1.2 Tower platforms have a small number of large diameter columns, such as 5 ml (16 ft). Tower platforms can be floated to the site and placed in place by selective flooding. Tower-legged platforms may or may not be supported by piles: A.2.1.3 Minimum structure It has one of the following characteristics: a) A frame structure that can provide less component margin than a typical four-legged jacket platform. b) A self-standing caisson formed by a large tubular member supporting one or more wells. c) Parallel riser casing or free-standing caisson connected and fixed by welding, non-welding or unconventional welding methods as a structural or axial foundation member.
d) Foundation members (piles or pile sleeves) connected by bolts, pins or clamps = A.2.1.4 Gravity platforms rely on the weight of the structure rather than piling to withstand environmental loads. Except for the contents included in C.13, this recommended practice does not include the design of gravity-type platforms. A.2.2 Other types of platforms
A.2.2.1 Guyed tower platforms are steel pipe frame structures suspended by piles or shallow bearing foundations as vertical supports. Their lateral support is mainly based on the cable system in accordance with SY/T10009-2002. The guyed tower platforms included in this recommended practice are limited to the provisions applicable to them. A.2.2.2 Tension-leg platform is a buoyant platform vertically moored to the seabed. API RP2T is used for this type of platform. A.2.2.3 A spherical platform is a base-type structure with great flexibility. Its flexibility is sufficient so that the external forces acting on it are largely offset by the inertial resistance of the platform movement. As a result, the forces transmitted to the platform and the supporting foundation are reduced. Unless the rigidity of the cable system is very large, the guyed tower platform is usually also spherical. The types of platforms covered by this recommended practice are limited to those that are applicable to them.
A.2.2.4 Other: Other types of structures covered by this recommended practice, such as underwater storage tanks, platform connecting piers, etc., are limited to those that are applicable to them:
A.3 Operational considerations
A.3.1 Function
The functions of the platform being designed are usually divided into drilling, oil production, storage, material handling, living, or a combination of these. When determining the size of the platform, the requirements of equipment operation, such as access, clearance and safety, must be considered. A.3.2 Location
The location of the platform must be determined before the design is completed. ：Design conditions vary with geographic location. In a given geographic area, basic conditions may vary, as may design wave height, period, tide, current, ground motion caused by marine earthquakes.
A.3.3 Orientation
The orientation of the platform refers to the position of the platform on the plane when it is referenced from a certain direction (such as true north). The orientation is usually determined based on the direction of frequent waves, winds, currents, and operational needs. A.3.4 Water Depth
Water depth and tidal information on the site and surrounding areas is required to select the nautical design parameters. The water depth should be determined as accurately as possible to determine the elevation of the mooring platform, guardrails, center plates and corrosion protection areas. A.3.5 Passages and auxiliary facilities
The location and number of ladders and docking platform passages shall be determined from the perspective of safety. Each deck accessible by personnel shall have at least two passages, and their arrangement shall be convenient for personnel to evacuate under various wind conditions. The location of the ladder shall also take into account the requirements of operation. A.3.6 Fire protection
For the safety of personnel and to prevent damage and loss of the platform, it is required to pay great attention to fire protection methods. The selection of fire protection system depends on the purpose of the platform, and the fire protection technology shall comply with the existing government regulations. A.3.7 Deck elevation
Unless the platform is designed to take into account the resistance of the lowest deck to the forces of waves and currents, the elevation of the middle plate of this layer shall be sufficient above the crest of the design wave. A sufficient additional air gap (see C.3.6) shall also be considered to allow extreme waves exceeding the design wave to pass. The gap between decks is determined by the operational conditions. A.3.8 Pipes and risers
When pipes and risers are supported by the platform, they add additional environmental loads to the platform. Their number, size and spatial location should be known early in the planning stage. Pipes and risers may or may not contribute to the platform's wave resistance. Planning should take into account the possible need for additional pipes and risers in the future. A.3.9 Arrangement of equipment and materials
The design should provide for the forces and arrangements related to the gravity loads defined in Section C.2. Concentrated loads on the platform should be distributed to where appropriate support frames can be designed, taking into account future operational requirements. A.3.10 Escape and material loading and unloading
The methods for egress and loading of materials should be planned at the beginning of the platform design. Such planning should take into account the type and size of the supply vessel and the mooring arrangements for securing it to the platform: the number, size and location of the mooring platform and guardrails: the type, lifting capacity, number and location of deck cranes. If any mobile equipment or materials are to be placed on the lower deck, hatches of sufficient size should be opened at appropriate locations in the upper middle plate: the possible use of helicopters should be considered and virtual facilities should be provided. A.3.11 Leakage and pollution
Necessary facilities should be provided to deal with spills and possible pollution. A discharge system should be set up on the deck to collect and store liquids for subsequent treatment. The discharge and collection system should comply with the current regulations of government departments. 1.3.12 Storm station
The design of all systems and components should take into account both normal environmental conditions in advance and extreme environmental conditions that may occur on site.
A.4 Environmental considerations
A.4.1 Overview
The following sections summarize the environmental information that may be required: a) Normal marine hydrological and meteorological environmental conditions (those expected to occur frequently during the service life of the structure) are required for planning site operations (such as installation) and for determining operational environmental loads, see C.3..4. b) To determine the extreme environmental loads, extreme marine and meteorological environmental conditions are required (a condition with a recurrence period of 100 years), see C.3.1.2.
c) To determine the loads mentioned in Section (.4), the environmental conditions for the two seismic levels required are: @① Ground motions that are not exceeded at the site during the service life of the platform by reasonable demonstration; ② Ground motions caused by strong earthquakes that are expected to occur. A.4.2 Wind
Wind forces act not only on all equipment, decks and frames on the platform, but also on the water parts of the structure. The wind speed under normal and extreme conditions needs to be considered.
A.4.3 Waves
Wind-driven waves are the main source of environmental forces acting on offshore platforms. These waves are irregular in shape, with varying wave heights and wavelengths, and may come from one direction or the same direction. The platform is approached from several directions at the same time. Therefore, it is very difficult to determine the magnitude and distribution of wave forces. Both normal and extreme wave specifications need to be considered. A.4.4 Tide
Tide is an important consideration in platform design because it affects: (Forces acting on the platform: ②Elevation of the moored platform guard and deck.
A.4.5 Current
Ocean current is an important consideration in platform design because it affects: (Forces acting on the platform: Position and direction of the moored platform guard.
A.4.6 Marine growth
In most sea areas, marine growth attached to the underwater components of the platform needs to be considered during design. The effect of increased surface roughness of the components and increased diameter and mass of the components on wave and seismic loads should be considered. A.4.7 Floating ice
If the platform is to be installed in a sea area where ice may form or drift, ice and the corresponding ice loads should be considered in the design. This recommended practice does not provide specific design guidelines for ice resistance. For relevant information, please refer to the relevant specifications and standards. A,4.8 Other oceanographic and meteorological data
Other environmental data, including records and/or forecasts of rainfall, fog, cold currents, and temperature and flooding, have different uses depending on the location of the platform:
A.4.9 Geological processes
A.4.9.1 Overview
In many sea areas, geological processes accompanied by surface sediment movement will occur within the fixed design service life. The characteristics, magnitude and recurrence period of possible seabed movement should be evaluated through field surveys and rigorous analytical modeling to provide a basis for determining its impact on structures and foundations. Due to the uncertainty in defining these processes, it is unreasonable to use a parametric study method when formulating design criteria.
A.4.9.2 Earthquakes
For areas that are seismically active, seismic forces must be specifically sensed in the design. Earthquakes are most often judged based on the frequency and magnitude of previous earthquakes. For the design of offshore structures, the seismicity of an area is classified according to the severity of the damage it may cause to the structure. The seismicity of an area is determined on the basis of detailed investigations: the investigation of the seismicity of such areas should include: the instability of the sub-surface soil of the platform site due to erosion, the seabed sliding caused by seismic activity, the distance of the platform site from the fault, the characteristics of the two seismic levels of seismic movement expected during the service life of the platform (see A.4.1, 3) and the seismic risk acceptable to the planned operations: for shallow water platforms that may be subjected to earthquakes, the impact of the resulting forces should be investigated.
A.4.9,3 Faults
In some sea areas, fault planes may extend to the seabed, which may produce vertical or horizontal movement. The cause of fault movement may be seismic activity, or it may be due to the removal of fluids from deep oil, or long-term changes related to large-scale sedimentation or erosion. If possible, platforms should be avoided where fault planes intersect the seabed. If certain circumstances dictate that structures must be located near areas of possible activity, the magnitude and time scale of the expected movement should be determined on the basis of geological studies for use in the bisection design.
A.4.9,4 Seafloor instability
The movement of the seafloor may be caused by ocean wave pressure, earthquakes, the deadweight of the soil, or a combination of these factors: weak and substructured sedimentary layers are most likely to move under the influence of waves when the wave pressure on the seafloor is very high, and may become unstable at very small slopes. Seafloor slopes that are previously stable under existing gravity and wave conditions may also be destroyed by the action of earthquake-induced forces.
Rapidly depositing strata (such as rapidly forming deltas), low-strength soils, the deadweight of the soil, and wave-induced pressure are all considered to be the determining factors in the process of continuous downslope movement of sedimentary layers. In these cases, important issues to be considered in platform design include the impact of large-scale movement of sedimentary strata in areas of strong wave pressure, downward movement of strata in areas not directly affected by wave roll and seafloor interaction, and the impact of sediment scouring and/or accumulation on platform performance. The scope of the field investigation of areas where seafloor instability may occur should focus on the identification of the geological stability characteristics of the surrounding area and the determination of the engineering properties of the soil necessary to simulate and assess seafloor movement. Analytical estimates of soil movement with depth below the mudline, combined with the engineering properties of the soil, can be used to determine the external forces expected to act on the platform components. Geological studies using historical oceanographic bathymetric data may be useful in determining the sedimentation rate during the design service life of the platform.
A.4.9.5 Scour
Scour is the movement of seafloor soil caused by currents and waves. This scour may be a natural geological process or it may be caused by structural members disturbing the natural flow pattern near the bottom. It has been observed that the scour zone is composed of the following types: a) Local scour: such as piles and pile groups around the structural members. a) Scour of steep slopes, which can be seen in chute models. b) Overall scour: Due to the influence of the entire structure, the mutual influence of multiple structures or the mutual influence of waves, soil and structure, a large condensate scour basin is formed around the structure. c) Overall movement of the sea: In the absence of structure, movement of sand waves, sand ridges or sandbars may occur. This situation can cause the seabed to drop or accumulate. Scour can cause the foundation to lose vertical and horizontal support, resulting in excessive settlement of the submerged foundation and overloading of foundation components: Where scour is likely to occur, the cause and/or mitigation measures should be considered in the design. A.4.9.6 Shallow gas Gases present in the pore water near the surface of the seabed, whether biologically generated or mineral-generated, must be considered in foundation engineering. 100019--2002
is an important factor to consider. In addition to the danger of drilling when drilling holes and oil wells during on-site soil investigations, the impact of shallow gas on foundation engineering is very important. At the beginning of the design, attention should be paid to the assumptions about the impact of shallow gas on the characteristics of the soil and the geological process analysis model.
A,4.10 Site Investigation—Foundations
A.4.10.1 Purpose
In order to design structures of any size safely and economically, it is necessary to understand the conditions of the construction site. A field soil investigation should be carried out to determine the various soil layers and their corresponding physical and engineering properties. Previous site investigation data and field experience may allow the installation of new structures without further studies: Preliminary work of site investigation The purpose of the site investigation is to review existing geophysical and borehole data, which may be found in project archives, literature, or government archives. The purpose of the review is to identify potential problems and help plan the next steps in the site investigation. Bathymetric and any required geophysical surveys should be part of the site study and should usually be completed before drilling. These data should be combined with an understanding of the shallow geology of the area to determine the required foundation design parameters. The scope of the site study should include the entire depth and area that affects or is affected by the installation of foundation components: 4.4.10.2 Seabed Survey
The main purpose of geophysical surveys near the construction site is to provide information to evaluate the geology of the foundation soil and surrounding areas that affect the site. Geophysical data can reveal signs of collapse, debris, irregular or rough landforms, mud volcanoes, mud blocks, collapse features, sand waves, slips, faults, squeezed layers, erosion surfaces, bubbles in sedimentary layers, gas permeability, buried channels, and lateral variations in the thickness of the formation. If the soil borehole sampling data are reasonably consistent with the results of the seafloor survey, it is sometimes possible to map the regional extent of the shallow soils.
The geophysical equipment used includes: ① Seafloor shallow profiler (tuned sensor) to determine the depth and structural characteristics of near-surface sediments; ② Side-profile sonar to determine seafloor surface features; ③ Boom or micro-sparker to determine soil structure hundreds of feet below the seafloor; ① Sparkers, air guns, water guns or sleeve blasters to interpret deeper strata and correlate them with deep seismic data obtained from reserve studies. Shallow sampling along geophysical survey lines using gravity, piston, grab samplers or vibratory coring may be useful for calibrating shallow geological survey results and deepening the understanding of the underlying strata. For a more detailed description of common equipment used in seafloor surveys, see the relevant information. 4.4.10.3 Soil investigation and testing
Where practicable, the methods of sampling and testing should be determined after reviewing the results of the geophysical survey. The site investigation should include one or more core boreholes to provide samples suitable for engineering characterization tests and the means for conducting in situ tests. The number and depth of the boreholes will depend on the soil variability near the site and the platform configuration: For structures supported by piles, the foundation investigation should provide at least soil characterization data to determine the following parameters: interaxial tensile and compressive capacity of pillows; load-displacement characteristics of piles under axial and transverse loads; driveability of piles and bearing capacity of anti-sinking plates. The specific techniques for soil sampling and sample storage, field and laboratory testing procedures will depend on the requirements of the platform design and the need to characterize the geological processes that may affect the facility. For new platform concepts, deepwater applications, platforms located in areas where slope instability is likely to occur, and gravity foundation structures, the engineering procedures should be modified to provide the necessary data for appropriate soil-structure interaction and pile bearing capacity.
When conducting field investigations in new areas or areas known to contain carbonate materials, discriminative methods should be used to determine the presence of carbonate soils. In particular, carbonate deposits have a range of cohesive properties from loose to well-cohesive. Therefore, a survey program must be designed with appropriate flexibility in handling sampling, drilling soil samples and field tests. Qualitative tests must be carried out to determine the carbon content. The engineering properties of soils containing carbonate materials (generally exceeding 15% to 20% of the carbon content) in the soil profile will be significantly affected. For such soils, additional field and laboratory tests and process techniques are necessary. A.5 Selection of design conditions
The selection of platform design environmental conditions is the responsibility of the platform owner. As a guide, the recurrence period used in the design standard for offshore engineering should be several times the design life of the platform. Experience with the main platforms in the Gulf of Mexico tends to use a 1 plus 10-year sea condition design standard: This is only suitable for newly built and relocated platforms that are occupied during the design event, or for structures where the loss or serious damage of components will cause serious damage. For structures that are unoccupied or can be evacuated during the design event, and for structures with a design life shorter than the usual 20 years or where damage or serious damage to the structure will not cause serious damage, the design requirements may be reduced when designing or relocating. Hazard analysis can prove that it is appropriate to use a longer or shorter recurrence period as the design standard. However, for manned platforms, where unforeseen design events may occur, and/or when there are other restrictions, such as long flight distances and limited evacuation speed, consideration should be given to using a sea condition standard of not less than 10 years. Chapter 1 gives guidance on determining the 100-year nominal return period design criteria for floating platforms in the US-Han Sea area. The determination of other load criteria should be carried out in accordance with the procedures discussed in this chapter and Chapter C. When evaluating existing platforms, it is generally reasonable to use reduced standards. Recommendations for determining the sea conditions for evaluating existing platforms are given in Chapter R. Other factors that should be considered in selecting design criteria are: a) the intended use of the platform; b) the life of the platform; c) the time and duration of construction and installation, and the load conditions of the operating environment; d) the probability of personnel living on the platform under extreme design load conditions; e) the possibility of harmful pollution; f) the requirements of the current authorities; and d) the predicted sea conditions under specific environmental conditions and operating conditions. h) the probability of occurrence of extreme marine environmental loads after considering the combined frequency of occurrence (magnitude and direction) of extreme wind, wave and current;
i) the probability of occurrence of extreme geothermal loads:
) the probability of occurrence of extreme ice loads.
4.6 Platform reuse
Existing platforms may be moved to a new area for continued installation and use. When considering reuse, the platform must be inspected to ensure that the platform is in (or can be returned to) a usable state. In addition, a new analysis and evaluation must be conducted on the expected use, condition and loading conditions of the platform at the new location. Generally, the requirements for such inspection, re-evaluation and repair or improvement should follow the requirements for new platforms in this practice. The steps and provisions for the reuse of platforms are described in Chapter P. Other special provisions for the reuse of platforms are described in Chapter P. A.7 Exposure classification
Structures can be classified according to different exposure levels, and the standards for the design of new platforms and the assessment of existing platforms can be determined accordingly to make them compatible with their intended functions
The levels can be determined by considering life safety and the consequences of failure. Life safety is considered based on the most likely environmental events expected, that is, the situations expected to occur when people are on the platform. The accident consequence analysis should pay attention to the factors listed in Section A.5 and the discussion in the notes to this section. These factors include the expected owner's losses (repair and replacement of platform equipment, production losses, environmental cleanup), losses to other operators (production losses caused by outlet pipelines, industrial and political losses, life safety, etc.). The classification of the platform is:
11=occupied—no evacuation
1.-2-occupied—evacuate
1.-3=unoccupied
The classification of the consequences of failure is:
L·1=severe consequence of failure
L-2=moderate consequence of failure
1.-3=minor consequence of failure
SY/T10009—2002
The classification used for platform classification is more restrictive than the life safety or consequence of failure classification. Due to changes in factors affecting life safety and consequence of failure, the classification of the platform may change during the life of the structure. A.7.1 Life safety
The determination of the appropriate level of life safety is based on the following provisions: A.7,1a 1.-1 Inhabited-non-evacuated
Inhabited-non-evacuated means that there are people living on the platform all the time and before the design environmental event occurs, either no plans to evacuate or evacuation is impractical
A.7.1h-2 Inhabited-evacuated
Inhabited-evacuated means that there are people usually living on the platform except during the forecast design environmental event period. As long as there is an evacuation plan before the design environment event and there is sufficient time to safely evacuate all occupants from the platform, the platform can be classified as an "occupied platform-evacuation platform" when grading.
A.7.1cL-3 Uninhabited
An occupied platform refers to a platform that is rarely occupied, or is neither an occupied evacuation nor an occupied evacuation platform. In some cases, platforms that are occasionally occupied are classified as uninhabited platforms (see Note A.7.1c). A.7.2 Consequences of Failure
As mentioned above, the consequences of failure should generally include consideration of the expected losses to the owner, other operators and the industry. The following description of the relevant factors can be used as a basic principle for determining the corresponding level of failure consequences. A.7.2aL-1 Severe Consequences
The Severe Consequences Level refers to important platforms and/or those platforms where oil and gas leaks may occur if they fail. In addition, it also includes platforms where it is unlikely that oil and gas production will be interrupted before the design event occurs (for example, in areas with frequent seismic activity). Platforms with important oil pipelines (see Note A.7.2-Pipelines) and/or intermittent oil storage facilities should also be classified as severe consequences. A.7.2L-2 Medium Consequences
The Medium Consequences Level refers to platforms that will be shut down during the design event. All platforms that will self-flow in the event of a platform failure must be equipped with a functional The underwater safety valves shall be manufactured and tested in accordance with the applicable standards of the People's Republic of China and the oil and gas industry. Crude oil is limited to storage in processing tanks and buffer tanks. The minor failure consequence level refers to a small platform that stops production when a design event occurs. All oil wells that can self-break in the event of platform failure must be equipped with fully functional underwater safety valves. The underwater safety valves shall be manufactured and tested in accordance with the applicable standards of the People's Republic of China and the oil and gas industry. These platforms may be equipped with production separation facilities and a small amount of internal pipelines. Crude oil is limited to storage in processing tanks. A,8 Platform Assessment
During the life of a platform an assessment may be required to determine its suitability. This process may be due to changes in the platform's use, such as adjustments to staffing and loading; changes in the platform's condition, such as damage or degradation; or re-evaluation of environmental loads or foundation strength. 1 Industry practice generally recognizes that older existing structures may not meet current design standards. However, risk assessment criteria that take into account the platform's use, location, and the consequences of failure have demonstrated that many platforms have adequate structural performance in these permitted conditions. Recommendations for establishing reduced standards for assessing the safety of life and the consequences of failure considered, as well as recommendations for assessment procedures, are given in Chapter R. These appropriate provisions are not intended to override normal design practice requirements for new platforms. For platforms not more than 5 years old, the reduced environmental standards in Chapter R cannot be used to justify platform modifications and additional components that will result in significantly increased loads on the platform:
A.9 Safety considerations
The safety of life and property depends on the ability of the platform to withstand its design loads and withstand the environmental conditions that may occur. Apart from this general principle
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