SY/T 10040-2002 Recommended practices for the design and analysis of positioning systems for floating structures
Some standard content:
ICS 75.180.10
Registration No.: 10483-2002
Petroleum and Natural Gas Industry Standard of the People's Republic of ChinaSY/T 100402002
Recommended practice for design and analysis ofstationkeeping systems for floating structures2002-05-28Published
National Economic and Trade Commission
2002-08-01Implementation
API Foreword
API Environmental Protection Mission and Environmental Protection Guiding PrinciplesSpecial Notes
1 Scope+***
2 Basic considerations
2.1 Introduction to positioning systems
2.2 Differences between permanent and movable mooring systems2.3 Design considerations
3 Mooring components
3.1 Mooring lines
3.2 Winch equipment
3.3 Mooring system·
4 Environmental considerations
4.1 Environmental conditions
Environmental data·
Wave roll·
Currents·
4.6 Water depth and tides
Soil conditions·
4.8 Large Air icing·
Marine objects
5 Environmental forces and floating motions
Basic considerations·
Guide to the estimation of environmental forces and floating body motions
Simplified methods·
Design criteria
Basic considerations
Displacement...
Mooring line tension,
6.4 Peak statistics
Mooring line length
Holding force of anchor system
Thrust aid mooring
Fatigue life·
Mooring analysis
Basic considerations
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SY/T 100402002
Static and dynamic analysis
Transient analysis·
Thruster assisted mooring analysis
7.5 Fatigue analysis
8 Model test
Basic considerations
Single anchor leg mooring system
Basic considerations·
Special design conditions
Extreme response analysis·
Design criteria for extreme response
Fatigue Analysis…
Special Design Considerations
10 Dynamic Positioning System
Basic Considerations
Basic Concepts and Main Factors
Design and Analysis
101.4 Operation of Dynamic Positioning System
11 Design Example
11.1 Extreme Response Analysis Example
11.2 Fatigue Analysis Example
Appendix A (Informative) Simplified Method for Estimating Environmental Forces and Motions of Floating Bodies Appendix B (Informative) Notes on the Performance Evaluation of Drag Anchors Appendix C (Informative)
Appendix L (Informative)
Extended Mooring System
Determination of Effective Thrust
References
Lateral Mooring of Tension Leg Platform
Typical External Turret Mooring Arrangement
Typical Internal Turret Mooring Arrangement…
Various Turret /Riser system
Catechuen Anchor Leg Mooring (CALM) system with nylon cableFigure 7
Catechuen Anchor Leg Mooring (CALM) system with fixed jibCatechuen Anchor Leg Mooring (CALM) system with flexible jib·..Single Anchor Leg Mooring (SALM) system with simple riser and jibSingle Anchor Leg Mooring (SALM) system with chain riser and nylon cableDynamic positioning
Different wire rope structures
Submersible Water floating structure
Winching system using linear winch and bending frameInstallation of caisson foundation (suction cone)
US Navy Flash rocket burial anchor
Wave height/wave period relationship
Drag burial anchor
Figure 19 Grip of anchor system in soft clay
Grip of anchor system in sandy beach
Fatigue design binding line
System dynamic analysis
Main components of dynamic positioning system
Control loop of dynamic positioning system
Three-axis controller and thruster deployment logic·position sensing system
Operation principle of short baseline system (SIBS)
Acoustic wave phase relationship
System execution process of long baseline system
Tension rope system
Riser angle reference system (ARARS)
Fixed automatic navigation satellite communication system (SIARS) Schematic diagram of compass in FIX
Schematic diagram of swing vertical reference sensor
Dispersed propeller type thruster·
Typical diverter propeller,
Typical retractable thruster structure·
Typical thruster layout
Basic composition of power system
Generation of reliability measurement of dynamic positioning system at different levels Rose diagram of dynamic positioning holding capability·
Mooring system layout Position
Choice of input motion
Mooring system and environmental force direction
Semi-submersible has a smooth surface and the current resistance coefficient of the components. Wave force distribution
Drilling ship's wave drift force and motion in the face of waves (1) Drilling ship's wave drift force and motion in the face of waves (Ⅱ) Drilling ship's wave drift force and motion in the face of waves (Ⅲ) Drilling ship's oblique waves and longitudinal wave drift force and motion! Ⅱ Drilling ship oblique wave Ⅱ Wave drift force and motion with longitudinal wave (Ⅱ) Wave drift force and motion of stationary ship oblique wave and transverse wave (1) Figure A.9
Drilling ship oblique wave and transverse wave drift force and motion (Ⅱ) Drilling ship oblique wave Ⅱ Wave drift force and motion with transverse wave (Ⅲ) Drilling ship transverse wave drift force and motion (I) Drilling ship transverse wave drift force and motion () Drilling ship transverse wave drift force and motion (sub) Semi-submersible head wave wave drift force and motion semi-submersible oblique wave SY/T 10040—2002
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Figure A.17 Wave drift forces and motions of semi-submersibles in beam waves Figure B.1 Effects of cyclic loading
Figure B.2 Effects of anchor immersion
Figure B.3 Towing distance in mud as a percentage of holding force Figure C.1
Propeller thrust—dispersed propeller
Propeller thrust
Figure C.3 Lateral force—
Guide propeller
—Tunnel thruster
Analysis conditions and corresponding analysis methods
Table 2 Tension limits and safety factors for various failure conditions and analysis methods Table 3 Safety factors for towing electric anchors
Table 4 Friction coefficient (f)
Table 5 Guidelines for mooring with thrusters
Table 6 Values of M and K in the discrete equations of the T-N curve Table 7 Bending-tension fatigue life of wire ropes expressed as a percentage of tension-tension fatigue life Example of reliability analysis of a drilling ship
Table 9 Environmental forces when the ship is pointing at 020 degrees Table 10
Complex response amplitude of fairlead motion (RAO) tension spectrum ...
Environmental conditions, average loads and low-frequency motions in the analysis direction Damage to the cable
Damage of anchor chain
Annual fatigue damage with environmental variation
Wind shape factor
Wind height factor
Wind loss factor
Estimated maximum anchor tip penetration depth for certain types of towing anchorsInflow velocity correction factor
Thrust loss under reverse conditions
SY/T10040—2002
This standard is equivalent to the American Petroleum Institute's "Recommended Practice for Irsign and Aunalysis of Statiurikeeping Systems for Flont-ing Strurtures" (1996 edition), namely API RP 2sK API Recommended Practice for Irsign and Aunalysis of Statiurikeeping Systems for Flont-ing Strurtures) (1996).
In the translation of this standard, the data or quantitative calculation methods of environmental conditions such as wind, waves, currents, ice, temperature, and geothermal energy still use the data and quantitative calculation methods in the original standard. Regarding the measurement units, the metric unit is used as the first, that is, the metric unit value is in front, and the corresponding value of the imperial unit is marked in brackets afterwards: In order not to change the shape characteristics of the original formulas, curves, constants and coefficients, all those using imperial units still use imperial units:
Appendix A, Appendix C and Appendix D of this standard are all informative appendices. This standard is proposed and managed by China National Offshore Oil Corporation. Drafting unit of this standard: Tianjin Yinxu Technology Development Center. The main drafters of this standard: Tian Shutang, Wang Zhongmin, and Wang Penglai. W
SY/T10040—2002
API Foreword
In this recommended practice, the parts marked with vertical lines are the revisions made to the previous version of API. Note that all chapters, paragraphs, figures and tables have been renumbered:
The ownership of this recommended practice belongs to the API Offshore Structures Section. API publications are available to anyone who wishes to use them. Every effort has been made to ensure the accuracy and reliability of the information in the publication. However, the Society makes no representations, warranties or guarantees regarding any issues related to this publication, and expressly disclaims any responsibility or legal liability for loss or damage caused by the use of this publication. At the same time, no responsibility or legal liability is assumed for any violation of federal, state or municipal laws that may conflict with this publication. Suggestions for revisions are welcome and should be provided directly to the Director, Exploration and Production Division, American Petroleum Institute, Washington, DC 200051201. Street NW
This standard is effective from the date indicated on the cover, but can also be used voluntarily from the date of publication. API Environmental Protection Mission and Environmental Protection Guidelines SY/T10040—2002
From the long-term development trend, one of the most important issues affecting the survival of the petroleum industry is the public's concern for the environment. In view of this development trend, the members of the American Petroleum Institute (API) have established a positive and forward-looking environmental strategy called the Contemporary Environmental Partnership Action Strategy (SEP). The goal of this action plan is to respond to public concerns by improving the environment, health and safety of the petroleum industry, record these improvements in a literary way, and communicate with the public. The basis of this action strategy (STEP) is the American Petroleum Institute (API) Environmental Protection Mission and Environmental Protection Guidelines. API standards will promote people to engage in good engineering design and operating practices and are an important means of implementing API's STEP. API Environmental Protection Mission and Guiding Principles The members of the American Petroleum Institute have been working tirelessly to improve the coordination between operations and the environment while developing energy economically and providing consumers with high-quality products and services. These members recognize that while protecting the health and safety of their employees and the public, they have the responsibility to effectively meet the needs of society and work with the public, government and others to develop and use natural resources in a way that protects the environment. To meet these requirements, API members guarantee to regulate their business conduct in accordance with the following principles: 1. Understand and respond to public concerns about their raw materials, products and operations. 2. Operate their plants and facilities and manage their raw materials and products in a way that protects the environment and protects the health and safety of their employees and the public. 3. Give priority to safety, health and environmental issues when designing and developing new products and processes. 4. Inform relevant officials, employees, customers and the public of any significant safety, health and environmental hazards and possible protective measures promptly. 5. Ask customers, carriers and others for advice on the safe use, transportation and disposal of their raw materials, products and wastes. · Develop and exploit natural resources economically and use energy efficiently to protect these resources. · Expand knowledge by conducting and supporting research on the safety, health and environmental effects of its raw materials, products, processes and wastes. · Accountable to relevant departments to reduce overall air emissions and waste generation. · Work with other relevant departments to solve problems caused by the handling and disposal of hazardous substances in operations. · Participate in the formulation of laws, regulations and standards for the protection of public, workplace and environmental safety by government and other parties. · Promote these principles and practices through mutual learning and assistance with other units that produce, bury, use, transport or dispose of similar raw materials, petroleum products and wastes:
SY/T 100402002
Special Notes
The issues discussed in API publications are necessarily general: for some specific situations, local, state and federal laws and regulations should be consulted again.
API assumes no obligation to employers, manufacturers, or suppliers to forewarn, properly train, and equip their employees and other participants in matters concerning health and safety risks and prevention; nor does API assume any responsibility for employers, manufacturers, and suppliers under local, state, and federal laws. Information on the safety and health risks and appropriate prevention of specific materials should be obtained from the employer, the manufacturer or supplier of the material, or from the material safety data sheet. No right to make, sell, or use any method, apparatus, or product covered by a patent is implied or contemplated in any AP publication: nothing contained in an AP publication can be used as a warranty against any liability for infringement of a patent.
In general, API standards are reviewed, revised, or revoked at least every five years. Sometimes this review period can be extended for two days at a time. After five years of publication as an operational standard, or after a further period of time, this publication shall be deemed ineffective. The availability of this publication may be obtained from the API Administration [telephone (202) 682-8000]: API Publications and Materials API is published annually and revised quarterly. API headquarters is located at 1220 L Street, NW Washington, DC 20005. The above documents are produced in accordance with API standardization procedures that ensure timely notification and participation in the development process. They are designated as individual API standards. Questions concerning the interpretation of the contents of this standard or the procedures for the production of standards should be directed to the Editorial Director (see bottom page of this document): American Petroleum Institute, 1220 L Street, Washington, DC 28005. Requests for reproduction or translation of any material published by API should also be addressed to the Director.
These API standards are published to promote the use of proven, well-established process design and operational practices. API standards are not intended to preclude the use of judgment as to when and where to apply them in the design of safe and reliable processes. The formalization and publication of API standards is not intended in any way to prevent anyone from adopting any other practice. Any manufacturer whose designs and materials are marked in accordance with the marking requirements of an API standard assumes sole responsibility for complying with all the requirements of that standard. API makes no representation, warranty, or guarantee that such products actually conform to the applicable API standards. All rights reserved: No part of this document may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher: API Publications Services: 1220 Main Street, Washington, DC 20005. Copyright @ 1996 American Petroleum Institute
1 Scope
SY/T 10040-202
Recommended Practice for Design and Analysis of Positioning Systems for Floating Structures The purpose of this standard is to present a reasonable approach to the analysis, design or evaluation of mooring systems for use with floating structures. This approach provides a systematic analytical tool by which the availability and safety of mooring systems can be determined, given an understanding of the environmental conditions in a particular area, the characteristics of the structure in a moored position, and other factors. This standard also includes some design guidelines for dynamic positioning systems. Floating structure and mooring technology is rapidly developing. In areas where the committee believes that sufficient information is available, specific and detailed recommendations are made. In other areas, only general statements are given that should be considered in response to specific issues. Designers are encouraged to use all research results. As marine technology continues to develop, this recommended practice will be revised, and it is hoped that the general statements contained herein will be gradually replaced by detailed suggestions: 2 Basic Considerations
2.1 Introduction to positioning systems
The positioning system of a floating structure can be either a single point mooring or an extended mooring. Ship-type installations tend to use single point mooring, while semi-submersible installations tend to use extended mooring: The third type of positioning system is dynamic positioning (DP): Dynamic positioning can be used as an independent power source for positioning, or to assist a total chain mooring. Dynamic positioning can be used for both turbines and semi-submersible systems.
2.1.1 Extended mooring
Figure 1 is a schematic diagram of a catenary extended semi-submersible mooring, which is a common mooring technology used in floating drilling and production operations. For floating production applications, extended mooring is mainly used for semi-submersible installations. Because the environmental forces acting on semi-submersible installations are not very sensitive to direction, the extended mooring system can be designed to keep the installation in a position that is independent of the direction of the environmental forces. However, the system can also be used for ship-type installations that are more sensitive to the direction of environmental forces: This mooring can be anchor chain type or steel cable type. Synthetic fiber rope or a combination of all three. Either universal drag pin or anchor can be used for the mooring line termination: For semi-floating production systems, spread mooring has certain advantages, because it fixes the position of the unit, and can be used to drill and complete the subsea wellhead just below the unit. This is also true for well repair operations: On the other hand, the mooring extension range of the spread mooring system is quite large (on the order of several feet): staggered and suspended mooring lines are within the scope of this extension, which must be considered when installing and repairing pipelines, risers or other subsea equipment. Spread mooring combined with vertical mooring cables (see Figure 2) for fixed tension leg platform (TIP) F, enhances the operability and reliability of the basic TIP concept: This spread mooring allows the surface vessel to be adjusted in a controlled manner and provides an independent parallel load path to resist the lateral environment. This concept can be used to deliver horizontal drilling tools and production equipment skids into position and connect to the seabed structure. Otherwise, these equipment blocks must be brought to the appropriate position using methods such as guide ropes, thrusters or towing the derrick on a surface vessel. The overall shape and design of this extended mooring are very similar to the extended mooring system used for semi-submersible floating production systems. 2.1.2 Single-point mooring
Single-point mooring is mainly used for oil tankers. This system allows the oil tanker to change direction like a weather vane. In order to minimize the environmental loads acting on the oil tanker, it is necessary to make the bow of the oil tanker face the main control direction of environmental conditions. The design of single-point mooring systems varies, but their functions are basically the same. The single-point mooring is integrated with the production riser and the oil tanker. Typical single-point mooring systems are described as follows: |SY/T 10040—2002
head buoy
anchor head buffer
tether or fleece plate
fairlead
mooring wave source
drilling and production equipment
wire transmission and anchor chain
lateral mooring rope
well completion production section
extended mooring system
a buoyant superstructure
, submersible mid-link float
mooring steel bar bundle
drilling and tool lowering work
seabed foundation
Figure 2 Lateral mooring of tension platform
tow cable
2.1.2.1 turret mooring
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Turret mooring system is defined as a system of anchored chained legs connected to a turret. The turret forms the basic component of the moored system: the turret has bearings that allow the system to rotate around the anchor. With appropriate reinforcement measures, the turret can be mounted on the outside of the hull or hull section (see Figure 3), or inside the ship (see Figure 4), with the chain either above or below the waterline: the turret can also be integrated with a vertical riser system connected to the hull or hull section (or inside) by some mechanism (frames for axial joints, mountain joints or anchor chain connections). The base of the turret can be weighted by adding weight inside the turret or by being suspended under the riser (balanced). The connection method between the above-mentioned turret and the hull affects the performance of the mooring system. The structure of the riser may include components such as steel pipe columns, chains or wire cables, and the diameter and length can vary greatly. The relative position of the chain plate and the turret also varies according to the design. Figure 5 shows several turret design types provided by the industry.
2.1.2.2 Catenary Anchor Leg Mooring (CALM)
A catenary leg mooring system consists of a large buoy supporting a number of anchor legs (see Figure 6) anchored to the seabed. A pipe or outlet pipe extending from the seabed is connected to the bottom of the CALM buoy. Some mooring systems use a nylon cable, usually a synthetic fiber cable, between the buoy and the tanker: Because the response of the CALM buoy under the influence of waves is completely different from that of the tanker, the system has a limited ability to withstand environmental conditions and when sea conditions reach a certain level, the tanker must be released. To overcome this limitation, some newer designs use a flexible structural connecting arm with a relatively large axis to connect the ship to the top of the buoy (see Figure 7). This flexible connection virtually eliminates relative horizontal movement between the buoy and the tanker: Figure 8 shows a recently developed mooring system with a flexible arm. A system that uses anchor chains to connect the vessel to a buoyant arm with a flexible mooring connection. 2.1, 2.3 Single Anchor Leg Mooring [SAI.M]
This system uses a vertical riser system that is fairly buoyant near the water surface (sometimes at the surface) and is secured to a tensioned riser. The system generally uses a section of tubular column with the riser articulated to a fixed arm (see Figure 9), or may use a chain riser with a flexible mooring connection (see Figure 10), with the buoyancy of the riser clawed at the top of the riser acting like an inverted pendulum. When the system moves horizontally, the pendulum action returns the riser to the vertical position. The tanker is either fixed to the top of the single anchor leg mooring (SALM) buoy by a flexible mooring line discussed in the description of catenary anchor mooring (CALM) or by a rigid arm: this riser base is usually fixed to the pile by a U-joint. or on weighted concrete blocks or steel structures on the seabed. In deep water, riser systems often have mid-span articulated joints. 2.1.3 Dynamic Positioning
Dynamic positioning (see Figure 11) can be used as a single positioning source or to assist a catenary mooring system. Dynamic positioning usually consists of an acoustic positioning reference system and computer-controlled thrusters around the hull. Dynamic positioning can be used in conjunction with a system called DP-assisted mooring (or thruster-assisted system if the thrusters are manually controlled). Dynamic positioning is particularly suitable for vessels that are scheduled to frequently enter and exit the site, such as oil and gas and extended testing systems.
2.2 The difference between permanent and movable mooring systems Permanent systems are usually used for production operations that are designed to last longer. For example, the system of a floating production system (FPS) is a permanent system because the typical design life of a floating production system mooring is in excess of 10 years. Movable systems Examples of mobile moorings where the mooring is often for a short period of time include mobile offshore drilling units (MODLs) and auxiliary vessels such as floating docks, drilling supply vessels and watch boats moored to other platforms in the vicinity. For operations where the design life is only a few years, the distinction between mobile and permanent may not be clear. In such cases, the user should make a judgment based on the risk of encountering harsh environments and the consequences of a minor mooring failure. As discussed below, the distinction between permanent and mobile moorings is significant. The following discussion can be used as a guide to determine the category (permanent or mobile) to which a floating structure belongs:
2.2.1 Mooring Types
A mobile floating platform will usually have the option of being equipped with an extended mooring, internal turret mooring or dynamic positioning system, while a permanent floating platform will have more mooring design options because it is not normally moved. 31 Extended mooring
Figure 1 is a schematic diagram of a catenary extended semi-submersible mooring, which is a common mooring technology used for floating drilling and production operations. For floating production applications, extended mooring is mainly used for semi-submersible devices. Because the environmental forces acting on semi-submersible devices are not very sensitive to direction, the extended mooring system can be designed to keep the device in a position independent of the direction of the environmental forces. However, the system can also be used for ship-type devices that are more sensitive to the direction of environmental forces: this mooring can be anchor chain, steel cable, synthetic fiber cable or a combination of these three methods. Either a common drag pin or anchor can be used as the mooring line termination: For semi-floating production systems, spread mooring has certain advantages. Since it fixes the position of the unit, drilling and completion of the subsea wellhead just below the unit can be carried out. This is also true for well repair operations. On the other hand, the mooring extension of the spread mooring system is quite large (on the order of several feet): the staggered and suspended mooring lines are within the scope of this extension, which must be considered when installing and repairing pipelines, risers or other subsea equipment. Spread mooring combined with the vertical mooring cables of the fixed tension leg platform (TIP) F (see Figure 2) enhances the operability and reliability of the basic TIP concept: this spread mooring allows the surface vessel to be adjusted in a controlled manner and provides an independent parallel load path to resist the lateral environment. This concept can be used to deliver horizontal drilling tools and production equipment skids into position and connect to the seabed structure. Otherwise, these equipment blocks must be brought to the appropriate position using methods such as guide ropes, thrusters or towing the derrick on a surface vessel. The overall shape and design of this extended mooring are very similar to the extended mooring system used for semi-submersible floating production systems. 2.1.2 Single-point mooring
Single-point mooring is mainly used for oil tankers. This system allows the oil tanker to change direction like a weather vane. In order to minimize the environmental loads acting on the oil tanker, it is necessary to make the bow of the oil tanker face the main control direction of environmental conditions. The design of single-point mooring systems varies, but their functions are basically the same. The single-point mooring is integrated with the production riser and the oil tanker. Typical single-point mooring systems are described as follows: |SY/T 10040—2002
head buoy
anchor head buffer
tether or fleece plate
fairlead
mooring wave source
drilling and production equipment
wire transmission and anchor chain
lateral mooring rope
well completion production section
extended mooring system
a buoyant superstructure
, submersible mid-link float
mooring steel bar bundle
drilling and tool lowering work
seabed foundation
Figure 2 Lateral mooring of tension platform
tow cable
2.1.2.1 turret mooring
SY/T 100402002
Turret mooring system is defined as a system of anchored chained legs connected to a turret. The turret forms the basic component of the moored system: the turret has bearings that allow the system to rotate around the anchor. With appropriate reinforcement measures, the turret can be mounted on the outside of the hull or hull section (see Figure 3), or inside the ship (see Figure 4), with the chain either above or below the waterline: the turret can also be integrated with a vertical riser system connected to the hull or hull section (or inside) by some mechanism (frames for axial joints, mountain joints or anchor chain connections). The base of the turret can be weighted by adding weight inside the turret or by being suspended under the riser (balanced). The connection method between the above-mentioned turret and the hull affects the performance of the mooring system. The structure of the riser may include components such as steel pipe columns, chains or wire cables, and the diameter and length can vary greatly. The relative position of the chain plate and the turret also varies according to the design. Figure 5 shows several turret design types provided by the industry.
2.1.2.2 Catenary Anchor Leg Mooring (CALM)
A catenary leg mooring system consists of a large buoy supporting a number of anchor legs (see Figure 6) anchored to the seabed. A pipe or outlet pipe extending from the seabed is connected to the bottom of the CALM buoy. Some mooring systems use a nylon cable, usually a synthetic fiber cable, between the buoy and the tanker: Because the response of the CALM buoy under the influence of waves is completely different from that of the tanker, the system has a limited ability to withstand environmental conditions and when sea conditions reach a certain level, the tanker must be released. To overcome this limitation, some newer designs use a flexible structural connecting arm with a relatively large axis to connect the ship to the top of the buoy (see Figure 7). This flexible connection virtually eliminates relative horizontal movement between the buoy and the tanker: Figure 8 shows a recently developed mooring system with a flexible arm. A system that uses anchor chains to connect the vessel to a buoyant arm with a flexible mooring connection. 2.1, 2.3 Single Anchor Leg Mooring [SAI.M]
This system uses a vertical riser system that is fairly buoyant near the water surface (sometimes at the surface) and is secured to a tensioned riser. The system generally uses a section of tubular column with the riser articulated to a fixed arm (see Figure 9), or may use a chain riser with a flexible mooring connection (see Figure 10), with the buoyancy of the riser clawed at the top of the riser acting like an inverted pendulum. When the system moves horizontally, the pendulum action returns the riser to the vertical position. The tanker is either fixed to the top of the single anchor leg mooring (SALM) buoy by a flexible mooring line discussed in the description of catenary anchor mooring (CALM) or by a rigid arm: this riser base is usually fixed to the pile by a U-joint. or on weighted concrete blocks or steel structures on the seabed. In deep water, riser systems often have mid-span articulated joints. 2.1.3 Dynamic Positioning
Dynamic positioning (see Figure 11) can be used as a single positioning source or to assist a catenary mooring system. Dynamic positioning usually consists of an acoustic positioning reference system and computer-controlled thrusters around the hull. Dynamic positioning can be used in conjunction with a system called DP-assisted mooring (or thruster-assisted system if the thrusters are manually controlled). Dynamic positioning is particularly suitable for vessels that are scheduled to frequently enter and exit the site, such as oil and gas and extended testing systems.
2.2 The difference between permanent and movable mooring systems Permanent systems are usually used for production operations that are designed to last longer. For example, the system of a floating production system (FPS) is a permanent system because the typical design life of a floating production system mooring is in excess of 10 years. Movable systems Examples of mobile moorings where the mooring is often for a short period of time include mobile offshore drilling units (MODLs) and auxiliary vessels such as floating docks, drilling supply vessels and watch boats moored to other platforms in the vicinity. For operations where the design life is only a few years, the distinction between mobile and permanent may not be clear. In such cases, the user should make a judgment based on the risk of encountering harsh environments and the consequences of a minor mooring failure. As discussed below, the distinction between permanent and mobile moorings is significant. The following discussion can be used as a guide to determine the category (permanent or mobile) to which a floating structure belongs:
2.2.1 Mooring Types
A mobile floating platform will usually have the option of being equipped with an extended mooring, internal turret mooring or dynamic positioning system, while a permanent floating platform will have more mooring design options because it is not normally moved. 31 Extended mooring
Figure 1 is a schematic diagram of a catenary extended semi-submersible mooring, which is a common mooring technology used for floating drilling and production operations. For floating production applications, extended mooring is mainly used for semi-submersible devices. Because the environmental forces acting on semi-submersible devices are not very sensitive to direction, the extended mooring system can be designed to keep the device in a position independent of the direction of the environmental forces. However, the system can also be used for ship-type devices that are more sensitive to the direction of environmental forces: this mooring can be anchor chain, steel cable, synthetic fiber cable or a combination of these three methods. Either a common drag pin or anchor can be used as the mooring line termination: For semi-floating production systems, spread mooring has certain advantages. Since it fixes the position of the unit, drilling and completion of the subsea wellhead just below the unit can be carried out. This is also true for well repair operations. On the other hand, the mooring extension of the spread mooring system is quite large (on the order of several feet): the staggered and suspended mooring lines are within the scope of this extension, which must be considered when installing and repairing pipelines, risers or other subsea equipment. Spread mooring combined with the vertical mooring cables of the fixed tension leg platform (TIP) F (see Figure 2) enhances the operability and reliability of the basic TIP concept: this spread mooring allows the surface vessel to be adjusted in a controlled manner and provides an independent parallel load path to resist the lateral environment. This concept can be used to deliver horizontal drilling tools and production equipment skids into position and connect to the seabed structure. Otherwise, these equipment blocks must be brought to the appropriate position using methods such as guide ropes, thrusters or towing the derrick on a surface vessel. The overall shape and design of this extended mooring are very similar to the extended mooring system used for semi-submersible floating production systems. 2.1.2 Single-point mooring
Single-point mooring is mainly used for oil tankers. This system allows the oil tanker to change direction like a weather vane. In order to minimize the environmental loads acting on the oil tanker, it is necessary to make the bow of the oil tanker face the main control direction of environmental conditions. The design of single-point mooring systems varies, but their functions are basically the same. The single-point mooring is integrated with the production riser and the oil tanker. Typical single-point mooring systems are described as follows: |SY/T 10040—2002
head buoy
anchor head buffer
tether or fleece plate
fairleadbZxz.net
mooring wave source
drilling and production equipment
wire transmission and anchor chain
lateral mooring rope
well completion production section
extended mooring system
a buoyant superstructure
, submersible mid-link float
mooring steel bar bundle
drilling and tool lowering work
seabed foundation
Figure 2 Lateral mooring of tension platform
tow cable
2.1.2.1 turret mooring
SY/T 100402002
Turret mooring system is defined as a system of anchored chained legs connected to a turret. The turret forms the basic component of the moored system: the turret has bearings that allow the system to rotate around the anchor. With appropriate reinforcement measures, the turret can be mounted on the outside of the hull or hull section (see Figure 3), or inside the ship (see Figure 4), with the chain either above or below the waterline: the turret can also be integrated with a vertical riser system connected to the hull or hull section (or inside) by some mechanism (frames for axial joints, mountain joints or anchor chain connections). The base of the turret can be weighted by adding weight inside the turret or by being suspended under the riser (balanced). The connection method between the above-mentioned turret and the hull affects the performance of the mooring system. The structure of the riser may include components such as steel pipe columns, chains or wire cables, and the diameter and length can vary greatly. The relative position of the chain plate and the turret also varies according to the design. Figure 5 shows several turret design types provided by the industry.
2.1.2.2 Catenary Anchor Leg Mooring (CALM)
A catenary leg mooring system consists of a large buoy supporting a number of anchor legs (see Figure 6) anchored to the seabed. A pipe or outlet pipe extending from the seabed is connected to the bottom of the CALM buoy. Some mooring systems use a nylon cable, usually a synthetic fiber cable, between the buoy and the tanker: Because the response of the CALM buoy under the influence of waves is completely different from that of the tanker, the system has a limited ability to withstand environmental conditions and when sea conditions reach a certain level, the tanker must be released. To overcome this limitation, some newer designs use a flexible structural connecting arm with a relatively large axis to connect the ship to the top of the buoy (see Figure 7). This flexible connection virtually eliminates relative horizontal movement between the buoy and the tanker: Figure 8 shows a recently developed mooring system with a flexible arm. A system that uses anchor chains to connect the vessel to a buoyant arm with a flexible mooring connection. 2.1, 2.3 Single Anchor Leg Mooring [SAI.M]
This system uses a vertical riser system that is fairly buoyant near the water surface (sometimes at the surface) and is secured to a tensioned riser. The system generally uses a section of tubular column with the riser articulated to a fixed arm (see Figure 9), or may use a chain riser with a flexible mooring connection (see Figure 10), with the buoyancy of the riser clawed at the top of the riser acting like an inverted pendulum. When the system moves horizontally, the pendulum action returns the riser to the vertical position. The tanker is either fixed to the top of the single anchor leg mooring (SALM) buoy by a flexible mooring line discussed in the description of catenary anchor mooring (CALM) or by a rigid arm: this riser base is usually fixed to the pile by a U-joint. or on weighted concrete blocks or steel structures on the seabed. In deep water, riser systems often have mid-span articulated joints. 2.1.3 Dynamic Positioning
Dynamic positioning (see Figure 11) can be used as a single positioning source or to assist a catenary mooring system. Dynamic positioning usually consists of an acoustic positioning reference system and computer-controlled thrusters around the hull. Dynamic positioning can be used in conjunction with a system called DP-assisted mooring (or thruster-assisted system if the thrusters are manually controlled). Dynamic positioning is particularly suitable for vessels that are scheduled to frequently enter and exit the site, such as oil and gas and extended testing systems.
2.2 The difference between permanent and movable mooring systems Permanent systems are usually used for production operations that are designed to last longer. For example, the system of a floating production system (FPS) is a permanent system because the typical design life of a floating production system mooring is in excess of 10 years. Movable systems Examples of mobile moorings where the mooring is often for a short period of time include mobile offshore drilling units (MODLs) and auxiliary vessels such as floating docks, drilling supply vessels and watch boats moored to other platforms in the vicinity. For operations where the design life is only a few years, the distinction between mobile and permanent may not be clear. In such cases, the user should make a judgment based on the risk of encountering harsh environments and the consequences of a minor mooring failure. As discussed below, the distinction between permanent and mobile moorings is significant. The following discussion can be used as a guide to determine the category (permanent or mobile) to which a floating structure belongs:
2.2.1 Mooring Types
A mobile floating platform will usually have the option of being equipped with an extended mooring, internal turret mooring or dynamic positioning system, while a permanent floating platform will have more mooring design options because it is not normally moved. 32 Single point mooring
Single point mooring is mainly used for oil tankers. This mooring system can make the oil tanker change direction like a weather vane. In order to minimize the environmental load acting on the oil tanker, it is necessary to make the bow of the oil tanker face the main control direction of environmental conditions. The design of single point mooring system varies, but their functions are basically the same. The single point mooring system is integrated with the production riser and the oil tanker. Typical single-point mooring systems are described as follows: |SY/T 10040—2002
head buoy
anchor head buffer
tether or fleece plate
fairlead
mooring wave source
drilling and production equipment
wire transmission and anchor chain
lateral mooring rope
well completion production section
extended mooring system
a buoyant superstructure
, submersible mid-link float
mooring steel bar bundle
drilling and tool lowering work
seabed foundation
Figure 2 Lateral mooring of tension platform
tow cable
2.1.2.1 turret mooring
SY/T 100402002
Turret mooring system is defined as a system of anchored chained legs connected to a turret. The turret forms the basic component of the moored system: the turret has bearings that allow the system to rotate around the anchor. With appropriate reinforcement measures, the turret can be mounted on the outside of the hull or hull section (see Figure 3), or inside the ship (see Figure 4), with the chain either above or below the waterline: the turret can also be integrated with a vertical riser system connected to the hull or hull section (or inside) by some mechanism (frames for axial joints, mountain joints or anchor chain connections). The base of the turret can be weighted by adding weight inside the turret or by being suspended under the riser (balanced). The connection method between the above-mentioned turret and the hull affects the performance of the mooring system. The structure of the riser may include components such as steel pipe columns, chains or wire cables, and the diameter and length can vary greatly. The relative position of the chain plate and the turret also varies according to the design. Figure 5 shows several turret design types provided by the industry.
2.1.2.2 Catenary Anchor Leg Mooring (CALM)
A catenary leg mooring system consists of a large buoy supporting a number of anchor legs (see Figure 6) anchored to the seabed. A pipe or outlet pipe extending from the seabed is connected to the bottom of the CALM buoy. Some mooring systems use a nylon cable, usually a synthetic fiber cable, between the buoy and the tanker: Because the response of the CALM buoy under the influence of waves is completely different from that of the tanker, the system has a limited ability to withstand environmental conditions and when sea conditions reach a certain level, the tanker must be released. To overcome this limitation, some newer designs use a flexible structural connecting arm with a relatively large axis to connect the ship to the top of the buoy (see Figure 7). This flexible connection virtually eliminates relative horizontal movement between the buoy and the tanker: Figure 8 shows a recently developed mooring system with a flexible arm. A system that uses anchor chains to connect the vessel to a buoyant arm with a flexible mooring connection. 2.1, 2.3 Single Anchor Leg Mooring [SAI.M]
This system uses a vertical riser system that is fairly buoyant near the water surface (sometimes at the surface) and is secured to a tensioned riser. The system generally uses a section of tubular column with the riser articulated to a fixed arm (see Figure 9), or may use a chain riser with a flexible mooring connection (see Figure 10), with the buoyancy of the riser clawed at the top of the riser acting like an inverted pendulum. When the system moves horizontally, the pendulum action returns the riser to the vertical position. The tanker is either fixed to the top of the single anchor leg mooring (SALM) buoy by a flexible mooring line discussed in the description of catenary anchor mooring (CALM) or by a rigid arm: this riser base is usually fixed to the pile by a U-joint. or on weighted concrete blocks or steel structures on the seabed. In deep water, riser systems often have mid-span articulated joints. 2.1.3 Dynamic Positioning
Dynamic positioning (see Figure 11) can be used as a single positioning source or to assist a catenary mooring system. Dynamic positioning usually consists of an acoustic positioning reference system and computer-controlled thrusters around the hull. Dynamic positioning can be used in conjunction with a system called DP-assisted mooring (or thruster-assisted system if the thrusters are manually controlled). Dynamic positioning is particularly suitable for vessels that are scheduled to frequently enter and exit the site, such as oil and gas and extended testing systems.
2.2 The difference between permanent and movable mooring systems Permanent systems are usually used for production operations that are designed to last longer. For example, the system of a floating production system (FPS) is a permanent system because the typical design life of a floating production system mooring is in excess of 10 years. Movable systems Examples of mobile moorings where the mooring is often for a short period of time include mobile offshore drilling units (MODLs) and auxiliary vessels such as floating docks, drilling supply vessels and watch boats moored to other platforms in the vicinity. For operations where the design life is only a few years, the distinction between mobile and permanent may not be clear. In such cases, the user should make a judgment based on the risk of encountering harsh environments and the consequences of a minor mooring failure. As discussed below, the distinction between permanent and mobile moorings is significant. The following discussion can be used as a guide to determine the category (permanent or mobile) to which a floating structure belongs:
2.2.1 Mooring Types
A mobile floating platform will usually have the option of being equipped with an extended mooring, internal turret mooring or dynamic positioning system, while a permanent floating platform will have more mooring design options because it is not normally moved. 32 Single point mooring
Single point mooring is mainly used for oil tankers. This mooring system can make the oil tanker change direction like a weather vane. In order to minimize the environmental load acting on the oil tanker, it is necessary to make the bow of the oil tanker face the main control direction of environmental conditions. The design of single point mooring system varies, but their functions are basically the same. The single point mooring system is integrated with the production riser and the oil tanker. Typical single-point mooring systems are described as follows: |SY/T 10040—2002
head buoy
anchor head buffer
tether or fleece plate
fairlead
mooring wave source
drilling and production equipment
wire transmission and anchor chain
lateral mooring rope
well completion production section
extended mooring system
a buoyant superstructure
, submersible mid-link float
mooring steel bar bundle
drilling and tool lowering work
seabed foundation
Figure 2 Lateral mooring of tension platform
tow cable
2.1.2.1 turret mooring
SY/T 100402002
Turret mooring system is defined as a system of anchored chained legs connected to a turret. The turret forms the basic component of the moored system: the turret has bearings that allow the system to rotate around the anchor. With appropriate reinforcement measures, the turret can be mounted on the outside of the hull or hull section (see Figure 3), or inside the ship (see Figure 4), with the chain either above or below the waterline: the turret can also be integrated with a vertical riser system connected to the hull or hull section (or inside) by some mechanism (frames for axial joints, mountain joints or anchor chain connections). The base of the turret can be weighted by adding weight inside the turret or by being suspended under the riser (balanced). The connection method between the above-mentioned turret and the hull affects the performance of the mooring system. The structure of the riser may include components such as steel pipe columns, chains or wire cables, and the diameter and length can vary greatly. The relative position of the chain plate and the turret also varies according to the design. Figure 5 shows several turret design types provided by the industry.
2.1.2.2 Catenary Anchor Leg Mooring (CALM)
A catenary leg mooring system consists of a large buoy supporting a number of anchor legs (see Figure 6) anchored to the seabed. A pipe or outlet pipe extending from the seabed is connected to the bottom of the CALM buoy. Some mooring systems use a nylon cable, usually a synthetic fiber cable, between the buoy and the tanker: Because the response of the CALM buoy under the influence of waves is completely different from that of the tanker, the system has a limited ability to withstand environmental conditions and when sea conditions reach a certain level, the tanker must be released. To overcome this limitation, some newer designs use a flexible structural connecting arm with a relatively large axis to connect the ship to the top of the buoy (see Figure 7). This flexible connection virtually eliminates relative horizontal movement between the buoy and the tanker: Figure 8 shows a recently developed mooring system with a flexible arm. A system that uses anchor chains to connect the vessel to a buoyant arm with a flexible mooring connection. 2.1, 2.3 Single Anchor Leg Mooring [SAI.M]
This system uses a vertical riser system that is fairly buoyant near the water surface (sometimes at the surface) and is secured to a tensioned riser. The system generally uses a section of tubular column with the riser articulated to a fixed arm (see Figure 9), or may use a chain riser with a flexible mooring connection (see Figure 10), with the buoyancy of the riser clawed at the top of the riser acting like an inverted pendulum. When the system moves horizontally, the pendulum action returns the riser to the vertical position. The tanker is either fixed to the top of the single anchor leg mooring (SALM) buoy by a flexible mooring line discussed in the description of catenary anchor mooring (CALM) or by a rigid arm: this riser base is usually fixed to the pile by a U-joint. or on weighted concrete blocks or steel structures on the seabed. In deep water, riser systems often have mid-span articulated joints. 2.1.3 Dynamic Positioning
Dynamic positioning (see Figure 11) can be used as a single positioning source or to assist a catenary mooring system. Dynamic positioning usually consists of an acoustic positioning reference system and computer-controlled thrusters around the hull. Dynamic positioning can be used in conjunction with a system called DP-assisted mooring (or thruster-assisted system if the thrusters are manually controlled). Dynamic positioning is particularly suitable for vessels that are scheduled to frequently enter and exit the site, such as oil and gas and extended testing systems.
2.2 The difference between permanent and movable mooring systems Permanent systems are usually used for production operations that are designed to last longer. For example, the system of a floating production system (FPS) is a permanent system because the typical design life of a floating production system mooring is in excess of 10 years. Movable systems Examples of mobile moorings where the mooring is often for a short period of time include mobile offshore drilling units (MODLs) and auxiliary vessels such as floating docks, drilling supply vessels and watch boats moored to other platforms in the vicinity. For operations where the design life is only a few years, the distinction between mobile and permanent may not be clear. In such cases, the user should make a judgment based on the risk of encountering harsh environments and the consequences of a minor mooring failure. As discussed below, the distinction between permanent and mobile moorings is significant. The following discussion can be used as a guide to determine the category (permanent or mobile) to which a floating structure belongs:
2.2.1 Mooring Types
A mobile floating platform will usually have the option of being equipped with an extended mooring, internal turret mooring or dynamic positioning system, while a permanent floating platform will have more mooring design options because it is not normally moved. 33 Dynamic Positioning
Dynamic positioning (see Figure 11) can be used as the sole positioning source or to assist a catenary mooring system. Dynamic positioning usually consists of an acoustic positioning reference system and computer-controlled thrusters around the vessel. Dynamic positioning can be used in conjunction with a system known as DP-assisted mooring (or thruster-assisted if the thrusters are manually controlled). Dynamic positioning is particularly suitable for vessels that are scheduled to frequently enter and exit the site, such as oil and gas, and for extended testing of systems.
2.2 The difference between permanent and removable mooring systems Permanent systems are usually used for production operations that are designed to last longer. For example, the system of a floating production system (FPS) is a permanent system because the typical design life of a floating production system mooring is in excess of 10 years. Mobile moorings are often stationary for short periods of time. Examples of mobile moorings include mobile offshore drilling units (MODLs) and auxiliary vessels moored to other platforms in the vicinity, such as floating docks, drilling supply vessels and watch boats. For operations with a design life of only a few years, the distinction between mobile and permanent may not be clear. In such cases, the user should make a judgment based on the risk of encountering harsh environments and the consequences of a minor mooring failure. As discussed below, the distinction between permanent and mobile moorings is significant. The following discussion can be used as a guide to determine the category (permanent or mobile) to which a floating structure belongs:
2.2.1 Mooring Types
A mobile floating platform will usually have the option of being equipped with an extended mooring, internal turret mooring or dynamic positioning system, while a permanent floating platform will have more mooring design options because it is not normally moved. 33 Dynamic Positioning
Dynamic positioning (see Figure 11) can be used as the sole positioning source or to assist a catenary mooring system. Dynamic positioning usually consists of an acoustic positioning reference system and computer-controlled thrusters around the vessel. Dynamic positioning can be used in conjunction with a system known as DP-assisted mooring (or thruster-assisted if the thrusters are manually controlled). Dynamic positioning is particularly suitable for vessels that are scheduled to frequently enter and exit the site, such as oil and gas, and for extended testing of systems.
2.2 The difference between permanent and removable mooring systems Permanent systems are usually used for production operations that are designed to last longer. For example, the system of a floating production system (FPS) is a permanent system because the typical design life of a floating production system mooring is in excess of 10 years. Mobile moorings are often stationary for short periods of time. Examples of mobile moorings include mobile offshore drilling units (MODLs) and auxiliary vessels moored to other platforms in the vicinity, such as floating docks, drilling supply vessels and watch boats. For operations with a design life of only a few years, the distinction between mobile and permanent may not be clear. In such cases, the user should make a judgment based on the risk of encountering harsh environments and the consequences of a minor mooring failure. As discussed below, the distinction between permanent and mobile moorings is significant. The following discussion can be used as a guide to determine the category (permanent or mobile) to which a floating structure belongs:
2.2.1 Mooring Types
A mobile floating platform will usually have the option of being equipped with an extended mooring, internal turret mooring or dynamic positioning system, while a permanent floating platform will have more mooring design options because it is not normally moved. 3
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