M \2009 03 04\~$blank pdf BS EN 1474 3 2008 ICS 75 200 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BRITISH STANDARD Installation and equipment for liquefied natural gas — De[.]
System requirement
A description of the system and the operation shall be established
For offshore or coastal weather-exposed operations, including LNG-C mooring and transfer systems, any system that incorporates arms or hoses must be regarded as a new development It is essential to establish specific performance standards for compliance, which will be formulated based on risk assessment techniques.
Overall safety philosophy
The owner must establish and document a comprehensive safety philosophy that aligns with relevant legislation, owner requirements, industry standards, and best practices This safety philosophy should include risk categorization and acceptance criteria, and be supplemented with vendor-specific recommendations for system usage precautions before commissioning Additionally, it must be consistent with the terminal's general safety philosophy.
Overall functional targets and requirements
The overall functional requirements for the cargo transfer system shall be identified and documented As a minimum the following capabilities shall be addressed for the different operational phases:
berthing configuration (tandem or side by side or single point mooring, …);
additional requirements to the manifold on the LNG carrier when required (e.g tandem or single point mooring offloading);
procedure for connection, transfer and disconnect including emergency release;
process of monitoring and management of continual relative movements between vessels (CPMS, telemetry etc.);
procedure and facilities handling, lifting and storing of transfer equipment;
transfer capacities for LNG and vapour return (volume flow, pressure, temperature);
requirements for the ESD system (sequence, timing, process responses);
requirements related to local regulations, flag if any;
owner QA requirements, such as classification, certification requirements.
Design principles and risk assessment methodology
A risk assessment shall be conducted as part of the overall assessment of the LNG transfer system In general for the overall system assessment the following objectives would apply:
evaluation of the design and operational procedures;
determination of the limiting conditions for the offloading operations;
assessment of safety and operability via risk assessment techniques;
determination of regulatory compliance (certification, classification): this section describes the design principles and the approach to establish design requirements for the transfer system
Risk assessments must be conducted using established methods by qualified individuals who possess a thorough understanding of risk and the assessment process It is essential to document the risk assessment methodology, tools, assumptions, and system boundaries clearly.
A risk based approach shall be used to ensure that:
critical elements and operations are identified;
performance standards are defined when applicable;
controls and mitigating measures are identified;
aspects of new technology, as defined below, are identified and qualified according to requirements in Clause 5
New technology refers to innovations that lack a verified history of successful application, while proven technology is characterized by a documented track record for specific uses For further information, please refer to the Bibliography.
To effectively identify new technology, it is essential to break it down into manageable components and classify these elements based on their novelty, as outlined in Table 1, while also considering the technology's current status and its specific application area.
Table 1 — Example for classifying the technology elements
This classification implies the following:
This classification encompasses the entirety of applied technology, including its individual components, functions, and subsystems, emphasizing areas requiring caution due to limited historical data Class 1 technology consists of established methods for qualification, testing, calculations, and analysis, allowing for documented margins In contrast, technologies classified as Class 2 to 4 are considered new and must be qualified in accordance with Clause 5, enabling a targeted approach to address specific areas of concern.
Design principles
The following principles shall apply in addition to the identified requirements from a risk assessment:
1) Transfer system shall be designed, constructed and maintained with sufficient integrity to withstand operational and environmental loading throughout the system lifecycle, refer to Clause 6)
2) Systems and structures shall be designed with suitable functionality and survivability for prevention, detection, control and mitigation of foreseeable accident events affecting the installation
3) Systems and structures shall be designed in compliance with internationally accepted codes and standards
4) Where novel transfer solutions (new technology or novel application of known technology) are intended to be used, this technology is to undergo a recognized qualification procedure Refer to Clause 5
1) Escalation of accidental event to LNG Terminal or LNG carrier which are not affected by the initiating event shall be avoided/mitigated
2) Effective protection and escape shall be provided to safeguard all personnel.
Risk assessment
Hazard identification
Identifying hazards that could compromise personnel safety or the integrity of the installation is crucial This process should encompass all aspects of normal and emergency operations, including operation, maintenance, shutdown, and emergency disconnection Hazards must be categorized based on risk levels derived from functional requirements and safety philosophy.
Typical hazard identification techniques include e.g HAZOPs, FMEA, safety reviews etc
Risk categories must encompass at least personnel safety, environmental releases, and potential damage to both the installation and the LNG carrier Additionally, risks associated with production loss, operational downtime, and reputational impact may also be considered.
A typical, but not necessarily exhaustive, list of hazards includes:
loss of containment, leading to hydrocarbon releases with potential to result in fires or explosions;
collisions (e.g damage to LNG carrier, terminal and transfer system);
damage due to cryogenic leakage on surfaces (e.g embrittlement) and at sea (e.g risk of rapid transition phase);
structural and or foundation failure;
loss of stability and buoyancy;
mooring, and station keeping of approaching vessel during connection, transfer and disconnect;
extreme weather causing excessive relative motions between the installations;
failure in supporting systems (power, hydraulics, monitoring)
The hazard identification process shall address and focus on the specific issues for cargo transfer systems including:
mooring configurations for the above;
connect/disconnect and flanged connections failures;
constant position monitoring systems (CPMS) and operations;
safe isolation and inerting operations;
issues related to cargo tank overpressurization (and other containment system issues) during offloading;
containment systems for process fluids;
actual weather limitations for operation;
The results of the hazard identification and any relevant assumptions shall be documented (see 5.2).
Risk analysis
Hazard assessment shall be performed according to the method described in EN 1473
The identified hazards can be ranked based on combination of likely frequency and consequence Insignificant risks may be eliminated from further evaluation provided that relevant assumptions are documented
Risks shall not be subdivided such that individual risk elements appear trivial, whereas collectively still represent a substantial risk
Frequency assessment involves recognizing initiating events and their combinations that may result in hazards The probability of these events occurring can be determined using historical data or other relevant information.
The consequences of the hazards shall include analysis of the effects of accidents or accidental events on the safety of personnel and integrity of the installation
The assessment of key prevention and protection systems will focus on their availability and vulnerability in relation to the required functionality for each identified hazard Significant findings must align with the assumptions established in other sections of the risk analysis and assessment.
Significant major hazards identified post-screening must be thoroughly documented, including the assumptions made during the ranking process.
When relevant failure data for a quantitative risk assessment is unavailable, a semi-quantitative or qualitative approach is advisable for ranking risks Tools such as HAZOPs, fault trees, and engineering judgment can effectively identify and eliminate trivial or minor hazards This includes hazards that are highly unlikely to occur due to effective preventive measures or those that would result in minimal consequences for personnel or property.
Risk assessment
The risks from significant major hazards shall be assessed and considered together in order to show the relative contribution of different hazards to the total calculated risks
The annual risks shall be assessed against predefined risk acceptance criteria If necessary, risk reduction measures shall be applied in order to meet the acceptance criteria.
Acceptance criteria
Acceptance criteria shall be defined before performing the risk analysis
The owner must ensure that the acceptance criteria align with functional requirements and overall safety philosophy, adhering to regulatory standards and best practices.
The criteria will consider the likelihood and impact of major hazards Adhering to these acceptance criteria will form the foundation for identifying safety-critical elements and selecting appropriate performance standards.
Safety-critical elements
Once the acceptance criteria have been defined, the safety-critical elements and performance standards shall be recorded
Safety critical elements are components or systems whose failure can significantly compromise the safety and integrity of LNG transfer They are designed to prevent or mitigate hazards that pose a threat to this safety and integrity.
Safety-critical elements must be identified in alignment with the major hazard scenarios evaluated during the assessment This identification process should incorporate sound engineering judgment The determination of safety-critical items should be grounded in the potential consequences of their failure.
NOTE The safety critical elements should typically include alarms (multi stage) ERS, ESD, blow down, pressure relief venting and drainage, fire protection, station keeping and position monitoring.
Performance standards
Performance standards for safety-critical elements must be established to complement the design criteria outlined in subsequent chapters These standards should ensure that the safety-critical elements meet the risk acceptance criteria demonstrated in the assessment Additionally, the performance standards should be clearly defined, typically in quantifiable terms, to allow for verification of the safety-critical elements.
The performance standards shall reflect any relevant lifecycle requirements of the critical element
The performance standard shall also reflect any interaction or dependence between safety-critical elements for a particular major accident scenario.
Risk reduction
Effective hazard identification and analysis provide a valuable opportunity for targeted risk reduction, particularly when initiated during the concept design stage, allowing for the avoidance or minimization of risks.
Risk reduction shall be based on ALARP principle (As Low As Reasonable Practicable)
NOTE Identified hazards should be avoided/mitigated through e.g.:
removal of the source of a hazard (without introducing new sources of hazard);
breaking the sequence of events leading to realisation of a hazard
Where hazards cannot be avoided, design and operation should reduce the likelihood of hazards occurring, e.g by:
reduction in number of leak sources (flanges, instruments, valves etc.);
removal or relocation of ignition sources;
simplifying operations, avoiding complex procedures and inter-relationships between systems;
reducing the probability of external initiating events, e.g lifting operations;
reduction in inventory, pressure, temperature;
use of less hazardous materials, process or technology
The consequences of hazards should be controlled and mitigated to reduce risk to personnel, property and environment e.g through:
relocation of equipment, improved layout;
provision of physical barriers, separation distances, fire walls etc.;
provision of detection and protection systems;
provision of means to escape and evacuate
Design qualification
The new transfer system design shall satisfy:
equivalent levels of safety with conventional ship to shore LNG transfer systems;
owner’s specified level of reliability and availability;
acceptance criteria resulting from the application of Clause 4
The key issues of the qualification strategy are as follows:
assessment of suitability for purpose of the system’s design, structure, and equipment against established performance standards;
methodology for the identification of the system’s critical elements consistent with the risk assessment methodology;
criteria of risk ranking linked to the elements safety criticality;
scheme verification throughout the lifecycle of the system (certification/classification) enabling future modifications to be reviewed and verified.
Technology assessment
Transfer systems typically integrate both established and innovative technologies The evaluation of the proposed solution will aim to pinpoint the novel components and the unique application of existing technologies, thereby directing the qualification program towards these key areas.
The qualification program must ensure safety and integrity comparable to conventional systems It is essential to verify compliance with design and operational safety through accepted codes and standards using risk assessment techniques and recognized qualification procedures.
Risk assessment: failure mode identification
The failure mode identification shall provide a consistent approach with the risk assessment methodology (see Clause 4)
This shall be followed by a more systematic examination of failure modes and shall cover:
The evaluation aims to ensure that any system meets the same level of integrity as outlined in the prescriptive codes, while also identifying any gaps not addressed by these codes This is essential for fulfilling the functional requirements specified in section 4.3 and adhering to the safety performance standards established in section 4.8.
The methodology will establish a list of essential elements related to the offshore LNG transfer system At this stage, categories of criticality will be defined primarily through qualitative risk-based evaluation criteria.
Analysis and testing
For the adoption of a transfer system the following general issues should be considered:
compliance with the requirements of EN 1474-1 and EN 1474-2 (where applicable);
application of proven systems and components;
ability to monitor and manage relative movements between the two vessels and the velocity of drift of the shuttle tanker;
reliability of control equipment (such as logic control systems and hydraulic drive systems);
reliability of connecting / disconnecting systems and components;
optimum access to all system parts for inspection and maintenance
Structural analysis must emphasize new technological elements and areas highlighted in the risk assessment, as outlined in Clause 6 The goal is to evaluate both global and local structural performance of all components, ensuring they meet the relevant criteria Structural strength should be assessed under all applicable and realistic loading conditions, with special focus on the design of critical interfaces.
Design calculations should take into account the following aspects:
survival conditions intact and damage (ship to ship mooring line failure);
Validating a marine LNG transfer system typically requires basin and/or model testing, as the complexities of a dynamic environment cannot be reliably assessed through numerical methods alone This testing is a crucial phase in the design process, ensuring that it can accurately provide loads and motions for all critical components.
The risk assessments previously established in 4.6 shall require that:
sufficient qualification destructive testing is carried out, in order to conservatively validate the prediction methodology;
sufficient proof or acceptance non-destructive testing is carried out satisfactorily
It shall identify all failure modes and accurately and reliably predict the corresponding limit states, and subsequently ensure sufficient safety and availability through the service life of the system
Where new limit states exceed currently proposed design, further destructive testing may be required to further qualify the system
Some installations may need project-specific model and / or basin testing with supporting dynamic analysis carried out to establish the transfer system and mooring configuration and vessels responses
While the results of the risk assessment should clarify the relevance for each component concerned, qualification testing should address the following:
limit states under combination of pressure and external forces when applicable;
Tests must be adequately designed to evaluate the accuracy of stress/strain predictions within the elastic range, and potentially for non-linear material properties, to ensure conservatism and validate safety margins in design Additionally, the impact of fabrication tolerances should be thoroughly examined during this process.
Similarly, temperature gradients prediction methodology and their effects shall be validated as necessary
The testing program will encompass tests and measurements designed to calibrate numerical analysis tools that account for the dynamic behavior of LNG carriers in both regular and irregular wave conditions.
The model testing program must encompass a sufficient variety of load cases to effectively address all critical scenarios where each component of the transfer system encounters maximum load or movement.
Reliability analysis
Reliability and availability assessments will be conducted to thoroughly analyze critical systems, emphasizing the importance of the LNG transfer system and its components.
The goal of reliability analysis is to ensure that the functional requirements outlined in section 4.3 and the safety performance standards specified in section 4.8 are met This involves conducting reliability and availability studies that include a thorough examination of the system, emphasizing a quantitative approach based on statistical assessments of collected data.
Compliance statements
The following statements of compliance shall be issued as part of the system’s qualification process:
Statement of feasibility, concept approval certificate
A statement from an approved independent third party, such as a class society or certification body, confirms that a system can receive approval in principle based on the outcomes of a concept design evaluation or high-level risk assessment.
Statement of fitness for service, type approval certificate, certification/verification report
A certificate of fitness or class notation is issued after evaluating all relevant plans and documentation, along with an on-site survey during construction and installation This certificate confirms compliance with performance requirements, codes, rules, and regulations.
6 Design basis and criteria of a LNG transfer system
General
A risk assessment study shall be performed (see Clause 4)
Calculations shall be performed to assess the design conditions (and complemented if necessary by model tests refer to 5.4)
The design shall reflect applicable legislation – international and local, owner requirements, industry standards and best practices
Design conditions and parameters are to consider the maximum allowable significant wave heights and specific metocean conditions, beyond which any transfer of the cryogenic product is to be stopped
The transfer system in stowed position shall be designed for the same return period of the metocean data as the terminal For winds, the 3 s gust shall be considered
Any requirements on the design metocean conditions during transfer system moving (from storage to connecting position or reverse) shall be specified by the owner
Clearly defining local environmental conditions, such as temperature ranges (both sea and air), humidity levels, salt mist exposure, potential inclinations, and vibrations, is essential for the appropriate selection of materials and equipment.
Supporting structures and equipment
All fixed, floating, or ancillary structures, along with the materials and equipment utilized for supporting, lifting, or moving LNG transfer systems, must be designed, constructed, and tested in accordance with relevant codes and both international and national standards.
The supporting structures must be engineered to withstand all operational and survival metocean loads as outlined in relevant codes, ensuring they account for all loadings associated with the LNG transfer system's operation.
These structures identified to be critical (see 4.6) shall also be designed for accidental loadings All operational and accidental conditions to be identified as recommended in Clause 4
Equipment and lifting devices belonging to the LNG transfer system shall be designed for the loading as specified in applicable international offshore codes and national standards
All other fixed or floating structures and equipment shall be designed, constructed and tested in accordance with applicable international and national codes and standards
Accessories such as nitrogen injection lines, storage locking devices, ladders and platforms, liquid nitrogen lines, and thermal insulation must be designed in compliance with EN 1474-1:2008, Section 4.5 or EN 1474-2:2008, Clause 5, as applicable, or in accordance with relevant international and national codes and standards.
Transfer line diameter and product data
The LNG transfer line should be sized according to EN 1474-1:2008, 4.2.1 and/or EN 1474-2:2008, Clause 5
Pressure loss curve for LNG and vapour return within the transfer system shall be agreed between the vendor and the owner
The product characteristics shall be specified by the owner.
Dimensions and clearances
The vendor shall ensure that the transfer system satisfies all specified requirements
The design shall cater for the minimum clearances defined by the owner for the different attitudes of the transfer system
The recommended minimum clearances are essential operating requirements that account for deflections and fabrication tolerances It is crucial to define the locations of the main clearance checkpoints The vendor's clearance study must utilize a drawing of the LNG terminal layout, both in elevation and plan, which should also consider any future expansion for transfer systems.
The transfer system vendor has the responsibility to identify all check points where there is the potential for interference of all transfer systems (including future)
Risk of geometrical interferences and potential clash between the transfer system and LNGC or terminal should be avoided during connection, normal operations, normal and emergency disconnection operations
Minimum distances between the terminal and the tanker shall be clearly specified and all required means to make the transfer reliable are to be provided.
Stress analysis
Stress analysis of pressure containing and non-pressure containing components shall satisfy the applicable requirements of EN 1474-1:2008, 4.2.2.2 Flexible hoses components shall satisfy applicable requirements of
LNG terminals constructed in areas which are considered seismically active, seismic loads from appropriate floor spectra shall be considered for the structure, the foundations and the offloading system
Site investigations and analytical modelling are to be carried out to evaluate the nature, magnitude and return intervals of potential seafloor movements
For floating types terminals the dynamics loads due to terminal motions shall be considered
If applicable, green seas loads shall be considered as well as ice loads in cold environment
Accidental (survival) loads shall be considered for the design of safety critical equipment.
Dynamic behaviour (cyclic motions amplitude, speed and fatigue)
The dynamic behavior of the transfer system must be evaluated considering the relative displacements between the LNG carrier and the LNG terminal under design conditions, along with the direct effects of environmental loads on the exposed transfer system.
For stress and fatigue analysis of load-bearing components, it is essential to consider the resulting cyclic and maximum loads, particularly in relation to the structural connections with the terminal and the LNG carrier manifolds.
Fatigue response of engineering materials to various loads that might occur throughout the design life of the structural components of the transfer system shall be taken into account
The impact of different loading spectra and corresponding stress spectra, influenced by the design configuration and operational conditions of the loading/unloading system, must be considered To evaluate fatigue damage effectively, a linear cumulative damage theory can be employed.
Static loadings from weight and fluids pressure effects shall be combined if relevant, should a mean stress have an influence on fatigue life.
Special loads situations
Balancing conditions of the mobile assembly part of the transfer system, with or without ice build-up, shall be taken into consideration
The design of the transfer system shall consider, in addition to the normal operation, the emergency release of the system in both the empty and full condition.
Product swivel joints and structural bearings
Product swivel joints and structural bearings shall satisfy the requirements of EN 1474-1:2008, 4.3 and 4.4
In the design of structural bearings for floating LNG terminals, the relative movements of the vessel manifold in relation to the fixed components of the system are crucial.
Connecting/disconnecting device
The transfer system design must account for both normal operations and emergency releases, applicable in both empty and full conditions, particularly for systems that can be drained prior to emergency disconnection.
The transfer system design shall include a system preventing from over-pressure
The connecting/disconnecting device arrangement shall satisfy containment tightness and prevent/minimize spillage in case of normal operating/emergency disconnection
There shall be no clash of the transfer system with the ship or the terminal (see 6.4)
The emergency disconnection system shall be able to operate with its components ice covered.
Handling for connection, disconnection, storing
To ensure safety and efficiency, appropriate handling equipment must be available for the secure connection, disconnection, and storage of the mobile parts transfer system and any removable components Additionally, the handling system required for emergency disconnection should be specifically designed for this purpose and must remain in position throughout the transfer operations.
Communications, evacuation and rescue
A manning study shall be performed to determine the number of operating personnel required to be present for the safe connection, LNG transfer and disconnection operations of the system
Transfer systems and their respective installation areas shall be provided with a suitable alarm and public address system
In particular manned transfer system isolated from the terminal shall be provided with suitable radio communication equipment in compliance with SOLAS or applicable coastal/local regulations
For operations communications should be performed trough a LNGC – LNG terminal link as well as UHF and VHF
NOTE UHF is the Ultra High Prequency, VHF is the Very High Frequency
Means shall be provided to allow a safe escape from the manned areas to the mustering stations
The mustering stations shall be able to act as a safe haven for the duration of the evacuation
A manned transfer system, separate from the terminal, must be equipped with Life Saving Appliances (LSA) that can accommodate all personnel on board These LSAs should be designed to endure emergency situations, such as a fire at sea, for an adequate duration to ensure the safe evacuation of all individuals.
Design shall include prevention of men overboard and rescuing facilities and transfer/evacuation of wounded personnel Need of a rescue boat with launching and retrieving devices to be studied.
Others
The arrangements for the following shall comply with EN 1474-1 and EN 1474-2 where applicable, otherwise in accordance with applicable codes:
Manned superstructures and components of the transfer system must be equipped with effective passive fire bulkheads to ensure personnel safety during major accidents, providing sufficient time for a safe evacuation.
A water-spray or water curtain systems may be considered to protect the transfer system from heat radiation:
The two fire mains of the LNGC and the LNG terminal shall be considered for the design of the fire protection of the LNG transfer system
The transfer system will be equipped with fixed dry chemical powder extinguishing systems designed to combat fires in cargo handling areas, ensuring that both the system and the dry chemical powder are sufficient for effective fire suppression.
Electrical supply failure situations shall with EN 1474-1 where applicable Black-out situation shall be considered and possible interconnection of electrical supply of LNGC and terminal investigated where appropriate
A maintenance study is to be performed and suitable means of transfer of personnel, tools and spare parts provided
It is crucial to pay special attention to the loading conditions during the mounting and assembly of the main components of the transfer system This vigilance helps prevent failures, overstress, or damage such as crushing or kinking of components that may experience loads different from those specified for normal operating conditions.
An erection study shall be provided
The requirements of MARPOL shall be satisfied (drainage of machinery spaces, water, air pollution and garbage management)
The terminal shall comply with COLREG and coastal state requirements regarding safety of sea and aerial navigation
When establishing ESD and ERS alarms in the transfer system, it is essential to consider the permissible pressure surge, the closing time of the ESD and ERS valves, and the ship's drifting speed.
The transfer system shall be designed so that overall requirements to safety and reliability are met during:
approach, berthing and connecting of the transfer system to the LNG carrier;
shut down, disconnect and storage of transfer system;
emergency shutdown and disconnection of the transfer system
The safety precautions specified in this section shall ensure that:
motions of the two units are monitored within the acceptable limits both to allow berthing and connection without damaging the transfer system, the units or mooring equipment;
proper actions are taken to shut down transfer and disconnect equipment if the motions of the units (LNG carrier and LNG terminal) exceed acceptable limits;
fluid transfer is monitored and that proper actions are being taken in case of leakages or disruptions;
communication between the two units is effective to ensure proper control of the operations
In addition to these basic safety precautions, safety critical elements and the specified performance standards identified in Clause 4 shall be reflected by the owner in the specific design requirements
Risk assessment studies must analyze the purging and draining requirements of the transfer system during each loading and offloading of LNG carriers Additionally, these studies should address the necessary maintenance procedures to be performed between the loading and offloading processes.
Irrespective of the list of safety critical elements and the performance standards, the minimum requirements specified below apply unless it can be demonstrated that these requirements are not applicable
A two-way communication system between the LNG terminal (control room/control station) and the LNG carrier shall be provided In order to ensure reliable communication, equipment redundancy is required
7.3 Approach and control monitoring berthing and connection process
Effective position monitoring and control for LNG carriers, turret-moored terminals, and other vessels during berthing operations should rely on standard navigational equipment and systems If required by a risk-based approach, additional systems may be implemented to enhance safety during the approach, berthing, and connection processes.
7.4 Position monitoring, alarm and shut down system for the LNG transfer systems
The design shall take into account the parameters to be monitored, e.g.:
The mooring system of an LNG terminal significantly influences the approach and berthing processes of LNG carriers, whether utilizing spread mooring lines or weather vanes for turret-moored vessels.
The implementation of a two-stage alarm system is essential for detecting and responding to excessive relative motions between the LNG terminal and the LNG carrier This system, along with the shutdown mechanism, must adhere to the standards set by EN 1532 and EN 1474-1 Due to the LNG ship's increased degrees of freedom while moored, the alarm envelopes and settings are more intricate, necessitating a comprehensive study of Emergency Shutdown (ESD) and Emergency Response System (ERS) sequence durations This study will utilize mathematical dynamic models to accurately describe the LNG ship's movements and may include model tests under both intact and various damaged mooring conditions.
The type and number of position monitoring sensors shall be approved by the owner
A continuous monitoring system for the transfer system will be implemented to provide real-time information to operators at both the LNG terminal and the LNG carrier (LNGC).
The required safety integrity level shall be determined by the owner as part of the risk analysis as specified in Clause 4 and according to EN 61511-1 to EN 61511-3
To ensure rapid disconnection of the LNG transfer system from the LNG carrier while minimizing spillage, it is essential to implement a system featuring a double valve and an emergency release coupling (ERC) at the end of the transfer system.
In offshore transfer systems, the proximity of process facilities to the transfer system suggests that the same regulations should be applied to both, especially concerning area classification, electrical systems, fire safety, and fire detection requirements For instance, standards such as EN 1532 may be relevant in this context.
The design of the transfer system must consider the layout of the LNG terminal and the proximity of facilities, particularly in relation to classification and safety requirements.
electrical and hydraulic power supply (and emergency release in case of main electrical power failure);
The transfer system shall be provided with fluid transfer monitoring display either at a local or central control station
The control system shall be designed so that pumps cannot be operated until specific valves are opened The pumps shall stop immediately upon commencement of an emergency disconnection procedure
Pressure sensors must be strategically placed to ensure the loading pump shuts down when the line pressure surpasses a predetermined maximum limit or falls below a specified minimum threshold.
NOTE Pressure sensors that are installed on board the ship/unit's loading pumps may be accepted
Applicable safeguards, preferably interlocks shall be provided to ensure that:
main control valves cannot be opened unless the coupling is connected to the mating flange;
outboard and inboard valves adjacent to the coupling are closed before the coupling can be released NOTE Operational procedures may replace physical interlocks
Accumulators shall be provided for hydraulic operated valves The accumulators shall be of sufficient capacity to close the valves and release the coupling
8.1 Two main categories of LNG transfer systems are anticipated:
Those servicing non-dedicated LNG carriers and those servicing dedicated LNG carriers (for mooring and transfer of liquid fluids and gases)
1) Transfer systems based on transfer arms applied in a side-by-side configuration For this category the requirements in EN 1474-1:2008, Clause 7 apply
2) Other transfer systems (including side by side using transfer hoses) where the regulations in
EN 1474-1 do not apply This comprises e.g transfer systems based on flexible hoses, transfer systems in a tandem configuration For these cases particular design requirements will be developed as described in 4.7
8.2 Additional requirements for the ship shall address:
loads exerted from the transfer system onto the manifolds;
size limitations for the LNG carrier incorporated as an assumption in the determination of the motion characteristics and the envelope;
During the loading process, it is essential to assess the maximum sea states to ensure that the motions of LNG carriers, along with the sloshing effects, are manageable This article will outline the typical documentation required for an offshore LNG transfer system.
requirements to LNG carrier systems and equipment for positioning and control of the vessel during approach, berthing and connecting
8.3 In order maximise the level of standardisation the following guidance shall be observed:
Cargo piping shall preferably be designed in accordance with regulations for LNG carriers and terminals with respect to:
The transfer system's owner may impose additional standards, such as offshore standards, while ensuring compatibility with the LNG carrier at the interface between the two systems.
8.4 Systems and equipment for the position control of the LNG carrier during berthing, connection and transfer:
To the extent possible shall be based on standard shipboard systems Additional equipments and systems shall be installed when deemed necessary as per Clause 4
Reference shall be made to EN 1474-1 and Clause 7
Reference shall be made to EN 1474-1, Clause 8 and EN 1474-2:2008, Clause 6
In addition the following shall be documented:
particular requirements to operational test to be conducted on site prior to commissioning as identified in
EN 1474-1:2008, Clauses 4, 5 or 8, for systems based on loading arms;
particular requirements to tests and inspection to be conducted in operation;
in preparation for the transfer operation;
after the completed transfer operation;
The quality system shall conform to EN ISO 9000 and EN ISO 9001
Reference shall be made to EN 1474-1, Clause 10, EN 1474-2:2008, 7.5, Clause 8 for tender documentation and contract documentation
In addition the following shall be documented:
site specification and environmental conditions forming the basis for motion envelopes;
particular requirements for the LNG carrier embedded in the design of the transfer system:
loads exerted from the transfer system onto the manifolds;
size limitations for the LNG carrier (if any) as a result of the determination of the motion characteristics;
Communication
A two-way communication system between the LNG terminal (control room/control station) and the LNG carrier shall be provided In order to ensure reliable communication, equipment redundancy is required.
Approach and control monitoring berthing and connection process
Effective position monitoring and control for LNG carriers, turret-moored LNG terminals, and other vessels during berthing operations should rely on standard navigational equipment and systems If required, additional systems may be implemented as part of a risk-based approach to enhance safety during the approach, berthing, and connection processes.
Position monitoring, alarm and shut down system for the LNG transfer systems
The design shall take into account the parameters to be monitored, e.g.:
The mooring system of an LNG terminal significantly influences the approach and berthing processes of LNG carriers, whether utilizing spread mooring lines or weather vanes for turret-moored vessels.
The implementation of a two-stage alarm system is essential for detecting and responding to excessive relative motions between the LNG terminal and the LNG carrier This system must adhere to the standards set by EN 1532 and EN 1474-1 Due to the LNG ship's increased degrees of freedom while moored, the alarm envelopes and settings are more complex, necessitating a thorough study of Emergency Shutdown (ESD) and Emergency Response Sequences (ERS) durations This study will utilize mathematical dynamic models to accurately describe the LNG ship's movements and may include model tests under both intact and various damaged mooring conditions.
The type and number of position monitoring sensors shall be approved by the owner
A continuous monitoring system for the transfer system will be implemented to provide real-time information to operators at both the LNG terminal and the LNG carrier (LNGC).
The required safety integrity level shall be determined by the owner as part of the risk analysis as specified in Clause 4 and according to EN 61511-1 to EN 61511-3.
ERS system
To ensure rapid disconnection of the LNG transfer system from the LNG carrier while minimizing spillage, it is essential to implement a system featuring a double valve and an emergency release coupling (ERC) at the end of the transfer system.
Safety interfaces
In offshore transfer systems, the proximity of process facilities to the transfer system suggests that the same regulations should be applied to both, especially concerning area classification, electrical systems, fire safety, and fire detection requirements For instance, standards such as EN 1532 may be relevant in this context.
The design of the transfer system must consider the layout of the LNG terminal and the proximity of facilities, particularly in relation to classification and safety requirements.
electrical and hydraulic power supply (and emergency release in case of main electrical power failure);
Control of fluid transfer
The transfer system shall be provided with fluid transfer monitoring display either at a local or central control station
The control system shall be designed so that pumps cannot be operated until specific valves are opened The pumps shall stop immediately upon commencement of an emergency disconnection procedure
Pressure sensors must be strategically placed to ensure the loading pump shuts down when the line pressure exceeds a predetermined maximum or falls below a specified minimum threshold.
NOTE Pressure sensors that are installed on board the ship/unit's loading pumps may be accepted
Applicable safeguards, preferably interlocks shall be provided to ensure that:
main control valves cannot be opened unless the coupling is connected to the mating flange;
outboard and inboard valves adjacent to the coupling are closed before the coupling can be released NOTE Operational procedures may replace physical interlocks
Accumulators shall be provided for hydraulic operated valves The accumulators shall be of sufficient capacity to close the valves and release the coupling
Two main categories of LNG transfer systems are anticipated
Those servicing non-dedicated LNG carriers and those servicing dedicated LNG carriers (for mooring and transfer of liquid fluids and gases)
1) Transfer systems based on transfer arms applied in a side-by-side configuration For this category the requirements in EN 1474-1:2008, Clause 7 apply
2) Other transfer systems (including side by side using transfer hoses) where the regulations in
EN 1474-1 do not apply This comprises e.g transfer systems based on flexible hoses, transfer systems in a tandem configuration For these cases particular design requirements will be developed as described in 4.7.
Additional requirements for the ship shall address
loads exerted from the transfer system onto the manifolds;
size limitations for the LNG carrier incorporated as an assumption in the determination of the motion characteristics and the envelope;
During the loading process, it is essential to assess maximum sea states to ensure that the motions of LNG carriers, along with the sloshing effects, are manageable This article will outline the typical documentation required for an offshore LNG transfer system.
requirements to LNG carrier systems and equipment for positioning and control of the vessel during approach, berthing and connecting.
In order maximise the level of standardisation the following guidance shall be observed
Cargo piping shall preferably be designed in accordance with regulations for LNG carriers and terminals with respect to:
The owner of the transfer system may impose additional standards, such as offshore standards, while ensuring compatibility with the LNG carrier at the interface between the transfer system and the LNG carrier.
Systems and equipment for the position control of the LNG carrier during berthing,
To the extent possible shall be based on standard shipboard systems Additional equipments and systems shall be installed when deemed necessary as per Clause 4
Reference shall be made to EN 1474-1 and Clause 7
Reference shall be made to EN 1474-1, Clause 8 and EN 1474-2:2008, Clause 6
In addition the following shall be documented:
particular requirements to operational test to be conducted on site prior to commissioning as identified in
EN 1474-1:2008, Clauses 4, 5 or 8, for systems based on loading arms;
particular requirements to tests and inspection to be conducted in operation;
in preparation for the transfer operation;
after the completed transfer operation;
The quality system shall conform to EN ISO 9000 and EN ISO 9001
Reference shall be made to EN 1474-1, Clause 10, EN 1474-2:2008, 7.5, Clause 8 for tender documentation and contract documentation
In addition the following shall be documented:
site specification and environmental conditions forming the basis for motion envelopes;
particular requirements for the LNG carrier embedded in the design of the transfer system:
loads exerted from the transfer system onto the manifolds;
size limitations for the LNG carrier (if any) as a result of the determination of the motion characteristics;
During the loading process, it is essential to assess the maximum sea states to ensure that the vessel's motions and the sloshing effects on the LNG carrier are manageable This article will outline the typical documentation required for an offshore LNG transfer system.
requirements to systems and equipment for positioning and control of the LNG carrier during approach, berthing and connecting;
specific requirements to communication equipment
Procedure for deviation from the full standard
If such a deviation is proposed, then:
gap analysis of this transfer system design compared to present standard shall be performed;
For every identified deviation, it is essential to review the safety philosophy and employ a risk-based approach to justify the deviation Additionally, it must be demonstrated that the system maintains an acceptable safety level in full compliance with Clause 4 and other pertinent sections.
approval by a recognized classification society is required;
whole process shall be documented for future reference
[1] Classification and Certification of Floating Offshore Liquefied Gas Installations, Guidance Notes – LR
[2] Classification and Certification of Offshore Gravity Based Liquefied Gas Installations, Guidance Notes – LR
[3] Classification and Certification of Offshore LNG Terminals, Guidance Note NI 518 DT R00 E – BV
[4] Guidance Notes on Review and Approval of Novel Concepts – ABS
[5] Guidance Notes on Risk Assessment for Marine and Offshore Oil and Gas Industries – ABS
[6] Guide for Building and Classing Offshore LNG Terminals – ABS
[7] Guideline for Alleviation of Surge Pressure on ESD – SIGTTO
[8] Guidelines for Linked Ship/Shore Emergency Shutdown of Liquefied Gas Transfer – SIGTTO
[9] IGC Code and Amendments – IMO, International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk
[10] LNG Operations in Port Areas – Essential Best Practices for the Industry – SIGTTO
[11] Offshore Gas Export and Receiving Terminals: OTG 02 – DNV
[12] Offshore Loading Safety Guidelines – OCIMF
[13] Qualification Procedures for New Technology, DNV-RP-A203 – DNV
[14] Recommended Practice for Design and Analysis of Station Keeping Systems for Floating Structures, API Recommended Practice 2 SK – API
[15] Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms (WSD, LFRD), API Recommended Practice 2 A - API
[16] Tandem Loading Guideline – UKOOA FPSO Committee
[17] Tandem Mooring and Offloading Guidelines for Non Specialized Tankers at F(P)SO Facilities – OCIMF
[18] Verification, Certification and Classification of New Technologies, DNV-OSS-309 - DNV
[19] EN 1160, Installations and equipment for liquefied natural gas — General characteristics of liquefied natural gas
[20] EN ISO 19901 (all parts), Petroleum and natural gas industries — Specific requirements for offshore structures
[21] EN ISO 19904-1, Petroleum and natural gas industries — Floating offshore structures — Part 1:
Monohulls, semi-submersibles and spars (ISO 19904-1:2006)