Section 4 System Design

4.1 General

4.1.1 Materials, components and equipment to be used in the construction of regasification systems shall be suitable for the intended service conditions and acceptable to LR. The materials, components and equipment shall also satisfy the requirements of this Section.

4.1.2 Materials shall comply with the requirements of the Rules for the Manufacture, Testing and Certification of Materials (hereinafter referred to as the Rules for Materials) and Pt 11, Ch 6 Materials of Construction and Quality Control .

4.1.3 The design, arrangements and selection of equipment shall be such as to minimise the risk of fire and explosion from flammable products.

4.1.4 Electrical components and equipment shall comply with Section Pt 11, Ch 20, 7 Electrical installation.

4.1.5 Any single failure of the regasification system shall not result in a hazard that affects safety.

4.1.6 The regasification barge or offshore unit shall have adequate capability for managing the boil-off gas generated by heat ingress through headers, manifolds flexible hoses and loading arms during barge or offshore unit-to-ship transfer operations.

4.1.7 The regasification system shall include provision to pre-cool the product transfer piping system prior to barge or offshore unit-to-ship transfer operations commencing.

4.2 Vaporisers

4.2.1 The requirements of these Rules apply to various types and designs of vaporiser and process units, such as:

Heat exchanger designs including:
- STV – Shell and tube heat exchanger type.
- PCHE – Printed circuit heat exchanger.
- AHHE – Air heated heat exchanger utilising forced ventilation.
- CWHE – Coil wound heat exchanger.
ORV – Open rack type utilising sea-water or a circulating intermediate heated fluid.
SCV – Submerged combustion type utilising the heat of combustion of either oil or send-out gas.

4.2.2 Vaporising units of novel design, making use of materials not covered by the Rules, will be subject to special consideration and subject to the requirements of Pt 7, Ch 14 Requirements for Machinery and Engineering Systems of Unconventional Design of the Rules for Ships, ‘Requirements for machinery and engineering systems of unconventional design’.

4.2.3 The manufacture, installation and testing of vaporisers, including the intermediate heat transfer vessels and pumping systems, shall be undertaken in accordance with these.

4.2.4 All LNG high pressure pumps supplying vaporisers, which are capable of developing a pressure exceeding the design pressure of the system into which they are pumping, are to be provided with relief valves in closed circuit.

4.2.5 For STVs and ORVs, sea-water may be used as a primary heat source for vaporisation. An intermediate heat transfer fluid may be proposed to reduce the chance of freezing and effects of corrosion.

4.2.6 Where sea-water is used as the source of heat to vaporise the LNG, the tubes shall be manufactured from a corrosion-resistant material, taking into consideration the type and temperature of media conveyed. Where the ✠Lloyd’s RGP+ Notation is to be assigned, suitable redundancy of the sea-water circulation pump and LNG high pressure supply pumps shall be provided.

4.2.7 When an intermediate heat transfer fluid is used, and where the ✠Lloyd’s RGP+ Notation is to be assigned, dual compressors or circulating pumps shall be provided. Where the heat transfer fluid goes through a phase change, the applicable Sections of Pt 6, Ch 3 Refrigerated Cargo Installations shall be complied with.

4.2.8 Where potential risk of failure of a tube or passage could result in gas entering the sea-water side:

the sea-water side shall be designed to accept the full gas pressure of the gas side;
the sea-water side shall be protected with bursting discs or relief valves in readily visible positions; the discharge from these bursting discs or relief valves shall be taken to a suitable high-pressure venting arrangement and the number and position of bursting discs or relief valves shall be adequate to relieve the flow occurring due to failure of a single tube.

4.2.9 If steam is used in a heat exchanger containing LNG, propane or other flammable gas, the condensate shall not be passed directly back to the machinery room. The steam-condensate shall be passed through a degassing tank located in a gas-dangerous area. The vent outlet from the degassing tank shall be routed to a safe location and be fitted with a flame screen. The degassing tank shall be fitted with a gas detection and alarm system, see Pt 11, Ch 13, 1.6 Gas detection.

4.2.10 If the barge or offshore unit is to operate in regions where insufficient natural sources of heat are available for vaporisation, e.g. due to low sea-water temperature, the design gas output conditions shall be maintained utilising alternative means.

4.2.11 Where alternative means of heating the LNG are required, an independent gas or oil supply system shall be provided to facilitate initial start-up.

4.2.12 The regasification system may operate with a dual heat source with, for example, a mixture of heat inputs from sea-water and a boiler.

4.2.13 Where aluminium alloy vertical tubes and horizontal headers are constantly covered with sea-water, adequate protection against corrosion shall be provided.

4.2.14 Commissioning and testing of vaporisers may be undertaken by the manufacturer prior to units being installed on board in accordance with Pt 11, Ch 20, 8.2 Commissioning regasification trials.

4.2.15 Water supply pumps shall be fitted with suitable inlet filters. It shall be possible to remove and clean the filters whilst the regasification system remains operational. Any regasification system-related sea-water inlet shall be fitted with gratings and provision made to allow cleaning by low pressure steam or compressed air.

4.2.16 A water treatment system shall be incorporated for use with submerged combustion vaporisers to eliminate degradation of the tubes.

4.2.17 The submerged combustion vaporisers shall comply with the relevant Sections applicable to inert gas generators and steam boilers operating with boil-off gas, as applicable, stated in Pt 11, Ch 7 Cargo Pressure/Temperature Control and Pt 5, Ch 10 Steam Raising Plant and Associated Pressure Vessels and Pt 5, Ch 11 Other Pressure Vessels.

4.3 Gas detection system

4.3.1 In addition to the gas detection system fitted to allow compliance with Pt 11, Ch 13 Instrumentation and Automation Systems, a permanently installed system of gas detection and audible and visual alarms is to be fitted in:

all enclosed spaces containing gas piping, liquid piping or regasification equipment;
other enclosed or semi-enclosed spaces where gas vapours may accumulate;
air-locks;
secondary fluid expansion tanks;
the condensate degassing tank.

4.3.2 Gas detection equipment is to be designed, installed and tested in accordance with IEC 60079-29-1, an is to be suitable for the gases to be detected.

4.3.3 The number and the positions of detection heads or sampling heads is to be determined with due regard to the size and layout of the semi-enclosed space or compartment and be in accordance with the equipment manufacturer’s recommendations. Due regard is to be given to the air flow from compartment ventilation inlets and outlets.

4.3.4 The gas detection system serving the regasification plant may be either independent or combined with the gas detection system installed to allow compliance with Pt 11, Ch 13 Instrumentation and Automation Systems.

4.3.5 The gas detection is to be of the continuous monitoring type, capable of immediate response.

4.3.6 The gas detection system serving the regasification plant is otherwise to comply with the construction and Installation requirements of Pt 11, Ch 13 Instrumentation and Automation Systems.

4.4 Emergency shutdown (ESD) system

4.4.1 An emergency shutdown (ESD) system serving the regasification plant and sub-systems and equipment shall be fitted and shall comply with the cause and effect matrix shown in Pt 11, Ch 20, 4.4 Emergency shutdown (ESD) system 4.4.4 Pt 11, Ch 20, 4.4 Emergency shutdown (ESD) system as applicable.

4.4.2 The ESD system shall be activated by the manual and automatic inputs listed in Pt 11, Ch 20, 4.4 Emergency shutdown (ESD) system 4.4.4. Any additional inputs shall only be included in the ESD system if it can be shown that their inclusion does not reduce the integrity and reliability of the system overall.

4.4.3 The ESD system shall return the regasification system to a safe static condition, allowing remedial action to be taken. Due regard shall be given in the design of the ESD system to avoid the generation of surge pressures within both the liquid and vapour pipework.

4.4.4 The equipment to be shut down on ESD activation shall include manifold valves during loading or discharge, and pumps and compressors associated with transferring LNG and NG.

Table 20.4.1 ESD functional arrangements

	Pumps		Compressor systems				Valves	Link
Shutdown action Initiation	Cargo pumps/cargo booster pumps	Spray/ stripping pumps	Vapour return compressors	Fuel gas compressors and system	Reliquefaction plant, including condensate return pumps, if fitted	Gas combustion unit	ESD valves	Signal to barge or regas’ unit/shore link***
Emergency push buttons (see Pt 11, Ch 20, 4.4 Emergency shutdown (ESD) system 4.4.2)				See Note 2
Fire detection on deck or in compressor house*
High level in storage tank				See Notes 1 and 2	See Notes 1 and 3	See Note 1	See Note 4
Signal from barge or regas’ unit/shore link				See Note 2	See Note 3	n/a		n/a
Loss of motive power to ESD valves**				See Note 2	See Note 3	n/a
Main electric power failure ('blackout')	See Note 5	See Note 5	See Note 5	See Note 5	See Note 5	See Note 5
KEY * Fusible plugs, electronic point temperature monitoring or area fire detection may be used for this purpose on deck Failure of hydraulic, electric or pneumatic power for remotely operated ESD valve actuators * Signal need not indicate the event initiating ESD Functional requirement n/a Not applicable
NOTES 1. These items of equipment can be omitted from these specific automatic shutdown initiators provided the compressor inlets are protected against cargo liquid ingress. 2. If the fuel gas compressor is used to return cargo vapour to shore, it shall be included in the ESD system only when operating in this mode. 3. If the reliquefaction plant compressors are used for vapour return/shore line clearing, they shall be included in the ESD system only when operating in that mode. 4. A sensor operating independently of the high liquid level alarm shall automatically actuate a shut-off valve in a manner that will both avoid excessive liquid pressure in the loading line and prevent the tank from becoming liquid full. These sensors may be used to close automatically the tank filling valve for the individual tank where the sensors are installed, as an alternative to closing the ESD valve provided at eachmanifold connection. If this option is adopted, activation of the full ESD system shall be initiated when the high-level sensors in all the tanks to be loaded have been activated. 5. These items of equipment shall be designed not to restart automatically upon recovery of main electric power and without confirmation of safe conditions.

4.4.5 The emergency shutdown system associated with the regasification system shall be designed, manufactured and tested in accordance with the principles stated in Pt 11, Ch 5, 2.2 Cargo system valve requirements.

4.4.6 The number and location of additional shutdown positions shall be determined by the type, number, location and position of the regasification plant, sub-systems and equipment.

4.5 Process shutdown (PSD) system

4.5.1 A process shutdown system (PSD) for the regasification system shall be arranged in accordance with the requirements listed in Pt 11, Ch 20, 6 Instrumentation, control, alarm and monitoring.

4.5.2 The activation of the PSD shall stop the supply of LNG to the LNG suction drum, high pressure LNG pumps and gas discharge valve. Where the installation comprises a number of separate regasification systems the PSD may be system-specific as well as initiating a full shutdown. A PSD functional arrangement matrix commensurate with that shown in Pt 11, Ch 20, 4.4 Emergency shutdown (ESD) system 4.4.4 shall be provided.

4.5.3 Manual PSD points shall be arranged at each regasification system’s control station and at locations as determined by the type, number, location and position of the regasification systems and equipment. The process shutdown points shall be clearly indicated.

4.5.4 Process shutdown valves in liquid piping shall close fully under all service conditions within an acceptable duration of actuation. Due regard shall be given in the design of the process shutdown system to avoid the generation of surge pressures within drain pipelines and collect tanks. Information about the closing time of the valves and their operating characteristics shall be available on board and the closing time shall be verifiable and reproducible.

4.5.5 The closure time for the shutdown valve referred to in Pt 11, Ch 20, 5.4 Piping system testing and non-destructive examination shall be measured from the time of manual or automatic initiation to final closure and is made up of a signal response time and a valve closure time. Valve closure time shall be such as to avoid surge pressure in pipelines.

4.6 Depressurisation and blowdown system

4.6.1 In accordance with ISO 23251 or equivalent.

4.6.2 A depressurisation and blowdown system shall be provided for depressurising high pressures liquid, vapour and gas systems. Each high pressure system may contain; liquid pumps, gas compressors, vessels, heat exchangers and pipework.

4.6.3 Where a liquid depressurisation system is provided, adequate provision shall be made in the design and installation for the effects of back pressure after the blowdown valve and the resulting volume of vapour flash gas due to the pressure drop.

4.6.4 Manual and automatic activation of the depressurisation system shall be provided.

4.6.5 Manual activation shall be possible from each regasification system’s control station, at the send-out manifold, and from other locations as determined by the type, number, location and position of the regasification systems and equipment. The depressurisation and blowdown system activation points shall be clearly indicated.

4.6.6 Automatic activation shall be part of the emergency shutdown arrangements.

4.7 System and pressure vessel protection

4.7.1 Each regasification system and associated pressure vessel is to be fitted with a form of secondary protection. This may take the form of pressure relief valves or alternatively an instrument-based system.

4.7.2 Pressure relief and venting system

Each regasification unit shall be provided with safety relief valves and venting arrangements which are to be separate from the venting arrangements serving the LNG storage tanks. High pressure safety relief valves, headers, knock-out pots, collection tanks, drain drums and vent masts shall be located within the cargo deck area.
High pressure safety relief valves and venting arrangements for liquid and gas shall be provided for each regasification system. The safety relief valve support arrangements shall be suitable to withstand the loads imposed by relief valve opening.
Where multiple regasification systems are installed, the design of pressure safety relief and venting arrangements shall consider the maximum combined release rate.
The gaseous phase safety relief valves shall be led to a dedicated high pressure vent mast for the regasification system required by Pt 11, Ch 20, 4.7 System and pressure vessel protection 4.7.2. The high pressure vent mast shall be sized to handle the maximum regasification capacity and to ensure safe dispersal of the gas.
The liquid phase safety relief valves shall be led to a knock-out pot, collection tank or drain drum having adequate capacity for the maximum LNG inflow anticipated within the design of the regasification unit. The collection vessel shall be fitted with a level switch to stop all high pressure LNG pumps. Any LNG from the collection vessel shall be safely drained back to the LNG storage tanks or be allowed to boil off and vapour to be returned to the barge or offshore unit’s vapour header.
LNG collection vessels shall be fitted with pressure safety relief valves in accordance with Pt 11, Ch 5 Process Pressure Vessels and Liquids, Vapour and Pressure Piping Systems and Offshore Arrangements.
Pressure safety relief valves and venting arrangements and locations shall comply with Pt 11, Ch 8 Vent Systems for Cargo Containment .

4.7.3 Instrument-based system

Instrument-based systems, in compliance with ISO 10418, may be used for both primary and secondary protection provided it is implemented in accordance with IEC 61511-1.

4.8 Fire protection and fire extinction

4.8.1 The regasification system shall be protected with both a water spray deluge system plus a dry chemical powder system and a fire detection system. The systems shall meet the requirements of Pt 11, Ch 11 Fire Prevention and Extinction .

4.8.2 The water spray deluge system and dry chemical powder system installed on board the barge or offshore unit shall be capable of providing coverage for the areas defined in Pt 11, Ch 11 Fire Prevention and Extinction and the regasification system simultaneously.

4.8.3 The barge or offshore unit’s water spray deluge system shall be designed to cover the regasification equipment, barge or offshore unit-to-ship LNG flexible hoses or loading arms and gas export manifold.

4.8.4 Protection from fire and heat shall be provided as necessary for the safe escape of personnel in case of an emergency. Details shall be submitted for appraisal as indicated in Pt 11, Ch 20, 2.1 General 2.1.1.

4.8.5 Fire protection arrangements shall be such as to prevent possible jet fires propagating from the regasification unit to the adjacent LNG storage tank areas. Proposed arrangements shall be evaluated in the risk based studies in Pt 11, Ch 20, 3.2 System safety risk assessment.

4.9 Location and arrangement of equipment

4.9.1 The location of the regasification unit and its sub-systems containing LNG and NG shall be considered part of the cargo area. The regasification units and all their associated equipment shall be located as far as is reasonably possible from accommodation spaces.

4.9.2 The regasification system machinery may be located on the open deck or in cargo pump and cargo compressor rooms. Arrangements of such spaces shall be in accordance with the requirements of Pt 11, Ch 3 Ship Arrangements.

4.9.3 When the regasification units are located on open deck they shall be placed in a sheltered location protected from green water.

4.9.4 The locations of the system arrangements, including vaporisers, high pressure pumps, suction drums, heaters, liquid pumps and ancillary piping systems, shall be defined and evaluated in the system safety risk assessment, see Section Pt 11, Ch 20, 3.2 System safety risk assessment, and shall be acceptable to LR.

4.9.5 The deck plating and sub-structure of the barge or offshore unit shall be protected from possible cryogenic spills associated with the regasification unit and suction drum in way of fittings, fixtures and demountable joints. No protection will be required in locations where the deck and sub-structure material can withstand cryogenic temperatures.