In addition to the regulations established by international organizations such as the International Maritime Organization (IMO), there are additional rules and guidelines provided by classification societies like the American Bureau of Shipping (ABS) and regulatory bodies like the United States Coast Guard (USCG). These entities offer supplementary standards and requirements to enhance safety and operational efficiency in the LNG industry. ABS, for instance, provides classification rules specific to LNG carriers, covering aspects such as structural design, materials, propulsion systems, cargo containment, and onboard systems. These rules are continuously updated to incorporate technological advancements and address emerging risks.
Similarly, the USCG offers regulations and guidelines tailored to LNG facilities and operations within the United States jurisdiction. These regulations encompass safety and security measures for LNG terminals, bunkering operations, vessel traffic management, and emergency response planning. Additionally, industry organizations and technical societies publish guides and best practices to assist stakeholders in implementing effective risk management strategies, conducting hazard assessments, and achieving compliance with regulatory requirements. By adhering to these additional rules, guides, and standards, LNG industry participants can ensure the safe, reliable, and environmentally responsible handling and transportation of liquefied natural gas.
The ABS Rules
Rules for LNG Carriers
The specific ABS Rules for LNG carriers are in Part 5, Chapter 8. As many other Classification Societies, ABS adopted the IGC Code as its own Rules. However, the content of the Code has been integrated by a number of additional requirements and interpretation that are to be complied with to receive ABS class. These additional requirements / interpretations may be originated by IACS Unified Requirements, IACS Interpretations or by ABS only.
In order to distinguish which are the original IGC Code requirements with respect of the specific ABS requirements, two different fonts have been adopted in the Rules. The part of the text written using “italic” font is identical to the content of the IGC Code. The part of the text written using “regular” font is the ABS addition: besides each added paragraph title there is the indication in brackets, whether the requirement therein contained is coming from ABS or from IACS.
Read also: Regulations and Rules for Vessels to Carry Liquefied Gas
The numbering system adds the ABS numbering to the original IGC Code numbering system. In other words, Part 5, Chapter 8 is added before the original numbering of the IGC Code Chapters that become “Sections” in the ABS Rules.
This System does allow a user of the ABS Rules not to have the IGC Code, as all its content, including references may be easily found in the Rules.
The Rules for surveys on existing LNG carriers are contained in Part 7, Chapter 3, Sections 2 of the Steel Vessels Rules. These Rules will be examined in detail under Module 18.
Additional Rules and Guides
As matters related to LNG’s ships are quite complex, ABS has prepared a series of additional Rules and Guidance that cover various aspects relative to LNG carriers. In particular they are:
a) Guide For Building and Classing Membrane Tank LNG Vessels (November 2002).
This Guide gives detailed design criteria for the structures of membrane ships and for their fatigue assessment.
b) Guide for Design and Installation of Dual Fuel Diesel Engines (January 2003).
ABS has been the first among the Classification Societies to publish a comprehensive guidance covering the dual fuel diesel engines. This Guide is quite important as dual fuel diesel engines are envisaged as the propulsion system that will be used by the next generation of LNG carriers.
c) Guide for Building and Classing Offshore LNG Terminals (April 2004).
Also this Guide puts ABS in the forefront with respect to other Classification Societies, as in the future many new LNG terminals will be built offshore.
d) Guidance Notes on Reliability – Centered Maintenance (July 2004).
e) Guide for Survey Based on Reliability – Centered Maintenance (December 2003).
The above Guides are not particular of LNG carriers, however, the survey based on reliability – centered maintenance would appear quite suitable for Condition Assessment Program for Liquefied Gas Carriers (CAP LNG)LNG carriers. As soon as the LNG ships Owners become aware of this opportunity and of the advantages of this kind of survey system, they are likely to subscribe it. This matter will be further dealt with in Module 18.
The USCG Rules
Since the IMO recommendations defer some matters to the discretion of each Administration, and in other matters are not specific enough, for Coast Guard regulatory purpose, several major changes have been introduced from the code in the proposed Coast Guard rules. These changes are to be taken into account if the ship is intended to visit US ports.
Liquefied Gas Definition
Definition of “Liquefied Gas Carrier TypesLiquefied gas” is changed from the Code’s definition of “a product having a vapor pressure of 2,8 kp/cm2 at 37,8 °C” to the proposed definition of “a product having a vapor pressure of 1,76 kp/cm2 at 37,8 °C“. This is a change in the definition from a Reid vapor pressure of 40 psia to 25 psia. The change in the Reid vapor pressure includes the “certain other substances” referred to in paragraph 1.2 of the Code, but does not include any product in IMO’s Chemical Code except ethylene, which is presently listed in the Code and the Chemical Code. The change in the Reid vapor pressure was proposed by the United State delegation to IMO but the change was not adopted, although there was apparently no objection to it. The change, however, does not affect the list of regulated cargoes.
Air Changes in Air Locks
The rate of air change between the air lock is not specified in the Code (paragraph 3.6.1) but is proposed at 12 changes per hour.
Leaks in the Interbarier Spaces
It is proposed that leaked cargo from interbarrier spaces be pumped to an emergency dump. This is proposed as an alternative to the Code requirement that leaked cargo is returned to the cargo tanks.
Reference Ambient Temperature
Chapter 4 of the Code includes a provision for the evaluation of the insulation and hull steel assuming, for the purpose of design calculations, that the cargo tank and secondary barrier, if installed, are at the design temperature and the ambient outside air and sea design temperatures as follows:
General Worldwide:
- Still Air: +5 °C (41 °F).
- Sea Water: 0 °C (32 °F).
Chapter 4 also provides that each administration may set higher or lower ambient design temperatures. USCG requires that the following reference temperatures be considered:
Any Waters in the World, except Alaskan Waters:- Air (at 5 knots): -18 °C (0 °F).
- Still Sea Water: 0 °C (32 °F).
Alaskan Waters:
- Air (at 5 knots): -29 °C (–20 °F).
- Still Sea Water: – 2 °C (28 °F).
This is already a USCG requirement. It is of the utmost importance that this requirement is complied with as early as at design stage. Otherwise the ship will be not allowed to call US ports.
This matter will be dealt with in detail in Module 5.
Steel Grades
The USCG regulations specify enhanced grades of steel for crack arresting purposes in the deck stringer, sheer strake, and bilge strake. The grades of steel as noted or their equivalents are to be used in the location indicated below:
- Deck stringer – Grade E.
- Sheer strake – Grade E.
- Turn of the bilge – Grade D or E.
This is already a USCG requirement. It is of the utmost importance that this requirement is complied with as early as at design stage. Otherwise the ship will be not allowed to call US ports.
Allowable Stresses
For independent tank types B and C, stress factors are not the same as the stress factor for these tanks in the Code. In the Code, the stress factors listed for independent tank types B and C are the minimum factors that may be used in calculation. The stress factors indicated by USCG meet Section VIII of the ASME Code, 1974, and are greater than the minimum listed in the Code, and must be used in independent tank type B and C calculations for vessels to which the regulations apply.
This is already a USCG requirement. It is of the utmost importance that this requirement is complied with as early as at design stage. Otherwise the ship will be not allowed to call US ports.
Venting Cargo
The Code allows pressure and temperature control of cargoes by venting cargo vapors to the atmosphere when the vessel is at sea and in port if this is accepted by receiving Administration. USCG proposed to prohibit normal venting of cargo into the atmosphere in many ports.
Cargo Tank Pressurization
The Code requires the cargo system to be designed to withstand the full vapor pressure of the cargo under conditions of the upper ambient design temperature or have other means to maintain the cargo tank pressure below the maximum allowable relief valve setting (MARVS) of the tank. USCG proposes that when the cargo carried is a liquefied gas, the cargo tank pressure must be maintained below the design vapor pressure indefinitely. Accordingly, the pressure on the Prevention rollover in LNG TanksLNG tank would be maintained below the design pressure for a period of not less than 21 days. Cargo tank pressure may be maintained below the design pressure by several methods including refrigeration systems, burning boil-off in waste heat or catalytic furnaces, using boil-off as fuel, or a combination of these methods. Using the boil-off as a fuel for propulsion is limited to a vessel carrying LNG LPG boil-off is not allowed as fuel for propulsion as LPG vapours are heavier than air.x.
Further USCG Requirements
The proposed regulations also include the following:
1) Transfer requirements for vinyl chloride.
2) Loading requirements for methyl acetylene propadiene mixture.
3) Additional operating requirements.
4) Requirements for inspection or re-inspection of US flag vessels at intervals that are the same as for vessels inspected under Subchapter D. Inspection for certification would be required every 2 years and re-inspection would be required between the 10th and 14th month following issuance of a Certificate of Inspection.
5) Requirements for the initial and periodic inspections and tests of the cargo containment system, cargo and process piping, and hull heating and cold spots.