GAS FUELLED ENGINE INSTALLATIONS

Transcription

1 RULES FOR CLASSICATION OF SHIPS / HIGH SPEED, LIGHT CRAFT AND NAVAL SURFACE CRAFT NEWBUILDINGS SPECIAL EQUIPMENT AND SYSTEMS ADDITIONAL CLASS PART 6 CHTER 13 GAS FUELLED ENGINE INSTALLATIONS JANUARY 2010 CONTENTS PAGE Sec. 1 General Requirements... 5 Sec. 2 Materials... 9 Sec. 3 Arrangement and System Design Sec. 4 Fire Safety Sec. 5 Electrical Systems Sec. 6 Control, Monitoring and Safety Systems Sec. 7 Compressors and Gas Engines Sec. 8 Manufacture, Workmanship and Testing Veritasveien 1, NO-1322 Høvik, Norway Tel.: Fax:

2 CHANGES IN THE RULES General The present edition of the rules includes additions and amendments approved by the Board as of December 2009, and supersedes the January 2007 edition of the same chapter. The rule changes come into force as indicated below. This chapter is valid until superseded by a revised chapter. Supplements will not be issued except for an updated list of minor amendments and corrections presented in Pt.0 Ch.1 Sec.3. Pt.0 Ch.1 is normally revised in January and July each year. Revised chapters will be forwarded to all subscribers to the rules. Buyers of reprints are advised to check the updated list of rule chapters printed Pt.0 Ch.1 Sec.1 to ensure that the chapter is current. Main changes coming into force 1 July 2010 General Interim Guidelines on Safety for Natural Gas-fuelled Engine Installations in Ships have been approved by IMO MSC.285(86) in June The Rules are aligned with these guidelines. Sec.1 General Requirements A documentation requirement for an overall design philosophy is added. Documentation requirements changed to new format. Some definitions updated in line with Interim Guidelines, changes later in document or general improvement. The product certification requirements for valves are updated to be stricter and in line with Rules for Classification of Ships, Pt.5 Ch.5 for low temperature gas or high pressure gas. Sec.2 Materials Some material requirements are updated to better accommodate materials for CNG tanks, and to make the requirements less strict for low pressure and piping with working temperature above zero. Sec.3 Arrangement and System Design The requirements with regard to entrance to and location of compressor rooms are changed to be in line with Interim Guidelines. Compressor rooms can now be accepted below open deck if arranged as tank rooms, and with entrance directly from open deck or through air locks. D100 General has got new content, and now contains a new requirement to give a better overall control with the design of redundant fuel supply and machinery installations due to shut down actions after gas leakages. The previous D100 General is moved to D200 and renamed Engine room configuration options. A new subsection E Gas Supply System General is added, collecting requirements from Sec.3 and Sec.6 regarding fuel supply system arrangement. The requirement for excess flow shut down in Sec.6 D is re-written for better clarity and to make the different alternative solutions clearer, and moved to Sec.3 together with the rest of D101 to D106. The design requirement for pipe duct is slightly revised to allow for an alternative calculation method for design pressure. New requirements for emptying, inerting and gas freeing of gas tanks added in line with Interim Guidelines. The wording for location of tanks is changed from above and below deck to on open deck and in enclosed spaces. The requirement for location of tanks on open deck away from ship side is updated to be in line with the requirements for tanks located in enclosed spaces, hence opening for a location closer to the ship side for some ship types. Left out by mistake in previous revisions. The requirements for location of CNG tanks and other gas tanks with pressure above 10 bar in enclosed spaces are updated in line with the Interim Guidelines. Now CNG can be located in enclosed spaces on certain conditions outlined in the rules. The tank room arrangement requirement is slightly updated better accommodate the arrangement with a tank room arranged as a cold box welded to the outer shell of a double tank. In line with Interim Guidelines. The bunkering station requirements are updated to better include CNG systems in addition to LNG systems, in line with Interim Guidelines. The ventilation requirement for tank room is modified to allow for other alternative means for explosion prevention as an alternative to ventilation, in line with Interim Guidelines. The ventilation requirement for ESD protected engine rooms is modified to allow for a lower rate in normal operation, in line with already enforced practice, and with Interim Guidelines. Redundancy requirement for ventilation of pump and compressor room is added, in line with Interim Guidelines. A new requirement containing safety requirements for spaces containing nitrogen generators or storage tanks is added. This is in line with similar requirements for chemical carriers and supply ships where nitrogen installations are common. We have rearranged some of the requirements, by adding a new Sub-section, and moving requirements from Sec.3 G and Sec.6 D for better clarity of the rules. Sec.4 Fire Safety Some updates are done to bring the rules in line with similar requirements in the Interim Guidelines. Some requirements are moved to Sec.6. Sec.5 Electrical Systems Some updates are done to align with similar requirements in the Interim Guidelines. The main reason for these updates is to better include also CNG tank systems. Sec.6 Control, Monitoring and Safety Systems Some minor changes are done to align with the Interim Guidelines. Some requirements are moved to Sec.3, and some are moved from Sec.3 and 4 to this section. Figures 1 and 2 are moved to Sec.3 and Table D1 is moved to B3. The structure of the section is improved. Corrections and Clarifications In addition to the above stated rule requirements, a number of corrections and clarifications have been made to the existing rule text. Comments to the rules may be sent by to rules@dnv.com For subscription orders or information about subscription terms, please use distribution@dnv.com Comprehensive information about DNV and the Society's services is found at the Web site Det Norske Veritas Computer Typesetting (Adobe FrameMaker) by Det Norske Veritas Printed in Norway If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation to such person for his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided that the maximum compensation shall never exceed USD 2 million. In this provision "Det Norske Veritas" shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalf of Det Norske Veritas.

3 Pt.6 Ch.13 Contents Page 3 CONTENTS SEC. 1 GENERAL REQUIREMENTS... 5 A. Classification...5 A 100 Application...5 A 200 Class notation...5 A 300 Survey extent...5 B. Definitions...5 B 100 Terms...5 C. Documentation...6 C 100 Plans and particulars...6 D. Certification...8 D 100 Gas engines...8 D 200 Pressure vessels...8 D 300 Valves...8 D 400 Pumps and compressors...8 E. Operation and Maintenance Manuals...8 E 100 Contents...8 SEC. 2 MATERIALS... 9 A. General...9 A 100 Material requirements...9 SEC. 3 ARRANGEMENT AND SYSTEM DESIGN.. 10 A. Location and Separation of Spaces...10 A 100 Gas compressor room...10 A 200 Engine rooms...10 A 300 Tank rooms...10 B. Arrangement of Entrances and Other Openings...10 B 100 General...10 C. General Gas Pipe Design...10 C 100 General...10 D. System Configuration...11 D 100 General...11 D 200 Engine room configuration options...11 D 300 Inherently gas safe machinery spaces...11 D 400 ESD protected machinery spaces...11 E. Gas supply system arrangement...11 E 100 Gas supply system general...11 E 200 Distribution outside of machinery spaces...13 F. Gas Supply System in Machinery Spaces...13 F 100 Gas supply system for inherently gas safe machinery spaces...13 F 200 Gas supply system for ESD protected machinery spaces...13 G. Gas Fuel Storage Tanks...14 G 100 Liquefied gas storage tanks...14 G 200 Compressed gas storage tanks...14 G 300 Storage on open deck...14 G 400 Storage in enclosed spaces...14 H. Fuel Bunkering System...14 H 100 Fuel bunkering station...14 H 200 Bunkering system...15 I. Ventilation Systems...15 I 100 General...15 I 200 Non-hazardous spaces...15 I 300 Gas tank room...15 I 400 Engine room...15 I 500 Pump and compressor rooms...15 J. Nitrogen Installations...16 J 100 Nitrogen installation spaces...16 SEC. 4 RE SAFETY A. General A 100 General...17 B. Fire Protection B 100 Construction...17 C. Fire Extinction C 100 Fire main...17 C 200 Water spray systems...17 C 300 Dry chemical powder fire extinguishing system...17 D. Fire Detection and Alarm Systems D 100 Detection...17 E. Spark arresters E 100 General...17 SEC. 5 ELECTRICAL SYSTEMS A. General A 100 General...18 B. Area classification B 100 General...18 B 200 Definition of zones...18 C. Inspection and testing C 100 General...18 D. Maintenance D 100 General...19 SEC. 6 CONTROL, MONITORING AND SAFETY SYSTEMS A. General A 100 Introduction...20 B. Monitoring B 100 Gas tank monitoring...20 B 200 Gas compressor monitoring...20 B 300 Gas engine monitoring...20 B 400 Gas supply system safety functions...21 B 500 Ventilation monitoring...22 C. Gas Detection C 100 Locations...22 D. Signboards D 100 General...22 SEC. 7 COMPRESSORS AND GAS ENGINES A. Gas Compressors A 100 General...24 A 200 Vibrations...24 B. Gas Engine Design B 100 General...24 B 200 Functional requirements dual fuel engines...24 B 300 Functional requirements gas-only engines...24 B 400 Design of on-engines piping on gas-only engines...24 SEC. 8 MANUFACTURE, WORKMANSHIP AND TESTING A. Gas Tanks A 100 Manufacture and testing...25 B. Gas Piping Systems B 100 Gas pipes...25 B 200 Ducting...25 B 300 Valves...25 B 400 Expansion bellows...25

4 Pt.6 Ch.13 Contents Page 4

5 Pt.6 Ch.13 Sec.1 Page 5 SECTION 1 GENERAL REQUIREMENTS A. Classification A 100 Application 101 The rules in this chapter apply to internal combustion engine installations in ships. Application of the ESD concept for LNG carriers requires acceptance by the Flag Administration under the equivalency clause in the IGC Code. The engines may be either single fuel engines or dual fuel engines, and the gas may be in gaseous or liquid state. Guidance note 1: The use of gas as fuel in ships other than LNG carriers is not covered by international conventions and such installations will need additional acceptance by flag authorities. Guidance note 2: Requirements not relevant for LNG carriers are shown in bold italic text. 102 The rules are applicable for installations where natural gas is used as fuel. If other gases are used as fuel special considerations will have to be done, and additional requirements may be relevant. A 200 Class notation 201 Ships built with machinery satisfying the requirements in this chapter will be given class notation: GAS FUELLED. A 300 Survey extent 301 Survey requirements for ships with the class notation GAS FUELLED are given in the Rules for Classification of Ships, Pt.7 Ch.1 Sec.2 A and C, Pt.7 Ch.1 Sec.3 C and Pt.7 Ch.1 Sec.4 C. B. Definitions B 100 Terms 101 Accommodation spaces: See the Rules for Classification of Ships, Pt.4 Ch Control stations: See the Rules for Classification of Ships, Pt.4 Ch.10. Guidance note: This does not include special fire control equipment that can be most practically located in the cargo area (if the vessel is a cargo ship). 103 Double block and bleed valve is a set of three automatic valves located at the fuel supply to each of the gas engines. Two of these valves shall be in series in the gas fuel pipe to the consuming equipment. The third valve shall be in a pipe that vents to a safe location in the open air, that portion of the gas fuel piping that is between the two valves in series. Alternatively, the function of one of the valves in series and the ventilation valve can be incorporated into one valve body, so arranged that the flow to the gas utilisation unit will be blocked and the ventilation opened. 104 Dual fuel engines are in this context engines that can burn gaseous and liquid fuel simultaneously and in a wide variety of proportions, or can operate successively on oil fuel and gas. 105 ESD means emergency shutdown. 106 Enclosed space means any space within which, in the absence of artificial ventilation, the ventilation will be limited and any explosive atmosphere will not be dispersed naturally. Guidance note: See also definition in IEC : Engine room is in this chapter used for machinery spaces containing gas fuelled engines. 108 Gas is defined as a fluid having a vapour pressure exceeding 2.8 bar absolute at a temperature of 37.8 C. 109 Hazardous area Area in which an explosive gas atmosphere or a flammable gas with a flash point below 60 C is or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of electrical apparatus. Hazardous areas are divided into Zone 0, 1 and 2 as defined below and according to the area classification specified in Sec.5 B. Zone 0 Area in which an explosive gas atmosphere or a flammable gas with a flash point below 60 C is present continuously or is present for long periods Zone 1 Area in which an explosive gas atmosphere or a flammable gas with a flash point below 60 C is likely to occur in normal operation Zone 2 Area in which an explosive gas atmosphere or a flammable gas with a flash point below 60 C is not likely to occur in normal operation and, if it does occur, is likely to do so only infrequently and will exist for a short period only. Guidance note: The definition of hazardous area is only related to the risk of explosion. In this context, health, safety and environmental issues, i.e. toxicity, is not considered. 110 Non-hazardous area An area not considered to be hazardous, i.e. gas safe, provided certain conditions are being met. 111 Sources of release are valves or detachable pipe joints in the fuel gas system. Also compressors and seals of pumps in the fuel gas system are regarded as sources of release. 112 High-pressure piping is in this context piping with maximum working pressure above 10 bar. 113 LEL is lower explosion limit. 114 Main tank valve is a remote operated valve on the gas outlet from a gas storage tank, located as close to the tank outlet point as possible. 115 Master gas fuel valve is an automatic valve in the gas supply line to each engine located outside the engine room and as close to the gas heater (if fitted) as possible. 116 Open deck means a deck that is open at one or both ends and equipped with adequate natural ventilation that is effective

6 Pt.6 Ch.13 Sec.1 Page 6 over the entire length of the deck through permanent openings distributed in the side panels or in the deck above. 117 Passenger areas are those spaces that are provided for the accommodation and use of passengers, excluding baggage, store, provision and mail rooms. 118 Semi-enclosed spaces are locations where natural conditions of ventilation are notably different from those on open decks due to the presence of structures such as roofs, wind breakers and bulkheads and which are so arranged that dispersion of gas may not occur. 119 Service spaces are spaces outside the cargo area used for galleys, pantries containing cooking appliances, lockers, mail and specie rooms, store rooms, workshops other than those forming part of the machinery spaces and similar spaces and trunks to such spaces. 120 Single gas fuel system is a power generating system consisting of gas-only engines, not able to switch over to fuel oil running. 121 Tank room means the gastight space surrounding the bunker tank, containing all tank connections and all tank valves. C. Documentation C 100 Plans and particulars 101 Documentation shall be submitted as required by Table C1. Table C1 Documentation requirements Object Documentation type Additional description Gas installation general Z050 Design Philosophy Z010 General arrangement plan A document describing the propulsion design philosophy for the ship according to Pt.4 Ch.1 Table B1. It shall include information on the machinery configuration, engine room arrangements, fuel arrangements, shut down philosophy, redundancy considerations etc. and shall be submitted before other documentation, to give support at approval of other documents. Shall give location of: machinery and boiler spaces, accommodation, service and control station spaces gas tanks and gas containment systems gas pump and compressor rooms gas bunkering pipes with shore connections tank hatches, ventilation pipes and any other openings to the gas tanks ventilating pipes, doors and openings to gas pump rooms, compressor rooms and other hazardous areas entrances, air inlets and openings to accommodation, service and control station spaces For approval () or information () G080 Hazardous area classification drawing Z140 Test procedure for quay For the safety functions of the gas installation in the form and sea trial of a cause and effect diagram Z160 Operational manual Shall contain information as outlined in E100 Gas containment C020 Assembly or arrangement drawing C030 Detailed drawing Gas tank Support and stays Secondary barrier Tank insulation C040 Design analysis Specification of design loads and structural analysis of gas tanks A complete stress analysis for independent tanks type B and type C C050 Non-destructive testing (NDT) plan Including Information about strength and tightness testing specification of stress relieving procedures for independent tanks type C (thermal or mechanical) M060 Welding procedures M010 Material specifications Gas tanks and connected pipes Cooling down procedure Z250 Procedure gas tank Marking plate gas tank C030 - Detailed drawing

7 Pt.6 Ch.13 Sec.1 Page 7 Table C1 Documentation requirements (Continued) Object Documentation type Additional description Gas piping system S010 Piping diagram Gas piping including ventilation lines for safety relief valves or similar piping, also to include ducts for gas pipes S090 Specification offsets, Drawings and specifications of offsets, loops, bends and loops and bends mechanical expansion joints, such as bellows, slip joints (only inside tank) or similar means in the gas piping S060 Pipe routing sketch S080 Thermal stress analysis Complete stress analysis of piping system when design temperature is below minus 110 C S090 Specification of valves, flanges and fittings Z280 Type approval certificate C050 Non-destructive testing (NDT) plan M010 Material specifications M060 Welding procedures Z140 Test procedure for quay and sea trial Drawings and specifications of flanges, valves and other fittings in the gas piping system. For valves intended for piping systems with a design temperature below minus 55 C, documentation for leak test and functional test at design temperature (type test) is required Documentation of type tests for expansion components in the gas piping system Non destructive testing Specification of pressure tests (structural and tightness tests) of gas piping Specification of post-weld heat treatment Functional tests of all piping systems including valves, fittings and associated equipment for handling gas (liquid or vapour) For approval () or information () Pipe insulation S090 Specification Drawings and specifications of insulation for low temperature C030 Detailed drawing piping where such insulation is installed Electrical bonding S090 Specification Specification of electrical bonding of piping Cooling system S010 Piping diagram Cooling water system in connection with gas fuel system, if fitted. Heating system S010 Piping diagram Heating water system in connection with gas fuel system, if fitted. Tank safety relief S090 Specification of piping, Drawings and specifications for safety relief valves and valves valves, flanges and fittings pressure/vacuum relief valves and associated ventilation piping S030 Capacity analysis Calculation of required gas tank relief valve capacity, including back pressure Gas mast Z030 System arrangement plan Gas outlet from tank safety relief valves, location and details Air locks Z020 Local arrangement plan If fitted. Location and construction details, incl. alarm equipment. Gastight bulkhead penetration C030 Detailed drawing If fitted / Ventilation system for hazardous spaces V010 Ducting diagram V050 Duct routing sketch C030 Detailed drawing Arrangement of ventilation ducts for spaces containing gas installations, like gas pipe ducts led through enclosed spaces, storage tanks below deck Arrangements and specifications of mechanical ventilation systems in spaces covering gas fuel system, giving capacity and location of fans and their motors. Drawings and material specifications of rotating parts and casings for fans and portable ventilators Hull protection Z020 Local arrangement plan Drawings and specifications of protection of hull steel beneath liquid piping where liquid leakage may be anticipated, such as at shore connections and at pump seals Gas freeing and S010 Piping system Arrangement and specifications of piping systems for gas purging of tanks freeing and purging of gas tanks Bilge system S010 Piping system Bilge and drainage arrangements in gas pump rooms, compressor rooms, tank rooms Fixed gas detection system Exhaust gas system Z100 Specification Z020 Local arrangement S060 Pipe routing sketch Location of detectors, alarm devices and call points and cable routing layout drawing

8 Pt.6 Ch.13 Sec.1 Page 8 Table C1 Documentation requirements (Continued) Object Documentation type Additional description Water spray system G200 Fixed fire extinguishing system documentation If fitted. Arrangement and specification of water spray system, including pipes, valves, nozzles and fittings Fire insulation G060 Structural fire protection drawing Dry chemical Z020 Local arrangement plan Arrangement and specification of dry chemical powder power system installation Fire detection Z020 Local arrangement plan Fire detection system for storage tank and ventilation trunk Electrical Z030 System arrangement Electrical equipment in hazardous areas equipment in plan hazardous areas Gas engine Control and monitoring E170 Electrical schematic drawing E090 Table of Ex-installation Z180 Maintenance manual Z071 Failure mode and effect analysis Single line diagrams for all intrinsically safe circuits, for each circuit including data for verification of the compatibility between the barrier and the field components Table of explosion protected equipment with reference to drawings together with certificates Maintenance manual as specified in Sec.5 D, for electrical installations in hazardous areas shall be submitted A failure mode and effect analysis (FMEA) examining all possible faults affecting the combustion process in the gas engines The following control and monitoring systems shall be approved by the Society: gas detection system gas tank monitoring system gas compressors control and monitoring system gas engines control and monitoring system. For requirements to documentation, see Pt.4 Ch.9. For approval () or information () D. Certification D 100 Gas engines 101 Gas engines are in addition to the requirements in this chapter shall be certified in accordance with Pt.4 Ch.3. D 200 Pressure vessels 201 Pressure vessels, which under normal operations will contain gas in the liquid and/or gaseous state, shall be certified as class I pressure vessels in accordance with Pt.4 Ch.7. D 300 Valves 301 For valves used in high pressure gas systems or systems with working temperature below 0 C product certification as given in Rules for Classification of Ships, Pt.5 Ch.5 Sec.6 H is required. For valves used in gas piping systems with low pressure and temperature above 0 C product certification is required, as given in the Rules for Classification of Ships, Pt.4 Ch.6. D 400 Pumps and compressors 401 Pumps and compressors in gas systems shall be delivered with the Society s product certificate. 402 For general requirements and in regard to testing of pumps: See the Rules for Classification of Ships, Pt.4 Ch For general requirements and with regard to testing of compressors: See Pt.4 Ch.5. E. Operation and Maintenance Manuals E 100 Contents 101 An operation manual shall include: bunkering procedure gas freeing and inerting procedures normal operation procedures of the gas system emergency operation procedures of the gas system. 102 A plan for systematic maintenance and function testing shall be kept onboard showing in detail how components and systems shall be tested and what shall be observed during the tests. Columns showing test dates and verification of tests carried out shall be included. The plan shall include: all instrumentation, automation and control systems affecting the gas supply system test intervals to reflect the consequences of failure involving a particular system. Functional testing of critical alarms should not exceed 3 months intervals. Normally the longest intervals shall not surpass 12 months. The plan should be included in the plan required for the class notation E0. Guidance note: Critical alarms are defined as low lubricating oil pressure alarms for rotating machinery.

9 Pt.6 Ch.13 Sec.2 Page 9 SECTION 2 MATERIALS A. General A 100 Material requirements 101 Materials are in general to be in accordance with the requirements in Pt Materials used in gas tanks, gas piping, process pressure vessels and other components in contact with gas with high pressure or a working temperature below 0 C shall be in accordance with the Rules for Classification of Ships, Pt.5 Ch.5 Sec.2 D. For piping see the Rules for Classification of Ships, Pt.5 Ch.5 Sec.6 C200. For CNG tanks, the use of materials not covered by Rules for Classification of Ships, Pt.5 Ch.5 may be specially considered and approved by the Society. 103 The materials used in gas piping systems with high pressure or temperature below 0 C shall be furnished with documentation in accordance with the Rules for Classification of Ships, Pt.5 Ch.5 Sec.2 Table E1. The materials used in gas piping systems with low pressure and temperature above 0 C shall be furnished with documentation in accordance with the Rules for Classification of Ships, Pt.4 Ch.6 Sec.2 Table A2. Gas piping is pertaining to the same pipe class as fuel oil piping in Pt.4 Ch.6 Sec.1 Table B1. For the definition of material documentation see the Rules for Classification of Ships, Pt.1 Ch.1 Sec The outer pipe in inherently safe engine room spaces with high pressure gas in the inner pipe is as least required to fulfil the material requirements for pipe materials with design temperature down to -55 in the Rules for Classification of Ships, Pt.5 Ch.5 Sec.2 Table D The outer pipe or duct around gas pipes with liquid gas shall be made of cold resistant steel unless it is efficiently protected from possible leakages from the inner pipe.

10 Pt.6 Ch.13 Sec.3 Page 10 SECTION 3 ARRANGEMENT AND SYSTEM DESIGN A. Location and Separation of Spaces A 100 Gas compressor room 101 Compressor rooms, if arranged, shall be located on open deck, unless those rooms are arranged and fitted in accordance with the requirements of this Rule chapter for tank rooms. 102 Where compressors are driven by shafting passing through a bulkhead or deck, the bulkhead penetration shall be of gas tight type. A 200 Engine rooms 201 When more than one engine room is required and these rooms are separated by a single bulkhead, the bulkhead shall have sufficient strength to withstand a local gas explosion. A strength standard of the bulkhead corresponding to that of a watertight bulkhead is considered adequate. 202 Engine rooms of the ESD protected type shall have as simple geometrical shape as possible. A 300 Tank rooms 301 Tank rooms boundaries shall be gas tight. 302 The tank room shall not be located adjacent to machinery spaces of category A. If the separation is by means of a cofferdam then additional insulation to class A-60 standard shall be fitted. B. Arrangement of Entrances and Other Openings B 100 General 101 Direct access through doors, gastight or otherwise, shall generally not be permitted from a non hazardous space to a hazardous space. Where such openings are necessary for operational reasons, an air lock which complies with the requirements of Rules for Classification of Ships, Pt.5 Ch.5 Sec.3 C300 shall be provided. 102 If the compressor room is approved located below open deck the room shall have an independent access direct from the open deck. Where a separate access from deck is not practicable, an air lock which complies with the requirements of Pt.5 Ch.5 Sec.3 C300 shall be provided. 103 The tank room entrance shall be arranged with a sill height of at least 300 mm. 104 Access to the tank room is as far as practicable to be independent and direct from open deck. If the tank room is only partially covering the tank, this requirement shall be applied to the room surrounding the tank, and where the opening to the tank room is located. Where a separate access from deck is not practicable, an air lock which complies with the requirements of Rules for Classification of Ships, Pt.5 Ch.5 Sec.3 C300 shall be provided. The access trunk shall be fitted with separate ventilation. The tank room shall not be open for entry during normal operation of the gas system. 105 An engine room containing gas engines shall have at least two completely independent exits. However, if the engine room is very small, this requirement can be waived after special consideration by the Society. 106 If the access to an engine room of ESD protected type is from another enclosed space in the ship, the entrances shall be arranged with self-closing doors. Audible and visible alarm shall sound at a permanently manned location if the door is open continuously for more than 1 minute. As an alternative an arrangement with two self-closing doors in series can be approved. C. General Gas Pipe Design C 100 General 101 Gas pipes shall in general comply with the applicable parts of the Rules for Classification of Ships, Pt.5 Ch.5 Sec Gas piping shall not be located less than 760 mm from the ship's side. 103 An arrangement for purging gas bunkering lines and supply lines (only up to the double block and bleed valves if these are located close to the engine) with nitrogen shall be provided. 104 The gas piping system shall be installed with sufficient flexibility. Bellows will not be accepted in enclosed spaces. 105 Gas pipes shall be colour marked based on a recognized standard. Guidance note: Refer to EN ISO 14726:2008 Ships and marine technology - Identification colours for the content of piping systems. 106 If the fuel gas contains heavier components that may condense in the system, knock out drums or equivalent means for collecting the liquid shall be fitted. 107 High pressure gas piping systems shall have sufficient constructive strength. This shall be confirmed by carrying out stress analysis and taking into account: stresses due to the weight of the piping system acceleration loads when significant internal pressure and loads induced by hog and sag of the ship. [IACS UR M59] Guidance note: Significant acceleration loads is in this context acceleration loads that give a stress equal to more than 20% of the stress from the internal pressure in the pipe 108 All valves and expansion joints used in high pressure gas systems shall be of an approved type. [IACS UR M59] 109 All gas piping and tanks shall be electrically bonded to the ship's hull. Bonding straps across stainless steel flanges with bolts and nuts of stainless steel are not required. If carbonmanganese steel is not fitted with bonding straps across the flanges, it shall be checked for electric bonding. The electrical bonding is sufficient, when the electrical resistance between piping and the hull does not exceed 10 6 Ohm. Gas piping sections of piping components which are not permanently connected to the hull by permanent piping connections, or where such connections are removable e.g. for removal of spool pieces, shall be electrically bonded to the hull by special bonding straps.

11 Pt.6 Ch.13 Sec.3 Page 11 Guidance note: The value of resistance 10 6 Ohm may be achieved without the use of bonding straps where gas piping systems and equipment are directly, or via their supports, either welded or bolted to the hull of the ship. It will be generally necessary initially to achieve a resistance value below 106 Ohm, to allow for deterioration in service. 110 Gas piping shall be protected against mechanical damage. D. System Configuration D 100 General 101 The propulsion and fuel supply system shall be so designed that the remaining power for propulsion and power generation after any gas leakage with following safety actions shall be in accordance with the requirements for remaining power and main functions after single failure of an active component in Rules for Classification of Ships, Pt.4 Ch.1. D 200 Engine room configuration options 201 Two alternative system configurations may be accepted: i) Inherently gas safe machinery spaces: Arrangements in machinery spaces are such that the spaces are considered gas safe under all conditions, normal as well as abnormal conditions i.e. inherently gas safe. ii) ESD protected machinery spaces: Arrangements in machinery spaces are such that the spaces are considered nonhazardous under normal conditions, but under certain abnormal conditions may have the potential to become gas hazardous. In the event of abnormal conditions involving gas hazards, emergency shutdown (ESD) of non-safe equipment (ignition sources) and machinery shall be automatically executed while equipment or machinery in use or active during these conditions shall be of explosion protected design. D 300 Inherently gas safe machinery spaces 301 All gas supply piping within machinery space boundaries must be enclosed in a gas tight enclosure, i.e. double wall piping or ducting. 302 For low pressure gas systems ventilation inlet openings for the double wall piping or duct can be accepted located in the engine room on the condition that a gas detection system is fitted in the engine room. D 400 ESD protected machinery spaces 401 Gas supply piping within machinery spaces may be accepted without a gas tight external enclosure on the following conditions: a) Engines for generating propulsion power and electric power shall be located in two or more engine rooms not having any common boundaries unless it can be documented that the common boundary can withstand an explosion in one of the rooms. Distribution of engines between the different engine rooms shall be such that in the case of shutdown of fuel supply to any one engine room it must be possible to maintain at least 40% of the propulsion power plus normal electrical power supply for sea going services. Incinerators, inert gas generators or other oil fired boilers shall not be located within an ESD protected machinery space. b) Pressure in gas supply lines within machinery spaces to be less than 10 bar. c) A gas detection system arranged to automatically shutdown the gas supply (also oil fuel supply if dual fuel) and disconnect all non-explosion protected equipment or installations shall be fitted. E. Gas supply system arrangement E 100 Gas supply system general 101 For single fuel installations (gas only) the fuel storage shall be divided between two or more tanks of approximately equal size. The tanks shall be located in separate compartments. 102 Each gas storage tank shall be provided with a tank valve capable of being remote operated. The valve shall be located as close to the tank outlet as possible. 103 The main supply lines for gas to each engine room shall be equipped with a manually operated stop valve and an automatically operated master gas fuel valve coupled in series or a combined manually and automatically operated stop valve. The valves shall be situated in the part of the piping that is outside engine room, and placed as near as possible to the installation for heating the gas, if fitted. The master gas fuel valve is automatically to cut off the gas supply as given in Sec.6 Table B3. The automatic master gas fuel valve shall be operable from a reasonable number of places in the engine room, from a room outside the engine room and from the bridge. 104 Each gas utilisation unit shall be provided with a set of double block and bleed valves. These valves shall be arranged so that when automatic shutdown is initiated as given in Sec.6 Table B3, this will cause the two gas fuel valves that are in series to close automatically and the ventilation valve to open automatically. The two block valves shall be of the failto-close type, while the ventilation valve shall be fail-to-open. The double block and bleed valves are also to be used for normal stop of the engine. 105 In cases where the master gas fuel valve is automatically shutdown, a ventilation valve, that will ventilate the pipe piece between the master gas valve and the double block and bleed valve, shall open. For high-pressure systems the pipe pieces between the double block and bleed valve and the gas injection valves, shall be automatically vented. See Fig.1 and Fig.2. For high-pressure systems the ventilation valves shall open at normal stop of engine.

12 Pt.6 Ch.13 Sec.3 Page 12 Fig. 1 Alternative supply valve arrangements for high-pressure installations (single engine or separate master valve arrangement) Fig. 2 Alternative supply valve arrangements for high-pressure installations (multi engine installation)

13 Pt.6 Ch.13 Sec.3 Page There shall be one manually operated shutdown valve in the gas supply line to each engine to assure safe isolation during maintenance on the engine. 107 For one-engine installations and multi-engine installations where a separate master valve is provided for each branch the master gas fuel valve and the double block and bleed valve functions can be combined. Examples for high-pressure installations are shown in Fig.1 and Fig In the main supply gas line to each engine located in an ESD protected machinery space, and in each gas supply line to high pressure installations means shall be provided for rapid detection of a rupture in the gas line in the engine room. When rupture is detected a valve shall be automatically shut off. This valve shall be located in the gas supply line before it enters the engine room or as close as possible to the point of entry inside the engine room, and it can be a separate valve or combined with other functions, e.g. the master valve. Acceptable means of detection are e.g.: an orifice or flow fuse detecting excess flow located close to the point of entry to the engine room; a combined excess flow detector with automatic shut off valve located close to the point of entry to the engine room; a low pressure detector located as close as possible to the engine inlet. Guidance note: The shutdown should be time delayed to prevent shutdown due to transient load variations. E 200 Distribution outside of machinery spaces 201 Gas fuel piping shall not be lead through accommodation spaces, service spaces or control stations. 202 Where gas pipes pass through enclosed spaces in the ship, they shall be enclosed in a duct. This duct shall be mechanically underpressure ventilated with 30 air changes per hour, and gas detection as required in Sec.6 shall be provided. 203 The duct shall be dimensioned according to F103 and F The ventilation inlet for the duct is always to be located in open air, away from ignition sources. 205 High-pressure gas lines outside the engine room spaces shall be installed and protected so as to minimise the risk of injury to personnel in case of rupture. F. Gas Supply System in Machinery Spaces F 100 Gas supply system for inherently gas safe machinery spaces 101 Gas supply lines passing through enclosed spaces shall be completely enclosed by a double pipe or duct. This double pipe or duct shall fulfil one of the following: a) The gas piping shall be a double wall piping system with the gas fuel contained in the inner pipe. The space between the concentric pipes shall be pressurised with inert gas at a pressure greater than the gas fuel pressure. Suitable alarms shall be provided to indicate a loss of inert gas pressure between the pipes. When the inner pipe contains high pressure gas the system shall be so arranged so that the pipe between the master gas valve and the engine is automatically purged with inert gas when the master gas valve is closed. [IACS UR M59] b) The gas fuel piping shall be installed within a ventilated pipe or duct. The air space between the gas fuel piping and the wall of the outer pipe or duct shall be equipped with mechanical underpressure ventilation having a capacity of at least 30 air changes per hour. This ventilation capacity can be reduced to 10 air changes per hour provided automatic filling of the duct with nitrogen upon detection of gas is arranged for. The fan motors shall be placed outside the ventilated pipe or duct. The ventilation outlet shall be covered by a protection screen and placed in a position where no flammable gas-air mixture may be ignited. 102 The connecting of gas piping and ducting to the gas injection valves must be so as to provide complete coverage by the ducting. The arrangement must facilitate replacement and or overhaul of injection valves and cylinder covers. Double ducting is also required for gas pipes on the engine and up to where the gas is supplied into the combustion chamber. Guidance note: If gas is supplied into the air inlet pipe on a low pressure engine, double ducting may be omitted on the air inlet pipe on the condition that a gas detector is fitted above the engine. 103 For high-pressure piping the design pressure of the ducting shall be taken as the higher of the following: the maximum built up pressure: static pressure in way of the rupture resulting from the gas flowing in the annular space local instantaneous peak pressure in way of the rupture p*: this pressure shall be taken as the critical pressure and is given by the following expression: k k 1 p = p k + 1 p 0 = maximum working pressure of the inner pipe k = C p /C v constant pressure specific heat divided by the constant volume specific heat k = 1.31 for CH 4 The tangential membrane stress of a straight pipe shall not exceed the tensile strength divided by 1.5 (R m /1.5) when subjected to the above pressure. The pressure ratings of all other piping components shall reflect the same level of strength as straight pipes. As an alternative to using the peak pressure from the above formula, the peak pressure found from representative tests can be used. Test reports must then be submitted. 104 For low pressure piping the duct shall be dimensioned for a design pressure not less than the maximum working pressure of the gas pipes. As an alternative the calculated maximum built up pressure in the duct in the case of a pipe rupture when ventilation is not running may be approved used for dimensioning of the duct. 105 The arrangement and installation of the high-pressure gas piping must provide the necessary flexibility for the gas supply piping to accommodate the oscillating movements of the engine, without running the risk of fatigue problems. The length and configuration of the branch lines are important factors in this regard. F 200 Gas supply system for ESD protected machinery spaces 201 The pressure in the gas supply system shall not exceed 10 bar. 202 The gas supply lines shall have a design pressure not less than 10 bar.

14 Pt.6 Ch.13 Sec.3 Page 14 G. Gas Fuel Storage Tanks G 100 Liquefied gas storage tanks 101 The storage tank used for liquefied gas shall be an independent tank designed in accordance with the Rules for Classification of Ships, Pt.5 Ch.5 Sec.5 I. 102 Pipe connections to the tank shall be in accordance with the Rules for Classification of Ships, Pt.5 Ch.5 Sec.6 C303 to C307. However, connections below the lowest liquid level may be accepted after special consideration by the Society. 103 Pressure relief valves as required in the Rules for Classification of Ships, Pt.5 Ch.5 Sec.9 B200 shall be fitted. 104 The outlet from the pressure relief valves shall be located at least B/3 or 6 m, whichever is greater, above the weather deck and 6 m above the working area and gangways, where B is the greatest moulded breadth of the ship in metres. The outlets shall be located at least 10 m from the nearest: air intake, air outlet or opening to accommodation, service and control spaces, or other non hazardous spaces exhaust outlet from machinery or from furnace installation. For small ships and ship types where the operation limits the possible location of the outlet, smaller height and distances than given above may be accepted. 105 Storage tanks for liquid gas with vapour pressure above the design pressure at 45 C shall be fitted with efficient insulation. 106 Storage tanks for liquid gas shall not be filled to more than 98% full at the reference temperature, where the reference temperature is as defined in the Rules for Classification of Ships, Pt.5 Ch.5 Sec.17 A105. A filling limit curve for actual filling temperatures shall be prepared from the formula given in the Rules for Classification of Ships, Pt.5 Ch.5 Sec.17 A102. However, when the tank insulation and tank location makes the probability very small for the tank contents to be heated up due to external fire, special considerations can be made to allow a higher filling limit than calculated using the reference temperature, but never above 95%. 107 It shall be possible to empty, inert and purge bunker tanks and associated gas piping systems. Procedures shall be developed in accordance with Rules for Classification of Ships, Pt.5 Ch.5 Sec.9. G 200 Compressed gas storage tanks 201 The storage tanks to be used for compressed gas shall be in accordance with Pt.4 Ch.7 and shall be certified by the Society. 202 Tanks for compressed gas shall be fitted with pressure relief valves with a set point below the design pressure of the tank and with outlet located as required in 104. G 300 Storage on open deck 301 Both gases of the compressed and the liquefied type will be accepted stored on open deck. 302 The storage tanks or tank batteries shall be located at least B/5 from the ship's side. For ships other than passenger ships a tank location closer than B/5 but not less than 760 mm from the ship's side may be accepted. 303 The gas storage tanks or tank batteries and equipment shall be located to assure sufficient natural ventilation, so as to prevent accumulation of escaped gas. 304 Tanks for liquid gas with a connection below the highest liquid level, see 102, shall be fitted with drip trays below the tank of sufficient size to hold the full content of the tank. The material of the drip tray should be stainless steel, and there should be efficient separation or insulation so that the hull or deck structures are not exposed to unacceptable cooling, in case of leakage of liquid gas. G 400 Storage in enclosed spaces 401 Gas in a liquid state with a maximum acceptable working pressure of 10 bar may be stored in enclosed spaces. Storage of compressed gas in enclosed spaces and location of gas tanks with a higher pressure than 10 bar in enclosed spaces is not acceptable unless the following is fulfilled in addition to 404: adequate means are provided to depressurize the tank in case of a fire which can affect the tank; and all surfaces within the tank room are provided with suitable thermal protection against any lost high-pressure gas and resulting condensation unless the bulkheads are designed for the lowest temperature that can arise from gas expansion leakage; and a fixed fire-extinguishing system is installed in the tank room. 402 The gas storage tank(s) shall be located as close as possible to the centreline and: minimum, the lesser of B/5 and 11.5 m from the ship side minimum, the lesser of B/15 and 2 m from the bottom plating not less than 760 mm from the shell plating. For vessels other than passenger vessels a tank location closer than B/5 from the ship side may be accepted and approved by the Society, on a case by case basis. 403 The storage tank and associated valves and piping shall be located in a space designed to act as a secondary barrier, in case of liquid gas leakage. This implies that the material shall be in accordance with the Rules for Classification of Ships, Pt.5 Ch.5 Sec.2 D, for secondary barriers, and that the space shall be designed to withstand the maximum pressure build up. Alternatively, pressure relief venting to a safe location (mast) can be provided. The space shall be capable of containing leakage, and shall be isolated thermally so that the surrounding hull is not exposed to unacceptable cooling, in case of leakage of the liquid gas. This secondary barrier space is in other parts of this chapter called tank room. When the tank is double walled and the outer tank shell is made of cold resistant material, a tank room could be arranged as a box fully welded to the outer shell of the tank, covering all tank connections and valves, but not necessarily all of the outer tank shell. 404 Bilge suctions from the tank room, if provided, shall not be connected to the bilge system for the rest of the ship. H. Fuel Bunkering System H 100 Fuel bunkering station 101 The bunkering station shall be so located that sufficient natural ventilation is provided. Closed or semi-enclosed bunkering stations will be subject to special consideration. 102 Drip trays shall be fitted below liquid gas bunkering connections and where leakage may occur. The drip trays shall be made of stainless steel, and should be drained over the ship's side by a pipe that preferably leads down near the sea. This pipe may be temporarily fitted for bunkering operations. The surrounding hull or deck structures shall not be exposed to unacceptable cooling, in case of leakage of liquid gas. For compressed gas bunkering stations, low temperature steel shielding shall be provided to prevent the possible es-