1 General
1.1 Application
The requirements in this Annex are applicable to natural gas and liquid fuel propulsion gas turbine and piping systems based on the following concepts:
.1 The dual fuel gas turbine is fitted in a gas-tight enclosure to minimize the risk associated with gas leakage, fire and any other hazards associated with the use of gas and oil fuel.
.2 The entire gas turbine enclosure is to encase the gas turbine(s) and, as a minimum, the associated equipment necessary for starting and continuous operation. Even though the internal space of the enclosure will contain the high pressure gas supply line, integrity is achieved by the required ventilation system, gas detection systems and associated safety shutdown systems, as well as the fire protection and firefighting systems which are equivalent to a localized protected space, as per Chapter II-2 of SOLAS 1974 as amended.
.3 Dual fuel gas turbines intended for use as prime movers for propulsion (mechanical drive or generator drive), electric power generation and auxiliary services equipment are to be designed, constructed, tested, certified and installed in accordance with the requirements of this Annex, in addition to the Rules for Steel Ships.
.4 Piping systems serving gas turbine engines, such as fuel oil, gas fuel, lubricating oil, starting air/hydraulic and exhaust gas systems, are to be in compliance with Part VI of the Rules for Steel Ships, Chapters 7 and 9 of the Guidelines.
.5 Gas turbine(s) used for propulsion are to be designed to enable maneuvering from stop to full ahead and vice-versa without a delay using either gas or liquid fuel. When changeover of fuel is activate d during all modes of operation, this should be smooth, without interruptions to the power, as far as practicable.
.6 Both liquid fuel and boil-off gas may be used simultaneously.
.7 Gas turbines are to be capable of operation with a range of gas composition mixtures reflective of that likely to be encountered during service.
2 Arrangement of Dual Fuel Gas Turbines
2.1 General
The dual fuel gas turbine power plant arrangement may consist of the dual fuel gas turbine as the prime mover driving rotating equipment, such as generator(s), a gearbox, couplings and propulsion shafting, together with associated equipment that may include; a starter, governor and fuel control, enclosure, piping, and auxiliary systems and exhaust gas/waste heat recovery boilers and instrumentation, monitoring and control systems.
2.1.1 Where the dual fuel gas turbine prime mover and the minimum associated equipment necessary for its operation are fitted in an enclosure, this enclosure is to be of minimum size, as far as practicable wit hout compromising the accessibility, maintainability and operability. This enclosure is to be provided with effective ventilation and gas detection systems.
3 Plans and Data to be Submitted
3.1 In addition to the plans and particulars required as per 2.2 of the Part IV of the Rules for Steel Ships, the following plans and particulars for dual fuel applications are also to be submitted:
.1 General arrangements showing location of the power plant and individual items of machinery, such as the gas turbine units(s), exhaust gas boilers, turbo generators(s), diesel generators and other associated equipment (such as the GCU, reliquefaction plant and the gas supply line to the consumers)
.2 General arrangement of the gas turbine engine enclosure, including location of the gas detectors, electrical equipment, lighting and ventilation, etc.
.3 Gas fuel manifold arrangement and details, including design pressure and temperatures, operational schematics, material specifications and bill of materials
.4 Enclosure, including size and dimensions, gas tightness, entrance and exits and other openings, such as ventilation intakes and outlets
.5 Ventilation systems details, including inlet cooling air calculations for the enclosure
.6 Fixed gas detection and alarm systems, and associated shut off and shutdown systems
.7 Gas fuel piping systems, including details of pipes and associated components, design pressures and temperatures, operational schematics, flange/joints loadings, material sp ecifications and bill of materials
.8 Gas compressors, with details such as type, size, mechanical components, materials used and details of alarms, indication, shutdown and control system.
.9 Mist separators
.10 Vaporizers
.11 Heat exchangers, including BOG heaters, BOG coolers, etc.
.12 Pressure vessels, including recovery tanks, etc.
.13 Descriptions and schematic diagrams for control and monitoring systems, including set points for abnormal conditions together with control logic for the entire power plant and individual items in the systems.
.14 Details of the electrical equipment in the turbine engine enclosure
.15 Failure Modes and Effects Analysis (FMEA) to determine possible failures and their effects in the safe operation of the dual fuel gas turbine
.16 Electric bonding (earthing) arrangement
.17 Emergency shutdown arrangements
CR Classification Society
.18 Operating and maintenance instruction manuals
.19 Schematic diagram showing gas and fuel supply lines from the source to the consumers for the entire power plant system
.20 Forced boil-off and LNG vaporization gas supply system from the tanks to the consumers
.21 Testing procedures during sea/gas trials (submitted for survey verification only).
4 Materials of Construction
4.1.1 Materials entering into the construction of gas turbine engine propulsion systems are to comply with the 2.3 of the Part IV of the Rules for Steel Ships and the requirements of the 7.4 of the Guidelines.
4.2 Materials subjected to low temperatures are to comply with the requirements of Chapters 4 and 5 of Part XI of the Rules for Steel Ships.
5 Dual Fuel Propulsion Gas Turbines
5.1 General
.1 Gas turbines as components are to comply with the requirements of 10.2.4 and 10.5 of the Guidelines and Chapter 2 of Part IV of the Rules for Steel Ships.
.2 The dual fuel gas turbine is to be fitted within an acoustic gas-tight enclosure providing effective gas detection, fire protection, ventilation and cooling, as per the requirements given in this Annex. Alternatively, the gas turbines may be located in a space containing other machinery, provided that the installation arrangements of the gas turbine are in compliance with 9.6 of the Guidelines.
.3 The design of the gas fuel manifold and nozzles is to provide complete venting upon shutdown to prevent gas leakage and fire, unless the manufacturer demonstrates to the satisfaction of CR by experience with similar installations or test data that the gas manifold evacuation is not necessa ry.
.4 The design of the gas turbine is also to provide positive means of evacuating all unburned gas from the combustor, turbine and exhaust collector.
.5 Gas turbine fuel oil piping system is to comply with the requirements of Chapter 4 of Part VI of the Rules for Steel Ships except that gas fuel piping within the enclosure need not be jacketed or shielded.
5.2 Gas Fuel Manifold
.1 The gas fuel manifold fitted on the engine is to be designed for the maximum design pressure, temperatures, thermal growth, dominant resonances and vibrations that may be experienced after installation.
.2 The installation arrangements of the gas fuel manifold, piping and pipe fittings, joints, etc., are to provide the necessary flexibility to accommodate the oscillating movements of the engine without risk of fatigue failure in the piping connections to the engine.
.3 The gas fuel manifold and piping configuration is to be approved and certified by CR as per the engine manufacturer’s design.
.4 All metallic gas fuel manifold/lines are to be of corrosion resistant steel.
.5 All mechanical joints are to be of welded type, as far as practicable, and designed to prevent accidental leakage onto hot engine parts and any other source of ignition. Shielding or other means are to be provided to prevent this.
.6 Non-welded connections will be subject to special consideration.
5.3 Gas Fuel Control Valves
.1 Actuation is to be from the machinery control room, both at local and remote locations. Where the source of power to the actuator is electrical, the electrical source should be from the emergency power supply or provided with a backup power supply. All shut-off valves are to close rapidly and completely. All shut-off valves are to be of fail-safe type.
.2 All internal elements of the gas fuel system are to be resistant to corrosion.
6 Gas Turbine Enclosure
6.1 General
.1 The gas turbine is to be resiliently or rigidly mounted to a structural foundation within an acoustically and thermally insulated enclosure.
.2 The enclosure design is to maintain all components within their safe working temperature under expected operating conditions to minimize the risk of fire from sources of ignition such as hot spots. This is to prevent damage by heat to the adjacent components by providing effective fire prevention, ventilation and cooling.
6.2 Construction
.1 Unless the fuel gas piping up to the gas turbine inlet is of double wall design and in full compliance with 9.6 of the Guidelines, the enclosure is to be gas-tight.
.2 The enclosure is to be of steel construction and designed for removal of major components, such as the generator, reduction gear (where fitted) or gas turbine. The manufacturer is to identify maintenance access envelopes for removal of the above major components.
.3 The enclosure is to maintain structural integrity with the access panels removed.
.4 The enclosure is to be arranged such that if the removal of the access panels and doors while the turbine may be operating causes an unsafe condition, then the access panels and doors are to be provided with interlocks or other means to automatically secure the turbine prior to removal of the access panel.
CR Classification Society
.5 The enclosure, including enclosure cooling ducting, is to be designed as airtight, as required by Annex 5/6.2.1, and capable of withstanding the pulsation pressure that emanates from the gas turbine during operation.
.6 The enclosure is to be sized to allow for maximum deflection of the mounted equipment without the equipment striking the enclosure.
.7 Where one enclosure serves two gas turbines, an internal wall is to be provided.
.8 Where a gas turbine is located inside a gas-tight acoustic enclosure, the internal space of the enclosure is considered to be a Category A machinery space, hence, the separation of this space from the adjoining spaces and fire protection of this space is to be in accordance with the applicable requirements in the Rules for Steel Ships and SOLAS 1974, as amended.
.9 Each enclosure is to form a gas-tight seal at all piping, ducting and electrical connections that penetrate the enclosure walls.
.10 A suitable means of inspection such as a glass inspection window or a CCTV system is to be installed in the enclosure such that it is possible for operators to observe the engine and its major components, including gearbox accessories, intake, piping and instrumentation, during operation looking for evidence of fluid leakage, fire, smoke or other abnormal operating conditions without entering the enclosure.
.11 The inspection windows may be installed in the enclosure access doors where the door location meets the internal viewing requirements. Where the enclosure is considered a category A machinery space, the windows are to be of the same fire rating as the bulkhead in which they are installed.
.12 Interior lighting is to be provided in the enclosure to allow a clear view of all components from the inspection windows. Enclosure access doors are to be provided in locations that will allow maintenance personnel easy access to both sides of all major components within the enclosure.
Access to the air intake of the engine is to be provided.
.13 The enclosure is to be sound and thermally insulated.
.14 Thermal and acoustic insulating material is to be provided with protection to minimize the possibility of absorption of oils, grease and moisture.
.15 Protective metal guards are to be provided to avoid wear or puncture of exposed insulated areas subject to mechanical abrasion.
.16 A temperature sensor is to be placed inside and adjacent to each gas turbine engine compartment entry to indicate compartment internal temperature.
.17 A placard stating necessary safety precautions to be taken by personnel is to be provided at the engine space access if entrance to the engine compartment is required after gas turbine engine shutdown.
.18 A hazard label is to be placed on or adjacent to each access to the enclosure and internal to the enclosure, located so as to be visible upon entry, and is to provide appropriate personnel warnings.
.19 Each base and enclosure is to be provided with floor drains to prevent the accumulation of fluids.
The floor drains are to be situated to negate any effect of base and enclosure installation rake on drainage.
Fluid drains are to be arranged so as to prevent migration of fluids to the gas turbine exhaust area and hot section.
.20 Means are to be provided for drainage of the enclosure space in a safe manner. Where an enclosure is fitted with a water-based fire protection system, a fixed permanently installed bilge system for the enclosure is to be provided.
6.3 Enclosure Air Intakes and Exhaust System
6.3.1 General
.1 The design and arrangement of the system is to minimize pressure drop and back pressure, turbulence, noise and ingestion of water or spray.
.2 The systems are to be designed and supported to prevent stress loading of the flexible connections and expansion joints.
.3 The design is to also minimize the transfer of vibration to the supporting structure and withstand stresses induced by weight, thermal expansion, engine vibration, working of the ship and pressure thrust caused by the exhaust gas and intake air.
.4 The perforated plate interior surface of the exhaust ducts is to be held in place using retainer clips welded to the duct structure.
.5 All systems are to be designed to withstand dynamic forces encountered by motion of the ship at sea, as specified in Table IV 1-1 of Part VI of the Rules for Steel Ships.
.6 All sections of systems exposed to the weather are to be self-supporting without any wire, rope, etc.
.7 Air intake and exhaust ducting is to be of welded construction as far as practicable and is to be in accordance with the requirements of the Rules for Steel Ships for 5.7 and 5.8 of the Part XII.
.8 Cover plates for maintenance and access openings are to be bolted on and are to have handles or other means to facilitate their removal. All cover plates are to open outwards.
.9 Flexible metal hoses or expansion joints of an approved type are to be used at the engine air intakes, as well as at the exhaust outlets and elsewhere, as required for flexibility. The flexible joints are to be provided with internal flow liners. The method of connecting these flexible metal hoses or expansion joints to the gas turbines is to be in accordance with builders’ and manufacturers’
recommendations.
.10 Adjustments for misalignment through the use of expansion joints are not permitted.
.11 Provisions are to be made to allow for differences in expansion between the stack and the uptakes.
.12 Uptakes are to be fitted with expansion joints to allow for thermal expansion and to prevent overstressing of the uptake plating and ship structure.
.13 The systems, including air filters, moisture separators, intake silencers, exhaust mufflers, water traps and valves, are not to impose a pressure drop or back pressure which will exceed the acceptable values as specified in the engine specifications.
.14 The internal surface of ducting is to be as smooth as practicable. Strengthening members are to be on the external surface of the duct.
.15 Where ducts are large enough to permit entry of personnel for inspection and maintenance access, they are to be provided with removable cover plates and grab rods or access hatch.
.16 Gas passages are to be free of internal obstruction, except that grab rods and ladder rungs are to be installed for inspection and maintenance.
.17 Ducts too small to permit entry of personnel are to be provided with openings and removable cover plates at the ends of horizontally installed sections for cleanout.
.18 The systems are to be provided with drains at the low points. Collected drainage is to be led overboard, if environmentally safe and possible, or connected to a drain system.
CR Classification Society
.19 The intakes, cooling air and exhaust duct openings are to be located above the waterline and positioned to minimize the probability of raw water entering the air inlet, cooling air and exhaust systems. These are also to be located to minimize the probability of sea spray being entrained in the air flow and carried into air inlets and cooling ducts.
.20 Air intake, cooling air and exhaust ducts are to be positioned and designed to minimize the probability that exhaust gases from any engine or any other source are drawn into the air inlet or cooling air duct of gas turbine.
.21 The exhaust gases outlet from the gas turbine are to be clear of any ventilation system inlets.
6.3.2 Combustion Air Intake System .1 General
.1 The air intake system is to consist of all devices from the weather to the front face of the gas turbine, and is to be in accordance with the requirements of this Annex. Air intakes are not to be located in hazardous areas.
.2 The engine manufacturer is to provide the following performance requirements for compressor inlet airflow:
- Inlet pressure loss (max.), in mm of H2O
- Air compressor inlet flow distortion (max.), in percent. Alternatively, manufacturer is to approve the design of the aerodynamics of intake.
- Air compressor pre-swirl angle (max.), in degrees - Air compressor counter-swirl angle (max.), in degrees - Total pressure fluctuation (max.), in mm of H2O
- Turbulence (max.) in percent, where turbulence is defined as the root mean square of the fluctuating pressure level between 0.5 and 700 Hz as measured by a fast response pressure transducer divided by the steady state (average) total pressure
.3 Each unit of installed equipment requiring combustion air is to have a separately ducted air system from the weather directly to the gas turbine.
.4 Combustion air shall be ducted from the weather, through a separator system, directly to each propulsion gas turbine.
.5 The design is to be such that the pressure drop in the gas turbine combustion air intake does not exceed that specified by the engine manufacturer.
.6 Gas turbine intake systems are to be designed to withstand compressor surging, as specified by the gas turbine manufacturer.
.7 Ducting material for the gas turbine combustion air intake systems is to be corrosion resistant alloys or stainless steel.
.8 Fasteners inside duct assemblies exposed to the weather are to be corrosion resistant and to be of material that will prevent a galvanic reaction with the surrounding material.
.9 A moisture separator, as described below, is to be installed, unless another effective arrangement is approved. The moisture separator elements are to have separation efficiency, as required by the gas turbine engine manufacturers. The elements are to be readily accessible for inspection and easily removed manually for cleaning or replacement.
.10 Each gas turbine engine intake is to consist of louvers or vanes, moisture separator water wash manifold (if applicable to the moisture separator type).
The following items are also to be provided:
- Moisture separator panels, differential pressure safety system to activate alarms and open
- Moisture separator panels, differential pressure safety system to activate alarms and open