10 Power Generation Including Propulsion and Other Gas Consumers

10.1 Goal

10.1.1 The goal of this chapter is to provide safe and reliable delivery of mechanical, electrical or thermal energy.

LR 10.1-01 In the context of 10.1.1, electrical includes control, alarm and safety systems associated with power generation and propulsion, see also LR 2.1-02.

10.2 Functional requirements

This chapter is related to functional requirements in 3.2.1, 3.2.11, 3.2.13, 3.2.16 and 3.2.17. In particular the following apply:

• .1 the exhaust systems shall be configured to prevent any accumulation of un-burnt gaseous fuel;
• .2 unless designed with the strength to withstand the worst case over pressure due to ignited gas leaks, engine components or systems containing or likely to contain an ignitable gas and air mixture shall be fitted with suitable pressure relief systems. Dependent on the particular engine design this may include the air inlet manifolds and scavenge spaces;
• .3 the explosion venting shall be led away from where personnel may normally be present; and
• .4 all gas consumers shall have a separate exhaust system.

10.3 Regulations for internal combustion engines of piston type

10.3.1 General

10.3.1.1 The exhaust system shall be equipped with explosion relief ventilation sufficiently dimensioned to prevent excessive explosion pressures in the event of ignition failure of one cylinder followed by ignition of the unburned gas in the system.

LR 10.3-01 Arrangements are to be provided to enable purging of the exhaust system before the starting of an engine, after failure to start and following loss of ignition during operation of the engine. The purge is to be of sufficient duration to displace at least three times the volume of the exhaust system.

10.3.1.2 For engines where the space below the piston is in direct communication with the crankcase a detailed evaluation regarding the hazard potential of fuel gas accumulation in the crankcase shall be carried out and reflected in the safety concept of the engine.

LR 10.3-02 The safety concept and corresponding arrangements for prevention of crankcase explosions is to be documented and submitted for consideration and acceptance by LR.

LR 10.3-03 The safety concept is to demonstrate that all potential hazards associated with gas accumulation in the crankcase have been considered and shall include but is not limited to the following:

(a) Engine type, i.e. trunk piston or cross head, etc.

(b) The type of engine cycle employed, i.e. diesel, Otto, etc.

(c) Sources of ignition.

(d) Gas detection requirements including type of detection system, sampling rates, etc.

(e) The potential hazard when new and during service when sealing components become worn.

(f) Cause and effect matrix.

(g) Requirements for inerting the crankcase.

LR 10.3-04 Where trunk piston type engines are used, a means of injecting inert gas into the crankcase is to be provided.

LR 10.3-05 When gas is supplied in a mixture with air through a common manifold, flame arresters shall be installed before each cylinder head. The inlet system is to be designed to withstand explosion of a gas-air mixture by means of explosion relief venting or having sufficient strength to contain a worst-case explosion. This requirement may be omitted if the gas concentration within the manifolds is controlled and if combustion of an unburnt mixture within the manifolds can be eliminated.

10.3.1.3 Each engine other than two-stroke crosshead diesel engines shall be fitted with vent systems independent of other engines for crankcases and sumps.

LR 10.3-06 The outlet of the vent system of each engine is to be led to a safe location in the open air through a flame arrestor.

10.3.1.4 Where gas can leak directly into the auxiliary system medium (lubricating oil, cooling water), an appropriate means shall be fitted after the engine outlet to extract gas in order to prevent gas dispersion. The gas extracted from auxiliary systems media shall be vented to a safe location in the atmosphere.

10.3.1.5 For engines fitted with ignition systems, prior to admission of gas fuel, correct operation of the ignition system on each unit shall be verified.

10.3.1.6 A means shall be provided to monitor and detect poor combustion or misfiring. In the event that it is detected, gas operation may be allowed provided that the gas supply to the concerned cylinder is shut off and provided that the operation of the engine with one cylinder cut-off is acceptable with respects to torsional vibrations.

10.3.1.7 For engines starting on fuels covered by this Code, if combustion has not been detected by the engine monitoring system within an engine specific time after the opening of the fuel supply valve, the fuel supply valve shall be automatically shut off. Means to ensure that any unburnt fuel mixture is purged away from the exhaust system shall be provided.

10.3.2 Regulations for dual fuel engines

10.3.2.1 In case of shutoff of the gas fuel supply, the engines shall be capable of continuous operation by oil fuel only without interruption.

10.3.2.2 An automatic system shall be fitted to change over from gas fuel operation to oil fuel operation and vice versa with minimum fluctuation of the engine power. Acceptable reliability shall be demonstrated through testing. In the case of unstable operation on engines when gas firing, the engine shall automatically change to oil fuel mode. Manual activation of gas system shutdown shall always be possible.

10.3.2.3 In case of a normal stop or an emergency shutdown, the gas fuel supply shall be shut off not later than the ignition source. It shall not be possible to shut off the ignition source without first or simultaneously closing the gas supply to each cylinder or to the complete engine.

LR 10.3-07 Dual-fuel type engines shall be capable of immediate change-over to oil fuel only. All starting is to be carried out on oil fuel only.

10.3.3 Regulations for gas-only engines

In case of a normal stop or an emergency shutdown, the gas fuel supply shall be shut off not later than the ignition source. It shall not be possible to shut off the ignition source without first or simultaneously closing the gas supply to each cylinder or to the complete engine.

10.3.4 Regulations for multi-fuel engines

10.3.4.1 In case of shutoff of one fuel supply, the engines shall be capable of continuous operation by an alternative fuel with minimum fluctuation of the engine power.

10.3.4.2 An automatic system shall be fitted to change over from one fuel operation to an alternative fuel operation with minimum fluctuation of the engine power. Acceptable reliability shall be demonstrated through testing. In the case of unstable operation on an engine when using a particular fuel, the engine shall automatically change to an alternative fuel mode. Manual activation shall always be possible.

10.4 Regulations for main and auxiliary boilers

10.4.1 Each boiler shall have a dedicated forced draught system. A crossover between boiler force draught systems may be fitted for emergency use providing that any relevant safety functions are maintained.

10.4.2 Combustion chambers and uptakes of boilers shall be designed to prevent any accumulation of gaseous fuel.

10.4.3 Burners shall be designed to maintain stable combustion under all firing conditions.

10.4.4 On main/propulsion boilers an automatic system shall be provided to change from gas fuel operation to oil fuel operation without interruption of boiler firing.

10.4.5 Gas nozzles and the burner control system shall be configured such that gas fuel can only be ignited by an established oil fuel flame, unless the boiler and combustion equipment is designed and approved by the Administration to light on gas fuel.

LR 10.4-01 Details of the associated safeguards including processes and procedures are to be submitted where the boiler and combustion equipment is specifically designed for lighting directly on gas fuel.

10.4.6 There shall be arrangements to ensure that gas fuel flow to the burner is automatically cut off unless satisfactory ignition has been established and maintained.

10.4.7 On the fuel pipe of each gas burner a manually operated shutoff valve shall be fitted.

LR 10.4-02 Each burner supply pipe is to be fitted with a flame arrester unless this is incorporated in the burner.

10.4.8 Provisions shall be made for automatically purging the gas supply piping to the burners, by means of an inert gas, after the extinguishing of these burners.

10.4.9 The automatic fuel changeover system required by 10.4.4 shall be monitored with alarms to ensure continuous availability.

10.4.10 Arrangements shall be made that, in case of flame failure of all operating burners, the combustion chambers of the boilers are automatically purged before relighting.

10.4.11 Arrangements shall be made to enable the boilers purging sequence to be manually activated.

LR 10.4-03 In addition to the low water level fuel shut-off and alarm required by Pt 5, Ch 10.15.7 or 16.7 of the Rules for Ships for oil-fired boilers, equivalent arrangements are to be made for gas shut-off and alarms when the boilers are being gas fired. See Pt 6, Ch 1 of the Rules for Ships for requirements for control, alarm and safety systems, and additional requirements for unattended operation.

10.5 Regulations for gas turbines

10.5.1 Unless designed with the strength to withstand the worst case over pressure due to ignited gas leaks, pressure relief systems shall be suitably designed and fitted to the exhaust system, taking into consideration of explosions due to gas leaks. Pressure relief systems within the exhaust uptakes shall be led to a safe location, away from personnel.

LR 10.5-01 The exhaust system is to be designed to prevent the accumulation of uncombusted gas. Arrangements are to be provided to purge automatically the gas turbine before ignition commences on starting, or recommences after failure to start, or following a loss of ignition in operation. Arrangements are also to be provided to allow manual purging. Interlocking devices are to be fitted to ensure that purging can be carried out only when the fuel supply valves are closed. The purge is to be of sufficient duration and a means of preventing poor combustion which may lead to an accumulation of unburnt gas in the exhaust is to be provided.

10.5.2 The gas turbine may be fitted in a gas-tight enclosure arranged in accordance with the ESD principle outlined in 5.6 and 9.7, however a pressure above 1.0 MPa in the gas supply piping may be accepted within this enclosure.

10.5.3 Gas detection systems and shutdown functions shall be as outlined for ESD protected machinery spaces.

10.5.4 Ventilation for the enclosure shall be as outlined in chapter 13 for ESD protected machinery spaces, but shall in addition be arranged with full redundancy (2 x 100% capacity fans from different electrical circuits).

10.5.5 For other than single fuel gas turbines, an automatic system shall be fitted to change over easily and quickly from gas fuel operation to oil fuel operation and vice-versa with minimum fluctuation of the engine power.

10.5.6 Means shall be provided to monitor and detect poor combustion that may lead to unburnt fuel gas in the exhaust system during operation. In the event that it is detected, the fuel gas supply shall be shutdown.

10.5.7 Each turbine shall be fitted with an automatic shutdown device for high exhaust temperatures.