Dual fuel engines are those that employ gas fuel (with pilot
oil) and oil fuel. Oil fuels may include distillate and residual fuels.
Gas only engines are those that employ gas fuel only.
16.7.1.1 When gas is supplied in a mixture with
air through a common manifold, flame arrestors shall be installed
before each cylinder head.
16.7.1.2 Each engine shall have its own separate
exhaust.
16.7.1.3 The exhausts shall be configured to prevent
any accumulation of unburnt gaseous fuel.
16.7.1.4 Unless designed with the strength to
withstand the worst case overpressure due to ignited gas leaks, air
inlet manifolds, scavenge spaces, exhaust system and crank cases shall
be fitted with suitable pressure relief systems. Pressure relief systems
shall lead to a safe location, away from personnel.
16.7.1.5 Each engine shall be fitted with vent
systems independent of other engines for crankcases, sumps and cooling
systems.
16.7.2
Combustion equipment
16.7.2.1 Prior to admission of gas fuel, correct
operation of the pilot oil injection system on each unit shall be
verified.
16.7.2.2 For a spark ignition engine, if ignition
has not been detected by the engine monitoring system within an engine
specific time after opening of the gas supply valve, this shall be
automatically shut off and the starting sequence terminated. It shall
be ensured that any unburnt gas mixture is purged from the exhaust
system.
16.7.2.3 For dual-fuel engines fitted with a pilot
oil injection system, an automatic system shall be fitted to change
over from gas fuel operation to oil fuel operation with minimum fluctuation
of the engine power.
16.7.2.4 In the case of unstable operation on
engines with the arrangement in 16.7.2.3 when gas firing, the engine
shall automatically change to oil fuel mode.
16.7.3.1 During stopping of the engine, the gas
fuel shall be automatically shut off before the ignition source.
16.7.3.2 Arrangements shall be provided to ensure
that there is no unburnt gas fuel in the exhaust gas system prior
to ignition.
16.7.3.3 Crankcases, sumps, scavenge spaces and
cooling system vents shall be provided with gas detection (see 13.6.17).
16.7.3.4 Provision shall be made within the design
of the engine to permit continuous monitoring of possible sources
of ignition within the crank case. Instrumentation fitted inside the
crankcase shall be in accordance with the requirements of chapter
10.
16.7.3.5 A means shall be provided to monitor
and detect poor combustion or misfiring that may lead to unburnt gas
fuel in the exhaust system during operation. In the event that it
is detected, the gas fuel supply shall be shut down. Instrumentation
fitted inside the exhaust system shall be in accordance with the requirements
of chapter 10.