procedures onboard your ship, refer to your ships
Cargo Fuel Operational Sequencing System (CFOSS)
Some operating troubles may be evident from a
low discharge pressure, excessive or unusual noise, or
an overloaded driving unit. The following paragraphs
discuss the most likely causes of operating troubles.
LOW DISCHARGE PRESSURE. A low dis-
charge pressure generally indicates that not enough
oil is being pumped. This condition may exist because
the pump needs priming or because of leakage. A
gradual decrease in discharge pressure over a period
of time is generally the result of pumping oil that
contains abrasive particles, which causes the housing
and rotors to wear.
The theories and laws of physics apply to all fuel
systems, but you must understand them completely
before you attempt to operate a fixed MOGAS sys-
U-TUBE PRINCIPLE OF
THE MOGAS SYSTEM
Hydraulics is the study of the behavior of fluids
in their application to engineering problems. The fun-
damental law underlying the whole science of hydrau-
NOISE. Excessive or unusual noises may be
lics was discovered by the French scientist Pascal, in
caused by cold oil, dirty strainers, air in the oil, vapor-
the seventeenth century. Pascals law states: Any
ization of the oil because of increased temperature, or
pressure or force applied to a confined liquid will be
misalignment of the coupling.
transmitted equally and undiminished in all direc-
tions, regardless of the size or shape of the container.
OVERLOADED DRIVING UNIT. Excessive
friction in the pump or in the driving unit can cause a
Liquid seeks its own level. The surface of the
driving unit to be overloaded. Misalignment of parts
water in a teakettle is at the same level in the spout as
when the pump is reassembled increases friction.
it is in the body of the kettle. This rule also applies
Overloading may also be caused by faulty operation
when a liquid is introduced to several differently
of the system, heavy or cold oil, or from other causes
shaped, openly connected tanks. The surface of the
that are not due to actual malfunctioning of the pump.
liquid would be at the same level in each connected
MOGAS SYSTEMS AFLOAT
LEARNING OBJECTIVES: Describe the typi-
cal afloat MOGAS system. Identify the protec-
tive systems for afloat MOGAS components.
Explain the correct operating procedures for
afloat MOGAS systems.
As an ABF assigned to LPD and LHA ships, you
will be working with motor gasoline (MOGAS) sys-
The two liquids handled in the MOGAS system
are seawater and gasoline. A cubic foot of seawater
weighs 64.0 pounds, while a cubic foot of gasoline
weighs 45.8 pounds. Since gasoline is lighter than
seawater, it will float on top of the seawater and not
mix with it.
A U-tube analogy to the MOGAS system, shown
in figure 6-4, is based on two principles:
The weight per unit volume of gasoline is less
than that of seawater. Therefore, the gasoline will float
on the surface of the seawater.
tems. As with JP-5 systems, each ship is different,
even ships within the same class. As older equipment
A given head of seawater in a U-tube will hold
is replaced with newer equipment, the uniformity
in balance a greater head of gasoline because the gaso-
among ships will increase until firm standardization
line is lighter than the seawater.
The MOGAS system on the ship is really a giant
Most equipment used in a fixed MOGAS system,
U-tube. The saddle storage tank containing seawater
such as pumps, valves, and filters are identical to the
and gasoline forms the bottom of the tube. The sea-
same equipment used in the afloat JP-5 system only
water piping forms one side of the tube, and the
smaller. This chapter will cover the major areas
gasoline piping forms the other side.
within a typical fixed MOGAS system aboard an LHA
The installation is designed to keep the gasoline
and the equipment unique to this system. Other class
storage tanks entirely full at all times, either with
ships systems are slightly different. For specific sys-
gasoline on top of the seawater or completely with
tem information and operation and maintenance
seawater. As gasoline is drawn off, water replaces it,