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Maritime English
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Maritime English
Unit 8
Testing an Engine
8.1 Introduction
The diesel engines, gear systems and hydraulics required to
power today's marine industry are
expected to operate for long periods of time at full load
capacity under extreme, often uncontrollable,
conditions. These units are constantly exposed to the damaging
effects of either fresh water or
saltwater, which are also used by some to cool the very systems
that keep them up and running. Wherecontamination and wear are
eminent, maximizing asset reliability becomes the priority.
Monitoring the
condition of both the unit and the fluid through oil analysis
identifies wear-causing contaminants and
their effect on performanceit costs so little to protect so
much.
Routine oil analysis is critical to managing asset reliability
in any marine application. High
performance expectations and harsh environmental operating
conditions present constant obstacles.
Continual exposure to water creates unique problems. Fresh
water-cooled engines are susceptible to
condensation and rust. Diesel engines typically operate at very
high temperatures, promoting oxidation
and acid formation. Gear systems and hydraulics are vulnerable
to contamination and wear. Oil
changes can be difficult and are not always convenient. Routine
testing and analysis can extend oil
drain intervals and identify small problems before they become
costly failures.
8.2 Engine Parameters
Before any engine is put on the market, it has to be thoroughly
tested. Nobody wants an engine that is
going to fail in use. So various tests are done on engines, of
which we will look at a few.
Useful Power
You will have seen that many engines have their power quoted as
brake horsepower(bhp). This has
been used by engineers for at least two hundred years. At its
crudest, it is a comparison with the power
you can get out of a horse, which had been the common form of
motive power for many centuries.
However a more scientific test was needed, and the diagram below
shows the kind of set up, called a
dynamometer.
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Maritime English
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Maritime English
Summary
We can work out indicated power from the indicator diagrams.
Internal combustion engines work on the four-stroke cycle: Suck,
squeeze, bang, blow.
Indicated power = energy from p-V diagram x no of cylinders x
number of cycles per sec.
Power from fuel = calorific value x flow rate
Thermal efficiency = indicated power power from fuel
Mechanical efficiency = output power indicated power
Overall efficiency = output power power from fuel
Power = torque x angular velocity.
1 bhp = 1 PS = 750 W
8.3 Comprehension Exercises
Ex. 1Fill in the gaps with the following words:
with; condition; newly; schedules; operating;preceded; other;
runs; generator; break-in
Load testing of ... overhauled engines must be ... by a
sufficient number of ... at no load and partial
load to insure that all parts are in good ... or functioning
properly and to insure that the engine and ... or
... loading device have reached uniform and correct ...
temperatures. Initial runs should comply ...
manufacturers engine ... procedures and ....
Ex. 2Match the words with the damages that they can do:
Rust can act as insulators, which form
barriers for proper heat transfer
Scale and deposit formations can lead to rust
Oxidation can accelerate wear, reduce heat
transfer efficiency and eventually
clog the system
Bibliography / Webography
1. Logie, C., Vivers, E., Nisbet, A.Marlins Study Pack 2(book
and two audio cassettes). Edinburgh,
Marlins, 1998 (ISBN 09531748 1 6)
2. Murphy, R.Essential Grammar In Use. 1st ed. Cambridge,
Cambridge University Press, 1990
(ISBN 0 521 35770 5)
