ICGSMA Bulletin - Indian Coast Guard

ICGSMA BULLETIN (JAN - MAR 13)
from the pipe line and visually inspected the
defective pipe along with ship’s staff. Further the
pipe lines were cleaned with wire brush and
chipped with chipping hammer. Excessive corrosion
was observed on both the pipes with hole up to 4
to 6 inches dimension.
5. The firm has rectified the defect by using
doublers at affected areas with 6 mm steel plate.
6. On analyzing, the extent of corrosion is
attributable to the following reason:
(a) Direct contact with sea water and air
simultaneously due to its design
(Overboard opening is just above the
water line).
(b) Overboard pipes are subject to high
temperature and seawater cooling while
the engine is running.
(c) Ageing of the pipes (ship has
completed 22 years).
RECOMMENDATION
Survey of the pipe to be undertaken in
every ERDD/refit and complete renewal of the
pipes may be undertaken in necessary under
supervision of a class surveyor.
A CASE STUDY-DEFECT RECTIFICATION
OF IDLE RPM ON DIESEL GENERATOR
INTRODUCTION
A Sathish Kumar, USE(ER)
C-133
As part of its power generation and
distribution (PGD) system, AOPV class of ships
which are fitted with four Diesel Generators of
make Cummins and model VTA-1710; each with an
output of 400 KW and max. RPM of 1500.
DEFECT DESCRIPTION.
The defect pertains to one of the diesel
generators onboard one of the AOPV. It was
observed that the idling RPM of DG set No. 2 was
not increasing beyond 700 from MSB remote
adjusting knob.
PRINCIPLE OF OPERATION.
Each DG is fitted with an electro servo
motor on top of the Governor’s RPM adjusting
shaft. As the DG is started, the servo motor is
controlled from MSB remote adjusting knob which
rotates the governor RPM adjusting shaft and thus,
engine RPM is stabilized.
URGENCY OF DR.
The ship was at sea on a long deployment
(OSD). One out of the four DGs was already non
operational due to defective alternator. Owing to
defect of idling RPM on DG set No. 2, the power
requirement of the ship was being fulfilled by the
remaining two DG sets. There was no standby DG
set. Consequently, DR of DG set No. 2 was critical.
ANALYSIS AND INVESTIGATION.
As preliminary checks, all fuel lines and
filters were checked for leakage. Governor’s
manual RPM adjusting knob operated from local
and checked for rotation of RPM adjusting shaft.
Governor oil drained and renewed. These
measures undertaken did not yield any positive
results towards rectification of the defect and the
defect persisted.
Further investigation revealed that the
governor’s mechanical lever movement from
hydraulic power piston for high throttle was
sluggish during starting of the DG set. This was the
An insight to trouble shooters 10