ICGSMA Bulletin - Indian Coast Guard

ICGSMA BULLETIN (JAN - MAR 13)
likely cause of the low idle RPM.
DEFECT IDENTIFICATION
After a detailed discussion with Senior
Engineer Officer and Engineer Officer, it was
decided to remove and dismantle the governor for
speculating the defect.
A team comprising of the Senior Engineer
Officer and two ERAs worked towards DR of the DG
set. On dismantling the governor drive end parts, it
was observed that a small metallic chip with thread
strands had got stuck with the oil pump suction
strainer.
THE DEFECT On starting of DG set, the hydraulic
oil is pumped through the oil pump suction strainer
to the power piston of the governor. The power
piston movement is transferred to the PTR Fuel
pump via mechanical linkage for maximum fuel
rack during starting and for further RPM
adjustment. As the oil strainer was choked, the
pump ceased to develop sufficient pressure to
operate the power piston which resulted in
sluggish mechanical lever movement to fuel pump.
DEFECT RECTIFICATION
The suction strainer and pipe were cleaned
with air and re-fitted with governor. Subsequently,
trials were undertaken and found satisfactory at
1500 RPM on both idle and with load conditions.
OBSERVATIONS
The position of the governor strainer was
intricate to locate visually from oil filling cap.
Despite oil renewal the obstruction from oil
strainer was not cleared. This was the main reason
for the team in speculating the cause of defect.
LESSON LEARNT
The governor without oil filling strainer
may cause ingress of foreign matter into the sump
during routines. Care should be taken that the oil is
added carefully using a clean container with
portable cloth or commercial plastic strainer.
RECOMMENDATION
This defect may minor in nature, but equally
unique and rare. A lot of attention is needed to
locate and avoid complexity of such defects. It is
highly recommended that a renewable cup shaped
plastic strainer be incorporated on the governor of
the DG set to prevent any kind of blockage by
impurities.
A CASE STUDY - DEFECT ANALYSIS ON
RO PLANT FOR LOW PERMEATE OUTPUT
WITH HIGH SALINITY
ICGS Meera Behn
The ship is fitted with 05 TPD RO Plant,
Make: Rochem Separation. The plant was
overhauled and DT modules were service
exchanged in Mar 12 during SR-11 at Mumbai by
PAC firm M/s Rochem Separation, Mumbai. The
plant is being utilized to meet fresh water
requirement of the ship.
In the month of Feb 13 almost 01 year after
overhauling it was noticed that the permeate
output of the plant has been decreased to 125 LPH,
whereas designed output is 208 LPH. The plant DT
modules were chemically cleaned by RO cleaner
33, 22 and 11 but no improvement observed. The
salinity of permeate also observed comparatively
high as 1700 µ cm. The permeate output further
decrease to 70 LPH and Plant start tripping view VS
60 (servo control valve) closure indicated by
permanent illumination of lamp no 4 and 5 on RO
plant panel. Indication of this defect was
understood as malfunction/failure of servo control
valve.
An insight to trouble shooters 11