ICGSMA Bulletin - Indian Coast Guard

ICGSMA BULLETIN (JAN - MAR 13)
SUGGESTION
The ship has projected this difficulty to the
PAC firm M/s Powerica and also suggested for
feasibility of fitment of Harbour DA sea water
pump on main DA as the gear profile for both the
DA sea water pumps is identical. The reps of PAC
firm has confirmed the fitment of Harbour DA sea
water pump on main DA’s with minor modification
on routing of the suction & discharge lines of the
pump. Recommendation of this modification is
requested to be assessed with expertise and may
be implemented in all the ship of this class.
BELLOW TYPE THERMOSTAT
It has thin brass bellows fitted to the frame
at the bottom and to a valve at the top. It is filled
with Ether, Alcohol or Acetone. This liquid
vaporizes at their respective boiling point.
THERMOSTAT
INTRODUCTION
JK Selvan, U/Nvk (ME)
ICGS Rajkamal
The functions of the thermostat are as
follows:-
(a) Thermostat is a device which prevents the
engine from getting overcooled when running
under normal condition.
(b) When the engine is started from cold, it
remains closed so that pump circulates
coolant(water) through cylinder jacket only.
(c) When engine reaches optimum operating
temperature the thermostat starts functioning.
(d) When the coolant water reaches above the
operating temperature thermostat opens allowing
hot water to flow through the cooler and get
cooled.
TYPES OF THERMOSTATS
The different types of thermostats are:-
(a) Bellow type thermostat
(b) Wax element type thermostat
At lower temperature the poppet valve
remains seated as bellows remain contracted.
Water is prevented from flowing through the
cooler. As the water gets hotter, the liquid
evaporates and the vapour exerts pressure inside
the bellows the valve gets open. A giggle pin
allows flow of air from bellows while charging it
with ether or alcohol.
WAX ELEMENT TYPE TERMHOSTAT
The wax is surrounded by a rubber sleeve. A
movable thrust pin has its conical end dipped in the
wax and its upper end screwed in the body. The
valve is fitted to the upper end of the container
which is surrounded by hot water. As the
temperature of the water rises, the wax melts and
forces the pin out of the wax container. The valve
alongwith the container moves down against
spring pressure. The spring pushes the container
back to its original position as the wax cools down.
An insight to trouble shooters 15