Boiler Maintenance Course
CASE STUDY-I
ECONOMIZER FIRE
Fleet Management Training Institute
Boiler Maintenance Course
Incident
 On 24th June, during morning 4 to 8 watch on a UMS
vessel 5/E was sole engineer on duty
 Watch selector was kept on E/R
 2nd Engineer was off watch
 At 0600 hrs Low steam pressure alarm sounded in
E/Room
 5/Er assumed it is due to excessive consumption of
steam & throttled steam to FO DBs
 Economizer exhaust gas high temperature alarm sounded
after about 30 minutes
 2nd Engineer was informed
 It was noted by 2nd Engineer that boiler water
circulating pump was found not working & stand-by
pump was also not working
 2/E noticed economizer casing red hot
Fleet Management Training Institute
Boiler Maintenance Course
Subsequent Action
Bridge was informed
C/E was informed
Engine rpm was reduced to maneuvering speed.
Engine was stopped after C/E arrived.
Aux blowers were cut off
Office was informed
Fleet Management Training Institute
Boiler Maintenance Course
Actions after discussion with
office
 T/C casing was covered
 Engine casing & all air inlets were sealed
 Fire fighting means were rigged near economizer and
also for boundary cooling
 Circulating water inlet & outlet to economizer were
closed
 Economizer was allowed to cool down on its own
 Funnel boundary cooling was started
Fleet Management Training Institute
Boiler Maintenance Course
Reason of Fire
 Boiler water circulating pump in use stopped due to
bearing seizure
 Other pump though kept in stand-by mode did not cut in
 No alarm sounded for abnormal stop of running pump
 Economizer ran dry for long period
 Excessive heat of exhaust gases caused tubes to heat,
resulting in ignition
 Economizer fire started
Fleet Management Training Institute
Boiler Maintenance Course
Damage
 Economizer which is 3
pass water tube type
suffered sever damage of
lower most pass. 50% of
the tubes were severely
damaged
Fleet Management Training Institute
Boiler Maintenance Course
Damage
 7 tubes of middle pass were found damaged
 Middle pass found sagged by 20 ~ 25 cm
Fleet Management Training Institute
Boiler Maintenance Course
Damage
 Stoppage of approximately 26 hours leading to off hire &
delays
 Repair cost
Fleet Management Training Institute
Boiler Maintenance Course
What went wrong ?
 Engine room was manned without senior engineer’s
present. Responsibility of E/R was left on 5/E
 Watch keeper did not monitor the stopped pump
 Steam low pressure alarm was taken casually by 5/E
 He did not inform the senior watch keeper & did not
even check if alarm was reset
 Watch keeper did not investigate the cause of low steam
pressure alarm
 Second engineer was called on subsequent second steam
low pressure alarm, who noticed that circulating pump
was failed
 Stand-by operation of pump failed
 Abnormal stop alarm failed
 The Economizer high temperature alarm setting was
6000 C which is way above and leads to delay in
detection of fire
Fleet Management Training Institute
Boiler Maintenance Course
Root Cause
 Boiler water circulating pump bearing seized, even
though pump was overhauled 1 month before this
incident
 Later investigation revealed that steam leaking from
gland found it’s way into adjacent bearing. Water flinger
on the shaft was not put back after the overhaul. This led
to loss of lubrication and complete seizure of bearing.
 Poor monitoring of machinery
Fleet Management Training Institute
Boiler Maintenance Course
Scope of Repairs
 Complete lower pass was cut & removed
 7 tubes on second pass were fitted with bypass
 Lower header was joined to middle pass using new
boiler tubes employing TIG welding
Fleet Management Training Institute
Boiler Maintenance Course
Causes
 Excessive soot deposit
Poor combustion leading to deposit of particulates &
un-burnt hydrocarbons
Excessive burning of lubricating oil causing
particulates to become sticky
Prolonged low speed running of engine
Soot cleaning routines, soot blowing not followed
 Insufficient cooling of economizer tubes, leading to
overheating
Scaling on water side
Corrosion and rust
Soot on fire side
Absence of water in economizer
Fleet Management Training Institute
Boiler Maintenance Course
What Causes Ignition…
 Three factors which are all needed for a soot fire: soot
deposits, oxygen and ignition
 The exhaust gas smoke from a diesel engine, due to its
high air excess ratio, contains about 14% oxygen
 Ignition of soot may arise in the presence of sufficient
oxygen when the deposits of combustible materials have
a sufficiently high temperature (higher than the flash
point) at which they will liberate sufficient vapour, which
may be ignited by a spark or a flame
Fleet Management Training Institute
Boiler Maintenance Course
Main Constituent
 The main constituent of the soot deposit is particulates
but, in addition, some un-burnt residues of fuel and
lubricating oils may be deposited in the boiler because of
faulty combustion equipment and, in particular, in
connection with starting and low speed running of the
engine
 The potential ignition temperature of the soot layer is
normally in the region of 300-400 Deg C, but the
presence of un-burnt oil may lower the ignition
temperature to approx. 150 Deg C, and under extreme
conditions even down to 120 Deg C
 This means that ignition may also take place after stop of
the main engine as a result of glowing particles (sparks)
remaining on the boiler tubes
Fleet Management Training Institute
Boiler Maintenance Course
Other Factors
 Exhaust gas velocity inside economizer
In a Class NK survey of over 53 vessels it was found
that all exhaust gas boilers based on a design gas
velocity lower than 10 m/s had soot fire trouble,
whereas relatively few boilers based on a design gas
velocity higher than 20 m/s had such trouble
 Inlet Piping to Boiler
Another factor that can reduce the actual gas
velocity in a specific part of the boiler is the design
of the inlet piping to the boiler
 Higher Gas Velocities generally help self cleaning of soot
Fleet Management Training Institute
Boiler Maintenance Course
What Should We Do?
 Proper maintenance of injection and combustion
equipments
 Regular cleaning of Economizer tubes and daily soot
blowing practice
 Need to inculcate traditional watch keeping procedures
where equipments are felt by hand for temp & vibrations,
sound characteristics are noticed, proper rounds are
taken
 Regular rounds of machinery space and realistic logging
of parameters
 Regular testing of alarms and trips and standby
machinery operation is essential, especially on UMS
vessels
 Need for calibration of measuring equipments.
 Training and experience of personnel before assigning
higher responsibilities
Fleet Management Training Institute
Boiler Maintenance Course
Take care of your Boilers well!
Fleet Management Training Institute