CASE STUDY-I

1. CASE STUDY-I ECONOMIZER FIRE

2. 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

3. 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

4. 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

5. 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

6. Damage Economizer which is 3 pass water tube type suffered sever damage of lower most pass. 50% of the tubes were severely damaged

7. Damage 7 tubes of middle pass were found damaged Middle pass found sagged by 20 ~ 25 cm

8. Damage Stoppage of approximately 26 hours leading to off hire & delays Repair cost

9. 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

10. 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

11. 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

12. 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 Causes

13. 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

14. 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

15. 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

16. 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

17. Take care of your Boilers well!