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INFORMATION FROM DNV TO THE MARITIME INDUSTRY NO. 3 – JUNE 2003

Casua lty In formation

Course of eventsDuring morning attendan ce of engine room,

a water leak from the exhaust gas boiler was

discovered. In order to get to port, the water

circulation was shut off, and the instruction

manual on “emergency dry running” was fol-

lowed.

When a rriving at an chora ge, the exhaust

gas boiler overheated, and the crew found

that a soot fire had occurred.

Extent of damage

Tube stacks at gas out let of exh aust gas boil-

er were found heavily damaged. More than

half of the tube stack sectional area was melt-

ed down an d the tubes of the remaining

area were found sagging.

Probable causeEven though the tubes seemed clean from

soot and oil residues at visible inspection,

soot deposits will always be present to some

extent. Boilers with fi nn ed tube design are

even more exposed to accumulation of soot

than boilers with plain tube design, and the

consequences of a fi re are often more

severe.

In this case, it seems that th e circulating

pump was stopped almost immed iately, while

the main engine was left running. This

action left the tube stack fully uncooled and

the soot deposits on the tu bes eventually

ignited and a fi re occurred.

Seconda ry causes may be:

• Insufficient sootblowing and water washingin gen eral, especially soot blowing prior to

and after manoeuvring and after water

washing of t urbo chargers in service.

SHIP TYPE: Any SIZE (g rt ): Any YEAR OF BUILD: Any

Damage to exhaust gasboilers due to dry

running

Sagged economiser tube nests

after soot fire, finned tubes.

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• Sootblowing with wet steam, which leaves

the soot in the middle of the boiler.

• Sootblowing with too low pressure, which

leaves the soot in th e middle o f the boiler.

• Poor routines in observing the exhaust gas

pressure differential across the boiler.

Lessons to be learned

Actions to be taken prior to dry running:

• When shutting off the water circulation,

the main engine should also be shut down

so the exhaust gas boiler can cool down

and any smouldering soot deposits on the

boiler tubes can die out.

• The heating surface should be inspected

carefully for soot deposits, an d water wash-

ing performed, both for cleaning and

cooling.

• Make every effort to re-establish the water

circulation to th e boiler and thereby

reduce the dry running period to a mini-

mum.

• Boiler manufacturers allow dry running of

exhaust gas boilers onl y in the case of emer- 

gency and with a clean boiler. In addition

they emphasise that every possible precau-

tion m ust be observed to prevent soot fi re.

Actions to be taken duringdry running:

• Increase the frequency of sootblowing con-

siderably, an d perform soot blowing several

times prior to manoeuvring.

• Inspect the boiler frequently, and if any

soot is present, th en water wash th e boiler

and increase the sootblowing frequency.

• The boilers instruction manual must be

read ca refully and its instructions are

always to b e followed.

Cas ual ty In f o r mat ion

is published by

Mari t ime Industr ies,

Mari t ime Technolog y and

Pr oduc t ion Ce ntr e

(Dept. fo r Classi f icat ion & ISM)

Det Norske Veritas

NO-1322 Høvik, Norw a y

Tel: + 47 67 57 99 00

Fa x: + 47 67 57 99 11

The purpose of Ca sual ty Informa tion is

to pr ov ide th e ma r ine indus t r y w i th

‘ lessons to be learned’ f rom incidents of

s h ip da mag e a nd m or e s e rious accide nts .

In this way , DNV hopes to contr ibute to

the prevention of s imilar occurrences in

the f uture . The informa tion included

is not necessar i ly res tr icted to cover ships

classed w ith DNV an d is present ed,

w i thout ob l ig a t ion , f o r in f o r mat ion

purposes o nly.

Quer ies may be directed to

Mari t ime Industr ies , Mar i t ime Technolog y an d

Production Centre (Dept. f or Classi f icat ion & ISM),

NO-1322 Høvik, Norw a y.

Fax + 47 67 57 99 11. E-mail MTPNO860@dn v.com

Copyr ight a nd disclaimer : This publicat ion ma y be

r e pr oduce d f r e e ly on condi t ion tha t De t Nors ke

Veri tas (DNV) is alwa ys sta ted as th e source .

DNV accepts no responsibi li ty for an y errors or

misinterpretat ions .

View inside economiser

with melted tubes.