Thursday, January 13, 2011

ECONOMISER ON CHEMICAL TANKERS -- CAPT AJIT VADAKAYIL




EXHAUST GAS ECONOMISER FIRE

Tick Box
Ser No
                                 Description

INDICATIONS

1

A sudden rise in boiler pressure, if not noticed the safety valve may lift.

2
A steep rise in the temperature of the exhaust gas .

3
Paint on economizer casing may blister due to heat.

4
Heavy smoke and sparks from funnel.

5
High temperature alarm of exhaust Gas Economiser .


ACTION

1.     
Sound fire alarm and inform bridge.

2.     
Bridge to keep relative wind towards poop deck and warn traffic of impending engine stop.

3.     
Reduce Main Engine speed.

4.     
Change over Main Engine consumption from HO to D.O.

5.     
Stop Main Engine immediately as this shuts of 14% oxygen feed to the fire.

6.     
Stop ME auxiliary blowers .Cover turbocharger air inlet and shut ER doors.

7.     
Switch off all ER blowers and shut off blower and funnel flaps.  However ensure there is enough oxygen for running AE internal combustion engine.

8.     
Continue running boiler water circulating pump.

9.     
Check if there is loss of water—if then is loss then go to SPECIAL mode at bottom.

10.  
Start Fire Pump and do boundary cooling of Exhaust Gas Economiser casing using a spray nozzle.   Protect nearby electricals with plastic sheets.

11.  
Remove all combustible material from surrounding area and also from poop deck.

12.  
Put off all Engine Room Blowers and shut off  Blower and Funnel flaps.

13.  
Open M/E Turbo Charger drains and also EGE drains.

14.  
Keep air pressure on ME exhaust valve closing mechanism  ( closed valves )

15.  
Do not use soot blowers and start a hydrogen fire. However water washing (fixed ) nozzle may be used.

16.  
Line up bilge pump for transferring engine room bilges to holding tank.

17.  
Engineer in Engine Room should maintain watch-keeping to keep essential services and not get involved in fire fighting.

18.  
Be patient, once oxygen is starved fire will stop and circ water will conduct heat away.


SPECIAL MODE-- IRON FIRE / HYDROGEN FIRE

a)
Loss of boiler water means tubes are melted down, in which case an iron fire ( boiler itself burns ) or hydrogen fire may develop with great heat .  STOP circ water pump.

b)
Close valves on water circulating line.

c)
Discharge remaining water on EGE section

d)
Cool fire with LARGE quantity of water splash , direct on heart of fire.


Notes:

Gilled/ finned or pinned  economizer tubes act as a reservoir for unburnt hydrocarbon deposits. 

Highest temperature is at edge of gills.

Slow steaming for long time with low quality HO increases the deposits

Modern engine exhaust temperatures are 250 deg C—Ignition temperature of dry soot is 350C and wet oily soot is 150 C.

Never put off boiler water circ pump after berthing till the temperatures have come to <100 deg C.

Steam and water feeds an iron fire due to oxidation of iron. Temperatures are>1100 deg C

Steam feeds Hydrogen fire. Both H2 and CO are combustible. Temperatures are >1000 deg C

Alkaline MECYL contributes Calcium Sulphates and Calcium Carbonates which cause stickiness in gilled tubes . Boiler exh gas outlet temperature should be >165 deg C as condensation of H2SO4 in the exhaust gas makes the soot sticky.

Gas velocity in the boiler , circ water flow velocity and gas temperature on tube surface must NOT be too low.

Use preheated feed water of>140C during start up.

Above is not applicable to smoke tube EGE who have self cleaning effect provided gas velocity is > 20 metres / sec. Soot fires never cause any damage as tubes are surrounded by water.


                             BOILERS

An efficient boiler is one of the most sought after items on a parcel chemical tanker.

With insufficient / bad quality steam , the cargo work efficiency suffers. Frustrating  manhours are wasted by the deck team when tankcleaning water jet pressures and temperatures do NOT match to optimum for high MP cargoes.

If the boiler steam gives high chlorides it is not of much use on deck when wall wash tests have to be done for cargoes like MEG Fibre grade where UCC requires a pass limit of 0.249 ppm chlorides. Or if the stainless steel maindeck ,steam inlet lines are constantly being fed free iron from the ungalvanised mild steel engine room steam pipes.

There is a siphoning drum attached to the return main steam line on deck near the bridge front. This has a glass port for checking the top water level ----
Floating oils/ insoluble light density chemicals,
A drain to check high density insoluble chemicals which sink in water , or for soluble cargo sampling
A vent to check odour of water soluble clear cargoes / volatile gases.
This engine room entry check of return condensate is vital, the chief engineer is also encouraged to use this engine room entry check point, where he can use his sense of smell. By the time the water enters the hotwell it is a bit too late to use the sense of smell.

The return water must NOT be send to the engine room inspection chamber/ atmospheric condenser/ hotwell unless the deck siphoning drum contents have been passed by Chief officer. This responsibility cannot be delegated or abdicated by Chief officer. Failure to follow this vital Goodwood instruction may mean boiler explosion or off hire due to boiler tubes getting coated with cargo.

If viscous chemicals enter the boiler, the boiler will be destroyed due to overheating of the furnace caused by water carry over/ reduced water flow and reduced heat transfer. Particles floating on hotwell / cascade tank surface can be absorbed by absorbents like loofa sponges.

Steam flexible hoses should be immediately disconnected after steam blow into cargo pipelines and connected back at manifold or elsewhere ONLY when required.—or you will have cargo entering the boiler. This applies to air blow flexible hoses and nitrogen hoses too. The entire deck force must be absolutely clear about this.

The deck steam max pressure is 7 bars. Quite often the shore  steam blow is 10 bars (or higher). You could have cargo entering the boiler hotwell at a differential pressure of 3 bars if the ship/ shore hoses are open simultaneously , considering intermediate cargo valve seats are do not give  perfect  seal with high MP cargoes in low ambient temperatures.

With insufficient boiler drum blow down or surface scum blow the steam arriving on deck may have water carry over which severely affect cargo discharge operations say of high MP cargoes in freezing weather. 

Funnel sparks must be avoided . The funnel must be monitored after an economizer wash. It is Chief engineers responsibility to advise the Master/ Chief Officer when economizer has been washed in port, so that sparks from the funnel in day time can be taken care of by relative wind.  Excess MECYL feed on new ships and during long manoeverings can cause soot build up in economisers.

If  sparks are emitted from the funnel the tanker should, if necessary, alter course as soon as possible to avoid sparks falling on the tank deck. Sparks cannot be seen in daytime and during dep port pilotage course cannot be altered for favourable relative wind without the pilot reporting this matter. In standard ports there are official forums to report such incidents.

Remember safety first .Any cargo, ballasting or tank cleaning operations that are taking place must be immediately stopped and all tank openings closed

There are toxic cargoes like PHENOL where the return steam coil water must not be sent back to engine room hotwell . In such cases the TCFW is heated by the butterworth heater inside the pumproom and injected into the tank steam coils and returned back to the same TCFW tank as a continious closed loop. Portable adaptor manifolds will be available for fixed steam inlet/ return manifolds.  


ECONOMISER WASHING:

When the periodical washing of the main engine exhaust gas economiser is carried out, usually in port limits, the washings/soot ( IMPREGNATED WITH MECYL ) are to be retained on board and must only be discharge to the sea when:-
¨ During daylight hours
¨ With the approval of the Master

Under the direct supervision of an engineer officer
¨ Ship is En-route and proceeding on passage.
¨ Ship is at least twenty miles from nearest land.

Prior to commencing the operation:
¨ Bridge watchkeeper must be advised and the position of the ship relative to the nearest land must be ascertained.
¨ Engineer Officer to record ship’s position and time of starting and completion in the Engine Room Log Book.
¨ Officer on the bridge to record the ship's position and the time of starting in the Deck Log book. On completion of the operation:
¨ Inform Officer on the bridge and obtain the ships position.
¨ Engineer Officer to record the ship’s position and time of completion in the Engine Room Record Book.
¨ Officer on the bridge to record the ship’s position and time of completion in the Deck Log Book

Ensure that there is no cargo/ oil contamination on the water side. Economisers must be kept clear of soot which lower efficiency during carriage of heating cargoes. Avoid using shore fresh water in boiler, always try and use fresh water generated on board. Shore water will usually contain excess chlorides , humous particles and silica.

Washing must be done by copious flow of hot water and not by atomizing high pressure cold wash from a kew machine, of couse you must check your holding tank capacity.

Open drains of turbocharger, exhaust manifold and exhaust boiler.
Make sure there is enough space in holding tank.
During wash frequently check turbo charger and exhaust manifold drains to ensure no water.
Carry out soot blowing after sailing. This soot blow must be monitored by chief engineer, to find out how efficient his staffs economizer washing efforts have been.
After an economizer wash the soot keeps dropping. There must be a final collection of soot before boxing back casing covers. Or this soot will comes out as sparks on dep berth.

Routine boiler maintenance must be done.

As a precaution against funnel fires and sparks; the burners, tubes, uptakes, exhaust manifolds and spark arresters should be maintained in good working condition.

Funnel uptakes, boiler tubes should be blown prior to arrival at and after departure from port. Boiler tubes should not be blown when the vessel is in port.

Boiler additives are chemicals which can affect the wall wash or deslopping contents for sensitive cargoes like Mono Ethylene Glycol fibre grade. Too muck alkali and you will be surprised to see that the chemical has turned a dark shade of red. Chief engineer must be made aware.

The condensate from steam main steam inlet line must be tested to determine the chloride and free iron content. Remember free iron plastered on SS bulkheads can cause pitting or even polymerization.

To prevent free iron on tank bulkheads and discolouration , before steaming tanks,  boiler must be blown down. Waste some steam on deck, and don’t be stingy about this. IMPORTANT— when you waste steam on deck or do live steaming the duty engineer must be told that water will have to be replenished in boiler, as the closed cycle is now open.

Always ensure that boiler feed water is fresh water generator output, when wall wash is looming ahead. Excess chlorides in feed water will cause lime deposits if not treated.

Engineering aspects—
Untreated boiler water has inherent salts and gases, which must be removed by chemicals or water softening chemicals. Salts cause scaling which reduce heat transfer. CO2 combines with water to form carbonic acid which attacks the boiler and condensation systems.

Oxygen in feed water causes severe corrosion and must be removed by thermal de-aeriation by keeping the feed water temp at around a practical value of 88 deg C. Around this temp CO2 is also removed.  Oxygen scavenging chemicals will remove the remaining quarter of Oxygen which  cannot be removed by heating feed water.

Alkaline treatment can neutralise  the effects of carbonic acid and also remove the salts which cause scale. Daily check feed and boiler water condition. Boiler water treatment programmes must strictly be followed.

Before sensitive cargoes like MEG FG where pure steam is required in cargo tanks—chemical dosing may have to be stopped as an exceptional case , but only after informing the master. Check for steam and water leaks daily.

It is Chief Engineers responsibility to ensure there is good quality/ quantity steam for cargo and tank cleaning operations and that the tank cleaning heater is absolutely efficient.

The boiler feed water system must be kept clean and free of contamination.  Salinometers must be used on all condensate systems that could contaminate the boiler. If a salinometer fails, that condensate system must be tested every 4 hours to minimise the risk of contamination.

A close watch must be kept on observation tanks for the possibility of chemical cargo/bunker heating coil contamination and immediate action taken to prevent oil ingress to the boiler should contamination occur.

Daily testing and treatment of condensate and boiler water, together with logging of test results, blow downs and chemical consumption are essential to detect any changes.

In order to improve oxygen scavenging, the hot well temperature of open feed systems is to be maintained as high as possible, ideally, and if possible, above 90 deg C.





CAPT AJIT VADAKAYIL

1 comment:

  1. CH
    October 13, 2014 at 6:35 AM
    Respected Captain,

    What is special about Tamil Nadu?

    How come it is able to continuously produce word geniuses like Ramanujam, Subrahmanyan Chandrasekhar, C.V. Raman, A.R. Rahman, Abdul Kalam, Venkatraman Ramakrishnan, Viswanathan Anand, Illayaraja, etc?

    Even till recently the Chief Justice of India, the Finance Minister, the RBI governor are all Tamils?

    Is there any scientific reason behind this? Because no other region has produced such super genius people in such numbers.

    Regards

    ReplyDelete
    Replies
    #####################
    Capt. Ajit Vadakayil
    October 13, 2014 at 7:06 AM
    hi ch,

    i am sure if i were a lawyer, i will NEVER EVER become CJI.

    i am sure if i were an economist, i will NEVER EVER become finance minister.

    you want me to continue ?

    when i was on my training ship in mumbai with 250 other cadets ( two years ) -- the biggest TELUs ( oily and slimy ) and SNEAKS ( snitches ) became SCC ( senior cadet captains ) , CC ( cadet captains ) , CL ( cadet leaders ) etc.

    i used to be in the CAPTAINS MONTHLY BREAKFAST PARTY ( cadet with maximum negative marks for OFFICER LIKE QUALITIES ) -- to be chewed up for breakfast every month .

    i got an EXTRA FIRST in every subject --except OFFICER LIKE QUALITIES.

    now what are OFFICER LIKE QUALITIES-

    being a son of a bit#h, being a sneak, being a hypocrite, being a as$ kisser , being a leader who will sell out his team, being a back biter, being an informer , being the best in playing to the gallery.

    so, so--

    at the passing out parade --most of the cadets who got all PRIXES were leaders -- they all got BOOOOOEEEEED !

    I remember i got only one prize--for being the best REPORTER IN ENGLISH -- the claps I got from the entire hall still resound in my ears -- along with another ROC ( royal officer cadet -who did NOT care to become a sold out leader ).

    and mind you -- i was in every single team which made my TOP ( starboard fore top ) the champion TOP.

    i was a champion sailor, rower, signaller, marks in subjects, soccer team in both years --

    but i lacked OLQ ( officer like qualities ) of being a FU#KIN' SLIME BALL.

    so in my passing our certificate , after two years of training -- i had an EXTRA FIRST in all subjects -- except OLQ where i was third grade

    so i guess they held a special meeting and GRACED ME TO FIRST CLASS --a young 18 year old boy -- .TEE HEEE !

    AT SEA, THE SAILORS DO NOT CARE FOR YOUR FOUR STRIPES- THEY ONLY CARE FOR WHO YOU ARE--

    AT SEA PEOPLE WHO KNOW ME , OR HAVE HEARD OF ME -- OR SAILED WITH ME, WILL VOUCH--

    CAPT AJIT VADAKAYIL WAS A SLAVE MORE POWERFUL THAN THE MIGHTY FU#KIN' CAESAR -- BY LIGHT YEARS .

    this has now passed on to LORE -- never ti happen again in the annals of sea .

    am i boasting ?

    -- so be it !

    humility is NOT about having a low opinion of yourselves to please the JEALOUS party.

    see, this would have been part of my post-- GAMES CAPTAIN PLAYED--

    you made me reveal it prematurely --with your TAMIL PRIDE ! TAKE IT EASY !

    check out my training ship-

    https://www.youtube.com/watch?v=MwpFBPMtnj4

    https://www.youtube.com/watch?v=k0BxC3kFET8

    capt ajit vadakayil
    ..

    ReplyDelete