AUTO IGNITION DANGERS ON CHEMICAL TANKERS- CAPT AJIT VADAKAYIL

AUTO IGNITION AND SPONTANEOUS COMBUSTION-  CAPT AJIT VADAKAYIL 

The autoignition temperature or kindling point of a chemical or substance is the lowest temperature at which it will spontaneously ignite in a normal atmosphere  WITHOUT  an external source of ignition, such as a flame or spark.

This means , you will be surprised to know that,  a fine spray of hydraulic oil or luboil or no 1 Fuel oil , will catch fire faster than a fine spray of Methanol or  Naptha or even Hydrogen.

This temperature is required to supply the activation energy needed for combustion. The temperature at which a chemical will ignite decreases as the pressure increases or oxygen concentration increases

Certain Lub oils have a AIT of 250 deg C.

Fuel or Chemical/   ( deg C)

Diethyl ether   160

Acetaldehyde  175

Fuel Oil No.1  210

Kerosene         210

n-Heptane       215

n-Octane         220

n-Hexane         225

Cyclohexane   245

Fuel Oil No.2   256

n-Pentane        260

Fuel Oil No.4   262

Gasoline          280

n-Pentene        298

Ehtyl Alcohol  365

Methyl Alcohol  385

Isopropyl Alcohol   399

Petroleum        400

n-Butane         405

Butane            420

Isopentane       420

Neoheaxane    425

Isooctane         447

Neopentane     450

Propylene        458

Isobutane        462

Xylene            463

Acetone           465

Isobutene        465

Propane           480

Ethylene          490

Styrene            490

Hydrogen        500

Ethane             515

p-Xylene         530

Toluene           530

Naphtha          550

Benzene          560

Coal-tar oil      580

Methane (Natural Gas)      580

Light gas         600

Carbon monoxide       609

Light hydrocarbons     650

The lowest temperature at which a substance will ignite in the presence of an external source of ignition is known as its flash point.

Hydrogen is less flammable than a fine spray of  Kerosene.

For liquids, it is defined as the lowest temperature at which a drop of solvent will ignite spontaneously.

Ethyl ether has an auto ignition temperature of 160°C , and its vapors have been ignited by hot pressurized steam pipes.

SPONTANEOUS COMBUSTION

Some materials when damp or soaked with oil, especially oil of vegetable origin, are liable to ignite without the external application of heat as the result of gradual heating within the material produced by oxidation. 

The risk of spontaneous combustion is smaller with petroleum oils than with vegetable oils ( like rapeseed ) , but it can still occur, particularly if the material is kept warm, for example by proximity to a hot pipe. Boiler suits must not be dried in engine room.

Cotton waste, rags, canvas, any similar absorbent material should therefore not be stowed near oil, paint, etc. and should not be left lying on the jetty, on decks, on equipment, on or around pipelines etc. If such materials become damp, they should be dried before being stowed away. If soaked with oil they should be cleaned or destroyed.

Certain chemicals used for boiler treatment are also oxidising agents and though carried in diluted form are capable of spontaneous combustion if permitted to evaporate. Oxidising chemicals must be stowed under supervision of Chief officer/ Chief engineer.

I remember stowing Chinese Calcium Hypochlorite containers on top most outboard end row--away from the accomodation,  incurring a small fortune in container shifting charges in 1993 -- 

-- and all were terribly upset with me.  My crew were surprised when I would tell them to spray some seawater using hoses on a very hot sea voyage afternoon , on these containers.

The German charterers complained to the Dutch Owners and the Owners to the Hong Kong Tech Managers-- in a sort of "we don’t want this Captain , if you cant shape him up".  They were of the opinion that this Indian Captain is stupid . 

But my shit did NOT smell those days, with my tech Mangers – they were all scared of me-- as they considered me as the Hitler type Belgian Jew MD’s ”blue eyed boy”.

This Belgian Jew was the type who would send goons to your house to break your bones-- if you fu#k around with him.  He is dead now-- otherwise I would have given a nice bio data about him.

I am a hard core Chemical man, and I did NOT care for these ignorant bosses ashore .  This is what is good at sea--you don't need to be a hypocrite.

I just told them to FU#K OFF !!   

On Capt Vadakayil's ship nobody can ever order him "HARD A PORT" ,  from ashore— PERIOD!.

It took another decade for proper legislation to take place, and that too after several Containerships were totally gutted with loss of life..  Between 1997 and 1999 there were 6 very large (multi-million pound loss) incidents on container ships involving calcium hypochlorite in various forms, including the “Contship France”, “Maersk Mombasa”, “Sea Express”, “DG Harmony”, “Aconcagua” and the “CMA Djakarta"

Calcium Hypochlorite is used extensively world wide for purifying water supplies and to a great extent in swimming pools. The chemical readily decomposes to release chlorine and oxygen, the components which make it useful as a disinfectant product. 

A side effect of this process is the reaction with combustible materials leading to spontaneous ignition and severe fires, promoted by the oxygen released from the chemical which renders ineffective the gas smothering systems typically used for fire fighting in ships holds. 

This characteristic as an oxidising agent had led to calcium hypochlorite being classified within Class 5.1 of the International Maritime Dangerous Goods (IMDG) Code. drums of calcium hypochlorite had a propensity to undergo a self-accelerating decomposition reaction that concluded with an explosion releasing large clouds of thick white “smoke”. 

This occurs when the heat produced by the decomposition reaction is unable to escape from inside the chemical package (because it is big, well insulated or in a hot environment). The temperature at which decomposition was initiated was found to be about 70 degC for drums of good quality material. An increase in the water content of the chemical could decrease the temperature at which the self accelerating decomposition could start, as could the presence of several different types of contaminants.  

Calcium hypochlorite was subsequently classified under 3 headings, UN1748, the high strength, dry material (with more than 39% available chlorine); UN2880, hydrated material with between 5.5% and 10% moisture, and UN2208, low strength material (typically known as bleaching powder) with between 10% and 39% free chlorine. 

Material with less than 10% available chlorine was not classified within the IMDG Code. UN1748 material was only to be carried on deck and “away from” sources of heat. UN2880 and UN2208 material could be carried under deck, UN2880 material also being stowed “away from” sources of heat “where temperatures in excess of 55oC for a period of 24 hours or more will be encountered”. 

The International Group of P&I Clubs initiated a serious study. The study found that self-accelerating decomposition in a 40ft container.  Self combustion could start at temperatures as low as 36 deg C. 

The IMDG Code currently has 3 entries for calcium hypochlorite:

UN 1748  Calcium Hypochlorite, Dry or Calcium Hypochlorite Mixture, Dry with more than 39% available chlorine (8.8% available oxygen)

UN 2208  Calcium Hypochlorite Mixture, Dry with more than 10% but not more than 39% available chlorine

UN 2880 Calcium Hypochlorite Hydrated or Calcium Hypochlorite Hydrated Mixture with not less than 5.5% but not more than 16% water.

The Code notes that these materials are liable to exothermic decomposition at elevated temperatures and shall be shaded from direct sunlight and all sources of heat and placed in adequately ventilated areas. It also warns that decomposition can be initiated by impurities. 

The changes came into effect in January 2001.-- better late than never

CAPT AJIT VADAKAYIL

( 29 YEARS IN COMMAND) 

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