Monday, December 6, 2010

STYRENE MONOMER , CHEMICAL TANKERS-- CAPT AJIT VADAKAYIL

Styrene monomer polymerises at 65C . Inhibited product can start polymerising >51C with generation of great heat which can ignite the cargo and rupture the tank.



Colourless clear oily liquid

CHRIS/ STY

Sweet odour when pure, sharp disagreeable when impure

SG/ 0.904

Suspected carcinogen

Olefins

Marpol category/ Y

BP/145.2 ºC

MP/ - 30.6ºC

FP/ 32C

VP/ 6 mm Hg at 20C

VD/ 3.6

AH/ 30C

TLV/ 50 ppm

Combustible liquid

Flammable vapor

Flammable limits/ 1.1 to 6.1%

AIT/ 490ºC

USCG compatibility / 30

Nitrogen pad not done as inhibitor is oxygen dependant.

Uses/ polystyrene, protective coatings, copolymer resins etc.

Odour threshold/ 0.15 ppm

Surface tension / high—31.14 dynes/ cm at 19C

Viscosity at 20C/ 1 mPas

Solubility/ Negligible in water, soluble in alcohol and ether

Does not react with water.

Floats on water


Readily undergoes polymerisation when heated or exposed to light or an oxidising / peroxide catalyst. The polymerisation releases heat and may become explosive. Must be inhibited


Prior loading tank / lines must be free of oxidising agents. Cleanliness to water white . If at all some shippers do wall wash it will be for suspended particles like zinc dust , rust and lint. Chlorides 10 ppm and colour 10 Apha.


Ensure the manifold sample is clear and bright prior loading.


FOSFA/ Banned as any one of the last two cargoes in organically coated tanks (Epoxy ), and as the last cargo in stainless steel and inorganically coated tanks (Zinc )


Ignited by heat and open flame. Fire or contamination may cause violent rupture of tank


Avoid breathing vapours. Provide body and respiratory protection. Keep tanks cool with water spray.


Suspected carcinogen.  Vapour causes moderate irritation to the skin, liquid causes smarting of the skin and first degree burns on long exposure, inhalation or ingestion causes bodily harm. Styrene degreases the skin.


Irritates eyes and respiratory tract. Vapors cause weakness, dizziness, nausea and  sleepiness. Attacks the nervous system.STEL/ 10 000 ppm may be fatal in 30 to 60 minutes. Product can be absorbed through the skin, mucous,  membranes and eyes. Wear protective clothing


Cargo not to be exposed to excessive heat. Alarm system to monitor cargo temperature should be provided


Heating coils in tanks should be blanked.


Stowage adjacent to heated cargoes is not normally allowed. DOW allows maximum  adjacent cargo temperature 30°C.


Styrene monomer creates humidity on the bulkheads of adjacent tanks, therefore in case of simultaneous loading of Styrene Monomer and Methanol in adjacent tanks, keep the level of Methanol always 2 – 3 meters higher than level of Styrene Monomer to prevent water contamination of Methanol.  Hot moist vapour condenses on cold surface.


Styrene is inhibited by 10- 15 ppm PTCB or tertiary butyl acetechol. Styrene can be stabilised by toluene too.

Vessel should be provided with “Inhibition Certificate” from the manufacturer of cargo.


 The Certificate should specify:

The name and amount of additive present

        Whether the additive is oxygen-dependent

        Date additive was put in product and duration of effectiveness

        Any temperature limitations qualifying the additive’s effective lifetime

        The actions to be taken should the length of voyage exceed the effective lifetime of the additive.


Styrene Monomer can form polymer residues and in case of epoxy coating  the trace quantity of styrene  will soak into  the paint film and only very slowly desorb.Odour and quality critical cargoes must not be carried for at least two voyages after the carriage of Styrene in epoxy tanks.


Has low electrical conductivity. Can generate electrical charges during high turbulence.


To prevent polymerisation, present tank to surveyor as soon as practical .Never allow styrene to dry on the bulkheads.


Start washing with cold sea water one  machine circle and leave it until cleaning is started. Ensure lines are flushed .

Empty the tank and start butterworthing with COLD sea water for 1 hour

Then hot wash with 70C water for 1 hour.

Rinse with fresh water.

Steam for 2 hrs to eliminate odour

Drain lines, mop up, dry

Use smell killer only is the tank is absolutely clean.


If the next cargo is wall wash PTT will be a problem. Use inhibiter killer and recirculate. ( If your SS tank is NOT smooth, recirc with a emulsifier. )


-------CAPT AJIT VADAKAYIL ( 28 YEARS IN COMMAND )


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