Thursday, September 22, 2011

CHLORINATED SOLVENTS ON CHEMICAL TANKERS- CAPT AJIT VADAKAYIL





CHLORINATED SOLVENTS

 
Chlorinated solvents are generally insoluble in water, and cleaning effect is limited to removing HC and other contaminants insoluble in water. They are hazardous to health. Carrying this cargo has a good cleaning effect on tank lining.

Chlorinated/ Brominated solvents hydrolyse in presence of water to form Organic and Inorganic acids which spoil the paint coating.  Shippers must give the moisture content in PPM. Water content should not exceed 100 ppm or 0.01% especially for epoxy.  Nitrogen pad is a must to exclude moisture.

Prior loading them take samples at manifold drain and line drain in brown narrow mouth self sealing sample bottles and also one clear bottle to check for clarity.

Chlorinated solvents must not be heated.

They are heavier than water and sink to the bottom. So when taking samples when you load Chlor solvents look for water on the surface of the cargo in the bottle.

Examples of chlorinated solvents are Methylene Chloride , Carbon Tetra Chloride,  Perchloroethylene , Trichloroethylene , Ethylene Di Chloride, Chloroform etc.  Methylene Chloride is biodegradable under both aerobic and anaerobic conditions.

Neoprene and natural rubber gaskets swell. So use Teflon or Viton gaskets. Check paint resistance tables for compatibility and also restrictions for previous cargoes. Check cargo flexible hose resistance tables too.

Chlorinated solvents are not loaded after Styrene and other monomers, Acrylates, Latex, Fats, Fatty acids, Nitriles, Epoxy resins , DOP etc due to NVM.

As a tank cleaning chemical, spraying of chlorinated solvents is not allowed.

Chlorinated HC does not by themselves attack SS. It is the impurities or decomposition products like Hydrogen chloride and Chlorides in the residual water phases which do the honours. If the products are acidic and contain high concentration of Chlorides, corrosion may occur.

Due to NVM Chlor solvents are not loaded after Monomers, Acrylates, Latex, Resins, Fatty acids, DOP, Nitriles , Palm oils, Fish oils , Glycols etc.

RECIRC OF CHLORINATED SOLVENTS

First check if the chlorinated solvent is compatible with the coating and the last cargo.

The Butterworth hose must be chemical resistant as the recirc is in full strength.

When recirc tank with chlorinated solvents the tanks must be first to water-white standard and DRY ( except for Latex and Isocyanates like TDI/MDI ) or discoloration will take place with damage .


Chlorinated solvents have high evaporation factor . So keep PV valve shut while recirc. When recirc use a filter at the recirc flange or spider/ octopus.

After recirc remove the solvent and steam tank thoroughly.  Drain tank and vent dry. Then spray Methanol which dissolves any traces of Perchloroethylene . Hotwash tank for one hour . Tank is now ready.

Since chlorinated solvent and water form acid compounds which can adversely affect tank coating and since this mixture dilutes the cleaning capability of the Chlorinated solvent, water should never be added to any Chlorinated solvent.

Generally one drum of 200 litres of solvent is needed for 100 cum.

Get the specs of Chlorinated HC before loading— Chlorides, water and Hydrogen chloride content. Also check the SS resistance tables. Clean tanks immediately after dischg even if they are not to be loaded again soon.

Chlorinated solvents are slowly hydrolyzed to acids, normally this is not a problem except if tank cleaning is stopped in an early stage.

Water will make the chlorinated solvent recirculation less effective.

Effect is also less on hot bulkheads due to adjacent heat. Methylene chloride evaporates more than Trichloethylene and Perchloroethylene as its VP is very high and BP very less—hence you require a large quantity of Methylene Chloride say—10 tons for an average sized tank. TCE evaporates the least.

If you don’t have Methanol on board, Graco inject light solution of Teepol in cold water and then wash off with hot water.

TRICHLOROETHYLENE

After dischg Isocyanate tanks have to be washed with non reactive solvent like chlorinated solvents and NEVER water. The urethane layer which forms will be very difficult to remove.

Chris code/ TCL
USCG/ 36
Colourless watery liquid, chloroform type sweet odour
Liquid on contact with very high temp/ flame  can decompose to form phosgene which is highly toxic
Non flammable , irritates eyes and skin
Slowly decomposed by light in the presence of moisture to form HCL
Suspected carcinogen
Prolonged skin contact can cause dermatitis
Sinks in water
SG/ 1.46
BP/ 87C
VD/ 4.5
VP/ 0.077 bars—80 mm hg at 20C
AH/ 38c
TLV/ 50 ppm
MARPOL category—Y
Not flammable
Moisture sensitive and can become acidic when wet
Excellent degreaser for extraction of oils/ fats and waxes
Used in drycleaning, tanning industry , fumigant etc
Not water soluble and hence requires emulsifier/ detergent
Mixing with water weakens capability—tank must be dry
Must not be heated
Spraying is not permitted
Check resistance of tank cleaning hoses prior recirc
When recirc use filter at spider.
After recirc vent and spray methanol to remove traces of solvent –then hot wash
Soluble in alchohol ethers and petroleum distillates
A very good solvent. Easily strips paints. Dissolves some plastics
When inhaled, trichloroethylene as with any anesthetic gas, depresses the central nervous system. Its symptoms are similar to those of alcohol intoxication, beginning with headache, dizziness, and confusion and progressing with increasing exposure to unconsciousness.

Breathing large amounts of trichloroethylene may cause impaired heart function, unconsciousness, and death. Breathing it for long periods may cause nerve, kidney, and liver damage.

The International Agency for Research on Cancer (IARC) has determined that trichloroethylene is “probably carcinogenic to humans.” California EPA regulators consider it a known carcinogen
Trichloroethylene is noticeable by smell at approximately 82 ppm and above. However, people can become accustomed to the odour and may not smell it until higher concentrations are reached.

PERCHLOROETHYLENE:

After dischg Isocyanate tanks have to be washed with non reactive solvent like chlorinated solvents and NEVER water. The urethane layer which forms will be very difficult to remove.

Before recirc remove all traces of water from tank
After recirc steam tank for 4 hours---drain tank vent
Perchloroethylene is soluble in methanol
CAT/Y
VP/ 14.2 mm HG at 20c
VD/ 5.83
SG/ 1.625
BP/ 121C
AH/ 40C
TLV/ 50C

Insoluble in water and requires the use of a emulsifier / detergent and then a solvent to remove from tank. Then warm wash.

Perchloroethylene, like most organic solvents, affects your brain the same way drinking alcohol does. Drinking alcohol within a few hours of exposure increases these effects, because the effects of perchloroethyelene and alcohol add together

If you are repeatedly overexposed for several days, you may be less affected as you develop a tolerance for overexposure. If a day or two then passes with no exposure, you may feel withdrawal symptoms such as nervousness, anxiety, and shakiness.

Perchloroethylene  is a potential cancer-causing substance (carcinogen).

Exposure to a carcinogen does not necessarily mean that you will get cancer. In general, the greater the exposure, the greater the risk of developing cancer. The best way to protect your health is to keep your exposure as low as possible.

Use it for its solvent properties. Most organic materials dissolve in perchloroethylene. It is the most widely used solvent in drycleaning and for degreasing,  including paint strippers and spot removers.

Instead or recirc with Diesel oil, in this strict prewash Marpol age , Perchloroethylene can be used.

METHYLENE CHLORIDE

After dischg Isocyanate tanks have to be washed with non reactive solvent like chlorinated solvents and NEVER water. The urethane layer which forms will be very difficult to remove. Instead or recirc with DO , Dichloromethane or Methylene chloride can be used. 

MARPOL /Y
Highly volatile
Attacks plastics
SG/ 1.322
BP/ 40C
VP/0.47 bars
VD/ 3
Use ambient water for cleaning
Liquid degreases the skin
Irritates the eyes and resp tract and can damage central nervous system
Sinks in water
AH/ 33C
VP / 500 mm HG at 20C
Colour/ clear
TLV/ 100
Negligible solubility in water-2% at 20C

First cold wash and then hot wash
Since ST is low –no emulsifiers or detergents are reqd.
Another name for it is dichloromethane
Methylene chloride is used as an industrial solvent and as a paint stripper
The World Health Organization (WHO) and EPA has determined that Methylene Chloride may cause cancer in humans.
Methylene chloride reacts with strong oxidizers, caustic substances, potassium, sodium, and concentrated nitric acid.
All chlorinates solvents show up in a UV test.

CAPT AJIT VADAKAYIL
(29 YEARS IN COMMAND )
..

5 comments:

  1. The blog was absolutely fantastic! Lot of great information which can be helpful in some or the other way. Keep updating the blog, looking forward for more contents...Great job, keep it up.. Cleaning Solvent

    ReplyDelete
  2. vanakam sir

    Shipping Corporation of India Limited (SCI) has issued notification for 40

    Graduate Marine Engineer (GME) trainee .


    sir is SCI good for doing GME course compared to other private institutes .

    after my training what will be my job prospects in SCI as IT DOES NOT GUARANTEE ANY FURTHER EMPLOYMENT OR EXTENSION OF SHIP BOARD TRAINING

    please take this as an exception and guide me sir as my career hangs by a thread.

    regards
    perumal.

    ReplyDelete
    Replies
    1. ji p,

      sci has the wherewithal.

      go ahead.

      capt ajit vadakayil
      ..

      Delete