The range of chemicals shipped in bulk has increased enormously in modern days .The need to maintain product quality, to minimise the potential for discoloration, and to facilitate tank cleaning between cargoes it is essential to test tanks and cargo at times and when required.

Most common tests and checks for oil and chemical cargoes include testing tank walls for cleanliness.

Testing is normally carried out by independent surveyors who, according to local practice or a written agreement in the charter party, are accepted by shipper, receiver and owner.

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If possible one of the ship's deck officers should take part in the cargo sampling, cargo testing, tank cleanliness examination etc. He should make notes and observations on the work of the surveyor with a view of protecting his party's interests. It is therefore necessary to have a general knowledge of the various procedures, without necessarily being able to carry them out himself. Some tests which are easily carried out by the ship's staff by relatively simple means. A small laboratory with a stainless steel sink, a rack for 10 - 20 bottles of chemical reagents, test tubes (Nessler tubes) and a supply of distilled water are an advantage to have on board.



In some remote ports independent surveyors may not be available. This gives the chief officer added responsibility in following the shipper's or receiver's instructions, particularly if he is requested to sign their protocols etc.

There are number of tests, which are commonly used by surveyors. Most of the tests are of a physical nature and are relatively easy to carry out on board. Normally the test results do not give any exact answers as to contaminations etc but have to be judged in relation to commonly accepted standards in industry or agreed values between the parties. Furthermore, the answers are often only indices of contaminations. In case of any disagreement full laboratory examinations may have to be carried out. It is then of the outmost importance that the ship secures samples, sealed by an independent surveyor or by both parties, of the cargo parcel in question for further analysis.

ASTM (American Society for Testing and Materials) - standards are contained in a series of updated books, obtainable through good bookstores or from: American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103, USA.

Similarly API (American Petroleum Institute) issues various standards, which are generally applied. All measurements and tests have their tolerances, usually rather widespread and with correspondingly great economic consequencies. It is good practice to take all readings twice, repeat important tests twice etc!

With ships engaged in special trades it might be useful to be able to carry out the more common tests on board and to train personnel correspondingly. This refers in particular to the testing of tank walls for cleanliness. Many delays can be avoided if the ship's officers can satisfy themselves that the tanks are properly cleaned before entering port, using the same methods as the surveyor coming on board does.

Cargo Lines and Fittings

Inspection of the cargo pumping, piping and tank heating equipment is an essential part of the preloading survey for determining a vessel's suitability to load a sensitive chemical product. Although many chemical parcel tankers have dedicated cargo piping and individual submersible cargo pumps and heating coils for each tank, it is still possible for the residues of a previous cargo, tank washing solutions, water and/or heat exchange fluid to be retained in drained piping, cargo pump cofferdam spaces and leaking heating coils.

It is therefore essential that tank cleaning operations include thorough line cleaning, draining of cargo piping and heating coils, blowing of cargo pump cofferdam spaces, as well as pressure testing of heating coils and submersible cargo pump seals.



Related info:

1. Fixed and portable tank cleaning equipments
   The installation of fixed tank washing machines within a cargo tank allows an inert atmosphere to be maintained during the washing operation, and thus permits cleaning in a closed mode in compliance with port regulations prohibiting release of noxious vapours. Their installation and use also reduces crew exposure to cargo vapours and inert gas.
   


2. Tank cleaning and risk with cargo contact
   Different chemicals affect the human body in many different ways. A general information and some practical advice are available in Appendix,7, of "Medical first aid guide for use in accidents involving dangerous goods" published by IMO, WHO and ILO ref (36).


3. Practical example of solving tank cleaning problems
   Cleaning of tanks is usually the responsibilty of the ship. Tank cleaning and the cleanliness involved have different standards depending upon the previous cargo and the cargo to be loaded. But the matter can be still more complicated, as cleanliness for one and the same product may vary, depending on who the receiver is and for what purpose the cargo is finally intended.


4. Tank cleaning fatality- case study & lessons learned
   In the trade practice onboard chemical tankers, it is not uncommon that the use of methanol or other chemical/detergents is undertaken to achieve the required standard of cleanliness inside the cargo tank, pipelines, cargo hoses, manifold adaptors/reducers, gauging equipment, etc. Industry publications clearly highlight and caution regarding their use due to their flammability and toxicity hazards.


5. Pre-cleaning /washing of cargo tanks
   Washing between different grades of cargo is the most common reason for tank cleaning. In most cargo sequences on chemical tankers, this cleaning may consist of no more than a simple hot or cold seawater wash. A simple water wash will disperse many types of chemicals and has been found effective between clean petroleum products such as gas oil and kerosene.


6. Final cleaning of cargo tanks prior loading
   Method of final cleaning to be used depends on both previous cargo and cargo to be loaded. As a general rule the tanks and piping shall be completely drained of water or residues before loading. The bottom of the tanks may have to be dried up with rags.


7. Tank cleaning and posoning hazards
   Certain substances affect the tissues locally as an irritant (cashew nut shell oil) or cause grave damage to the eyes, skin or mucous membranes (e g strong acids and caustic). Other substances may be absorbed by contact to the skin without local effects (e g nitrobenzene, aniline).


8. Testing of tanks and cargoes
   Most common tests and checks for oil and chemical cargoes include testing tank walls for cleanliness. Testing is normally carried out by independent surveyors who, according to local practice or a written agreement in the charter party, are accepted by shipper, receiver and owner.


9. Practical tank cleaning methods for various noxious liquid cargo
   Tanks that may have contained monomer or drying oils should first be cleaned with sufficient cold water quantities to avoid polymerization of cargo residues. In some cases, it is necessary to employ tank cleaning chemicals, but their use is generally limited as it may be difficult to dispose of slops.


10. Special tank cleaning method
    If a special method involving cleaning agents is to be used, it may create an additional hazard for the crew. Shipboard procedures should ensure that personnel are familiar with, and protected from, the health hazards associated with such a method. The cleaning agents may be added to the wash water or used alone. The cleaning procedures adopted should not entail the need for personnel to enter the tank.


11. Determining proper tank cleaning by acid wash method
    The acid wash method is used if there is any suspicion that a cargo of aromatics may have been contaminated by a previous oil cargo. The method is also used as a check that a tank is sufficiently cleaned before loading aromatics.


12. Supervision of all tank cleaning and gas freeing operations
    Tank cleaning is essential on-a chemical tanker, but it must be recognised as a potentially hazardous operation, and rigorous precautions should be observed throughout the process. Together with gas freeing, it is probably the most hazardous operation routinely undertaken on a chemical tanker.


13. Disposal of tank washings, slops and dirty ballast - safe method
    During normal operations of a chemical carrier, the main need to dispose of chemical residues, slops or water contaminated with cargo will arise during or immediately after tank cleaning. Final disposal of slops or washwater should be in accordance with the ship's P&A Manual. Tank washings and slops may be retained on board in a slop tank, or discharged ashore or into barges.


14. Cargo tank damage during pigging operations
    Blowing and pigging of pipelines at terminals poses inherent risks for the terminal and a chemical tanker. Frequent damages to tanks have occurred. If there are doubts about the shore operation or signs of problems ashore the OOW must immediately request clarification.


15. Determining water contamination in chemical cargo
    Presence of free water in non water-soluble products can, very roughly be determined on board by warming a sample of the product in a test tube or in a bottle. Water will then collect at the bottom of the tube and can be seen after some time.


16. Determining Sulphur contamination (sulphides) in chemical cargo
    Certain products, in particular "virgin naphta feedstock'' (petroleum naphta) are severely contaminated by minor amounts of sulphides (and also lead compounds), which poison catalysts in further processing. Previous heavy oils or dirty harbour ballast water may have left traces of sulphides in the cargo tanks.


17. Chloride contamination in chemical cargo - how to resolve?
    Certain cargoes are very senstive to chloride contamination, in particular glycols, methanol, ethanol . The tanks should be finally washed with fresh water. However, chlorides (salt) may still be present and a check might be useful. The greatest risk for salt deposits is on horizontal surfaces.


18. APHA (Hazen) method for determining color of very light chemical products
    A method called APHA (Hazen) is often used for very light products, defined in ASTM D-1209, viz aromatics, ketones. This colour scale is defined with an origin in 100 cc distilled water (value 0) to succesively higher values (max 500) by adding APHA-solution (a platinum-cobolt salt solution).


19. Loading, discharging & care of Phenol - Safety guideline
    PHENOL is carried at sea in a generally pure state. As a result, it has a high freezing point of approximately 40~ 41deg C. PHENOL is also extremely dangerous when it comes into contact with the eyes or skin and can be fatal.


20. Hazards of Phenol - safe handling of Phenol on chemical tankers.
    Phenol must be carried at temperatures within charterers instructions, typically between +50 and + 60 degrees C. Heating instructions of the Shipper or Owners must be followed to avoid protests and delays in the port of discharge. Overheating can damage this cargo. A full cargo heating log must be maintained.


21. Handling benzene & methanol safety precautions
    Benzene is known as a strong carcinogen and known to cause leukaemia. When handling cargoes with more than Benzene concentration of 0.5%, the Master is to ensure that all personnel involved are aware of the long term hazards.


22. Personal protective equipments for carcinogens & cyanide-like cargoes onboard chemical tankers
    A carcinogen is a substance that may cause cancer by contact or by inhalation. It is therefore essential that the highest safety precautions are taken when handling these cargoes. Access to deck areas must be restricted to duty personnel only. All accommodation doors and ports must be closed and ventilation put on recirculation. Any member of crews involved in cargo operations must wear chemical protective suits and breathing apparatus


23. Handling ACRYLONITRILE safety precautions
    ACRYLONITRILE are high value and require sophisticated handling for safety, health and loss prevention reasons. They need careful consideration prior loading , tank coating compatibility, cross compatibility with other cargoes carried, environmental controls if required (inerting).


24. handling ISOCYANATES safety precautions
    Product safety data sheets may be available from various sources. For safety preparation, until the specific product safety data sheet can be obtained, Chemical Data Guide for Bulk Shipment by Water (U.S. DoT), should be used.


25. Loading, carrying & discharging of Sulphuric acid - regulatory requirements & special handling methods
    IBC code compatibility chart strictly prohibits water in adjacent compartment to Sulphuric acid as you are aware if both come in contact with each other will generate a violent reaction. It is therefore recommended that the during loading of sulphuric acid adjacent ballast tanks to be always stripped dry to the maximum efficiency of the deballasting equipment used.

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