Cargo care during transit - chemical tanker procedure
Cargoes carried by a chemical tanker differ widely in characteristics and mode of handling, and thus in the care they require
during transit. During the voyage, attention must be paid to these special needs of cargoes.
Inert gas capacity should be sufficient for the entire voyage. If stored nitrogen is relied upon, it must be confirmed prior to sailing that the ship has sufficient nitrogen on board to be able to comply with the inerting requirements.
Regular checks on tank contents should be made to detect an unexpected change in liquid level. Cargoes that need cooling or heating must be monitored daily and a temperature log kept. Temperature log for the voyage to be maintained as per the instructions provided by the shippers. Some cargoes are liable to self-react under certain conditions . Cargoes that may self-react should be monitored daily in order to detect any abnormal behaviour at an early stage.
Inert gas capacity should be sufficient for the entire voyage. If stored nitrogen is relied upon, it must be confirmed prior to sailing that the ship has sufficient nitrogen on board to be able to comply with the inerting requirements.
Regular checks on tank contents should be made to detect an unexpected change in liquid level. Cargoes that need cooling or heating must be monitored daily and a temperature log kept. Temperature log for the voyage to be maintained as per the instructions provided by the shippers. Some cargoes are liable to self-react under certain conditions . Cargoes that may self-react should be monitored daily in order to detect any abnormal behaviour at an early stage.
Unexpected changes of temperature are an important early indicator of a possible self-reaction,
and attention should be given to ensuring that any required heating does not cause part of the cargo to become overheated.
Crystallisation. of inhibited liquid cargoes can lead to depletion of inhibitor in parts of the tank's contents (because the
inhibitor does not crystallise as well), and subsequent remelting of the crystals can thus yield pockets of uninhibited liquid,
with the risk of starting dangerous self-polymerisation.
With inhibited cargoes, the precautions and limitations described in the inhibitor certificate should be carefully observed. If control of the tank atmosphere is being used, ullage spaces should be monitored regularly to ensure that the correct atmosphere and overpressure are being maintained. Most inhibitors are not themselves volatile, so they do not vaporise with the cargo and are unlikely to be prese~t in cargo vapours. Therefore, polymerisation may occur where cargo vapours condense. Such places as inside vent valves and flame arresters should be regularly inspected, and any blockage by solid polymers promptly cleared.
Precaution/attention & record sheets are necessary for cargoes that need:
Avoiding claims
On many occasions cargo losses may occure during voyage and resulting in claims to the owners. Shipboard losses can be attributed to
1. Evaporation via PV vents.
2. Excessive ROB due to high pour-point of cargo or pumping problems.
While in some trades the discharge port out turn figures alone determine the amount of cargo delivered, in others they are still compared to the bill of lading figures provided by the load port.
Virtual losses (On paper only): In many shortage claims no actual loss has taken place but the amount of cargo has been overstated when loading and/or understated when discharging.
Stowing volatile cargo next to heated cargo causes evaporation losses. Charterers should specify maximum adjacent temperatures. Adjacent heat is an important spec on chemical tankers.
Chief Officer must find out that number of shore tanks to be loaded from, the quantity, temperature and SG of cargo in each. Whether there are any planned loading stops for shore tank changes. Whether density is being expressed ‘in air?or ‘in vacuum?Whether shore pipelines are full or empty, and details of any pipeline displacements planned. Whether loading by gravity or shore pumps.
Good Practices
The inspector must be accompanied at all times and his ullage measurements actively verified. Frequently maintaining and checking ship’s equipment - and arranging for yearly calibration of electronic measuring devices by an agent approved by the manufacturer.
Never permit the use of the terminal’s measuring equipment on board. If measurements taken with the inspector’s equipment differ from those taken with the ships, propose that all measurements be taken with each, and both be sent for verification ashore afterwards.
If the ship is pitching or rolling, five measurements should be taken, withdrawing the tape as soon as it penetrates the surface of the cargo. The highest and lowest should be ignored and the middle three averaged. Weather and sea conditions should be logged.
Cargo temperature may vary by 5 °C at different levels in the tank, so must be averaged from at least three readings -top, middle and bottom. Some digital probes can measure at more frequent intervals .Measurement error of 1°C can distort the volume calculation substantially , however this will depend on cargo density also.
Reference publications:
Related Info:
We have summarized below some of the special chemical cargoes frequently carried onboard chemical tankers
Main Info pages!
Home page ||| Chemical hazards ||| Cargo planning & Stowage ||| Cargo loading ||| Cargo documents ||| Safe stability ||| Cargo care ||| Preparation for unloading ||| Inert gas systems |||Gas freeing ||| Nitrogen handling ||| Chemical handling Safe practice |||Handling equipments ||| Cargo & Ballast pumps ||| Cargo tanks |||Tank cleaning |||Special cargoes |||Spills emergencies |||Fire protection
Chemicaltankerguide.com is merely an informational site about various aspects of chemical tankers and safety tips that may be particular value to those working in: Chemical Handling, Chemical Storage, Liquefied Chemical Suppliers, Chemical Shipping, Chemical Transportation, Chemical Terminals, Bulk Chemical Services and Chemical Processing. If you are interested in finding out more about chemical tanker guideline please visit IMO official website. For any comment please Contact us
Copyright © 2011 Chemical Tanker Guide.com All rights reserved.
With inhibited cargoes, the precautions and limitations described in the inhibitor certificate should be carefully observed. If control of the tank atmosphere is being used, ullage spaces should be monitored regularly to ensure that the correct atmosphere and overpressure are being maintained. Most inhibitors are not themselves volatile, so they do not vaporise with the cargo and are unlikely to be prese~t in cargo vapours. Therefore, polymerisation may occur where cargo vapours condense. Such places as inside vent valves and flame arresters should be regularly inspected, and any blockage by solid polymers promptly cleared.
Precaution/attention & record sheets are necessary for cargoes that need:
- Cargo heating : Cargoes that require heating must be monitored at least once daily and a temperature log must be kept. Ensure that correct heating medium is used, and that heating coils in tanks that do not require heating are blown dry and blanked. Prior to loading heated cargo, heating coils should be pressure tested and results recorded in the log book.
- Cargo cooling : In specialised cases, is required to prevent products from giving-off toxic and flammable vapours. Special care requirements are generally documented in the condition of carriage details contained in the ships Certificate of Fitness and also in the IBC/BCH Codes. The Company and Charterers are to be consulted if additional information is required.
- Tank Atmosphere ?monitoring and recording of the ullage space of pressure and/or oxygen should be carried out at regular intervals (daily) to ensure that the correct environment is being maintained.
- Temperature Control : Cargoes that may self-react must be monitored on a daily basis for any increase temperature that deviates from the ambient climatic conditions.
- Nitrogen cover : Prior sailing the vessel must have sufficient Nitrogen of the correct quality on board to comply with the padding requirements. No of bottle = Total Ullage Space (m3) x 0.2 / 180` x 50, for 4 changes maintaining 50mb, N2 bottle = 50l x 180bar
- Tank atmosphere : O2 content strictly controlled :Some cargoes like Hexane-HMD-Octene do have a maximum requirement with respect to oxygen in the vapour space. The vapour space has to be checked with the appropriate oxygen meter. The Shipper determines the frequency of the routine checks. The results are to be recorded in ‘Voyage Log?
- Agitation/ Circulation : Some chemicals, e.g. Phosphoric Acid, require agitation to prevent sediment separation and different temperature/density layers from forming. Re-circulating through a diffuser is one method of agitating the cargo
Avoiding claims
On many occasions cargo losses may occure during voyage and resulting in claims to the owners. Shipboard losses can be attributed to
1. Evaporation via PV vents.
2. Excessive ROB due to high pour-point of cargo or pumping problems.
While in some trades the discharge port out turn figures alone determine the amount of cargo delivered, in others they are still compared to the bill of lading figures provided by the load port.
Virtual losses (On paper only): In many shortage claims no actual loss has taken place but the amount of cargo has been overstated when loading and/or understated when discharging.
Stowing volatile cargo next to heated cargo causes evaporation losses. Charterers should specify maximum adjacent temperatures. Adjacent heat is an important spec on chemical tankers.
Chief Officer must find out that number of shore tanks to be loaded from, the quantity, temperature and SG of cargo in each. Whether there are any planned loading stops for shore tank changes. Whether density is being expressed ‘in air?or ‘in vacuum?Whether shore pipelines are full or empty, and details of any pipeline displacements planned. Whether loading by gravity or shore pumps.
Good Practices
The inspector must be accompanied at all times and his ullage measurements actively verified. Frequently maintaining and checking ship’s equipment - and arranging for yearly calibration of electronic measuring devices by an agent approved by the manufacturer.
Never permit the use of the terminal’s measuring equipment on board. If measurements taken with the inspector’s equipment differ from those taken with the ships, propose that all measurements be taken with each, and both be sent for verification ashore afterwards.
If the ship is pitching or rolling, five measurements should be taken, withdrawing the tape as soon as it penetrates the surface of the cargo. The highest and lowest should be ignored and the middle three averaged. Weather and sea conditions should be logged.
Cargo temperature may vary by 5 °C at different levels in the tank, so must be averaged from at least three readings -top, middle and bottom. Some digital probes can measure at more frequent intervals .Measurement error of 1°C can distort the volume calculation substantially , however this will depend on cargo density also.
Reference publications:
- International Safety Guide for Oil Tankers and Terminals (ISGOTT)
- Certificate of Fitness for the Carriage of Dangerous Chemicals in Bulk
- Ship’s “Procedure and Arrangements Manual?(Approved by Class)
- BCH/IBC Code
- ICS CTSG
Related Info:
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Edible oils Heating Instructions
Heating instructions should also be detailed, and these should state the in-transit temperature, loading/ discharging temperature and the allowed daily rate of increase of temperature. Rapid heating of certain grades can cause scorching of the cargo, and overheating the cargo can promote oxidation, hydrolysis, scorching and discoloration of the cargo. Rapid heating can also cause an increase in FFA content, which causes the load to turn sour, and is used as a measure of cargo quality, especially for palm oil. -
What is putrefaction process of liquid chemicals ?
Most animal and vegetable oils undergo decomposition over time, a natural process known as putrefaction (going off), that generates obnoxious and toxic vapours and depletes the oxygen in the tank. Tanks that have contained such products must be carefully ventilated and the atmosphere tested prior to tank entry . ..... -
Carriage of inhibited flammable chemical products in cargo tanks
In certain conditions of heat, pressure and in the presence of Oxygen, some chemical cargo types can become viscous and possibly solid and dense in nature. This self reaction can cause some cargoes , especially in the presence of high temperatures and Oxygen, to begin an exothermic reaction, becoming self heating and rapidly expanding which may result in possibly disastrous consequences for the vessel. -
Cargo sampling safety precautions
Cargo samples are evidence of the condition of the product during the various phases of transport (storage at terminal, arriving on board, loading, passage, discharging). This procedure describes sample-taking procedures and the legal background. Suitable PPE is to be worn when taking samples. Sample bottle to be flushed prior collecting sample. ..... -
Cargo segregation requirement for chemical tankers
In the case of two or more liquid chemical cargoes which react with one another in a hazardous manner, segregation must be done The product data sheets, together with the BCH/IBC Codes are to be studies carefully to determine the compatibility restrictions when carrying different groups of cargoes. -
How to avoid solidification in cargo tanks ?
Solidification in the cargo tanks can occur when solidifying cargoes are stowed adjacent to “cold cargoes” or cold ballast water in adjacent spaces. Tank bottoms must therefore always be checked for hard factions especially when carrying vegetable and animal oils, at regular intervals throughout the voyage and always prior to arrival in the discharge port. -
Cargo compatibility and reactivity of various chemical cargo
Transporting of dangerous and noxious liquid chemicals in bulk involved various risk factors. Between some chemicals violent reactions may occur if the chemicals are mixed in certain proportions. The result may possibly be an eruption and tank rupture. Such an occurrance must be prevented. Water may also have to be considered in this respect. -
Determining presence of contaminants
in chemical cargo
To maintain product quality onboard modern chemical tankers any contaminants in the cargo need to be observed. Following guideline may be useful determining various product contaminants in noxious liquid chemicals. -
Ship shore cargo connection safe method
The connection at the manifold of hoses or metal cargo arms for cargo handling is the primary cargo connection between ship and shore, and it is essential that both parties take proper care preparing for the connection. Flange faces, gaskets and seals used at this point should be clean and in good condition. Minimum standards for hoses are laid down in the IBC Code. The hoses should be in good condition and installed with gaskets which are suitable for the chemical product to be handled. -
Venting of cargo tanks safety procedure
Cargo tanks of a chemical tanker are required to be provided with venting systems to prevent both over and under pressurisation of the tank. Two types of venting system are specified by the Code, namely “open” and “controlled”. -
Ship to ship transfer operation
The ship to ship (STS) transfer of cargoes carried on chemical tankers is a frequent operation, and the following article addresses some special safety aspects of the preparations and procedures that may be found necessary for STS operations. -
Ship shore safety checklist while alongside a terminal
Due regard should be given to the need for adequate fendering arrangements. Ships should remain adequately secured in their moorings. Alongside piers or quays, ranging of the ship should be prevented by keeping all mooring lines taut: attention should be given to the movement of the ship caused by wind, currents, tides or passing ships and the operation in progress. Wire ropes and fibre ropes should not be used together in the same direction (i.e. breasts, springs, head or stern) because of the difference in their elastic properties. -
Cargo compatibility chart for handling dangerous liquid chemicals in bulk
Determine the group numbers of the two cargoes by referring to the alphabetical listing of cargoes and the corresponding groups. Many cargoes are listed under their parent names: unless otherwise indicated, isomers or mixtures of isomers of a particular cargo are assigned to the same group. - Cargo handling safe practice for chemical products
Check cargo hoses to see that they have not deteriorated, that flange connections are intact, that there is an electrical bond between hose flanges and that the working pressure for the hose is marked on it. If there is any doubt about the hose's condition, find out when the hose was last pressure tested . -
Risk with noxious liquid 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). -
How take a sample of noxious liquid cargo ?
Cargo samples are evidence of the condition of the product during the various phases of transport (storage at terminal, arriving on board, loading, passage, discharging).For protection against possible cargo claims it is very important that cargo sampling is correctly carried out.
We have summarized below some of the special chemical cargoes frequently carried onboard chemical tankers
-
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. .... -
Handling carcinogens requirements for certain chemical cargoes
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. ..... -
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). ..... -
handling ISOCYANATES safety precautions
Isocyanates 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, special tank cleaning procedures & environmental controls . ..... -
handling Sulfuric acid safety precautions
Loading , carrying at sea & discharging of Sulphuric acid involve high risk 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). ..... -
handling Phenol safety precautions
Phenol 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). ..... -
Hazards of Phenol - safe handling of Phenol on chemical tankers.
Heating instructions of the Shipper or Owners must be followed to avoid cargo related claims. Sufficient toxic gas measuring tubes must be available before commencement of loading. ..... -
Marine transportation of Phenol and more safety guideline
The solution of Phenol causes severe chemical burns to the intact skin, which are usually painless. It appears as white wrinkled "dead skin". In case of eye contact, permanent damage to the eye may occur..... -
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. ..... -
Carriage of Hydrolysable cargoes
Carriage of Hydrolysable cargoes ..... -
Carriage of Propylene Oxide cargoes
Carriage of Propylene Oxide cargoes ..... -
Requirements of various grade chemical cargo heating
In a modern chemical tanker in order to maintain product quality, to minimise the potential for discoloration, and to facilitate some liquid cargo transport in a safe manner cargo heating is required. ..... -
Handling toxic cargoes
There are three common ways that a cargo can be toxic: swallowed (oral toxicity), absorbed through the skin, eyes and mucous membranes (dermal toxicity) or inhalation as a vapour or mist (inhalation toxicity). .... -
OILS AND FATS (Animal and Vegetable) carriage guideline
Oilseeds such as rape, soya and sunflower as well as edible oils and fats in bulk, together with such commodities as copra, groundnuts and palm kernels ....
Main Info pages!
Home page ||| Chemical hazards ||| Cargo planning & Stowage ||| Cargo loading ||| Cargo documents ||| Safe stability ||| Cargo care ||| Preparation for unloading ||| Inert gas systems |||Gas freeing ||| Nitrogen handling ||| Chemical handling Safe practice |||Handling equipments ||| Cargo & Ballast pumps ||| Cargo tanks |||Tank cleaning |||Special cargoes |||Spills emergencies |||Fire protection
Chemicaltankerguide.com is merely an informational site about various aspects of chemical tankers and safety tips that may be particular value to those working in: Chemical Handling, Chemical Storage, Liquefied Chemical Suppliers, Chemical Shipping, Chemical Transportation, Chemical Terminals, Bulk Chemical Services and Chemical Processing. If you are interested in finding out more about chemical tanker guideline please visit IMO official website. For any comment please Contact us
Copyright © 2011 Chemical Tanker Guide.com All rights reserved.