Cargo Planning on Chemical Tanker

Properties of cargo and hazards posed by them must be well understood by the Master and Chief Officer, prior finalizing the plan. In case of any doubts or unavailability of data, the charterers must be contacted and the required information sought.

Prior arrival port, the cargo plan shall be prepared in total and individually for each berth.  The cargo plan shall be discussed with all personnel concerned with the operations. It should be posted at a conspicuous location in the cargo control room (CCR) so as to be available to the key persons involved in the operations.

The cargo plan shall be discussed with shore personnel involved in the operations to ensure safe and efficient operations. The relevant ship staff must familiarize themselves with the plan and with all emergency procedures such as a spill, leak, fire, injuries etc.

The cargo plan may need amendments after discussions with shore personnel. Any alteration to the plan should be approved by the Master and conveyed to the ship’s personnel involved in the operation. The amended plan shall be displayed in the CCR.

Following points should be remembered when preparing a Cargo Plan

  • Voyage and cargo instructions will be issued by the Charterer and must be acknowledged.
  • The vessel shall carry only those grades of cargo, which are permitted by the ship’s Certificate of Fitness and the Tank Coating Compatibility list. In case a cargo not mentioned in the COF is to be loaded, the Company must be contacted immediately for advice.
  • Cargo history of cargo tanks especially when dealing with NIOP/FOSFA cargoes.
  • Load line applicable to the vessel and maximum cargo to load.
  • Density of seawater at load port to calculate the allowance for dock water and UKC
  • Restrictions imposed by various conventions and codes.
  • Port rotation and compliance to seasonal load line zones. The Master shall ensure that the vessel is not overloaded.
  • Restrictions imposed by National and Local requirements.
  • Pollution category, physical and chemical properties of the cargoes, health data, emergency procedures and the hazards of the cargo obtained from the various MSDS available. The Manufacturer’s MSDS sheet for the cargo must be obtained as soon as possible, but in any case prior to commencement of loading.
  • Cargo compatibility and segregation
  • Requirements of environmental control within the tank.
  • To avoid contamination through common venting systems
  • Draught, Trim and Stability of the vessel at all stages of loading, discharging and carriage.
  • Heating/ Cooling requirements
  • Heating status of the cargo. In case on cargoes not requiring heating, the coils shall be blown through, kept clear of water, valves closed and blanks fitted at both the inlet and outlet sides.
  • Maximum allowable temperature of cargo and adjacent tanks.
  • Stresses (SF, BM and torsion stresses) and sloshing loads at all stages of loading, discharging and carriage.
  • Number of slack tanks and their effect on stability and sloshing. Limitation on number and location of slack tanks shall be highlighted.
  • Load and /or discharge rate, maximum allowable pressure, ballasting/de-ballasting operations, venting requirements, and communication facilities available.
  • Final ullages of tanks
  • Distribution of cargo, pipelines and pumps to be used, critical stages of operation, emergency stop procedures and notice for change of rate.
  • All precautions for safety including PPE, fire protection and firefighting agents.
  • Personnel available for cargo duties and delegation of such duties.
  • Suitability of tank material and material of equipment in the tank.
  • The terminal and ship information exchange.
  • The Master must have in writing from the Terminal Representative, whether the final stop shall be a shore stop or a ship stop.
  • Any other precautions required for the cargo
  • Actions in the event of an emergency and Emergency stop procedures
  • Emergency spill procedures and spill containment
  • Precautions against static generation
  • Line clearing, pigging and blowing procedures with associated hazards.
  • Cold weather precautions
  • Special precautions required for the particular operation

Guidelines set in the ICS Tanker Safety Guide (Chemical) guidelines shall be referred to while preparing the cargo plan.

The final Cargo Stowage Plan and the loading/discharging plan shall be available during the Ship-Shore interface meeting. The information contained therein, especially those with regard to communications and co-ordination between ship and shore must be discussed as a part of the Ship-Shore information exchange.

When planning cargo stowage, below 2 flow charts can be of help. If you plan your cargo stowage plan meeting all the requirements as per the flowcharts will result in compliance with the requirements of IBC or BCH code.

Allocation of tanks for loading products respectively

Sometimes the Charterer also provides a stowage plan, the same shall be verified and confirmed to be safe and environmentally compliant. If any part of the plan is unacceptable, the vessel shall inform the Charterer of the same citing the reasons. A modified plan shall be forwarded to the charterers, also at the same time is advisable to inform the company as soon as possible.

Related Post:  Importance of Separation and marking of Cargo

The vessel should prepare a stowage plan on the basis of a quantity instructed by the Charterer. In some cases, it may happen that the vessel is given a different cargo figure after berthing. In such cases the charterers must be contacted and ascertain the correct figures to be loaded and / or nominated. In no case the vessel should decide the quantity to load, again same should also be informed to Company.

Cargo Quantity

The maximum cargo allowable for the draught as permitted by the Load Line Rules for applicable voyage and the Charter Party must always be loaded. The draught to which the regulations apply is the observed draught amidships, and not mean of the fore and aft drafts.

Unnecessary extra quantities of bunkers, fresh water, stores and ballast are to be avoided to enable maximum dead-weight cargo to be loaded.

Frequent checks should be made to accurately assess the weight of consumable stores against the constant in the stability information.

Density of Water

On each occasion of loading the density of seawater is to be established from a sample (from at the depth of half of mean drafts) taken in adequate time before completion of loading. Any necessary allowance should be calculated and its effect allowed for when calculating the completion ullages.

Segregation

Reactivity with other cargoes

Incompatible cargoes may react dangerously with each other. Hence, such cargoes must not be stowed in adjacent cargo tanks or allowed to mix in slop tanks after tank cleaning or in drip trays. While the USCG table gives general indications, the footnotes and data sheets for any two particular cargoes should always be consulted because there are exceptions to the compatibility Chart. The compatibility of one chemical with another shall be checked by referring to the Compatibility Chart and Exceptions to the Chart (Appendix I) of U.S.A. CFR 46 Part 150. These can also be found in the ‘Chemical Data Guide for Bulk Shipment by Water’ (USDT).

Below is Compatibility Chart from USCG

Cargo Compatibility Chart as per USCG 46 CFR part 150

 

Segregation of cargoes reactive with water

Reactivity with water must be checked prior making the loading plan. A dangerous reaction caused by contact of the chemical with water or moisture may be a major safety hazard. Leakage of water into the cargoes may cause hydrolysis of the cargoes resulting in increased corrosivity. Such a reaction may result in deterioration of cargo quality, damage to tank equipment and coating.

Cargoes reactive with water must be segregated from the water by a barrier space and tanks which contain water such as fresh water tanks, ballast water tanks, or heavy weather ballast water tanks, slop tanks containing tank washings, etc. Water or steam should be avoided as a medium for heating. Drip trays must be kept dry when such cargo is loaded on board.

Segregation of cargoes affected by heat

Some cargoes are self-reactive and when subjected to heat may behave dangerously. In some other cargoes there may be a deterioration of quality. Heated cargoes should never be loaded adjacent to cargoes susceptible to self-reaction such as polymerization, decomposition, thermal instability, quality issues etc.

So far as possible, heated cargo should not be stowed adjacent to cargo tanks which contain a cargo of low boiling point or tanks containing toxic and /or heat sensitive cargo so as to avoid the possible release of cargo vapour into the environment. This may result in loss of cargo and/or collection of vapour deck areas

Filling Limits of Cargo

During the passage, the vessel may transit through areas with varying temperatures. It is necessary to calculate the ullage to which the tanks are to be topped off and due allowance must be made for increase in volume as temperature increases during the voyage either due to climatic conditions or cargo heating. On the other hand, excessive allowance must be avoided.

So far as possible, a cargo tank should never be loaded beyond 98 % of its capacity, even after allowing for increase in volume due to expansion. Loading, therefore shall be such that at no stage of the voyage is any tank 100% full.

The highest temperature during the voyage is determined from the various navigational publications available on board for the particular month or season. Trim of Vessel in expected loaded conditions is to be taken into consideration.

Related Post:  Important Items to be checked by Duty Officer during Rounds

IBC Code Chapter 15 States that:

  • No cargo tanks shall be more than 98% liquid-full at the reference temperature (R).
  • The maximum volume (VL) of cargo to be loaded in a tank shall be:

VL = 0.98 V (Pr/Pl)

where:

V = volume of the tank

Pr = density of cargo at the reference temperature (R)

Pl = density of cargo at the loading temperature

Load density of cargo tank

Cargo Tanks are designed to take a limited amount of load. Hence, specific gravity of a cargo plays a very important role in the final loading condition of the tank. It is necessary to take into account the correction between the design specific gravity (DSG) of the cargo tanks and the specific gravity (SG) of the cargo loaded. The design specific gravity of the tank will be available in the approved Loading Manual and Appendix to the Classification Certificate.

The maximum volume to be loaded will be calculated by the following formula:

Max. Volume to load (% full) = (Design Specific Gravity/Specific Gravity of the cargo) x 100

The formula gives you an percentage of Maximum Volume to Load, so on behalf of the volume you will have to calculate the Ullage.

For Example: Design Specific Gravity of Tank is 1.025 and Cargo to load has a Specific Gravity of 1.5 the Calculation Comes to (1.025/1.5) x 100 equals 68.33%. So 68.33% Volume of Tank can be filled.

Sloshing Strength of Cargo Tank

So far as possible, partial loading between 20% and 80% of tank volumes shall be avoided to ensure that there is no excessive sloshing load on the tank structure. It is also important to note the specific gravity of the cargo when keeping tanks slack.

However, if partial loading is involved in the intended plan, cargoes should be loaded to the extent of safe loading percentages as determined after referring to the sloshing calculation or the sloshing diagrams, after consultation with the Loading Manual and Stability data of the vessel. Percentage of stow in a tank must be reflected in the stowage plan.

Chemicals to be Carried for the First Time

Whenever  a chemical cargo is carried for the first time, the cargo must be reviewed. The review is based on the MSDS obtained from the manufacturer and any other source. Confirm that chemical cargoes listed in vessel’s COF.

As soon as the cargo bookings are received the Master and Chief Officer shall study the MSDS of the chemicals concerned, identify the main hazards of the cargo and precautions to be taken. Once all information on the product is gathered a crew meeting should be conducted and the chemical to be carried is discussed with regards to its safe handling, stowage, hazards and precautions. All safety information regarding cargoes carried on board must be readily available to all crew members.

The risks should be minimized as far as practicable, utilizing the best information, knowledge, technology and the guidance available from various sources. All necessary information on procedures and arrangements must be exchanged and agreed with the shore personnel, terminal personnel and other parties concerned prior to commencement of the operation.

Tripartite Lists

New products are continually being created and proposed for carriage. When there is need to transport a cargo which is not classified (IBC Chapter 17 or 18), the shippers must approach their Administration and request for a tripartite agreement to be established between the authorities of the shipping country, receiving country and the vessel’s flag state. Conditions of carriage not included in the COF are subject to this agreement. Such products have a potential to be eventually included in the IBC Code.

If a tripartite agreement is completed, the cargo is included in the MEPC.2 circular (Provisional Categorization of Liquid Substances), which is updated annually and published each December. The initiator has 3 years in which to provide all data to formally classify the cargo, failing which the agreement will expire.

MEPC.2 Circular should be available on board and reference should be made of relevant parts as required.

Cargo stowage planning on chemical tanker is complex job as  you have to look for a number of factors that need to be checked to ensure that chemicals can be loaded, carried and discharged safely.

Hopefully after reading this post, you will have rough idea as to what info and stuff you need to go while planning the stowage.

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