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Chemical tankers operation - voyage planning & required stowage guideline

Prior commencement of a voyage a ship master is by law and in practice ultimately responsible for the correct stowage of the cargo. He must take all parameters such as, but not limited to, the following when deciding on which tanks to use for the stowage of a particular cargo;

chemical tanker navigation at sea
  1. Stress, stability, trim and list
  2. Certificate of Fitness (check the list of chemicals attached to the certificate and confirm that the ship is certified to carry the cargo)
  3. IBC/BCH Code to be referenced and the carriage requirements of the cargo noted along with IMO classification etc
  4. Charterer’s requirements for the cargo
  5. If more than one tank is required, the total volume of the tanks chosen should as near as possible be the same, but not less than, the total volume of cargo, keeping dead space and ullage to a safe minimum.
  6. Certificate of Class to be cross-checked for ensuring chosen tanks have sufficient strength for high density cargoes
  7. Tank coating compatibility
  8. Heating requirements
  9. Heat adjacent restriction for the cargo
  10. Cargo sensitivity to adjacent tanks being heated or hot water washed
  11. Compatibility of different cargoes in adjacent tanks or common cargo piping, pumping or ventilation systems
  12. Last cargo compatibility; permission by charterers received especially when loading vegetable oils (FOSFA rules). Tank cleaning requirements
  13. Shipping Documents for each cargo to load
  14. MSDS for each cargo
  15. Antidotes and Toxic Gas detectors for the cargoes being handled as applicable
  16. Crew familiarity with the cargo to be handled

Cargo Quantities

The cargo quantities are planned by the Master and checked in relation to the voyage orders with regard to:
  1. Loading capacity (load calculation)
  2. International Load Line Zones in trading area
  3. Sheer force and bending moment stresses during the various stages of loading and discharging
  4. Draft and passage limitations en route, canals and in ports of destination

Filling limits of cargo tanks

Filling limits of cargo tanks is due to:

1) Load density limit of cargo tanks against cargo density

2) Density of cargo at maximum voyage temperature or discharge temperature against load temperature

3) IBC code limit of cargo quantity for ship Type 1 and 2 tanks.

4) FOSFA restrictions for minimum filling limits (>60% volume in order to consider last cargo) The filling limits of the cargo tanks due to temperature variations and overfill limits shall be complied with as per IBC code. In additions vessel shall comply filling limit restrictions due load density limits of cargo tanks as per Certificate of Class and Stability manual.

Cargo Quantity Options

Abbreviations are used in the instructions expressed as percentages and as follows:

Cargo equipment defects

It is the Master’s responsibility to inform the management office immediately regarding any cargo equipment defects which might influence cargo stowage. This is to prevent cargo commitments being made to which cannot be adhered to as a consequence of these defects.

Stowage Limitations of Cargo Tank Structure and Fittings on Chemical Ships

Attention should be paid to stowage limitations due to cargo tank structures and their fittings, i.e. the specifications of a cargo tank will limit product weights and quantities which can be loaded in that tank. Refer to ship specific Certificate of Fitness, also the BCH/IBC Codes, for lists of cargoes and tank types suitable for their carriage.

Oil and Hazardous Material Transfer Procedure

Prior to each transferring of oil or hazardous cargo to or from the vessel and from tank to tank within the vessel the Chief Officer has to prepare and submit to the Master for approval an Oil or Hazardous Material Transfer Procedure as required by 33 CFR 155.720. The contents of Transfer Procedure should comply with the requirements detailed in 33 CFR 155.750.

Typical voyage orders will contain the following elements: The Master must advise the management office of any doubt, disagreement or inability to comply, with the instructions.

Product tanker bow mecca
Fig:Product tanker bow mecca

It is the responsibility of the Master to plan equipment and supplies for the intended voyage such as, but not limited to the following:

The following reference publications provide useful information :

Related Info:

Cargo handling safe practice for chemical products

Ship & terminal pre-loading meeting prior loading /discharging

Cargo compatibility and reactivity of various chemical cargo

Poisoning and required first aid treatment onboard

Determining presence of contaminants in chemical cargo

Checklist for handling dangerous liquid chemicals in bulk

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