| GTM-8.22 |
Gas Tanker Manual GTM Cargo Planning |
Form No.: GTM-8.22
Revision: 01 Date: 15 Oct 2024 Issued by: DPA Approved by: MD |
22 CARGO PLANNING
22.1 REFERENCE PUBLICATIONS
The following reference publications are to be read in conjunction with this section:
| Publication | Location |
|---|---|
| International Safety Guide for Oil Tankers and Manuals (ISGOTT) | Chief Officer |
| Tanker Safety Guide – Liquefied Gas (ICS) | Chief Officer |
| Liquefied Gas Handling Principles (SIGTTO) | Chief Officer |
| Ship to Ship Transfer Guide (Liquefied Gas) | Chief Officer |
| Guide to Port Entry | Master |
22.2 COMPANY FORMS
The following Company Forms are to be used in conjunction with this section:
| Company Form No | Title |
|---|---|
| SAF 20 | Deck Log Book |
| MAR 01 | Sea Passage Report |
| MAR 02 | Port Log |
| MAR 03 | Notice of Readiness |
| MAR 05 | Deadfreight Statement |
| MAR 06a | Letter of Protest Between Ship and Shore Figures |
| MAR 06b | Letter of Protest - General |
| MAR 08 | Cargo and Loading Discharge Plan |
| GAS 01 | Pre arrival and Commencement – Cargo Operations Checklist |
| GAS 02 | Loading Cargo Checklist |
| GAS 03 | Discharging Cargo Checklist |
| GAS 04 | Changing non compatible cargoes Checklist |
| GAS 05 | Liquefied Gases calculation Checklist |
22.3 GENERAL
Before and during all operations involving the cargo, ballast and bunkering systems, the Master must ensure that the precautions required by these operating instructions and relevant checklists are fully observed. Reference is to be made to the publications listed in this section as well as equipment operating and instruction manuals.
22.4 VOYAGE ORDERS
Cargoes are nominated on the basis of the ship’s recorded characteristics and there should be no difficulty under normal circumstances in arranging stowage. However, should a situation arise where nominated quantities cannot be stowed safely the Company, and if appropriate the vessel's Charterers must be informed immediately.
The fixture advice sent to the vessel will normally include “a minimum Charter Party quantity”. This figure is a contractual quantity. It is not an instruction to load that quantity. It is imperative that if a ‘maximum’ cargo quantity is advised to the vessel then this figure must not be exceeded. Conversely, if a “minimum” cargo quantity is advised to the vessel then at least that quantity must be loaded.
The quantity to be loaded must be strictly in accordance with the latest instructions received from the Company or the vessel’s Charterers. Should the Master consider he has not been given sufficient information, he is to request additional information from the Company or the vessel’s Charterers immediately. The Master must ensure that his Chief Officer is kept fully informed of any changes. Similarly, the Chief Officer must ensure that the Master is kept fully aware of any changes in quantities which are advised via the terminal personnel. Changes in cargo quantities received via the terminal or where the terminal nomination does not agree with the loading orders in quantities and/or grades must be confirmed with the Company and the vessel’s Charterers without delay.
22.5 PORT INFORMATION
The Master is to consult the Guide to Port Entry and the local Agent prior to arrival, for the current port details.
22.6 CARGO PLANNING
22.6.1 Cargo Plan
When planning the stowage of the nominated cargo the following are to be taken into consideration:
- Quantities and grades of the cargo to be loaded
- Cargo segregation requirements.
- Cargo tanks atmosphere requirements.
- Loading and discharge ports rotation.
- Trim, stress and stability during the intended voyage.
- Any draught restrictions in ports and throughout the passage.
- Expansion allowance for intended cargo (reference temperature).
- Any additional cargo care which may be required during the voyage.
22.6.2 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 must prepare and submit to the Master for approval a Transfer Procedure.
22.6.3 Cargo Loading/Discharge Plan
For quick reference throughout the cargo operations and in conjunction with the Transfer Procedure, the Chief Officer is to prepare a loading/discharge programme on Form MAR 08, which is to include, but not be limited to, the following:
- Quantity and grade of each parcel;
- Density, temperature and other relevant conditions, including the reference temperature which determines the filling limits;
- A plan of the distribution, quantities, innages, lines and pumps to be used;
- Transfer rates and maximum allowable pressures;
- Critical stages of the operation;
- Notice of rate change;
- Stability and stress information;
- Drafts and trims;
- Emergency stop procedures;
- Action to be taken in the event of a spill;
- Flammability and toxicity with references to cargo data sheets;
- Ballast operations;
- Protective equipment requirements;
- Hazards of the particular cargoes;
- Cargo pollution category;
- Quantity and grade of each parcel;
- Density, temperature and other relevant properties;
- Final ullages for all loaded tanks;
- The order of cargo/ballast tanks to be filled/emptied together with the expected time schedule showing which pumps (if applicable) would be in use;
- The number of controlled stages required depending on intended cargo operation and ship’s design;
- The required ballast condition for each stage of the operation;
- The expected stress, stability and draught conditions at each stage of the operation;
- The operating envelope of shore loading/discharging arms;
- Cooling requirements including rates of cool-down;
- Use of the cargo heater or vapouriser;
- Heel requirements after discharge;
- Under keel clearance limitations;
- Bunkering; and
- Special precautions required for the particular operation.
The Cargo Loading/Discharge Plan is to be approved by the Master and signed by each Officer involved in cargo operations. Junior Officers should whenever possible be actively encouraged to assist in cargo planning, line setting and the execution of ballast and cargo activities.
Pre-operations meeting shall be held with involved officers and crew to review and explain the plan, before arrival in port. This meeting shall be recorded in the Cargo Log Book.
This plan is to be discussed and agreed in writing with the terminal personnel as described in the current edition of the ISGOTT.
22.7 EXPANSION ALLOWANCE – REFERENCE TEMPERATURE (PRESSURIZED VESSELS)
Before loading commences, consideration must be given to the temperature of the cargo being loaded and to the maximum temperature, which may be expected on the voyage. Where there is a possibility that the cargo temperature will rise during the voyage, sufficient ullage space must be left to allow, with safety, for the increased volume of cargo resulting from expansion.
Cargo tanks must not be filled to more than 98% of the tank capacity, measured after necessary adjustments to the temperature of the cargo have been completed.
The maximum volume to which tanks may be filled is calculated using the following formula:
ρR
LL = FL ___
ρL
where:
- LL = loading limit expressed in percent, which means the maximum liquid volume relative to the tank volume to which the tank may be loaded.
- FL = filling limit = 98% unless certain exceptions apply.
- ρR = relative density of cargo at the highest temperature which the cargo may reach upon termination of loading, during transport or at unloading, under the ambient design temperature conditions.
- ρL = relative density of cargo at the loading temperature and pressure.
Temperatures predicted in this way are then taken as the saturated temperatures at a vapour pressure which is equal to the relevant tank pressures. To obtain the relative density of the cargo, standard tables are used. Predictions of cargo density during loading complete the information required to apply the IMO Code formulae given here above.
Refer to linked document Loading Limit Assessment for calculation guidance.
Refer to SIGTTO publication Application of Amendments to Gas Carrier Codes Concerning Type C Tank Loading Limits.
22.8 DENSITY OF WATER AT BERTH
The density of water in which the vessel is floating must be checked after arrival on any berth. This is particularly relevant on the loading berth, as the density of water will affect the amount of cargo that can be loaded. The hydrometer supplied to the vessel is to be used for this purpose.
22.9 CARGO TANK INSPECTIONS
Cargo tanks must be inspected before and after loading and discharging operations. These inspections normally include taking of ullages, pressures, and temperatures from the monitoring system. Inspection is to be carried out by a Shore Representative and the Chief Officer. An appropriate ullage Report must be completed by the Chief Officer and counter-signed by the Terminal Representative.
Letters of Protest must be issued in the case of discrepancies. In certain circumstances, the attendance of a P & I surveyor will be necessary, in which case the Company must be notified without delay.
22.10 CARGO SURVEYORS
It is normal and usual practice that independent cargo surveyors are appointed by Charterers, Shippers and/or Receivers to carry out tank inspections, calculating cargo quantities. The Company may also appoint an independent surveyor, particularly when the possibility of a dispute or claims exists, to protect the interests of the Company and Owners.
In the event that a surveyor appears to lack proficiency or safety awareness, this must be reported to the Company providing as much detail as possible.
Cargo surveyors almost always provide the ship with copies of their various papers. They must be kept together with the ship’s cargo papers voyage by voyage in envelopes.
22.11 ENDORSING CARGO SURVEYORS REPORTS
It is essential that great care is exercised when surveyors’ reports are presented for counter signature. The ship’s Officer must realize that he is not just being asked to witness a set of figures of measurements; he is, in fact, being asked to endorse the surveyor’s report “as agent of the ship’s owner.” He must not endorse it with a “clean” signature unless he is totally satisfied and in agreement with the details the report contains.
If he is not in total agreement with the surveyor’s report, the ship’s Officer must make a written comment on the form before he signs it, stating clearly what aspects of the report he does not agree with. Even if he is in agreement with the contents of the report, he is to endorse the document “for receipt only.”
22.12 CARGO DOCUMENTATION
Copies of all available cargo documents are to be kept together voyage by voyage.
22.12.1 Commercial Documents
The following list of commercial documents is normally in use on the liquid cargo trade:
- Bill of Lading
- Cargo Manifest
- Certificate of Quantity
- Certificate of Quality
- Certificate of Origin
- Statement of Facts
- Cargo Discharge Certificate
- and others
Some of these documents require to be signed or counter-signed by the Master. In such a case, it is the responsibility of the Master prior to signing to check the correctness of information contained within the document. In case of any doubts or questions regarding the commercial documents, the Master must refer to the Company for advice.
22.12.2 Ship’s Cargo Documentation
The following documentation related to cargo operations is normally to be completed by ship’s staff at each port of loading and/or discharging and forwarded to the Company and/or Time Charterers:
- MAR 02 Port Log
- MAR 03 Notice Of Readiness
- MAR 05 Deadfreight Statement
- MAR 06a Letter of Protest - Difference between Ship and Shore Figures
- MAR 06b Letter of Protest – General
- GAS 05 Liquefied Gases calculation Checklist
Company forms must normally be used for this purpose; however, when the vessel is on Time Charterer, the Charterers may place on board their own forms. In such cases, provided that their forms contain at least the same information as the Company forms, the copies of Charterer’s forms will be accepted by the Company.
22.13 PRE-TRANSFER SURVEY AND LOG ENTRIES
Prior to any transfer operation, a survey of the vessel and her cargo systems is to be carried out. The survey must include the examination and testing of all items listed in the relevant sections of ISGOTT, and as applicable to the vessel. Special attention must be paid to the following:
- Pump trips are to be tested prior to the commencement of each cargo operation and the result logged.
The majority of the items listed in ISGOTT are included in the standard ship/shore checklist; however, not all, and it is essential that Masters review the requirements of this chapter prior to arrival. Wherever possible, equipment tests are to be carried out prior to arrival.
The majority of checks cannot be completed until immediately prior to the cargo transfer operation, and the Master must ensure that these are carried out. On successful completion of all tests and checks and prior to commencing cargo operations, a log entry is to be made.
The above surveys are to be carried out under the supervision of the Chief Officer and Chief Engineer. Immediately prior to commencing cargo operations, the Chief Officer must personally assure himself of the correct setting of the valves in the cargo system. In the event of any problems, the Company is to be advised immediately.