Within the gas trade, the ship/shore interface plays a vital part in operations. It is an area where differing standards and safety cultures may coexist.
- Supervision and control
- The terminal
- The ship
- Prior to arrival
- Alongside the jetty
- Discussions prior to cargo transfer
- Ship/shore safety check list
- Operational considerations
- Berthing and mooring
- Connection and disconnection of cargo hoses and hard arms
- Cargo tank atmospheres
- Cargo handling procedures
- Gangways and ship security
- Work permits
- Fire-fighting and safety
Supervision and control
There is no major difference between the general operation of a liquefied gas tanker and the operation of any other type of ship. However, in view of the hazardous cargo transported by a liquefied gas tanker, the crew must be trained to be extra vigilant and to consider at all times the potential risk under which the ship, its crew and its cargo are placed.
Close co-operation between ship and shore personnel is essential for the safe handling of a ship transferring cargo in a terminal. If the operation is well prepared and if open channels of communication are maintained between ship and terminal, there is a good chance that the transfer will be carried out smoothly and that any unexpected incident will be tackled promptly before it can develop into something more serious.
With respect to the equipment fitted on jetties, the ship/shore interface covers:
- Breasting dolphins;
- Hard arms and hoses;
- Ship/shore gangways;
- Emergency shut-down arrangements;
- Ship/shore links;
- Fire-fighting equipment capability.
Liquefied gases are loaded and discharged at many terminals around the world by a wide variety of ship types and sizes. Operations range from the very large self-contained LNG projects to smaller LPG terminals handling many different products.
During the design of a new marine terminal, minimum and maximum ship size is established. Furthermore, the jetty and its equipment are designed accordingly. Farther offshore, the port approaches and river channel are surveyed. Once a terminal is ready for service, the relevant information needed by visiting ships should be advised to the port authority, ship’s agents, pilots and ship owners associations.
Gas carriers are normally built in such a way that there is maximum compatibility with a range of terminals. Terminal personnel prior to acceptance of any nomination should always confirm compatibility of any particular ship and terminal from a technical viewpoint. Confirmation should include items such as mooring studies, manifold configurations and ESD link (Emergency Shut Down) compatibility.
Communications should start before the intended voyage and continue until the arrival of the ship alongside: they must also include the period of cargo operations and continue until the ship departs. All communications should be carried out in a common language so that misunderstanding cannot develop. Usually, apart from some coastal trades, this will be English.
Prior to arrival
As a ship approaches a port, direct contact should be established between ship and shore as soon as possible. Modern communications will readily allow the terminal to update the ship on its requirements for the envisaged transfer operation. Additionally, port requirements, berthing arrangements and the facilities available can also be advised.
Similarly, the shipmaster may inform the terminal of the cargo arrival temperatures and pressures, stores and bunker requirements and personnel joining or leaving. For the planning of ship cargo operations, the shipmaster should be advised by the terminal of all port and terminal requirements relevant to gas carriers.
Alongside the jetty
As for the earlier parts of a ship’s voyage described in the foregoing paragraphs, reliable and effective communications are a necessity once the ship is alongside.
While alongside and transferring cargo, various means of communication need to be agreed. Decisions must be made on the use of portable radios or telephones. These tools usually form the basis of good communications under normal operating conditions. However, emergency means of communication must also be developed and this will normally take the form of an established terminal operating procedure.
In many terminals, the actuation of emergency shut-down (ESD) valves is interlinked between ship and shore. This communication channel requires a suitable system having plugs and sockets fitted on ship and jetty. Both ship and shore need to be properly outfitted. Such methods of communication are recommended so that a controlled emergency shutdown can always be accomplished. This will always ensure that either the ship or shore emergency shutdown valve, whichever is nearest to the operational cargo pump, is closed first.
Discussions prior to cargo transfer
Before the start of any cargo transfer operation, the intended cargo handling procedures must be thoroughly discussed at a meeting held between the responsible personnel from the ship and the terminal. The purpose of the meeting is primarily to draw up a suitable cargo plan and to check on safety issues. Furthermore, the meeting has the benefit of making both sides familiar with the essential characteristics of ship and shore cargo handling systems. At the meeting, the envisaged operational and safety procedures and requirements should be covered. Finally, any limitations to be observed during the transfer should be noted in writing. Written agreements should include a cargo handling plan (including transfer rates), communication procedures, emergency signals, emergency shutdown procedure and the tank venting system to be used.
The content of the meeting will depend on a wide variety of circumstances but the following broad outline forms the normal basis for such meetings.
1 The names and roles of terminal and ship personnel who will be responsible for cargo transfer operations should be noted.
2 The terminal representative should check that pre-arrival instructions to the ship on cargo, cargo disposition and cargo arrival temperature have been carried out. They also check that all necessary ship equipment inspections and tests have been performed.
3 Similarly, the ship’s officers should satisfy themselves that the relevant terminal equipment is satisfactory and that appropriate inspection checks have been carried out.
4 The terminal representatives and, where necessary, customs and independent surveyors should be informed of the cargo tank data, such as:
- Liquid heel or arrival dip;
- Composition of tank vapour;
- Cargo tank quantities;
- Total quantity of cargo on board.
5 The ship and terminal should then discuss and agree in writing the quantity and types of cargo to be loaded or discharged and in what order. The anticipated transfer rates and, for discharge, the receiving tank allocations should also be agreed.
The cargo transfer operation should be planned and confirmed in writing in order to assure full mutual understanding. The items to be addressed should include:
- The order of loading or discharging;
- The total quantities of cargo to be transferred;
- The sequence of discharging and receiving tanks;
- The intended transfer rates;
- The transfer temperatures and pressures to be expected;
- The use of vapour return line.
6 To reconfirm earlier pre-charter advice, the previous three cargoes carried by the ship and the relevant dates should be noted in order to identify and assess any possible cargo contamination problems, particularly after ammonia.
7 The appropriate Cargo Information Data Sheets should be provided and should be posted in prominent places on board the ship and within the terminal.
Ship/shore safety check list
When a ship is alongside, no cargo operations or inerting should commence until the ship and the terminal have completed the international Ship/Shore Safety Check List and it has been confirmed that such operations can be safely carried out. It is normal practice that this checklist is presented to the ship by the terminal.
Recommendations on the Safe Transport of Dangerous Cargoes and Related Activitiesin Port Areas were revised by IMO in 1995. They refer to a comprehensive Ship/Shore Safety Check List covering the handling of bulk liquid dangerous substances with a special section for liquefied gases. It also includes guidelines for its completion.
Berthing and mooring
Berthing. Port and terminal authorities should establish berthing and unberthing criteria for safe operations, including limiting wind, wave, current and tide conditions. Requirements for the number and size of tugs must also be set.
Mooring. Mooring line configurations should be agreed as suitable. The initial mooring of the ship to the terminal and the subsequent tending of moorings is most important if the ship is to be safely held alongside and damage to transfer facilities and jetty prevented.
Connection and disconnection of cargo hoses and hard arms
Terminal equipment, such as hoses and hard arms, are designed to connect with the ship’s manifold. Irrespective of the type of equipment being used, there are certain operational procedures to be considered.
- No flanges should be disconnected or blanks removed until it is confirmed that line connections are liquid-free and depressurised and, where possible, inerted with nitrogen or other suitable inert gas.
- Care must be taken to avoid air or contaminants entering cargo pipelines.
- The manifold area of a gas carrier is a zone where flammable vapours may be present. Therefore, care must be taken to ensure that ignition sources are eliminated from this area.
Cargo tank atmospheres
Prior to any cargo transfer, the oxygen content in the ship’s cargo tank vapours should be carefully checked. As stated elsewhere in this book, at these times the oxygen content should never exceed five per cent and is commonly required to be not more than two per cent by volume in tanks containing vapour only. Lower oxygen contents may be required for cargo quality purposes.
For example, products such as butadiene and vinyl chloride, which can react with oxygen to form unstable compounds, require maximum oxygen concentrations of 0,2 per cent by volume and 0,1 per cent by volume, respectively.
Cargo handling procedures
Cargo handling is described in “Safety Precautions and Measures on Gas tankers”Safety Precautions and Measures but procedural aspects of these operations, directly relevant to the ship/shore interface, are considered here. All operations carried out alongside should be under the continuous supervision of experienced ship and shore personnel. These personnel should be familiar with the details, hazards and characteristics of the cargoes being handled and capable of ensuring that such operations can be safely and efficiently completed.
Facilities for instant and reliable communications (such as separate telephone, portable radio or VHF) between the ship and the shore control should be provided at all times during cargo operations. Before commencing operations, maximum cargo transfer rates have to be agreed. This should be done in accordance with vapour return specification, ship or shore reliquefaction capacity and emergency shut-down requirements. Inevitably, some of these considerations may be based on best practical estimates. Accordingly, during operations, a strict watch should be maintained on flow rates, tank pressures and temperatures. By means of ship/shore communications, adjustments to initial agreements can be made as appropriate.
If cargo transfer operations need to be stopped, this should be carried out under previously agreed controlled conditions with proper communication. If the situation demands an emergency shut-down, the agreed procedure should be followed, bearing in mind the dangers of excessive surge pressures. It is particularly important to maintain appropriate communication in emergency conditions and, if the responsible person becomes over-occupied in controlling operations, the communication task should be delegated to another officer.
Gangways and ship security
It is the duty of both the ship and the terminal to ensure that adequate and safe ship/shore access is provided. Where possible, the manifold areas should be roped off to limit the access of personnel to that area. The gangway should be located away from the immediate vicinity of the manifold and, ideally, should be positioned about midway between the cargo manifold and the accommodation. As appropriate, it should be rigged with a strong safety net beneath. Both on the terminal and on board ship it is good practice to provide a lifebuoy at the gangway entrances. Proper illumination of the gangway and its approaches should be provided during darkness.
A notice warning against unauthorised personnel should be posted at the gangway and provision should be made for all ship visitors to be met and escorted to the accommodation.
In general, on gas carriers, bunkering operations by barge will not take place during cargo operations as this is usually disallowed by terminal regulations. This avoids a bunker craft with possible ignition sources being allowed alongside the gas carrier. Bunkering from the shore can be carried out during cargo operations so long as shipside scuppers can be closed quickly. In case of cargo leakage open scuppers on gas carriers are an important feature to allow cold liquids to escape quickly so reducing the risk of metal embrittlement and the possibility of small pool-fires on a ship’s deck.
Oil tanker practice is to operate with scuppers closed and, in general, this standard is also applied to bunkering operations. It is therefore essential for gas carrier port operations to be properly considered in this respect and either suitable operational procedures must be in place or bunker tank openings and air pipes should be well bunded so that bunkering from ashore can take place during liquid cargo handling.
While a ship is alongside, only under exceptional and well-controlled circumstances should any hot work (including the use of power tools) be undertaken, either on board or within the vicinity of the ship. In the unlikely event that such work must be carried out, the most stringent safety precautions and procedures should be drawn up and rigidly adhered to. To cover these and similar circumstances, a Permit to Work system should be in place. In the event that hot or cold work becomes necessary when a ship is alongside, a Work Permit should be agreed between the ship, the terminal and, where necessary, the port authority. The Work Permit should cover a limited period and the terms and conditions for which it is issued should be rigidly enforced.
Fire-fighting and safety
When a ship is alongside a terminal jetty, it is important that a joint emergency plan be available. The preparation of such a plan is the responsibility of each terminal. The details of the plan should consider the appropriate actions to be taken in all envisaged emergencies. This should include communication with local emergency services and the port authority. A summary of the essential elements within the plan should be made available to ships’ personnel and an appropriate method of providing this information is by inclusion of suitable data in the Terminal Information and Regulation booklet.
Whilst a ship is alongside the terminal, fire-fighting equipment, both on board and on shore, should be correctly positioned and ready for immediate use. Although the requirements of a particular emergency situation will vary, fixed and portable firefighting equipment should always be stationed to cover the ship and jetty manifold area. As described in the Ship/Shore Safety Check List Guidelines, fire hoses should be laid out with nozzles attached; hoses from fixed dry powder units should be laid out; and portable fire extinguishers readied for immediate action. The international ship/shore fire connection should also be made available for use at short notice.
Water spray systems should be tested on a regular basis. Where water sprays are designed to operate automatically, in the event of fire, the functioning of the automatic devices should be included in the test. The ship’s firefighting and safety plan should be placed in a container near the gangway. This plan should provide the most up-to-date information. It is good practice to include a copy of the ship’s Crew List in the container.