Problems with ship/shore compatibility
As described above, there can be incompatibility between terminal and ship pipeline systems. In practice the lowest allowable standard for pipelines and hard arms for many refrigerated terminal installations is the ANSI Class 150 pressure rating. This will normally provide for a 19 bar working pressure plus 33 per cent surge allowance. Ship pipework sometimes has lower ratings as described above.
6.6.5 Cargo surveyors
Independent cargo surveyors are often employed by cargo buyers or sellers and the survey companies provide personnel to check cargo operations and cargo quantities
both on board ship and within terminals. Such activities can include cargo measuring and cargo sampling (Reference 2.20).
During cargo operations, it is important to maintain a log of events. Ship's officers and shore personnel should ensure that their time records are in agreement and that, when independent cargo surveyors are used, similar times are recorded in the Surveyor's Time Sheet.
6.6.6 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 mid-way 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 (see Reference 2.23).
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 .
Ideally, a jetty should provide a secondary means of escape from the ship in case the normal access is unusable in an emergency. If the jetty configuration renders such secondary escape by gangway impossible, other means should be considered such as:—
• Preparing the ship's free-fall lifeboat for immediate lowering, or
• Rigging of the ship's accommodation ladder on the side away from the jetty.
The terminal, in liaison with the ship, should control the persons and vehicles entering the jetty area to ensure that only authorised persons with legitimate business are permitted access. In controlling this access, any local regulations concerning smoking, carriage of matches or lighters, the use of mobile telephones and pagers, and the use of cameras should be enforced. Similarly the ship's deck-watch should check on the side away from the jetty and report the approach of unauthorised waterborne craft coming into the restricted area.
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6.6.7 Bunkering
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 ship-side 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.
6.6.8 Work permits
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.
6.7 FIRE-FIGHTING AND SAFETY
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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 (see Reference 2.5).
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 fire fighting equipment should always be stationed to cover the ship and jetty manifold area. As described in the Ship/Shore Safety Check List Guidelines (see Appendix 3), 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 (see Appendix E of Reference 2.4) 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 fire-fighting 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.
6.8 LINKED EMERGENCY SHUT-DOWN SYSTEMS
As described elsewhere in this book, ESD systems are fitted at terminals and to ships. At the ship/shore interface, in order to enhance safety, it is recommended that these systems are compatible and that they be interlinked. This is usually accomplished by electrical connections although, in the LNG trade, fibre-optics are commonly used. For this arrangement to be appropriately assembled, both ship and shore need compatible systems; this also means that suitable plugs and sockets must be provided.
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The main purpose of a linked ESD system is to have safe ship and shore control over the entire ESD system. This is in order to ensure a safe shut-down in line with appropriate valve closure times.
The Guiding rules for limiting pressure surge on loading or discharging are:—
(1) To stop the cargo pump
(2) First close the ESD valve nearest to the pump
(3) Finally, close other ESD valves
This surge pressure control recognises the greater vulnerability of hoses or hard arms in comparison to the rest of the pipeline system.
As will be noted, the guiding rules are standard but the sequence of operations depends on whether the ship is loading or discharging. It will also be seen that to follow the procedure in a satisfactory manner, good coordination is required between the ship and jetty. It is accepted that without a linked system, in an emergency situation, such control is difficult and for this reason ship and shore ESD system should be interconnected.
The system logic engineered into a linked system must be designed to ensure an appropriate procedure is followed no matter which party initiates an ESD. (Details of such a system suited to LPG terminals is available from Reference 2.34. The particular system described in the reference has the advantage of being quite easily retro-fitted to existing plant and ships and is well suited to the many berths not so fitted in the LPG trade.)
The following tables outline the manual and automatic means by which an ESD should be activated: furthermore, the tables outline the signals which should be transmitted.
| ESD should be initiated by the following EMERGENCIES:-
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| SHIP | TERMINAL |
| Manual Trip | Manual Trip |
| Operation of manual trip | Operation of manual trip |
| Automatic Trip | Automatic Trip |
| Shut-down signal from ashore | Shut-down signal from ship |
| Overfilling of any cargo tank | Overfilling of receiving tank |
| Power loss to valve controls | Power loss to arm manoeuvring |
| Loss of control air pressure | Power loss to ERS |
| ESD valve moving from full-open | ESD logic failure |
| ESD logic failure | Fire in terminal area |
| Fire in cargo area | Loss of electric power |
| Loss of electric power | Ship movement — pre-ERS |
| Activation of the PERC | |
| High level in surge drum | |
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| ESD should initiate the following IMMEDIATE ACTIONS:-
| |
| ON SHIP Send shut-down signal to the shore Trip ship's cargo and spray pumps Trip booster pump (LPG) Trip vapour return compressor Start to close ship's ESO valve | ON TERMINAL (LOADING) Send shut-down signal to the ship via the ship/shore link Trip loading pump Open spill-back valves Start to close shore ESD valve ON TERMINAL (RECEIVING) Send shut-down signal to the ship Start to close shore ESD valve |
ESD Links are already well established at LNG ports. In the early LNG projects, ship and shore were coupled with pneumatic systems. These could be slow in operation and suffered from problems with dirt and moisture. These drawbacks led to the development of electric or electronic and optical links. Accordingly, there are now four main types in operation:—
• Pneumatic types
• The electrical type (either intrinsically safe or of increased safety)
• The fibre optic type, or
• Those operated by radio telemetry
Regardless of the cargo to be handled, it is vital, prior to receiving a new ship at a terminal, to communicate on the question of the compatible systems being fitted at the terminal and on the ship.
6.9 TERMINAL BOOKLET — INFORMATION AND REGULATION
This chapter has outlined a number of terminal-based procedures which should apply to any well-run ship/shore operation. For the purposes of clear and unambiguous operations many terminals produce a Terminal Information and Regulation booklet.
Such guidelines can be helpful for defining the responsibilities of each party and can be used for introducing local procedures. A booklet of this type can be subdivided as follows:—
Information
• Port geographical position
• Restrictions on port entry
• Ship restrictions at the berth
• Weather and tidal data
• Preferred mooring plan
• Diagram of jetty fire-fighting and life-saving appliances
• Procedures for limiting surge pressures
• Terminal pipeline and tankage plan
• Description of ESD arrangements
• Communication methods
• Requirements for a ship/shore ESD Link
• Cargo pumping limitations
• Safety requirements
• Emergency procedures
Regulations
Regulations may include national and port authority requirements. They can also include many of the safety issues described in Chapter Six of this book.
Documentation
• Letter to shipmasters (see Appendix 3)
• The ship/shore safety check list (see Appendix 3)
• A cargo planning form
• A cargo calculation form
For further information on this subject terminal managements can turn to Reference 2.31 and 2.42.
6. 10 TRAINING
The training of seagoing personnel is covered by international regulation under course syllabuses prepared under the auspices of IMO (see References 1.5, 1.8 and 1.9). Further more, basic training is provided for seafaring ratings in Reference 2.2. For terminal personnel, similar training is recommended and in this respect Reference 2.19 has been published by SIGTTO for the benefit of marine terminal managers and training personnel in the gas industry.
Chapter 7
Cargo Handling Operations
This chapter takes the reader through a complete cycle of ship loading and discharging operations, from a gas-free condition until a change of cargo is planned. In addition, recommendations for ship-to-ship transfer operations are provided. The text ties together much of what has been written in earlier chapters so that personnel can appreciate how the various equipment and procedures fit within operational practices.
When a gas carrier first comes alongside a berth to carry out cargo handling operations, it is essential that the preliminary procedures as outlined in Chapter Six be properly completed. In particular, the questions given in the Ship/Shore Safety Check List should always be addressed. In line with check list questions, cargo handling plans should be developed and agreed jointly. Furthermore, written procedures should be established for controlling ship/shore cargo flow rates and for procedures covering general emergencies. It is in accordance with these plans that safe operations, as outlined in this chapter, can be ensured.
7.1 SEQUENCE OF OPERATIONS
Assuming a gas carrier comes directly from a shipbuilder or drydock, the general sequence of cargo handling operations is as follows.
7.2 TANK INSPECTION, DRYING AND INERTING
7.2.1 Tank inspection
Before any cargo operations are carried out it is essential that cargo tanks are thoroughly inspected for cleanliness; that all loose objects are removed; and that all fittings are properly secured. In addition, any free water must be removed. Once this inspection has been completed, the cargo tank should be securely closed and air drying operations may start.
7.2.2 Drying
Drying the cargo handling system in any refrigerated ship is a necessary precursor to loading. This means that water vapour and free water must all be removed from the system. If this is not done, the residual moisture can cause problems with icing and hydrate formation within the cargo system. (The reasons are clear when it is appreciated that the quantity of water condensed when cooling down a 1000m3 tank containing air at atmospheric pressure, 30°C and 100% humidity to 0°C would be 25 litres.)
Whatever method is adopted for drying, care must be taken to achieve the correct dew point temperature — see Table 2.3(b). Malfunction of valves and pumps due to ice or hydrate formation can often result from an inadequately dried system. While the addition of antifreeze may be possible to allow freezing point depression at deep-well pump suctions, such a procedure must not substitute for thorough drying. (Antifreeze is only used on cargoes down to -48°C; propanol is used as a de-icer down to -108°C but below this temperature, for cargoes such as LNG, no de-icer is effective.)
Tank atmosphere drying can be accomplished in several ways. These are described below.
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