Fig: Chemical tanker high level alarm mounting on deck
Care must be taken as tanks become full, especially when loading a product into more than one tank simultaneously, due to
the increased risk of an overflow while topping off. High level alarms and tank overflow control alarms are safety critical
items, and loading should be stopped if it is suspected that either is not working correctly.
The responsible officer must ensure that tanks that have been topped off are properly isolated from tanks still being loaded.
Cargo tanks which have been topped off should be checked frequently during the remaining loading operations to detect
changes in liquid level, and to avoid an overflow.
When nearing completion of loading the shore should be notified and, if necessary, the loading rate reduced.
Clearing cargo hoses
When clearing the line after loading a static accumulator cargo, it is desirable to minimise the introduction of gas into the tank
which will bubble up through the cargo
If nitrogen is used to clear the cargo hose after loading a cargo treated with an inhibitor that depends on oxygen, care should
be taken to minimise the volume of nitrogen entering the cargo tank. Not only may bubbling the nitrogen through the liquid in
the tank deplete the dissolved oxygen and affect the inhibitor by requiring it to take oxygen from the atmosphere in the ullage
space, but it is also possible that excessive nitrogen will linger in the ullage space.
The loading line is always blown through with either compressed air, steam or nitrogen, depending
on the cargo, to empty it between manifold and terminal. This is necessary to ensure
risk-free release of loading arm or hose connection. If possible the vessel’s line system used
should also blown empty this way. With heated or solidifying cargoes this is a must.
In case of high viscous cargo it is important to be aware that after line blowing the cargo may
contain an air-bubble and therefore the ullage measured immediately after blowing is less
than actual (Vegetable oils) giving higher volume of cargo onboard than actual. Pre-blowing and
after-blowing ullage measurements should give a good indication of this. The tank in question has
to settle before a correct ullage can be taken. If this is not possible or cannot be ascertained, the
ullage report to be remarked of entrapped air in the cargo giving higher volume in ship tank.
At some installations the landline from tank farm to jetty manifold or part of it are
It is possible that large amounts of cargo are pressed into a cargo tank at high rate
and high pressure. Method and required tank volume necessary for this shoreline emptying must
be agreed upon in the pre-loading conference. Especially one must be aware of the high pressure
which could be created when pigging and take precautionary measures to prevent overpressurising
the tank or creating an overflow, by venting the tank during this operation and
throttling manifold valve to control flow.
Fig: cargo handling gears
Completion of loading & final measurements
When loading is completed the final loading measurements have to be carried out. In order to
clear the shore and vessel’s cargo line free from product, the lines are blown from the shore.
Cargos sensitive to Oxygen are given a nitrogen blanket following loading. The surveyor
together with an officer will take the ullage and cargo temperature of the tank(s) concerned. In
the presence of an officer cargo samples are taken sealed and labelled.
- Loading the manifold valve must be closed
- In cases where the shore line is emptied by either “blowing” or “pigging” the product
into the ship tank(s) the responsible officer must ensure that the tank(s) have
sufficient space to accommodate the quantity in the shoreline.
- Blowing” or “pigging” can cause a pressure surge and the responsible officer must
monitor this operation carefully in order not to over-pressurize or overflow the tank.
- During customary ullaging and sampling the responsible officer must ensure that
that this activity is conducted as per local and/or international regulations and that
proper personal protective equipment is used.
- Disconnecting of shore hoses or arms must only take place after they have been
drained for cargo residues and relieved of any pressure after blowing/pigging.
- Personnel engaged in hose disconnection must wear proper personal protective
- Cargo heating system should be tested as required.
Disconnection of cargo hoses
After the transfer of a chemical cargo is complete, established procedures should be followed to minimise residues in the
line, and especially in the cargo hose or cargo arm between ship and shore. Disconnection must only take place after draining
of cargo residues and relief of any pressure, even before emergency disconnection if at all possible.
Disconnection of the hose or cargo arm at the ship's manifold is a time when the cargo containment system is deliberately
breached. Although hose disconnection is a routine operation that must be performed, it should be regarded as comparable to
opening up any other cargo pipeline on deck. Personnel engaged in hose disconnection should wear protective equipment
appropriate to the hazards of the cargo involved which, for a highly toxic cargo, will include a full chemical resistant suit and
Preparation for sea voyage
- Cargo samples :
are to be stored safely in the designated sample store / locker. Storage
elsewhere in cargo office or accommodation is not allowed. Cargo samples should
not be brought into accommodation.
- Manifold :
blind flanges on the manifold have to be fitted and fully bolted.
- P/V Valves :
The valve setting should be in accordance with C.O.F.
- Hoses – If time permits :
All loading hoses, jumper hoses, have to be disconnected. If vessel’s hoses have been
used, these hoses should be cleaned at sea and thereafter fitted with blind flanges.
Thereafter hoses are to be stowed for the sea-voyage.
Hoses on the vapour return line, between central vapour return line and specific
tank in the towers, when applicable have to be removed. The vapour return line
has to be fitted with blind flanges wherever applicable.
- Tank alarms :
Tank alarm system to be switched off.
- Tank closures and openings :
All tank hatches butterworth hatches etc. have to be checked that they are closed
before commencing the sea voyage.
In general, a round over deck should be made by a responsible officer to check that the cargo area
is seaworthy in all respects.
Technical readiness prior loading operations
Before loading any cargo, check Certificate of Fitness, heating requirements, cargo & coating compatibility, density.... Make sure that you can load it!
Strictly review cargo documents, including viscosity and melting point.
Preparation for cargo operation
Ship checks prior to arrival
: When approaching a port to load or discharge cargo, the following important checks should be made by the ship in time to allow any necessary work to be done:
Preparing a cargo tank atmosphere
The correct atmosphere in a tank, can be established either inerting to prevent the formation of flammable mixtures of cargo vapour and air, or padding to prevent chemical reaction between oxygen and the cargo. It may also be necessary to reduce the humidity (dewpoint) of the atmosphere within the cargo system.
Ship & terminal pre-loading meeting prior
The complexity of loading/discharging operations on chemical tankers makes it necessary to plan all activities in which vessel and terminal are involved. Parties involved are from terminal a loading Master, from ship Master/Chief officer & an expert surveyor. ....
Handling various grade liquid chemicals during loading
Loading of various noxious liquid chemicals involved numerous hazards. It is important to exercise safety during all stages of cargo loading. ...
Checklist for handling dangerous liquid chemicals in bulk
Information on the product to be handled should be available on board the ship and ashore before and during the operation. This information should include:
Cargo is bought and sold in various units of measurement. These may be Barrels (Bbls) at 60F, Cubic metres (M3) @ 15C, Metric Tonnes in Vacuum, Metric Tonnes in Air and Long tons in Air.
Different methods of calculation for various substances can be applied, but they must be similar for loading and discharging.....
Risk & hazards of chemical contamination onboard
Modern tankers are often equipped with individual submersible cargo pumps but if these are connected to common or shared lines there is still a risk of contamination.
Cargo unloading operation safety precautions
Just prior to commencing discharge the responsible officer should check that the cargo pipeline system is set correctly, that correct valves are open, that valves not being used are closed, and that the cargo venting system is appropriate for the cargo operation. Particular attention should be paid to ship's cargo discharge equipment, such as pumps and pumproom ventilation
Liaison between ship and shore
Operations concerning cargo handling, tank cleaning and pre-wash, ballasting and bunkering require an exchange of information between the ship and terminal before the ship arrives or after arrival. .....
Ship shore safety checklist while alongside a terminal
Cargo loading and unloading operation of seagoing chemical carriers involved numerous critical procedure that need to be precisely monitored. Below Ship /shore check items are described as guidance only.
- IBC Code / BCH code
International Safety Guide for Oil Tankers and Terminals (ISGOTT)
ICS Chemical Tanker Safety Guide
Ship’s “Procedure and Arrangements Manual” (Approved by Class)
Certificate of Fitness for the Carriage of Dangerous Chemicals in Bulk
Ship’s “VEC System Operational Manual” (Approved by Class)
Ship to Ship Transfer Guide (Petroleum)
Tank Cleaning Manual
More info pages:
Handling self reactive chemicals
Cleanliness: Before loading self reactive substances onboard chemical tanker, a responsible Officer must ensure that there are no traces of other substances, which may promote self-reaction of the cargo to be loaded in the cargo tanks and the cargo systems.
....Handling of toxic chemical cargoes
A toxic substance is one which is liable to cause either harm to human health, serious injury or death. Toxic means the same as poisonous. Toxicity is an intrinsic property of a chemical, which man cannot modify, and its effect is a function of exposure. In some cases, correct response to its effects after exposure can diminish its consequences.
Cargo hoses handling ,connection and use
A modern cargo hose represents skilled engineering and, unless wrongly used, can be relied upon to contain the cargo. Nevertheless, it should always be treated as the weakest link in the cargo containment and transfer system, so correct handling and use of hoses is important. ....
How to prevent cargo pipeline leakage
There are many reason that may lead to cargo line failure on board chemical tanker. Galvanic corrosion in the cargo and stripping pipelines may cause several leakage. One of the sources of such corrosion in pipelines is variation in corrosion resistance at adjacent points in the piping. .....
Cargo line clearance requirement for chemical tankers
The lines used for cargo operations must be cleared and the pressure released to prevent solidification, polymerisation, reaction, pitting and danger to personnel connecting and disconnecting hoses or taking samples.
Closed loading requirement of various grade liquid chemicals and related considerations
Closed loading/discharge means loading or discharging with securely closed ullage, sounding and sighting ports. Additionally the venting must be controlled.....
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