PART ONE: CARGOES, SHIPS AND LEGISLATION (EDITION 3)
Code No 951
Time: 18 Mins
Transportation by sea is essential and forms a considerable proportion of sea trade
round the world. The typical design features of a chemical tanker ensure that the
particular containment needs are met. For example, stainless steel tanks and
separate pumping systems for each tank.
The video then describes the different types and classes of chemical tankers and
their suitability for carrying chemicals. It discusses typical cargo characteristics of
four compounds that are respectively flammable, toxic, corrosive and self-reacting.
The importance of checking the cargo data sheets, displayed on board ship for each
voyage, is emphasised.
These cargoes require special handling during loading, discharge, and throughout
the voyage. A cargo’s characteristics will determine whether it can be accepted, and
how and where it should be loaded, as well as the operational precautions and
emergency procedures to be taken into account. Cargo compatibility is important
and in this context we deal with ignition sources and fire prevention, flammable
vapours, etc.
The video then considers a corrosive liquid cargo, the hazards associated with toxic
cargoes, the safe operational practices which relate to these, and the monitoring of
inhibitor levels in self-reacting cargoes. The video concludes with a brief description
of the relevant controlling regulations as a source of further information.
If, despite precautions, the cargo does escape, crews need to be familiar with the
emergency procedures to reduce any pollution of the ship and its surrounding
environment.
For all four cargoes, the approach is detailed in the context of cargo loading, carriage
conditions and cargo discharge. The coverage extends to some of the practical as
well as the regulatory requirements in terms of cargo categories given in Marpol
Annex II. These include conditions laid down for stripping and tank washing of the
various categories of cargoes likely to be carried on board chemical tankers.
The program also highlights those sea areas where tank washing and effluent
dispersal are restricted.
TANK PURGING AND LINE CLEANING ONBOARD CHEMICAL TANKERS
Code No 752
Time: 23 Mins
This training package deals with the hazardous subject of handling shore supplied
nitrogen on board ship, in the context of tank purging, blanketing and cargo line
clearing, when there is a danger of tank over pressurisation.
The nitrogen is usually supplied at high pressure (16 bar) and at high flow rate.
Agreement on the procedure for handling the nitrogen is paramount, and should be
part of the pre-loading checklist between ship and shore, with emphasis on firm
parameters for transfer rate and pressure. Although the operation is an important
stage in cargo handling, it is also potentially hazardous. This is because tanks on
chemical tankers are not designed to withstand internal pressure, so the structure
could fail at less than 0.5 bar overpressure. The associated risks of the operation
need to be thoroughly understood.
The video takes the viewer through the typical phases of nitrogen and cargo control
in a loading port and a discharge port. It highlights the critical moments and how to
ensure that these are controlled safely in the Cargo Control Room, in the Terminal
Control Room and at the manifold.
Some of the topics included are communication between terminal and ship, how to
start the nitrogen supply, how to increase it to agreed volume, how to slow down and
stop the supply prior to loading cargo. A similar process is illustrated with cargo
loading, including cargo line clearing. It is normally the terminal's responsibility to
control the pressure and volume of nitrogen and line clearing is done towards the
ship's tank and not the shore tank. Pigging and line flushing are covered. In a
discharge port, it is assumed that the ullage space must be filled with nitrogen as
the cargo is being discharged.
In all cases it is established that if the tank atmosphere contains cargo vapour which
is prohibited from being vented into the atmosphere, it must be returned to shore
containers. In such cases the flows into and out of the tank must be balanced by
shore control. The video is accompanied by a supporting booklet. It supports the
STCW Code, Chapter V, Section A-V/1.
Working on board a chemical tanker has special dangers due to the variety of
hazardous cargo this type of ship can carry.
Safe working practice on board chemical tankers is largely defined by the mixture of
cargo carried at any given moment, and it is therefore critical that everyone on board
knows exactly what cargo is carried. This video package demonstrates to all on
board what could happen if this cardinal rule is ignored. The program illustrates the
‘fate’ of a seaman who ‘gambles’ with safety when the cargo includes flammable
corrosive and toxic substances. He blows himself up, gets sprayed with acid and gets
poisoned inside a tank where toxic fumes are present. All this, because he ignores
some of the simplest safety rules appropriate in most situations.
For example, he carries his metal tools in unsafe containers, he wears no safety
helmet, chemical suit or gloves; he is more interested in listening to his CD on the
main deck! He enters a tank without an entry permit, he tells no-one about his
intentions and ignores all the safety rules applicable when entering enclosed
spaces. He gets more than he bargained for!
The video, having shown in graphic images what can happen if you ignore safety,
then shows how to carry out these operational procedures without ‘gambling’ with
safety. The same seaman is seen following all the safety procedures stipulated on
his entry permit. He has has become a safe and effective member of the operational
team on board his ship.
This training package explains the importance as well as the complexity of effective
tank cleaning on chemical tankers. It shows that efficient tank cleaning is
important to ensure that the cargo to be loaded will remain within specification
during the voyage and the discharge. Tank cleaning is also important to ensure that
the cargo is carried without danger to the ship, its personnel and other cargo on
board.
The video considers the many factors that must be taken into account during the
planning stages of tank washing - among them are:
the construction of the tank walls
the nature of the last cargo
the washing medium
the cleaning processes to be applied
the appropriate techniques to be employed, the time available for cleaning and
the nature of the next cargo to be loaded
All these need to be considered in the light of the current regulations including
MARPOL.
The planning process is further complicated by the possible combinations of last
cargo and next cargo, ranging from easy chemicals to high-grade chemicals, to CPP,
vegoils, molasses and caustics. The task for the officers in charge is to select and
employ the correct tank washing and testing procedures every time, without fail, as
the price of errors can be high in terms of human life and commercial losses.
Having discussed the complexity of the planning process, the video describes the
relative simplicity of the actual washing process. By gathering the relevant facts and
strictly following the rules and procedures laid down in the controlling literature
available on board ship, the washing itself should be straightforward.
The most important sources of information are listed. These include:- the
Company’s Tank Cleaning Manual, The Cargo Data Sheets, MARPOL Annex I & II, US
Coast Guard Chemical Data Guide for Bulk Shipment of Chemicals, Dr Verwey’s
Guide, the Cargo and Oil Record Books and the ship’s Tank Cleaning Record Book.
How these documents are used in the planning and execution of tank washing is the
key component of the video. A typical procedure for getting from a dirty tank used for
carrying vegetable oil to a safe clean one, ready to transport methanol, is illustrated
in the video. Finally, reference is made to a number of special last cargo/next cargo
situations where the tank washing processes differ considerably from the sample
case shown.
Code No 951 
Time: 18 Mins
Code No 952 
Time: 23 Mins
Code No 595