Page 45 - International safety guide for oil tankers and terminals

HAZARDS OF PETROLEUM

Threshold Limit Values (TLVs), sometimes referred to as Permissible
Exposure Limits (PELs). However, this latter term has been discontinued
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in this publication as operational procedures should be aimed at reducing
personnel exposure to a minimum and not to a permissible level.

exposure to TLV concentrations, the values are only guidelines. Bestย์นาวี
Exposure limits set by international organisations, national administrations
or by local regulatory standards should not be exceeded.

Industry bodies and oil companies often refer to the American Conference
of Governmental Industrial Hygienists (ACGIH) which has established
guidelines on limits that are expected to protect personnel against harmful
vapours in the working environment. The values quoted are expressed as
Threshold Limit Values (TLVs) in parts per million (ppm) by volume of gas
งานห้องสมุด ศูนย์ฝกพาณิช
in air.
In spite of the fact that serious health effects are not likely as a result of

practice is to maintain concentrations of all atmospheric contaminants as
low as reasonably practicable (ALARP).

In the following text, the term TLV-TWA (Time Weighted Average) is used.
Because they are averages, TWAs assume short-term exposures above
the TLV-TWA that are not sufficiently high to cause injury to health and
that are compensated by equivalent exposures below the TLV-TWA
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during the conventional 8 hour working day.
2.3.3.3 Effects

The main effects of low concentrations of petroleum gas on personnel
are headaches and eye irritation, with diminished responsibility and
dizziness similar to intoxication. At high concentrations, these lead to
paralysis, insensibility and death.

The toxicity of petroleum gases can vary widely depending on the major
hydrocarbon constituents of the gases. Toxicity can be greatly influenced
by the presence of some minor components such as aromatic
hydrocarbons (e.g. benzene) and hydrogen sulphide (H 2 S). A TLV-TWA of
300 ppm, corresponding to about 2% LFL, is established for gasoline
vapours. Such a figure may be used as a general guide for petroleum
gases but should not be taken as applicable to gas mixtures containing
benzene or hydrogen sulphide.

2.3.4 Material Safety Data Sheets (MSDS)
To assist ships’ crews in preparing for toxic cargoes, IMO has urged
governments to ensure that ships are supplied with, and carry, Material Safety
Data Sheets for significant cargoes. (See Bibliography for ‘Recommendations
for Material Safety Data Sheets for MARPOL Annex 1 Cargoes and Marine
Fuel Oils’.) The MSDS should indicate the type and probable concentrations of
hazardous or toxic components in the cargo or bunkers to be loaded,
particularly H 2 S and benzene.

The MSDS should be based on the standard IMO format.

It is the responsibility of the supplier to provide the relevant MSDS to a tanker
before it commences loading an oil cargo or bunker fuel. It is the ship’s
responsibility to provide the receiver with an MSDS for the cargo to be
discharged. The ship should also advise the terminal and any tank inspectors

© ICS/OCIMF/IAPH 2006 11