Ballasting, loading or discharging operations carried out without recourse to opening ullage and sighting ports. During closed operations, ships will require the means to enable closed monitoring of tank contents, either by a fixed gauging system or by using portable equipment passed through a vapour lock.

A tank, compartment or container is gas free when sufficient fresh air has been introduced into it to lower the level of any flammable, toxic or inert gas to that required for a specific purpose, e.g. Hot Work, entry etc

Means the introduction of fresh air into a tank with the object of removing toxic, flammable and inert gases and increasing the oxygen content to 21% by volume.

Work involving sources of ignition or temperatures sufficiently high to cause the ignition of a flammable gas mixture. This includes any work requiring the use of welding, burning or soldering equipment, blow torches, some power driven tools, portable electrical equipment which is not intrinsically safe or contained within an approved explosion-proof housing, and internal combustion engines.

H2S is a very toxic, corrosive and flammable gas. It has a very low odour threshold and a distinctive odour of rotten eggs. H2S is colourless, is heavier than air, has a relative vapour density of 1.189, and is soluble in water.

A gas or a mixture of gases, such as flue gas, containing insufficient oxygen to support the combustion of hydrocarbons.

Nitrogen, N - 83%
Carbon Dioxide, CO2 - 12-14%
Oxygen, O - 2-4%
Other - less or around 1%

All equipment fitted to supply, cool, clean, pressurise, monitor and control the delivery of inert gas to the cargo tank systems.

An inert gas plant and inert gas distribution system together with means for preventing backflow of cargo gases to the machinery spaces, fixed and portable measuring instruments and control devices.

The Guide provides operational advice to directly assist personnel involved in tanker and terminal operations, including guidance on, and examples of, certain aspects of tanker and terminal operations and how they may be managed. It s is NOT a definitive description of how tanker and terminal operations are conducted.

The Oil Companies International Marine Forum (OCIMF) is a voluntary association of oil companies with an interest in the shipment and terminalling of crude oil, oil products, petrochemicals and gas.

The introduction of inert gas into a tank already in the inert condition with the object of further reducing the existing oxygen content and/or reducing the existing hydrocarbon gas content to a level below which combustion cannot be supported if air is subsequently introduced into the tank.

One of the most significant safety initiatives introduced by OCIMF is the Ship Inspection Report Programme (SIRE). This programme was originally launched in 1993 to specifically address concerns about sub-standard shipping. The SIRE Programme is a unique tanker risk assessment tool of value to charterers, ship operators, terminal operators and government bodies concerned with ship safety.

Airborne concentration of substances under which it is believed that nearly all workers may be exposed day after day with no adverse effect. TVLs are advisory exposure quidelines, not legal standards, and are based on industrial experience and studies. There are three different types of TVL:

Time Weighted Average (TLV-TWA) – The airborne concentration of a toxic substance averaged over an 8 hours period, usually expressed in parts per million (ppm).

Short Term Exposure Limit (TVL-STEL) – The airborne concentration of a toxic substance averaged over any 15 minute period, usually expressed in parts per million (ppm).

Ceiling (TLV-C) – The concentration that should not be exceeded during any part of the working exposure.

Equipment fitted to a tank to enable the measuring and sampling of cargoes without release of vapour or inert gas pressure.