Inert Gas Systems

Oil Tankers

By

Siddharth Sid Chandrasekar

How ?

Tanker Structures

CBT & SBT

SBT

Ballast water is taken on board to maintain stability, such as when a vessel is sailing empty to pick up cargo or after having unloaded cargo. Ballast water contained in segregated ballast tanks (SBT) never come into contact with either cargo oil or fuel oil

CBT

To have so-called dedicated clean ballast tanks (CBT) means that specific cargo tanks are dedicated to carry ballast water only.

Oil Discharge Monitoring & Control System

General Precautions on Tankers

Strict smoking regulations, no smoking signs

No naked lights outside accommodation

Portable UHF -intrinsically safe

Fixed electrical equipment - secure earth connections

General Precautions

Portable electrical equipment

Portable pumps and fans - can develop static charge

Clothing No static charge potential

Deck maintenance tools (grinders, grit blasters, chippers)

General Precautions

Main engine Soot blowing

Portable pumps and fans - can develop static charge

Aluminium based primer paints interact with the rust and provide an ignition source if subsequently stuck hard by a metal object

Mobile phones

General Precautions

Cold Weather Precautions anti freeze for deck seal & P/V breaker, fire mains drained

Enclosed Space Entry

Pumproom Entry Permits

Hot Work Permits

General Precautions

Arrival into Port

Pre arrival Ship-terminal questionnaire

Mooring System Checklist

Ship Shore safety checklist (ISGOTT)

Load / Discharge Operation Checklist

Checklists

Ship / Terminal Information Exchange Checklist

Handling of Cargo & Ballast

Constant supervision Ship & Shore

Cargo sampling Open & Closes systems

Correct line up

Incremental rate with further checks

Cargo Operations

Dont close valves against positive flow

Load / Discharge Plan

Obligations to MARPOL regulations & Ballast Water Management

Stability criteria, Free Surface Effect

Stresses and bending moments

Contamination (oil) of ballast water

Ballast Operations

Minimum depth at berth and stern trim

VECS

Collect and treat vapour via shore based infrastructure

The vapour return line ashore is fitted with sensors and alarms to monitor tank pressures

A flame arrestor will be fitted within the system on the shore side

A stud is located on the presentation face of the reducer flange prevents wrongful manifold connection

A different colour coding system

VECS

Inert Gas Systems

Inert Gas Systems

Why ?

Primary means of fire / explosion prevention on tankers

Maintain a low, positive pressurised, inerted cargo tank atmosphere at all times

Removes the possibility of oxygen entering the tank

Prevents the cargo tanks atmosphere from entering the flammability range

Inert Gas Systems

Types

Flue Gas Generator

Types

Inert Gas Generator

Inert Gas Systems

Basic flue gas composition:

O2 - content: Approx. 5% by vol.

CO2 - content: Approx. 13% by vol.

SO2 - content: Approx. 3000 ppm.

N2 - content: Balance

Inert gas composition:

O2 - content: No change

CO2 - content: No change

SO2 - content: Less than 100 ppm

N2 - content: Balance

Gas outlet temperature:

Max. 5C above sea water temperature.

Relative humidity: 100%

Carry over of water droplets: Less than 1 g/kg dry gas.

IMO requirement

Flammability Diagram

AB - Hydrocarbon gas/air mixtures without inert gas

C & D LFL & UFL of HC gas in air

CE & DE Explosive limit when IG is inserted

Purging

The introduction of inert gas into a tank already in the inert condition (O2