The Safe Transfer of Liquefied Gas in an Offshore Environment (STOLGOE)

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Published Date

October 2010

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The Safe Transfer of Liquefied Gas in an Offshore Environment (STOLGOE)

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This is a guide to the transfer of Liquefied Petroleum Gas (LPG) between Floating (Production) Storage and Offloading (F(P)SO) facilities and conventional gas tankers. It covers every stage of the operation, including pre-arrival procedures, berthing and mooring, cargo transfer, unmooring and departure, gas-up and cooldown. It also discusses operational and personnel safety and emergency preparedness.

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This publication primarily addresses side by side (SBS) operations where the gas tanker moors alongside the F(P)SO. It includes recommendations for mooring equipment and considers mooring loads and operations, motions of the F(P)SO and gas tanker, station keeping, cargo transfer equipment and cargo transfer operations. The guidelines are intended to assist in standardising equipment and procedures for SBS activities and to highlight general design issues in the interest of safe, efficient and reliable operations.

Section 1

Regulatory Compliance

1.1    General
1.2    Coastal State/Local Requirements
1.3    Flag State Requirements
1.4    Classification Society Requirements
1.5    Other Industry Guidance

Section 2
Safety in Design

2.1    General
2.2    Risk Analysis
2.3    Operating Environments
2.4    Model Tests and Simulations
2.5    Tug Support
2.6    Berthing Aids
2.7    F(P)SO Mooring System
2.8    F(P)SO Heading Control
2.9    Mooring Equipment Layout Configuration and Compatibility
2.10  Fendering Equipment
2.11  Cargo Transfer Equipment
2.12  F(P)SO Venting Systems
2.13  ESD Systems
2.14  Emergency Release Couplings
2.15  Quick Release Capability of Moorings
2.16  Lighting
2.17  CCTV

Section 3
Operational and Personnel Safety

3.1    Operational Safety
3.2    Personnel Safety

Section 4
Nomination and Pre-Arrival Procedures

4.1    Nomination Procedures
4.2    Pre-Arrival Communications
4.3    Pre-Arrival Checklists and Testing of Essential Systems
4.4    Tugs and Support Vessels
4.5    Mooring and Fendering Plan

Section 5
Berthing and Mooring

5.1    Personnel and Equipment Transfer
5.2    Pre-Berthing Inspection
5.3    Pre-Berthing Information Exchange
5.4    Pre-Berthing Equipment Checks
5.5    Use of Tugs
5.6    Berthing Criteria
5.7    Manoeuvring
5.8    Mooring
5.9    Transfer of Personnel and Equipment Alongside
5.10  Orientation of F(P)SO for SBS Operations

Section 6
Cargo Transfer

6.1    General
6.2    Cargo and Ballast Plans
6.3    Pre-Transfer System Integrity Checks
6.4    Hose/Arm Handling and Connection
6.5    Sampling and Gauging
6.6    Cargo Transfer
6.7    Control of Vapours
6.8    Hose/Arm Clearing
6.9    Hose/Arm Disconnection and Recovery

Section 7
Unmooring and Departure

7.1    Early Departure Procedure
7.2    Unmooring and Departure

Section 8
Gas-Up and Cool-Down

8.1    General
8.2    Gas Tanker
8.3    F(P)SO

Section 9
Offshore Transfer of LPG via Tandem Mooring or SPM

9.1    Primary References and Scope
9.2    Safety in Design
9.3    Operational Issues

Section 10
Emergency Preparedness

10.1  Overview
10.2  Emergency Scenarios
10.3  Drills and Training


A       Example Content of Terminal Handbook (Port Information Book)
B       Example SIMOPS Matrix
C       Example Gas Tanker Nomination Questionnaire
D       Checklists
D1     Example Record of Pre-Transfer Meeting
D2     Example of F(P)SO Pre-Berthing Checklist
D3     Example of Ship/F(P)SO Safety Checklist
D4     Example Pre-Unberthing Checklist

Purpose and Scope


These Guidelines address the transfer of Liquefied Petroleum Gas (LPG) between Floating (Production) Storage and Offloading facilities (F(P)SOs) and conventional gas tankers. Offshore operations involving the transfer of Liquefied Natural Gas (LNG) are not specifically addressed in this document, but will be included in a future update once industry experience is available on which to base guidance.


The Guidelines are primarily intended to familiarise Masters, ship operators, F(P)SO operators and project development teams with the general principles and equipment involved in LPG offloading activities between F(P)SOs and gas tankers. For the purposes of these Guidelines, the gas tanker is considered to be a vessel equipped with standard mooring and cargo transfer equipment, with a conventional single propulsion system comprising of a fixed blade propeller.


The guide primarily addresses side-by-side (SBS) operations where the gas tanker moors alongside the F(P)SO. LPG is also offloaded to gas tankers offshore in other modes, such as via an SPM or in a tandem configuration. These operations are considered in depth in other OCIMF publications associated with oil transfers. Within this publication, only the differences associated with gas transfer have been highlighted.


To address site-specific aspects in particular locations, the recommendations contained within this publication may be supplemented by additional requirements from development project teams, individual ship owners (or ship managers) and individual F(P)SO operators.


Individual countries may have local regulations that address mooring arrangements and LPG cargo transfer operations within their territorial waters or Exclusive Economic Zone. These must be complied with and, where appropriate, these Guidelines may be referenced for additional advice. These Guidelines should not be considered contrary to, or a replacement of, any National or International Regulations or individual terminal operator’s specific procedures.

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. OCIMF focuses exclusively on preventing harm to people and the environment by promoting best practice in the design, construction and operation of tankers, barges and offshore vessels and their interfaces with terminals. Learn more at

Title: The Safe Transfer of Liquefied Gas in an Offshore Environment (STOLGOE)
Number of Pages: 116
Product Code: WS1253K
ISBN: ISBN 13: 978-1-85609-400-9 (9781856094009), ISBN 10: 1-85609-400-6 (1856094006)
Published Date: October 2010
Binding Format: Hardback
Book Height: 300 mm
Book Width: 215 mm
Book Spine: 10 mm
Weight: 0.80 kg
Author: Oil Companies International Marine Forum

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