Tandem Mooring and Offloading Guidelines for Conventional Tankers at F(P)SO Facilities

Published Date

December 2009

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Tandem Mooring and Offloading Guidelines for Conventional Tankers at F(P)SO Facilities

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This book concerns conventional tankers engaged in tandem mooring and is the sister publication to ‘Recommendations for Equipment in the Bow Mooring of Ships at SPMs’. These guidelines address tandem mooring and cargo transfer operations of crude oil and other petroleum products between Floating (Production) Storage and Offloading facilities (F(P)SOs) and Conventional Tankers (CTs).

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These 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 F(P)SO – CT operations. Transfer of crude oil and petroleum products between an F(P)SO and a tandem moored Conventional Tanker (CT) has become commonplace in the shipping industry as Operators increasingly develop offshore fields without recourse to shore based export terminals. Experience gained from existing operations has proven that cargo transfer operations in a tandem mooring configuration may be undertaken safely and reliably. In order 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.

These Guidelines are intended to provide an understanding of the issues - including design, equipment, operations and environmental limitations in operation – contributing to a successful and safe tandem mooring and cargo transfer between an F(P)SO and a CT. Such issues should be taken into consideration by Project teams in the design / construction stage and by Operators at the execution stage, in order to provide an F(P)SO facility that maintains operational risk as low as reasonably practical, utilising risk reduction processes including, but not limited to, HAZOP, HAZID, Quantitative and Qualitative Risk Assessment and Failure Modes and Effect Analysis (FMEA), as appropriate.

This OCIMF document addresses the inter-relation between the F(P)SO and unmodified, Conventional Tankers operating in tandem mooring configuration. The guidance includes recommendations for mooring equipment, considers mooring loads and operations, motions of the F(P)SO and CT, station keeping, cargo transfer equipment and cargo transfer operations. Risk management of F(P)SO operations is addressed in detail within the: • OGP ‘Guideline for Managing Marine Risk Associated with F(P)SOs’ • UKOOA ‘Tandem Loading Guidelines’ • OCIMF ‘Offshore Safety Guidelines with Special Relevance to Harsh Weather Zones’. These documents primarily address dedicated Dynamic Positioning capable shuttle tanker operations. The relevant principles of Risk Management when operating with CTs in a tandem configuration are considered within this document.

Section 1

Glossary of Terms and Abbreviations


Section 2


2.1 Scope

2.2 Purpose

2.3 Objectives

Section 3

Applicable Codes and Standards

3.1 Regulatory Compliance

3.2 Classification Society (CS) Rules

3.3 Statutory Requirements

3.4 Coastal State/Local Requirements

3.5 Process Equipment Industry Standards and Guides


Section 4

FPSO, FSO and Offloading Philosophy

4.1 Definition and Application

4.2 Operating Environments

4.3 F(P)SO Subsea Mooring Arrangements

4.4 F(P)SO Location Relative to Other Structures

4.5 Basis of Design and Offloading Philosophy Development


Section 5

F(P)SO Tandem Mooring Configuration and Equipment

5.1 Introduction

5.2 Mooring Equipment Design

5.3 Single and Dual Hawser Mooring Systems

5.4 Mooring Equipment

5.4.1 Chafe Chain Securing Point

5.4.2 Fairlead

5.4.3 Chafe Chain

5.4.4 Mooring Hawser

5.4.5 Weak Link

5.4.6 Hawser Handling and Storage

5.4.7 Hawser Retirement


Section 6

F(P)SO Cargo Offloading Configuration and Equipment

6.1 Configuration

6.2 Cargo Pumping System

6.3 Custody Transfer System

6.4 Manifold

6.5 Hose Flushing Arrangements

6.6 Cargo Hoses and Equipment

6.6.1 Cargo Hose Stowage in the Sea

6.6.2 Cargo Hose Stowage Reel

6.6.3 Cargo Hose Trough Storage

6.6.4 Cargo Hose Size and Length

6.7 Quick Release Couplings

6.7.1 Passive Couplings

6.7.2 Active Couplings

6.8 Hose End Fittings

6.9 Overpressure and Surge Protection

6.10 Cargo Containment

6.11 Lifting and Other Equipment


Section 7

Conventional Tanker Tandem Mooring and Loading Configuration and Equipment

7.1 Conventional Tankers

7.2 CT Bow Mooring Equipment

7.3 CT Cargo Manifold

7.3.1 Cargo Manifold Configuration

7.3.2 Cargo Hose Lifting Equipment

7.4 Position Keeping Equipment

7.4.1 Position Keeping

7.4.2 Towing Strongpoint and Bollards

7.4.3 Stern Mooring Winch

7.5 Personnel Transfer Facilities

7.6 Lighting

7.7 Surge Prevention and Overpressure Protection

7.8 CT Equipment Maintenance and Repair


Section 8

Mooring Forces and Relative Motions

8.1 Introduction

8.2 CALM Buoy and Conventional Tanker

8.3 F(P)SO and Conventional Tanker

8.4 Simulation, Motions and Forces

8.4.1 Condition of F(P)SO and CT

8.4.2 Hawsers

8.4.3 Tugs

8.4.4 Environmental Conditions



Support Vessels, Manoeuvring and Station Keeping

9.1 Environmental Limitations for Tandem Mooring & Offloading

9.2 Requirements for Tugs and Support Vessels

9.2.1 General

9.2.2 Personnel Transfer

9.2.3 Mooring and Line Handling

9.2.4 Hose Handling

9.2.5 Tug Assistance

9.4 CT Approach to the F(P)SO

9.4.1 Approach to Turret Moored F(P)SO

9.4.2 Approach to Spread Moored F(P)SO

9.5 Approach Speed

9.6 Station Keeping and Limiting Sectors During Offtake

9.6.1 Operating Sectors

9.6.2 Monitoring and Alarm Systems

9.6.3 CT - F(P)SO Separation

9.6.4 Use of Thrusters on F(P)SOs

9.7 Navigational and Berthing Aids

9.7.1 Laser Range Finder

9.7.2 Telemetry and Doppler Systems

9.7.3 Handheld DGPS



Tandem Offloading Operation

10.1 Organisation and Responsibilities

10.1.1 Management of Offloading Operations with CTs

10.1.2 Terminal Operator’s Responsibilities

10.1.3 Mooring Master and Assistant Mooring Master Requirements

10.1.4 Terminal Operations Procedures Manual

10.1.5 Terminal Regulations Manual

10.2 Pre-Arrival Preparations

10.3 Pre-Mooring Preparations

10.4 Mooring Operation

10.5 Pre-Transfer Conference

10.6 Cargo Hose Connection

10.7 Cargo Transfer

10.8 Cargo Handling

10.9 Communication Requirements for Tandem Offloading

10.10 Disconnect and Un-Mooring

10.11 Night Operations

10.12 Manning and Watch Standing Operations



Risk Management

11.1 CT Tandem Offload

11.2 Hazards and Effects Management Process

11.3 CT Tandem Offloading Hazard Identification

11.4 Risk Assessment

11.5 Risk Control

11.6 Mitigated Risk Assessment

11.7 Recovery Measures




Industry Guidelines

IMO Resolutions and Guidelines

Classification Rules

Mooring Systems



Offloading and Maintenance Philosophy

OCIMF was formed in April 1970 in response to the growing public concern about marine pollution, particularly by oil, after the Torrey Canyon incident in 1967. In the early 1970s, a variety of anti-pollution initiatives were starting to emerge nationally, regionally and internationally, but with little coordination. Through OCIMF, the oil industry was able to play a stronger, coordinating role in response to these initiatives, making its professional expertise widely available through cooperation with governments and intergovernmental bodies.

OCIMF was granted consultative status at the IMO in 1971 and continues to present oil industry views at IMO meetings. Since then, its role has broadened to take account the changing maritime activities of its membership. Its remit now covers tankers, barges, offshore support vessels and terminals and its advice extends to issues like shipping in ice and large-scale piracy, which rarely troubled the oil industry when OCIMF was first created in the 1970s.

The current membership of OCIMF comprises 112 companies worldwide.

Today, OCIMF is widely recognised as the voice of the oil industry providing expertise in the safe and environmentally responsible transport and handling of hydrocarbons in ships and terminals and setting standards for continuous improvement. Membership is extensive and includes every oil major in the world along with the majority of National Oil Companies.

OCIMF has much to be proud of. Not only has it contributed to a substantial quantity of regulation at the IMO aimed at improving the safety of tankers and protecting the environment, but it has introduced important new guidance on pressing current issues such as piracy and Arctic shipping. With the process of introducing new Internationally-accepted regulation necessarily slow as it crosses many individual countries and jurisdictions, OCIMF is in the unique position of being able to leverage the expertise of its membership to press ahead with much needed guidance on important industry issues. This provides the means to improve practices in the membership and in the wider industry, and serves as a valuable reference for developing regulation.

Title: Tandem Mooring and Offloading Guidelines for Conventional Tankers at F(P)SO Facilities
Number of Volumes: 1
Edition: First
Number of Pages: 122
Product Code: WS1197K
ISBN: ISBN 13: 978-1-905331-62-8 (9781905331628), ISBN 10: 1-905331-62-2 (1905331622)
Published Date: December 2009
Binding Format: Hardback
Book Height: 330 mm
Book Width: 213 mm
Book Spine: 10 mm
Weight: 0.73 kg

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