Towing (Oilfield Seamanship Series Volume 4)

This volume of the Oilfield Seamanship Series focuses on towing operations. It includes practical advice on subjects such as changing tow bridles and the general arrangement of jackup vessels. The text is supported by diagrams and tables, both of which cover manoeuvring considerations such as turning into heavy weather. The limitations of AHTs and AHTSs are explained in the context of personnel experience, with procedural guidance given to prevent damage to towing equipment.

Part 1 Introduction

Part 2 Towing Arrangements

2.1 Heavy duty semi-submersible drilling unit/support barge

2.2 Lay barges

2.3 Large cargo barges

2.4 Medium and large size jackup units

2.5 Multi-tug towing

2.6 Retrieval gear and common defects – cargo barges, semi-subs and jackups

2.7 Short scope towing practice

Part 3 Rigging and Connecting Tow Gear

3.1 Tow gear rig-up – large AHTS for interfield tow

3.2 Rigging towing gear rig up on an AHT for interfield tow

3.3 Towing gear rig up for jackup manoeuvring

3.4 Tow gear for manoeuvring a cargo barge

3.5 Towline control – the gog line

3.6 Towing rig for towing on anchor chains

3.7 Changing tow bridles

3.8 Towing on rig pennants

3.9 Towing scopes

3.10 Chafing gear – towline protection

3.11 Chafing gear – operational cautions towing shoes and sleeves

3.12 Passing tow bridles

3.13 Picking up tow bridles

3.14 Connecting tow gear

3.15 Disconnecting/retrieval of tow gear
Part 4 Emergency Towing Arrangements and Towing Emergencies

4.1 Passing tow gear in heavy weather

4.2 Picking up and connecting emergency tow gear

4.3 Broken – causes

4.4 Data on towline breakages

4.5 Recovery of tow bridle on a semi-submersible drilling rig

4.6 Fishing and re-connecting broken tow gear

4.7 Re-rigging tow gear on tug – changing wires

4.8 Emergency eye splices

4.9 Re-socketing

4.10 Tug breakdown – single and multi-spread tows

4.11 Girting problems

4.12 Ripping down rails and drums

4.13 Fouled propellers

4.14 Man overboard

Part 5 Tug and Tow Management

5.1 Getting underway – moored semi-submersible

5.2 Getting underway – jackup

5.3 Getting underway – flat barge

5.4 Towline forces and towline deployment

5.5 Holding course and altering course

5.6 Allowing for set and drift – choosing the best course

5.7 Using wind, tide and current

5.8 Catenary calculations and tables

5.9 Daily towing checklist

5.10 Speed while towing

5.11 Limitations of AHTs/AHTSs as towing vessels

5.12 Fuelling at sea

5.13 Tug/tow interface

5.14 Towing jackup rigs

5.15 Voyage plan – basic data

5.16 Contingency planning

5.17 Towing Techniques

5.18 Standing orders for towage operations

Part 6 Heavy Weather Towing and Tow Management

6.1 Introduction

6.2 Semi-submersibles

6.3 Jackup vessels

6.4 Flat barges

6.5 Running before heavy weather

6.6 Heaving to – into the weather

6.7 Heaving to – before the weather

6.8 Turning up into heavy weather

6.9 Scope and power settings in heavy weather

6.10 Self-rendering winches

6.11 Rolling

6.12 Shearing and steering

6.13 Shearing forces management

6.14 Gog lines and their use

6.15 Lee shore problems

6.16 Weather routeing

Part 7 Towing Gear

7.1 Towing gear strength and towing forces

7.2 Sizing tow gear to the boat

7.3 Tow wire type, size and construction

7.4 Tow wires

7.5 Tow wire bending factors

7.6 Bollard pull/speed

7.7 Bollard pull and power settings

7.8 Tow gear safety factors

7.9 Termination efficiency

7.10 Recommended wire ropes for towing

7.11 Synthetic ropes for towing springs

7.12 Thimbles, chafing gear and stoppers

7.13 Shackles, connectors, fish plates and chain fittings

7.14 Maintenance and inspection of towing gear – wires, synthetic ropes and connectors

7.15 Splicing, socketing and the use of cutting gear

7.16 Spooling wires and pennants

7.17 Towing operations

7.18 Jury rigged tow gear

7.19 Towing winches

7.20 Towing practice

7.21 Useful tables and wire rope data

Part 8 Planning Towing Operations

8.1 The role of the warranty surveyor – tug approval

8.2 Checklist for tug approval

8.3 Surveyors’ inspection of towing vessel

8.4 Bollard pull certification and trials

8.5 Towing power calculations

8.6 Tow planning checklist

8.7 Tow Master’s duties and responsibilities

8.8 Towing resistance calculations

8.9 Typical speed and power used and tensions

Part 9 Towing Safety

Part 10 Unusual Towing Operations

10.1 Submerged pipeline bridle towing

10.2 Trenching and ploughing

10.3 Heavy lift support

10.4 Loading submersible barges

10.5 Iceberg towing

10.6 Tow management of very large structures

10.7 Multi-unit tows
10.8 Workboats

Part 11 Jackup Towing Operations

11.1 General use of harbour tugs for positioning

11.2 General use of tugs

11.3 Tug management – manoeuvring jackup units

11.4 Gear make-up and strength calculations

11.5 Making fast main tow gear

11.6 Towing positions

11.7 Picking up and connecting towlines

11.8 Leaving open location – 2 boats

11.9 Moving onto open location – 2 boats

11.10 Moving onto locations – 2 boats and stern bridle

11.11 Moving onto open location – 3 boats

11.12 Positioning alongside platforms and jackets

11.13 Locating on a jacket with subsurface obstructions

11.14 Rigging surface support buoy

11.15 Walking onto a platform

11.16 Moving onto jackets – alternative methods of control

Captain Michael Hancox

Captain Michael Hancox is a Marine Consultant and former Director of Hancox Marine Services Limited.

Witherby Publishing Group

Witherbys titles are developed using scripts developed by technical experts that are peer reviewed within work groups. Typically, they seek to improve understanding of the regulations, recommendations and guidelines issued by Industry.

Witherbys staff have significant expertise in the fields of navigation and hazardous cargoes as well as in the presentation of complex subjects in a graphic and easy to understand manner.