Encyclopedia of Ocean Engineering

Living Edition
| Editors: Weicheng Cui, Shixiao Fu, Zhiqiang Hu

Complete and Partial Dismantling

  • Qingji ZhouEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-981-10-6963-5_170-1
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Synonyms

Definition

Nowadays, there are different ways of dismantling ships and offshore structures, i.e., complete dismantling and partial dismantling. For ship recycling, most the end-of-life vessels are usually sold to the international markets for complete dismantling. It is a common way to export obsolete vessels to shipyards for recycling in both developed and developing countries as a way of resource recycling and reusing. However, some vessels, such as cargo ships and tankers, are partially dismantled and transformed into fishing farming, which would be beneficial to the environment. For offshore structure recycling, when an offshore field becomes unviable, the offshore infrastructures require decommissioning, by using one of the following alternatives – complete removal, partial removal, or remote reefing (Chandler et al. 2017).

Scientific Fundamentals

Historical Development

Currently, the core ship dismantling locations have been moved to developing countries, including India, Bangladesh, Turkey, Pakistan, and China (Mikelis 2008; Deshpande et al. 2012; Ormond 2012; Hiremath et al. 2015; Rahman and Mayer 2015; Du et al. 2017, 2018). However, the ship dismantling industry usually has severe negative implications on the environment, human safety, and health because of the hazardous materials and chemicals involved (Sonak et al. 2008; Neşer et al. 2008; Harris and Kahwa 2003). Recycling end-of-life vessels in an environmentally friendly manner is a major challenge faced by ship owners, shipbreaking yards, as well as government agencies worldwide (Du et al. 2018). Moreover, problems generated by the insufficiencies of current ship dismantling practices have consequences for not only the environment but also for occupational safety and the health of the workers.

Meanwhile, there are thousands of offshore oil and gas facilities and platforms all over the world, as well as subsea infrastructure, pipelines, wells, etc. Many of those offshore engineering infrastructure have been in service for several decades and are due or will soon be due to be decommissioned (Chandler et al. 2017). Typically, offshore structure decommissioning procedure includes the following steps – decommissioning planning and engineering, permitting and regulatory compliance, platform preparation, well plugging and abandonment, conductor removal, mobilization and demobilization of derrick barges, platform removal, pipeline and power cable decommissioning, materials disposal, site clearance and verification, and post-job activities. Herein, this part aims to introduce complete and partial dismantling of ships and offshore structures that are end-of-life.

Complete Dismantling of Ships

The Sixth Meeting of the Conference of Parties to the Basel Convention in 2003 had adopted the Technical Guidelines for the Environmentally Sound Management of the Full and Partial Dismantling of Ships (hereafter as The Guidelines) as the technical guidelines for the hazardous wastes and their disposal during ship dismantling. The Guidelines had also been considered and adopted by IMO for IMO Guidelines on Ship Recycling in 2004. Meanwhile, the Hong Kong International Convention for the Safe and Environmentally Sound Recycling of Ships, 2009 (the Hong Kong Convention), also aims at ensuring the environment, safety, and health issues. These guidelines aim to enable ship dismantling facilities attain environmental sound management (ESM) by providing information and recommendations on procedures, processes, and practices for the countries during ship dismantling processes. Therefore, it is a major challenge to recycle end-of-life ships in both environmentally sound and safe manner ways.

As mentioned by the Basel Convention, ESM is defined as “taking all practicable steps to ensure that hazardous wastes or other wastes are managed in a manner which will protect human health and the environment against the adverse effects which may result from such wastes.” The Guidelines provide an overview of the elements to be considered for the complete dismantling of ships in order to achieve an environmentally sound ship dismantling, including preparations on the ship, ship dismantling facility, environmental management plan, etc. In this section, the procedures for different methods of ship dismantling are introduced and studied. The procedures include pre-demolition removal and preparations prior to ship dismantling operations, arrangement of ship dismantling facility, main works of ship dismantling operations, and the environmental management plan.

Environmental Management Plan

At the beginning of ship dismantling, an environmental management plan (EMP) is usually required to achieve the aim of environmental sound management for ship dismantling. The EMP includes the assessment of the potential environmental impacts during ship dismantling by conducting an environmental impact assessment, which helps to identify the environmental aspects and the environmental goals to be set for the facilities. The EMP, which is an all-encompassing document, covers all aspects of environmental issues at a macroscopic range, including the assessment of potential environmental impacts, the potential preventative measures, and environmental management system (hazardous materials management plan, contingency preparedness plan, monitoring plan, etc.).

Pre-demolition Removing and Preparations

Prior to ship dismantling operations, firstly, whatever method the yard uses to dismantle the ship, the ship should be fixed or moored well to minimize displacement of the ship. Thereafter, some preparatory procedures should be implemented on the ship, such as overall checking onboard, collecting related information, and planning of ship dismantling; deployment of access gangway and warning signs; open and free any gas; oxygen and explosion tests in sealed cabin; deployment of oil booms; emergency facilities equipment; etc. More details are shown in Table 1.
Table 1

Preparatory procedures before main work of ship dismantling

Item

Action

Purpose

Prepare inventory list of hazardous materials and polluting wastes

Make a detailed ship dismantling plan

Identify, quantify, and locate different types of hazardous materials and wastes on board

To arrange the sequence and nature of the work to be executed and ensure human health and safety and ESM

Remove and clean the liquids, e.g., fuels, oils, etc.

Remove the hazardous materials, e.g., asbestos, Polychlorinated biphenyl (PCBs), tributyltin (TBT) paints, etc.

Clear all the residual materials before cutting process

Remove crew’s furniture, storage, tools, and other sundries

Pump out and drain off the oil in oil pipes, oil tanks, and lubricant systems, and clean the tanks

Remove harmful and harmless insulation materials

Remove other dangerous (toxic, flammable, and explosive) items such as dump oil, paints, high-pressure cylinder, etc.

To ensure that the ship is ready for dismantling in safe and clean conditions

Removal of equipment

Remove consumable and loose equipment

Remove reusable components

To ensure that the cutting operations are more efficient

Securing

Deploy safe access to all areas, compartments, tanks, etc. ensuring breathable atmospheres

Create safe working conditions for hot work, including cleaning/venting, removal of toxic or highly flammable paints from areas to be cut, and testing/monitoring before any hot work is performed

Deploy emergency facilities equipment

To ensure that working procedures and operations are undertaken in a safe manner

Note: Adapted from the Basel Convention (2003)

Ship Dismantling Facility Arrangement

It is very important to make sure that all of the dismantling facilities and equipment should be working properly and the dismantling yard should be cleaned and comprises certain key functionalities. The equipment includes different kinds of cranes, forklift trucks, loaders, transport vehicles, cutting equipment, etc. Whichever method used for dismantling, the shipbreaking yard should include various zones for different purposes during dismantling. For an environmentally sound design of a yard, it is important to discern what activities take place in which zone, and what associated hazards are to be considered and prevented through environmentally friendly design. The zones shall comprise certain key functionalities, including containment for spills and leakages of hazardous materials/liquids, certain areas for dismantling blocks and sections into small pieces, specially equipped warehouse and appropriate containment for hazardous and toxic materials removal (such as asbestos), temporary regions for benign materials and hull blocks/sections, secure storage rooms/areas for hazardous wastes, certain regions for fully processed materials and equipment that can be reused and recycled, and proper disposal facilities for persistent organic pollutants.

Main Works of Ship Hull Dismantling

The main work of ship hull dismantling follows the pre-demolition removal and cleaning, and the layout of dismantling zones and facilities/equipment. Various techniques applied for ship dismantling have different costs and different degrees of environmental and social impacts. Currently, there are mainly four methods for ship dismantling. These include beaching, slipway or landing, alongside or pier breaking, and dry dock, as shown in Table 2.
Table 2

Comparison of different ship dismantling methods

Ship dismantling method

Procedures

Advantages/disadvantages

Key locations

Beaching

The ship is driven to a tidal flat on a high magnitude tide and then pulled up the beach as far as possible

The items and steel are removed from the ships by gas or oxygen cutting

All operations take place directly on the beach in a relatively small and congested area

The winches drag the steel pieces up the beach

Large blocks may also be cut from the ship, released onto the mudflats, and dragged individually by the winches

Once onshore, everything is cut into smaller pieces progressively and then taken from the yard by lorry or truck

Does not require investments in infrastructure or technology

The moving cranes and motorized winches can be reused

Labor-intensive

Unsuitable for the use of heavy lifting gear

Not allow for containment of hazardous substances

Any spills of oil or cargo remaining would be swept out to sea and cause environmental issue

The regions with high tidal variation and wide mudflats

Chittagong in Bangladesh

Alang in India

Gadani in Pakistan

Slipway or landing

A modification of beaching method essentially, with some crucial differences

The ship is driven onto the shore or on a concrete slipway connecting shore and sea

Ship sections are removed by a mobile crane working from the shore, and the ship is pulled onto the shore gradually

Steel pieces are also removed from the ship by the mobile crane

After the ship is lightened, it will be dragged up the shore for further dismantling

A temporary quay or semipermanent jetty may also be added

Comparing to beaching method, this method is comparatively safe and environmentally friendly

Any accidental spillages can be contained due to the lack of racing tides

Typically used in areas where the tidal flow is low and easily predictable

Aliaga

Turkey

Some other EU Countries

Alongside or pier breaking

The ship is immobilized on a wharf or quay in a sheltered harbor or river

The ship is secured alongside in the sheltered waters

The superstructure is dismantled from top to bottom and from outside to inside

The cutting usually follows the welding lines

Usually uses cold dismantling method for oil pipes

It is mandatory to drain the remaining oil, gas, and water inside the equipment and conduct gas-free check before cutting during engine room dismantling

Dismantle the connection pipe and parts with the equipment at first

Maintain the ship’s balance at all times

A crane removes the hull from the top to the bottom

The last piece (such as the double bottom) may be lifted or sent to a dry dock for final cuttings

Results in pollution on alongside, which can be monitored and controlled

It is a safety and environmental sound way

Usually applied in calm water

China

Myanmar

Few places in Europe

Dry dock

The ship is driven to an enclosed, flooded dock, and the water is pumped out

The ship is then dismantled piece by piece

On completion, the dock is cleaned and flooded again for the next ship

With a minimum risk of environmental pollution

The cost is the highest

Rarely used presently due to its high cost

The USA and Europe practice this method

Leave Sley International’s facility in Liverpool, UK

Note: Adapted from Hossain (2017), Demaria (2010), and Du et al. (2018)

During the first dismantling, the ship is usually broken down into blocks or sections. Piece cutting is needed to cut the blocks into pieces on site for secondary dismantling, especially for alongside or pier breaking method. The workers should clean up the residual oil and wastes on the blocks so that they can be disposed of separately. As a requirement, the blocks are cut into steel sheets, profiled materials, and waste steel and, respectively, placed in a certain place (Du et al. 2018). A procedure for dismantling a LNG (liquefied natural gas) vessel, which applies pier breaking method, can be seen in Fig. 1.
Fig. 1

Ship recycling procedure for LNG (Du et al. 2018)

Complete Dismantling of Offshore Platforms

Offshore oil and gas platforms are aging gradually around the world. Those end-of-life offshore structures are decommissioned and removed by ways of complete dismantling and partial dismantling. For complete dismantling of offshore platform, the removal procedures include platform preparation and cleaning, conductor removal, removal of deck and equipment, complete removal of jacket or hull, site clearance, etc.

Platform Preparation

For platform preparation and cleaning, the main procedures are as follows.
  • Prepare the facilities for removal.

  • Shut down the facilities and equipment.

  • Topside inspections.

  • Underwater inspections, conducted by divers and remotely operated vehicles (ROVs).

  • Plug and abandon the wells permanently, and abandon the pipelines.

When removing the topside of the platform, the following steps shall be carried out.
  • Flush and clean the tanks, process equipment and pipes, and dispose of the residual hydrocarbons on the platform.

  • Remove the equipment.

  • Cut the pipes and cables.

  • Divide the platform modules into individual units.

  • Weld padeyes and remove obstructions for deck module lifting.

  • Reinforce local structure for lifting.

  • When removing the jacket, marine growth can be removed from the structure at sea if possible.

Conductor Removal

The conductors can be removed during platform decommissioning operations or prior to the arrival of heavy-lift vehicle. The conductors can be severed by using one of the following alternatives: explosive, abrasive cutting, mechanical cutting, and diamond wire cutting. When pulling the conductors, the following methods can be used: casing jack, drilling rig, platform crane, and the crane on heavy-lift vehicles.

Deck and Module Removal

The removal of topsides is in reverse sequence of the installation procedures. The modules shall be removed and placed on a cargo barge, which is fixed on the cargo barge by welding. The deck and module removal can also carried by floatover method, which requires a specially designed vessel that can be partially submerged by ballasting and raised by deballasting. The cargo barge is then sent to the onshore disposal yard.

Complete Removal of Jacket and Hull

Complete removal of jacket can be conducted by separating the structure from its foundation and transporting it in whole or in pieces to onshore yard for further dismantling. Explosive method is usually to separate the structure from its foundation. Prior to the explosive detonation, certain surveys need to be carried out to ensure that the marine mammals are not near the platform. Usually, explosives are placed in the main piles and skirt piles at least 15 ft below the mudline. If the lifting capacity of the heavy-lift vehicle is insufficient, buoyant can be added to the served jacket to reduce the weight. Large jacket can be towed to shallower water at first, then cut to sections, and sent to the onshore disposal yard.

After the complete removal of the platform, both the site and any location where the jacket is cut have to be cleared of debris and verified that they have been cleared. The site can be cleared by trawlers dragging nets across the bottom in a recorded grid pattern of specified dimensions or by the use of other authorized methods.

Partial Dismantling of Offshore Platforms

When offshore platforms require decommissioning, there are usually different ways, including complete removal, in situ decommissioning (leaving the infrastructure in place either completely intact or with the topsides removed and legs toppled), removal and relocation offshore platforms (for example, as a dive site or fishery), as well as partial removal (removing some parts of the infrastructure while leaving others in situ) (Ekins et al. 2005; Chandler et al. 2017). Partial dismantling usually happens in the decommissioning of offshore platforms. Platform jackets or hulls may be decommissioned using one of the following alternatives – complete removal, partial removal, or remote reefing. These alternatives vary only in the methods used to remove the jacket or hull. For any given platform type, the platform removal preparation, well P&A, and pipeline decommissioning are the same for all removal alternatives.

The advantages and disadvantages for dealing with offshore platforms in different ways, i.e., leave in place, partial removal, and complete removal, are shown in Table 3.
Table 3

Advantages and disadvantages for different methods of platform removal

Option

Advantages

Disadvantages

Leave in place

Poses no harm to marine life

Immediate cost savings

Provides recreational fishing, diving habitat

Provides emergency safe havens

Maintains status

 Structure remains visible

 Requires no research and development

 Requires no site clearance

 Provides migratory animal habitat (surface)

 Provides reef habitat (subsurface)

Suitable for structures at water depth more than 400 feet

Maintains unnatural habitat

Maintenance costs escalate with age

 Requires protective coating above water

 Requires cathodic protection under water

 Requires navigation-aid lights and horns

 Remains susceptible to storm damage

Continues conflicts with other users

Potential liabilities

 Unauthorized boarding

 Collisions

 Surface and subsurface navigation hazards

May require eventual removal with

 Reduced structural integrity

 Increased safety risk

 Increased cost

Negatively affects construction/removal industry

 No recycling of steel

Requires changes in regulations and laws

Not suitable for structures at water depth less than 400 feet

Partial removal

Potentially reduces harm to marine life during removal and maintains some reef habitat

Potentially cost effective

 Requires no maintenance

 Requires no site clearance

May provide recreational fishing and diving habitat

Operators released from liability

Encourages innovative removal methods

Does not return habitat to natural state

Eliminates habitat structure in upper range of water column

Must maintain buoys

Useful only in water depths allowing sufficient clearance

Potentially increases diver risk during removal

Decreases shrimping access

Liability attaches to regulatory agency

 Court test inevitable

 Creates navigational hazards (surface and subsurface)

Loss of resources

 Eliminates surface habitat

 No recycling of steel

Complete removal

(at 15 feet below mudline)

Meets shrimper requirements

 Maintains clearance for trawlers

Requires no changes in regulations or laws

Poses no navigational hazards

Eliminates liability and site maintenance

Allows reuse and recycling

Environmental impacts

 Relocates or eliminates reef habitat

 Fish kill from explosives

Expensive to operators

 Explosives require an observer program

 Restricts use of explosives

 Discourages development of nonexplosive techniques

 Requires transportation to shore or reef site

Requires site clearance

May require backfill

Hazardous to divers

Potential removal problems from soil skin friction at 15 feet below mudline

Complete removal

(at 5 feet below mudline or less)

Immediate cost savings

 Requires less jetting

 Minimizes problems from soil skin friction

Encourages use of nonexplosive methods

 Less hazardous to divers

 Easier to clean for access by mechanical or abrasive tools

Meets shrimpers requirements

 Nothing remains above mud line

Reuse or recycling possible

Poses no navigational hazards

Requires no backfill

Eliminates liability and site maintenance

Requires changes in regulations and laws

Explosives may still be necessary in some cases although advanced techniques using smaller charges could be used

Site clearance required

Environmental impact

 Relocates or eliminates reef habitat

 Requires disposal

Closing Remarks

Different from partial dismantling of offshore platforms (such as offshore jacket platform), generally, the ships are completely dismantled in different ways after a life span of around 30 years. Specifically, the environmental management plan for ship dismantling, pre-demolition removing and preparations before ship dismantling operations, ship dismantling facility arrangement, and the dismantling procedures for different methods of ship recycling have been introduced in this paper. The end-of-life ships usually contain many kinds of hazardous materials which may result in health, safety, and environmental issues if they are not disposed properly. Therefore, an environmental management plan is needed; advanced techniques remain to be developed to enhance the prevention and protection of the environment, human health, and safety. The steps for the complete dismantling of offshore platforms have also been discussed. “Design for recycling” concepts are meaningful ways of improving the health, safety, and environmental conditions during ship dismantling.

Cross-References

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Copyright information

© Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  1. 1.School of Civil and Environmental EngineeringNanyang Technological UniversitySingaporeSingapore

Section editors and affiliations

  • Zunfeng Du
    • 1
  1. 1.Department of Naval Architecture and Ocean Engineering, School of Civil EngineeringTianjin UniversityTianjinChina