14. Surface Preparation

8/3/2019 14. Surface Preparation

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SURFACE PREPARATION

FOR SHIP HULL

Prof Ir Dr. Ab Saman b. Abd Kader, PEng,MIEM, MCIT

Faculty of Mechanical Engineering, UTM



Description

During this process, surfaces of steel ships areprepared for painting.

Steam or fresh water under high pressure is played

onto the undersides of hulls to remove barnacles andother growth.

Exterior surfaces may be sandblasted, but chipping,

using chipping hammers, wire brushes and grinders,powered either pneumatically or electrically, is morecommon.



Interior preparation is usually done by hand, althoughspecial equipment may be used in tanks and in void

or double bottoms.

- Chemical paint and rust removers may be usedin preparing metal surfaces.

- A commercial diving operation may be usedto clean the undersides of hulls while the ship

remains in the water. For example, divers maymanually steer a hull cleaning device called a

SCAMP, which is comprised of rotating steelbrushes and an impeller to vacuum the materialremoved from the hull.



Equipment

Scaffolding and ladders

Abrasive blasting equipment - rubber hose lines, compressors,nozzles, couplings, etc.

Electrical or pneumatic hand tools

Tackle

Flame torches

Personal protective clothing - hats or hoods, dust masks, goggles,face shields, respirators, gloves

SCAMP - an underwater hull cleaning device operated by divers



Procedure

In order to maintain conditions Munters normallyinstall their own desiccant dehumidifiers.

Based on Munters’ sorption drying wheel, the process

ensures that when the air leaves the dehumidificationunits and enters the enclosures it is completely dry.

These units also draw in heated reactivation air,collecting moisture via the drying wheel and thenexiting the units and the enclosure as wet air.



Equipment is normally positioned outside the

temporary structure with the dry air ducted and

blown in, ensuring that as air is circulated,

moisture is picked up and removed creating a

closed circuit and ensuring constant air

movement.

Providing a total loss system enables Munters

to effectively pressurise the area and reduce

moisture infiltration.



Benefit

Using such methods Munters were able to

provide:

Uninterrupted work – Continuous operation

of Munters’ dehumidifier units enables the

programme of works to be completed without

interruption, ensuring all deadlines are met.



Controlled resurfacing conditions –

- Regular checks are undertaken during the entire

resurfacing process to ensure RH is constantlymaintained irrespective of weather conditions.

- This constant level of humidity improves the overallcuring process and avoids corrosion and

condensation.

Reduced energy costs –

- In addition to being more effective, Munters’

dehumidifiers are considerably more efficient thanheaters at controlling humidity, consequently costingless and providing a more environmentally friendlyoption.



Characteristics

An inert topcoat designed for full immersion service toovercoat virtually any surface and make it highly resistant tomoisture and oxygen permeation, corrosion and chemicalattack and abrasion

coatings exhibit outstanding weathering characteristics in bothsalt and fresh water environments

ideal for full immersion service on all marine equipment,

pipeline systems, water tank linings, or any immersed or semi-immersed components



Designed to protect ferrous and non-ferrous metals, fiberglass, carbon fiber andconcrete, it provides a high quality finish, offers exceptional all roundperformance and is an impenetrable barrier to marine boring organisms.

An impenetrable barrier to marine boring organisms (readily cleaned of marinegrowth)

Outstanding Hydrophobic and Oleophobic surface properties

Impervious to moisture and oxygen permeation (Osmotic barrier)

Highly flexible and outstanding impact and abrasion resistance

Extremely low surface energy reduces friction and drag

Highly resistant to attack by hydrocarbons and chemical products

Water potable and completely non-toxic to marine environments



Repair Activities

Underwater Hull Cleaning is accomplishedperiodically to:

• Improve fuel economy through reduction of hullfriction resistance by removing marine fouling

• Restore acoustical capability of sonar devices

• Prepare damaged or abraded surfaces for applicationof underwater curing compounds

Documents

14. Surface Preparation