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
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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.
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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.
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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
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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.
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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.
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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.
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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.
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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
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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
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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