CÔNG NGHỆ sơn tàu THỦY

Sơn là chất lỏng có chứa bột màu, khi sơn trên bề mặt sẽtạo một màng bám dính lên bề mặt có tác dụng bảo vệ rỉ,trang trí và có tính chất đặc biệt khác.• Binders Chất Kết Dính• Solvents Dung Môi• Pigments Bột Màu• Extenders Chất Độn• Additives Chất Phụ Gia

Trang 1

Frosio 07 Ambient conditions slide # 1

AMBIENT CONDITIONS

Humidity Air Temperature Substrate Temperature

Parameters influencing the corrosion speed

Atmospheric corrosion

Humidity Temperature

Concentration of salts Amount of air pollution, including acid rain, soot and dust particles

Trang 2

3 °C above the dew point

of the surrounding atmosphere

Atmospheric conditions.

Requirement during blasting and painting

Trang 3

B-24/2-4

4847-693

Estimating probability of condensation

• Cold liquid inside hull and warm air outside causes condensation

• See how frames inside keeps the cold longer

Why Temperature & Humidity are important

Frozen overnight condensation, follows the frames of the ship

Condensation follows the contours

of the double-bottom tank

Trang 4

Purpose of climatic evaluation

Evaluate the likelihood of the moisture in the air to form condensation on a substrate

Moisture / Absolute Humidity

• When water evaporates, it forms water vapour or moisture in the air

• We may measure this moisture as gram water per

• The maximum amount of moisture that can be contained in the air depends on the temperature of the air

• Warm air can contain larger amounts of moisture than cold air

• The maximum moisture that can be contained in air

at the various temperatures is called the Absolute

Humidity

Trang 5

maximum moisture content in the air is

Trang 6

Moisture / Relative Humidity

• The Relative Humidity is a measure of how much of the

Absolute Humidity (maximum moisture) that the air contains, expressed as percent

• If the air contains the maximum amount of moisture, it will have a Relative Humidity of 100%

• If the air contain half of the maximum amount of moisture, it will have a Relative Humidity (RH) of 50%

• If the air contain a quarter of the maximum amount of moisture, it will have a Relative Humidity of 25%

Trang 7

% R.H.:

Water vapour in the air as percentage of the total amount water vapour the air can contain at the same temperature

Example

Air at 20oC can contain 17.31 g water/m3, but the actual content is measured to 15 g/m3 What is the R.H ?

15g x 100%

17.31g

Humidity / Dew Point

as percentage of Absolute Humidity 17.31)

g/m3, but the RH will increase to 92.69% (12.64 as percentage of Absolute Humidity 13.65)

Humidity) is 10.62 g/m3 This means the moisture content

of 12.64 g/m3 is 2.02 g/m3 more than it can hold at this temperature

• The consequence is that the excessive moisture will leave the air through condensation, ending up as dew on available surfaces or as rain or fog

• The temperature at which a given moisture content will

start to condensate is called Dew Point.

Trang 8

Dew Point / Substrate Temperature

• On an early morning inspection we measure the air

• Due to cold over-night temperature, the steel temperature

• Would this cause any problem?

to the steel surface will be cooled by the steel and perhaps

• This means that although we may not see it clearly, there will be condensation on the steel

Dew Point!

Trang 9

Temperature of substrate should

be at a temperature of

min 3oC

above dew point of the air in the

vicinity

and paint application:

Measuring ambient conditions

• Electronic multi-function gauge

• Electronic humidity gauge

• Sling Psychrometer (Sling Hygrometer, “Dry and Wet bulb”)

• (Hair hygrometer, not suitable!)

• Dew point calculator

• Steel thermometer

Trang 10

• Needs frequent calibration

• Dependent on batteries

• Multi-function models will measure air temperature, surface temperature, relative humidity, and calculate dew point and T(*)

( * ) difference between dew point and surface temperature)

Electronic humidity gauge

A dry and a wet thermometer put together in

one unit.

• The difference in the measured temperatures indicate the amount of humidity:

• Large difference = low RH%

• Small or none = high RH%

Sling Psycrometer

Trang 11

ISO 8502-4 Measuring the relative humidity

• Photo: Sling Psychrometer for measuring:

- Dry temperature

- Wet temperature

• Measure the temperature in the vicinity

• Calculate the relative humidity

• Use together with dew point calculator

Cd-4932-88

ISO 8502-4 Dew point calculator

• For calculation of dew point

• To be used together with surface temperature thermometer and sling psychrometer

• Use this frequently during pre-treatment, application and drying of the paint

• Recommendation: Every 6 hours and when weather conditions are changing

Cd-4932-89

Trang 12

Guidance on the estimation of the probability

of condensation prior to paint application

Steel temperature min 3 oC above the dew point

Trang 13

determination of relative humidity (%RH)

Example:

Measured valuesAir dry temp.: 14.0 °CWet bulb temp.: 10.5 °CRead

Relative humidity: 65 %Dew point: 7 °CAir-water content: 6.3 g/kg

Trang 14

Using the IX diagram

• Draw a horizontal line at the appropriate dry bulb temperature

• Draw a 45o line at the appropriate wet bulb temperature

• At the intersection you will determine the RH

• Draw a vertical line from the intersection point all the way to the 100% line

• This is the dew point

Ambient conditions, general

Painting should not be started when:

• The relative humidity exceeds 85% (unless the paint manufacturer consider it safe)

• The substrate temperature is less than 3o

C above the dew point

Trang 15

• Dehumidifier, reduces the actual humidity

in the surroundings

• Heather, heat the objects (surfaces) prior

to application in order to reduce the danger for condensation.

• Forced ventilation is a must in order to secure a proper evaporation of the solvents from the paint film.

• Ambient

temperature will influence:

– shelf life (storage) – potlife (two-pack paints: time between mixing and no longer useable)

– induction time reaction before application) – viscosity/sprayability – Steel Temperature

(pre-Ambient Temperature and Steel Temperature

• Steel temperature

will affect:

– probability for condensation – solvent evaporation – speed of cure (drying time)

– degree of cure – recoating interval – service life of the coating

Trang 16

Ventilation Good practice

Solvent vapours are heavier than air

Suction from lowest points

in enclosed areas

Ventilation Bad practice

Solvent vapour Solvent vapour

Using an inlet fan Using an exhaust fan

Air out

Solvent vapours

Inlet fan, air through pipe

Trang 17

Control of relative humidity and temperature

• Check the atmospheric conditions before the work starts

• If required: Install proper ventilation

• Check the atmospheric conditions while the work is ongoing and during drying / curing

Paint technology: Humidity_control1

Temperature and humidity

of air used for drying.

• Supply of heated air immediately after application may lead to skin drying and entrapped solvents

• Cold air will keep the film open longer and ensure proper evaporation

• Avoid high air temperature (especially epoxy)

• High humidity will slow down the drying time

• Exhaust from heating equipment using propane or paraffin oil contain water and Carbon dioxide and may create Amine sweating

Trang 18

Blisters inside a tank due to poor ventilation

Entrapped solvents

• Blisters sometime contain water

• Rust will not be formed inside intact blisters, due

to the high pH

• As soon as the blisters break corrosion will start

• Use cathodic protection

to back up the paint system

Cd-4934-68

Trang 19

Frosio 12 Special coatings slide # 1

SPECIAL COATINGS

Other coatings than paint

Powder coatings

Trang 20

• The powder contains resin, curing agent, pigments, additives, etc., all in solid form

• Surface preparation:

Sa 2½

• Applied by electrostatic spray

or dipping in a fluidized bed

• The object is baked in an oven at 160 –

250o C for 5 – 20 minutes

• The powder melts, forms a film and cures

• Typically used as part of production line (conveyor belt), for pipes (fusion bonded epoxy), cladding sheet, or for reinforcing bars in concrete

Powder coating (2)

Trang 21

Glass fibre lining

• Types of glass:

– Woven mats– Non-woven mats– Chop-strand– Flakes

• Can be combined with both epoxy, polyester and vinyl-ester resins

• Used inside tanks, usually at the bottom / lower sides

• High requirement to surface preparation

• Resin is usually applied directly on the prepared steel surface, the glass fibre mat is pressed into the wet film and more resin applied on top

• Chop-strand application may also be used

• System may be built up be several coats

• High labour cost

• High material cost

Glass fibre lining (2)

Trang 22

Rubber lining

• Used for tanks and pipelines

• Considered as the ultimate acid protection

• Natural rubber lining is typically used in storage tanks for concentrated

• Requires curing

in autoclave at

110 – 180o C:

Vulcanization

Trang 23

Anti-corrosion tapes & foils

• Mostly used on pipes

• No solvents

• Require special application equipment

• Limited size of items to

be coated

• Applied by wrapping over a primer

• Thickness from 1 mm upwards

• No curing

• Many varieties available:

– Polyethylene tapes – Petrolatum (greasy) tapes – Elastomerised Bitumen tapes – PE-Butyl Rubber tapes – High temperature tapes

Trang 24

Soft coatings

• Coatings that do not dry or cure, but stay soft all the time

• Protect against corrosion by forming a barrier

• Usually very good penetrating properties

• Applied by spraying

• Very difficult to change to a drying type of coating (cleaning / adhesion)

• Wax (warm applied)

• Grease (Lanolin / Wool fat / Sheep grease), very messy!

• Bitumen (hot applied)

• Used in cofferdams, void spaces, ballast tanks, under-carriage of cars & trucks, etc

Trang 25

Frosio 09 Application slide # 2

Good work practise

Trang 26

Application

Cleanliness and good housekeeping before, during and after application are one of the most important factors to have a good result

Good access is as important for a satisfactory application as the quality of the equipment!

Trang 27

Personal protection is a necessity

• Make sure to use adequate

protection while using paint

• Application on an offshore

installation

Cd-4934-30

Important to open the tin correctly !

• Remove all loose particles from the lid

• Loosen the lid

• Lift the lid away from the tin in such a manner that the

contaminants do not fall into the paint Application: Open_dirtytin1

Trang 28

Mixing of two-pack paints

• Component B is poured into the component A (base)

• Component B may have a high viscosity Make sure to add all of it

Empty the tin !

• Ensure correct mixing ratio

• Use mechanical agitator

• The applicator is well protected

Think of your health !

Cd-4930-58

Tools for mixing of paints

• Always use mechanical agitator to ensure proper mixing

• Proper mixing will not be achieved by a stick

• A wooden stick may also contain dirt and loose parts that may contaminate the paint and clog the spray equipment

Cd-4930-57

Trang 29

• Mixing of a two-pack paint: Light coloured component A (base) and dark coloured component B

• Visual mixing control improves the mixing and thereby the performance of the paint

Cd-4930-59

Hand-tools for application of paint

• Stirrer: Only to

be used for small tins

• Round paint brush

• Flat, short paint brush

• Radiator brush

• Small back roller

• Tape for masking

Cd-4934-04

Trang 30

Methods for paint application

Alternative 3.

1 Coat: Brush

2 Coat: Roller

Trang 31

Application of paint

Use of roller for application

on bare steel is not recommended.

Roller application will not ensure good wetting of the substrate.

Rollers and paint brushes left in a tin after the job is finished.

• The paint will dry / cure and the equipment is unsuitable for application of paint

• Waste of money !

Cd-4930-68

Trang 32

Poor coating performance

• To the right: Correct mixing and mixing ratio

• To the left: Insufficient mixing and / or incorrect mixing ratio

Cd-4930-60

Mixing of a two-pack paint Visual mixing control

• The dark base makes it easy to see when the mixing is complete

• This is not easy to see with a clear base

• Poor mixing results

in poor protective properties of the paint

Application: Mixingcontrol1

Trang 33

Heating of paint in hot water bath

• Particularly applicable under cold climatic conditions

• Unnecessary thinning of the paint can be avoided

• Unnecessary thinning: Increased drying period

Cd-4930-61

Ready to start?

Trang 34

Working with a Brush

Application by paint brush

Benefits

Good wetting of the substrate Forces the paint into the surface Better than roller on the first coat Good on areas with poor accessibility

Limitations

Gives low film thickness, many coats required Creates an uneven film Application speed is slow

Trang 35

different surfaces

• Large, flat surfaces:

Squared end brush with long bristles

• Narrow surfaces:

Angular cut brush

• Irregular surfaces and edges:

Round or oval brushes

Note:

High quality brushes give an improved paint film

A round (or an oval) paint brush is in many cases recommended.

• Paint brush “works” the paint well into the substrate

• Can be used on 1 coat as well as subsequent coats

• Limitation: The production rate

Cd-4934-05

Trang 36

Application by paint brush

• Application of the 1st coat

• Here, a round paint brush is used

• The paint brush works the paint well into the substrate

• Limitation:

Production rate

Angled, flat paint brush (radiator brush)

• For areas being difficult to access

• Long handle is not recommended

• With long extension: Not permitted offshore

Cd-4934-07

Trang 37

Good quality paint brushes must be cleaned properly to maintain its properties

• Often the paint brushes are left without any kind of cleaning

• If properly cleaned and stored they can be reused

• Use suitable thinner or cleaner

• Final cleaning with water and soap before storing it properly

(not shown on video) Application: Cleaning_brush1

Working with Rollers

Trang 38

in the paint filmGives low film thickness, many coats required

Application by roller

Roller application

• Roller application will not force the paint into the profile of the substrate, but rather deposit it over the peaks

Trang 39

Application tool Small back roller

• Type of roller to use must be selected on what

to paint and the type of paint to use

• Thin naps for glossy top coats

to paint and the type of paint to use

• Well protected painter

Trang 40

Application by roller

• Type of roller to use must be selected on what to paint and the type of paint to use

• Not recommended to use roller on the 1st coat.

Cd-4934-11

Superstructure Application by roller Two men working from a dock arm

This is often seen where it is environmental restrictions Spray dust may contaminate near by objects (Overspray / wind)

Cd-4934-12

Định dạng
Số trang	377
Dung lượng	18,85 MB