油漆施工学习.pptx
Paint ApplicationMethods of Application Brush Roller Conventional Spray Airless Spray第1页/共52页 Material to be applied Substrate Environmental Considerations Transfer Efficiency Clean-up considerationsPaint Application Choice of Method第2页/共52页 Not as simple as it appears Quality&size of brush important Work quickly&methodically Very useful for stripe coats in a tank Coverage up to 100m2/man dayPaint Application-Brush第8页/共52页Ballast Spaces-Stripe Coat ApplicationPaint Application Stripe Coats第9页/共52页Ballast Spaces-First Full Coat ApplicationPaint Application Stripe Coats第10页/共52页Ballast Spaces-Final Coat ApplicationPaint Application Stripe Coats第11页/共52页 Faster than brush(coverage 200-400m2/man day)Poor in tight areas and on pitted steel Rollering needs less skill than other methods Only low film thickness achieved Quality of roller very important(not synthetic)Paint Application-Roller第12页/共52页Application by Brush and RollerPaint Application-Roller第13页/共52页 Compressed air atomizes the paint at the tip A mixture of air and paint is sprayed Because air mixes with the paint it must be clean&dry(so oil and moisture separators)For atomization,paint must have low viscosity,and so can only achieve low film thicknesses.Coverage of up 400-750m2/man dayPaint Application Conventional Spray第14页/共52页Paint Application Conventional Spray第15页/共52页Paint Application Conventional Spray第16页/共52页 By far the most widely used method of application in the Marine industry Called“airless”because there is no air mixed with the paint-it is atomized purely by the very high fluid pressure of the paint.Paint Application Airless Spray第19页/共52页Airless Spray UnitPaint Application Airless Spray第20页/共52页Paint Application Airless Spray第21页/共52页Airless SprayAdvantagesDisadvantagesSpeed of Application(1200m2/man/day)Health&Safety(High Fluid Pressures)Reduced overspray(vs Conventional Spray)Clogging ProblemsApplication of High Viscosity CoatingsLack of versatilityHigh dft in one coatClean-up considerationsPaint Application Airless Spray第22页/共52页Safety Catch OFFPaint Application Airless Spray第23页/共52页Safety Catch ONPaint Application Airless Spray第24页/共52页 Datasheets state fluid pressures for application,but on the pump can only read input air pressure.(50psi on a 40:1 pump=2000psi fluid pressure)Maintenance of equipment important Use of recommended tip size(not worn tips)Pressure drops by:-Paint viscosity Length of the line Vertical pumping distance.Paint Application Airless Spray第25页/共52页BAD set up:-Pressure drops by Line length HeightPaint Application Airless Spray第26页/共52页GOOD set up:-Short hose length Pump raised so gravity on our sidePaint Application Airless Spray第27页/共52页 Spray 12-14”(30-35cm)from surface Start moving before pulling trigger Move parallel to surface so gun is at 90o Overlap each pass by about 50%Individual blocked areas should be overlapped when painting large areas Crosshatch technique for applying thick coatingsAirless Spray Procedures第28页/共52页90Paint Application Airless Spray第29页/共52页Paint Application Airless Spray第30页/共52页Paint Application Airless Spray第31页/共52页Paint Application Airless Spray第32页/共52页Paint Application Airless Spray第33页/共52页Airless Spray TipsSpray FanFan Geometry is dependent on angle&shape of the tip orificeLiquid Coating under high pressureAtomised paint第34页/共52页Airless Spray TipsSpray Gun HeadSpray Gun TipOrificeSlot AngleSpray AngleLiquid Coating under high pressure第35页/共52页Airless Spray Tips At front of tip is an elliptically shaped slot which produces a similarly shaped spray pattern(fan).Normally vertical but can be changedFan Width第37页/共52页Airless Spray TipsPoor atomisation leads to:-1)“Horning”Streams of non-atomised paint2)“Fingering”Streams of non-atomised paint第43页/共52页Airless Spray TipsDefects such as horning and fingering can be caused by other factors such as low paint pressure and high paint viscosity.The easy way to fix these is to add thinners but this is technically unacceptable and usually trying to compensate for poor quality equipment or set-up.Paint is supplied ready-for-use so always check other factors first.第44页/共52页Use thinners only when necessary.Use correct thinners for the product(check datasheet).“Thinner”&“Cleaner”may be different.Usual maximum is 5%,otherwise:-cause solvent entrapment.cause runs,sags,slumping etc.retard cure.alter the volume solids and affect the wft/dft ratio.Using Thinners第45页/共52页This is the time period after mixing before the two components become too reacted for the paint to be used.The“pot life”is temperature related-the higher the temperature,the shorter the pot life.Exceeding the pot life can:-waste paint and block airless-spray equipment.affect the adhesion&properties of the coating.Pot LifeDO NOT APPLY PAINT AFTER POT LIFE TIME EVEN IF IT LOOKS OK!第46页/共52页Paint should NOT be applied in adverse conditions.Below 50C-unless using low temp.cure paints.Above 350C-dry overspray.Very windy conditions-heavy overspray losses.Wet surfaces(rain,snow,ice,fog,condensation).Application Conditions第47页/共52页Measure&record the wet and dry bulb temperature readings from a“whirling hygrometer”.Calculate the“relative humidity”(RH)and“dew point”.Measure the surface temperature with a digital thermometer on the vessel area that is to be coated.Allow painting when the surface temperature is 3OC or more above the dew point.Checking the Conditions第48页/共52页Apply the paint at the correct wet film thickness(wft)to give the specified dry film thickness(dft).The wft:dft ratio is dependent upon the volume solids.The wft must be checked as soon as the paint has been applied i.e.before solvent evaporation.Adjust application technique the correct wft is achieved.The dft can be checked later but this will read total thickness of both the new coat and underlying coats.WFT/DFT第49页/共52页Extensive studies of vessel applications has shown:-Minimum dft achieved is 40%of that specified.Maximum dft is 250%of that specified.dfts measured follow a normal distribution curve.Variations can be reduced by“volume area control”.Film Thickness Distribution第50页/共52页Paint Application第51页/共52页
