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1. EXAMINATION SCHEME
As per the present scheme, API 653 examination is one-day, 8-hour, 2 session examination, comprising of pre-lunch session (4 hours) for “open-book” examination and post-lunch session (4 hours) for “closed-book” examination.
There are a total of 150 questions carrying 1 mark each (total of 150 marks), split into open-book (approximately 50 questions) and closed-book (approximately 100 questions). The distribution of 50 and 100 questions respectively for open-book and closed-book examinations is approximate; however the total is always 150 questions.
Each question is multiple choice questions with given 4 possible choices. Only one is the correct choice. The candidate has to pick-up the correct choice and indicate the same on separate answer sheet. The answer sheet along...
Saturday, September 8, 2012
Thursday, September 6, 2012
BGAS Painting Study Material Chapter 2 continuation
Profile measurementIf a profile requirement is specified, it is the inspector’s duty to ensure that the specification requirements are met. This can be done in two ways.
By measuring – using gauges with and without replica tape.
By assessing – using surface comparators.
The dial gauges are still very often used. The dial gauges fall into two categories
Surface Profile Needle Gauge
Dial Micrometers with Replica Tape.
Surface Profile Needle Gauge.The gauge is applied to the blasted substrate and the needle can be felt to locate a trough. Then by applying a slight pressure to allow the flat ‘foot’ of the gauge to...
Wednesday, September 5, 2012
Painting Defects
Viscosity DropLow viscosities may be simply due to incomplete stirring or the addition of too much solvent. The viscosity may decrease on standing in water-borne paints due to enzymic attack on the thickeners used. Modern latex paints use thickeners that are not readily attacked by bacteria. Changes in the orientation of the pigments (for example partial flocculation) may reduce the viscosity.
Wrinkling, Webbing, Frosting and Gas CheckingWrinkling is the development of wrinkles in the paint film as it dries, usually due to the formation of a skin. Defects similar to wrinkling are webbing, frosting and gas checking. Webbing is the development of wrinkles, usually in a well defined pattern and if it occurs in an oven it is called gas checking. Frosting is the formation a haze which is due to...
Painting Defects
SettlingThis is the separation of the pigments and occurs to a certain extent in all paints. It becomes a serious defect when the pigment is difficult to reincorporate into the paint by stirring.The defect occurs due to the high densities of some pigments and can be accelerated by a drop in viscosity, the paint being stored at high ambient temperatures or by being subjected to vibration for example on long transportation by rail.The control of settling lies in selection of suitable pigments and the addition of additives that increase the viscosity of the paint.
Slow DryingSlow drying occurs when the paint remains tacky for an extended period of time. This will result in the film picking up insects or dirt before it is hard and will make repainting difficult.The main causes are:Too thick of...
Painting Defects
Orange PeelThis defect gives the paint finish the rough appearance similar to the outside of an orange. The defect is found in spray painting and is generally due to having the wrong solvent. It can also be due to an incorrectly adjusted spray gun.The solution is to use the manufacturers recommended thinner and to adjust and use the gun correctly.
PeelingPeeling is simply another type of flaking where the amount of paint film removed is greater.
Pin holingThe defect is the appearance of small holes in dried paint film. The problem is most probably caused by too thick a coat trapping solvents into the film, or by air bubbles. The defect may be due to not cleaning the surface before painting, using the wrong solvents in spray painting or incorrect air pressure. The problem can be solved by addressing...
Painting Defects
Floatation and FloodingFloatation or floating occurs when a paint has been incorrectly formulated with two or more different colored pigments when one of the pigments floats to the surface giving different differences. On close examination the surface appears mottled with regular shaped cells.Flooding is similar to floatation in that one of the pigments migrates to the surface when the paint is produced using two pigments with different densities. These defects are corrected mainly by better paint formulation.
GassingThis is the formation of a gas, usually by hydrogen, by the reaction of reactive pigments, like Zinc and Aluminum, with acidic materials in the resin. It can be overcome by better formulation or packaging the paint separate from the pigment and mixing the ingredients prior to...
Painting Defects
Dirt RetentionThis is the deposition of dirt and dust on the paint film. For certain types of paint, the dirt may become entrained into the surface. The paints that resist dirt retention are high-gloss enamels while the low gloss latexes are the most susceptible to this defect.
FadingFading is the decrease in the intensity of the color after exposure. It should be tested for after removal of any chalking that may have occurred as this will tend to mask the actual fade of the pigment. In general organic pigments, especially those of low cost, will fade more than pigments that are inorganic. More expensive coatings especially prepared for exterior exposure will resist fading more than less expensive paints.
Fish EyeThis defect is indicated by small round imperfections in the top coat. The defect...
Painting Defects
BronzingThis is a defect that was often observed on cars painted red or blue where after a period of time a characteristic red tone developed on the paint surface. The cause was older types of pigments like phthalocyanine or Prussian blues. The defect is not common with the pigments available today. ChalkingChalking is the powdery deposit on the surface of the paint which dulls the gloss and appears after exposure. This defect is usually associated with long exposures to sunlight and is a natural degradation of the paint film. Some combinations and types of pigments and resins show more pronounced chalking than others.CheckingChecking is the appearance of wide splits with round edges that occur in the top coat. The cause is usually due to the surface not being clean (could be old paint) or...
Painting Defects
BlisteringThis defect is the appearance of irregular blisters on the paint finish.This defect can be caused by:Not correctly cleaning substrate
Contamination of the brush, air gun, line etc.
Using wrong thinner or incorrect amount of thinners
Old paint surface
Excess film thickness
In timber finishes, not allowing the solvent, particularly paint removers , to evaporate before repainting
This defect may be overcome by:Cleaning all surfaces free of grease and allowing the solvent to evaporate.
Using recommended thinner at correct ratio.
In spray applications, inspect so that water does not build up in the traps, especially in humid weather.
Check that the new paint is compatible with the old surface.
Do not apply paint films too quickly and allow solvents...
Painting Defects
BGAS Painting Inspector Exam Painting Defects Name and Definition
BandingThis defect is found in spray applications where there is heavy application of paint on the outside of the spray pattern with little paint in the canter of the fan.The cause can be:Too much air pressure
Uneven lapping of the spray gun
Having the gun too close to the job
The remedy may be found from:Use at correct air pressure
Ensure that the overlap of each stroke is 50% over the previous coat
Hold gun at the correct distance from the job - about 15 cm for lacquers and 25 cm for enamels. To correct a coat that has been applied, re-coat with double coat using thinner that has been specifically recommended for the paint using indicated solvent ratio and pressure, and ensuring that the gun is...
BGAS Painting Study Material Chapter 2 continuation
ProfileSurface profile, Anchor pattern, key, Peak to trough height and Amplitude are all expression meaning the cross section of a blasted area, as measured from the top of the peaks to the bottom of the troughs. The surface profile requirements are given on the specification for the job, e.g. for B. Gas 30 – 75 microns.
Shot blasted profileFigure 2.1 Terms relating to preparing surfaces
Grit blasted profile Figure 2.2 Grit blasted profile
*Hackle – A small surface lamination, which stands upright like a needle after blasting. Approximately ≤ 13 mm. Easily removed.
*Lamination (slivers) – Appears to be a longitudinal ‘crack’,...
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