PAINTING – ERS (ENGINEERING RESEARCH SCHOOL)
1.
What is the Swedish standard of surface preparation and how does it differ from BS 4232? SIS – 05 – 5900 is the Swedish standard of surface preparation. It is a pictorial representation.
2.
State the Swedish grade of blast cleaning and compare them to BS 4232.
SIS – 05 – 5900 Sa 3 – White Metal. Sa 2 ½ -- Near White Metal (Very thorough blasting) Sa 2 – Thorough blasting Sa 1 – Light Blasting
3.
BS 4232 First Quality Second Quality Third Quality N/A
Identify three abrasives used in blast cleaning and state their use, advantages and disadvantages. Chilled iron grit, crushed slag, ceramic grits. Chilled iron grit: Excellent all purpose abrasive, due to its relatively high density which gives high particle energy, maintains sharp cutting edges on the grit. Can be reused causes rogue peaks if directed at a particular place for a quiet long time. Crushed slag: From a metallurgical process it is cheap / expendable abrasive. Quiet effective grit for one use only. No reclamation due to their rapid break down to dust. No reuse. E.g. copper slag, aluminium. Ceramic grits: Expensive grit. Retains their sharp cutting edges. Can be used on hard base materials. Used at lower pressure on thin metal and on stainless steel, non-ferrous materials as they are inert and do not stain or discolours.
4.
What do surface profile and amplitude mean? The shape of a cross – sectional blast finish is known as surface profile. The size of profile as measured from the peaks to the troughs is known as the amplitude or peak to trough height. Page 1 of 85
5.
What is the maximum amplitude on BGC painting contract? 75 microns. (Max)
6.
30 microns (min)
Can sand be used as an abrasive in blast cleaning operation? No.
7.
How are the Swedish standards of wire brushing defined? St2 – Wire brushing by manual means, thorough scrapping and wire brushing. St3 – Very thorough scrapping and wire brushing by machine brushing.
8.
Describe the two blasting techniques that use water. Slurry blasting and wet blasting.
9.
What is a micron and how many are there in one thou? Micron is a measurement of film thickness. One thou = 1/1000 of an inch. 25.4 microns = one thou, 40 thou = 1 mm.
10.
How thick are imperial and metric values of a plastic backing of testex? Imperial = 50 microns Metric = 0.2 mil
11.
What disadvantages is associated with wire brushing? Care must be taken to avoid over brushing a particular area causing “Burnishing” a condition with a polished surface that has an adverse effect on coating adhesion. Very laborious and expensive.
12.
What is Jason’s hammer? Where could it be used, what restrictions are associated with its use? Needle gun is Jason’s hammer. Needle guns are used for cleaning difficult surfaces such as rivet heads and welds. They leave sharp edge craters and rogue peaks, and they have a tendency to push impurities into the surface. Page 2 of 85
13.
14.
Explain the footner process and sequence of operation. Phosphating – footner or duplex process: this technique involves a final treatment in a one to two percent phosphoric acid solution held at 80°c for one to two minutes. This leaves a thin a rust inhibitive phosphate coating on the steel surface to which the coating shall be preferably applied while it is still warm, possibly after a final wash. How does the flame cleaning process work and what precautions are necessary if it is used for BGC? Cleaning of the surface by passing a high velocity oxyacetylene flame over the surface to be cleaned. The process removes much of the mill scale and rust, but leaves a dust on the surface, which has to be removed by wire brushing.
15.
What is mill scale and is it more or less noble than steel? Millscale is an oxide of iron produced when the steel is manufactured. It is a result of hot steel coming into contact with air and forming oxides composed of three layers, FeO, Fe2O4 and Fe2O3. Mill scale is noble than steel.
16.
What is a rogue peak? What problem can it cause? Rogue peaks are peaks, which stand out above the required profile. They lead to spot or flash rusting.
17.
If a surface is designated Bsa 2 ½, what does it mean? Rust grade B, blast clean to Sa 2 ½.
18.
Describe the two methods of measuring the amplitude. Surface profile needle gauge: Relies on the needle touching the bottom of the troughs on the surface profile. Take 20 readings and calculate the average of amplitude. Testex tape: 1. Zero the micrometer ensuring flat contact point and clean tip of it. 2. Remove the paper backing from the testex tape and stick the testex tape to the surface to be measured. 3. Rub the testex into the troughs using a blunt instrument, until the peaks can be seen butting up to the transparent plastic. 4. Remove the testex tape from the surface and measure the overall thickness with dial micrometer. 5. Deduct 50 microns for the plastic backing from the reading to obtain amplitude. Page 3 of 85
19.
Give five essential requirements for abrasive blasting at site. 1. 2. 3. 4. 5.
20.
Removes surface contamination. It gives a surface profile. Economical and efficient way. Better results than other cleaning. Relatively safe.
Describe the action and purpose of dead man’s handle. Deadman’s handle is used for direct operator control, to stop of the flow of abrasive when the operator lets go of the nozzle.
21.
Where should air pressure for blasting be determined and how is it done? The pressure at the nozzle may be measured using the hypodermic needle gauge. This is placed through the hose near to the nozzle with the hole in the needle facing the nozzle at 45°.
22.
Identify two blasting nozzles by shape. State advantage of each. Straight bore nozzle concentrates most of the abrasive in the central area of the blast pattern, fringe area of lower blasting size. For small or repair areas and softer metals. Venturi shaped nozzle produces a large blast pattern with the whole area receiving relatively equal amount of abrasive. Gives an even blast pattern area over a relatively large area.
23.
Describe a test for detecting mill scale on a blast clean surface. An acidic solution of copper solution when applied to a blast clean surface will react by turning to bright colour on clean sheet but will turn to black colour if mill scale is present.
24.
Which BGC code of practice relates to blast cleaning at site? BS 7079.
25.
What is a polymer and where do they occur? Page 4 of 85
Polymer produced by the growth of suitable stable molecules called monomers. Monomers, they occur in synthetic resin, polyurethane. 26.
What is polymerization and how it is brought about? Polymers produced by the growth of suitable stable molecules called monomers. The process by these monomers are joined together is called cross-linking and the result as in the hardening of drying oil type of paint.
27.
What are convertible and non-convertible coatings? Convertible coatings are those that undergo a chemical change during the drying process that cannot be reversed e.g. alkyd epoxy. Non-convertible coatings are those, which after they have dried may be restored to the original liquid form by the application of solvent. E.g. Nitro cellulose and chlorinated rubber, thermoplastic resins.
28.
What are the basic components of paint? Paint consists of binders or resins in which pigment or colouring matter is suspended. Usually the binder is diluted by the addition of a solvent.
29.
What are the characteristics of M.I.O and its advantages? M.I.O –Micaceous iron oxide: It decreases the permeability of the film. Protects the substrate from the environment. Interferes with the corrosion reactions (inhibitors).
30.
What is the function of binder and pigment content? Binder consists of oil or resins or blend of oils and resins. It’s essential is the film formation, the ability to change from liquid film which flows to a more or less hard plastic film. Pigment is used for colour or to modify the physical properties of binder resins. To provide rust inhibiting properties. To protect the film from the effects of ultraviolet light and weather. To add body.
31.
Name eight binders. 1. 2. 3. 4.
32.
Natural drying oils Oleo resinous oils Convertible binder Non-convertible binder
– – – –
Linseed oil, tung oil Alkyds, resins Vinyl, nitro cellulose, chlorinated rubber. Epoxy, urethane, polyester.
What is the function of solvent and its main properties? Page 5 of 85
Solvents are volatile organic liquids used in paints to reduce the viscosity or consistency of the material and to facilitate the application of a uniform coating. 33.
Name five solvents and their associate binders. 1. 2. 3. 4. 5. 6.
34.
Water – Water based paints, emulsions M.I.B.K – Vinyl M.E.K – Epoxies. Acetone – Epoxy Turpentine / white spirit – Alkyds Toluene / xylene – Chlorinated rubber.
Explain T.L.V, M.A.C, P.P.M T.L.V – Threshold limit value M.A.C – Maximum allowable concentration P.P.M – Parts per million
35.
How is toxicity of a solvent measured? Tri – Tector can measure toxicity.
36.
Define the three types of drying mechanism. Evaporation: This involves the evaporation of a solvent from the vehicle, leaving behind a film of solid material. Chemical reaction: Polymerization – molecular growth by cross-linkage of the resins. Oxidation: This involves the conversion of the constituents of the vehicle to the solid state by chemical changes involving mainly oxidation by reaction with atmospheric oxygen.
37.
How do chlorinated rubber, epoxy and alkyd paint dries? By chemical reaction and solvent evaporation.
38.
What is meant by pot life and how does it differ from the induction period? Pot life is the time limit within which the mixed components can be used e.g. five minutes at 20°c. Induction period is the time of mix to the application time. Page 6 of 85
39.
What are plasticiers and what are they used for, give e.g.’s? Plasticiers are usually liquids and must have a minimum tendency to volatize so that they will remain in the film. E.g. camphor, castor oil, chlorinated waxes.
40.
What are dryers and why they might be added to oil based paints? Drying agent (Siccative) is added to an oxidative paint to speed up the drying process. Siccative increases the capacity of the binder to absorb oxygen.
41.
What is the formula for density? Density = Mass / Volume. (Units – gms / cubic centimetre)
42.
What is cathodic disbondment and under what conditions does it occur?
43.
If the impressed current is greater than the corrosion current then the cathodic disbonding may result. This effect happens when excessive CP current is sufficiently strong to begin to generate gases at the metal surface by a process of electrolysis of moisture on the surface. The gas generated pushes the coating from the surface and causes adhesion failure beneath the edges of the coating. Explain relative humidity and dew point. Relative humidity is defined as the amount of moisture (water vapour) in air compared with the maximum possible in air. It is expressed as a percentage. Dew point is defined as the temperature at which condensation occurs.
44.
Name five methods of paint applications. 1. 2. 3. 4. 5. 6.
45.
Brush application Roller application Dip coating (electrostatic technique) Electrostatic spray application Conventional spray application Airless spray application
State the advantages of airless spray over conventional spray 1. Airless spray applies most types of paint much faster than any other manually operated method of paint application. 2. As the paint is not under pressure the pump can operate from the manufacturer’s can. 3. Because no air is used, there is no over spray. 4. A uniform thick coat is produced, reducing the number of coats required. 5. A very wet coat is applied, ensuring good adhesion and flow out. Page 7 of 85
6. Most paints can be sprayed with very little thinning. 7. No thinnages on the spray pattern means no overlapping in each stroke with wide form pattern. This makes airless spray much faster than conventional spray. 8. Because of the even spray pattern and cleanage, cutting at angles can be achieved. 9. The single hose connection to the gun makes it easier to handle.
1. PAINT
1.
What is paint? Paint is a film-form in fluid that is spread in thin coats to decorate and or protect a surface.
2.
What does paint contain? Paint consists of binders, resins, pigments and extenders.
3.
What are the important properties of paint? 1. 2. 3. 4.
Provides adhesion to the surface being painted. Colour retention and stability. Gloss Permeability Page 8 of 85
5. Mechanical properties – Hardness, resistance to abrasion or expansion and contraction due to temperature changes. 4.
What influences the mechanical properties of a paint film? Nature of substrate and a coating with ideal characteristics.
5.
What is a binder and what does it do? Binder consists of oils or resins or a blend of oils and resins. Its essential function is film formation. The ability to change from a liquid film that flows to more or less hard plastic film.
6.
What are modern binders made from? Manufactured from synthetic or resins.
7.
What is cross-linking, ‘explain better in epoxy coating specification’? Polymer is produced by the growth of suitable stable molecules called monomers. The process by which these monomers are joined together is called cross-linking and the result is as in the hardening of the drying oil type of paint.
8.
Name the four groups of binders.
9.
1. Natural drying oils 2. Oleo resinous oils 3. Convertible 4. Non-convertible What are pigments?
-
Linseed oil, tug oil. Alkyd Vinyl, nitro cellulose Epoxies, urethane, polyester.
Pigments are small particles that are soluble in the paint solvents that may be used for colour or to modify the physical properties of binder resins. 10.
Name the two groups of pigments. Organic pigment In organic pigment
11.
-
Indian yellow. Titanium di oxide.
Why is pigment added to paint? To provide colour, hide the surface, protect the film from UV light and weather, decrease the permeability of film, rust-inhibiting properties add body.
12.
What is M.I.O. and what are its advantages? Page 9 of 85
M.I.O. – Micaceous iron oxide decreases the permeability of film. Protects from UV light and from the environment. 13.
What are extenders? Extenders are added to paints to add thickness e.g. chalks, china clay, and talc.
14.
What are anti skinning agents and what do they do? A drying agent is added to an oxidative paint to speed up the drying process. E.g. compounds of lead, cobalt.
15.
Name the two groups of paints. 1. Non – convertible coatings, e.g. nitrocellulose, thermo plastic resin 2. Convertible coatings, e.g. alkyds, epoxy resin.
16.
Name three ways a paint system can dry. Explain each method. 1. Evaporation of solvent from the vehicle leaving behind a film of solid material. 2. Oxidation involves conversion of the constituents of the vehicle to the solid state by chemical changes involving mainly oxidation by reaction with atmospheric oxygen. 3. Chemical reaction – polymerization. Molecular growth by cross-linkage.
17.
Explain convertible and non-convertible coatings. Convertible coatings undergo a chemical change during the process that cannot be reversed. Non-convertible coatings are those that can be restored to their original liquid form after they have dried.
18.
Name two heavy-duty coatings and what are their disadvantages? Coal tar, asphaltic bitumen. Applied at elevated temperatures 260°c, fumes – fire hazardous.
19.
What are plastic coatings and how are they applied? Use of plastics for corrosion resistant coating. 1. Dipping the preheated object into either a liquid plastic or a powder of plastic particles. 2. Spraying powder particles on to the heated object or through flame onto the Page 10 of 85
object. 3. By extrusion. 20.
What is the disadvantage of plastic coatings? Poor bonding to the substrate. Stresses induced by the heating / cooling cycle.
21.
What are self adhesive tapes? PVC or polyethylene backing with a rubber base adhesive wrapping tapes.
22.
What is polyethylene coating? Sintering a powder directly to the pipe, in much the same way as an epoxy powder. Hot extrusion on to an adhesive or mastic.
23.
Why is concrete coating used? It acts as ballast and ensures that the pipeline will have negative buoyancy even when empty.
24.
What is antifouling? To prevent growth of marine organisms.
25.
What are powder coatings? Use of thermo plastic powders.
26.
What are the requirements for priming paints?
27.
To secure good wetting of the substrate and provide adhesion to the substrate for the entire system. To control corrosion of steels (by inhibition). What are solvents? Solvents are volatile organic liquids used in paints to reduce viscosity or consistency of the material and to facilitate the application of uniform coating.
28.
What are the important features of solvents? Rate of evaporation if too slow leads to runs or sags, if too fast it leads to dry spray and poor film. Flash point – Fire hazard. Toxicity – Health hazard. Page 11 of 85
29.
What is the M.A.C of common solvents give values? M.A.C – Maximum allowable content limiting value for the exposure. Xylene Toluene Benzene Acetone M.I.E.K Carbon tetrachloride
30.
-
200 ppm 200 ppm 100 ppm 1000 ppm 100 ppm 10 ppm.
What are the Positive features 1. Excellent exterior durability
Alkyd
2. Good flexibility, recoatability 3. Excellent adhesion to moist surface and easier to apply.
Chlorinated rubber.
Epoxy
31.
1. Limited heat resistance. 2. Poor solvent resistant. 3. Blast cleaned surface required 1. Poor gloss, to exterior exposure. 2. Difficult to overcoat. 3. Mistakes possible in mixing and application.
Name four types of solvents. 1. 2. 3. 4.
32.
1. Fast drying. 2. Good chemical and water resistant. 3. Good exterior durability. 1. Excellent chemical and solvent resistant. 2. Excellent adhesion. 3. Good high build capabilities, and good long term performance.
Negative features 1. Poor chemical and solvent Resistance. 2. Fair water resistance. 3. Poor heat resistance.
Hydro carbons Alcohol Ketones Esters
– Turpentine, benzene, white spray – Methyl, Ethyl, isopropyl – Methyl, ethyl-ketone (MEK) – Methyl acetate, amyl acetate.
What are plasticiers? Page 12 of 85
Plasticisers are usually liquid and must have a minimum tendency to volatize so that they will remain in the film e.g. camphor. 33.
List solvents and associated paints. Water Water based paints Toluene / Xylene Chlorinated rubber Acetone Epoxies M.I.B.K Vinyl M.E.K Epoxies
34.
In paint manufacture explain pre mixing. Binder, solvent and dilutants are pumped in correct quantities through a centrally controlled pipe system into measuring and mixing vats, where measure quantities of pigment and possible extenders are added.
35.
What is dispersion? The raw materials mixed into a batch are dispersed by means of a dissolver, consisting of a shaft with a rotating seriated disc.
36.
Paint grinding? Name types of mill and explain. Pearl or sand mill: The paint is pumped into the sand filled mill from below in a vertical mill or from one end in a horizontal mill. The paint is pumped under pressure through a number of rotating discs, which creates strong abrasion effects and can cause very fine dispersion in the short time of its travel through the mill. Paint collected at the top of the mill at a rate upto 1000 litres. Roller mill: This unit consists of adjustable steel rollers, rotating against each other so that the paint is subjected to pressure and shear forces, which decrease the conglomerate size. The paint is removed from the final roller in the row by a scraper blade or knife. Ball mill: This consists of a rotating drum, part filled with steel or porcelain balls of about 2 – 3 cms. Dia. The mill is filled with the paint until the balls are covered and the drum is set in motion, the pigment conglomerates are ground down due to the abrasion between the balls. The rotation speed is slow, generally less than one revolution per second and the pigment size is controlled by the period of time the mill is operated.
37.
Explain final batch mixing. After grinding, the paint is pumped to final batching where more binder and or thinner are added while stirring in order to obtain the correct delivery viscosity. Page 13 of 85
Tinting colour adjustment and quality control adjustments may be performed, prior to loading the materials into the delivery containers. 38.
Draw the different sketches for various mills.
3. QUALITY CONTROL TESTING – PAINT Page 14 of 85
1.
What is specific gravity? Specific gravity is called relative density. Ratio of density of material and the density of water (comparison). SG = Density of x Density of water. It is a ratio. No units.
2.
How is testing for specific gravity carried out? Name the equipment. Equipment name: Weight per gallon cup. 1. 2. 3. 4. 5. 6. 7.
3.
Weigh the cup and lid empty. Fill the cup with the paint. Allow the paint to stand for two minutes. Excess paint removed. Clean external surface of the cup. Weigh the cup lid + paint. 6 – 1 = Specific gravity.
What is the typical specific gravity of paint? 1 to 1.75
4.
What is viscosity. Viscosity is the internal resistance to flow possessed by a liquid.
5.
How is viscosity calculated? By Ford Flow Cup No.4 1. Warm the cup. 2. Cover the hole at the bottom of the cup with finger and fill the paint. 3. Remove excess paint. 4. Start the stopwatch while simultaneously removing the finger from the hole. 5. Observe the time taken for the flow of paint to start to break into droplets. 6. Time taken in seconds is the viscosity value.
6.
What is the calculation for volume of solids? Volume of solids = D.F.T
x 100% Page 15 of 85
W.F.T 7.
What is used to find wet film thickness (W.F.T) how is it used? Wet comb gauge: It is pushed firmly into the wet paint so that the outer most teeth makes contact with the substrate. Held at right angles to the surface. Gauge is removed and the teeth are examined. W.F.T. lies between the last tooth i.e. coated and the first tooth that is uncoated. Midpoint between this is W.F.T.
8.
What is used to find dry film thickness (D.F.T) how is it used? Banana gauge – magnetic pull of gauge: 1. Calibrate the instrument on steel surface profile, which matches with the profile of the painted surface being measured. 2. Using shim of known thickness, calibrate the instrument in the range expected measured thickness will lie.
9.
What are the thickness of the shims used and identify by its colour? 25 microns 51 microns 127 microns 254 microns 508 microns
10.
– – – – –
purple dark blue brown white yellow
How is thickness measured on M.I.O and why? Metallic painting by W.F.T. By knowing the W.F.T. and conversion using the formula W.F.T. = 100 x D.F.T Vs %
11.
Explain the cross cut test method. Pressure sensitive tape, sharp knife, and rubber eraser. No. of cuts shall be six or eleven. Surface is clean and dry. 40-mm long space, cut 1 mm apart if carrying 11cuts, two mm apart for six cuts. Cut through the film in steady motion. Repeat the process in the opposite plane to give 1 mm or 2 mm. Inspect the cut to establish that the surface has been penetrated. Place the tape over the grid and smooth it by finger, then rub with eraser. Remove the tape after 90 seconds. After making Page 16 of 85
several cuts examine the cutting edge and discard if jagged or if tearing of the paint film. 12.
What are acceptable results of cross cut tapes? 5B: The edges of the cuts are completely smooth, none of the squares of the lattice is detached. 4B: Small flakes of the coating are detached at intersections less than five percent of the area is affected. 3B: Small flakes of the coating are detached along the edges and at intersections of cuts. The area affected is five to fifteen percent of the lattice. 2B: The coating has flaked along the edges and on parts of the squares. The area affected is fifteen to thirty five percent of the lattice. 1B: The coating has flaked along the edges of the cuts in large ribbons and whole squares have detached. Area affected is thirty five to sixty percent of the lattice. 0B: Flaking and detachment worse than grade 1B.
13.
Explain the X cut test. Pressure sensitive tape, sharp knife, rubber eraser are the materials required to carry out the test. Surface should be clean and dry. Make two cuts in the coating each approximately 40 mm that intersects near the middle with an angle of 30°. Inspect the cut to establish that the surface has been penetrated. Using a piece of tape 75-mm, place the centre of the tape at the intersection of the cuts, smooth the tape by finger and then rub firmly with eraser. Brush the area lightly with soft brush, remove the tape after approximate 90 seconds by taking one end and rapidly. Examine the cutting edge of tool for signs wear and replace when needed. Inspect the cut area and rate the adhesion.
14.
What are the acceptable results of X - cut tests? 5A: No peeling or removal. 4A: Trace peeling or removal along incisions. 3A: Jagged, removed along most of incisions upto 1.6 mm on either side. 2A: Jagged, removed along most of incisions upto 3.2 mm on either side. 1A: Removal from most of the area of X under the tape. 0A: Removal beyond the area of X.
15.
Explain pull of test. A dolly made of aluminium alloy is stuck on to the coating system under evaluation using araldite adhesive. After the adhesive has cured, the dolly is removed by direct pull-of using a special tool and the force required is measured. Page 17 of 85
16.
Explain flash point and how this is obtained? Flash point of a material is the lowest temperature at which the vapours given of will ignite when a flame or spark is passed over it. Flash point is obtained by the use of Abel cup. Fill the test cup with the paint and place it in the water bath, which is heated to the required temperature. Light the ignition device when the paint has reached the required temperature. Carry out flame test. Raise the temperature by 0.5°c and repeat ignition, in steps of 0.5°c raise until the flash point is reached. Read the thermometer reading of the temperature accurately.
17.
What is relative humidity? It is the amount of water vapour in the air expressed as a percentage and it is obtained by a calculation made from the dry bulb and dew point temperatures.
18.
What are acceptable application conditions for blasting and painting? Paint should be applied only to the surfaces that are thoroughly dry and under such conditions of humidity and temperature, as it will promote evaporation, rather than condensation. Other factors to be aware are strong hard sunlight, strong winds which could cause too rapid evaporation of solvents and the paint film being impregnated with dirt etc., Bgas Specification 1. The air or metal temperature is atleast 3°c above the dew point temperature. 2. The relative humidity is less than 90%. 3. The temperatures for the applications are within the manufacturer recommendations.
19.
What is dew point? Dew point is the temperature at which condensation of water vapour in the air would form on the surface.
20.
What equipment is used to find humidity and dew point? Explain its use. Using whirling hygrometer, 1. Check the fabric of the wet bulb is clean, wet and secure at both the ends. container should be full of clean water. 2. Whirl the hygrometer at about three revolutions per second for one minute. 3. Read both the thermometers, noting the wet bulb first. 4. Whirl again for another minute. Read temperature again. Repeat until constant temperature reading are obtained. Page 18 of 85
5. Records wet and dry bulb temperature. 6. Calculate relative humidity, dew point using chart. 21.
How is surface profile measured? Model 123 - surface profile gauge is a quick, direct reading and easy to use instrument. The gauge is first set to zero by leveling the foot and the pointer on a flat surface. When the foot is subsequently pressed against a blasted profile, the foot will rest upon the peaks and the pointer will penetrate the valleys. The dial will show reading. Take ten such readings and take the average of it.
22.
What is BS 7079? Preparation of steel substrates before application of paints and related products.
23.
What is the maximum time between blasting and painting? Four hours.
24.
What specification is used to define this time? BS 5493.
25.
Name the four international standards for blast cleaning. 1. SSPC - Steel Structures Painting Council. 2. NACE - National Association Of Corrosion Engineers 3. SIS - 05-5900 - Swedish standard - pictorial surface preparation standard for painting steel structures. 4. BS 7079 - British Standard Specification.
26.
List blast cleaned surface i.e. give comparison of blasting grades to the above standards. Comparison of blasting grades. SSPC
White metal (SP5) Near white metal (SP10) Commercial finish (SP6)
BS -7079, SIS - 05-5900 Sa 3 Sa 2.5
BS 4232 depreciated First quality Second quality
NACE Grade 1 Grade 2
Sa 2
Third quality
Grade 3 Page 19 of 85
Light blast and brush Sa 1 off (SP7)
27.
N/A
Explain the test for soluble iron. Test paper - soaking of filter paper in a freshly prepared 5% solution of potassium ferricyanide in water and allowing the paper to dry. When pressed against a wet steel surface it will show a blue colour whenever soluble iron salts has been dissolved by water.
28.
Explain test for soluble sulphates. Filter paper soaked in a barium chloride dehydrates 6% wet solution and dried. The dry paper is then pressed against the test surface backed by a second paper soaked in saturated potassium permanganate, contamination is absorbed and held in the barium sulphate lattice, imparting a pink colour to those parts of the paper which contacted sulphates.
29.
Explain the soluble chlorides. Filter paper wetted with silver nitrate 2% wet solution and then pressed against the steel surface for about twenty seconds. It is then peeled off and thoroughly washed in chloride free water. Immersion photographic developer can detect any silver chloride formed remains in the paper. Chloride sites shows brown - black areas.
30.
Explain test for mill scale. An acidic solution of copper solution when applied to a blast cleaned surface will react by turning to a bright copper solution on clean steel, but will turn to a black colour if mill scale is present.
31.
Explain the test for oil contamination. Shinning on ultraviolet light source on the surface causing the oil to fluorescence. Pouring solvent across the surface, the solvent should form a continuous flow and not break into droplets.
32.
Explain the test for dust. Use of strip of clear cello-tape 25-mm wide strip. Press the tape onto the surface lightly rub over the tape with finger, then snatch the tape off. Any loose dust will stick to the tape and will show up clearly when the tape is put onto white paper. Page 20 of 85
33.
Explain care of blasted surface. Surface prepared for coating should not be allowed to deteriorate or the contaminated in anyway between grit blasting and spraying. Blasted surfaces should never be handled or touched unless hands are protected with clean gloves.
4. SURFACE PREPARATION
1.
What is used to detect pinholes in paint? DC Voltage - wet sponge (low voltage) test by holiday detector.
2.
What is tacking? Coating has partially set only; surface is not wet but has a sticky feel, like tape, due to excessive thinner, insufficient drying time, low temperature.
3.
What problems result from poor mixing of paint? Poor opacity, slow drying, poor gloss.
4.
What type of stirrer is used when mixing by hand? Properly made stirrer should be used which is long enough to reach the bottom of the container and with a broad, chisel like edge and a comfortable handle. Page 21 of 85
5.
What percentage of thinner is normally required? Ten percent.
6.
What is the result of over thinning? Thin coating will result in poor durability and a lower resistance to corrosion.
7.
What is induction period? In multi pack paints, it is the time of the mix to the application time.
8.
What is pot life? The pot life is the time limit within which the mixed component can be used. E.g. five minutes at 20°c.
9.
What condition shows when paint is stored for long periods or in poor areas? On aging paint may tend to thicken or go out of condition. Paint tends to settle during storage and after prolonged period.
10.
What is drying time? Drying time is the period when, 1. Solvent is evaporating from the film 2. Curing by oxidation or when chemical reaction is taking place.
11.
What is drying time affected by? a. Temperature b. Paint film thickness. c. Ventilation (concentration of solvents immediately above the surface)
12.
What do manufacturers data sheets quote for drying time? Touch dry: When the film is no longer tacky. Hard dry: When the film is sufficiently hard to permit measurement of D.F.T. Full cure: When maximum chemical resistance has been built up within the coating. Page 22 of 85
13.
What data would you require from manufacturer prior to paint application? Paint manufacturers should quote the temperature at which the drying times are applicable e.g. 20°c.
14.
What improvement to a paint surface would blast cleaning have over other methods? Better surface preparation improves the performance of any coating.
15.
What is the fundamental principle of blast cleaning? It is the removal of rust, millscale, or other surface contaminant by projecting a highly concentrated stream of relatively small abrasive particles at high velocity against the surface to be cleaned.
16.
What type of abrasives can be used? Chilled iron grit, crushed slag's, ceramic grits.
17.
The degree of surface roughness is related to what? The degree of surface roughness and the rate of cleaning depend primarily on the characteristics of the abrasive grit used.
18.
What abrasives are commonly used? Crushed wall nut shells, glass and crushed slags, various metallic shots and grits.
19.
Why is sand and flint not to be used for blast cleaning? Due to health hazard - formation of silicosis.
20.
Name types of surface cleaning other than blasting. 1. 2. 3. 4. 5. 6. 7.
Water blasting Manual cleaning Flame cleaning Needle gunning Weathering Acid pickling Degreasing. Page 23 of 85
5. METHODS OF PAINT APPLICATION
1.
What points have to be considered when brush painting? Paint application has a significant effect on the life of a paint system. By employing skilled painters, applying paints under properly controlled conditions, and only suitable ambient conditions outside. Page 24 of 85
2.
What method of paint application is performed for primer and why? Brush painting is said to have achieved superior wetting and is the only acceptable way to apply some anti corrosive primers. Brush marks leads to areas of low film build. Rubbing action of a brush can be an additional aid to get good adhesion.
3.
What are the advantages and dis-advantages of roller application?
ADVANTAGES 1. Mobility and low equipment cost. 2. Cleaner than spray gun. 3. Faster than brush.
4.
DISADVANTAGES 1. Not suited for irregular surfaces. 2. Thin uneven coats with misses / pinholes. 3. Poor penetration, not suited for all types of paints.
When is dip coating used? Objects coated by dipping are usually part of a conveyor belt system in which stowing is also involved in order to prevent more drips.
5.
Name methods of powder coating. 1. Fluid bed, electrostatic technique. 2. Electrostatic spray.
6.
Explain electrostatic spray with advantages and disadvantages.
ADVANTAGES 1. No over spray. 2. Very clean to use.
DISADVANTAGES 1. Not suitable for water thinned paints or heavily pigmented metallic coating. 2. Equipment is costly and not easily maneuvered.
3. Great saving in paint
7.
What types of spray pumps are used? 1. Air motors 2. Electrically driven hydraulic pump.
8.
Explain conventional spraying with advantages and disadvantages. Page 25 of 85
This involves using compressed air to both atomized paint and to convey it to the substrate. ADVANTAGES DISADVANTAGES 1. Highly quality finish. 1. Paint fog and loss of material. 2. Even film thickness. 2. High equipment cost. 3. Easy adjustment. 3. Not always suited for outdoor work. 4. Applies water borne silicates. 4. Unsuitable for high build and high viscosity paints. 5. Poor penetration, risk of over spray. 9.
Explain airless spraying with advantages and disadvantages.
ADVANTAGES 1. Very high work rate. 2. Good automation with little or no paint fog. 3. Pole gun for awkward places. 4. Only really suitable method for the application of high builds. 5. Good penetrator. 10.
DISADVANTAGES 1. High equipment cost. 2. Depends on power source. 3. Less mobile than brush / roller. 4. Risk of dry spray. 5. Adjustments only by changing the nozzle.
What are fluid tips and what do they control? Readily changeable part of the gun and are fitted by the retaining nut. 1. Controls the width of the spray pattern by varying the angle of the tip. 2. Controls the quantity of paint passing through.
11.
Why is a reversible head used? To save removing, cleaning and replacing the tip each time to clear the blockage by small particles of dust.
12.
13.
What type of fluid line hoses are used and why? Specially designed high pressure, solvent resistant, small bore hoses, reinforced with wire mesh, fitted with thread connection, swivel fitted between hose and the gun allowing free movement. (For remote location application) Explain the advantages of airless spray over conventional spray. 1. Airless spray applies most types of paint much faster than any other manually operated method of paint applied. Page 26 of 85
2. As the paint is not under pressure, the pump can operate from the manufacturer's can. 3. No air is used. No over spray. 4. A uniform thick coat is produced, reducing the number of coats. 5. A very wet coat is applied ensuring good adhesion and flow out. 6. Most paints can be sprayed with very little thinning. 7. Faster than conventional spray. 8. Even spray pattern, clean edge, cutting at angles can be achieved. 9. Single hose, easier to handle.
Page 27 of 85
6. INSPECTION, STANDARDS AND SPECIFICATION.
1.
What major factor determines the success of a coating? a. b. c. d. e.
2.
Environment in which it is placed. Temperature, the coating has to endure. Direct impact, mechanical damage, wear or erosion. Chemicals. Service conditions.
Why are environmental tests carried out during a project? a. Extremes of weather can be detrimental to the coating process. b. Moisture on the surface prevents film formation or reduces the quality of coating adhesion. c. High temperature may cause rapid evaporation of solvents or create a layer of coating at the substrate interface, which has not been able to flow. d. Low temperature may reduce solvent evaporation rate or interfere with the cure cycle of the coating.
3.
Explain how environmental testing is carried out? a. Measure the ambient temperature (air) and substrate temperature. b. Relative humidity and dew point by the use of whirling hygrometer. c. Surface temperature - magnetic dial type.
4.
When shall coating be not applied? a. During rain, snow or high wind. b. When the air or metal temperature is down to within 3°c of the dew point temperature. c. When the air or metal temperature is below 5°c. (according to the paint manufacture). d. When the relative humidity RH is above 90%. e. Substrate is wet.
5.
Explain how wet film thickness gauges are used? The wet film gauge should be placed in the coating film at a angle 90° to the Surface. Teeth are examined after immersion in the wet coatings on their surface Measures less than the W.F.T., while those with no coating measures more than Page 28 of 85
W.F.T. Mid of the values shall be taken. 6.
What is BS 7079? Preparation of steel substrates before application of paints and related products.
7.
What is rust grade D? Heavily corroded and pitted steel.
8.
What is the written equivalent of Sa 2 1/2? Second quality to BS 4232.
9.
How is surface temperature measured? By magnetic surface temperature gauge.
10.
How accurate are magnetic D.F.T. gauges? + / - 10%.
11.
What are the advantages of electronic D.F.T. gauge? Electronic gauges can be very good when they are properly calibrated. Accuracy is very precise. Capable of storing many measurements, making statistical analysis and printing the results on a computer pointer.
12.
What voltage is used for a wet sponge holiday detector? Operating at voltages below 100 volts. (normally at 67.5 volts)
13.
What standard describes the use of holiday detector? NACE standard RP - 01 - 88.
14.
What is testex? How is it used and what are their limitations? Testex tape Press - o - film is a replica tape composed of an incompressible Mylar backing of known thickness (2 mils) coated with a compressible film. Peel off one piece of tape, remove the backing tape and stick the tape on the blast cleaned surface. Rub the top surface of the tape (i.e. on the middle of the sticky section) with a blunt tool such as eraser head of a pencil, until the tape has picked up an Page 29 of 85
impression of the blast-cleaned surface. Set the dial tape micrometer to the zero mark. Put the tape into the jaws of the dial tape micrometer. Be sure it is placed on the tape window only. Measure the reading, subtract two mils from the reading. It gives the surface profile. If anchor profile is less than 0.8 mils or greater than 4.5 mils testex tape will not give a worthwhile measurement. 15.
When are high voltage holiday detectors are used and at what voltage? Holidays in virtually any thickness, 1000 volts - 20,000 volts.
16.
What is BS 4800? Schedules of paint colours for building purposes.
17.
What is 5493? Code of practice for protective coating of iron and steel structures.
18.
What is BS 3900? Method of test for paints.
19.
What is BS 5750? ISO 9000 series - Quality system.
20.
What is an inspector's prime concern? Monitoring quality on a coating project.
21.
Why are verbal communications important? Need to communicate effectively. Take an objective view of interpersonal skills.
22.
Why are written communications important? Writer is aware who will read the document, what is needed, to pass on the required information, describe the activities etc.,
23.
As an inspector would you be expected to supervise? No.
24.
As an inspector what do you consider as your main responsibilities? Page 30 of 85
a. b. c. d. e. f. 25.
To ensure compliance to the specification. To assess the quality of the work. To ensure safe working methods are adopted. To report the deficiency/any deviation from the set standards. To prepare inspection reports. To ensure adherence to good work practices.
Do you consider a good relationship with the client to be important? Yes. Good working relationship helps to resolve problems, to arrive at an amicable solution.
26.
What factors determine the level of inspection? Type of protection treatment, requirements of the coating, its end use, cost of inspection, quality of supervision to be expected of the coating applicator.
27.
What would you a painting specification contain? a. b. c. d. e.
28.
It should outline a procedure. How many measurements are to be taken, time interval when it is to be done? Which instrument to use. What would be the inspection authority and responsibility? Guideline for completion and submission of inspection reports.
What would a pre job conference provide? a. Contribute an understanding of the inspection criteria, which are specified, the tools and methods that will be used. b. Ensure that every class of the specification is understood. c. Highlight potential problems. d. To record the purpose of the meeting.
29.
What safety checks would an inspector carry out prior to blast cleaning? a. b. c. d. e. f. g.
Work permit obtained. Areas are cordoned of (restriction to entry). Earthing is done. Display of caution boards. An observer to watch the operation. Use of PPE, overall, bridging apparatus, shoes and ear defenders. Air inlet without any contamination. Page 31 of 85
h. Equipments are checked for their performance. i. Unauthorized entry restricted. 30.
What checks would an inspector carry out prior to painting? a. b. c. d. e. f.
31.
Check the masking of sensitive areas of site, electronic components, plates etc., Ensure existing coaters are protected from over spray. Check contaminant screens. Ensure that the hazard warning signs are in place. Check the equipment. Check the environment conditions.
What surface preparation checks do you consider to be most important? a. Visually examine the substrate prior to blast cleaning or power tool cleaning to ensure there is no inherent defects or detrimental contamination such as mud, oil, or construction debris. b. Check blast-cleaning air to ensure it is free of oil and water. c. Check that the oil and water traps are functioning and empty of water. d. Observe the surface preparation looking for unusual surface conditions/colouration. e. Visually check the abrasive being used. f. Measure anchor profile atleast once for each hour of blast cleaning. g. Surface cleanliness - does it meet the standard. h. Surface profile pattern. i. Unblasted areas. j. Make scotch tape test to ensure dust has been removed.
Page 32 of 85
7. HEALTH AND SAFETY.
1.
What documents state health and safety at work? Health and safety work act 1974 (HASWA).
2.
What year was the health and safety act passed? 1974.
3.
What is an inspector's first duty to access? Access the risk.
4.
How long would records of personal exposed be kept? Thirty years.
5.
What is E.P.A? Environmental protection act.
6.
What is V.O.C? Volatile organic compounds. Page 33 of 85
7.
What is the V.O.C. regulation on the maximum level of pounds per gallon? 4.5 pounds per gallon.
8.
How would structures coated by lead based paints be blast cleaned? Blast cleaning in an enclosed environment.
9.
Name some heavy metals used in coating and painting. Red lead, zinc chromate, chrome lead.
10.
Is personal protection equipment important (PPE)? Yes. It is a must for safe working.
11.
What types of filters are used for breathing apparatus? Charcoal filters.
12.
How would you remove or reduce risk? a. Ceasing to use the process, which uses the hazardous material, or by substituting an alternate material. b. Provide sufficient ventilation in the area to reduce the hazard to non-hazard. c. Enclose the area completely. d. Restrict access to the area. e. Provide protective clothing, breathing equipment, ppe.
13.
What type of protective clothing is required? Long sleeve cover-all, full leather protective suiting for the blast-cleaning operator.
14.
What is toxicity? Risk of explosion in an enclosed environment.
15.
What is L.E.L? Lower exposure level.
16.
What is P.P.M? Parts per million.
17.
What is used for gas testing - list equipment. Page 34 of 85
a. b. c. d. 18.
Explosive meter. Dragger meter. Tria tector. Oxygen meter.
When must a paint contractor register with the E.P.A? When applying more than twenty tons of paint or five tons of solvent.
19.
Painting contractors are monitored to ensure what? Hydrocarbons solvent emission rates are less than 50 mg of carbon per cubic metre coatings, 250 mg per litre of solvent.
20.
What is a work permit and why it is required? Work documentation system that must be followed before work is performed in a hazardous environment. Requirements for entry to confined spaces. Restriction on access, equipment and working method.
8. CATHODIC PROTECTION.
1.
What is corrosion? Corrosion is an electrochemical process. Corrosion is the decay or deterioration of the surface due to interaction with the environment.
2.
What factors can prevent corrosion? a. Material selection. b. Protective coating. c. Cathodic protection.
3.
Name seven types of corrosion. a. b. c. d. e.
Surface corrosion. Pitting corrosion. Stress corrosion cracking. Fretting corrosion. Crevice corrosion. Page 35 of 85
f. Corrosion in acid or alkaline environment. g. Bacterial corrosion. 4.
What factors influence corrosion? a. b. c. d. e. f.
5.
Temperature. Humidity. Surface condition of the metal. Time. Effect of stress. Atmospheric pollution.
How will coating help to prevent corrosion? a. Prevents or restricts contact between the environment and the substrate. b. Releases substances (inhibitors) which repel attack by the environment. c. Produces an electric current, which protects the substrate.
6.
What is cathodic protection? Cathodic protection is the process of reducing or eliminating corrosion by altering the flow of electric current in such a way that anodes become cathode.
7.
Name two types of cathodic protection system. a. Sacrificial anode system. b. Impressed current system.
8.
List metals in the noble order. a. Gold. c. Copper e. Lead g. Iron i. Aluminium
9.
b. Silver d. Hydrogen f. Nickel h. Zinc j. Magnesium
List anodes normally used for a. Pipelines in the ground b. Pipelines under the sea. c. Fixed sea structures
- Magnesium. - Zinc. - Zinc or Aluminium. Page 36 of 85
10.
Explain stray current effects. Other metal structures near to the ground bed may cause CP current to flow in an unpredictable fashion. Interfering structures to be connected to electric resistor.
11.
Explain cathodic disbonding. If the impressed current is greater than the corrosion current they are strong enough to generate gases at the metal surface by electrolysis of moisture on the surface. The gas generated pushes the coating from the surface and causes adhesion failure beneath the edge of the coating.
12.
What information can be gathered using survey techniques? a. b. c. d.
13.
Measurement of soil resistivity. Measurement of corrosion potential. Pearson survey (for location of holidays in coating) Interference survey.
What is mill scale? Is it more noble than steel? Mill scale is a thin black, flaky layer of oxidized iron formed on the steel during its manufacture. Mill scale is more noble than steel.
14.
What is calorising? Calorising is a method of impregnating aluminium powder on to and into a metal surface at high temperature (700 to 800°c) producing a surface with excellent corrosion resistant.
15.
What is stainless steel? It is an alloy of iron and chromium.
16.
What is corten? It is a low-grade stainless steel.
17.
What is Monel? Page 37 of 85
It is an alloy of 70% nickel, 25% copper and iron, magnesium and silicon. 18.
Where is cupro-nickel used? Where erosion and corrosion might occur.
19.
Explain an impressed current CP system. Voltage from an external power source called transformer rectifier is impressed on the circuit between the pipeline and buried earth connections known as ground bed resulting in a direct current being discharged. In discharging current to earth the ground bed material is subjected to corrosion. The impressed current system can be used in all types of soil resistivities, the greater the resistivity, the greater the driving voltage or number of anodes to achieve CP.
20.
Why corrosion is particularly severe in industrial and marine environments? a. b. c. d. e.
Variation in oxygen content on the steel surface (wet / dry) RH % (above 60% is critical) Presence of impurities in air (acids, alkali, salt etc.) Higher nobility metals in contact with the steel (e.g. mill scale) Temperature (ambient and substrate temperature)
PAPER 1. (B-gas) PAINTING GRADE 3,2. 1.
Describe why and how corrosion occurs. Corrosion is an electrochemical process called electrolysis, which results from an anodic reaction and atleast one cathodic reaction & metal iron reduction. Whenever a material which is having free +ve ions is immersed in an electrolyte have -ve ions or free electrons, metal is reduced to its oxide by chemical bonding process. This is called corrosion of metals. Page 38 of 85
2.
Describe what is meant by bimetallic corrosion. Bimetallic corrosion occurs when two different metals are attached close together. Th less noble of the two metals will act as an anode to the nobler one, the cathode and will sacrifice itself.
3.
Describe the following. a. The galvanic series: is that metals carry an order of nobility to corrode. This nobility is found by testing in seawater. Gold and silver corrode less quickly than copper mill scale, steel, aluminium and zinc. So we can use the galvanic series to bring about cathodic protection to steel. b. Mill scale: is a black flaky layer of oxidized iron found on steel during its manufacture. c. Rust grades to SIS 05-5900: There are four grades. Grade A - Covered with mill scale, with little or no rust. Grade B - A mixture of mill scale and rust. Grade C - No mill scale, surface is slightly rusted. Grade D - Heavily rusted and pitted. d. Blast cleaning grades to SIS 05-5900: There are four standards. Sa 1 - Light blast clean. Sa 2 - Thorough blast clean. Sa 2 1/2 - Very thorough blast clean. Sa 3 - Blast cleaning to visually clean steel.
4.
Describe the difference between water blasting and pressure washing. Water blasting is carried out at very high psi and with added abrasives to remove the most contaminations - can cut a profile in steel. Also very good in removing toxic coatings. It is excellent at cleaning tube bundles. Pressure washing is a lowpressure water system mainly used for cleaning painted surfaces, it can also be used with a detergent for removal of salts, chlorides, and contamination from substrates. Very useful tool in the maintenance paint field.
5.
Name two tests used to determine the presence of hygroscopic salts left on a blast cleaned surface. Potassium ferri-cyanide test - for soluble iron salts. Silver nitrate test - for soluble chloride salts.
6.
Name four expendable abrasives and state the difference between an expendable and a reusable abrasive. Page 39 of 85
Expendable abrasives - Glass flakes, copper slag, garnet shells, ice, walnut shells, coconut shells. Expendable abrasives - They cannot be reused after blasting. They fall with high impact over the steel surface and shattered, and on falling becomes powdery. Can be used only one time. Reusable abrasive - After blasting they can be reused upto twenty times. E.g. steel iron, shot with grit. It can be reclaimed, cleaned and monitored for the size before reusing. 7.
Name the three basic constituents of a solvent carrying paints and the functions each performs in the paints. a. Binder: It binds the particle together, holds them in suspension and gives the paint its finish, flexibility, gives good adhesion to the surface. It converts to a solid dry film and gives resistance to water, alkalis and abrasion. b. Pigment: Gives colour and opacity to the paint. Gives resistance to acids, alkalis, light. c. Solvent: Forms the evaporative part of the drying process. Thins the paint for easy application. Washes out the equipment and brushes can act as a degreasing agent if approved.
8.
Name six pigments and give their respective colours. Calcium plumbate Red iron oxide, Red lead Zinc chromate Phthalocyame blue Phthalocyame green Burnt umber Zinc phosphate Coal tar
9.
-
Creamy white Red Yellow Blue Green Brown White Brownish black.
Describe what qualities a laminar pigment gives to paint and name four pigments. It gives a high resistant coating to the passage of water, E.g. M.I.O, graphite, glass flakes, mica, aluminium flakes.
10.
Describe a) a barrier paint system, b) a sacrificial paint coating. A barrier paint system is a low permeability coating system, normally a four-coat system. Primer, tie coat, M.I.O high build and a topcoat. Page 40 of 85
A sacrificial paint coating is usually zinc or aluminium based paint, which is less noble than the steel substrate that is being coated. So the less noble is coating (anode) sacrifices itself to the nobler steel substrate (cathode). 11.
Describe what a tie-coat is and give three reasons why we may require one. A tie-coat is a paint, which can tie two normally incompatible systems together, mainly used for maintenance painting. It is used in anti-fouling system. Reasons: To get proper adhesion, to avoid bleeding, to avoid solvent stripping.
12.
Describe a typical paint manufacturing process and give the two types of paint mill which could be used. Select raw materials, mill the paint, carry out any QC testing requirements, can the paint, store in the warehouse and then distribute the paint. Direct charge mill, ball mill, attriator mill. Ball mill- it grinds all the raw ingredients together. Premix mill takes all the premixed ingredients and refines this mixture to high quality paint used in large batch in run.
13.
Describe what you know of viscosity and out line one method of testing. Viscosity is the measure of fluid resistance to flow. It is used to find the amount of solvent that is added to the paint. It is tested at 20° +/- 0.5°c. Ford flow cup # 4 is used. Bring your paint temperature to 20°c. place your finger over the hole of the cup, fill with paint, level off the paint with ruler. Note the time taken i.e. how long the paint flows before the break comes in the flow of the paint when you remove the finger from the hole.
14.
Describe what do you know of density. Density is weight per unit volume. Units = gms/cubic centimetre.
15.
Can you use a banana gauge over a. An M.I.O coating b. An aluminium substrate c. A galvanized surface
16.
-
No No. Yes provided it is over steel surface.
Describe a destructive test for determining the dry film thickness of paint. Page 41 of 85
PAINT INSPECTOR'S GAUGE (P.I.G): Cut a 'V' cut shaped channels over the paint film coated over an area. Place it over a microscope and measure the thickness of the paint and how many coats are there. To determine the compatibility between different coats. 17.
Give four artificial weathering devices and describe what they simulate. a. b. c. d. e.
Salt spray test - It is used to simulate marine environment. Water soap test - It is a test for paint film permeability. Tropical box - It is used to simulate high humid environment. Cold cracking test - It is used to check the contraction at very low temperature. Temperature cycling - It is used to simulate alternate low and high temperature of a paint.
18.
What is the name of the instrument which measures opacity and give two examples Cryptometer - a) Pfund Cryptometer, b) Hiding power chart.
19.
Describe a dolly test for adhesion. a. Clean the substrate coated with the paint. Degrease it and roughen. b. Attach dolly by regular araldite. c. Leave 24 hours time at 25°c. d. Afterwards cut a around dolly to isolate the substrate. e. Apply pull of force and note down the pressure (psi). f. Note at what pressure the failure occurs. g. What types of failure occurs (cohesive / adhesive)
20
How does the following work? a) Conventional spray set up b) Airless spray system c) Electrostatic spray system. a) Conventional spray setup is used for relatively low pressures and thin materials. Also the cup gun does not hold big quantities of paint. So you are forever filling them up. Also the gravity and suction guns can only be used in the upright position. b) Airless spray system is a very fast system for applying paint to very large areas, roughly one square metre perminute, large spray pattern and applies thick coating in one application. c) Electrostatic spray system requires a special spray gun, which applies charge to the paint particles. The substrate is positively earthed and the paint particles are given a negative charge at the tip as they leave the gun. So the paint particles go Page 42 of 85
to the earth and wrap themselves around the normally tubular components and a even coating is obtained, very little wastage of paint. 21.
How is BS 4800 used in the construction industry? It specifies 100 colours out of the 237 in BS 5252. It is used to identify the existing colour paint for which maintenance painting has to be done. It is useful for the manufacturer's to verify with the standard colours given in BS 4800 (100 colours).
22.
What are the essential differences between blister and osmotic blister? Expansion or contraction of the paint film against the substrate usually causes dry blisters. Osmotic blister is a blister, which contains gas, liquid, or crystal. It is caused by the entrapment of solvent, hygroscopic salts. It is usually dome shaped.
23.
What shall painting equipment comply with when being used on the Bgas site? To the paint manufacturer's recommendation.
24.
How do the following display their characteristics? Bleeding is a discolouration of a new paint applied over an old one. Bitumen and paints contain red pigments are particularly problematic. Blooming. It is where a finishing paint assumes a milky type appearance and the loss of gloss due to colour or dampened air settling on the paint before it was dry. Chalking. Paint becomes powdery or chalky. Break down of the binder due to ultraviolet light and also due to poor weather condition. Cissing. In-complete paint films due to paint over oil and grease. Grinning. Seeing the underlying surface through the finish coat. Colour contrast, lack of opacity. Flocculation. Separating out paint constituents in the tin and the refusal to be stirred back together again. Lifting. Attempting paint over, underneath a coating, which is not fully cured. The evaporating solvent will lift up, picking up. Roopiness. Brush marks in a painted surface. Solvent stripping. Paint with a powerful solvent will lift the coating underneath due to the power of the solvent. Oxidization. The drying process between certain binders and oxygen e.g. alkyd resin. Chemical curing. The mixing of two components which produces drying in a twopack paint. Overspray. Paint which is not going to substrate. Paint, which falls over an area which, is not required to be painted. Page 43 of 85
25.
Define the following, Dew point, Rh, Induction period, Pot life, Flash point, Shelf Life, Batch No., Masking out A.G.I, Rust blooming, Water borne coating, B Sa 2 1/2, Feathering, A St3, PA 9, P 10. Dew point: The temperature at which condensation would form on a substrate. RH: The amount of water vapour in the air expressed as a percentage and calculates from the wet and dry bulb temperatures. Induction Period: The length of time a paint is required to stand after mixing and before application, to allow the air bulb to escape and or chemical reactions to take place and is specified by the paint manufacturer. Pot life: The length of time (following induction) that a paint remains in an applicable condition according to the manufacturer's instructions. Flash point: The lowest temperature at which a given material will flash, if a flame or spark is present. Shelf life: Maximum interval in which a material may be stored in a usable condition. Batch number: Manufacturer's data number for production date. Masking out: Must be carried out on items to be protected during preparation and painting, items normally masked out are control equipment, fire protection equipment, weld ends, sensing and spraying heads, name plates. A.G.I: Above ground installation. Rust blooming: It is caused by moisture or humidity on new blasted steel and shows up before priming. Water borne coating: One whose solvent is water. It dries by coalescent. B Sa 2 1/2 : Rust grade B. Mixture of mill scale and rust. Prepared by very thorough blast cleaning. Feathering: Smoothing back the coating edge to allow repair. Paint to flow into and produce a smooth edges i.e. smoothing down of rough paint edges. A St3: Not possible. PA 9: B gas document properties and performance requirements refer to the ordering of paints and performance of paints systems. Any paint used on B-gas work must comply with PA 9. PA 10: It is the technical name specification for new and maintenance painting at works and site for above ground pipeline and plant installations and is arranged into three sections. Primary information, general painting information, information for specific painting applications.
26.
Give as much details as you can for the following. SPA 1: Applies to the painting at work or site of new installation and components and maintenance paint. (CS) SPA 2: For indoor use and short term uses. SPA 3: New installation and maintenance, above 100°c, upto 340°c, and above. SPA 4: Painting of damp ferrous surfaces. Page 44 of 85
SPA 6: Painting of non-ferrous surfaces.
PAPER 2. (B-gas) PAINTING GRADE 3,2.
1.
What kind of process is corrosion? Electro chemical process.
2.
What particular problems relate to the maintaining of an effective coating system in splash zone? Rapid change in oxygen, salt spray, growth of marine life, access to the working area is difficult. Wave impact and erosion. Mechanical damage due to ship movement.
3.
What factors influence the rate of corrosion? a. b. c. d.
4.
Variation in oxygen content on steel surface (wet and dry) RH percentage above 60%. Higher nobility metals in contact. Air borne acids, alkalis and salts.
What ills mill scale and why it is a particular problem when attempting to protect steel? Mill scale is an oxidized iron. Mill scale is nobler than steel so the exposed areas of steel (anode) will sacrifice itself to protect the mill scale (cathode).
5.
What is the number of the Swedish standard contained within BS 7079 and list the rust and blasting grades together with their brief relevant titles? RUST GRADE
BLASTING GRADE Page 45 of 85
Rust grade A - Covered in mill scale with little or no rust. Rust grade B - A mixture of mill scale and rust. Rust grade C - Mill scale, rusted with slight surface pitting. Rust grade D - Heavily rusted and pitted. 6.
7.
Sa 1 - Light blast clean. Sa 2 - Thorough blast clean. Sa 2 1/2 - Very thorough blast clean. Sa 3 - Blast clean and visually clean.
Name three tests for locating hygroscopic salts and mill scale on a blast cleaned surface. Potassium ferri cyanide test Soluble iron salts Silver nitrate Soluble chlorides Copper sulphate Mill scale What factors influence how clean and how rough the surface becomes after blast cleaning. Using the correct abrasives ensuring that size, hardness, density and shape are the correct for the substrate. Operator's ability to ensure proper speeds, angles and distance plus speed (time). Surface profile and cleanliness.
8.
Regarding hand and power tool cleaning state what always concludes this process and to what standards. Wire brushing: Brushes must be made from phosphor, bronze or beryllium bronze. St 2 - Thorough hand & mechanical cleaning (manual). St 3 - Very thorough hand & mechanical (mechanical). Used on rust grades B,C,D.
9.
What three basic ingredients make up a traditional solvent carrying paint? Binder, pigment and solvent.
10.
What are the functions of each of these three in a solvent carrying paint? Binders: It binds the particles together and holds them in suspension. Gives the paint its finish, makes the coating adhere to the surfaces, gives flexibility. Converts to a solid dry film, resistance to water and chemicals. Pigments: Gives colour and opacity to the paint. Resistance to alkalis, acids and light. Solvent: Brushes & equipment cleaner, thins the paint, degreases if approved. forms the evaporative part of the drying process. Page 46 of 85
11.
Name five items that can be included in paint to improve its performance or suitability for a certain use. Drier or catalyst, extenders, plasticiers, thixotropic agent, anti skinning agent, stabilizer.
12.
Identify six paints by their binder name. Polyurethane, alkyd, chlorinated rubber, epoxy, emulsion, aluminium, achrolic, vinyl, silicon, cellulose and zinc.
13.
Name four binder / solvent combination. Epoxy Chlorinated rubber Alkyd resin Emulsion
14.
Acetone. Xylene. White spirit. Water.
Name six opaque pigments together with their respective colours. Calcium plumbate Red iron oxide Red lead Zinc chromate Zinc phosphate Coal tar
15.
-
-
Creamy white Red Red Yellow White Dark brown or black.
Describe what a laminar pigment is. The laminar pigment (M.I.O, Mica, glass flakes) particle shape tiny hands or leaves, upon drying they interweave and overlap each other to form a leave type. Surface provides a low permeability to water.
16.
What is the difference between a convertible and a non-convertible coating? Convertible coating dries by chemically changing upon, afterwards it cannot be softened or damaged by its own solvent. Non-convertible coating dries by solvent evaporation only. It cannot be damaged or softened when it contacts with its own solvent.
17.
Define the term induction period.
Page 47 of 85
The length of the time, the two pack has to stand after mixing, before applying for allowing the air bubbles to escape and chemical reaction has to take place and is stated by the manufacturer. 18.
Define the term pot life. The length of time after induction the two-pack paint remains in an applying condition, according to the manufacturer's instructions.
19.
Define a barrier system of coating. This type of coating isolates the substrate from the environment by providing a low permeability coating system.
20.
Define the term tie-coat and give an example of its use. A coat used to apply over two incompatible coatings e.g. during maintenance painting.
21.
What is the difference between thermosetting and thermoplastic? Heat cured plastic, Thermosetting: They can be formed by heating and curing heat cured plastic. After setting they will not soften or degrease. Thermoplastic: They can be formed by heating and curing heat cured plastic. After setting, when they are re-heated it will become softer and become liquid and again can be reused.
22.
What is impressed current. What problem can arise from its incorrect setting up? Voltage from an external power source called a transformer rectifier is impressed on the circuit between the pipeline and buried earth connections known as ground beds resulting in a direct current being discharged. In discharging current to earth the ground bed materials are subject to corrosion. The impressed system can be used in all types of soil resistivites. The greater the resistivity the greater the driving voltage or no. of anodes to achieve CP cathodic disbondment will occur.
23.
Name two types of paint mill and give two examples of each. Page 48 of 85
DIRECT CHARGE MILL Ball mill Attritor mill High speed disperser mill
24.
PRE-MIX MILL Big mill (Ballotoni) Sand pearl and Bead mill Slurry mill
COLLOID MILL Simple roll Dried roll mill Triple roll.
What is the title of BS 3900? Method of test for liquid paint. How many test sets are in BS 3900? Eight. How are the tests identified (name, number)? Title and letter from A to H. A. Method of test for liquid paint films (excludes chemicals) B. Liquid and dried films include chemical examination. C. Test associated with paint film formation D. Opacity test on paints. E. Mechanical test on paint films F. Durability test on paint film. G. Environmental test on paint film. H. Designation of intensity, quality and size of common type of defect. General principle and rating scheme.
25.
What does a fineness of grind gauge measure? Grind gauge measures pigment grain size, how finely the pigment has been (grained) ground in the milling process.
26.
What is the flash point and by what apparatus is it determined? It is the minimum temperature at which the vapours of a liquid begin to ignite when the external source of ignition is introduced. The closed cup Abel type determines flash point.
27.
What is viscosity and what equipment is used to measure the viscosity of a free flowing paint and Thixotropic paint? Viscosity is the internal measure of fluid resistance to flow. a) Free flowing paint viscosity is determined by Ford flow cup no.4. Page 49 of 85
b) Thixotropic paint viscosity is determined by rotating viscometer/rota thinner, krebs stormer viscometer. Set the r.p.m through the window at 200 r.p.m. to make it a free flowing paint. Paint is put in the viscometer and paint is thinned similar to the ford flow cup no.4 test, note the time taken for the paint to be broken to droplets. Time taken in seconds will give the visocity. 28.
What is density cup and give an example of its use? Small black cup of 100 cc, which is made of aircraft alloy, is known as density cup. The lid in it has a hole in the top. Pour the paint inside the density cup. Close it with the lid. Wipe of the extra paint coming out of the hole from the cup. Weigh it by using the formula Density = Weight / volume. Find out the density of the liquid. Density cup is used for, a) To check the amount of solvent added to the paint. b) Whether the two-pack paint has been mixed to the correct ratio.
29.
30.
Calculate the volume of solids of the paint if the W.F.T was 186 microns and the D.F.T - 93 microns. VS % = D.F.T x 100 = 50% W.F.T. Calculate the W.F.T. of a paint if the Vs %ge was 66 and D.F.T was 88 microns. W.F.T = D.F.T x 100 = 133.3 microns Vs %
31.
Calculate the D.F.T. of paint if Vs % was 44 and W.F.T was 234 microns. D.F.T = W.F.T x Vs % = 102.96 microns 100
32.
Calculate the density of paint if a 5-litre tin weighed 15 kg. Density = weight = 3 gms / cu.cm Volume
33.
Calculate the density of two pack material if part A paint was 1.5 g/cu.cm and part B catalyst was 0.5 g / cu.cm (assume ratio 1:1) 1.5 + 0.5 = 1 g / cu.cm 2 Page 50 of 85
34.
Name an example of a nondestructive D.F.T. gauge and destructive D.F.T. gauge. NDT - D.F.T. gauge - Electronic gauge, banana gauge. DT - D.F.T. gauge - Paint inspectors gauge.
35.
Name four artificial weathering devices and say what they are designed to simulate. Salt spray test Tropical box test Water sock test Cold crack test Cracking
36.
-
Marine environment High humidity environment Test for permeability of paint system Test for low temperature Temperature cycling test for flexibility of paint film varying temperature alteration(high temp &low temp)
Name two drying / curing tests and state how they are operated. Drying / curing test: Ballotini test- hardened steel balls put over the wet paint film panel. Stylus test: It consists of a series of trailing needles. To find out tack dry, hard dry and fully cured. Cold leaf test: It is moved over the wet film since they are used in different tensions.
37.
What does a Cryptometer measure and give two examples of a Cryptometer. It is used to measure the opacity. Hiding power charts and P-fund Cryptometer.
38.
What determines the degree of gloss, a paint may possess. a) The ratio between binder and pigment. The fineness of the pigment grind. b) Fineness of pigment grind. c) Skill of spray painter. d) Method of application. e) Absorbing of the substrate for the paint.
39.
Name three adhesion tests and describe how one of them is carried out. a) Cross cut test b) Cross hatch test c) Dolly test.
Page 51 of 85
Clean, degrease and roughen the surface. Apply dolly with regular araldite and give 24-hrs time at 25°c. Cut around the dolly to isolate the substrate. Apply the pull off force and find out, 1. At what pressure (psi) failure occurs. 2. What type of failure occurs. Cohesive/adhesive. 40.
State the conditions under which B-gas allows painting to take place. a) The ambient or surface temperature should be atleast 3°c and above the dew point temperature. b) The relative humidity should be less than 90% c) Temperature condition for applying paint should be within the manufacturer's instruction. (maximum and minimum temperature)
41.
Name eight duties of a paint inspector. 1. 2. 3. 4.
Inspect and report He must act with integrity at all times and true to the specification. Learn the specification and familiarize with the plants and equipment used. Inspect the substrate condition (grade of paint) and select a suitable paint system as per the specification requirement. 5. Check whether dry bulb temperature, dew point & RH% is within the acceptable level or not. 6. Inspect the prepared surface for its surface profile and cleanliness (grade Sa 1, Sa 2, 2 1/2, 3) 7. Verify whether the correct material have been obtained for the paint application. 8. Witness paint preparation (mixing) and operation at site. 9. Measure WFT, DFT and check adhesion and curing. 10. Make reports - daily, weekly, monthly. 42.
List eight-contractor malpractice. 1. Using unqualified personnel. 2. Using unsafe plant and equipment. 3. Using equipment, which are in poor condition. 4. Proceeding to further coat without inspection being carried out. 5. Applying coat in wrong sequence, omission of a coat. 6. Apply a wrong paint. 7. Use of date, expired products. 8. Improper coating thickness. 9. Using more solvent. 10. Less thickness of coat. Page 52 of 85
11. Improper mixing of paint. 43.
Name three methods of applying paint and compare the advantages and disadvantages of each in-terms of quality and cost effectiveness. Brush: Cheap easy method, best for applying primers. Disadvantages - slow, covers small areas and messy to handle. Roller: Cheap and easy to apply. Disadvantages - uneven coating, orange peel effect. Conventional (air): Expensive (four to five times costlier than others), covers large areas. Disadvantages - overspray.
44.
What does BS 2015, glossary of paint terms refer to and give three examples? 1. 2. 3. 4. 5. 6. 7. 8.
45.
Bleeding: Penetrating and discolouring of paint coated over it. Blistering: Dome shaped blisters formed due to contraction - dry blisters. Osmotic blisters: It is formed due to entrapped liquid, gas and salts. Chalking: Pigment becomes chalky or powdery when it comes under chlorides, sulphides. Flocculation: Separating out of certain elements. Grinning: Seeing the underneath surface through the finish coat. Holidays: Poorly or missed coating. Pinholing: Holes down through the paint caused due to escape of gases.
What is BS 4800 and how is it used in the construction industry? It is arranged of 100 standard colours taken from the 237 colours contained in BS 5252 and used in the construction industry. It can be used to identify existing colours when maintenance painting and is a method by which all manufacturers can make exactly the same colour.
46.
How does B-gas define the following. Long term protection: Upto 10 years. Short term protection: Upto 2-3 years. Medium term protection: Upto 5 years. New galvanizing: A substrate coated with zinc galvanized surface where this cohesive oxide layer has not formed glossy and shinning appearance-less than three months old. Weathered galvanizing: Wire brushed with stiff brushes, more than 3 months old. A galvanized surface where the cohesive oxide layers has formed dull and lacking in sheen. Page 53 of 85
47.
What is the procedure for removing oil and grease from a surface before preparation commences? Because of oil & grease paint will not spread properly. White spirit should not be used. Use only approved solvent with safety precaution to be followed. For applying solvent use disposable swab. Do not use cotton rags. After solvent cleaning use a detergent pressure washing followed by clean water, rinsing and then drying it.
48.
What is the procedure for removing oil and grease from a surface, found after preparation has taken place? Use approved solvent and after degreasing, do pressure washing with 2% detergent followed by clean water rinsing and drying it off. Reblast and clean it.
49.
What is the procedure for removing Algae and mould growth from pipe work? Apply antifungicidal bi-oxidant over the algae and mould growth and give minimum twenty-four hours time. Leave it free for this period. After this time elapse use stiff wire brushes to scrub off, pressure wash with a detergent followed by clean water rinsing.
50.
Under what conditions must paint be stored? In ad dry, lockable, well ventilated building away from gas areas, flames, heat sparks and rays of the sun and follow any special storage condition.
51.
What is T-wash? What is it used for? What colour is it? How do we check for a correct reaction when using it? It is an etch primer. When applied first it provides a key for new galvanized steel. Blue in colour. Turns black upon drying. *T-wash should not be used in aluminium. Use PVB*
52.
What two coat paints are applied at works? High solid solvent based epoxy primer to 75 microns d.f.t. Epoxy m.i.o. Mid coat to 75 microns d.f.t.
53.
What distance must be left at areas to be welded when painting? Page 54 of 85
Seventy-five mm. 54.
How much must new paint overlap on old repairs? Hundred mm.
55.
What is the maximum allowed time for priming to take place following the preparation and by what method is primer applied? Maximum four hours follow completion of blasting. Except Spa 4 where priming is immediate. By brushing or spray as appropriate.
56.
What do B-gas class as hot duty services? One which reaches a temperature of above 99°c, when (it is working) in use.
57.
What must all pneumatically and electrically operated power tool equipment's should be done before use? Properly earthed.
58.
What type of sheeting may and may not be used for protection against spillage and spotting? Sheeting must be non-flammable. Flammable sheets like tarpaulins should not be used. (Fire hazard)
59.
What must not be used to clean out kettles or dispose of rubbish? Fire or flames.
60.
Give the rules for mixing of paints regarding sizes. Upto five litres may be mixed by hand. Above five litres must be mechanically mixed.
61.
What are osmotic blisters and what can cause them? Osmotic blisters are blisters, which contain liquid, gas or crystals (chlorides). Main causes are solvent entrapment, water entrapment, hygroscopic salts left on the blast cleaned surface. Page 55 of 85
62.
Some metals are difficult to prepare. Name three and describe how you might prepare them. 1. Aluminium sheeting extrusions: Infactory - Degrease in acid bath. Onsite - Etch and degrease with emery cloth and white spirit. Etch primer, zinc chromate (no lead paints). 2. Galvanized iron (steel dipped in molten zinc): Infactory - Degrease in acid or alkali bath (t-wash). Onsite - Allow to weather for several months or degrease with zinc chromate, calcium plumbate or etch primer. 3. Copper, brass and bronze: Infactory - Degrease in solvent bath. Onsite - Use emery cloth and white spirit (do not weather or dry abrade). Etch primer.
63.
Where does a pipeline leave the ground and what problems would you find and how might you treat this? Sketch:
1. Mechanical damage from back filling. 2. Rapid change in oxygen in soil, steel interface due to alternate wetting or drying conditions. 3. Soil may be chemically reactive. 4. Acid attack. 5. Will produce corrosion. - a) apply extra coating b) apply masking (polyethylene) c) better drainage to avoid standing water d) top mustle well seeded. 64.
What additional information would you record when maintenance painting a pipeline without removing the previous coats? 1. It needs to be established whether the existing system contains any toxic coatings as this will dictate the method of preparation used. 2. Are the existing coatings compatible to the new system interms of adhesion possibility of solvent stripping, possibility of bleeding. Get the information from the paint manufacturer. 3. Further information required. Nature and extent of surface contamination, extent of break down, extent of corrosion, where adhesion problems, solvent striping or bleeding might occur. A tie coat would be employed to prevent these particular problems arising e.g. inservice environmental condition.
65.
Name five paints and state their drying or curing method. Page 56 of 85
1. Emulsion - Coalescence - Evaporates without chemical action but it also gets dries like a non-convertible but acts like a convertible coating. 2. Alkyd - Solvent evaporation followed by oxidation. 3. Chlorinate rubber - Solvent evaporation only. Non-convertible coating. 4. Two pack epoxy - Solvent evaporation followed by chemical reaction. 5. Fusion bonded epoxy - Heat cured - Thermosetting, convertible coating. 66. 67.
Name a black pigment in common use apart from coal tar. Carbon blocks. What is a holiday detector and a pinhole detector? What does it detect, and how does it work? It is an electrical device applied to detect holidays, pinhole, voids etc., Coil spring type: 1. Preset the voltage. 2. Pass this holiday equipment through it (job). 3. Where there is a holiday present, it produces a spark, visual warning audio signal peep will be heard. 4. Speed of running the coil is 1ft - 2ft/sec. It need not be used on above ground conditions. It can also be used inside tanks, offshore structure, and platforms, on underground pipelines 100% holiday test is required. Brush shape, horseshoe type, coil spring type, wet spring type are the various types of holiday and pinhole detectors.
68.
If you worked on a contract where frequent stoppages occurred for poor weather, what additional information would you record? 1. 2. 3. 4. 5.
69.
Time of starting and stopping of work. Wastage of materials should be noted down. Extra reasons for weather. Progress of the work before the work is stopped. Record of damages to partly dried coating on to prepared areas (blasted).
If a pipeline was in direct contact with acoustic cladding what paint system might be applied if we wished to maintain it every three years or not at all? Cladding - No maintenance required. Acoustic cladding does not have any anti corrosion property. Acoustic cladding reduces the noise level by 10 - 20 dB. Thermal cladding is carried out to with stand the temperatures in between -10°c to +1000°c.
70.
What is important about selecting a paint system suitable for a certain environment? Page 57 of 85
Each and every paint has its own characteristics. Select a paint system that should with stand the environmental conditions and comply with the specification requirement. Marine conditions, high humid condition, too low temperature conditions. 71.
What information do B-gas require to be on a paint tin and what B-gas document deals with the properties and performance of paints. The document PA 9 properties and performance of pant. 1. Manufacturers name. 2. Transco identification number. 3. Description of the product. 4. Colour code (specified by Transco) 5. Any special storage requirement. 6. The expiry date. 7. Application grade (brush/spray) 8. Batch identification code. 9. Identification of parts, mixing ratio by volume (paint catalyst) 10. Any marking required by current legislation.
72.
What is unusual about the preparation of surfaces which are dealt by SPA 4? After blasting remove grit contamination with clean water.
73.
Describe what you know of HASWA and COSHH? HASWA - Health and safety at work act 1974. It deals with duties of employer and employee with regard to health and safety. Employee should report accident, spillage. It is a statutory requirement. COSHH - Control of substances hazardous to health 1988.
74.
Give one advantage of using testex tape and plastic disposable W.F.T combs. It can be kept as a permanent record.
75.
State the principles of being able to use a banana gauge for taking D.F.T. readings. When using the banana gauge on ferrous metal (substrate) coated with non-ferrous coatings, then the D.F.T can be measured with banana gauge. It works on the principle of magnetism.
76.
Briefly describe the various paint application methods and its limitations. Page 58 of 85
Brush application: Brush painting is said to achieve superior wetting and is the only acceptable way to apply some anti corrosive primers. Brush marks leads to areas of low film build. Use of brush is slow, and time consuming. Rubbing action of a brush can be and additional aid to good adhesion. A brush of suitable size for the work in hand should always be selected, as a small brush on a large area makes it difficult to apply an even coating and slows down the rate of working, whilst using a large brush on a narrow area makes accurate working impossible. Rollers: Quality of roller application depends partly on the covering or sleeve of the roller and partly on how conscientious the applicator is. It is not suited for anti-corrosive and anti-fouling paints. Dip-coatings: Paint must have a fast drying time. The paint in the dipping tank must be stirred continuously as the viscosity of the paint is important. Rapid withdrawal from the dip tank can cause too thin a coating. Powder Coating - Fluid bed & Electrostatic Technique. A fluid bed is one in which a mass of broken up solid is kept in a state of agitation by mechanical or other means. Fluid beds for coating purposes consist of finely powdered pigmented resinous solids through which air is blown to keep the particles in motion. Electrostatic Spray: Paint is sprayed from a pressure feed tank through a fluid hose to the gun in the usual way. At the same time paint is given a -ve electrical charge. As the electrically charged paint leaves the gun, it atomizes and each particle is attracted to any earthen object, in its path i.e. the article being sprayed. Conventional spraying: This involves using a compressed air to both atomize the paint and to convey it to the substrate. In high pressure, the painting is stored in a pressured container from which large quantities can be delivered quickly. Airless spraying: Paint supplied by a hydraulic pump is forced at high pressure through a narrow orifice in a tungsten carbide nozzle. The pressure is such that the paint is atomized and carried to the substrate by its own momentum.
Page 59 of 85
1. PAINT / PAINTING INSPECTION - PAPER 1 B-gas Grade - 1 1.
Describe the following terms a) Splash zone b) Jacket c) Caisson Splash zone: 2.5 mt + 12 mt above the L.A.T. Jacket: Welded support frame of the platform tubular. Caisson: Open ended pipe that runs from topsides to the sea bottom. Has pumps and filters to take waste away.
2.
Which statutory instrument document relates to safety for offshore? SI - 1091. The offshore safety regulation 1976.
3.
List the safety measures required for over the side working in descending order of preference if scaffolding is not practicable. 3 Rail barrier Safety net Safety belt line Rescue boat and radio Full life jacket.
4.
Who is ultimately responsible for safety at offshore? Page 60 of 85
O.I.M - Off shore installation manager. 5.
Name four decks on a platform. Heli-deck Spider-deck Drilling-deck Cellar-deck.
6.
Name three major dangers, which exist when working offshore? Falling overboard, fire explosion and adverse weather (gales & storms)
7.
Name three methods of keeping a platform in a fixed position. Piling, semi submersible, material support, jacket legs, sea tank.
8.
9.
How are escape routes identified on an offshore platform? By arrows cut out of reflecting strips and fixed on top of the non-skid designated deck. Deck coating: 100-mm - Prime route, 50-mm - Sea route. What precautions must be observed when boarding and travelling in helicopters? All as described in the C.A.A. course which you must attend before travelling offshore.
10.
How often is medical treatment required for personnel working offshore? From the ages 30 - 39, every 3 years. From the ages 40 - 50, every 2 years. From the age 50 and above - yearly.
11.
List the essential items of clothing and equipment for an offshore painting inspector. Riggers boots, safety helmet, 100% cotton overalls, safety glasses, and life belt jacket and weather and paint instruments.
12.
What is breaker capsule? A completely enclosed safety and rescue boat for escape. Page 61 of 85
13.
Are painters permitted to erect scaffolding? No. It must be the work of a qualified scaffolder holding a C.I.T.B card. Painters paint only, but they can refuse to work on the scaffold if they are not sure of its safety for their job or personnel safety.
14.
Describe the meaning of H - 120 in relation to fire protection. H - stands for hydrocarbon. 120 stands for the time in minutes, that the fire protection system is designed to stop the passage of flames, smoke, to allow personnel to escape to safety.
15.
On what parts of an offshore structure are anti-foulant coatings applied? Name two common types of toxic material used in anti-foulants. Anti-foulant coatings are applied on the submerged and splash zone areas of the sea. Organic tin, cupros-oxide are two common types of toxic materials used in antifoulants. Mercury, arsenic and lead are not used.
16.
Name the two types of fireproof coatings. say which type is used mostly and describe how it works. Cementious and Intumescent are two types of fireproof coatings. Intumescent coatings are the preferred ones for offshore coating in hydrocarbon fires and cellulosic fires. They swell upto many times their thickness thus delaying the fire spread upto 200%
17.
What application requirements are specified for the spray application of paint to large surface areas? The manufacturer's specification sheets (data) specify the application requirements. Large fan sprays, vertical and horizontal parallel passes, non-organic paintings should overlap by 50%.
18.
For which coated areas is 100% holiday detection required? Seabed and splash zone to the cellar deck.
19.
a) Finish blast cleaning may be not carried out, when? When the dew point is not above 3°c above the steel temperature. b) Can blast cleaning be carried out at night? Yes, but must be finished in the daylight. Page 62 of 85
c) What standard is specified for power tool cleaning. ST-3. d) Power tool cleaning must overlap existing coating by atleast - 50mm. e) Coatings must not be applied when surfaces are less than - 3°c above DP, when RH % is above 85%. 20.
a) Coatings must not come within - 50mm of weld preparation. b) Is it permitted to spray paint from a BOSUNS chair - no, but brush application is acceptable. c) What distance and angle should a spray gun is held from the surface? Distance - 18", 450 - 600mm, at an angle of 90°.
PAPER 2. PAINTING GRADE 1 (B-gas) - OFFSHORE.
1.
What does a Radioman fulfill? He is a look out person. He keeps in three way contact during and over the site operation. He should also be on hand where the people are working in vessels or enclosed space in offshore. To summon help in case of accident in the radio operator's office.
2.
What document does a paint inspector need to know to work on offshore? The offshore safety regulation 1976 SI - 1091. Page 63 of 85
Medical certificate, passport, lifeboat survival training, B-gas approval. 3.
Give a list of duties an N.R.P. might perform. Incharge of designated areas of the platform. Issuing hot and cold permits. Receiving completed work permits, checking work carried out on permit. Area authority O.I.M.
4.
Why are areas encapsulated and give ways in which this could be done? To protect instruments and fire protection equipment's during blasting, cleaning and painting operations. During maintenance work, completely cover the areas in plastic sheets or mask off, for climatic or safety reasons.
5.
What possible problems would an inspector meet at offshore? a) b) c) d)
6.
High change in the weather conditions. Rapid change of tidal conditions. Movements of helicopters and boats. Access to work during drying times.
How would an inspector communicate with his boss back to back? Usually meet for half an hour or so at the shift change, if there was a serious problem to explain or leave a hand written report for him in his logbook.
7.
How would you determine that a contractor's plant and equipment was safe to use? All plant equipment used on offshore must have calibration certificates, maintenance record details dated and signed by approved agent.
8.
Why is masking carried out and what areas might need this? To protect sensitive equipment (electrical and instruments) in particular from damage during maintenance operation. Also the pipe work and colour coded sections has to be masked off before being sprayed by different paints to protect areas that are not painted.
9.
Give reasons why the submerged zone is not always coated.
Page 64 of 85
Submerged zone is difficult to paint because of its position. Also because of water and lack of oxygen present, the rate of corrosion is not so serious and also sacrificial anodes are used. 10.
What are the two ways in which galvanized surfaces can be prepared before painting? The two ways are, 1) Sweep blast and etch primer 2) Power tool with mordant wash.
11.
What is COSHH and what dos it deal with? Control of substances hazardous to health regulation 1988. It deals with environmental safety in the work place, solvents, sands, dust except lead paints, radiation explosives, own regulations.
12.
Other than temperatures and RH what could stop blast cleaning from being carried out? Where different types of cleaning is needed usually power or hand cleaning due to maintenance or other type of problems-weather conditions, operation or production.
13.
What are the two types of test, which are carried out for cathodic disbondment? Static test for submerged coatings. Cyclic test for splash zone coat.
14.
What is the title of CPC - 155 and which is the current issue? Title -175C, Paint council-1998 Issue 2, CPC - company practices for paint.
15.
What do the following refer to? AL BS CS Cu HSE LAT MIO NI SI
-
Aluminium British standard Carbon steel copper Health safety environment Lowest astronomical tide Micaceous iron oxide Nickel Statutory instrument Page 65 of 85
SS ZN 16.
-
Stainless steel Zinc.
What are reduced V.O.C. coatings? For V.O.C. coatings pigments carry more water emulsion binders. It is water based. Solvents are greatly reduced.
17.
What information must a paint manufacturer print on a paint tin? Method of use (brush or spray), type of paint, production date, shelf life, confirmative with B-gas specification are the things that should be printed on a paint tin.
18.
What results must be published by a paint manufacturer regarding the qualities of his paints?
The following are the results that have to be published by the manufacturer. Composition (pigment, binder & volatiles) Manufacturer's name Product description Volume of solids Viscosity Opacity Covering power (gloss) Abrasion resistant Impact resistant Density and adhesion. 19.
What information does the paint manufacturer have to supply to the contractor? Material data sheets, health and safety information regarding the products.
20.
Who is responsible for choosing a paint system for use on a particular job? The contractor using range of approved B-gas paint systems.
21.
What are the two BS codes used in connection with colour schedules? BS 4800 and BS 5252.
22.
What must happen to any weld splatter which was not removed during the fabrication process? It must be ground of flush by the best mechanical means. Page 66 of 85
23.
What shall surfaces be free from before painting? Surfaces shall be free from dust, moisture, oil and grease and other contaminants.
24.
How shall heavy or metallic pigment be kept in suspension when applying paint? Automatic stirrer, air or power operated in the paint pot during application and constantly in motion can keep it in suspension.
25.
What shall drying/curing periods comply with painting? It shall comply with manufacturer's data sheets.
26.
What is a stripe coat? It is a brush-applied coat to the weld areas to make sure that the proper D.F.T is attained. It is an extra coat to welds and edges.
27.
Describe how test panels are prepared and painted and what is their purpose. Test panels are blasted to Sa 3 standard, then according to test required instructions. For rust grade after blasting it is left in the atmosphere for 2 - 3 months. Test panels are then dipped in seawater. Dry for 2 or 3 minutes, then coat.
28.
What type of components comes under identification marking of paints? Reflective plastic strips.
29.
How do you decide what grade of preparation needs to be carried out? Depends on the design life.
30.
When wet blasting, what will you to areas likely to be affected by water and abrasive contamination? Securely mask off.
31.
When can a brush be used to apply paint for offshore structures? In repair maintenance when it is impracticable to use airless.
32.
If B-gas decide to inspect work being carried out what must not happen? Page 67 of 85
All other work must be stopped. 33.
When are destructive tests usually carried out? If there is a problem in maintenance paint or test panels.
34.
Who advises of the voltage to be used when holiday detection tests are being carried out? As per specification - 5 volts per micron or as per the engineer of the paint manufacturer.
35.
What is the procedure for rectifying coatings, which have an inadequate thickness? Rub down with sandpaper and blow them down. Apply mist coat to bring up the required D.F.T.
36.
What document should be used as a reference for the procedures to remove contamination from a surface? BS 7079.
37.
What type of risk assessments are looked for when undertaking a cleaning and painting procedure? 1. 2. 3. 4.
38.
How safe is the area. Danger - Health and safety. COSHH. Need of climate conditions and lighting.
Who is responsible for the training of personnel to work offshore? The contractor must arrange for his people to be trained.
39.
What are the requirements for 'overside' working? 3 bar rail, scaffolds, board toes, safety net, safety line, life belt, boat with radio contact.
40.
What things might you note when carrying out visual inspection for a) Preparation procedures: Correct procedure, condition of substrate i.e. free from contaminants, scaffolding requirement, blasting equipment's, checks for air Page 68 of 85
purity, observation of rogue peaks i.e. uneven amplitude, high points should be abraded. b) Painting procedures: Correct usage of paints as required by the specification, colours, visual check for any skinning or jelling of paint, whether tin is sealed before first use, shelf life, pot life, paint mixing ratios and appropriate thinner quantity added to the paint, visual observation of the paint system for any paint defects. c) Cleaning up of area of operations: Removal of paint debris and disposed as per local rules, don't fire.
Page 69 of 85
PAPER - 3. (B-gas, Painting Grade 1) COATINGS
1.
Give as much information as you can for the following surfaces preparation and paint systems. a) Internal surfaces of potable water tanks: H.S.C. should be coated to Sa 3. Blast media must be removed. Industrial vacuum cleaners are very good and quick. All welds must be strip coated. Apply 3-coat system (as recommended by data sheets). It must be 100% holiday detected by wet sponge method. It should have 300 microns d.f.t high build epoxy. b) Materials operating at elevated temperature: It should be blast cleaned to Sa 3. It must have a proven track record like inorganic zinc silicate and modified silicone sealers, poly siloxene. c) Coating designed for living quarters and how they work: Intumescent to 200°c. They swell up to many times there own thickness and the wire mesh screen holds them together as the coating turns to a carbonaceous char. Also they should be rated A.60 or H.120 d) Splash zone coatings: It should be blasted to Sa 2 1/2. As per manufacture specification, mostly coal tar epoxy or glass flakes are used. It must be 100% holiday detected, sweep blasted and then tie coat to be carried out. e) Copper, nickel, aluminium, and other nonferrous surfaces: Most nonferrous metals are usually not coated except for cosmetic and colour coding. Aluminium is used in the composition of some coating, and in sacrificial anodes. Hand emery (brade), white spirit for cleaning, apply acrylic urethane coat upto 70 microns d.f.t. f) Helidecks: Heli decks are blasted and coated using non spark and non metal abrasives and paints. Alum surface preparation Sa 2 1/2 like appearance. Maintenance by wire brushing, zinc rich epoxy, 2 pack epoxy, tie coat, baux epoxy (polyamide) g) Instruments / electrical equipment's: It should be masked off to protect them from the preparation and painting operations. Surface preparation to St 3, hand abrade, acrylic coat to 200 microns d.f.t. h) Submerged zone: It can be painted using paint system that can be cured under water. They may be unpainted, as this area is a slow corrosion area. Due to low oxygen , coal tar epoxy as that of splash zone can be applied. Page 70 of 85
i) Top side maintenance: Operations to be carried out by power cleaning to St 3. Apply alum epoxy primer. Mostly hand cleaning preparations only carried out. Brush applied coating with urethane acrylic upto 70 microns d.f.t. j) Galvanized steel structures: Sweep blast and apply. Power wire brush - apply two damaged areas, epoxy mastic chlorinated resin. k) Pipeline riser in the splash zone: It should be coated same as all other steel work in that zone. l) Deck coatings: It should be non-slip escape system. Over the top coating screened coat and seeler should be applied. 3-pack copolymer is applied 2-4mm
PAPER - 4. PAINTING GRADE 1 (B-gas)
1.
What do you understand by the following terms? a) L.A.T: Lowest astronomical tide. b) Elevation: Side view of a platform according to l.a.t. c) Splash zone: It has a dimensioned area. No other deck has this. It is -2.5 Mts. to +12 Mts. of the l.a.t.
2.
Which statutory instrument document relates to safety at offshore? S1 - 1019
3.
What are the requirements for inspecting scaffolding used at offshore? It must be inspected by competent qualified personnel only, every seven days and always after adverse weather.
4.
How is safe scaffolding identified? By the colour, green tag.
5.
List the safety measures required for over the side working in descending order of preference if scaffolding is not practicable. Safety nets, safety belt line and life jacket.
6.
Name two types of permit to work and give an example on each. Hot: All power driven tools, blasting and spraying equipments. Cold: Working at heights, rubbing down, house keeping. Page 71 of 85
7.
What documentation is required prior to entering a vessel at offshore? A permit may be required over and above the hot or cold ones issued by a competent person to check whether oxygen is in excess of 20%. A stand by person at the entry, K9 sniffer to determine explosion levels, M.E.L, O.E.L. are also required before entering a vessel.
8.
Who is ultimately responsible for safety at offshore? O.I.M.I.O
9.
Are drilling muds acidic or alkaline? Alkaline. Name three decks, which are main at offshore platforms.
10.
Splash deck, atmospheric deck and topsides deck. 11.
Describe the following areas on an offshore platform. Jacket: It is the support structure of a platform. Caissons: Open pipe work with pumps and filters. Conductor: Joins riser pipelines to topside pipe work.
12.
What should you do immediately after arriving on an offshore platform? Book in and attend safety briefing.
13.
How are offshore platforms identified? It is identified by operator's name, name of oil or gas field. Letter designation sign is black and yellow in colour.
14.
List three safety considerations for all offshore workers working on a production platform.
15.
Who issues work permits? Nominated responsible person. Page 72 of 85
16.
For how long must a person work offshore before offshore survival training becomes compulsory? A visitor who visits a platform does not stay overnight, for not more than four times a year and must register his visit every time on the rig.
17.
How often is a medical check required for personnel working at offshore? Below 40 years - 3 years Between 40 - 50 years - 2 years Over 50 years - yearly.
18.
How are escape routes identified on an offshore platform?
19.
By reflective strips, by arrows over the specified deck coat, primary routes -100Mts, secondary routes - 50 Mts. Name three methods of keeping a platform in fixed position? Steel piling, Matt support and sea tanker.
20.
What precautions should be observed when boarding and travelling in helicopter? As recommended by the C.A.A.
21.
List the essential items of equipment and clothing for an offshore painting inspector 100% cotton overalls, rigger boots, safety helmets, safety glasses, gloves, life jacket and safety suit are the equipment's required for the inspector.
22.
Eddy current paint thickness metres and electrical thermometrs may not be allowed at offshore, why? Possibility of spark from batteries is the reason for not allowing the above said meters.
23.
Explain the following term's platform, module and jacket. Platform: Structures from where operations, drilling and production start at offshore. Module: Large boxes which contain accommodation and compressor etc., Jacket: It is the support structure of a platform.
24.
Which documents are you required to have before boarding a helicopter to go Page 73 of 85
offshore? C.A.A. course certificate, boarding card, medical certificate, safety survival certificate and passport. 25.
What is the abbreviation for O.I.M? Offshore installation manager.
26.
What is the station bill? It is the notice board located outside the radio officer's office.
27.
What must be worn below the cellar deck? A survival suit and a full life jacket.
28.
In an emergency what is the difference between an intermittent siren and a flashing light, and a continuous siren and a red light? Intermittent siren and flashlight prepare to abandon rig, whereas continuous siren and red light indicates to abandon rig.
29.
What is brucker capsule? It is an escape vessel. It is a fully covered lifeboat.
30.
What are the problems associated with the preparation and painting of helidecks and, splash and tidal zones? Problems associated are weather conditions, limited time factors, air traffic and tide levels.
31.
When would helidecks, tidal and splash zones are painted? They will be painted when there is low tides and when there is no helicopter activity and in day light working only.
32.
What considerations should be given to scaffolding in the splash zone? Removal of boards after work as the tides will wash away loose boards. It should be checked regularly. Page 74 of 85
33.
Why are rigger boots worn at offshore? It is resistant to oils and kicked of quickly.
34.
Why are nylon overalls usually prohibited? Due to static electricity which can occur. They may also melt.
35.
Describe three methods for fixing a platform in position. Steel piling, matt support and sea tanks are the three methods.
36.
What is derrick lay barge? It is a vessel for laying offshore oil and gas pipelines and setting topsides, risers and for piling of jackets.
37.
Where on platform is the spider deck? It is the lowest deck. Splash zone walkway between braces and conductors.
38.
Who is a standby man or radioman? He is a person used in the vessel or near enclosed spaces in cases of emergency. He must be always present in person and on the look out. Radioman - he is a 3 way contact, himself, work team and standby boat.
39.
How is a paint application equipment earthed for use at offshore? Blast cleaning and spray equipment shall be continuously electrically bonded from nozzle to the surface being painted and backward from nozzle to the compressor, which shall be earthed.
40
What is the minimum length of nozzle for wet blasting at offshore? One metre long.
41.
Name three types of foulant? Animals, plant and micro-organism.
42.
Describe the meaning of H-120 in relation to fire protection. Page 75 of 85
H - Hydrocarbon and 120 minutes is the time for the fire proof, which is required to protect you. 43.
What is HP / A of a structural member? It is the ratio of the heated premier of the steel to its cross-sectional area.
44.
Name the two major types of fireproof coatings. 1. Cementious 2. Intumesceen Intumescent.
45.
Describe a typical method used to keep a very thick fire proof coating adhered on to a steel substrate. A typical method is by the use of wire netting (reinforced), pinned to the substrate by welding.
46.
47.
Name four types of anti-fouling coatings and briefly describe how they work. 1. Soluble matrix type: Water-soluble binder, release of resins. 2. Contact insoluble matrix type: Insoluble binder, release of cuprous oxide. 3. Diffusion type: Chlorinated rubber or vinyl binder releases organic solvents and diffuses out. 4. Wash off or self polish type: Copolymerised acrylic binder. Erosion washes off. It is used in offshore structures. On what parts of an offshore structure are anti-foulants applied? Sub and splash zone legs and upto eight metres of the L.A.T.
48.
Name two common types of toxic material used in anti-foulants. Cuprous oxide, organotin, mercury arsenic - restricted use.
49.
Name four environmental factors that will govern the effective life of an anti-fouling coating. 1. 2. 3. 4.
50.
Wave speed High salinity of water Water temperature erosion High pH levels
What do you understand by an encapsulated area at offshore? The area is fully enclosed working area usually for safety or climate. Page 76 of 85
51.
What type of fire proof coating swells up when it reaches high temperature of 200°c? Intumescent.
52.
Name four considerations for selecting the thickness of a specific fire proof coating for protecting structural steel. 1. 2. 3. 4.
53.
Type of fire Duration of protection H / PA of the structural formation The critical temperature of the steel (400°c is most common)
How do cellulosic fires differ from hydrocarbon fires? Hydrocarbons are fuel by oils or gases. Cellulosic fires take longer time to reach their maximum temperature. (High thermal shock-1250°c, short time)
54.
Name five ways a fire protective coating can insulate from fire. 1. A thermally insulating layer 2. A barrier to exclude oxygen from the combustion surface 3. The formation of a heat resistant and non combust layer 4. The evolution of non combust gases or water to quench the flames 5. The removal of a fire attached outer surface to reveal a cooler surface.
55.
What type of fire proof coating is currently in favour for use at offshore? Intumescent.
56.
How are anti-fouling coatings applied? It is usually applied by airless spray.
57.
The B-gas draft specification entitled ' Specification for painting and coating of offshore structures related equipment properties and performance of paints and coatings' is the - BG / OS / PS / 1206
58.
How is the splash zone defined?
Page 77 of 85
Splash zone has a dimension in area. No other deck has this dimension. It is -2.5 Mts. to +12 Mts. of the L.A.T. 59.
Are copper nickel surfaces painted? If so discuss the reasons for painting them. Yes, copper nickel surfaces are painted, for colour coding and cosmetic coating on pipe work.
60.
Whose responsibility is it to provide up to date data and product safety sheets for the paints / coatings and solvents used on the contract? Coating manufacturers.
61.
What is the minimum surface preparation standard for internal coating on caissons? SA 3.
62.
What is the amplitude range required for blast cleaned surfaces? 50 - 75 microns.
63.
For what distance must surface preparation overlap onto adjacent painted areas. 50 mm.
64.
What surface preparation method is used within one hour of abrasive wet blasting? Primer coated, pressure washed with fresh potable water.
65.
Is it permissible to use inhibitors for wet blasting? No. They can leave a deposit on the surface.
66.
What is the temperature, dew point and relative humidity restriction for finish blasting? Dew point should be above 3°c above the substrate temperature. RH should not be higher than 85%.
67.
Is blast cleaning permitted at night? Yes, but the job must be finished in morning daylight. Page 78 of 85
68.
What type of cleaning is normally specified for repair and maintenance work and to what grade? Wire brushing to St 3.
69.
Are power impact tools permitted? In special occasions by agreement by B-gas engineer. When other methods are not suitable follow by brushing to St3.
70.
Is it permissible to paint with non-moisture tolerance system if the air temperature is 13°c, the metal surface is 12°c and the dew point is 9°c? No. Dew point is less than 3°c of the metal substrate. It should be over three degrees. RH % is not known. Manufacturer recommendations are to be followed.
71.
Is it permissible to apply paints from a single Bosuns chair? Yes. Not to be spray applied. Brush application only is allowed.
72.
What application requirements are specified for the spray application of paint to large surface area? By airless spray following manufacturers instructions. Uniform parallel passes have to be followed.
73.
Name six areas on the offshore structure that must have coatings applied -BS729. Gratings, ladders, cages, handrails, standard walkways, kick plates and duct work.
74.
75.
Can stainless steel surfaces be painted? If so discuss the reasons for painting them. Yes, they can be painted, if the area is under insulation to prevent chlorideinstigated corrosion and for protection from heat. Which procedure would take precedence if there is a conflict between the project specification and the 12 - 06 / A. 12 - 06 / B, project specification takes precedence.
76.
Does the B-gas inspector has the right to check scaffolding? Page 79 of 85
Yes, but cannot approve. 77.
Can authorization for over coating be given verbally by the B-gas inspector? Yes, but has to put it in writing later.
78.
How are painted surfaces, damaged to bare steel during transistor installation, prepared prior to repair? Preparations prior to repair are, repair it to original system. Extend 50 mm onto sound coat i.e. use same blast standard, prime intermediate and topcoats to same D.F.T's.
79.
How are amplitudes of blasted surfaces checked / measured? By using testex tape & micrometer, by profile gauge, surface needle gauge.
80.
How are D.F.T's measured? They are measured with an elcometer type, dry film gauge called magnetic banana gauge. Except for M.I.O. where W.F.T. to calculate D.F.T. is Vs x WFT IN
81.
For which coatings is 100% holiday detection specified? For all coatings from below cellar to seabed, coal tar epoxy, glass flake epoxy and poly siloxane.
82.
How are adhesion tests carried out? By X - cut, cross hatch or dolly test.
83.
How many coats of anti-fouling paint are applied to specified areas? Three to four coats after tie-coat.
84.
What paint / coating system is specified for splash zones and to what thickness? Coal tar epoxy - 200 microns, epoxy primer - 30 microns, total 630 - microns. Glass flake epoxy - 2 x 250 microns, epoxy primer - 30 microns, total - 530 microns. Discuss the full system from dry blast preparation to find coat, for coating the underside of a cellular deck onshore.
85.
Page 80 of 85
Blast clean to Sa 2 1/2, zinc rich epoxy primer - tie coat, then 3 coats of high build epoxy. 86.
What type of primer is to be used on the underside of a cellar deck if wire brushing is used instead of blasting? High solids aluminium epoxy.
87.
What coating system is specified for conductors? Coal tar epoxy - same coating as in the zone.
88.
What coating system s specified for internally coating caissons? Sa 3 - blasting glass flake, epoxy polyester - 2 mm.
89.
How are escape routes to be identified? By arrows made from reflective strips.
90.
For what application is heavy-duty screed specified? Heavy duty deck areas, major wear, non-skid areas, copolymers screed, escape route, helideck, skid deck and drill deck.
91.
What finish coat is specified for the topside zone and why? Ultraviolet, urethane acrylics are the finish coats specified. It has good resistance, gloss retention, easily cleared and strong binder impermeable.
92.
Is the painting of galvanized surfaces specified? Discuss. Yes. Because the hot dip surfaces must be in compliance with BS 729 also there are systems for O/coating galvanized items and the repair of damaged galvanized areas by epoxy mastics. Colour code to be given.
93.
What type of surface preparation is specified if it is necessary to coat Cu-Ni or Ni alloys? The surface has to be degreased, lightly abraded and washed with fresh water and dried. Coat with urethane or epoxy etch primer only on aluminium. Do not blast clean. Page 81 of 85
94.
For what application may zinc silicate with a sealer be specified? Atmospheres at high elevated temperature 121°c to 350°c, flare stacks, turbine exhausts and as per manufacturer's specification.
95.
How are damaged coatings prepared and repaired when they have not exposed the metal surface? Damaged coatings should be suitably cleaned and chamfered to ensure patch coating is continuous. The build up is to be upto the specified thickness and systems.
96.
Coating must not come within fifty mm for preparing welds.
97.
What is insulation used for? It is used for conserving heat, cold, for personnel protection, frost and anticondensation.
98.
Name the three general types of materials used in an insulation system. Calcium silicate, rock wool, expanded perlite and modified slag wool.
99.
Which B-gas specification applies to acoustic cladding? BGC - PS - PW C1
100.
What is the aim of acoustic cladding? Its main aim is to cut down noise level by 10 - 20 decibels.
101.
What is the typical thickness for acoustic cladding? 50 - 100 mm.
102.
What is the metal jacket composed for acoustic cladding? Aluminium alloy, galvanized mild steel.
103.
What is the insulation banding made from? Metallic and non-metallic banding must be made from the same material as that of the jacket.
104.
What are the requirements for mastic sealant and rubber or neoprene bedding Page 82 of 85
strips? It must be suitable for use at temperature between -20°c to +50°c and in rare occasion upto 80°c. 105.
What are nuts, bolts and washers made from? They are made of either stainless steel or zinc coated mild steel.
106.
What are the four basic operations for applying acoustic cladding? 1. 2. 3. 4.
107.
Preparation Insulation and fixing Repeat insulation and fixing if required Metal cladding and fixing.
What is the minimum overlap for the metal jacket on to itself? 25 mm.
108.
What action is taken when cladding reaches a branch pipe? A clearance of 6 mm is maintained and mastic filled.
109.
Which specification applies to thermal insulation? BGC - PS - PW C2.
110.
What is vermiculite? Vermiculite is a loose granular fill type of insulation.
111.
Name six materials that could be used for thermal insulation. Foamed glass, rock wool, modified slag wool, expanded perlite, calcium silicate and phenolic foam (not to be used in buildings).
112.
What total thickness could be specified for thermal insulation? Between 50 - 100 mm and in certain case upto 400 mm.
113.
For what application are vapour seals used? It is used for cryogenic application. Page 83 of 85
114.
What type of metal cladding is used for thermal insulation? Either aluminium alloy or galvanized mild steel sheeting where greater rigidity is needed.
115.
What is an alternative to metal cladding for thermal insulation?
116.
Self-setting cement, glass cloth and hard setting composition. Name six binding materials used for thermal insulation. Wire netting, binding wire, self taping screws, binding tape, nuts and bolts and adhesive joint sealant.
117.
List four basic operations for applying insulation for heat conservation and protection? Preparations repeat insulation and fixing if required, metal cladding and fixing or self-setting or hard setting cement.
118.
List the five basic operations for applying insulation for cold conservation and cryogenic service. Stagger insulation, first layer of vapour sealing compound, scrum cloth embedded in first sealing, second layer of seal then cladding and banding seal, vapour seal and metal cladding are the five basic operations.
119.
How frequently is binding wire used when insulating pipe works? At 150 mm intervals.
120.
How frequently are fixing bands used on equipment? 300 mm.
121.
How frequently are fixing bands used on metal cladding? 450 mm.
122.
What is the minimum metal cladding overlap on pipes greater than 40-mm diameter? 75 mm.
123.
Where is anti-abrasive compound used? Page 84 of 85
For fixing material. 124.
What is the temperature range applicable to the B-gas specification for thermal insulation? - 200°c to + 1000°c
Page 85 of 85
