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PAGE 18
BGas Painting Inspection Grade 2 / 3
1. Name the different ways of surface Preparation?
Dry Abrasive Blast Cleaning
Water Blasting
Hand and Power Tool Cleaning
Flame Cleaning
Pickling ( Chemical Cleaning )
Vapour Degreasing
Weathering
2. What equipment are needed for Blasting?Compressor
Blast Pot - for abrasives
Vapour Traps ( knock out pot )
Hose
Nozzles
Safety to 1GE SR 21 Maintain operating pressure at 100 psi.
Hose should be carbon impregnated.
External couplings.
dead mans handle should be under direct control of the
operator
should be kept as straight and as short as possible to avoid
kinks, and
blowouts.
PPE (leather aprons and gloves, boots and ear protectors,
including
direct air fed helmet, with adequate visors.
3. What speed do the particles exit a Venturi blast nozzle?450
mph ( 720 kmph )
4. What speed do the particles exit a Straight bore nozzle?
220 mph
5. Describe how you would carry out a check on air pressure of a
blasting?Alert the Operator
Shutdown the abrasive
Insert the Hypodermic needle gauge into the reinforced hose as
possible to the nozzle at 45
toward the nozzle Take direct reading from the gauge
6. What are the advantages and disadvantage of Venturi?
Venturi
Advantages
DisadvantageVery high speed (450mph)
Safety
Faster operation
Maintenance
Large area coverage
less accurate
Large blast pattern
Suitable for large area
7. What are the advantages and disadvantage of Straight
bore?
Straight bore
Advantages
DisadvantageGreater accuracy
Low speed ( 220 mph )
less area coverage
8. What is used to determine the presence of Hygroscopic salts,
in industrial situation?Potassium Ferricyanide test will determine
the presence of Hygroscopic salts, in industrial situation?
9. Which test is carried out for soluble salts in a marine
environment?
Silver Nitrate Test is carried out for soluble salts in a marine
environment
10. Give another common name for Copper slag?Iron Sillica
11. How many photographs of Flame clean standards are in BS
7079?There are 4 photographs of Flame clean standards are in BS
7079
12. Name the system for pickling followed by passivation?Duplex
process system is pickling followed by passivation using phosphoric
or chromic acid
13. Describe how rouge peaks are caused?Girt, which cuts the
profile.
14. How many times can garnet be used for site blasting? Why?One
time only, because after blasting the garnet fall on the ground
& it gets contaminated. And we cant use contaminated abrasives
for blasting.
15. List the equipment required for an abrasive blasting
operations site?A compressor
A pot containing the abrasives.
Vapour Traps for oil and water (knock out pots).
A hose, usually carbon impregnated to discharge static
electric
External couplings
A nozzle
A dead mans handle for operator safety.
16. When power brushes are authorised for use BGas/Transco site,
the wire is made from which non-sparking producing materials
?Phosphor bronze and Beryllium bronze
17. What are the advantages and disadvantages of wet blasting
?
Wet Blasting
Advantages
DisadvantageUseful for removal of toxic materials
Need large amount of water
Environmentally friendly
Disposal of resulting slurry
Spark free
Does not cut profile
Ideal for removal of soluble salts & chloridesSubstrate
inhibitors to be added
18. What profile range can be measured using coarse Testex?20 50
um profile range can be measured using coarse Testex
19. What profile range can be measured using X coarse Testex?37
115 um profile range can be measured using X coarse Testex
20. What are the two principles of the theory of Adhesion?
Molecular Interference ( PHYSICAL )
Molecular Attraction ( CHEMICAL )
21. Briefly Describe the mechanisms of the two theories of
adhesion.Molecular Interference : The surface is rough & uneven
the paint wets & lock into profile
analogy Velcro, PHYSICAL
Molecular Attraction : Negatively charged particles attracts to
positive areas& vice versa.
Analogy magnet ( also called as Ionic Bonding ). CHEMICAL
22. How many microns are in 1thou?1thou = 25.4 um
23. Give three different names for the cross section of a
blast.Anchor pattern.Surface profile
Key
Peak to trough height
Amplitude
24. What is the most common cause of flash rusting on a blasted
substrate?Rouge peaks
25. What would be considered to be an ideal shot grit mix?What
is the purpose of mixing shot and grit?To get uniform profile,
because grit cuts the profile & shot controls the rouge
peaks.
26. Which abrasive would have the effect of work hardening a
substrate?Metallic Shot
27. Name three methods of measuring or assessing a profile.?1-
By using surface profile Needle Gauge
2 - Using Testex tape & Dial micrometer
3 - Comparators
28. What is the most common cause of rogue peaks on a
substrate?Grit, which cuts the profile
29. In what situation would it be better to use steel grit in
preference to copper slag abrasives?Copper slag can be used only
once, because it shatters into small pieces on impact. So Grit it
can be used many times
30. If cracks or laminations are found on a substrate after
blasting what steps should be taken?Cracks or laminations must be
referred to the Engineer
31. Using comparators to ISO 8503, what are the three main
profile assessments?1- Fine
2 - Medium
3 - Coarse
32. What are the other two assessments when the above three are
not appropriate?1 - Finer than Fine
2 - Coarser than Coarse
33. What would be size of copper slag needed to give a profile
of 50 to 75 um?G 16 would be size of copper slag needed to give a
profile of 50 to 75 um34. What is the title of the BS 7079?The
title of the BS 7079 is Preparation of the Steel substrates before
application of paint
35. Describe the four Blasting grade ?Sa1 : Light Blast
CleaningSa2 : Thorough Blast Cleaning.
Sa2 : Very Thorough Blast Cleaning.Sa3 : Blast Cleaning to
Visually Clean Steel.
36. What are the four characteristics of an abrasive?Size
Shape
Hardness
Density
37. Why are blast hoses carbon impregnated?To discharge static
electricity
38. Name the gauge used for measuring pressure at the blast
nozzle?Hypodermic Needle Gauge
39. Name four advantages of centrifugal blasting over open
blasting.1 - Operator Safety
2 - System is more productive
3 - Quality can be adjusted
4 - Efficient use of Abrasives
40. According to BS 7079 is it possible to blast clean to an A
Sa1?Not Possible ( According to BS 7079 is it possible to blast
clean to an A Sa1? )
41. Is there any difference between an A Sa1 and B Sa1?A Sa1 Not
achievable
B Sa1 Can be achievable
42. Could you tell the difference between rust grades A and B
blasted to Sa3?No Difference
43. Could you tell the difference between rust grades C and D
blasted to Sa3?C Slight pitting
D Heavily Pitted
44. What would be a typical speed of abrasives leaving a wheel
abrator?220 mph
45. What is considered to be the most efficient blasting
pressure?100 psi is the most efficient blasting pressure
46. What is meant by the term burnishing?Burnishing means
Polishing
47. What would be the equivalent to St2 in the Sa grades?St2 is
equivalent to Sa 2 grades
48. What is the neutral figure on the pH scale?7 is the neutral
figure on the pH scale
49. How is pH measured?pH measured using indicator strips
50. Why are inhibitors sometimes added to water in wet
blasting?Sometimes inhibitors are added to water in wet blasting,
because to retard corrosion
51. Name two typical areas where needle guns might not be
used?Rivets & bolts, Weld end preparations
52. What is the Duplex Process of surface preparation?
Duplex process system is pickling followed by passivation using
Phosphoric acid or chromic acid.
53. Why is it considered essential to remove millscale prior to
painting?
Millscale being cathodic to steel and more noble than steel.
54. Which British standard would be used in determining the size
of copper slag abrasive?BS 410 (specification for test sieves)
55. Which British standard would be used in determining the size
of metallic abrasive?
BS 410 (specification for test sieves?
56. Why it is important to have a good surface
preparation?Because good surface preparation provide area available
for adhesion and for coating life.
57. What is meant by the term grade, relating to a blast
finish?
Degree of cleanliness, Degree of roughness (surface profile)
58. What are the main factor governing the grade of a blast
finish?Time, Velocity of particles.
59. Name four advantages of centrifugal blasting over open
blasting?60. Operator safety, more productive, efficient use of
abrasives, quality obtained.61. which solvent are commonly used for
degreasing?Xylene.
62. How is abrasive cleansed in a wheel abrator system?
By Air wash separator.
63. What would be the typical temperature and concentration of
sulphuric acid in the pickling process
70C, 5-10% concentrated sulphuric acid, 5-25 min.
64. Describe the Duplex Process?Clean surface by solvent
(xylene)
immerse the component is sulphuric acid 5-10% concentration,
60-70C temp, 5-25 min.
rinse with clean warm water to remove layer of soluble salts
formed.
immerse in bath of phosphoric / chromic acid 2% at 80 C temp.,
1-2 min with iron filling (0.5%)
rinse in clean water and check PH value.
65. What would be considered to be advantages of wet blasting
over dry blasting?Wet blasting removes toxic materials, more
environmentally friendly, spark free and ideal for removal of
soluble salts etc.66. Why is the phosphating or chromating of a
steel done?
It forms a rust inhibitive layer which protect the underlying
surface and increase the adhesion properties & prevent
embrittlement.67. Name a third type of paint other solvent free and
solvent borne?Powder paint.
68. Name four or more advantages of chlorinated rubber
paint?
Resistance to mould growth.
Non-flammable after solvent release.
Very high resistance to acid & alkalies
Material is non-toxic & provides a very durable film.
69. What are the three main disadvantages of chlorinated rubber
paint?Low resistance to solvent.
Low temperature tolerance, 65C maximum.
Spray application resulted in cobwebs
70. Would it be good practice to apply chlorinated rubber over
alkyd resin?No.71. What is meant by opaque?Hiding power, covering
power (opacity)
72. What is another name for an un-pigmented paint?
Varnish
73. What are the natural properties of a resin?
Brittle by nature and fast drying, mix with oil to modify some
properties.
74. What are the natural properties of an oil?
Slow drying properties, mixed with resin to modify the film
properties.
75. How does the paint using the barrier principle work?
The material form a thick impermeable layer of a high electrical
resistance.
76. How does the paint using the passivation principle
work?Chemical reaction between the paint constituents and the
substrate.
77. How does paint using cathodic protection principle
work?Bi-metallic principle by using less noble metal.
78. Give another name for solvent free two packs?
MCL - Multi compound liquid
79. Name six properties of binder?
Viscosity
Adhesion to the substrate for the expected life of coating.
Resistance to chemical attack.
Dialectric strength.
Resistance to passage of water.
Cohesive strength.
Resistance to abrasion.
80. Name three natural resin used in paints?Copals, Dammers
& Coumarones.
81. Name five natural oil used in paints?
Linseed Oil, Tung Oil, Soya Oil, Tall Oil & Safflower
Oil.
82. Name an Inorganic high temperature service binder?Ethyl
& Methyl silicate (silicone)
83. Name two pigments likely to be used for high temperature
service?
Aluminium & Carbon.
84. By what name would you call the basic unit of a
polymer?monomer (mer).
85. what is polymerization?
Joining together of a string or structure of repeated units.
86. What would be the characteristics of a short oil paints?
less than 45% oil to resin, brittle and fast drying
material.
87. What would be the characteristics of a long oil paints?
More than 60% oil to resin, slow drying properties, decorative
material.88. What is meant by the term opaque pigment?Inert
particle with excellent light scattering properties in order to
give covering power (opacity).
89. What is the typical size of a pigment particle?
1/10 micron.
90. Briefly describe the difference between saturated and
unsaturated when referring to oil or polymers?
Saturated oil are oil which cannot combine with oxygen to form a
film and unsaturated oil combine with oxygen and solidify by
polymerization to form film.91. What is the main difference between
a dye and a pigment?
Pigment used in paints must remain as solid particles within the
vehicle (solvent + binder), and not dissolve, if is dissolves it is
known as a dye.
92. Name three rust inhibitive pigments considered to be
toxic?Red lead, Calcium plumbate, coal tar & zinc chromate.
93. Name four commonly occurring minerals used as extender
pigments?
Clays, chalk, talcum & slate flour.
94. If pigments was added way below the CPVC, how would it
affect the film?
Good gloss properties but poor covering power (opacity), low
cohesive strength.99. The abbreviation CPVC means what?
Critical pigment volume concentration.
100. Why are thixotropes added to a paint formulations?
To stop settlement and allow higher film thickness.101. Describe
how a basic inhibitor works?
Causing a chemical reaction between the paint constituent and
substrates.
102. Which of the common extenders could not be used in whites
and pastels?
Slate flour (black colour).103. How would the film affected if
pigment was added above the CPVC?
Film would be porous, low in cohesive strength and adhesion.104.
Which of the rust inhibitive pigments is the most common?
Zinc phosphate.
105. Why are extenders used in paint formulation?
Provide adhesion, cohesion, film strength and durability.
106. If chromium was used as a pigment, what colour would the
paint be?
Green, yellows & Oranges.
107. Why are plasticizers added to paint?
Flexibility, reduce brittleness, compatible with binder108. Two
metals are commonly used as galvanic pigmentation, name them? Zinc
& Aluminium109. Why are driers added to oil based paint?
To allow even thorough drying of the film.
110. What is meant by the term thixotropic?
Thixotropic is an anti settling agent, a thickener, allows a
higher film thickness eg bentones & waxes.111. What is meant by
the term aggregate when referring to paint?
Degree of dispersion of fineness of grind.112. If antioxidant
was added to paint, what would it do?
Antioxidant retard the formation of a skin on the surface of the
paint eg. Methy ethyl ketoxime.
113. Give names of two plasticizers?
Castor oil, coconut oil and palm oil.114. What is meant by the
term dispersion?
A paint consist of solid particles suspended in the vehicle,
where there is no solubility, so a paint is a dispersion.
115. There are two types of dispersion, what are they?
A dispersion can be either a solid or liquid dispersed within
another liquid, where there is no solubility.
116. If paint cures by chemical reaction is it reversible or
convertible?
Convertible or non reversible.
117. What type of polymerization occurs in chemically curing
paint?
Cross linked polymers.
118. Name a paint, which dries solely by solvent
evaporation?
Chlorinated rubber, vinyls, acrylics, cellulosic and
laquers.
119. What is meant by non-convertible?
Dries solely by solvent evaporation, no chemical reaction.120.
What is meant by non-reversible?
Cures by oxidation and Chemical reaction.
121. Name four drying mechanisms?
Solvent evaporation, oxidation, chemical curing and
coalescence.
122. In a coating, which dries by solvent evaporation, what type
of polymerization occurs?
Linear polymers.123. What is another name for fineness of
grind?
Degree of dispersion.124. Which generic types of paint dry by
solvent evaporation followed by oxidation?
Alkyds, phenolics, natural oil and resins.
125. What type of polymers forms during oxidation?Cross linked
polymers.
126. What term applies to paint drying at ambient
temperatures?
Air drying.127. What is meant by the term coalescence?
Physically join together.
128. What is meant by the term pot life?
Pot life is the period of time after mixing in which the paint
must be used.
129. Name three curing agents used in epoxies?
Amides, Amines and Isocyanates.
130. Is paint a solution or dispersion, qualify?Dispersion,
pigment particle remain in as solid in a vehicle.131. What is an
exothermic reaction?
heat off from the container.132. What is meant by the term
induction period?
The length of time after mixing which the paint should stand
before use.
133. What is the difference between thermoplastic and
thermosetting?
Thermosplastic material soften with the application of heat,
therefore reversible or non convertible
Eg. Polyethylene and polypropalene
Themosetting means the material will cure with the application
of heat, therefore are convertible or non-reversible eg. Epoxy and
urethane.
134. Two other terms relate to induction period, what are
they?
Stand time and lead time.
135. Does a phenolic resin have an induction period?
No.136. Name some reversible binders?
Chlorinated rubber, vinyls, cellulose etc.
137. Is an epoxy powder paint thermoplastic or
thermosetting?
Thermosetting
138. If a coating is permeable, what does it mean?
Allow water to penetrate to the substrate.
139. What is meant by cross-linking, give two binders as an
example?
Cross linking or chemical curing is a three dimensional
polymerization process eg. Epoxy & urethane.
140. What is the opposite to exothermic?
Endothermic.
141. What is the term used for paints needing temperature in
excess of 65C to cure?
Stoving.
142. Name a material used as a driers in paint formulation?
Octoates, manganese and zirconium.143. Why would bentones or wax
be used in paint formulation?
Used as anti settling agents.
144. What generic type of paints would use anti-oxidants?
Alkyd, natural oil, resin
145. How does a single pack, epoxy ester paint dry?
Oxidation.
146. How is dew point defined?
The temperature at which water vapour in the air will
condense.
147. When using a whirling hygrometer which bulb should be read
first and why?Wet bulb, the water in the wet bulb uses heat energy
from the air to change into water vapour.
148. At what speed should the thermometer bulbs pass through the
air? 4m/sec.
149. By what other name can we refer to a whirling
hygrometer?
Aspirated hygrometer or psychrometer.
150. What is the stated criteria for acceptance, prior to
calculations on a whirling hygrometer?
On two consecutive spin the reading should be within 0.2C, wet
bulb to wet bulb and dry bulb to dry bulb.
151. Name two pieces of equipment used for taking steel
temperature?
Magnetic and digital. 152. Define viscosity?Viscosity is defined
as being a fluid resistance to flow.
153. Approximately, what is the viscosity of water?
One centi poise
154. Name the cgs and SI units of dynamic viscosity?
Poise, centi poise, dyne, N. s/m2.
155. Name three different flow cups?Zahn, Frikmar, Ford, ISO and
DIN
156. When using a flow cup which unit of viscosity would be
used?
Second.157. In ford flow cup no 4 what does 4 relate to ?
Hole size in mm.
158. Give the names of three different rotational
viscometers?
Rotothinner, Kerbs Stormer Viscometer and Flow viscometer.
159. Give a reason for performing a viscosity test on site?To
obtain the percentage of thinner used.160. Which viscometer would
not be used on thixotropic paint?
Flow viscometer.
161. Why is temperature very important when doing viscosity
tests?
Increase or decrease in temperature will effect the
viscosity.
162. What is the main difference between the rotathinner and
krebs stomer?Rotothinner measures dynamic viscosity and kerbs
stomer measures kinematic viscosity.
163. Describe how to use a ford flow cup?
Level the stand and cup. Place another cup under the flow cup to
catch the paint, fill the cup with paint ensuring it is full whilst
covering the 4mm hole in the bottom. Run a straight edge over the
lip of the cup to ensure it is full simultaneously remove finger
from bottom and start stop watch. Time until 1st break in flow. The
time recorded is the viscosity in seconds at the temperature.164.
Give another name for a fineness of grind guage?
Hegman grind gauge
165. How and for what is a hegman grind gauge used?
Paint is added to the deepest point of the scale and drawn along
to totally fill the groove using a specially profiled scraper bar.
Within 3mm band, five to ten aggregates break through the surface
of the paint, this is the point where surface will change from
gloss to matt, thus measuring the degree of dispersion of
paint.166. Briefly describe how to do the volatile, non-volatile
test to BS 3900 Pt B2?
A dry glass stirring rod and watchglass along with 2gm of paint
is weighted, watchglass containing paint is place into a hot air
oven, stir to drive away volatile content, take a final weight of
the glass, rod, and dry paint and simple calculation will give
volatile / non volatile ratio by weight.167. Name the equipment
used to determine the flash point of a solvent?
Abel cup.168. What colour should the flame be at the flash
point?
Blue colour.
169. What formula is used to calculate the density?
Density = Weight / volume
170. What formula is used to calculate specific gravity?
Specific gravity =Density / Density of water
171. What is relative density?
Weight of material divided by of volume of water
172. What are the other names for a density cup?Relative density
cup, specific gravity cup, weight per liter cup, weight per gallon
cup and pyknometer.173. What is a stoke, the unit for ?
A viscosity unit frequently used for kinematic viscosity is the
stoke. (kerbs units or poise).
174. Which test is used to determine Abrasion resistance?
Taber rotary abraser.
175. Which equipment would be used to determine
flexibility?Cylindrical mandrels.
176. Which equipment would be used to measure impact
resistance?
Tubular impact testers.
177. For what reason would the Koeing albert apparatus be
used?To test the hardness of a film.
178. For which two reason could a density cup be used on
site?
To calculate the density of the solvent.To calculate the 2 pack
are mixed in correct proportion.
179. Name four accelerated test boxes?
Humidity cabinets, salt spray cabinets, water soak tests,
temperature cycling and prohesion testing.
180. Why would a tropical box be used?For testing tropical
conditions.
181. Would a paint be higher or lower density than water?
Higher 182. How would the density be affected if solvent was
added to paint?
The density of paint decrease183. What is the capacity of a
density cup?
100 cc.
184. What difference is there between SG and Density?185. What
information could be obtained from a water soak test?
Painted panels submerged to test for water absorption.
186. What information could be obtained from temperature cycling
test?
Maximum and minimum temperature can be set and cycle time, over
a running period to 1000 hrs.187. What information could be
obtained from a cold check test?
188. Name four drying and curing tests?Mechanical thumb test,
Pencil scratch test, mechanical scratch test and gold leaf
test.189. What stage of the BK test would be recorded as the drying
time?
Solvent Evaporation time, the solgel transition, surface drying
time and final dry time.
190. Name three methods of determining opacity?
Trough type, black and white fused plate and cryptometer.
191. What effects the opacity of a paint film?
Pigment volume concentration.
192. Why would a Pfund cryptometer be used?
To measure Opacity.
193. Give one reason why an inspector would use a PIG gauge?
To measure MIO.
194. Why are wet paint film thicknesses needed?
To ensure that the DFT would be ok.195. Name two methods of
measuring WFTs?
Eccentric wheel and comb gauge.
196. What is the reason for taking WFT immediately after
application?
To obtain true readings (solvent start evaporating as it exits
the spray tip).197. Can a banana gauge be used on non-ferromagnetic
substrate?
No.
198. Could an eddy current gauge be used on ferromagnetic
substrates?
No.
199. Can a horseshoe gauge be used on non-ferromagnetic
substrates?
No.
200. As part of which test would a bar applicator be
used?Opacity.
201. Which instruments would be used to measure
reflectivity?
Gloss meter.
202. How does a gloss meter work?
A light source direct a beam of light onto the surface under
test and a photo cell, set at the same angle, collect the reflected
light and quantifies it and convert it digitally into a percentage
of the incident light. A high percentage of reflection will be
gloss and a low percentage will be matt.
203. Which factors in paint govern the degree of gloss?
Degree of dispersion, resin type and PVC
204. In a primer/mid coat what would be the expected degree of
grind?
40-45.
205. In a gloss paint what would be a typical degree of
grind?
20.
206. What percent reading would be expected when measuring gloss
on a glass panel?
Near 100%
207. Using a gloss meter a reading of 25% would signify
what?
Matt.
208. If an aggregate size of 35 um was present in a paint of 30
um DFT what would be a likely result when using a gloss meter?
Matt.
209. Name three common tests for determining adhesion of a paint
film?V cut test, cross cut and dolly test.
210. Which adhesion test are quantitative?Dolly test and
hydraulic adhesion test.
211. Inter coat adhesion and primer to substrate adhesion are
two adhesion faults name the third?
Cohesive failure.
212. What chemical solution is used to conduct a cathodic
disbondment test?
Sodium chloride.
213. What criteria is used when assessing a cathodic disbondment
test panel?
214. Name the methods of applying cathodic
protection?Sacrificial anodes system and impressed current
system.
215. What is used to determine the potential of a pipeline?
Copper sulphate half cell electrode.
216. Would it be advisable to refill a pipe trench with
carbonaceous backfill?
217. Does a cathodic protection system eliminate corrosion?
It controls where corrosion occurs.
218. Can the external surface of a tank be protected?No, In
order for cathodic protection to be applied, an electrolyte must be
present.
219. What voltage would be used on a 250 um thick paint using a
sponge pinhole detector?
9V.220. What voltage would be used on a 450 um thick coating
with sponge pinhole detector?
90V.
221. What function does the above additive perform?
Surface tension.
222. Would it be advisable to do wet sponge detection on
galvanizing?
No.
223. Does a sponge detector work on AC or DC?DC.
224. Other than the wet sponge which other equipment could be
used to determine the presence of pinhole/holidays?Spark detector
(high voltage)
225. Name two categories of paint mill?Ball mill and attritor
mill.
226. What is the main reason for processing paint in a mill?
Dispersing or Grinding or milling aggregates and agglomerates
down to a suitable size for the paint.
227. Briefly describe how a ball mill works?
Mill base is added to the drum until the balls are covered,
about 50% capacity of the drum. The hatch is then sealed off and
the drum started rotating at such speed so that the balls cascade
down and do not stick on the drum due to centrifugal forces. Shear
forces are applied to the mill base as the balls cascade between
the balls and vessel walls. A typical dispersion time would be
overnight.228. Briefly describe how a attritor mill works?
The attritor mill is a vertical version of the ball mill, but
more efficient and also static. The balls are driven by paddles.
The mill base is continually circulated by pump from bottom to top
and gives adequate dispersion in less time.
229. A bead mill is sometimes called by which other names?
Sand mill or pearl mill.
230. How does a colloid mill work?
Using grinding discs containing carborundum, approx. 10
diameter. The top stone is stationary and the lower stone is
rotating fast at a speed up to 3600 revs per/min. Gravity fed low
viscosity slurry enters the centre of the top stone and is passed
between the two stones by centrifugal force, where it is subjected
to extreme turbulence and shear forces to affect the
dispersion.
231. What do you understand from the term halogenated
hydrocarbon?
232. How can we determine the viscosity of a high viscosity
paint?233. Briefly describe the principle of CP?
A metal less noble than steel is included in the film and an
electrolyte eg. Water passes through the film contacting substrate
and pigment particle, then a circuit can engaged whereby the
pigment particles will receive the hydroxyl iron and thus suffer
corrosion in preference to the steel substrate.234. What function
does a primer have in a paint system?
Primer is normally low volume solid material, wets out substrate
and provide excellent adhesion and also provide a key for any
subsequent layer.
235. In a mordant primer what is the main working
constituent?Mordant means of a corrosive nature or will bite into
and as suggested contains an acid, phosphoric acid.
236. What advantages do electrostatic application methods
provide?
The coating material is positively charged and is attracted to
the component when using powder coatings, wastage is significally
reduce and it produces a more uniform coating.
237. Define exothermic?
Giving off heat, the container will warm up.
238. Define endothermic?
Taking in heat, the container will cool, forming
condensation.
239. What is cohesive failure in paint give the main cause?
Over thickness of a layer can entrap solvent during drying
process and stop formation of film, reducing cohesive strength. The
main reason for cohesive failure is solvent entrapment and
incorrect ratio mix to two pack.
240. Why does a zinc rich paint need a strong binder?
241. Why are etch primers not spray applied?
242. What do you understand by the term over spray?
243. Name four methods of determining DFTs?
Test panels, Calculations, Destructive test gauges &
non-destructive test gauges.
244. What is a psychrometer used for?
Psychrometer or whirling hygrometer used to determine wet and
dry bulb temperature from which relative humidity and dew point is
calculated.
245. What colour should a galvanized surface be after
application of T wash?
246. How soon can T washed substrate be coated?
247. Other than pigment, base and curing agent name two other
constituents fo FBE powder paint?
248. Give the main differences between airless and conventional
spray.?Conventional spray
Airless spray
Slow application
Excellent application rate
Low air pressure 40-75 psi
Can need 100 psi to operate pump
Delivery pressure greater than 20 psiDelivery pressure greater
than 6000 psi
Need special paint container
use manufacture container
Low maintenance
high maintenance
Easy to clean
need flushing to remove traces of paint.
249. Brush application has advantages over spray application,
what are they?
Environmentally friendly, less waste of material, any dust or
detritus on the substrate present worked in to the film.
250. What is the main consideration when selecting a metallic
pigment for a sacrificial paint?
The metallic pigment must be less noble (more
electronegative)
251. What is mean by sheredizing?Nuts, bolts or any fasteners
rely on tension are tumble in the powdered zinc, the tem used is
sheredizing.
252. Name three types of paint feed for a conventional
spray?
Suction Feed, Gravity feed & remote pressure pot.
253. What is calorising process?
Calorising is coating with aluminium, one way of calorising a
component is to dip it into molten aluminium.
254. What is the BS 2015 term for skipped or missed areas?
Holidays. 255. A colour has three properties, what are they?
Hue, Brightness & Saturation.
256. Why would be paint applied by hot spray?
When paint is heated it reduce in viscosity and cure or drying
starts quicker and reduces the need for solvent addition.257. On an
airless spray tip how are blockage cleared?
By turning the tip through 180o, triggering to ground or a
container to clear the blockage. 258. How is atomization achieved
using conventional sprays?
Approximately 25mm in front of the aperture two channels blow
air to converge at the paint stream. At this convergence the paint
is atomised into vary minute droplets and conduted onto the
workpiece
259. How is atomisation achieved using airless sprays?
Atomisation occurs by forcing the paint at extremely high
pressure usually 2000 to 2500 psi, through a very small aperture 12
to 23 thou diameter into a volume of air offering resistance to
paint flow as the air & paint meet the paint atomized.
260. What is dip coating?A component is dipped into a paint and
hung to dry.
261. What do you understand from the term ropiness?Brush
marks.
262. What is efflorescence and how does it occur?
A whitish crystalline formation on bricks, mortar, plaster
etc.
263. What is flocculation?
The development of loosely cohesive pigments agglomerates in
coating material.
264. What could be the cause of bittiness in a paint film?
Inculsion of foreign matter or within paint itself.
265. What are the hazard signs for Toxic, very toxic, harmful
and corrosive?
Black symbol of skull and crossbones on orange square for toxic,
very toxic.
Black diagonal cross on an orange square for harmful.
Black symbol showing a tilted test tube dripping onto a hand for
corrosive.
266. What is saponification?
The formation of a soap by the reaction of a fatty acid ester
and an alkali?
267. What units are used for measuring toxicity?
PPM.
268. Which material would have to be used on a perpetually damp
surface?
Moisture curing polyurethane.
269. What is padding?
Pads of mohair or foam are used to apply brush paint.
270. What causes lifting of a paint film?
Strong solvent over a coating using weak solvent.
271. Why would a paint inspector use potassium
hexacyonoferrate?
To detect iron soluble salt.
272. What would be an average thickness for galvanizing?
100 um.
273. How can you tell the difference between blooming and
chalking?
Blooming under surface , chalking over surface
274. What could be the reason for inter coat adhesive
failure?
Oil , Grease etc.
275. Why are manufacturer developing solvent free, water borne
and powders?
Environment protection act requirement.
276. How can bleeding be avoided?
By applying sealer first.
277. In less than 30 words explain the duties of a painting
inspector?
Activities such as measuring, examining, testing, gauging,
storage of materials, quality plan, site plan and relevant local
requirements.
278. What is meant by the term stripe coats?Paint applied by
brush to welds and edges.
279. How many cm3 are there in 4.5 litres?
4500 cm3 .280. Name two types of mill & describe their
work?
Direct charge mill and pre-mix mill.
Direct charge mill which takes and mill all the raw ingredients
together eg. Ball mill, attritor mill & high speed
dispenser.
Premix mill Take the ingredients which have been premixed to a
rough consistency and refine this mixture to a high quality paint.
This system is used for large production runs. Eg. Sand mill,
colloid mill, single row mill & triple row mill.281. What is
compliant coating ?A coating which complies with the requirement of
environment protection Act. 1990.
282. What is damp surface?
Surface on which water is not readily detectable but of which
the temperature is below the dew point.
283. What is fully weathered galvanizing?A galvanized steel
surface on which a cohesive oxide layer has formed by natural
weathering. The surface will normally be dull and lacking in
metallic sheen.
284. What is hot duty surface ?
Metal surfaces on the assembly that will attain a temperature of
100oC or above during use.
285. What is moist surface?
Surface from which standing water and droplets have been removed
but on which there is a noticeable film of water.
286. What is T-wash?
A non-proprietary material used as a primer or pretreatment for
zinc metal surfaces.
287. What has to be considered for maintenance or
repainting?Based on a survey of the item or plant which would
determine :The existing paint system.
The extent of breakdown and corrosion.
The in service environment conditions.
The nature and extent of any surface contamination.
288. Why & What Equipment to be protected and masked before
preparation and painting?Prior to any cleaning, surface preparation
or painting, the contractor shall protect and mask equipment and
areas in need of protection, with masking material. Eg. Fire
protection equipment, weld end preparation, lubrication paints and
nameplates.
289. What is the name of the mill used to produce mastics,
fillers and putties?
Tripple roll mill.
290. What special surface preparation are required for coating
on concrete ?
Scrabbling.
291. Give the reason why different surface require different
paint systems?
Painting always depends on the nature of surface (rusted,
pitted, or new), type of surface (ferrous or non-ferrous) condition
(industrial or marine) cost, temp. etc.
292. What additional information would you record when
maintenance painting a pipeline without removing the previous
coats?
What the existing painting is ?, The extent of breakdown and
corrosion, the in service environmental conditions, the nature and
extent of any surface contamination.
293. If you worked on a contract where frequent stoppage
occurred for poor weather, what additional information would you
record?what the weather conditions were, how long stoppage lasted,
progress of work to stoppage, assessment of damage caused by
weather to wet painted areas, loss of material due to stoppage.
294. Name an equipment used to test for opacity?Pfund
cryptometer, hiding power chart with applicator.
295. What is another name for a sand mill and describe its
operation?
Pearl or bead mill, rotation disc attached with vertical shaft
aid to shear as paint, slurry, forced through steel ball which
present between the disc. The degree of dispersion is high.
Suitable for long production run of popular paints.296. Briefly
state the preferred paints system ( and DFT) for new and
maintenance painting at works and site for above ground pipeline
and plant installations?High build aluminium primer - 75 um.
MIO
- 75 um
High build epoxy
- 75 um
Epoxy or polyurethane acrylic- 40 um
Total
- 265 um
297. List ten duties of paint inspector ?Learn the
specification, get to know the plant, ensure all concerned
understand the specification, keep the engineer informed at all
times of any departure from the specification, make written reports
at an agreed frequency, conduct and attend site meetings, before
commencing the work, check environment, equipment, materials, check
previous days work, agree the day work programme with contractors
senior personnel. On the completion of the each stage, ensure that,
system meets the specification by carrying out witness tests and
check for application faults. On completion of the work, make the
final check and the summary reports.
298. Describe contractors mall practice, which you are aware?Use
of unskilled labours, unsafe scaffolding, use of unsuitable
equipment, leaking compressor, brushes, damaged ladders, etc.
Insufficient blasting or paint in difficult areas likes underneath
of the pipe etc. painting and preparing the surface during in
inclement weather conditions, painting before inspection of
substrate or previous coats. Reusing of expandable abrasives, use
wrong solvent or an excessive solvent, use diesel in the paint as a
solvent or plasticizer, use of incorrect paint or different
manufactures paint. Applying of low thickness etc.299. What is the
procedure to remove algae and mould growth?
Algae and mould growth shall be removed by scrubbing with stiff
bristle brush, using clean water, after the removal of a boicidal
wash to be acceptable to prevent contamination of the new paint
system. All surfaces shall be dry before painting commences.300.
What particular problems relate to the splash zone?
Possibility of surface contamination (salt, water), damage (from
service & work coats), mould and algae growth high salt
contamination, restricted areas etc.