1.

SITE COATING INSPECTION

1. What type of abrasive would normally be used for site blasting?

Expendable copper slag.

2. Which British gas specification relates to safety during blast cleaning?

BGC PS SW 4. IGE/SR/21.

3. Which Swedish standard relates to surface preparation?

SIS 05 5900.

4. What does St 3 mean?

Very thorough hand and power tool cleaning. (Mechanical)

5. What is meant by Sa 2 ½?

Very thorough blast cleaning.

6. How is oil or grease removed from a pipe surface before dry abrasive blasting?

By using organic solvents like toluene or xylene. Any contaminant solvents shall be wiped
off with clean, dry lint free rags using fresh solvents in order to prevent a film or residue
forming on the pipe.

7. What is a rogue peak?

A rogue peak is a peak, which stands out above the required profile.

8. Can copper slag abrasive be used more than once?

No it is not reusable.

9. Can shot or grit be reused in a factory blasting operation?

Yes.

10. What do you understand by the term amplitude in relation to a blasted finish?

The size of the profile as measured from the peaks to the troughs is known as the amplitude
or peak to trough height.

11. Name the corn plaster method of measuring amplitude and describe its use?

Testex tape surface profile gauge is Press O Film tape. Press O Film is a replica tape
composed of an incompressible Mylar backing of known thickness (2 mils). Coated
with a compressible material. The tape is placed against the metal surface rubbed with a
blunt instrument. The pressure applied to the tape causes the compressible material to
replicate the blasted surface. By measuring the resultant tape thickness with a spring

Page 1 of 30
 micrometer, the maximum peak to valley height can be obtained by subtracting the
thickness of the Mylar backing from the total micrometer reading.
Press-o-film will also work accurately on convex and concave surfaces. It is also possible to
retain the tape and have a permanent record of the blast profile.

12.What are micrometer in relation to a millimeter?

Micrometer is an instrument used to measure thickness in microns, whereas millimeter is a

measure of length or thickness. 10¯

13. What is knocking out pot ?

It is a liquid moisture separator.

14. What is the usual Type/Shape of a blasting nozzle ?

15. What is the maximum allowable pressure from a blasting compressor to be in

accordance with British Gas requirements ?

100 P.S.

16. How can pressure be measured near the blasting nozzle ?

The pressure at the nozzle may be measured using a hypodermic needle gauge. This is placed
near the nozzle with the hole in the needle facing the nozzle at 45° inclination.

17. Describe the use of a deadman’s handle ?

Deadman shut off: It is a remote control valve, which allows the machine to be operated by
one man. When the blaster triggers the valve closes. If the abrasive hose is accidentally
dropped it shuts off (the flow of abrasive) thus eliminating accidents. It is a cut off safety
device. It is not used in factory. Best suited for field application.

18. Explain the sequence of operations during the footner duplex process.

Phosphating – only applies to the footner or duplex process. The technique involves a final
treatment in a 1 to 2% phosphoric acid solution held at 80°c for 1 to 2 minutes. This leaves a
thin rust inhibitive phosphate coating on the steel surface to which the coating should be
preferably applied while it is still warm, possibly after a final wash.

19. Describe the disadvantages of wire brushing for surface preparation.

The process is slow, laborious and costly. It is impossible to remove all rust and millscale by
this method. Manual cleaning is the slowest and least satisfactory method of surface
preparation. The biggest drawback to the use of power tools is the “Burnishing Effect” that
arises on the metal.

20. What is BS 7079 ?

BS 7079 : Preparation of steel substrates before the application of paint and related products.

Page 2 of 30
21. Describe the action of steel shot on a substrate during blasting compared to steel
grit.

Shot blasting work hardens a steel surface to a greater degree than grit which has the effect of
reducing the chance of any stress corrosion cracking, which could otherwise occur in the
future. Shot also reduces the occurrence of rogue peaks i.e. peens over any rogue peaks. It
does not cut new profiles.

22.Why is sand containing silica not used as a blasting abrasive ?

Associated health hazard of silicosis.

23. Name two methods of measuring peak to trough height.

By use of a surface profile needle gauge. Using a Testex tape.

24. How many micrometers in a thou ?

25.4 microns = 1 thou ( 0.001" ), (40 thou = 1mm)

25. What is a typical maximum time lapse between blasting and coating ?

BS 549 indicate a maximum delay of 4 hours and require that if visible deterioration has
occurred, the surface preparation shall be repeated.

2. ENAMELS / TAPES

1. What is the British gas specification for coal tar enamel materials ?

BGCS / PS /CW 1. Alternatively, BGC / PS / CW3.

2. What does the viscosity of a material mean ?

Viscosity means the measure of a fluid resistance to flow.

3. How are coal tar enamel coatings applied in the factory. List the sequence of operation.

1. Blast clean to SA 2 ½.
2. Remove grit etc., with a soft brush.
3. Prime area using a soft brush (spray). For coal tar enamel, use a synthetic type B fast drying
primer.
4. When the primer is dry, apply a flood coating of hot enamel.
5. Apply a glass fibre inner wrap whilst applying a second flood coating. The inner wrap must
not come within 1mm of the pipe surface.
6. Apply a third flood coating whilst applying impregnated glass fibre outer wrap (thermo
glass).
7. Apply a white wash – solar protective coating.

Page 3 of 30
4. Can Bitumen coating be overlapped with a coal tar ?

No. enamels may be coal tar or bitumen based. The two materials shall not in any
circumstances be mixed and in the case of application in the fluid the material to be used
should be chosen to match any existing pipe coating to which it will be required to adhere.

5. Describe a test to differentiate coal tar from bitumen.

Take a very small (about 3mm diameter) ball of the unknown enamel and place onto a sheet
of white blotting or filter paper. Put two or three drops of xylene or toluene solvent onto the
ball. The ring of the liquid running off the enamel and soaking into the paper will show
yellow with coal tar and show brown with bitumen.

6. Is it permissible to wrap welded butt joints using coal tar if the abutting pipes are
coated with polyethylene cladding?
No. It is not suitable material for use with PE clad pipe.

7. What precautions must be taken to prevent tarwarts when handling / using coal tar
enamels?

a. Keep bitumen and coal tar off your skin.

b. Wear protective clothing.
c. Do not put dirty rags or tools in your trouser pockets.
d. Wash your hands before going to the lavatory.
e. Watch out for warts.

It is strongly advised that those who work or have worked with coal tar or bitumen should
seek medical advice if they discover warts on their body.

8. What type of primer was / is used for the application of a) bitumen b) coal tar.

For bitumen enamel use a synthetic or bitumen based primer.

For coal tar enamel, use a synthetic type B fast drying primer.

9. What is Asphalt?

Coal tar + chalk + bitumen.

10. Why is a herbicide incorporated in bitumen coatings?

Bitumen enamel is capable of sustaining root growth and the incorporation of a herbicide to
forestall this is desirable.

11. What was / is the application temperature of coal tar enamels?

Coal tar enamels must be applied when it is at a temperature of between 240°c and 255°c.

12. What was / is the maximum temperature of coal tar can reach in the melting pot and
what action would be taken if this temperature was exceeded and why?

The temperature in the melting pot may be adjusted to suit site conditions provided that it
does not exceed 260°c. any enamel, the temperature of which has been allowed to exceed
260°c shall be rejected.
Page 4 of 30
13. What was / is the application temperature of bitumen enamels?

For bitumen enamels the application temperature must not exceed 230°c.

14. Where does bitumen comes from?

It is a by-product of Hydrocarbons from Petroleum Industry.

15. How could the temperature in a melting dope be determined?

By Metallic thermometer.

16. Is it necessary to agitate enamel in a melting / doped pot?

Yes. It is essentially needed to agitate the enamel. A mechanical agitator shall be kept in
operation whilst the enamel is melted and periodically thereafter.

17. Why is lime wash applied to the external surface of enamel coated pipes?

To protect from direct sunrays. Solar protection, to avoid excessive heat absorption etc.,

18. What do you understand by the terminology disbonded thermo glass?

Outer wrap not adhering to the flood coating of the coal tar.

19. How may the temperature of a pipe surface be measured in low ambient temperature
conditions?

Using magnetic surface temperature gauge.

20. What icicles on enamel mean coated pipe?

Substantial lack of thickness and inclusions in the coating i.e. pinholes etc., As the enamel is
applied use a rubber or canvas sling to spread and smooth off the coating to prevent the
formation of icicles on the underside of the pie or fitting.

21. How much enamel is required between the inner wrap and the pipe surface?

Under no circumstances shall the inner wrap be so tensioned as to leave less than 1.mm of
enamel between it and the pipe surface.

22. List the eight types of coating / wrapping materials.

a. Coal tar b. Bitumen c. Polyethylene d. Cold applied tapes (self-adhesive)

e. Hot applied tapes f. Cold applied laminate tapes. g. Grease based tapes
h. Brush / spray applied coatings. i. Mastic, fillers and putties
j. Heat shrinkable plastics. k. Epoxy powder and urethane tar.

Page 5 of 30
23. What do you understand by terminology “bleed through” in relation to enamel flood
coatings?

The outer wrap should stay on the surface of the enamel except for the bleed through which is
necessary to obtain an adequate bond and to prevent lamination.

24. What is the total minimum thickness over the plate and over the weld for enamel
coatings?

The finished coating must have a general thickness of 4.mm and be atleast 2.4mm thick over
all welds.

3. ENAMEL / TAPES.

1. What is meant by the term holiday?

To detect any holes or lack of thickness in the wrap or any inclusions. These defects are
called holidays. Poorly or missed coatings.

2. What is the abbreviation for C.T.E.?

Coal tar enamel.

3. Describe the operation for repairing pinholes on coal tar coated pipes?

Minor abrasions and holidays may be made good by carefully smoothing out the enamel with
a suitable hot implement and adding as necessary further hot enamel to maintain the required
minimum thickness.

4. Describe the operation for repairing a damaged area of 150mm x 150mm, on a 750mm
diameter pipe, coated with coal tar.

a. Remove the coating to cut edges of the repair portion.

b. Wire brushing should be done to grade St 2.
c. Remove all dust from the cleaned surface with a soft brush.
d. Apply primer to the clean dry metal surface.
e. Ensure that the metal surface is covered.
f. Cut to size the inner wrap.
g. Apply hot enamel over it, above to it with an outer wrap a patch would be sufficient to
overlap the previous area.

5. How soon after application can adhesion checks are carried out on coal tar or bitumen
coatings.

Bond test is carried out at a frequency specified by the engineer and when the inspector has
reason to believe that adhesion is suffering.

6. What voltage is required for holiday detecting coal tar coatings?

15 kV.

Page 6 of 30
7. Describe how a bond test is carried out enamel coating?

a. Measure the temperature of enamel wrap. If the temperature of wrap is not between 5°c and
25°c cool or warm the test area to bring the wrap temperature within that range.
b. Using a knife, heated if necessary, make two parallel cuts through the wrap to pipe surface
about 100mm long and 30mm apart.
c. With a stiff flat blade loosen the wrap the full width between the two cuts and lift the wrap
upward in a direction at right angles to the pipe surface.
d. The bond shall be considered satisfactory if the wrap does not peel clearly away from the
primer or the pipe surface but is removed with difficulty causing cohesive failure of the wrap.

8. What precautions must be taken if using xylene as a degreaser?

Concentrated vapors from this material are toxic and if inhaled in an undiluted form will
cause severe dizziness and headache. It is therefore desirable to use this material in open
conditions or if indoors in a well ventilated workspace. Smoking or naked flames should not
be permitted in the immediate zone of use. Liquid solution is kept away from the eyes and
skin and the use of eye shields and gloves is recommended.

9. What is meant by the flash point of a liquid / solvent?

The flash point of a material is the lowest temperature at which the vapor given off will ignite
when a flame or spark is passed over it. A highly volatile material will have a lower flash
point than a material of low volatility.

10. How may coal tar enamel be removed from a pipe?

Removal of coating should be by means of a knife, scraper and or approved copper headed
hammer as applicable and in a manner which will not cause damage to the metal surface.

11. Is it permissible to use turpentine or white spirit as a degreaser?

No. It will leave oil residue.

12. Why are barrier cream and protective clothing worn when handling coal tar enamels?

Coal tar, when heated can give off hazardous and irritant fumes, therefore barrier creams,
positive pressure facemasks, and or goggles (to protect the face and eyes) shall be used. At all
times when handling hot enamel, impervious protective gloves and other appropriate
protective clothing e.g. Aprons & boots should be worn to prevent contact of the skin with
hot enamel.

13. How is primer applied?

Primer is applied with a soft brush.

14. Primers must overlap existing coatings by how much?

150mm. Minimum overlap.

15. What voltage is required for holiday detecting PE cladding?

Holiday detection at 10Kv.

Page 7 of 30
16. What precautions are taken to prevent solvent loss from primer application containers?

Extremes of temperature during storage should be avoided. Only the required amount to be
transferred to small containers. Primer cans should not be left open.

17. What is the minimum thickness for polyethylene cladding and the underlying mastic in
accordance with PSC / CW 4?

PE tape coated with a thin pressure sensitive adhesive. The tape thickness may vary from
0.15mm to 0.5mm

18. How is damaged polyethylene cladding repaired if damaged?

Repairs to PE clad pipe can be effected by spirally wrapping after trimming off any loose
material.

19. How are damaged polyethylene coatings repaired?

Polyethylene coatings shall be repaired by application of mastic over it a size of PE coat is

applied.

20. What is the material specification for cold applied self adhesive tapes and cold applied
laminate tapes?

For cold applied laminated tape BGC PS CW2

For self-adhesive tapes BGC PS CW5.

21. Name 2 British gases approved applied self adhesive tapes.

Scotch wrap, all weather sellotape.

22. What are cold applied self-adhesive used for?

Tapes are compatible with most of the pipe coatings. PE tapes mould to contours- they may
be used as an outer wrap over grease base tapes. Self-adhesive cold applied tapes can be
readily applied to long pipe lengths by means of a hand-operated machine.

23. What is the abbreviation for M.C.L?

Multi compound liquid.

24. Name three British gases approved cold applied laminate tapes and their corresponding
primers.

Maflo wrap - B400

Servi wrap - servi wrap
Plymcote - Plymcote
Densopal - Densopal primer
Scotch wrap vinyl mastic - scotch wrap
Royston greenline - Royston 747 primer
Page 8 of 30
25. What is the voltage required for holiday detecting cold applied laminate tapes ?

15 kV.
Except Royston green line _ 10Kv.

4. ENAMELS / TAPES.

1. Is Cold laminate tapes compatible with Coal tar and Bitumen coatings ?

Yes – They are generally compatible with Coal tar, Bitumen and PE

2. What precautions must be applied when back filling over pipes wrapped with cold
applied laminate tapes ?

Imported fill to replace heavy clays, particularly where depth of cover is excessive and
backfill consolidation is difficult, plastic laminate tapes are susceptible to rock stone damage
and may require special backfill measure. Their use on thrust sling should be limited. They
are susceptible to sling handling damage particularly in warm weather.

3. Are primers considered essential for cold applied laminate tape system ?

Yes – Use of primers considered essential not with standing manufacturers recommendations
to the contrary.

4. How much overlap is required for cold laminate tapes on joint coatings ?

Welded joint wrapping must be applied in a spiral fashion with 55% overlap to give a
minimum of two-tape thickness. Consideration may be given to applying the thicker tapes
with only 25mm overlap.

5. Which specification covers the application of cold applied tapes ?

BGC PS CW2

6. Why does British Gas not approve the use of hot applied tape ?

Due to the health hazard involved in these operation carcinogens is formed due to inhalation
of fumes due to coal tar and bitumen.

7. What materials make up a hot applied tape ?

Hot applied tapes usually consist of a synthetic fabric bandage ex, woven nylon, coated with
a layer of plasticised coal tar or bitumen.

8. What is Densotape ?

Densotape is a greased-based tape.

9. What is a Flood box ?

For collecting excess powder.

Page 9 of 30
10. What are Mastics and Putties used for ?

Mastics, filler and putties are used extensively for rationalizing irregular shapes. Suitability
for use on components operating at elevated temperature or in situations where soil stressing
might occur will be largely related to the base material of the product.

11. Is it possible to holiday detecting grease-based tapes ?

Holiday detection is not applicable for grease base tapes, unless they are over wrapped in this
case is 12 to 15 kV.

12. What are Metros 1341 and Matresol 1340 ?

Brush / spray applied coatings. It is a brushing plastic Denso Metrosol 1341 – Mastic 1341.
Its primer is Metrosol 1340.

13. Describe the use of Heat shrinkable plastics.

Heat shrinkable plastics are commonly supplied as a pre expanded sleeves, wraparounds or
tapes having a coating of heat sensitive mastic on the surface which makes contact with the
pipe. On application of heat by blowtorch or other means, applied to the central area working
outwards, shrinkage of the plastic takes place, the softened mastic layer acts as a
sealant/adhesive. Use of primer is not normally recommended.

14. Can valves be coated with brushing mastics in accordance with the current BG
PSCW5 ?

Yes.

15. What is the expected thickness of a brush or spray applied compound ?

500 microns.

16. What is typical voltage for a holiday detector battery ?

6 volt battery.

17.Explain the use of a holiday detector on a tee piece.

To detect lack of thickness or holes in the wrap. Brush, which consists of many thin copper
strands, attached to the end of an insulated hand stick. The brush is often used for joint
wrapping around areas where the coil will not travel e.g., tee piece. The bleeper will sound
when the circuit is complete i.e. on a holiday.

18. What happens to the kV dial when a holiday is detected ?

When the coil comes into contact with a holiday the kV dial will drop and the bleeper will
sound.

Page 10 of 30
19. Explain the operation of holiday detector on FBE coated pipe.

Coil spring type –

a. Preset the voltage to 125v for 25minutes.
b. Pass this coil spring through the coated (fbe) pipe.
c. Where there is holiday it produces a spark, visual warning and an audio signal beep will be
heard.
d. Speed of running of the coil 1 ft/sec. Mark the holiday area with waterproof markers. Repair
that area. Re inspect and retest.

20. Is it possible to holiday detect wet coated pipe ?

No.

21. What will happen if the voltage selected for holiday detection is too high for the
coating ?

This will cause holidays by an arc burning through the coating.

22. What material would be used to repair damaged brushing mastic coatings ?

The same mastics shall be reapplied for repairs.

23. What is the title for the BGC PS 10 ?

General pipelining specification – For ditching and back filling.

24. What is the specification which covers handling and storage of steel pipe bends and
Tees?

BGC PS L3. Handling, transport and storage of steel pipes, bends and tees.

25. What is thermoplastic coating ?

A paint, which returns to a liquid state when heat is applied, is known as thermoplastic.
Epoxy powder coating is done in this method.

5. ENAMELS / TAPES.

1. What are the duties of an inspector covering a ditching operation ?

The inspector must make sure that there are no stones, electrodes etc., present in the ditch,
which could cause damage to coating. He must also ensure that the base of the ditch is evenly
bedded. When the pipes are lifted from, the skids before lowering in the coating must be
checked by holiday detection to ensure freedom from skid damage.

Page 11 of 30
2. Is it permissible to ditch coal tar coated pipe when the ambient temperature is 25°c ?

No.

3. What happens to the base of a trench excavated in rock before ditching ?

The rock area will have a rough hard surface. If the trench is excavated in a rock a well
rammed bed of approved sand / gravel mixture, 150mm deep must be applied to the base of
the ditch.

4. Describe the back filling operation in accordance with the BGC PS P10.

When back filling the best of the previously excavated material is returned to, the trench
providing it is free from stones in 300mm layer. Each layers being well compacted with hand
rammers or mechanical vibrators before the deposition of the next layer.
Stone free layers are deposited until the backfill material is atleast 300mm above the top of
the pipe then the remaining excavated material is returned to the trench in 300mm layers and
compacted as above. Any stones present must pass through a 200mm-ring gauge. The
minimum depth of cover between the top of the pipe and the surface of the top of the soil is
1.1 Mts.

5. What is the minimum depth between the top of the pipe and the surface of the topsoil, in
accordance with BGC PS P10?

1.1 Mts. is the minimum depth.

6. Describe a simple method to check for laminated coal tar coatings.

Take a very small ball (about 3mm in dia) of the unknown enamel and place onto a sheet of
white blotting or filter paper. Put two or three drops of xylene or toluene solvent onto the
ball. Th ring of liquid running of the enamel and soaking into the paper will show yellow for
coal tar and brown for bitumen.

7. What is the safest method to handle pipes in accordance with BGC PSL3 ?

Where practicable pipes shall be lifted using a spreader beam with suitable slings (nylon tape)
as this is the safest method. Where a spreader beam is not practicable two leg chain slings
(brothers) shall be used, there shall be fitted with properly designed profiled hooks fitted with
guide ropes, and the inner edges of the hooks shall be coated in nylon or soft alloy.

8. Is it necessary to pad cradles and baten carriers ?

Yes it is necessary to pad with atleast 12mm of rubber at contact points.

9. Describe the method for handling bends or tees.

When handling bends or tees, a nylon sling shall pass through the bores.

10. Describe the stringing operation on a pipeline ?

With the use of spreader beam with suitable nylons the pipes shall be lifted and kept in line,
one pipe preceding the other with slight overlap.

Page 12 of 30
11. Is it necessary to choke pipes when using cradles during transportation ?

Yes.

12. Are holiday detector ac or dc ?

It is dc.

13. What do you understand by the terminology soft standings in relation to the
storage of pipes ?

Soft standings consist of two parallel sand rows separated by approximately ¾ of the
Pipe length .

14. How many bearers and pads (hard standings) are required when stacking pipe of
standard wall thickness coated with polyethylene cladding ?

Hard standings which may only be used on a flat firm ground, consists of bearer (skids)
padded with wood wool pads, number of which is dependent on a table in BGC PSL3.

15. When stacking polyethylene clad pipe. How many pads are required between tier ?

Two.

16. What is the maximum no. of tiers, if stacking coal tar coated pipe 900mm diameter ?

Three tier.

17. What is the maximum no. of tiers required if stacking FBE coated pipe 42” diameter.

Two

18. How many bearers and pads (hard standing ) are required when stacking pipe of
standard wall thickness coated with epoxy powder ?

Stacks of three.

19. How could the joint be coated / wrapped if a pipe coated with epoxy powder was welded
to a pipe clad with polyethylene ?

With M.C.L or shrink sleeve.

20. Is it permissible in accordance with BGC PS CW5 to overlap onto polyethylene

cladding with primer for cold applied laminated tapes ?

Yes. Permitted.

21. What is meant by gunting ?

Application of concrete mix by mechanical means.

Page 13 of 30
22. Describe a Pearson survey.

23. Is it possible to ditch a length of pipe into a trench half full of water ?

No. it should be dewatered and then lowered.

24. Define the term brothers in relation to the handling of the pipe.

Where a spreader beam is not practicable two leg chains (brothers) shall be used, these shall
be fitted with properly designed profiled hooks fitted with guide ropes, and the inner edge of
the hooks shall be coated in nylon or soft alloy.

25. List four safety precautions during dry abrasive blasting.

a. Use of a dead-mans handle to stop the flow of abrasive when the operator lets go of the
nozzle.
b. Use hoses of the correct type i.e. reinforced.
c. Restrict the pressure to 100psi.
d. Use of carbon impregnated hose to reduce the chance of static shock.
e. Operators should wear protective clothing, including an airfed helmet, boots, leather, apron
and gloves.
f. Keep the hoses as straight as possible to prevent kinks which may lead to blowout.

6. POWDER COATINGS - APPLICATIONS

1. What do you understand by the term “Blueing of steel”?

Rust formation. After blasting the surface, steel exposed to environment will get oxidized.

2. Which British gas specification covers field application of epoxy powders?

BGC PS CW5.

3. Can epoxy powder coatings be applied on butt joints if the adjoining pipes are coated
with polyethylene cladding?

No. if it is epoxy you cannot coat.

4. How is degreasing operation carried out prior to blasting for epoxy powder coatings?

Any grease or oil can be removed using a suitable solvent e.g., xylene within a band of
500mm centered on the weld.

5. What amplitude is required on blasted joints prior to the application of epoxy powder
coatings?

50 micrometer and 100 micrometer.

Page 14 of 30
6. What grade of preparation is required for epoxy powder coatings?

BS 4232. 2nd Quality – Sa 2 ½.

7. By how much it is necessary to overlap on to the FBE coating (factory) during blasting?

25% diameter of the pipe.

8. What is Sliver?

Sliver is surface lamination.

9. If there is any jagged or disbonded areas remaining on the factory coating after blasting
it is necessary to feather the edges back, by how much?

The edges of the existing coating are feathered back by 15 mm.

10. If a sliver is present on a blasted surface what action must be taken?

If any are present they are ground using a grinder and provide correct wall thickness remains
the ground areas are subjected to further blast cleaning.

11. How are blasted joints heated prior to powder application in the field?

This is done by induction (heating) heater which is clamped around the joint to be coated.

12. What is a typical application temperature for epoxy powder?

253°c. should not exceed 300°c

13. What safety precautions are required during heating?

Any source of ignition should be kept away from the area where epoxy powder is being used.
Masks should be worn when working with epoxy powders to prevent inhalation and to
protect the eyes.

14. The temperature of steel during heating should never exceed…. °C.

300°c.

15. How are the steel temperatures measured after heating?

The metal temperature is measured by means of tempil sticks or by a suitable thermocouple.

16. How soon after the heating must epoxy powder be applied?

When the metal temperature falls down to the application of temperature range e.g., 218 to
246°c.

17. What is the minimum and maximum coating thickness for factory and field applied
epoxy powder coatings?
Minimum cured coating thickness 400 microns.
Maximum cured coating thickness 650 microns.
Page 15 of 30
18. How is the coating thickness measured?
By the use of calibrated magnetic film thickness gauge (banana gauge)

19. By how much should the field coating overlap the factory coating?

30 mm.

20. Is over spray reclaimed?

Yes.

21. What do you understand by over spray?

Application of non-uniform and certain areas where coating thickness is more than required.
Powder application is more at those locations is over spray.

22. Is the epoxy powder melted prior to application or when it hits the pipe?

When the powder comes into contact with the hot metal surface, it melts to form paint like
coating.

23. How is differential curing of epoxy powder coating reduced?

To reduce the differential curing of epoxy resin the required coating thickness is applied in as
few passes as practicable.

24. Why must the spray container be checked during the powder application?

To ensure there is enough powder to complete an application process.

25. Can reclaimed powder be reapplied.

Yes. It should be free from contamination and it must not exceed 25% of the powder in the
spray container.

7. POWDER COATINGS – INSPECTION, FUSION BONDED EPOXY

1. How often are thickness checks required on field applied epoxy powder coatings in
accordance with the relevant British Gas Specification?

All coated butt joints should be subjected to thickness checks. After a coated joint has cooled
thickness checks are made at six positions spaced equidistantly around the circumference.

2. What do you understand by WFT & DFT?

Wet Film Thickness – WFT

Dry Film Thickness – DFT

Page 16 of 30
3. Where on epoxy coated joints are thickness checks taken?

At six positions, spaced equidistantly around the circumference.

4. Describe the calibration of banana gauge.

a. Choose a magnetically insulated shim of known thickness close to the thickness of

the paint you expect to find. (Always use the white shim)
b. Place the shim on the same substrate, surface finish on which the paint to be
measured is attached e.g. if the paint is on a blasted surface, calibrate the gauge on
an uncoated blasted surface.
c. Place the magnet onto the shim and press firmly on the instrument, wind the scale
wheel forwards until the magnet is definitely attached to the shim/ substrate.
d. Gradually wind the wheel backwards slowly until the magnet detaches itself. At
this point, move the cursor on the instrument to the thickness of the shim as
shown on the scale wheel with some instruments, the scale itself must be moved
up to the line up with a fixed cursor. When using the latter type of instrument,
rotate the wheel to zero to locate the position of the scale adjustor.

The instrument is now calibrated and may be used to measure the d.f.t of any
Non-magnetic paint films to within a claimed accuracy of +/- 5% in some case.

5. What action is taken if any epoxy powder coated joint has insufficient thickness?

If any areas are under thickness, the engineer may require the butt to be reblasted and
recoated or repaired by approved means.

6. Is it permissible to store powder overnight in the application container?

No. The powder should not be stored overnight in the application container. Bad storage can
affect gel time.

7. When working with epoxy powder what safety precautions should be taken?

Masks should be worn when working with epoxy powder to prevent inhalation and to protect
the eyes. Any sources of ignition should be kept away from the area where epoxy powder is
being used.

8. How soon after coating with FBE can holiday detection be carried out?

All coated butt joints are subjected to holiday detection when they have reached ambient
temperature.

9. How much voltage is required for the holiday detection of FBE coatings?

The voltage used is 125 volts per 25 microns of coating thickness e.g. 2 kV for 400 microns.

10. What is special about the springs used for the holiday detection of FBE coatings?

The brushes used are carbon-impregnated neoprene and can be of the curved type to suit the
contour of the pipe. If a spring is used it should be ‘D’ sectioned so there is maximum contact
to the pipe surface.

Page 17 of 30
11. Is it permissible to store powder overnight in the application container?

No. The powder should not be stored overnight in the application container- bad storage can
affect gel time.

12. Are epoxy powder coatings thermosetting or plastic?

Thermosetting.

13. What do you understand by thermosetting and thermoplastic?

Thermosetting means, when heat is reapplied to a cured coating it will not return to a liquid
state. A paint, which returns to a liquid state when heat is applied, is known as thermoplastic.

14. How is epoxy coating cured?

By cross-linking.
15. How often are curing checks carried out on epoxy powder coatings and how are they
tested?

These are carried on the first ten joints coated and then at a frequency agreed with British gas.
Samples of coating are taken from the weld and parent plate at the six ‘o’ clock position and
then sent for a DSC scan.

16. Describe briefly how the curing tests are carried out.

Samples of coating are taken from the weld and parent plate at the six ‘o’ clock position and
then sent for a DSC scan.

17. Why are epoxy powder coatings developed?

Because they are solvent free.

18. Describe Polymerization and Cross-linking.

A polymer is a giant linear molecule i.e. a string or structure of repeated units, these single
units are known as mers or monomers. Polymers, although they are heavy molecules, are
made up from atoms and compounds composed of elements with a low molecular weight,
such as carbon, hydrogen, nitrogen and oxygen. The formation of polymers is a chemical
process known as polymerization.

19. Describe the adhesion test carried out on epoxy powder coatings and how often are they
needed to do.

These are carried out on the first ten butts then at a frequency agreed by British gas.
1. Using a Stanley knife make two 13 mm long incisions through the coating to the
metal surface to form a ‘v’ with an angle of 30° (approx.)
2. Force the coating from the pipe using the Stanley knife starting at the tip of the ‘v’
The coating shall be deemed acceptable if it refuses to peel.

20. Explain the repair procedure for pinholes in epoxy powder coating.

Abrade area, then repair pinhole using a quick setting epoxy repair kit i.e. interpon and retest
the area.
Page 18 of 30
21. What is relative humidity?

Relative humidity is the amount of water vapour in the air expressed as percentage compared
to the amount of water vapour that could be in the air at the same temperature.

8. POWDER COATINGS – TWO PACK EPOXY

1. Describe the use of melt stick for the repair of epoxy powder coatings.

Heat repair area using a propane or butane torch and apply melt stick into flame and wipe
stick in a circular motion onto the heated surface to produce a smooth patch of 600 microns
approximate thickness.

2. Describe the use of two pack epoxy repair materials?

Components of the coating material e.g. Base and curing agent are supplied in separate
containers (tubes or tins) and shall be thoroughly mixed in the proportions specified by the
manufacturer. The components are usually supplied in different colour is achieved without
any streaking. No thinner shall be used at any time.

3. Can thinner be applied to epoxy two-pack prior to application.

No.

4. What do you understand by pot life and induction period?

Pot-life: The length of time after induction that a two-pack paint can be applied.

Induction Period: The length of time a two-pack needs to stand after mixing and before
application.

5. What D.F.T. is required for two-pack epoxy repairs?

600 microns thickness.

6. Can cold laminate tapes be used on epoxy powder coatings in accordance with
British gas specification.

Yes.

7. What do you understand by the term gel time?

When the powder reaches it’s melting point temperature before solidification.

8. Can heat shrinkable plastics be used for repairs on epoxy powder coatings in
accordance with British gas specification.

No.
Page 19 of 30
9. Urethane material should be in accordance with which British gas specifications.

BGC PS CW6 PART 1.

10. Is it permissible to coat a joint using a urethane coating if the pipe is coated with
epoxy powder?

Yes.

11. Are Tie-in welds coated with epoxy powder?

No.

12. What is the instrument used for the measurement of relative humidity and dew point?

Whirling hygrometer.

13. Is it permissible to British gas standards to apply F.B.E. coatings during rain, snow or
Mist?

Yes if protective canopies are used.

14. Is it permissible to British gas standards to apply urethane coatings when the material
temperature is 12c.

Yes. If it is less than 10c – no.

15. What is Scotchkote 206N?

Fusion bonded epoxy powder made by 3M and usually peppermint green.

16. What is a typical pot life for urethane tar two-pack coating?

Pot life is the time lapse between mixing and the time where the material is no longer
usable, it is stated by the manufacturer e.g. 15 minutes at 15c.

17. What is the maximum permissible relative humidity for the application of a two pack
Urethane coating?

RH 80

18. What are the two materials that make up a Urethane tar base?

Urethane tar coating consists of a base part A and a curing agent part B.

19. How is it possible to shorten the cure time of a Urethane two pack coating?

By preheating the prepared surface, with the engineer’s approval.

20. What is the difference between Protogol 32-10 and Protogol 32-10L?

Protogol 32-10: Spray application.

Protogol 32-10L: Application by brush/trowel.
Page 20 of 30
21. Can Protogol 32-10L be used on pipe to be thrust bored?

No.

22. Is Protogol 32-10L compatible with Protogol 32-10?

No.

23. Is Protogol 32-10L compatible with epoxy powder coatings?

Yes.

24. Is Protogol 32-10L compatible with coal tar coating?

No.

25. Describe the application of Protogol 32-10L.

Two components should be mixed by pouring the total components of part B into part A.
ensure that the maximum amount of part B is added by scraping residual material from the
sides of the container with the Spatula or knife. The mixing ratio is 3:1 by ratio. Pot life is 10
minutes at 20c.
1. When large areas to be coated, the contents of one pack will be insufficient to coat the
total area to the required thickness. In this case coating thickness is built up in layers to a
total D.F.T. of one mm.
2. Commencing at the underside of the pipe, apply the compound with the scraper (75-mm
blade) spreading the material in a circumferential manner and directing excess material
into the weld bead.
3. Allow to dry for one hour then apply a second layer, this time working in the longitudinal
direction. Ensure a smooth final appearance.

9. POWDER COATINGS / MULTI COMPONENT LIQUIDS – URETHANE

1. What is the minimum overlap required when using two pack urethane on pipes
Coated with coal tar?

150 mm minimum.

2. What must be done at the interface if the two coatings as per the above question?

The interface of the two coatings should be over wrapped using a heavy duty cold
applied laminated tape.

3. When can a pipe be handled after coating with urethane?

Coated pipes should not be handled until the coating is fully cured (24 hrs)

4. Is it permissible to spray apply Protogol 32-10L, if not how is it applied?

No. It is applied by brush / trowel.

Page 21 of 30
5. Is it permissible to spray apply Protogol 32-10, if not how is it applied?

Yes. Spray by application.

6. What is the difference between airless spray and conventional spray?

In an airless spray the paint is atomized. There is no air cap on the gun. The spray tips on the
airless spray guns or usually lined with tungsten carbide, some have the advantage of being
fully reversible by turning a lever 180 to clear out any blockages in the small orifice. Using
airless spray equipment can be very dangerous due to the high fluid pressures.

Conventional spray: Type – Gravity, Suction and Remote Cup.

More expensive than brush but cheaper than airless. Four to five times quicker than
brush. Cannot apply coatings as quickly or as thickly as airless. Takes time and lot
of solvent to wash equipment. Masking is required. Lengthy time is required, low
pressure. Thin coating can only be applied. Personnel safety is required.

Airless spray.

Very expensive, maintenance and parts also expensive. Upto 30 times quicker than
brush. Only method for applying high volume and high thickness of paints. High
build coatings. Dangerous if not used properly (high pressure). Safety clothing,
Trigger locking and gun hoses to be kept in good condition.

7. If spraying is used to apply urethane coating, it is necessary to flush out the spray gun
after use. What precautions must be taken before the next application of urethane?
What would have happened if this were not done properly?

Normal practice is to flush out the spray gun using a solvent, this stops the coating –
gelling in the equipment. When work recommences the coating spray must be
solvent free, otherwise blistering would occur.

8. What kV is used on the urethane tar coatings?

Voltage used is a 125 volts per 25 microns of coating thickness e.g. 5 kV for 1 mm.

9. How often is hardness / cure test carried out on a urethane tar coatings?

These are carried out on the first 10 butts on a contract then at a frequency agreed by
Bgas.

10. Describe how an adhesion test is carried out on a urethane coating.

Using a Stanley knife make two 13-mm approximate long incisions through the coating to the
metal surface to form a ‘V’ with an angle of approximately 30. Force the coating from the
pipe. Use the Stanley knife starting at the tip of the ‘V’. The coating shall be deemed
acceptable if it refuses to peel.

Page 22 of 30
11. Describe briefly how epoxy powder is applied to a pipe in a coating mill.

1. Surface preparation – Blast cleaning Sa 2 ½.

2. Heating by induction coil. Joint heated to 253c.
3. Coating manual or semi automatic spray - Metal temperature 218 - 246c. Coating
thickness is applied in few passes to reduce differential curing.

12. What is an approximate range for epoxy powder particle size?

13. What is the minimum thickness for Protogol 32 – 10L in accordance with CW5?

1 mm.

14. How much overlap is required on to a F.B.E. coated pipe using a urethane coating in
accordance with the requirement of CW5?

Overlap – 75 mm.

15. What precaution must be undertaken to prevent damage on factory epoxy powder
Coatings during welding?

If welding is done, cover the near by area by use of insulating material e.g. fire proof blanket.

16. What precautions must be undertaken to prevent damage on factory epoxy powder
Coatings during the handling of pipes using side booms?

Where practicable pipes shall be lifted using a spreader beam with suitable slings (nylon
type) as this is the safest method. When a spreader beam is not practicable, two leg chain
slings (brothers) shall be used. This shall be fitted with properly designed, profiled hooks
fitted with guide ropes, and the inner edge of the hooks shall be coated in nylon or soft alloy.
Chains shall not be slung around pipes even if padded.

17. What precautions must be undertaken to prevent damage on factory epoxy powder
Coatings during bending of the pipes?

Rubber padding shall be lined in the bending machines. Bending shall be carried out in
ambient temperature.

18. In accordance with BGC PSL3 is it permissible to use steel hooks to lift pipes coated
with epoxy powder?

No.

19. To CW5, if the air temperature is 10c is it permissible to apply urethane coatings?

If it is less than 10c not permitted. But at this temperature can be done.

20. What is the problem with long term storage of epoxy powder?

Supplied in paper sacks and should be kept dry at all times, but should not be left in direct
sunlight or stored overnight in the application container, otherwise the curing of the coating
may be adversely affected.
Page 23 of 30
21. If it is required to remove an epoxy coating on a joint, how would this be carried
out?

1. Blast clean to Sa 2 ½ abrading sound coating atleast 10 mm back from exposed metal.
2. Remove dust etc., using a compressed air.
3. Repair using two – pack repair material.
4. Holiday detect.

22. Is it permissible to degrease a urethane coating or an epoxy coating using white

spirit?

No. Not permitted. It will leave oil residue on surface.

23. Is epoxy powder inflammable?

Yes.

24. List the four stages of transformation for epoxy from powder to hard film.

1. Flow time powder to semi liquid.

2. Wetting time powder to liquid.
3. Gel time powder to the start of solidification.
4. Cure time powder to completion of cross-linking.

25. An F.B.E. coated pipe is welded to a urethane coated fitting. How would the joint be
coated?

When coating joints made on epoxy coated pipes the joint coating overlap should be
approximately 75 mm.
The interface of the two coatings should also be over wrapped using a heavy-duty cold
applied laminated tape.

10. POWDER COATINGS / MULTI COMPONENT LIQUIDS – INSPECTION AND

TESTING

1. How long would a brush / trowel applied urethane coating required to fully cure at
20c?

Eight hours.

2. When would be a brush / trowel applied urethane coating be touch dry?

Touch dry – two hours at 20c.

3. What precautions are necessary to prevent damage to F.B.E coated pipe when profile
cutting?

Mask up area.
Page 24 of 30
4. Is it permissible to thrust bore a pipe coated with F.B.E on a British gas pipeline
under construction?

No.

5. Is it permissible to Bgas specification to gunite a pipe if the pipe is coated with

F.B.E?

No.

6. How would urethane coatings be removed if required?

Abrade the area by blast cleaning.

7. How wide is the band of epoxy powder coating when applied in the field?

Joint area + 30 mm on to the existing coating either side.

8. What do you understand by the terms Tg1 and Tg2 in relation to a DSC scan?

DSC – Differential-scanning calorimetry is a method used to determine the thermal

characteristics of epoxy powder and coating, and the information obtained from the test gives
us the degree of cure. DSC traces produced from the production coating should show that
Tg2 is within -2c and +5c of Tg1.

9. What is the acceptance tolerance related to Tg1 and Tg2?

Tg2 is -2c and +5c of Tg1.

10. What do you understand by the terminology residual exothermal in relation to DSC?

DSC – Thermal characteristics of epoxy powder.

Exothermal – Heat released during the reaction.
The potential heat energy involved in the coating for the degree of cure.

11. What do you understand by the terminology endothermic reaction?

Heat absorbed during the reaction.

12. What are the following abbreviations MIBK & DSC?

MIBK – Methyl iso butyl ketone.

DSC – Differential scanning calorimetry.

13. Name an epoxy powder application company approved by Bgas.

Raychem and canusa.

14. Is it possible to ditch F.B.E coated pipe during hot weather?

No.

Page 25 of 30
15. What are hygroscopic salts?

A salt which absorbs moisture from the atmosphere.

16. What does BGC PS SCW4 relate to?

Polyethylene cladding on steel pipe.

17. What is Plasgard 410?

Multi compound liquid mixed (two-pack or three-pack) to make one component. Has limited
pot life approximately 30 min.

18. What is Interpon quickset?

Two – pack repair kit, mixed in equal amounts so as to blend to colours into one colour.

19. What is fluidized bed used for?

For coating purpose.

20. How far from the end of the pipe does the factory epoxy powder coating terminate when
applied in accordance with BGC PS CW6 part 2?

500 mm.

21. Sketch an epoxy powder coating set up used on pipelines showing blasting, heating
coating operations.

22. Why is it not good practice to apply epoxy powder coatings too thick?

To avoid differential curing, application is done by layer passes.

Page 26 of 30
23. The epoxy powder material used on the BGAS pipelines shall be in accordance with
which specifications.
BGC PS CW6

24. What are potassium ferricyanide test papers used for?

To determine the presence of any colourless ion salts which may be present in the skin. This
test is carried out immediately after blast cleaning.

25. If it is required to overcoat epoxy powder coatings e.g. with a paint system on an
A.G.I what preparation must be undertaken and why?

Degrease, abrade and recoat

11. CATHODIC PROTECTION

1. Name two methods of applying cathodic protection.

1. Sacrificial anodes.
2. Impressed current.

2. Why does an uncoated steel pipe corrode?

1. Due to oxidation.
2. Metal iron reduction.
3. Variations in oxygen content on the material surface.

3. Name the type of reference electrode used by Bgas to measure pipe to earth potential.

Copper / copper sulphate half-cell reference electrode is used.

4. Why should magnesium anodes be used rather than zinc anodes with sacrificial C.P.
system?

Where soil resistivity is high magnesium anodes are usually used. Nobility of zinc is
less whereas magnesium is ignoble.

5. Is it possible to apply too much cathodic protection? If so what effect does this have?

It is possible for the cathodic protection to be too great i.e. the pipe can be over
negative. This can cause excessive amounts of hydrogen gas to be given of from the
metal substrate resulting in coating disbondment known as cathodic disbondment.
The more negative the pipe, the more hydrogen gas evolved.

6. What effect on C.P. would a foreign structure have if it comes into contact with the
pipe?

Stray effects.

7. What is the another name of sacrificial anode system works?

Galvanic anodes.

Page 27 of 30
8. Is it necessary to coat C.P. plates?

No.

9. Explain briefly how the sacrificial anode system works.

Sacrificial anodes are ignoble with respect to the pipeline i.e. if they are attached to a pipeline
via a cable, the anodes corrode first before corrosion of the pipe occurs. Sacrificial anodes
need to be replaced after the useful life.

10. Explain briefly how the impressed current system works.

This system is used to protect large area of pipeline e.g. ten miles in length from one C.P.
installation. Voltage from an external power source called 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
material is subjected to corrosion. Voltage output is between 10 to 50 volts.

11. What is an electrolyte?

An electrolyte which provides an electrical pathway from anode to cathode outside of the
metal.

12. What types of anodes are used on the impressed current systems?

Silicon ion, magnetite or graphite anodes.

13. Name three promoters of corrosion.

1. Oxygen reduction in acid solution, neutral, alkaline.

2. Metal ion reduction.
3. Hydrogen evolution.
4. Metal deposition.

14. Express 0.85V in mV, then explain the significance of this figure in relation to
Cathodic protection.

850 mV. It is international figure in C.P. system.

15. What is ground bed?

Buried earth connections are known as ground beds. Ground beds may consist of
approximately six silicon ion magnetite or graphite anodes buried in a surround of
carbonaceous backfill.

16. What work is carried out at the intersection were foreign pipeline crosses a pipeline to
which cathodic protection is being applied and why?

Stray current effects, connect the interfering structures to the protected structures
with an electrical resistor or resistance bond. Other metal structure near to the ground
Page 28 of 30
 bed may cause cathodic protection to flow in an unpredictable fashion possibly to
structures other than the structures being protected.

17. Is corrosion eliminated with cathodic protection?

Yes.

18. Is it possible to use graphite anodes to protect a buried steel pipeline?

Yes.

19. Is it a good practice to bury the pipeline to be cathodically protected in a carbonaceous

backfill?

Yes.

20. What is interference?

Stray current effects are known as interference. Other metal structures near to the ground bed
may cause C.P. currents to flow in an unpredictable fashion.

21. What is the cause of cathodic disbondment?

If the impressed current is greater than the corrosion current then cathodic disbondment may
result. This can cause excessive amounts of hydrogen gas to be given of from the metal
substrate resulting in cathodic disbondment. The gas generated pushes the coating from the
surface and causes adhesion failure beneath the edges of coating.

22. What is a transformer rectifier and its function?

Voltage from an external power source called a transformer rectifier is impressed on the
circuit between the pipeline and buried earth connection known as ground beds resulting in a
direct current being discharged.

23. What adverse conditions would cause the amperage and voltage output to be adjusted
on an impressed current C.P. system?

Current used is dependent on the quality of coating, typical amperage is 0.15 amps
but it may be much higher or lower. The greater the soil resistivity greater is the driving
voltage or number of anodes required to achieve C.P.

24. What is an isolation (insulation) joint used for?

Isolation or insulating joints will be encountered on cathodically protected pipelines; they are
special fittings implemented where it is necessary to electrically isolate the underground pipe
work from pipe work etc., which adversely affects the cathodic protection C.P. system.

25. Why is it not possible to cathodically protect an A.G.I.? What is A.G.I.?

A.G.I – Above ground installation.

Isolation joints or flanged joints are particularly necessary at below / above ground positions
at A.G.I.’s. This is because there is no electrolyte for the current to flow above ground and
also electrical interference can occur from lightening etc., present on A.G.I.
Page 29 of 30
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