APPLICATION METHODOLOGY OF COAL TAR TAPE & COAT PRIMER
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STORAGE AT SITE: COAL TAR TAPE SHALL BE STORED
UNDER SHED VERTICAL POSITION; IT SHALL BE STORED IN SINGLE OR DOUBLE ROLL LAYER
1.
SURFACE
PREPARATION
a.
All bare steel shall be free of dust, dirt,
grease, oil and other foreign matter; practical removal can be done by either
power or hand wire brushing. grease and oil can be removed by use of a solvent that leaves no oily or dust film
remaining on the steel surface
b.
Welds shall be cleaned of all welding slag,
splatter, and scale. Sharp edges or burrs shall be removed by grinding or
filing.
c.
The weld shall be no more than “warm to the
touch” before priming and taping.
d.
Moisture, if present, shall be removed before
priming and taping.
2.
PRIMER
APPLICATION
a.
After proper surface preparation, him coat
primer shall be stirred and applied sparingly in a uniform continuous method to
the steel surface.
b.
Application may be by brush or roller.
c.
Primer shall be dry to touch but tacky before
applying coal tar tape.
d.
No foreign matter shall come in contact with the
primed surfaces prior to applying coal tar tape.
e.
Priming application shall be limited to that
amount of pipe that can be wrapped during the same workday, when primer surface
is tacky otherwise the steel must be re-primed. Re-priming may not take place
until all dust and other foreign matter has been removed. In addition the
surface must be dry before re-priming.
3.
TAPE
APPLICATION
a.
Tape shall be used to coat all miscellaneous
pipe delivered bare to the field such as, but not limited to, bends, elbows, cut-outs,
straight runs, welded joints and patching of the factory applied coating.
b.
Tape roll shall be kept under sun for one hour
before opening of tape roll to avoid cracking.
c.
Proper application of coal tar tape is obtained
by use of a propane torch with a wide mouth burner head. A LE-100 magnum torch
id recommended. coal tar tape is applied after coating surface preparation and
priming by heating the coating side – not the film sid- lightly with the propane torch to obtain a softening of
the pitch, causing the tape should be heated that will remain in a semi liquefied
state during application. Application proceeds, alternately heating the coating
side and wrapping with minimum overlap until the entire surface is coated.
i.
if a 55% overlap of material is required (for a
total of approximately 116 mils – layers) the application proceeds, alternately
heating and flashing with torch to the film of the first layer of tape that has
been applied and wrapping with a 55% overlap until the entire surface is
coated.
ii.
Where the plastic film has been flashed our
(ref: 3.3.1) the layer may have residual melted plastic film on the surface of
the tape – this is acceptable. in addition, as the plastic film is not
necessary to flash off the final layer of plastic film on the wrap.
iii.
For welded joints the taping that the tape
conforms to the “cut back” of the factory coating and the weld area. No voids
or wrinkles caused by improper application is allowed.
d.
The repair and patching of the coating is made
by removing all loose disband material from around the area of the “holiday”. No
sharp points, burrs, or rough edges shall be “feathered” smooth, prior to
application of the primer and tape.
4.
STORAGE
HANDLING AND SHIPPING
a.
Coated pipe shall be handled and stored in such
a manner as to prevent damage to the coating
b.
All booms, hooks, forks, supports, skids and
other devices used to move and handle coated pipe shall be padded to prevent
damage to the coating.
c.
Pipe shall be shipped using sufficient padding
and dunning to adequately protect the pipe coating chains and steel bands shall
not be used.
5.
BACKFILL
a.
Backfill adjacent to the coated pipe shall be
free of scrap, sticks, large stones, rocks or debris which would tend to damage
the coating.
