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Characteristic
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Requirement
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Reference
standard
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1
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Design of coating system
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| .1
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Selection of the coating
system
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The selection of the coating system
should be considered by the parties involved with respect to the service
conditions and planned maintenance. The following aspects, among other
things should be considered:
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.1 location of space relative to heated surfaces;
.2 frequency of ballasting and deballasting
operations;
.3 required surface conditions;
.4 required surface cleanliness and dryness;
.5 supplementary cathodic protections, if any (where
coating is supplemented by cathodic protection, the coating should be
compatible with the cathodic protection system).
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| Coating manufacturers shall have
products with documented satisfactory performance records and technical data
sheets. The manufacturers should also be capable of rendering adequate
technical assistance. Performance records, technical data sheet and
technical assistance (if given) shall be recorded in the Coating Technical
File.
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| Coatings for application underneath
sun-heated decks or on bulkheads forming boundaries of heated spaces shall
be able to withstand repeated heating and/or cooling without becoming
brittle.
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| .2
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Coating type
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Epoxy based
systems.
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| Other coating systems with performance
according to the test procedure in annex 1.
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| A multi-coat system with each coat of
contrasting colour is recommended.
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| The top coat shall be of a light
colour in order to facilitate inservice inspection.
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| .3
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Coating
pre-qualification test
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Epoxy based systems tested prior to
the date of entry into force of this Standard in a laboratory by a method
corresponding to the test procedure in annex 1 or equivalent, which as a
minimum meets the requirements for rusting and blistering; or which have
documented field exposure for 5 years with a final coating condition of not
less than “GOOD” may be accepted.
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| For all other systems, testing
according to the procedure in annex 1, or equivalent, is required.
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| .4
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Job
specification
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There shall be a minimum of two stripe
coats and two spray coats, except that the second stripe coat, by way of
welded seams only, may be reduced in scope where it is proven that the NDFT
can be met by the coats applied in order to avoid unnecessary over
thickness. Any reduction in scope of the second stripe coat shall be fully
detailed in the CTF.
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| Stripe coats shall be applied by
brush or roller. Roller to be used for scallops, ratholes, etc.
only.
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| Each main coating layer shall be
appropriately cured before application of the next coat, in accordance with
coating manufacturer’s recommendations. Surface contaminants such as rust,
grease, dust, salt, oil, etc. shall be removed prior to painting with proper
method according to the paint manufacturer’s recommendation. Abrasive
inclusions embedded in the coating shall be removed. Job specifications
shall include the dry-to-recoat times and walk-on time given by the
manufacturer.
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| .5
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NDFT (nominal total dry film
thickness)
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NDFT 320 μm with 90/10 rule for epoxy
based coatings, other systems to coating manufacturer’s
specifications.
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Type of gauge and
calibration in accordance with SSPC-PA2
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Maximum total dry film thickness
according to manufacturer’s detailed specifications.
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Care shall be taken to avoid
increasing the thickness in an exaggerated way. Wet film thickness shall be
regularly checked during application.
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Thinner shall be limited to those
types and quantities recommended by the manufacturer.
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| 2
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PSP (Primary surface preparation)
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| .1
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Blasting and
profile
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Sa 2˝; with profiles between 30-75
μm.
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ISO 8501-1,
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| Blasting should not be carried out
when:
.1 the relative humidity is above 85%; or
.2 the surface temperature of steel is less than 3°C
above the dew point.
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ISO 8503-1/3
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| Checking of the steel surface
cleanliness and roughness profile should be carried out at the end of the
surface preparation and before the application of the primer, in accordance
with the manufacturer’s recommendations.
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| .2
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Water soluble salt limit equivalent to
NaCl
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≤ 50 mg/m2 of sodium
chloride.
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Conductivity measured in accordance
with ISO 8502-9
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| .3
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Shop primer
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Zinc containing inhibitor free zinc
silicate based or equivalent.
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| Compatibility with main coating
system shall be confirmed by the coating manufacturer.
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3
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Secondary surface preparation
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| .1
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Steel condition
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The steel surface should be prepared
so that the coating selected can achieve an even distribution at the
required NDFT and have an adequate adhesion by removing sharp edges,
grinding weld beads and removing weld spatter and any other surface
contaminant in accordance with ISO 8501-3 grade P2.
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ISO 8501-3
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| Edges to be treated to a rounded
radius of minimum 2 mm, or subjected to three pass grinding or at least
equivalent process before painting.
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| .2
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Surface
treatment
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Sa 2˝ on damaged shop primer and
welds.
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ISO 8501-1
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| Sa 2
removing at least 70% of intact shop primer, which has not passed a
pre-qualification certified by test procedures in .1.c.
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| If the
complete coating system comprising epoxy based main coating and shop primer
has passed a pre-qualification certified by test procedures in .1.c, intact
shop primer may be retained provided the same epoxy coating system is used.
The retained shop primer shall be cleaned by sweep blasting, high pressure
water washing or equivalent method.
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| If a zinc
silicate shop primer has passed the pre-qualification test of .1.c as part
of an epoxy coating system, it may be used in combination with other epoxy
coatings certified under .1.c, provided that the compatibility has been
confirmed by the manufacturer by the test in accordance with paragraph 1.7
of appendix 1 to annex 1 without wave movement.
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| .3
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Surface treatment after
erection
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Butts St 3
or better or Sa 2˝ where practicable. Small damages up to 2% of total area:
St 3. Contiguous damages over 25 m2 or over 2% of the total area
of the tank, Sa 2˝ should be applied.
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ISO 8501-1
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| Coating in
overlap to be feathered.
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| .4
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Profile
requirements
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In case of
full or partial blasting 30-75 μm, otherwise as recommended by the coating
manufacturer.
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ISO
8503-1/3
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| .5
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Dust
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Dust
quantity rating “1” for dust size class “3”, “4” or “5”.
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ISO 8502-3
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| Lower dust
size classes to be removed if visible on the surface to be coated without
magnification.
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| .6
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Water
soluble salts limit equivalent to NaCl after blasting/ grinding
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≤ 50
mg/m2 of sodium chloride.
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Conductivity measured in accordance with ISO 8502-9
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| .7
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Oil
contamination
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No oil
contamination.
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4
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Miscellaneous
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| .1
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Ventilation
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Adequate
ventilation is necessary for the proper drying and curing of coating.
Ventilation should be maintained throughout the application process and for
a period after application is completed, as recommended by the coating
manufacturer.
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| .2
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Environmental conditions
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Coating
shall be applied under controlled humidity and surface conditions, in
accordance with the manufacturer’s specifications. In addition, coating
shall not be applied when:
.1 the relative humidity is
above 85%; or
.2 the surface temperature is less
than 3°C above the dew point.
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| .3
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Testing of
coating
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Destructive
testing should be avoided.
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ISO 19840
Annex 3
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| Dry film
thickness shall be measured after each coat for quality control purpose and
the total dry film thickness shall be confirmed after completion of final
coat, using appropriate thickness gauges.
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| .4
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Repair
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Any
defective areas, e.g. pin-holes, bubbles, voids, etc. should be marked up
and appropriate repairs effected. All such repairs shall be re-checked and
documented.
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