1
MATERIALS
Centrifugal Casting of tanks is not allowed.
Tanks shall be filament wound or contact molded conforming to the following
appropriate ASTM specifications:
Filament Wound Tanks shall be designed and
fabricated in accordance with ASTM Specification D3299-08, "Filament-Wound
Glass-Fiber-Reinforced Thermoset Resin Chemical-Resistant Tanks".
Contact Molded Tanks shall be designed and
fabricated in accordance with ASTM Specification D4097-01, "Contact-Molded
Glass-Fiber-Reinforced Thermoset Resin Chemical-Resistant Tanks".
Tanks shall be as manufactured by a
certified FRPI (Fiberglass Reinforced Plastic Institute) fabricator.
1.1
Resin - The resin used shall be a commercial grade, premium,
corrosion resistant vinyl ester that has been evaluated in a laminate by
test in accordance with ASTM C-581 in Sodium Hypochlorite service comparable
to the intended service and recommended for this service by the resin
manufacturer.
The tank manufacturer shall strictly adhere
to the resin manufacturer's recommendations for surface veil materials,
resin cure systems, and post cure requirements.
1.1.1
The resin shall contain no pigments, dyes, colorants, or fillers
except as follows:
1.1.1.1
A Thixotropic agent that does not interfere with visual inspection of
laminate quality may only be added for viscosity control in resins that are
not to be used in the inner corrosion barrier, interior layers, interior
secondary layers, and interior top coats.
1.1.1.2
Resin pastes used to fill crevices may contain Thixotropic agents
provided that all such areas are subsequently covered with a full
corrosion-resistant barrier laminate.
1.1.1.3
A pigmented exterior gel coat must be provided on any tank to
be installed outdoors to reduce ultraviolet decomposition of the Sodium
Hypochlorite. Note: It is the responsibility of the specifier to identify
outdoor installations. Ultraviolet absorbers shall be added to the
exterior surface for improved weather resistance on indoor tanks as well
since tanks may be outdoors during construction and installation periods.
1.1
Reinforcement
1.1.1
Chopped Strand Mat - Chopped strand mat shall be constructed from
commercial grade E-type glass strands bonded together using a binder. The
strands should be treated with a sizing that is chemically compatible with
the resin system used.
1.1.2
Continuous Roving - Continuous roving shall be a commercial-grade of
E-type glass fiber with a sizing that is chemically compatible with the
resin system used.
Continuous roving for chopping in spray-up
process shall be principally silane finished with as little chrome compounds
as practical to achieve chopper performance while maintaining visual
laminate clarity requirements.
1.1.3
Woven Roving - Woven roving shall be in accordance with ASTM
Specification.
Note:
Based on Justin's experience with most premium corrosion-resistant resins
and their inherent cure characteristics and shop handling qualities, we
suggest the following for Sodium Hypochlorite service.
·
Approved Premium Vinyl ester
resin - BPO/DMA cured inner corrosion barrier with 2 ply synthetic surface
veil (Nexus-Burlington Industries)
The laminate construction section that follows is premised on the resin
system suggestions above.
2
LAMINATE
CONSTRUCTION REQUIREMENTS
Structural Tank - The laminate comprising
the structural tank (bottom, cylindrical shell, top head) shall consist of a
corrosion-resistant barrier comprised of an inner surface, interior layer,
and a structural layer. The tank
bottom shall be integral with the bottom tank shell. No tank bottom
attachment joints (external or internal) are allowed. No patched or
repaired hole in the center of the tank bottom resulting from tooling or
fixture support.
2.1.1
Inner Surface - The inner surface exposed to the chemical environment
shall be a resin rich 0.015 to 0.030 inches thick, reinforced with 2 ply of
synthetic fiber surface mat such-as Nexus (Burlington Industries) or
approved equal.
2.1.2
Interior Layer - The inner surface layer exposed to the corrosive
environment shall be followed with a layer composed of resin, reinforced
only with noncontiguous glass-fiber strands applied to a minimum thickness
of 0.100 inches. The combined thickness of the inner surface and interior
layer shall be 0.115 to 0.130 inches and in no case less than 0.110 inches.
2.1.2.1
Glass content of the inner surface and interior layer combined shall
be 27% + 5% by weight.
2.1.2.2
Resin used in these layers shall be Derakane 411, Derakane 510C, AOC
F010, AOC K022 or approved equal incorporating a BPO/DMA cure system as
recommended by the manufacturer.
2.1.2.3
The degree of cure, after post cure (see Section 4) shall be such as
to exhibit a Barcol hardness on the inner surface of at least 90% of the
resin manufacturer's minimum specified hardness for the cured laminate with
a synthetic surface mat.
2.1.3
Structural layer:
2.1.3.1
Filament Wound Structural Layer - Subsequent reinforcement shall be
continuous-strand roving in accordance with 1.2.2, that in combination in
2.1.1 & 2.1.2 is needed to satisfy the design requirements. Glass content of
this filament-wound structural layer shall be 50 to 80% by weight. Only
those constructions evaluated for design properties shall be used.
2.1.3.2
Contact Molded Structural Layer - Subsequent reinforcement shall be
comprised of 1.5 oz/ft2 chopped strand mat or equivalent weight
of chopped roving, or shall be comprised of chopped strand mat or chopped
roving and such additional number of alternating plies of 24 oz/yd2
woven roving to a thickness as required to meet the physical properties that
are used for the design. Each successive ply or pass of reinforcement shall
be well rolled prior to the application of additional reinforcement. Where
woven rovings are used, chopped strand glass reinforcement shall be used as
alternating and final layers. All woven roving and chopped strand shall be
overlapped. Laps in subsequent layers shall be staggered at least 2.25
inches from laps in the preceding layer.
2.1.3.3
Resin used in the structural layer shall be the same as used in the
inner surface and interior layers except that the BPO/DMA cure system is not
required. Other generic types of resin such as Isophthalics or
general-purpose resins shall not be used.
3
FITTINGS
AND MANWAYS
3.1
Manways - All closed top tanks shall be provided with a minimum 24
inch diameter flanged manway with bolted cover. All tanks with a straight
shell height greater than 12 feet shall be provided with a minimum 24-inch
diameter flanged side manway with bolted cover. Bolted manways shall be
provided with 1/8 inch thick full-face EPDM gaskets and 316 Stainless Steel
bolting.
Manway stub flange and cover shall be hand
lay-up construction with the inner surface and interior layer using the BPO/DMA
cured resin system.
3.2
Flanged Nozzles - All flanged nozzles shall be of hand lay-up
construction with the pipe stub molded integrally with the pipe flange.
Compression molded or cemented on flanges is prohibited. The resin used for
the inner surface and interior layer of flanged stubs shall be the BPO/DMA
cured resin system. Nozzles 4 inch diameter and smaller shall be gusseted
conically or with four (4) 3/8 inch thick plate gussets.
3.3
Installation of all manways and flanged nozzles shall be the
flush-type per ASTM D3299 or D4097. Penetrating-type installation is not
recommended in Sodium Hypochlorite service. Nozzles less than 1½”
diameter should not be used.
3.4
All interior overlays of nozzles, manways, and other internal
accessories shall incorporate the BPO/DMA cured resin system.
3.5
Threaded Fittings - Threaded fittings shall not be used in
Sodium Hypochlorite service.
4
POST
CURE
4.1
The completed tank shall be post cured with dry heat in accordance
with the resin manufacturer's recommendations. Any internal repairs or
rework must be completed prior to post curing. If repairs are made following
post cure, an additional post cure cycle is required.
TIPS FOR LONGER SERVICE LIFE
1.
Maintain storage temperature below the decomposition point for the
Hypochlorite
solution being stored (generally below
125°F).
2.
Avoid ultraviolet exposure, which tends to decompose Hypochlorite.
Install tanks indoors or specify a pigmented exterior gel coat to reduce
ultraviolet exposure potential.
3.
Maintain the pH above 10. pH levels below 10 are a possible
indication of decomposition of the Hypochlorite.
4.
If generating Hypochlorite in the tank:
►
Control pH at above 10.
►
Do not over chlorinate. (Total chlorination should not exceed 15%)
►
Control temperatures below 125°F.
5.
If decomposition of the Hypochlorite stored is suspected:
►
Empty the tank as quickly as practical through normal usage. If normal
consumption will not empty the tank in 30 to 60 days, arrangements should be
made to empty the tank.
►
Rinse the tank thoroughly.
►
Inspect the interior through the manway, (or by getting inside - when it's
safe) for evidence of attack, such as loss of gloss, discoloration, mud
cracking, or build-up of yellowish residue.
►Consult
the manufacturer or the resin supplier.
All information , recommendations &
suggestions appearing in this literature concerning the use of our products
are based upon tests and data believed to be reliable; however, it is the
user’s responsibility to determine the suitability for his own use of the
products described herein. Since the actual use by others is beyond our
control, no guarantee, expressed or implied, is made by Justin Tanks LLC as
to the effects of such use or the results to be obtained, nor does
Justin Tanks LLC assume any liability arising out of use, by others, of the
products referenced to herein. Nor is the information herein to be construed
as absolutely complete, since additional information may be necessary or
desirable when particular or exceptional conditions or circumstances exist
or because of applicable laws or government regulations. Nothing herein
contained is to be construed as permission or as a recommendation to
infringe any patent.
