12P e4 PP2 fm Specification for Fiberglass Reinforced Plastic Tanks API SPECIFICATION 12P FOURTH EDITION, FEBRUARY 2016 EFFECTIVE DATE AUGUST 1, 2016 Special Notes API publications necessarily address[.]
General
This specification outlines the requirements for the material, design, fabrication, and testing of fiberglass-reinforced plastic (FRP) tanks It specifically addresses shop-fabricated, vertical, cylindrical tanks intended for aboveground use and atmospheric pressure service, while excluding unsupported cone bottom tanks from its scope.
This specification outlines standard sizes of FRP tanks for the petroleum industry Due to the versatility of FRP tanks, users must assess their suitability for specific applications.
When considering the use of FRP tanks, it is crucial to acknowledge the impact of high temperatures from exposure fires, as these can significantly weaken the material To mitigate risks, FRP tanks must be adequately protected from fire exposure or positioned in a manner that prevents spills from endangering people, buildings, structures, or other equipment in the event of a failure.
Compliance
The manufacturer must adhere to all provisions outlined in this specification, while the purchaser is tasked with clearly defining their specific requirements in the Data Sheet Additionally, the purchaser has the right to conduct any necessary investigations to ensure the manufacturer's compliance and may reject any materials that do not meet the specified standards.
Purchasers are advised to conduct their own inspections, in addition to the manufacturer's provided inspection It is essential for the purchaser's inspector to closely monitor all specified details of shop fabrication and testing that impact the integrity and safety of the final structure.
1.2.2 If specified by the purchaser on the Data Sheet, the tank shall be constructed in accordance with API Q1 and the API Monogram Program (see Annex A).
1.2.3 This specification applies to new tanks The requirements may be applied to existing tanks at the discretion of the owner/operator.
The documents referenced herein are essential for the application of this document For references with specific dates, only the cited edition is applicable In the case of undated references, the most recent edition of the referenced document, including any amendments, is relevant.
API Recommended Practice 545, Recommended Practice for Lightning Protection of Aboveground Storage Tanks for
API Standard 2000, Venting Atmospheric and Low-pressure Storage Tanks
API Recommended Practice 2003, Protection Against Ignitions Arising Out of Static, Lightning, and Stray Currents AISC 1 Steel Construction Manual
1 American Institute of Steel Construction, One East Wacker Drive Suite 700, Chicago, IL 60601-1802, www.aisc.org.
ASCE 7 2 , Minimum Design Loads for Buildings and Other Structures
ASME B1.1 3 , Unified Inch Screw Threads, UN and UNR Thread Form
ASME B16.5, Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard
ASTM A36/A36M 4 , Standard Specification for Carbon Structural Steel
ASTM A153, Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware
ASTM A193/A193M, Standard Specification for Alloy-Steel and Stainless Steel Bolting for High Temperature or High
Pressure Service and Other Special Purpose Applications
ASTM A307, Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod 60000 PSI Tensile Strength ASTM A325, Standard Specification for Structural Bolts, Steel, Heat Treated, 120/105 ksi Minimum Tensile Strength
ASTM A325M, Standard Specification for Structural Bolts, Steel, Heat Treated 830 MPa Minimum Tensile Strength
ASTM B695, Standard Specification for Coatings of Zinc Mechanically Deposited on Iron and Steel
ASTM C581, Standard Practice for Determining Chemical Resistance of Thermosetting Resins Used in Glass-Fiber-
Reinforced Structures Intended for Liquid Service
ASTM D638, Standard Test Method for Tensile Properties of Plastics
ASTM A563, Standard Specification for Carbon and Alloy Steel Nuts
ASTM D790, Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical
ASTM D2583, Standard Test Method for Indentation Hardness of Rigid Plastics by Means of a Barcol Impressor ASTM D2584, Standard Test Method for Ignition Loss of Cured Reinforced Resins
ASTM D2990, Test Methods for Tensile, Compressive, and Flexural Creep and Creep-Rupture of Plastics
ASTM D3299, Standard Specification for Filament-Wound Glass-Fiber-Reinforced Thermoset Resin Corrosion-
ASTM D4097, Standard Specification for Contact-Molded Glass-Fiber-Reinforced Thermoset Resin Corrosion-
ASTM F436, Standard Specification for Hardened Steel Washers
ASTM F844, Standard Specification for Washers, Steel, Plain (Flat), Unhardened for General Use
2 American Society of Civil Engineers, 1801 Alexander Bell Drive, Reston, VA 20191, www.asce.org.
3 ASME, Two Park Avenue, New York, NY 10016-5990, www.asme.org.
4 ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428, www.astm.org.
SPI E-1067 6 , Recommended Practice for Acoustic Emission Examination of Fiberglass Tanks/Vessels
U.S Government, 29 CFR Section 1910, General Industry Regulations, OSHA 8
For the purposes of this document, the following definitions apply.
The FRP composite is created through a unique combination of chop-spray and filament winding techniques, which work together to enhance its properties This innovative process leverages the directional strength of glass from filament winding while incorporating a higher resin content from chop-spray, resulting in improved corrosion protection for the reinforcement.
Continuous strand glass roving and catalyzed resin are processed through a chopper gun that cuts the fiberglass into adjustable lengths on-site This chopper gun applies the resin-saturated fiberglass onto the mold, where the laminate is rolled to ensure complete saturation and compaction of the glass strands Additional layers of chopped laminate are added as needed to achieve the desired thickness.
The required thickness must meet the tension and compression strength criteria outlined in this Specification, or, in the absence of such criteria, adhere to sound engineering practices for the specified design conditions, without considering construction limitations or corrosion allowances.
Fiber-reinforced plastic composites consist of a polymer matrix resin, commonly known as plastic, which includes thermoset resins like polyester, isopolyester, vinyl ester, epoxy, and phenolic These composites are enhanced with fiber reinforcements such as glass, carbon, aramid, or other materials to improve their strength and durability.
Filament winding is an automated open molding technique that utilizes a rotating mandrel as the mold, creating a finished inner surface and a laminate exterior This process achieves a high degree of fiber loading, resulting in exceptional tensile strength for hollow, cylindrical products like chemical and fuel storage tanks, pipes, stacks, and pressure vessels.
The person(s) designated by the purchaser or manufacturer to perform inspections.
5 International Code Council, 500 New Jersey Avenue, NW, 6th Floor, Washington, DC 20001, www.iccsafe.org.
6 Society of the Plastics Industry, 1425 K Street NW., Suite 500, Washington, DC 20005, http://www.plasticsindustry.org.
7 The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, PA 15222, www.sspc.org.
8 U.S Department of Labor, Occupational Safety and Health Administration, 200 Constitution Avenue, NW, Washington, DC
When a specification is adopted by a legal jurisdiction or referenced on a manufacturer's nameplate or certification, its required sections become mandatory.
The party having the primary responsibility to construct the tank.
The owner, owner’s engineer, or operator who specifies the tank Data Sheet for the purchase.
A choice to be selected by the purchaser and indicated on the Data Sheet When the purchaser specifies an option covered by an annex, it then becomes a requirement.
Criteria that provides a good/acceptable design and may be used at the option of the purchaser and the manufacturer.
General
Tanks manufactured to this specification utilize composite materials made from thermosetting polymers reinforced with glass fibers Acceptable polymer resins include polyester, epoxy, and vinyl ester resins It is essential for the purchaser to specify the exact material on the Data Sheet, especially if there are specific conditions, such as extreme temperatures, that may influence material selection.
Resin
4.2.1 The resin used shall be commercial grade thermosetting polymer and shall not contain fillers and pigments, except if specified by the purchaser on the Data Sheet.
Thixotropic agents utilized for viscosity control must not obstruct visual inspection and should be limited to a maximum of 5% by weight However, resin paste or putty employed to fill crevices prior to overlay is exempt from these restrictions.
To mitigate the effects of prolonged exposure to ultraviolet radiation, such as surface chalking and discoloration, it is essential to incorporate one or more of the following solutions: a UV absorber in the resin at a concentration of 0.1 to 0.3 weight percent, pigment in the outer resin layers to enhance opacity, an external surface paint as detailed in the Data Sheet (refer to Annex D for further coating requirements), or a UV-inhibited gelcoat that is compatible with the underlying resin.
NOTE Additions of any of the above may interfere with visual inspection of laminate quality.
If indicated on the Data Sheet, antimony compounds or other fire retardant agents will be incorporated into the laminate to enhance fire resistance, ensuring that the final laminate complies with the specified physical properties.
Metal powders, carbon, and other conductive compounds enhance conductivity in laminates However, the inclusion of these materials can hinder visual inspections and affect the physical properties of the laminate.
Resistance to hydrocarbon attack must be verified through testing as per ASTM C581 Additionally, tensile and flexural strength should be assessed at the specified temperature following ASTM D2990 The manufacturer or their agent is responsible for conducting these tests, maintaining records, and providing them to the purchaser upon request.
Reinforcing Material
Reinforcing materials must consist of commercial-grade E- or E-CR-type glass fiber, featuring a coupling agent that is chemically compatible with the resin employed The selected reinforcing material for tank fabrication should be the same as that used to establish the corrosion resistance and physical property design data specified in Section 4.
Surfacing Material
Reinforcing used on the inner surface shall comply with ASTM D3299.
Appurtenances
Woven roving used for reinforcement of knuckles, manways, and other appurtenances shall be tested in compliance with, and meet the requirements of, the most suitable industry standard.
Bolting Materials
See Annex C and the Data Sheet for requirements applicable to bolting materials.
General
5.1.1 The purchaser shall determine and specify the design and operating pressures on the Data Sheet The standard design is limited to:
— working pressure of 152.4 mm (6 in.) water column (0.217 psig or 1.496 kPa) with the static head of the stored fluid for the operating pressure, and
— vacuum condition of 50.8 mm (2 in.) water column (0.072 psig or 0.497 kPa).
This section addresses the design requirements for filament winding, chop-spray, and their combination methods, known as chop-hoop Tanks made with hand lay-up (contact molding) must meet the same standards as those constructed using chop-spray techniques All dimensions should adhere to the specifications outlined in Figure 2 and Table 1.
Shell Design—Chop-spray
The allowable shell design tensile stress (S_a) is set at 10% of the ultimate stress (S_u), which must be determined through ASTM D638 testing for each composite combination provided by the manufacturer This testing is required for all standard composite combinations and involves measuring the shell thickness, defined as the structural layer plus the exterior layer Test specimens must be made with resins that include all additives used in the final product If there are no revisions to ASTM D638, these tests can be conducted once, with the results maintained on file.
The minimum shell thickness must adhere to the design equation \( t = \frac{PD}{2S} \), ensuring it is not less than 4.8 mm (0.1875 in.) Here, \( t \) represents the minimum allowable shell thickness at the specified pressure point \( P \).
P is the pressure exerted by a combination of fluid head and gas blanket,
D is the inside diameter of the tank,
S a is the allowable shell design tensile stress.
Table 1—Tank Dimensions (See Figure 2)
Inside Diameter ft, in ± 1 /2 in.
Shell Height ft, in ± 1 /2 in.
Height of Overflow Line Connection ft, in ± 1 /8 in.
Height of Walkways Lugs ft, in ± 1 /8 in.
NOTE The approximate working capacities shown in Column 2 apply to flat-bottom tanks.
Shell Design—Filament Wound and Chop-hoop
Allowable design tensile stress (S a )is that stress which produces 0.001 mm/mm (in./in.) tensile strain according to the formula:
E is the tensile modulus of elasticity for the particular filament wound laminate in the direction of loading.
The modulus of elasticity and ultimate stress must be determined according to ASTM D638, with tests conducted for each composite combination used by the manufacturer Test specimens should include all additives present in the final product If the calculated value of \$S_a\$ exceeds 0.10 times the ultimate tensile stress, then \$S_a\$ is adjusted to \$S_a = 0.10 \times S_u\$ Additionally, the minimum shell thickness is calculated using Equation (1) and must not be less than 4.8 mm (0.1875 in).
Shell Design—Laminate Construction
The laminate comprising the structural components (bottom, cylindrical shell, and roof) shall consist of an inner surface, interior layer, structured layer, and an exterior layer.
The inner surface must consist of reinforced resin-rich material with a thickness ranging from 0.254 mm to 0.508 mm (0.010 in to 0.020 in.), featuring either a chemical-resistant glass fiber surface veil or an organic fiber surface veil as detailed in the Data Sheet The manufacturer is required to supply documentation confirming that the material used for the inner surface layer is appropriate for the specified fluid in the Data Sheet, ensuring that the resin-rich surface contains less than 20% by weight of reinforcing material.
To prevent weeping, the inner surface exposed to corrosive environments must be coated with a resin layer reinforced with non-continuous glass-fiber strands This should consist of at least two layers of chopped-strand mat, totaling 0.92 kg/m² (3 oz/ft²), or alternatively, two passes of chopped roving with lengths between 12.7 mm (0.5 in.) and 50.8 mm (2 in.), also weighing 0.92 kg/m² (3 oz/ft²) Each layer must be rolled before adding more reinforcement, ensuring the combined thickness of the inner surface and interior layer is at least 2.03 mm (0.080 in.) Additionally, the glass content of both layers should be maintained at 27 ±5% by weight, as per ASTM D2584 standards.
5.4.4 Structural Layer (Chop-hoop, Filament Wound)
The structural layer will utilize continuous strand roving for reinforcement, ensuring it meets minimum strength requirements for various tank heights as outlined in Section 5.3 If further reinforcement is necessary, options such as woven fabric, unidirectional fabric, chopped-strand mat, or chopped strands can be incorporated into the winding to enhance strength The glass content of this structural layer will be maintained between 45%.
55 % for chop-hoop wound laminates and from 50 % to 80 % for filament wound laminates when tested in accordance with ASTM D2584.
As an alternative to section 5.4.4, subsequent reinforcement must include 0.46 kg/m² (1.5 oz/ft²) of chopped strand mat or an equivalent weight of chopped roving, along with alternating layers of 0.81 kg/m² (2.7 oz/ft²) woven roving and 0.46 kg/m² (1.5 oz/ft²) chopped strand mat, or equivalent chopped roving, to achieve the required thickness as per section 4.2 Each layer of reinforcement should be rolled before applying additional layers The glass content in this structural layer must be at least 35% when tested according to ASTM D2584 Additionally, alternating layers of directional reinforcement should overlap by a minimum of 38.1 mm (1.5 in.), with laps staggered at least 57.15 mm (2.25 in.) from one layer to the next.
The tank shell, bottom, and roof must feature an exterior layer made of chopped strand, chopped-strand mat, or surfacing mat, ensuring that no glass fibers are exposed Additionally, the resin used in this exterior layer must be resistant to ultraviolet degradation, in accordance with the specifications outlined in section 4.2.2.
Bottom Knuckle Radius Design
The bottom knuckle must be reinforced with a glass fiber and resin overlay that extends at least 304.8 mm (12 in.) upward from the flat bottom tangent line, with an additional thickness transition of 101.6 mm (4 in.) The reinforcement of the knuckle radius should taper to ensure it is tangent with the flat bottom and does not extend beyond the tangent line onto the tank bottom This reinforced perimeter must allow the bottom to uniformly contact a flat support surface when liquid is present inside the tank The minimum thickness of the radius section should equal the combined thicknesses of the bottom shell wall and the bottom, with a minimum acceptable knuckle radius of 2 in (50.8 mm), as illustrated in Figure 1.
Figure 1—Bottom Knuckle of Flat-bottom Tank
76 mm to 102 mm (3 in to 4 in.)
Bottom-to-Shell Joint (Chop-spray) Design
When fabricating tank bottoms and shells separately, the joint must consist of alternating layers of mat (or chopped strand) and 0.81 kg/m² (24 oz/yd²) woven roving, with a minimum overlay thickness equal to the tank shell thickness at the joint Reinforcement must comply with Section 6.5 of ASTM D4097, and the interior layer should include at least two layers of 0.46 kg/m² (1.5 oz/ft²) material The seal joint must have a minimum width of 152.4 mm (6 in.), and the inner surface should be sealed as per Section 5.4.
Bottom Strength
The minimum acceptable bottom thickness for fully supported flat or cone bottoms in tanks with a diameter of 3.66 m (12 ft) or less is 6.35 mm (0.25 in.), while for tanks exceeding this diameter, the minimum thickness increases to 9.52 mm (0.375 in.) Additionally, the construction of the bottom laminate must adhere to the specifications outlined in Sections 5.4, 5.4.2, 5.4.3, and 5.4.5.
Geometry
5.8.1 The roof configuration shall be:
— flanged or dished dome, or
— conical roof with 1:12 pitch or steeper.
The roof must support a concentrated load of 1.112 kN (250 lb) on any 101.6 mm × 101.6 mm (4 in × 4 in.) area without sustaining damage, ensuring a maximum deflection of 0.5% of the inside tank diameter Acceptable methods for achieving this include the use of stiffener ribs or sandwich construction stiffening systems.
Roof Laminate Construction
5.9.1 Roof laminate construction shall conform to Sections 5.4, 5.4.2, 5.4.3, and 5.4.5 The minimum roof thickness shall be 4.8 mm (0.1875 in.).
5.9.2 If the tank has a gas blanket installed, the purchaser shall consider the option of laminating the interior of the top roof seam (see Data Sheet, Annex D).
Cleanout
Cleanout or manway flange cover dimensions and bolting must adhere to the specifications outlined in Table 2 or ASTM D3299, Table 5 Additionally, the construction of cleanout flanged nozzles should comply with ASTM D3299, Table 4 It is essential that the bottom of the cleanout does not extend more than 304.8 mm (12 in.) below the tank's bottom Furthermore, the requirements detailed in Annex C are applicable to cleanout and manway bolting.
Nozzles
The tank will be equipped with the nozzles depicted in Figure 2, unless the purchaser specifies otherwise The dimensions and placement of these nozzles must adhere to the specifications outlined in Table 1 and Figure 2.
NOTE The configuration covered above is the default or standard design.
The purchaser may modify the orientation, size, and quantity of nozzles The nameplate marking shall denote the nozzle configuration See Section 8.
Nozzles must be female NPT, but purchasers can request alternative types like flanged, grooved, or male NPT on the Data Sheet Fittings C-1 and C-4 should feature a full coupling design for internal connections, including drain and inlet downcomers All nozzles are required to be of the glassed-in type.
Cutout Reinforcements
Cutouts for nozzles and cleanouts subjected to hydrostatic pressure must be reinforced in a circular area that is concentric with the cutout The required thickness of the reinforcement (T r) should be specified in millimeters or inches.
For nozzles with a nominal pipe size (NPS) of 6 or larger, the reinforcement factor \( K \) is set at 1.0 For smaller nozzles, \( K \) is calculated using the formula \( \frac{d}{d_r - d} \), where \( d \) represents the nozzle's outside diameter The reinforcement diameter \( d_r \) is determined as twice the outside diameter \( d \) for nozzles NPS 6 and above, while for those smaller than NPS 6, it is calculated as \( d + 6 \) inches.
P is the hydrostatic pressure at the point of nozzle installation;
D is the inside diameter of the tank;
S a is the allowable tensile stress (see 5.2.1).
For T r < 3.2 mm ( 1 /8 in.), no additional reinforcement shall be required other than the overlay for glassed-in nozzles.
Size a Diameter of Flange and Cover Thickness of Flange and Cover Diameter of Bolt
Bolt Hole Diameter mm (in.) mm (in ± 3 /32) mm (in ± 1 /32) mm (in ± 3 /32) mm (in ± 1 /32)
Side-shell Manway—Up to 15 psig (104 kPa) Hydrostatic Head
Roof Manway—Up to 0.5 psig (3.5 kPa) Static Head
610 (24) 813 (32) 10 ( 3 /8) 749 (29 1 /2) 20 13 ( 1 /2) a Bolt size = bolt hole diameter minus 3 mm ( 1 / 8 in.).
Figure 2—Closed Top FRP Tank Dimensions (See Table 1)
1016 mm (1 ft-0 in.) 305 mm (1 ft-2 in.) 356 mm
1 457 mm to 610 mm (18 in to 24 in.) circular cleanout (see Table 2)
9 optional gauge/thief-hatch cutout connection (see Figure 3)
12 glassed-in walkway bracket lugs
14 optional emergency relief vent connection
NOTE See Table 1 for connection sizes
Appurtenances
5.13.1 Nozzles, cleanouts, and other appurtenances shall be installed in accordance with 5.10 to 5.12 Installation laminates shall meet minimum standards shown in Figure 5 and Figure 6 of ASTM D3299.
5.13.2 FRP flanged nozzle construction and design shall conform to ASTM D3299, Table 4 Flange drilling and bolting shall conform to ASME B16.5 for Class 150 flat faced flanges.
5.13.3 All fittings below the liquid level shall be reinforced internally with at least two layers of 0.46 kg/m 2 (1.5 oz/ft 2 ) mat The inner surface shall be sealed according to 5.4.3.
5.13.4 For bolting requirements applicable to all appurtenances, see Annex C.
Walkway, Ladder, Lifting, Hold-down, and Tie-down Lugs
The manufacturer must conduct physical tests on a prototype to verify that all lifting lugs can support twice the tank's empty weight It is important that lugs are not installed using fasteners that penetrate the shell Additionally, the loads for walkways and ladders are detailed in Annex C.
If the purchaser specifies hold-downs (wind anchorage lugs), the manufacturer must calculate wind loads in accordance with ASCE 7 or IBC standards Additionally, the hold-down lugs must be installed on the tank in a manner that prevents them from extending below the tank's bottom surface.
When a safety tie down is required for field personnel on the tank roof, an anchor lug must be installed at a suitable location This anchor lug should comply with 29 CFR 1910 or an equivalent national standard Additionally, a tank lifting lug can serve as the tie down anchor if it is properly designed for this purpose.
Downcomer Pipe
A conductive downcomer pipe, with a spray deflector shall be installed if specified in the Data Sheet.
NOTE The downcomer pipe system is used to reduce the internal static build up caused by liquid splashing from the filling drop.
Gauge/Thief Hatches
Pressure and vacuum ratings for gauge, thief, or hatch must align with the specified design conditions Suggested bolt patterns for common flanges on gauge/thief hatch openings are illustrated in Figure 3 Additionally, a grounding lug must be installed on the hatch to ensure proper grounding, with a size suitable for attaching an AWG.
No 4 wire A striker plate consisting of a minimum of 4.8 mm × 406.4 mm × 406.4 mm (0.1875 in × 16 in × 16 in.) steel plate shall be laminated to the tank bottom directly below the gauge/thief hatch.
Manual gauging, which involves opening the gauge or thief hatch, poses personal safety risks due to potential gas exposure in the tank To reduce this risk, purchasers can implement a remote tank level gauging system utilizing technologies such as radar gauges, float valves, or level transmitters.
Design Considerations for Potential Electrostatic Hazards
Electrostatic hazards which might arise when filling or emptying FRP tanks may be divided into two types:
1) those due to the accumulation of a charge on the outside of the tank,
2) those due to the build-up of an electric field inside the tank.
All metal appurtenances on tanks must have a flexible bonding conductor to reduce hazards The gauge or thief hatch should be grounded to minimize risks, and any metallic walkways, stairways, or ladders linked to a fiberglass reinforced plastic (FRP) tank must also be connected to electrical ground.
To reduce the risk of charge accumulation in metal tanks, purchasers should consider various strategies Key methods include limiting flow rates until the filling pipe is submerged and using conductive metallic downcomers Additionally, employing conductive materials for tank construction that are properly grounded, as outlined in the Data Sheet, is essential It is crucial that all metal components in contact with the vapor space and liquid containment are bonded and grounded In extreme situations, a suspended conductor within the tank may be necessary.
Grounding
If specified in the Data Sheet the manufacturer shall provide a means to ground the interior fluid.
Current methods for grounding tanks include conductive downcomers suspended from electrically bonded connections at the tank roof, extending to the tank floor; conductive ground rods, either vertical or horizontal; carbon c-veil embedded on the internal shell surface of the tank; and a suspended static conductor within the tank.
API 2003 and API 545 provide more complete guidance to address static and lightning protection issues as they relate to tank installation and operation
Figure 3—Typical Gauge/Thief Hatch Opening
16 x 14 mm ( 17 / 32 in.) For 13 mm ( 1 / 2 in.) bolts
Normal Venting
Closed top tanks must be positively vented to the atmosphere, with Connection C-2 designated for normal inbreathing and outbreathing caused by temperature fluctuations and liquid movement This connection should be equal to or larger than the largest inlet or outlet connection and must be equipped with appropriately sized pressure-vacuum valves as per API 2000 standards Additionally, gauge/thief hatches and pressure/vacuum valves must comply with the specified design conditions.
Emergency Venting
The purchaser shall consider providing emergency venting for upset conditions This shall be addressed in the Data Sheet.
Emergency venting capacity is typically unnecessary for FRP tanks during an external tank fire, as these tanks generally fail at temperatures around 93.3 °C (200 °F) This failure temperature is reached before a significant amount of liquid vaporizes, thus preventing any venting issues.
Figure 4—Example of Suspended Static Conductor Bond to Grounding System
Carbon fiber Point discharge stainless steel brush
Fabrication
Tanks must be constructed using either the contact-molded or filament-wound process, adhering to ASTM D4097 for contact-molded tanks and ASTM D3299 for filament-wound tanks Both fabrication methods are acceptable, and if a combination of these methods is employed, the tank must comply with the relevant standards for each respective fabrication method used.
Joints between separately formed hoop sections of tanks must be created with an overlay that meets the minimum widths specified in ASTM D4097, Table 2, and should have an overlay thickness matching the required design shell thickness This overlay must taper back from the minimum thickness to align flush with the adjoining section over a width of at least 76 mm (3 in.) Additionally, the inner surface of the joint must be sealed according to section 5.4.3.
Tanks must be constructed according to the dimensions and tolerances specified in Table 1 The thickness of the shell, bottom, and roof must meet or exceed the requirements outlined in Section 5 Furthermore, the exterior surface of the shell should be free from any abrupt visual transitions or bulging.
The tank must be devoid of visual defects, including foreign inclusions, dry spots, air bubbles, pinholes, and delaminations Its internal surface should be smooth, without cracks or crazing, and may have no more than 2 pits per 0.093 m² (1 ft²) area Acceptable pits should be smaller than 3.2 mm (1/8 in.) in diameter and less than 0.8 mm in depth.
Pits measuring up to \$\frac{1}{32}\$ inch deep are acceptable if adequately covered with resin to ensure the inner surface reinforcement is protected Any pits exceeding this size must be repaired While some waviness is allowed, the surface must remain smooth and devoid of pits Additionally, the tank's exterior surface should be smooth and free from exposed fibers.
Hydrostatic Testing
7.2.1 The tank shall be hydrostatically tested in the manufacturer’s shop.
If the buyer chooses to conduct a second hydrotest in the field post-installation, this procedure falls outside the parameters of this specification For detailed requirements, please refer to the Data Sheet.
7.2.2 Testing shall be conducted with clean, fresh water to which a surfactant has been added.
7.2.3 The test shall be held for a minimum period of one hour, unless a longer period is specified by the purchaser
If there is a sign of cracks or excessive deformation, then the test period shall be at least four hours long.
7.2.4 The tank shall be tested by filling through use of a temporary standpipe 0.305 m (12 in.) above the top crown of the tank.
7.2.5 All connections shall be plugged or blinded during the test, using the type and size of fittings intended for use after installation, to conform thread or flange sealing integrity.
7.2.6 All leaks and defects found shall be repaired by the manufacturer and the tank retested for a minimum of
2 hours If the tank shows a consistent defect(s), it shall be rejected.
Quality Control Tests
The manufacturer or their subcontractor must conduct tests on the completed tank to ensure compliance with the specification These tests will assess thickness, degree of cure, dimensional tolerances, and surface cure.
Tank shell thickness must be measured and documented at all cutouts to ensure compliance with the specified minimum thickness Measurements should be conducted using a micrometer, calipers, ultrasonic methods, or other sensitive techniques that yield consistent data At each cutout, readings should be taken at two locations approximately 180° apart, aligned in the circumferential direction.
7.3.3 Degree of cure of the laminate shall be determined to meet the resin manufacturer’s standards by measuring Barcol hardness in accordance with ASTM D2583.
7.3.4 Tank dimensions and standard nozzle locations shall be verified on the finished tank to meet the tolerances stipulated in Table 1 and locations specified in Figure 2.
To detect surface inhibition on external and secondary bond surfaces exposed to air during curing, an acetone test is required The procedure involves wiping the surface with clean acetone for 30 seconds, allowing it to dry for 10 to 20 seconds, and then checking for tackiness A tacky surface indicates an incomplete cure, which necessitates a Barcol hardness test for verification If incomplete curing is confirmed, the tank must either be repaired and retested or scrapped, depending on the purchaser's preference.
Optional Tests
Additional tests may be performed as requested by the purchaser, which can include tensile strength (ASTM D638), flexural strength (ASTM D790), glass content (ASTM D2584), temperature resistance of resin (ASTM D790), acoustic emission examination (SPI E-1067), and destructive tests If destructive testing is required, it will be carried out on nozzle and manway cutouts, for which the manufacturer must retain appropriately sized cutouts for testing purposes.
Painting
The external surface paint can serve as the finishing color and must include a comprehensive exterior coating system comprising surface preparation, primer, and finish coating Surface preparation should adhere to SSPC-SP1 standards, involving solvent cleaning to eliminate dirt, grease, and oil, followed by rinsing with potable water The surface should be uniformly and lightly abraded to create an etch or anchor profile without compromising the design thickness, using fine abrasive blasting or 100 grit sandpaper A polyamide epoxy primer is recommended, with an aliphatic polyurethane finish, and all applications must comply with the coating manufacturer's product Data Sheet.
The tank must feature a metal nameplate, positioned as illustrated in Figure 2, and marked in accordance with Figure 5 This nameplate should indicate the nozzle configuration as either "Standard" or "Modified," and it must reference API 12P Additionally, if applicable, the API monogram should be included on the nameplate, as detailed in Section 5.11 of Annex A (Use of API Monogram by Licensees) and Annex D (FRP Tank Data Sheet).
8.2 If the purchaser specifies requirements that conflict with this specification, then the tank shall not be monogrammed and the nameplate shall not refer to API-12P.
NOTE If there is any exception made to a requirement in API-12P, the nameplate should be marked to refer to the purchaser’s specification.
8.3 The nameplate shall be affixed with bolts and nuts or by other suitable means
Manufactured in Accordance with API Specification 12P
Type of Resin Used in Manufacture
Minimum and Maximum Operating Temperature
Design Vacuum °C or °F MPa or oz mm or in of WCNozzle Configuration (Standard or Modified)
Use of API Monogram by Licensees
The API Monogram ® is a registered certification mark owned by the American Petroleum Institute (API) and licensed by its Board of Directors The API Monogram Program allows product manufacturers to use the API Monogram on new products that meet specific product specifications and are produced under a quality management system compliant with API Q1 requirements A comprehensive, searchable list of all Monogram licensees is available on the API Composite List website (www.api.org/compositelist).
The API Monogram and license number on products signify a warranty from the licensee to both API and product purchasers, confirming that the products were manufactured under a quality management system compliant with API Q1 standards Licenses for the API Monogram are granted only after a thorough on-site audit verifies that an organization has established and consistently maintained a quality management system that meets API Q1 requirements, ensuring that the products adhere to the relevant API specifications and standards While any manufacturer can assert that their products meet API requirements, only those with an API license are authorized to display the API Monogram on their products.
This annex outlines the criteria for organizations seeking to voluntarily obtain an API Monogram license, ensuring that their products meet the relevant API product specifications and standards, as well as the requirements of the API Monogram Program.
For information on becoming an API Monogram Licensee, please contact API, Certification Programs, 1220 L Street,
N W., Washington, DC 20005 or call 202-682-8145 or by email at certification@api.org.
API Specification Q1, Specification for Quality Management System Requirements for Product Manufacturing for the
Petroleum and Natural Gas Industry
For purposes of this annex, the following terms and definitions apply.
A newly manufactured product by an API licensee adheres to a fully implemented API Q1 compliant quality management system, ensuring it meets all specified requirements of the relevant API product specifications and standards.
Requirements, including performance and licensee-specified requirements, set forth in API Q1 and the applicable API product specification(s) and or standard(s).
NOTE Licensee-specified requirements include those activities necessary to satisfy API specified requirements.
A prescribed set of rules and requirements for a specific product includes definitions of terms, classification of components, and detailed procedures It outlines specified dimensions, manufacturing criteria, material requirements, performance testing, and design activities Additionally, it addresses the measurement of quality and quantity concerning materials, products, processes, services, and practices.
Organization that has successfully completed the application and audit process and has been issued a license by API.
Records and documents required to provide evidence that the applicable product has been designed in accordance with API Q1 and the requirements of the applicable product specification(s) and/or standard(s).
An organization applying the API Monogram to products shall develop, maintain, and operate at all times a quality management system conforming to API Q1
A.5 Control of the Application and Removal of the API Monogram
Licensees must manage the application and removal of the API Monogram by ensuring that only products meeting API specifications display the Monogram Additionally, each licensee is required to create and uphold a documented marking procedure that outlines the Monogram requirements as specified in this annex and relevant API product standards.
1) define the authority responsible for application and removal of the API Monogram;
2) define the method(s) used to apply the API Monogram;
3) identify the location on the product where the API Monogram is to be applied;
4) require the application of the licensee's license number and date of manufacture of the product in conjunction with the use of the API Monogram;
The date of manufacture must consist of at least two digits for the month and two digits for the year (e.g., 05-12 for May 2012), unless specified otherwise in the relevant API product specifications or standards.
The application of additional API product specifications and marking requirements is essential Only licensed API licensees are permitted to use the API Monogram and its designated license number on products eligible for the monogram The API Monogram license is specific to a site, meaning it can only be applied at the licensed facility location The monogram may be applied at any suitable time during production; however, it must be removed if the product is found to be non-compliant with the relevant API specifications and standards, as outlined in the API Monogram Program.
For specific manufacturing processes or product types, alternative procedures for API Monogram marking may be permitted Detailed requirements for these alternative marking procedures can be found in the API Policy and the API Monogram Program Alternative Marking of Products License Agreement, accessible on the API Monogram Program website at http://www.api.org/alternative-marking.
Licensees and applicants for licensing are required to keep an up-to-date design package for all products covered by their Monogram license This design package must include objective evidence demonstrating that the product design complies with the latest API product specifications Additionally, these design packages must be accessible during API facility audits.
In specific instances, the exclusion of design activities is allowed under the Monogram Program, as detailed in
Advisory # 6, available on API Monogram Program website at http://www.api.org/advisories.
The API Monogram Program identifies facilities capable of manufacturing equipment that meets API specifications and standards Licensing may be denied or suspended based on a facility's manufacturing capabilities If necessary, API can conduct additional audits of subcontractors at the organization's expense to verify compliance with relevant API product specifications and standards.
A.8 API Monogram Program: Nonconformance Reporting
API requests information regarding products that do not meet specified requirements and any field failures attributed to specification deficiencies or nonconformities Customers are encouraged to report issues with API monogrammed products Nonconformances can be reported through the API Nonconformance Reporting System at http://compositelist.api.org/ncr.asp.
Vertical flat bottom tanks require installation on a base that offers continuous support for the tank bottom and knuckle radius, ensuring adequate bearing strength to handle the weight of a fully filled tank while minimizing settlement Recommended materials for tank grades should be utilized whenever feasible.
— compacted gravel with a top clean sand layer to provide a smooth uniform support;
— smooth surfaced concrete, or a concrete grout.