1、Designation: D 1998 06Standard Specification forPolyethylene Upright Storage Tanks1This standard is issued under the fixed designation D 1998; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in p
2、arentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This specification covers flat-bottom, upright, cylindri-cal tanks molded in one-piece seamless construction by rota-tional molding. The tanks a
3、re molded from polyethylene forabove ground, vertical installation and are capable of contain-ing aggressive chemicals at atmospheric pressure. Included arerequirements for materials, properties, design, construction,dimensions, tolerances, workmanship and appearance. Tankcapacities are from 1900 L
4、500 gal up.1.2 This specification does not cover the design of vesselsintended for use at pressures other than atmospheric pressure.Furthermore, this specification does not cover the design ofportable tanks. It is also not for vessels intended for use withliquids heated above their flash points, or
5、temperatures above66C 150F for Type I tanks and 60C 140F for Type IItanks for continuous service. NFPA Standards 30 and 31 shallbe consulted for installations that are subject to the require-ments of these standards.1.3 Special design considerations not covered in this speci-fication shall be given
6、to vessels subject to superimposedmechanical forces, such as seismic forces, wind load oragitation; to vessels subject to service temperature in excess of23C 73.4F; and vessels subject to superimposed pressureexceeding 25.4 cm 10 in. of water or 2.5 3 103MPa 0.36psi.1.4 The values stated in SI units
7、 are to be regarded as thestandard. The values given in brackets are for information only.NOTE 1There is no similar or equivalent ISO standard.1.5 The following precautionary caveat pertains only to thetest methods portion, Section 11, of this specification: Thisstandard does not purport to address
8、all of the safety concerns,if any, associated with its use. It is the responsibility of the userof this standard to establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for C
9、onditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 1693 Test Method for Environmental Stress-Cracking ofEthylene PlasticsD 2837 Test Method for Obtaining Hydrostatic DesignBasis for Thermoplastic Pipe Materials or Pressure DesignBasis for Thermoplastic Pipe ProductsD 3892 Practi
10、ce for Packaging/Packing of PlasticsD 4703 Practice for Compression Molding ThermoplasticMaterials into Test Specimens, Plaques, or SheetsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodF 412 Terminology Relating to Plastic Piping Systems2.2 OSHA Stan
11、dard:29 CFR 1910.106 Occupational Safety and Health Admin-istration, Flammable and Combustible Liquids32.3 ANSI Standard:B-16.5 Pipe Flanges and Flanged Fittings42.4 NFPA Standards:30 Flammable and Combustible Liquid Code531 Installation of Oil Burning Equipment53. Terminology3.1 Definitions: Defini
12、tions are in accordance with Termi-nologies D 883 and F 412 and the Association of RotationalMolders (ARM) Glossary of Terms,6unless otherwise indi-cated.3.2 Definitions of Terms Specific to This Standard:1This specification is under the jurisdiction of ASTM Committee D20 onPlastics and is the direc
13、t responsibility of Subcommittee D20.15 on ThermoplasticMaterials (Section D20.15.01).Current edition approved Sept. 1, 2006. Published October 2006. Originallyapproved in 1991. Last previous edition approved in 2004 as D 1998 - 04.2For referenced ASTM standards, visit the ASTM website, www.astm.org
14、, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Occupational Safety and Health Administration (OSHA), 200Constitution Ave., NW, Washington, DC 20210.4Available f
15、rom American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.5Available from National Fire Protection Association (NFPA), 1 BatterymarchPark, Quincy, MA 02269-9101.6Available from Association of Rotational Molders, 2000 Spring Road, Suite511, Oak Brook, IL 60523.1*A
16、 Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.1 impact failure, nany crack in the test specimenresulting from the impact and visible in normal room lightingto a per
17、son with normal eyesight.3.2.2 rotational molding, na three-stage commercial pro-cess consisting of loading the mold with powdered resin,fusing the resin by heating while rotating the mold about morethan one axis, and cooling and removing the molded article.3.2.3 service factor, na number less than
18、1.0 (that takesinto consideration all the variables and degrees of safetyinvolved in a polyethylene storage tank installation) that ismultiplied by the hydrostatic design basis to give the designhoop stress.4. Classification4.1 Tanks meeting this specification are classified accordingto type as foll
19、ows, and it is the responsibility of the purchaserto specify Type I or Type II:4.1.1 Type ITanks molded from cross-linkable polyethyl-ene.4.1.2 Type IITanks molded from non-cross-linkable poly-ethylene.5. Materials5.1 This specification is based upon the use of 100 % virginpolyethylene intended for
20、the rotational molding process. Anyuse of regrind, recycled or reprocessed materials, or combina-tions of such materials, shall not rely upon the performancedata of their original constituents, but must meet the require-ments of this specification in its own right.5.1.1 The polyethylene shall have a
21、 stress-cracking resis-tance of 500 h minimum F50 in accordance with Test MethodD 1693, Condition A, full-strength stress-cracking agent. Thetest specimens shall be compression molded or rotationalmolded. If compression molded, Procedure C of Annex A1 ofPractice D 4703 shall be followed for both typ
22、es of polyethyl-ene with a minimum platen temperature of 177C 350F forType II materials. The temperature for Type I (cross-linkable)polyethylene shall be 197C 390F and the platen shall bekept closed under full pressure for five minutes at the specifiedtemperature in order to bring about the crosslin
23、king reaction. Ifthe test specimens are rotational molded, the conditions forrotational molding shall be similar to the conditions used formolding a tank from this polyethylene.NOTE 2The stress-cracking test is not used as an indicator of generalchemical resistance of a polyethylene. Refer to the po
24、lyethylene suppliersor molders chemical-resistance chart for information on the resistance ofthe polyethylene to specific chemicals or products, or test specificproducts or chemicals prior to use.5.2 All tanks used for outdoor installation shall contain anultraviolet stabilizer at a level adequate t
25、o give protection forthe intended service life of the tanks. This stabilizer shall becompounded into the polyethylene.5.3 Any pigments added must be compatible with thepolyethylene and shall not exceed 0.5 % dry blended, and 2 %compounded in, of the total weight.NOTE 3The use of dry-blended pigments
26、 may have an effect onphysical properties, that is, impact strength.5.4 Each resin used in designing tanks covered by thisspecification shall have hydrostatic-hoop-stress data available.6. Design Requirements for Both Type I and Type II TanksDesign Requirements for Both Type I and Type II Tanks6.1 C
27、ylinder Shell (Unsupported Portion of Tanks)Theminimum required wall thickness of the cylindrical shell at anyfluid level shall be determined by the following equation, butshall not be less than 4.7 mm 0.187 in. thick. The toleranceindicated in 9.1.2 applies to these dimensions.T 5 P 3 OD/2 SD (1)wh
28、ere:T = wall thickness, mm in.,P = pressure, MPa (0.0098 MPa/m-H2O 3 SG 3 H(m),or psi (0.433 psi/ft-H2O 3 SG 3 H (ft),SG = specific gravity of fluid,H = fluid head, m ft,OD = outside diameter of tank, mm in., andSD = hydrostatic design stress, MPa psi.6.1.1 The hydrostatic design stress that is used
29、 to determinethe minimum wall thickness at any fluid level must be based onhoop stress data for the resin. The hoop stress data, obtained inaccordance with the procedures of Test Method D 2837,provide a hydrostatic-design-basis for the resin. Thehydrostatic-design-basis must be reduced by a service
30、factor todetermine the actual hydrostatic design stress. The maximumservice factor shall be 0.5 for wall thicknesses less than 9.5 mm0.375 in. For thicknesses equal to or greater than 9.5 mm0.375 in., the maximum service factor shall be 0.475. Forexample, if the hydrostatic-design-basis for the resi
31、n is 8.7MPa 1260 psi, the hydrostatic design stress for a tank withwall thickness greater than 9.5 mm 0.375 in. is0.475 3 8.7 = 4.1 MPa or 0.475 3 1260 = 600 psi.6.1.2 Tank hoop stresses shall be derated for service above23C 73.4F.6.2 Cylinder Shell (Externally Supported Tanks)Theminimum required wa
32、ll thickness for the cylinder straight shellmust be sufficient to support its own weight in an uprightposition without any external support, but shall not be less than4.7 mm 0.187 in. thick. The tolerance indicated in 9.1.2applies to these dimensions.6.3 Top HeadMust be integrally molded with the cy
33、lindershell. The minimum thickness of the top head shall be equal tothe top of the straight wall.6.4 Bottom HeadMust be integrally molded with thecylinder shell. The minimum thickness for a full-supportedflat-bottom head shall be 4.7 mm 0.187 in. The radius of thebottom knuckle of a flat-bottom tank
34、 shall not be less than 25.4mm 1 in. for tanks with a diameter less than 1.8 m 6 ft and38.1 mm 1.5 in. for a diameter greater than 1.8 m 6 ft. Theminimum thickness of the radius shall not be less than themaximum thickness of the cylinder wall.D19980626.5 Open-Top TanksThe top edge of open tanks shal
35、l bereinforced by design to maintain its shape after installation.7. Fittings7.1 Fabricated nozzles, gaskets, and other fitting accessoriesmust be chemically compatible with the materials to behandled in the tanks.7.2 Openings that are cut in tanks to install fittings must nothave sharp corners. Hol
36、es shall have minimum clearance toinsure best performance of fittings.7.3 The size, location, and specification, and so forth, formanways and fittings shall be agreed upon between thepurchaser and the manufacturer.7.4 The vents must comply with OSHA 1910.106 (F) (iii)(2) (IV) (9) normal venting for
37、atmospheric tanks, or otheraccepted standard, or shall be at least as large as the filling orwithdrawal connection, whichever is larger but in no case lessthan 25.4 mm 1 in. nominal inside diameter.7.5 Fittings installed in tanks shall be of appropriatestrength to meet manufacturer and purchaser spe
38、cifications.7.6 Bolts securing mechanical fittings must be manufac-tured of materials compatible with tank contents.7.7 Provisions shall be made to attach hold-down devices tothe tanks for outdoor service.7.8 For all flanged connectors, the flange drilling andbolting shall be in accordance with ANSI
39、/ASME B-16.5 for150 psi 1 MPa pressure class straddling the principal center-line of the vessel.8. Performance Requirements8.1 The following performance requirements shall be metby Type I and Type II tanks:8.1.1 Low-Temperature ImpactLow-temperature impactshall be determined using the test method de
40、scribed in 11.3.The requirements for Type I and Type II tanks are as follows:Wall thickness, mm in.Impact energy,min. J ft-lb4.7 mm 0.187 in. to and including 6.4 mm 0.25 in. 122.0 906.6 mm 0.26 in. to and including 12.9 mm 0.50 in. 135.5 10012.9 mm 0.51 in. to and including 19.3 mm 0.75 in. 203.2 1
41、5019.3 mm 0.76 in. to and including 25.4 mm 1.00 in. 271.0 200Greater than 25.4 mm 1.00 in. 271.0 2008.1.2 Percent Gel, for Type I Tanks OnlyThe percent gellevel shall be determined using the test method described in11.4. The percent gel level for Type I tanks on the inside 3.2mm 0.125 in. of the wa
42、ll shall be a minimum of 60 %.9. Dimensions and Tolerances9.1 GeneralAll dimensions will be taken with the tank inthe vertical position, unfilled. Tank dimensions will representthe exterior measurements.9.1.1 Outside DiameterThe tolerance for the outside di-ameter, including out of roundness, shall
43、be 63%.9.1.2 Shell Wall and Head ThicknessThe tolerance foraverage thickness at each elevation shall be 10 % of thedesign thickness on the low side and shall be unlimited on thehigh side. The tolerance for individual audit readings shall belimited to 20 % of the design thickness. The total amount of
44、surface area on the low side of the tolerance shall not exceed10 % of the total surface area.9.1.3 Placement of FittingsThe tolerance for fitting place-ments shall be 12.7 mm 0.5 in. in elevation and 2 radial atambient temperature.10. Workmanship10.1 Type I finished tank walls shall be free, as comm
45、er-cially practicable, of visual defects such as foreign inclusions,air bubbles, pinholes, pimples, crazing, cracking and delami-nations that will impair the serviceability of the vessel. Finebubbles are acceptable with Type II tanks to the degree towhich they do not interfere with proper fusion of
46、the resin melt.10.2 Because of the differences in various resins used in thisapplication and the molding conditions used, the interiorsurface characteristics may vary. The acceptable finish shall bepredetermined by agreement between the molder and thebuyer.11. Test Methods11.1 Test SpecimensTest spe
47、cimens shall be taken from anarea that is representative of the bottom side wall. If norepresentative sample cut-out area in the tank is available, testspecimens shall be molded in a test mold. In either case, priortesting shall verify that the tank wall and the test specimenhave equal impact resist
48、ance.11.1.1 The test mold shall be constructed of the same typematerial and have the same wall thickness as the tank mold.The thickness of the specimen from a test mold shall be thesame as the thickness of the bottom sidewall within thetolerances as defined in 9.1.2. The test mold shall be moldedwit
49、h each tank.11.2 ConditioningIf requested, test specimens shall beconditioned at 23 6 2C 73.4 6 3.6F and 50 6 5 % relativehumidity for not less than 40 h prior to testing in accordancewith Procedure A of Practice D 618.11.3 Low-Temperature Impact Test:11.3.1 ScopeThis test method is for the determination ofthe impact property of rotational-molded polyethylene tanks atlow temperature.The test method is used on tanks molded fromboth crosslinked and no
