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AS 1692—1989
Australian Standard�
Tanks for flammable andcombustible liquids
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This Australian Standard was prepared by Committee ME/17, Flammable & CombustibleLiquids. It was approved on behalf of the Council of Standards Australia on 29 June 1989and published on 11 December 1989.
The following interests are represented on Committee ME/17:
Association of Australian Port and Marine Authorities
Australian Institute of Petroleum
Australian Paint Manufacturers Federation
Board of Fire Commissioners New South Wales
Confederation of Australian Industry
Department of Administrative Services
Department of Defence
Department of Industrial Relations and Employment, New South Wales
Department of Labour, South Australia
Department of Labour, Victoria
Department of Local Government, Queensland
Department of Mines, Tasmania
Department of Mines, Western Australia
Department of the Arts, Sport, the Environment, Tourism & Territories
Electricity Supply Association of Australia
Insurance Council of Australia
Metal Trades Industry Association of Australia
Railways of Australia Committee
Work Health Authority, Northern Territory
Review of Australian Standards.To keep abreast of progress in industry, Australian Standards are subject toperiodic review and are kept up to date by the issue of amendments or new editions as necessary. It is importanttherefore that Standards users ensure that they are in possession of the latest edition, and any amendments thereto.
Full details of all Australian Standards and related publications will be found in the Standards Australia Catalogueof Publications; this information is supplemented each month by the magazine ‘The Australian Standard’, whichsubscribing members receive, and which gives details of new publications, new editions and amendments, and ofwithdrawn Standards.
Suggestions for improvements to Australian Standards, addressed to the head office of Standards Australia, arewelcomed. Notification of any inaccuracy or ambiguity found in an Australian Standard should be made withoutdelay in order that the matter may be investigated and appropriate action taken.
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AS 1692—1989
Australian Standard�
Tanks for flammable andcombustible liquids
First published as part of AS CB5—1942.Second edition 1957.Third edition 1969.AS CB21 first published 1966.Second edition 1969.Redesignated AS CB21.1—1969, June 1972.AS CB21.2 first published 1972.Parts of AS CB5—1969, AS CB21.1—1969 and ASCB21.2—1972 revised, amalgamated and redesignated
AS 1692—1975.Second edition 1983.Third edition 1989.
PUBLISHED BY STANDARDS AUSTRALIA(STANDARDS ASSOCIATION OF AUSTRALIA)1 THE CRESCENT, HOMEBUSH, NSW 2140
ISBN 0 7262 5855 5
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PREFACE
This Standard was prepared by the Standards Australia Committee on Flammable andCombustible Liquids, to supersede AS 1692–1983. The Standard was originally derived fromAS CB5, Oil fuel installations, which was first issued in 1942. When AS 1940,SAAFlammable and Combustible Liquids Codewas issued in 1976, the requirements for theconstruction of tanks, as distinct from their installation, were extracted to be dealt with in aseparate reference standard.
At that time a decision was made to limit the Standard to steel tanks, largely as a matter ofconvenience and expediency, i.e. the framework already existed in AS CB5 and otherStandards, and steel tanks were well understood and quite common, while requirements forother materials would have needed time to develop.
The 1983 edition extended the scope to include stainless steel tanks. Consideration was givento the inclusion of aluminium, but the very wide variety of alloys, with widely differingstrengths and susceptibility to corrosion, made it difficult to recommend thicknesses with anydegree of confidence. Since aluminium is not in widespread use, and is then mainly used inspecial cases where compatibility with the contents is a major consideration, it was decided toomit it from the Standard, and treat it under Clause 1.6.
Thicknesses for all materials were chosen on the same premise as before, i.e. the thickness forall tanks except Category 6 are empirical, being the result of experience rather than accuratestress calculations. It has been considered that stresses will be comparatively low and that theneed for the tank to be reasonably sturdy for handling, or a need for corrosion allowance, andsimilar practical factors dictate the material thickness. Other limiting assumptions whichhave a bearing on the shell thickness are as follows:
(a) Liquid levels after normal filling will not be substantially above the ‘tank–full’condition. No allowance has been made for the effect of filling an extended pipe to alevel substantially above the tank.
(b) The vapour space pressure will not exceed 35 kPa.
(c) The length/diameter ratio of an aboveground tank on two supports will not exceed 5.
(d) Shells are not stiffened.
(e) The material is commercial grade low–carbon steel.
(f) The liquid being stored is not more corrosive than normal petroleum products.
(g) The density of the liquid being stored will not exceed 1000 kg/m3.
(h) The possibili ty of using thinner materials, compensating by special shaping,corrugating, bracing or stiffening, is recognized, especially for stainless steel. Any suchalternatives may be admissible under Clause 1.6.
Outside these conditions, the assumptions and hence the requirements are no longer valid andspecific approval may be necessary.
This Standard does not insist on compliance with any particular material Standards, or the useof specific grades of materials.
Tanks of glass–fibre reinforced plastics (GRP) are not covered in detail in this Standardalthough GRP is recognized as an alternative material. High cost has militated againstwidespread use, but construction is dealt with adequately in existing standards, except forunderground service where some additional stiffening may be required.
The dimensional requirements of the first edition had been compared with British, American(UL), French, and German Standards to ensure that they were not inconsistent with generaltrends. The new dimensions for stainless steel were derived from AS 2809.2,Tankers forflammable liquids, in the absence of any other source.
The committee recognized that there are situations in which liquids other than petroleumderivatives are stored, and in which tank materials other than those covered may be suitable.However, it has not been possible to explore all the alternatives, and such special cases shouldbe negotiated individually with the Authority.
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CONTENTS
Page
SECTION 1. SCOPE AND GENERAL
1.1 SCOPE 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 CLASSIFICATION 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 APPLICATION 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 REFERENCED DOCUMENTS 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 DEFINITIONS 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6 NEW DESIGNSAND INNOVATIONS 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.7 INTERPRETATIONS 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 2. GENERAL DESIGN AND CONSTRUCTION
2.1 GENERAL 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 CONTENTSINDICATOR 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 FILLIN G PROVISIONS 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4 DRAINING AND NORMAL DRAW–OFF 7. . . . . . . . . . . . . . . . . . . . . . . . . .
2.5 MANHOLES 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6 TANK VENTS 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.7 TESTING 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.8 HANDLIN G AND TRANSPORT 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SECTION 3. REQUIREMENTSFOR SPECIFIC CATEGORIESOF TANKS
3.1 CATEGORY 1 TANKS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 CATEGORY 2 TANKS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3 CATEGORY 3 TANKS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4 CATEGORY 4 TANKS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5 CATEGORY 5 TANKS 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6 CATEGORY 6 TANKS 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
APPENDIX A. INFORMATION TO BE PROVIDED BY THEPURCHASER 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
� Copyright — STANDARDSAUSTRALIA
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AS 1692—1989 4
STANDARDS AUSTRALIA
Australian StandardTanks for flammable and combustible liquids
SECTION 1. SCOPE AND GENERAL
1.1 SCOPE. This Standard specifies requirementsfor the design and construction of tanks for thestorage of flammable and combustible liquids,together with certain accessories. It does not dealwith their installation, nor does it deal with road, rail,or marine tankers, or with fuel tanks for vehicles. Itis applicable only to the storage of materials that areliquid at normal temperatures and pressures.
NOTES:1. This Standard is basically oriented towards cylindrical tanks
of commercial grade low carbon steel for petroleum fuelstorage, this being the most common application for tankstorage, but it also provides for stainless steel tanks.Glass-fibre reinforced plastics are recognized alternativematerials, but are dealt with in other Standards, notablyBS 4994 and AS 2634. It is recognized that the storage ofother types of liquid, or the use of other materials ofconstruction, may render part or all of this Standardinappropriate; any such substitutions should be the subject ofspecific approval.
2. Attention is drawn to Appendix A, which sets out details ofparticular information that the purchaser needs to supply inorder that the manufacturer can complete the tank.
1.2 CLASSIFICATION. Tanks within the scope ofthis Standard are classified as follows:(a) Category 1—tanks up to 1200 L capacity, for
aboveground use, intended principally for thestorage of oil fuel in domestic type applications.NOTE: Category 1 tanks cannot be used for the storage offlammable liquids as they do not incorporate a liquid seal.
(b) Category 2— vertical or horizontal cylindricaltanks up to 2500 L capacity, for aboveground use,intended principally for farms and similar openspace locations.
(c) Category 3—rectangular tanks and tanks ofunconventional shapes, intended principally forindustrial use aboveground as either head tanks orstorage tanks.
(d) Category 4— horizontal cylindrical tanks up to150 m3 capacity, for underground or abovegrounduse, intended principally for industrial or servicestation use.
(e) Category 5—vertical cylindrical tanks up to 150m3 capacity, for aboveground use, intended forindustrial use.
(f) Category 6—vertical tanks up to any capacity, ofa size and type that is usually erected on site.
1.3 APPLICATION. Tanks in Categories 1 to 5shall comply with all the relevant requirements ofSection 2 and the specific requirements of Section 3,as appropriate to the category. Tanks in Category 6shall comply with Clause 3.6.1.4 REFERENCED DOCUMENTS. The followingdocuments are referred to in this Standard:
AS1020 The control of undesirable static electricity1170 SAA Loading Code1170.2 Part 2: Wind forces1210 SAA Unfired Pressure Vessels Code1250 SAA Steel Structures Code1554 SAA Structural Steel Welding Code1657 SAA Code for Fixed Platforms, Walkways,
Stairways, and Ladders1940 SAA Flammable and Combustible Liquids
Code2624 Steel plate and strip for the construction of
welded steel tanks for oil storage2634 Chemical plant equipment made from
glass-fibre reinforced plastics (GRP) basedon thermosetting resins
BS2654 Specification for the manufacture of vertical
steel welded storage tanks with butt-weldedshells for the petroleum industry
4994 Specification for the design and constructionof vessels and tanks in reinforced plastics
5500 Specification for unfired fusion weldedpressure vessels
API620 Recommended rules for design and
construction of large, welded low-pressurestorage tanks
650 Welded steel tanks for oil storageASTMD 5 Test method for penetration of bituminous
materials.*
1.5 DEFINITIONS. For the purpose of thisStandard, the definitions below apply:1.5.1 Approved (approval)—approved by (approvalof) the authority concerned.1.5.2 Authority, Authority having jurisdiction —the authority having statutory (legal) control of theinstallation which incorporates the tank.1.5.3 Liquid (flammable, combustible)— aflammable liquid or a combustible liquid as definedin AS 1940.1.5.4 Nominal thickness— the nominal thickness ofmaterial which is commercially available and towhich specified manufacturing tolerances areapplicable.1.5.5 Domestic type— an application common to,but not necessarily restricted to, familiar dwellings.
* Identical with IP 49.
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1.5.6 Capacity— full tank capacity, i.e. the totalvolume which the tank will accept without spilling orleaking.
NOTE: It is recognized that the available capacity of a tankwill normally be less than the full capacity, because of theneed to provide an ullage space to allow for thermalexpansion. A common practice is to allow 3 percent forullage, but local regulations, or factors of the installation suchas tank size, sheltered locations or underground installationcan all have a bearing on the ultimate figure used.
1.6 NEW DESIGNS AND INNOVATIONS. Anynovel materials, designs, methods of assembly,procedures, etc, which do not comply with specific
requirements of this Standard, are not necessarilyprohibited. SAA Committee ME/17, Flammable andCombustible Liquids, can act in an advisory capacityconcerning equivalent suitability, but the specificapproval remains the prerogative of the Authority.
1.7 INTERPRETATIONS. Questions concerningthe meaning, application or effect of any part of thisspecification may be referred to SAA CommitteeME/17, Flammable and Combustible Liquids, forexplanation. The authority of this committee islimited to matters of interpretation and it will notadjudicate in disputes.
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AS 1692—1989 6
SECTION 2. GENERAL DESIGN AND CONSTRUCTION
2.1 GENERAL.
2.1.1 Design suitability. The design of any storagetank shall be such as will ensure that it is adequatefor any load and pressure to which it may besubjected, and shall take into account any corrosiveor other abnormal conditions. Any method ofconstruction or material that is not specifically dealtwith herein shall be applied in conformity with goodengineering practice. Any weld-on fittings, flanges,nozzles, and the like, shall be compatible with thematerial of the tank and the welding process.
2.1.2 Material. Any material used in theconstruction of a tank shall be of a type and qualitysuitable for the conditions of use, and compatiblewith the liquid being stored. Material should complywith any relevant Australian Standard, or anappropriate other Standard if no Australian Standardexists.
2.1.3 Welding. Any welded joint shall comply withthe applicable requirements of AS 1554, weldcategory GP.
2.1.4 Finish and protective coatings.Any internalor external protective coatings shall be sufficient toensure satisfactory life of the tank and its supports.Particular attention should be paid to the following:
(a) The soil or atmospheric conditions surroundingthe tank.
(b) Compatibility of internal coatings with thecontents of the tank.
(c) Protection of areas particularly vulnerable tocorrosion, e.g. points of contact with thesupports, rainwater traps.
(d) The specific requirements for surface preparationand coatings where cathodic protection is used.
2.1.5 Supports. Any supporting structure that issupplied with the tank shall comply with thestructural code applicable for the particular material,e.g. AS 1250 for steel supports. Any welded-onsupports, brackets or other fittings shall be welded sothat the penetration of moisture in a manner likely tocause corrosion of the tank shell is prevented.
NOTE: Particular attention should be paid to the method oftransmitting loads between the tank shell and the supports, sothat local overstressing or distortion of the tank shell is avoided.BS 5500 describes methods for calculating these stresses.
2.1.6 Connections to underground tanks.All pipeentries to a tank intended to be wholly buried belowground level shall be through the top of the tankunless specifically approved otherwise.
2.1.7 Liquid seal. Every fill pipe, suction pipe, ordip pipe that enters through the top of a tank and thatis likely to be opened to atmosphere at some timeduring a normal filling procedure shall be providedwith a liquid seal sufficient to ensure that the bottomend of the pipe is submerged in not less than 25 mmof liquid at all times subsequent to the initial filling.Tanks of Category 1 are exempt from thisrequirement.
NOTE: Figure 2.1 illustrates typical arrangements.
2.1.8 Access ladders and structures.Any accessstructure shall comply with AS 1657. The designshall be such that there is no differential movementbetween the tank and the structure.
2.2 CONTENTS INDICATOR.
2.2.1 Indicator required. Each storage tank shallbe provided with a means for ascertaining the liquidlevel. If the indicator is of a type designed forreading at a remote location, additional facilities forchecking its accuracy shall be provided. Themaximum permitted filling level shall be indicated onthe gauge.
NOTES:1. Any change to the contents of the tank may alter the
maximum permitted filling level.2. Acceptable types of indicator are float gauges, hydrostatic
pressure gauges, dipsticks, dip tapes or sight tubes (gaugeglasses).
2.2.2 Dipstick. Any dipstick-indicating system shallcomply with the following requirements:
(a) The opening shall be provided with a cap whichshall be liquid-tight and vapour-tight unless acommon dip and vent is used on abovegroundtanks.
(b) Where a dipstick measures by contacting thebottom of the tank, a tubular dipstick guide shallbe provided. The guide shall incorporate apressure equalizer hole which connects the upperend of the dip pipe with the upper tank space.This hole, if over 1.5 mm diameter, shall becovered by an antiflash gauze not coarser than600 µm mesh. A durable striker pad shall beattached firmly to the tank bottom below the dipopening, other than for tanks of Categories 1and 2.
(c) Any dipstick for a tank intended to containflammable liquids shall be of non-ferrousmaterial.
2.2.3 Sight tubes. A sight tube of the typecommonly known as a gauge glass shall not be fittedto any tank storing flammable liquids and should notbe used for any other class of liquid unless such useis unavoidable. Where a gauge glass is unavoidable –
(a) an adequate protective guard for the tube shall beprovided;
(b) the material of the sight tube shall be unaffectedby the liquid used; and
(c) a self-closing shut-off valve shall be provided onany connecting leg that is below liquid level.
2.3 FILLING PROVISIONS.
2.3.1 General. Each tank shall be provided with ameans of filling to suit the intended method of fillingand the location of the fill point in relation to thetank.
NOTES:1. The type should be agreed between the purchaser and the
supplier.2. For a top-filled tank, a weatherproof cap, cover, or plug is
normally provided with the tank.
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2.3.2 Fill pipe. The filling provision on every tankother than a Category 1 tank shall be such that liquidis conducted through a fully enclosed pipe to adischarge point which is not more than one diameterof the pipe above the tank bottom.
Where filling is from the top, an extension pipe shallbe used to achieve compliance with this requirement.
Where a side entry into a vertical tank requires to bereinforced, the discharge point may be located highenough to accommodate the reinforcing ring, butshould be not more than 150 mm from the tankbottom.
NOTE: This requirement is intended to ensure that splashingduring filling, which may result in the generation of staticelectricity, is minimized. See AS 1020.
2.3.3 Pressure equalization.Any fill pipe that fillsdownwards into a tank shall incorporate a pressureequalizer hole which connects the upper end of thepipe with the upper tank space. This hole, if over 1.5mm diameter, shall be covered by an antiflash gauzenot coarser than 600µm mesh.
2.3.4 High-head filling. Where the height of thefilling point above the tank is such that the pressureon the tank will exceed the test pressures described inClause 2.7, the tank shall incorporate a provision toprevent the liquid level from rising above thetank-full condition or the tank shall be designed andtested to withstand the additional pressure of aliquid-full filling extension.
2.4 DRAINING AND NORMAL DRAW-OFF.
2.4.1 General. It shall be possible to remove theentire liquid contents from a tank without removingthe tank from its installed position.
NOTE: Where the conditions of installation are such thatdraining by gravity through a bottom outlet cannot be provided,e.g. an underground tank, facilities for the insertion of a suctionspear through a fill pipe or other opening will be deemed tocomply with this requirement.
2.4.2 Drain outlet location. Any drain provisionshould draw from the lowest point of the tank and, ifseparate from the liquid draw-off pipe, should belocated as far as possible from the draw-off pipe.
2.5 MANHOLES.
2.5.1 Where required. A manhole shall be providedwhen specified by the tank purchaser.
NOTE: A manhole is not an essential for tank safety, but may beconvenient during construction, or for the maintenance, cleaning,or inspection of the tank and of any equipment inside it.
2.5.2 Size of manholes.Any manhole shall be notless in size than the following:
(a) If elliptical, 450 mm× 400 mm.
(b) If circular, 450 mm diameter.
(c) If the manhole neck is over 200 mm high,600 mm diameter.
* This distance will alter the depth of the liquid seal if thetank is to be installed with a slope, and in such casesadequate correction must be made in order to maintainthe seal dimensions (see Clause 2.1.7)
FIGURE 2.1. LIQUID SEAL PROVISIONS
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AS 1692—1989 8
NOTES:1. These sizes should be exceeded wherever possible. In particular,
where breathing apparatus may be required for personnelentering the tank, a manhole should be not less than 600 mmdiameter.
2. Fixed ladders within the tank may be necessary to providereasonable means of access.
2.5.3 Multiple manholes. Where a vertical tank over3 m high is required to have a manhole, and themanhole is required to be near the top of the tank, asecond manhole shall be provided adjacent to the bottomof the tank. Alternatively, if a single manhole is locatedadjacent to the bottom of the tank, no other manhole isrequired unless specified by the purchaser.2.5.4 Manhole covers. Each manhole shall beprovided with a cover which shall be vapour-tight andliquid-tight at the test pressure.2.6 TANK VENTS.2.6.1 General. Each tank shall incorporate a provisionto vent to atmosphere the vapour space above the liquid.The vent may be combined with the filling provision fora Category 1 tank; for all other tanks a vent shall beseparate from the fill orifice. The venting provision maybe one of the following:(a) Free venting, in which the vapour space is in
contact with the atmosphere without any interveningvalves or other devices, so that the pressure abovethe liquid is substantially that of the surroundingatmosphere.
(b) Pressure-vacuum venting, in which a control devicepermits a positive or negative pressure within thetank to reach a predetermined level before thepressure or vacuum is relieved.
(c) Emergency venting, used to supplement (a) and (b),in which excessive pressure built up in emergencyconditions such as fire is relieved by means of apressure-relief device.
2.6.2 Size of vent. The size of any free vent orpressure-vacuum vent shall be such that pressure orvacuum resulting from filling or emptying oratmospheric temperature change will not cause stressesin excess of the normal maximum design stress. Indetermining the size of the vent connection, thefollowing requirements shall apply:(a) Where a free vent in a Category 1 tank is combined
with the filler, the opening shall provide not lessthan 600 mm2 of free vent area with the nozzleinserted and 10 mm2 with the cap in place.
(b) For a separate free vent in a tank of Category 1 orCategory 2, the vent area shall be not less than theequivalent of a 25 mm nominal internal diameterpipe.
(c) For any other category of tank, the vent provisionor the vent connection facilities shall be thosespecified by the purchaser of the tank.
NOTE: The design of the vent, and particularly its size, aredependent on factors that relate to the specific installation; thereforea tank manufacturer would not normally undertake to design andsize the vent without instructions from the purchaser. AS 1940provides requirements to assist in vent design.
2.6.3 Vent terminal. The discharge end of any freevent supplied as part of a tank shall be protected fromthe ingress of foreign material, e.g. by a return bend ora protective cap, cage, or fitting. Any such fitting shallnot reduce the required vent area. The discharge point
shall be higher than the filling point and not less than150 mm above the tank top.2.7 TESTING.2.7.1 Leakage test.Each tank shall be subjected to aleakage test before any painting, coating, or similartreatment is applied, and shall be found to be sound andliquid-tight before being put into service. A hydrostatictest method should be used, but air testing may beapplied in the conditions specified in Clause 2.7.3 to anytank except those in Category 3 or Category 6. Whenhydrostatically testing, a tank shall be tested in theorientation of its operation, i.e. vertical tanks shall betested when vertical, horizontal tanks tested whenhorizontal.
NOTE: Any flat side or end may be supported during testing,provided that the method of support does not inhibit the observationof any leak.
2.7.2 Hydrostatic testing. Any hydrostatic test shallbe carried out in accordance with the followingrequirements, as applicable:(a) For any free-vented tank in Category 1, Category 2,
Category 4 or Category 5, the test pressure shall bethat caused when the tank is filled with water and1m additional water head is applied. Where the tankfilling or operating pressure will exceed theequivalent of 1m head above the top of the tank, thetest pressure shall be that maximum pressure plus1m head of water.
(b) For any free-vented Category 3 tank, the testpressure shall be as in (a) above, except that theadditional head shall be reduced to 150 mm.
(c) For any Category 6 tank, the test pressure andprocedure shall be that given in the Standard towhich the tank was built.
(d) Where a pressure-vacuum or emergency vent is tobe used with the tank, the test pressure shall be asin (a) above, plus 35 kPa.
(e) The test pressure shall be applied for sufficient timeto allow any leaks to develop and to be observed.
NOTE: The purchaser is free to specify higher test pressures, butthe design of the tank should be checked for its ability to withstandany such higher pressures.
2.7.3 Air testing. Any air test shall be conducted inaccordance with the following requirements:(a) Air testing shall be applied only to new tanks and at
the manufacturer’s premises.(b) The equipment and operation shall be approved by
the Authority responsible for pressure-vessel safetyand workplace safety at the testing site.
(c) The test pressure shall be that which will stress toa level equivalent to that which would be caused bythe appropriate hydrostatic test pressure, providedthat the test pressure shall not exceed 35 kPawithout the approval of the Authority responsiblefor pressure vessel and workplace safety at thetesting site. If approval for such test pressure cannotbe obtained, then a hydrostatic test as inClause 2.7.2 shall be applied.
(d) When air for testing is taken from a source ofsupply having a pressure greater than 35 kPa,pressure shall be reduced by means of a pressurereducing device; a pressure gauge, a safety valve, orhydrostatic pressure-relieving device, and a pressurerelease cock shall be fitted on the low pressure side.
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(e) A tank that is to be filled from a filling pointmore than 1 m above the tank shell shall betested at the head resulting from the fillinglocation, plus an additional 1 m head of water.
(f) The pressure-relieving device shall be capable ofdischarging the maximum delivery of thepressure-reducing device without rise in pressurebeyond 110 percent of the test pressure.
(g) The tank shall not be subjected to blows whileunder air pressure.
(h) Air for testing shall be introduced gradually andevenly until the test pressure has been reached.
(i) The test pressure shall be applied for sufficienttime to allow any leaks to develop and to beobserved.
2.8 HANDLING AND TRANSPORT. Any tankwhich could suffer damage because of stresses causedby handling and transportation shall be provided withadequate supports and stays to protect it until it hasbeen installed.
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SECTION 3. REQUIREMENTS FOR SPECIFICCATEGORIES OF TANKS
3.1 CATEGORY 1 TANKS.
3.1.1 Size limitation. No tank shall be made toCategory 1 dimensions having a capacity in excess of1200 L.
3.1.2 Material. The material used to form anyCategory 1 tank shall be not less than 1.6 mm nominalthickness low carbon steel or 1.2 mm stainless steel.The tank shall be made so that when completely filledin service no flat side shall bulge by an amount inexcess of 2 percent of the lesser dimension of that side.
3.2 CATEGORY 2 TANKS.
3.2.1 Size limitation. No tank shall be made toCategory 2 dimensions having a capacity in excess of2500 L.
3.2.2 Material. The material used to form anyCategory 2 tank shall be not less than 2 mm nominalthickness low carbon steel, or 1.6 mm stainless steel.For a vertical tank, the bottom shall be not less than3 mm nominal thickness low carbon steel or 2.5 mmstainless steel.
3.3 CATEGORY 3 TANKS.
3.3.1 Material. The material used to form anyCategory 3 tank shall be not less than the nominalthickness given in Table 3.1.
NOTE: Thicknesses are empirical, based on certain assumptionsthat are outlined in the Preface. Tanks that are rectangular or ofother unconventional shape should be treated with caution becauseof the difficult design problems involved.
3.3.2 Plate stiffness.Any rectangular tanks shall bemade so that when completely filled in service, no sideshall bulge by an amount in excess of 2 percent of thelesser dimension of that side.
3.4 CATEGORY 4 TANKS.
3.4.1 Material. The material used to form anyCategory 4 tank shall be not less than the nominalthickness given in Table 3.2. The thicknesses given inTable 3.2 are applicable to tanks whose length does notexceed 5 times their diameter. The design of tankswhose length/diameter ratio exceeds 5 shall bespecifically approved.
NOTE: Thicknesses are empirical, based on certain assumptionsthat are outlined in the Preface.
3.4.2 Tank ends. Any conical or dished end shall beformed to a height not less than that given in Table 3.3.Any flat end shall be stayed or stiffened in accordancewith AS 1210.
3.4.3 Placing of supports. The location of a supportin relation to the end of the tank shall be such that theshell will not fail due to loading in the vicinity of thesupport.
NOTE: BS 5500 provides methods for calculating stresses atsupports. Unusually long tanks on three supports require specialdesign (see Clause 3.4.1).
3.4.4 Construction. Any welded joint in a tank shallcomply with the following requirements, as applicable:
(a) Any longitudinal welded joint shall be a butt joint(see Figure 3.1(a)).
(b) Any circumferential welded joint in any tank whichwill incorporate pressure-vacuum venting, thepressure relief setting of which will exceed 14 kPa,shall be a butt joint or double-welded lap joint.
(c) Any dished internal bulkhead within a tank may bewelded on one side only.
(d) Any circumferential welded joint in any tank otherthan as described in (b) above may be of the formsshown in Figure 3.1, except where a purchaserspecifically requires that a lap joint be seal-weldedon the inside.
3.5 CATEGORY 5 TANKS.
3.5.1 Material. The material used to form anyCategory 5 tank shall be not less than the nominalthickness given in Table 3.4.
NOTE: Thicknesses are empirical, based on certain assumptionsthat are outlined in the Preface.
3.5.2 Flat tank bottom. Where a tank is intended tobe installed so that it rests on and is evenly andadequately supported over its entire bottom area, thebottom may be unstayed. If the tank is supported bymeans of a projecting rim, skirt, or legs without anyother support for the bottom, then the bottom, if flat,shall be stayed and stiffened in accordance withAS 1210.
3.5.3 Bolting down. Any Category 5 tank shallincorporate provisions for bolting down, sufficient towithstand the forces involved, in the followingcircumstances:
(a) Where wind loadings applicable for the site wouldotherwise be sufficient to cause dislodgment oroverturning of the tank when empty (seeAS 1170.2).
(b) Where an uplift force on a tank roof due to thepressure setting of a vent is greater than the massof the roof and shell.
3.5.4 Construction. Any welded joint shall complywith the following requirements, as applicable:
(a) Shell. Any longitudinal shell joint shall be a buttjoint and any circumferential shell joint should bea butt joint but may be a lap joint (see Figure 3.1).
(b) Bottom. If the tank rests on the tank bottom, thejoint between the shell and the bottom may be asingle-welded lap joint. If the tank is on legs, sucha joint shall be either a butt joint or a double-welded lap joint. Any transverse seam across a tankbottom may be made in the form of asingle-welded lap joint (with the weld inside) if thetank rests on the tank bottom, or a butt joint ordouble-welded lap joint if the tank is on legs.
(c) Tank top. Any of the types illustrated in Figure 3.1and Figure 3.2, as appropriate, may be used. If thetank will incorporate pressure-vacuum venting andthe pressure setting is over 14 kPa, the jointbetween the shell and the top shall be reinforced asillustrated in Figure 3.2(c), and the design shall bein accordance with BS 2654. This requirement doesnot apply where a tank is less than 3 m in
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diameter, nor where a tank irrespective of sizeincorporates a dished and flanged end.
3.6 CATEGORY 6 TANKS. A Category 6 tank shallcomply fully with BS 2654, API 620, API 650, or otherapproved Standard.
NOTES:1. Where the Standard chosen makes reference to another Standard
of its country of origin, an appropriate Australian Standard maybe substituted, provided that the substitution is appropriate andboth parties to the purchase contract are agreeable, and approvalhas been obtained. See AS 2624.
2. A list of preferred sizes for Category 6 tank diameters, in metricdimensions, is given in Appendix C of BS 2654.
TABLE 3.1
THICKNESS OF MATERIAL FOR RECTANGULAR TANKS OF CATEGORY 3
CapacityL
Minimum nominal thicknessmm
Thicknessvalid up to
heightmm
Increase thicknessfor each 1 mextra height
mmLow carbonsteel
Stainlesssteel
≤ 50> 50 ≤ 250> 250 ≤ 500> 500 ≤ 1200> 1200 ≤ 5000
0.81.01.63.05.0
0.60.81.02.54.0
0.51.01.01.51.5
0.50.50.51.51.5
> 5000 Each flat surface individually designed for the pressure
TABLE 3.2
THICKNESS, SHELLS AND ENDS FOR HORIZONTAL CYLINDRICALTANKS OF CATEGORY 4
(Applicable to all tanks whether for aboveground or underground installation)
Tank diametermm
Minimum nominal thickness, mm
Low carbon steel Stainless steel
≤ 1.53> 1.53 ≤ 2.20> 2.20 ≤ 2.75> 2.75 ≤ 3.75
3568
2.5456
TABLE 3.3
MINIMUM HEIGHT OF DISHED OR CONICAL ENDSFOR TANKS OF CATEGORY 4
Tank diameterm
Dished heightmm
≤ 1.53> 1.53 ≤ 2.20> 2.20 ≤ 2.75> 2.75 ≤ 3.75
4070110200
Note: The dished height does not include the straight length of any flange.i.e. dimensionF of Figure 3.1 is additional to the dished height>
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TABLE 3.4
THICKNESS, SHELLS AND ENDS FOR CYLINDRICAL VERTICAL TANKS OF CATEGORY 5
Tank diameterShell
(See Notes 3 and 4)Bottom
mmTopmm
mmFlat
(See Notes 2 and 4)Dished or coned
(See Notes 3 and 4) Flat Dished or coned
mLow
carbonsteel
Stainlesssteel
Lowcarbon
steel
Stainlesssteel
Lowcarbon
steel
Stainlesssteel
Lowcarbon
steel
StainlessSteel
Lowcarbon
steel
Stainlesssteel
≤ 1.53> 1.53 ≤ 2.20> 2.20 ≤ 2.75> 2.75 ≤ 3.75> 3.75 ≤ 4.5
35566
2.54455
66666
66666
3568
10
2.54568
35566
2.54455
33555
2.52.5444
> 4.5 Design as a Category 6 tank
NOTES:1. All thicknesses are nominal (see Clause 1.5.4).2. Flat bottoms are assumed to be fully supported over at least 60 percent of their area (see Clause 3.5.2).3. Dished or coned bottoms are assumed to be for tanks that rest on peripheral legs, so that the bottoms have no support. Tanks that are
particularly tall, so that the liquid head is high, should be checked in accordance with AS 1210 to verify the adequacy of the shell and bottomthicknesses. The shell should also be checked for adequacy at the point of attachment of legs.
4. Consideration should be given to increasing thicknesses where damage due to transport, handling, and erection is likely.
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FIGURE 3.1 (in part) TYPICAL JOINTS FOR TANKS
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FIGURE 3.1 (in part)
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FIGURE 3.2 VERTICAL TANKS—ROOF JOINTS
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APPENDIX A
INFORMATION TO BE PROVIDED BY THE PURCHASER
(This Appendix forms an integral part of this Standard.)
The purchaser should provide the tank manufacturer with such information as is necessaryto permit manufacture of the tank. In particular the following should be provided:
(a) Whether the tank is to be aboveground, or wholly or partly buried.
(b) The type and nature of the filling provision required.
(c) The test pressure, or the liquid head, or the pressure of operation.
(d) The type and location of the draw-off connection.
(e) Vent provision, i.e. the type, size, capacity, provision for any vent extension.
(f) Whether a manhole or manholes are required and their location.
(g) Whether a test certificate is required.
(h) Whether calibration of tank or contents indicator is required.
(i) Any finishing or protective coatings required.
(j) Density of the liquid if it exceeds 1000 kg/m3.
(k) Any special requirements regarding supports.
(l) Product being stored.
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