As 1692 Tanks for Flammable & Combustible Liquids

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AS 1692—1989

Australian Standard

R

Tanks for flammable and

combustible liquids

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This Australian Standard was prepared by Committee ME/17, Flammable & Combustible Liquids. It was approved on behalf of the Council of Standards Australia on 29 June 1989 and 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 to periodic review and are kept up to date by the issue of amendments or new editions as necessary. It is important therefore 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 Catalogue of Publications; this information is supplemented each month by the magazine ‘The Australian Standard’, which subscribing members receive, and which gives details of new publications, new editions and amendments, and of withdrawn Standards.

Suggestions for improvements to Australian Standards, addressed to the head office of Standards Australia, are welcomed. Notification of any inaccuracy or ambiguity found in an Australian Standard should be made without delay in order that the matter may be investigated and appropriate action taken.

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AS 1692—1989

Australian Standard

R

Tanks for flammable and

combustible 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 AS CB21.2—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 and Combustible Liquids, to supersede AS 1692–1983. The Standard was originally derived from AS CB5, Oil fuel installations, which was first issued in 1942. When AS 1940, SAA

Flammable and Combustible Liquids Code was issued in 1976, the requirements for the

construction of tanks, as distinct from their installation, were extracted to be dealt with in a separate reference standard.

At that time a decision was made to limit the Standard to steel tanks, largely as a matter of convenience and expediency, i.e. the framework already existed in AS CB5 and other Standards, and steel tanks were well understood and quite common, while requirements for other materials would have needed time to develop.

The 1983 edition extended the scope to include stainless steel tanks. Consideration was given to the inclusion of aluminium, but the very wide variety of alloys, with widely differing strengths and susceptibility to corrosion, made it difficult to recommend thicknesses with any degree of confidence. Since aluminium is not in widespread use, and is then mainly used in special cases where compatibility with the contents is a major consideration, it was decided to omit 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 for all tanks except Category 6 are empirical, being the result of experience rather than accurate stress calculations. It has been considered that stresses will be comparatively low and that the need for the tank to be reasonably sturdy for handling, or a need for corrosion allowance, and similar practical factors dictate the material thickness. Other limiting assumptions which have 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 a level 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 possibility of using thinner materials, compensating by special shaping, corrugating, bracing or stiffening, is recognized, especially for stainless steel. Any such alternatives may be admissible under Clause 1.6.

Outside these conditions, the assumptions and hence the requirements are no longer valid and specific approval may be necessary.

This Standard does not insist on compliance with any particular material Standards, or the use of specific grades of materials.

Tanks of glass–fibre reinforced plastics (GRP) are not covered in detail in this Standard although GRP is recognized as an alternative material. High cost has militated against widespread use, but construction is dealt with adequately in existing standards, except for underground 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 general trends. The new dimensions for stainless steel were derived from AS 2809.2, Tankers for

flammable liquids, in the absence of any other source.

The committee recognized that there are situations in which liquids other than petroleum derivatives 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 should be 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 DESIGNS AND INNOVATIONS 5. . . . 1.7 INTERPRETATIONS 5. . . . SECTION 2. GENERAL DESIGN AND CONSTRUCTION

2.1 GENERAL 6. . . . 2.2 CONTENTS INDICATOR 6. . . . 2.3 FILLING 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 HANDLING AND TRANSPORT 9. . . . SECTION 3. REQUIREMENTS FOR SPECIFIC CATEGORIES OF 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 THE

PURCHASER 16. . . .

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AS 1692—1989 4

STANDARDS AUSTRALIA

Australian Standard

Tanks for flammable and combustible liquids SECTION 1. SCOPE AND GENERAL

1.1 SCOPE. This Standard specifies requirements

for the design and construction of tanks for the

storage of flammable and combustible liquids,

together with certain accessories. It does not deal with their installation, nor does it deal with road, rail, or marine tankers, or with fuel tanks for vehicles. It is applicable only to the storage of materials that are liquid at normal temperatures and pressures.

NOTES:

1. This Standard is basically oriented towards cylindrical tanks of commercial grade low carbon steel for petroleum fuel storage, this being the most common application for tank storage, but it also provides for stainless steel tanks. Glass-fibre reinforced plastics are recognized alternative materials, but are dealt with in other Standards, notably BS 4994 and AS 2634. It is recognized that the storage of other types of liquid, or the use of other materials of construction, may render part or all of this Standard inappropriate; any such substitutions should be the subject of specific approval.

2. Attention is drawn to Appendix A, which sets out details of particular information that the purchaser needs to supply in order that the manufacturer can complete the tank.

1.2 CLASSIFICATION. Tanks within the scope of

this Standard are classified as follows:

(a) Category 1 — tanks up to 1200 L capacity, for aboveground use, intended principally for the storage of oil fuel in domestic type applications.

NOTE: Category 1 tanks cannot be used for the storage of flammable liquids as they do not incorporate a liquid seal.

(b) Category 2 — vertical or horizontal cylindrical tanks up to 2500 L capacity, for aboveground use, intended principally for farms and similar open space locations.

(c) Category 3 — rectangular tanks and tanks of unconventional shapes, intended principally for industrial use aboveground as either head tanks or storage tanks.

(d) Category 4 — horizontal cylindrical tanks up to

150 m3

capacity, for underground or aboveground use, intended principally for industrial or service station use.

(e) Category 5 — vertical cylindrical tanks up to 150

m3

capacity, for aboveground use, intended for industrial use.

(f) Category 6 — vertical tanks up to any capacity, of a size and type that is usually erected on site.

1.3 APPLICATION. Tanks in Categories 1 to 5

shall comply with all the relevant requirements of Section 2 and the specific requirements of Section 3, as appropriate to the category. Tanks in Category 6 shall comply with Clause 3.6.

1.4 REFERENCED DOCUMENTS. The following

documents are referred to in this Standard:

AS

1020 The control of undesirable static electricity

1170 SAA Loading Code

1170.2 Part 2: Wind forces

1210 SAA Unfired Pressure Vessels Code

1250 SAA Steel Structures Code

1554 SAA Structural Steel Welding Code

1657 SAA Code for Fixed Platforms, Walkways,

Stairways, and Ladders

1940 SAA Flammable and Combustible Liquids

Code

2624 Steel plate and strip for the construction of

welded steel tanks for oil storage

2634 Chemical plant equipment made from

glass-fibre reinforced plastics (GRP) based on thermosetting resins

BS

2654 Specification for the manufacture of vertical

steel welded storage tanks with butt-welded shells for the petroleum industry

4994 Specification for the design and construction

of vessels and tanks in reinforced plastics

5500 Specification for unfired fusion welded

pressure vessels API

620 Recommended rules for design and

construction of large, welded low-pressure storage tanks

650 Welded steel tanks for oil storage

ASTM

D 5 Test method for penetration of bituminous

materials.*

1.5 DEFINITIONS. For the purpose of this Standard, the definitions below apply:

1.5.1 Approved (approval) — approved by (approval

of) the authority concerned.

1.5.2 Authority, Authority having jurisdiction —

the authority having statutory (legal) control of the installation which incorporates the tank.

1.5.3 Liquid (flammable, combustible) — a

flammable liquid or a combustible liquid as defined in AS 1940.

1.5.4 Nominal thickness — the nominal thickness of

material which is commercially available and to

which specified manufacturing tolerances are

applicable.

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 total

volume which the tank will accept without spilling or leaking.

NOTE: It is recognized that the available capacity of a tank will normally be less than the full capacity, because of the need to provide an ullage space to allow for thermal expansion. A common practice is to allow 3 percent for ullage, but local regulations, or factors of the installation such as tank size, sheltered locations or underground installation can all have a bearing on the ultimate figure used.

1.6 NEW DESIGNS AND INNOVATIONS. Any

novel materials, designs, methods of assembly, procedures, etc, which do not comply with specific

requirements of this Standard, are not necessarily prohibited. SAA Committee ME/17, Flammable and Combustible Liquids, can act in an advisory capacity concerning equivalent suitability, but the specific approval remains the prerogative of the Authority.

1.7 INTERPRETATIONS. Questions concerning

the meaning, application or effect of any part of this specification may be referred to SAA Committee ME/17, Flammable and Combustible Liquids, for explanation. The authority of this committee is limited to matters of interpretation and it will not adjudicate 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 storage

tank shall be such as will ensure that it is adequate for any load and pressure to which it may be subjected, and shall take into account any corrosive or other abnormal conditions. Any method of construction or material that is not specifically dealt with herein shall be applied in conformity with good engineering practice. Any weld-on fittings, flanges, nozzles, and the like, shall be compatible with the material of the tank and the welding process.

2.1.2 Material. Any material used in the construction of a tank shall be of a type and quality suitable for the conditions of use, and compatible with the liquid being stored. Material should comply

with any relevant Australian Standard, or an

appropriate other Standard if no Australian Standard exists.

2.1.3 Welding. Any welded joint shall comply with

the applicable requirements of AS 1554, weld category GP.

2.1.4 Finish and protective coatings. Any internal

or external protective coatings shall be sufficient to ensure satisfactory life of the tank and its supports. Particular attention should be paid to the following: (a) The soil or atmospheric conditions surrounding

the tank.

(b) Compatibility of internal coatings with the contents of the tank.

(c) Protection of areas particularly vulnerable to

corrosion, e.g. points of contact with the

supports, rainwater traps.

(d) The specific requirements for surface preparation and coatings where cathodic protection is used.

2.1.5 Supports. Any supporting structure that is

supplied with the tank shall comply with the structural code applicable for the particular material, e.g. AS 1250 for steel supports. Any welded-on supports, brackets or other fittings shall be welded so that the penetration of moisture in a manner likely to cause corrosion of the tank shell is prevented.

NOTE: Particular attention should be paid to the method of transmitting loads between the tank shell and the supports, so that 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 pipe

entries to a tank intended to be wholly buried below ground level shall be through the top of the tank unless specifically approved otherwise.

2.1.7 Liquid seal. Every fill pipe, suction pipe, or

dip pipe that enters through the top of a tank and that is likely to be opened to atmosphere at some time during a normal filling procedure shall be provided with a liquid seal sufficient to ensure that the bottom end of the pipe is submerged in not less than 25 mm of liquid at all times subsequent to the initial filling.

Tanks of Category 1 are exempt from this

requirement.

NOTE: Figure 2.1 illustrates typical arrangements.

2.1.8 Access ladders and structures. Any access

structure shall comply with AS 1657. The design shall be such that there is no differential movement between the tank and the structure.

2.2 CONTENTS INDICATOR.

2.2.1 Indicator required. Each storage tank shall

be provided with a means for ascertaining the liquid level. If the indicator is of a type designed for reading at a remote location, additional facilities for

checking its accuracy shall be provided. The

maximum permitted filling level shall be indicated on the 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 (gauge glasses).

2.2.2 Dipstick. Any dipstick-indicating system shall

comply with the following requirements:

(a) The opening shall be provided with a cap which shall be liquid-tight and vapour-tight unless a common dip and vent is used on aboveground tanks.

(b) Where a dipstick measures by contacting the bottom of the tank, a tubular dipstick guide shall be provided. The guide shall incorporate a pressure equalizer hole which connects the upper end of the dip pipe with the upper tank space. This hole, if over 1.5 mm diameter, shall be covered by an antiflash gauze not coarser than 600 µm mesh. A durable striker pad shall be attached firmly to the tank bottom below the dip opening, other than for tanks of Categories 1 and 2.

(c) Any dipstick for a tank intended to contain

flammable liquids shall be of non-ferrous

material.

2.2.3 Sight tubes. A sight tube of the type commonly known as a gauge glass shall not be fitted to any tank storing flammable liquids and should not be used for any other class of liquid unless such use is unavoidable. Where a gauge glass is unavoidable – (a) an adequate protective guard for the tube shall be

provided;

(b) the material of the sight tube shall be unaffected by the liquid used; and

(c) a self-closing shut-off valve shall be provided on any connecting leg that is below liquid level.

2.3 FILLING PROVISIONS.

2.3.1 General. Each tank shall be provided with a

means of filling to suit the intended method of filling and the location of the fill point in relation to the tank.

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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7 AS 1692—1989

2.3.2 Fill pipe. The filling provision on every tank

other than a Category 1 tank shall be such that liquid is conducted through a fully enclosed pipe to a discharge point which is not more than one diameter of the pipe above the tank bottom.

Where filling is from the top, an extension pipe shall be used to achieve compliance with this requirement. Where a side entry into a vertical tank requires to be reinforced, the discharge point may be located high enough to accommodate the reinforcing ring, but should be not more than 150 mm from the tank bottom.

NOTE: This requirement is intended to ensure that splashing during filling, which may result in the generation of static electricity, is minimized. See AS 1020.

2.3.3 Pressure equalization. Any fill pipe that fills

downwards into a tank shall incorporate a pressure equalizer hole which connects the upper end of the pipe with the upper tank space. This hole, if over 1.5 mm diameter, shall be covered by an antiflash gauze

not coarser than 600µm mesh.

2.3.4 High-head filling. Where the height of the

filling point above the tank is such that the pressure on the tank will exceed the test pressures described in Clause 2.7, the tank shall incorporate a provision to prevent the liquid level from rising above the tank-full condition or the tank shall be designed and tested to withstand the additional pressure of a liquid-full filling extension.

2.4 DRAINING AND NORMAL DRAW-OFF. 2.4.1 General. It shall be possible to remove the

entire liquid contents from a tank without removing the tank from its installed position.

NOTE: Where the conditions of installation are such that draining by gravity through a bottom outlet cannot be provided, e.g. an underground tank, facilities for the insertion of a suction spear through a fill pipe or other opening will be deemed to comply with this requirement.

2.4.2 Drain outlet location. Any drain provision

should draw from the lowest point of the tank and, if separate from the liquid draw-off pipe, should be located as far as possible from the draw-off pipe.

2.5 MANHOLES.

2.5.1 Where required. A manhole shall be provided

when specified by the tank purchaser.

NOTE: A manhole is not an essential for tank safety, but may be convenient 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 not

less 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 the tank is to be installed with a slope, and in such cases adequate correction must be made in order to maintain the 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 personnel entering the tank, a manhole should be not less than 600 mm diameter.

2. Fixed ladders within the tank may be necessary to provide reasonable means of access.

2.5.3 Multiple manholes. Where a vertical tank over

3 m high is required to have a manhole, and the manhole is required to be near the top of the tank, a second manhole shall be provided adjacent to the bottom of the tank. Alternatively, if a single manhole is located adjacent to the bottom of the tank, no other manhole is required unless specified by the purchaser.

2.5.4 Manhole covers. Each manhole shall be provided with a cover which shall be vapour-tight and liquid-tight at the test pressure.

2.6 TANK VENTS.

2.6.1 General. Each tank shall incorporate a provision

to vent to atmosphere the vapour space above the liquid. The vent may be combined with the filling provision for a Category 1 tank; for all other tanks a vent shall be separate from the fill orifice. The venting provision may be one of the following:

(a) Free venting, in which the vapour space is in contact with the atmosphere without any intervening valves or other devices, so that the pressure above the liquid is substantially that of the surrounding atmosphere.

(b) Pressure-vacuum venting, in which a control device permits a positive or negative pressure within the tank to reach a predetermined level before the pressure or vacuum is relieved.

(c) Emergency venting, used to supplement (a) and (b), in which excessive pressure built up in emergency conditions such as fire is relieved by means of a pressure-relief device.

2.6.2 Size of vent. The size of any free vent or

pressure-vacuum vent shall be such that pressure or

vacuum resulting from filling or emptying or

atmospheric temperature change will not cause stresses in excess of the normal maximum design stress. In determining the size of the vent connection, the following requirements shall apply:

(a) Where a free vent in a Category 1 tank is combined with the filler, the opening shall provide not less

than 600 mm2

of free vent area with the nozzle

inserted and 10 mm2

with the cap in place. (b) For a separate free vent in a tank of Category 1 or

Category 2, the vent area shall be not less than the equivalent of a 25 mm nominal internal diameter pipe.

(c) For any other category of tank, the vent provision or the vent connection facilities shall be those specified by the purchaser of the tank.

NOTE: The design of the vent, and particularly its size, are dependent on factors that relate to the specific installation; therefore a tank manufacturer would not normally undertake to design and size the vent without instructions from the purchaser. AS 1940 provides requirements to assist in vent design.

2.6.3 Vent terminal. The discharge end of any free

vent supplied as part of a tank shall be protected from the ingress of foreign material, e.g. by a return bend or a protective cap, cage, or fitting. Any such fitting shall not reduce the required vent area. The discharge point

shall be higher than the filling point and not less than 150 mm above the tank top.

2.7 TESTING.

2.7.1 Leakage test. Each tank shall be subjected to a

leakage test before any painting, coating, or similar treatment is applied, and shall be found to be sound and liquid-tight before being put into service. A hydrostatic test method should be used, but air testing may be applied in the conditions specified in Clause 2.7.3 to any tank except those in Category 3 or Category 6. When hydrostatically testing, a tank shall be tested in the orientation of its operation, i.e. vertical tanks shall be tested when vertical, horizontal tanks tested when horizontal.

NOTE: Any flat side or end may be supported during testing, provided that the method of support does not inhibit the observation of any leak.

2.7.2 Hydrostatic testing. Any hydrostatic test shall

be carried out in accordance with the following requirements, as applicable:

(a) For any free-vented tank in Category 1, Category 2, Category 4 or Category 5, the test pressure shall be that caused when the tank is filled with water and 1m additional water head is applied. Where the tank filling or operating pressure will exceed the equivalent of 1m head above the top of the tank, the test pressure shall be that maximum pressure plus 1m head of water.

(b) For any free-vented Category 3 tank, the test pressure shall be as in (a) above, except that the additional head shall be reduced to 150 mm. (c) For any Category 6 tank, the test pressure and

procedure shall be that given in the Standard to which the tank was built.

(d) Where a pressure-vacuum or emergency vent is to be used with the tank, the test pressure shall be as in (a) above, plus 35 kPa.

(e) The test pressure shall be applied for sufficient time to allow any leaks to develop and to be observed.

NOTE: The purchaser is free to specify higher test pressures, but the design of the tank should be checked for its ability to withstand any such higher pressures.

2.7.3 Air testing. Any air test shall be conducted in

accordance 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 safety and workplace safety at the testing site.

(c) The test pressure shall be that which will stress to a level equivalent to that which would be caused by the appropriate hydrostatic test pressure, provided that the test pressure shall not exceed 35 kPa without the approval of the Authority responsible for pressure vessel and workplace safety at the testing site. If approval for such test pressure cannot

be obtained, then a hydrostatic test as in

Clause 2.7.2 shall be applied.

(d) When air for testing is taken from a source of supply having a pressure greater than 35 kPa, pressure shall be reduced by means of a pressure reducing device; a pressure gauge, a safety valve, or hydrostatic pressure-relieving device, and a pressure release cock shall be fitted on the low pressure side. COPYRIGHT

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9 AS 1692—1989

(e) A tank that is to be filled from a filling point more than 1 m above the tank shell shall be tested at the head resulting from the filling location, plus an additional 1 m head of water. (f) The pressure-relieving device shall be capable of

discharging the maximum delivery of the

pressure-reducing device without rise in pressure beyond 110 percent of the test pressure.

(g) The tank shall not be subjected to blows while under air pressure.

(h) Air for testing shall be introduced gradually and evenly until the test pressure has been reached. (i) The test pressure shall be applied for sufficient

time to allow any leaks to develop and to be observed.

2.8 HANDLING AND TRANSPORT. Any tank

which could suffer damage because of stresses caused by handling and transportation shall be provided with adequate supports and stays to protect it until it has been installed.

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AS 1692—1989 10

SECTION 3. REQUIREMENTS FOR SPECIFIC CATEGORIES OF TANKS

3.1 CATEGORY 1 TANKS.

3.1.1 Size limitation. No tank shall be made to

Category 1 dimensions having a capacity in excess of 1200 L.

3.1.2 Material. The material used to form any

Category 1 tank shall be not less than 1.6 mm nominal thickness low carbon steel or 1.2 mm stainless steel. The tank shall be made so that when completely filled in service no flat side shall bulge by an amount in excess 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 to

Category 2 dimensions having a capacity in excess of 2500 L.

3.2.2 Material. The material used to form any

Category 2 tank shall be not less than 2 mm nominal thickness low carbon steel, or 1.6 mm stainless steel. For a vertical tank, the bottom shall be not less than 3 mm nominal thickness low carbon steel or 2.5 mm stainless steel.

3.3 CATEGORY 3 TANKS.

3.3.1 Material. The material used to form any

Category 3 tank shall be not less than the nominal thickness given in Table 3.1.

NOTE: Thicknesses are empirical, based on certain assumptions that are outlined in the Preface. Tanks that are rectangular or of other unconventional shape should be treated with caution because of the difficult design problems involved.

3.3.2 Plate stiffness. Any rectangular tanks shall be

made so that when completely filled in service, no side shall bulge by an amount in excess of 2 percent of the lesser dimension of that side.

3.4 CATEGORY 4 TANKS.

3.4.1 Material. The material used to form any

Category 4 tank shall be not less than the nominal thickness given in Table 3.2. The thicknesses given in Table 3.2 are applicable to tanks whose length does not exceed 5 times their diameter. The design of tanks whose length/diameter ratio exceeds 5 shall be specifically approved.

NOTE: Thicknesses are empirical, based on certain assumptions that are outlined in the Preface.

3.4.2 Tank ends. Any conical or dished end shall be

formed to a height not less than that given in Table 3.3. Any flat end shall be stayed or stiffened in accordance with AS 1210.

3.4.3 Placing of supports. The location of a support

in relation to the end of the tank shall be such that the shell will not fail due to loading in the vicinity of the support.

NOTE: BS 5500 provides methods for calculating stresses at supports. Unusually long tanks on three supports require special design (see Clause 3.4.1).

3.4.4 Construction. Any welded joint in a tank shall

comply 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 which will incorporate pressure-vacuum venting, the pressure 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 be

welded on one side only.

(d) Any circumferential welded joint in any tank other than as described in (b) above may be of the forms shown in Figure 3.1, except where a purchaser specifically requires that a lap joint be seal-welded on the inside.

3.5 CATEGORY 5 TANKS.

3.5.1 Material. The material used to form any

Category 5 tank shall be not less than the nominal thickness given in Table 3.4.

NOTE: Thicknesses are empirical, based on certain assumptions that are outlined in the Preface.

3.5.2 Flat tank bottom. Where a tank is intended to

be installed so that it rests on and is evenly and adequately supported over its entire bottom area, the bottom may be unstayed. If the tank is supported by means of a projecting rim, skirt, or legs without any other support for the bottom, then the bottom, if flat, shall be stayed and stiffened in accordance with AS 1210.

3.5.3 Bolting down. Any Category 5 tank shall

incorporate provisions for bolting down, sufficient to withstand the forces involved, in the following circumstances:

(a) Where wind loadings applicable for the site would otherwise be sufficient to cause dislodgment or

overturning of the tank when empty (see

AS 1170.2).

(b) Where an uplift force on a tank roof due to the pressure setting of a vent is greater than the mass of the roof and shell.

3.5.4 Construction. Any welded joint shall comply

with the following requirements, as applicable: (a) Shell. Any longitudinal shell joint shall be a butt

joint and any circumferential shell joint should be a butt joint but may be a lap joint (see Figure 3.1). (b) Bottom. If the tank rests on the tank bottom, the joint between the shell and the bottom may be a single-welded lap joint. If the tank is on legs, such a joint shall be either a butt joint or a double-welded lap joint. Any transverse seam across a tank

bottom may be made in the form of a

single-welded lap joint (with the weld inside) if the tank rests on the tank bottom, or a butt joint or double-welded lap joint if the tank is on legs. (c) Tank top. Any of the types illustrated in Figure 3.1

and Figure 3.2, as appropriate, may be used. If the tank will incorporate pressure-vacuum venting and the pressure setting is over 14 kPa, the joint between the shell and the top shall be reinforced as illustrated in Figure 3.2(c), and the design shall be in accordance with BS 2654. This requirement does not apply where a tank is less than 3 m in COPYRIGHT

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11 AS 1692—1989

diameter, nor where a tank irrespective of size incorporates a dished and flanged end.

3.6 CATEGORY 6 TANKS. A Category 6 tank shall

comply fully with BS 2654, API 620, API 650, or other approved Standard.

NOTES:

1. Where the Standard chosen makes reference to another Standard

of its country of origin, an appropriate Australian Standard may be substituted, provided that the substitution is appropriate and both parties to the purchase contract are agreeable, and approval has been obtained. See AS 2624.

2. A list of preferred sizes for Category 6 tank diameters, in metric dimensions, is given in Appendix C of BS 2654.

TABLE 3.1

THICKNESS OF MATERIAL FOR RECTANGULAR TANKS OF CATEGORY 3

Capacity L

Minimum nominal thickness mm Thickness valid up to height mm Increase thickness for each 1 m extra height mm Low carbon steel Stainless steel ≤50 > 50 ≤250 > 250 ≤500 > 500 ≤1200 > 1200 ≤5000 0.8 1.0 1.6 3.0 5.0 0.6 0.8 1.0 2.5 4.0 0.5 1.0 1.0 1.5 1.5 0.5 0.5 0.5 1.5 1.5 > 5000 Each flat surface individually designed for the pressure

TABLE 3.2

THICKNESS, SHELLS AND ENDS FOR HORIZONTAL CYLINDRICAL TANKS OF CATEGORY 4

(Applicable to all tanks whether for aboveground or underground installation)

Tank diameter mm

Minimum nominal thickness, mm Low carbon steel Stainless steel

≤1.53 > 1.53 ≤2.20 > 2.20 ≤2.75 > 2.75 ≤3.75 3 5 6 8 2.5 4 5 6 TABLE 3.3

MINIMUM HEIGHT OF DISHED OR CONICAL ENDS FOR TANKS OF CATEGORY 4

Tank diameter m Dished height mm ≤1.53 > 1.53 ≤2.20 > 2.20 ≤2.75 > 2.75 ≤3.75 40 70 110 200

Note: The dished height does not include the straight length of any flange. i.e. dimension F of Figure 3.1 is additional to the dished height>

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AS 1692—1989 12

TABLE 3.4

THICKNESS, SHELLS AND ENDS FOR CYLINDRICAL VERTICAL TANKS OF CATEGORY 5

Tank diameter

Shell (See Notes 3 and 4)

Bottom mm Top mm mm Flat (See Notes 2 and 4)

Dished or coned

(See Notes 3 and 4) Flat Dished or coned

m Low carbon steel Stainless steel Low carbon steel Stainless steel Low carbon steel Stainless steel Low carbon steel Stainless Steel Low carbon steel Stainless steel ≤1.53 > 1.53 ≤2.20 > 2.20 ≤2.75 > 2.75 ≤3.75 > 3.75 ≤4.5 3 5 5 6 6 2.5 4 4 5 5 6 6 6 6 6 6 6 6 6 6 3 5 6 8 10 2.5 4 5 6 8 3 5 5 6 6 2.5 4 4 5 5 3 3 5 5 5 2.5 2.5 4 4 4

> 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 bottom thicknesses. 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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13 AS 1692—1989

FIGURE 3.1 (in part) TYPICAL JOINTS FOR TANKS

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AS 1692—1989 14

FIGURE 3.1 (in part)

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15 AS 1692—1989

FIGURE 3.2 VERTICAL TANKS—ROOF JOINTS

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AS 1692—1989 16

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 necessary to 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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Figure

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References

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