INTERNATIONAL MARITIME ORGANIZATION E IMO SUB-COMMITTEE ON DANGEROUS GOODS, SOLID CARGOES AND CONTAINERS 7th session Agenda item 3 DSC 7/3/5 20 June 2002 Original: ENGLISH AMENDMENTS TO THE IMDG CODE, ITS ES AND SUPPLEMENTS (EmS, MFAG), INCLUDING HARMONISATION OF THE IMDG CODE WITH THE UN RECOMMENDATIONS ON THE TRANSPORT OF DANGEROUS GOODS Amendments to the IMDC Code, its annexes and supplements Proposal for an MSC Circular on IMO Type Portable Tanks Submitted by the United Kingdom Executive summary: Action to be taken: Paragraph 3 Related documents: Introduction SUMMARY This is a proposal to publish an MSC Circular containing the transitional provisions required for existing IMO type portable tanks and road tank vehicles to assist tank manufacturers and operators, inspecting and certifying authorities, consignors and shippers. This proposal is based on IMDG Code Amendment 29 Section 13. IMDG Code Amendment 30 paragraph 4.2.0, IMDG Code Amendment 29 Section 13, DSC 7/3 paragraph 15 1 The Maritime Safety Committee at its seventy-second session adopted the finalised Amendment 30 to the IMDG Code with an entry into force date of 1 January 2001 and a 12 month transitional period ending 31 December 2001. However, there are further transitional periods for IMO type portable tanks and road tank vehicles that extend their use in some cases to 1 January 2010 and beyond. The detailed provisions for such tanks are contained in Section 13 of the IMDG Code Amendment 29 but have not been reproduced in the reformatted IMDG Code Amendment 30 Details of the proposal 2 The IMDG Code Amendment 30 incorporated provisions for multimodal UN tanks and road tank vehicles for the transport of dangerous goods. New portable tanks are required to comply with these provisions from 1 January 2001. The reformatted Code however, also permits IMO type portable tanks and road tank vehicles designed, constructed and operated in accordance with provisions in the IMDG Code Amendment 29. These tanks are to be phased out over a period of years depending on certain conditions. For example, IMO type tanks could be For reasons of economy, this document is printed in a limited number. Delegates are kindly asked to bring their copies to meetings and not to request additional copies.
- 2 - constructed certified and approved to meet the provisions of IMDG Code Amendment 29 until 1 January 2003 and continue in use thereafter till 1 January 2010 or in some cases beyond that date unless they failed to meet the inspection, survey and test requirements of the Code. 3 The United Kingdom believes that provisions applicable to tanks in existence before 1 January 2003 should be readily available to those involved in the continued operations of these tanks. While it was not considered feasible to reproduce these provisions in every amendment of the Code until they become void, the Editorial & Technical Working Group invited the United Kingdom to submit a proposal to the Committee for the issue of an MSC Circular which could then be referred to in subsequent amendments to the Code. (DSC 7/3 15) 4 A draft of the provisions that could form the basis for such a circular is annexed to this submission. Action requested of the Committee 5 The Committee is invited to consider the publication of an MSC Circular as outlined above, containing the relevant provisions for existing IMO type portable tanks and road tank vehicles. ***
GUIDELINES ON THE APPLICATION OF THE TRANSITIONAL PROVISIONS FOR PORTABLE TANKS AND ROAD TANK VEHICLES CERTIFIED AND APPROVED PRIOR TO 1 JANUARY 2003 FOR THE CARRIAGE OF DANGEROUS GOODS AND MARINE POLLUTANTS 1.0 Introduction 1.1 The provisions of the United Nations Recommendations on the Transport of Dangerous Goods Model Regulations 11 th edition concerning multimodal portable tanks have been included in the IMDG Code Amendment 30 00. Tanks constructed certified and approved to these requirements are referred to as UN portable tanks in this guidance. The Code as amended entered into force on 1 January 2002. The Code includes transitional provisions for IMO type portable tanks and road tank vehicles constructed, certified and approved before 1 January 2003 under certain conditions. Definitions of the IMO tank types to which these transitional provisions apply can be found in the Note to paragraph 4.2.0 in chapter 4.2 of the IMDG Code. (Unless otherwise stated, any reference to the IMDG Code refers to the IMDG Code Amendment 30-00 and subsequent amendments) The purpose of this circular is to provide guidance for the use of tank manufacturers and operators, certifying and inspection authorities, consignors and others engaged in the carriage of dangerous goods and marine pollutants in IMO portable tanks and road tank vehicles constructed, certified and approved before 1 January 2003. 1.2 The transitional provisions are summarised below: - The acceptance of new IMO type portable tanks and road tank vehicles constructed and approved according to the requirements of the 29 th Amendment 29-98 (Section 13) or as modified by IMDG Code Amendment 30-00 are permitted until 1 January 2003 (see 4.2.0 of IMDG Code Amendment 30-00.) - The use of all IMO type portable tanks and road tank vehicles constructed prior to 1 January 2003 according to the requirements of IMDG Code Amendment 29-98 are permitted until 1 January 2010 provided that they remain safe for use and are inspected and tested at the required intervals given in IMDG Code chapter 6.7 and they are used only for those substances indicated in column 12 of the Dangerous Goods List in chapter 3.2 of the IMDG Code - The use of all IMO type portable tanks and road tank vehicles constructed prior to 1 January 2003 according to the requirements of IMDG Code Amendment 29-98 are permitted until the end of their life provided that: the test or maximum allowable working pressures, outlet arrangements, emergency pressure relief devices; minimum shell thickness requirements and other details correspond to those required for the T-code assigned to
Page 2 UN portable tanks permitted for the carriage of the substance or substances in them in accordance with the Dangerous Goods List in the IMDG Code and they remain safe for use and are inspected and tested at the required intervals given in IMDG Code chapter 6.7 - Where one or more design parameters required by IMDG Code Amendment 29-98 for an IMO type portable tank are more stringent than required for a UN portable tank for a particular substance in the Dangerous Goods List in chapter 3.2, IMO type tanks meeting the requirements for UN portable tanks may be used with immediate effect provided that all other parameters meet the requirements for UN portable tanks. There is no need to re-certify the IMO portable tank as a UN portable tank. 1.3 There are some differences in the terminology and requirements for the design and construction of IMO type portable tanks and the provisions those for UN portable tanks. These guidelines indicate those requirements from IMDG Code Amendment 29 98 which differ from the provisions for UN portable tanks and can be used instead of them, until the IMO portable tanks have been withdrawn from maritime service. [Where there is no significant difference in the requirements of IMDG Code Amendment 29-98, the requirements of IMDG Code chapters 4.2 and 6.7 should be followed. ] 1.4 Use of IMO type 4, 6 and 8 tanks IMO tanks types 4, 6 and 8 (road tank vehicles) must be used only as permitted under the conditions specified in the IMDG Code 2000 edition paragraph 4.2.5. 1.5 Off-shore portable tanks. Off-shore portable tanks designed and constructed to the requirements of IMDG Code Amendment 29-98 and applicable MSC Circulars may continue in use in the same manner as outlined earlier in these guidance. The requirements of the applicable MSC Circulars should also be followed until superseded. 2.0 General requirements for the use, design, construction, inspection and testing of IMO type portable tanks and road tank vehicle In general, the provisions of chapters 4.2, 6.7, 6.8 and 6.9 of the IMDG Code are applicable to IMO type tanks. Any exceptions to these provisions are indicated in the section below and are taken from IMDG Code Amendment 29-98 Section 13. 3.0 General requirements for IMO type 1 and type 2 portable tanks and IMO type 4 tanks for substances other than class 2. The provisions of 6.7.2 and 6.8.3.1 of the IMDG Code apply IMO type 1 and type 2 portable tanks and IMO type 4 tanks as appropriate except that the provisions in the sections below taken from the IMDG Code Amendment 29-98 section 13 may be substituted for certain provisions identified in the sub-section.
Page 3 3.1 Definitions The following definitions shall apply to IMO portable tanks: 3.1.1 Maximum allowable working pressure (MAWP) means a pressure that is not less than the higher of the following two pressures, measured at the top of the tank while in operating position:.1 the highest effective pressure allowed in the shell during filling or discharge; or.2 the maximum effective gauge pressure to which tanks for liquids should be designed, which is the sum of the following partial pressures minus 1 bar:.2.1 the vapour pressure (in bar) at 65 C; and.2.2 the partial pressure (in bar) of air or other gases in the ullage space being determined by a maximum ullage temperature of 65 C and a liquid expansion due to the increase of the bulk mean temperature of t r - t f (t f =filling temperature, usually 15 C; t r =50 C; the maximum mean bulk temperature). 3.1.2 Test pressure means the maximum gauge pressure at the top of a tank during a hydraulic test. 3.1.3 Design pressure means the pressure used, according to a recognised pressure vessel code for the design of every element of the tank. The design pressure should never be less than the highest of the following three pressures:.1 the working pressure as given in 3.1.1.1 of this guidance; or.2 the sum of the pressure as given in 3.1.1.2 of this guidance and the dynamic head pressure, determined on the basis of the dynamic forces due to inertia specified in 3.3.1 minus 1.0 bar; such a dynamic head pressure should never be taken to be less than 0.35 bar; or.3 the required test pressure divided by 1.5. 3.1.4 Start-to-discharge pressure means the value of increasing static pressure below which no bubbling occurs when a pressure-relief valve is tested by means of air under water seal at the outlet. 3.1.5 Road tank vehicle is a vehicle fitted with a tank complying with the relevant requirements for type 1 or 2 portable tanks or is a type 4 tank, intended for the transport of dangerous liquids by both road and sea modes of transport, the tank of which is permanently or rigidly attached to the vehicle during all normal operations of loading, discharging and transport and is neither filled nor discharged on board and is driven on board on its own wheels.
Page 4 3.2 General requirements for the design, construction and operation of tanks constructed before 1 January 2003 The following modification of the requirements shall apply to the design of IMO portable tanks. 3.2.1 In 6.7.2.2.1, chapter 6.7, the provision for fine grain steels when used to construct portable tanks, to have a guaranteed yield strength maximum of 460 N/mm2 and tensile strength limit of 725 N/mm2 is not required. [However, in so far as it is possible, these provisions should be taken into account in selecting materials for the repair of IMO portable tanks.] 3.2.2 The use of aluminium as a construction material for UN Portable Tanks is either authorised in the Dangerous Goods List or by approval of the competent authority. In 6.7.2.2.1, chapter 6.7, when authorised, the provision for aluminium to be insulated to prevent significant loss of physical properties when subjected to a heat load of 110 kw/m 2 is not required. [Nevertheless these requirements should be taken into account aluminium has been used as a material of construction for IMO portable tanks intended for liquids.] [IMO portable tanks authorised for liquids according to IMDG Code Amendment 29 98 but not in compliance with the insulation requirements of IMDG Code 6.7.2.2.1 of chapter 6.7 should not be authorised for use in this condition after.1 January 2010.] 3.2.3 In general, tanks should be designed and manufactured to withstand a test pressure equal to at least 1.5 times the maximum allowable working pressure. Specific requirements are laid down for various substances authorised to be carried in tanks in the Chapter 3.2 Dangerous Goods List in the IMDG Code. In any case, the test pressure should never be lower than 1.5 bar. 3.3 Design criteria The following requirements shall apply instead of the requirements of 6.7.2.2.12 of chapter 6.7: 3.3.1 Tanks and their fastenings should, under the maximum permissible load, be capable of absorbing the following dynamic forces:.1 in the direction of travel: twice the total mass;.2 horizontally at right angles to the direction of travel: the total mass (where the direction of travel is not clearly determined, the maximum permissible load should be equal to twice the total mass);.3 vertically upwards: the total mass; and.4 vertically downwards: twice the total mass (total loading including the effect of gravity).
Page 5 3.3.2 Under each of these loads, the safety factors to be observed for the primary combined stress should be as follows:.1 for metals having a clearly defined yield point, a safety factor of 1.5 in relation to the determined yield stress; or.2 for metals with no clearly defined yield point, a safety factor of 1.5 in relation to the guaranteed 0.2% (1.0% for austenitic steels) proof stress. Note: The above loads do not give rise to an increase in the pressure in the vapour space. 3.3.3 The specimens used to determine the elongation at fracture should be taken transversely to the direction of rolling and be so secured that: where: Lo = 5d, or Lo = 5.65 A Lo = gauge length of the specimen before the test; d = diameter; and A = cross-sectional area of the test specimen. The provision in 6.7.2.3.3.4 is to require permanent elongations at fracture to be measured in accordance with ISO 6892:1998 using a 50mm gauge length. [As far as possible this requirement should be followed.] [3.3.4 Materials with an Re/Rm ratio greater than 0.85 are not allowed for the construction of welded UN portable tanks (see 6.7.2.3.3.3, chapter 6.7). These limitations were not imposed on IMO portable tanks according to the requirements of Amendment 29 98. Nevertheless these requirements should be taken into account as far as practicable for IMO portable tanks including the requirements of 6.7.2.3.3.4 of chapter 6.7 regarding the determination of these values.] 3.4 Minimum shell thickness Instead of the requirements at 6.7.2.4.6 and 6.7.2.4.7 of chapter 6.7 the following requirements shall apply to the determination of minimum shell thickness. 3.4.1 The cylindrical portions and ends of tanks should have a thickness of not less than that determined by the following formula *: e = C. 3 (Rm x A)
Page 6 where: e = minimum required thickness of the metal to be used, in mm; Rm = guaranteed minimum tensile strength of the metal to be used, in N/mm2; A = guaranteed minimum elongation (as a percentage) of the metal to be used on fracture under tensile stress; see 6.7.2.3.3, C = 107 (equivalent to 5 mm mild steel) for tanks intended for the transport of powdery or granular solid substances and for tanks of not more than 1.80 m in diameter intended for the transport of liquids or C = 128 (equivalent to 6 mm mild steel) for tanks of more than1.80 m in diameter. *The constant C is derived from the following formula: e 3 (Rm x A) = e o 3 (Rm o x A o ), where the sub-index `o' refers to mild steel and the part of the equation without sub-index `o' refers to the metal used. The relationship with mild steel as employed by this Code is attached to the constant C, where C = e o 3 (Rm o x A o ). 3.4.2 Where additional thickness of the shell is required for certain dangerous substances, the table below shows the value of the constant C to used for calculation purposes: Minimum shell thickness in mild steel: 6 mm 8 mm 10 mm 12 mm "C" to be used for calculation is: 128 171 213 256 3.4.3 Except as provided in 3.4.4, the cylindrical portions and ends of all tanks should have a thickness of at least 3 mm regardless of the material of construction. 3.4.4 Where additional protection of the tanks against damage is provided, the competent authority may, for a tank having a test pressure below 2.65 bar (i.e. type 2 portable tank), authorise a reduction in the minimum thickness in proportion to the protection provided. For such protected tanks the thickness should not be less than that determined in accordance with 3.4.2, where: C = 64 (equivalent to 3 mm mild steel) for tanks of not more than 1.80 m in diameter; and C = 85 (equivalent to 4 mm mild steel) for tanks of more than 1.80 m in diameter. These requirements shall supplement the requirements of 6.7.2.4.3 of chapter 6.7 for tanks with a test pressure less than 2.65 bar. Note: Transitional arrangements apply to the shell thickness requirements for certain substances.
Page 7 3.5 Capacity of relief devices The requirements of 6.7.2.12 of chapter 6.7 shall apply to the determination of the total capacity of relief devices with the exception of the melting point of insulation jackets which may be taken as 649 o C in place of 700 o C. 3.6 Marking of pressure-relief devices The requirements of 6.7.2.13 of chapter 6.7 shall apply to IMO portable tanks with the exception that where the rated flow capacity has been determined in some other way than is prescribed in ISO 4126-1:1996, the alternative standard used shall be marked on the device. 3.7 Design approval The requirements of 6.7.2.18 of chapter 6.7 shall apply to Imo portable tanks. Where the distinguishing sign or mark of the State in whose territory is other than that prescribed by the Convention on Road Traffic, Vienna, 1968, that other sign may continue to appear on certificates of IMO portable tanks manufactured before 1 January 2003. 3.8 Inspection and testing The requirements of 6.7.2.19.1 of chapter 6.7 concerning impact testing shall not apply to IMO portable tanks. Note: IMO portable tanks may be required to undergo a prototype impact test in order to comply with other standards, national or international requirements. This exemption does not take the place of those other standards, national or international requirements. 3.9 Marking of plates The particulars to be marked on the corrosion-resistant metal plate for IMO portable tanks shall correspond to that shown below instead of that shown at 6.7.2.20.1 of chapter 6.7: Country of manufacture... IMO tank Approval Approval Type no... country... number... Manufacturer's name or mark... Registration number... Year of manufacture... Test pressure... (bar)/(mpa)* Maximum allowable working pressure... (bar)/(mpa)*
Page 8 Water capacity at 20 C... (litres) (The water capacity should be established to within 1% by practical test rather than by calculation.) Maximum gross mass... (kg) Original hydrostatic test date and witness identification... Code to which tank is designed... Metallurgic design temperature (only if above +50 C or below -20 C)... Maximum allowable working pressure for coils (where coils used)... (bar)/(mpa)* Tank material... Equivalent thickness in mild steel... (mm) Lining material (if any)... Capacity of each compartment (in compartmented tanks)...litres Month, year and test pressure of most recent periodic test:... month... year... (bar)/(mpa)* Stamp of expert who carried out most recent test... * The unit used should be marked. 3.10 [The plate should be kept free of paint to ensure that the markings will be legible at all times.] 3.11 Additional requirements applicable to the transport of class 3 substances in IMO portable tanks IMO portable tanks should be closed and be fitted with relief devices in accordance with 6.7.2.8 to 6.7.2.15 of chapter 6.7 as varied by 3.5 and 3.6 of this guidance. 3.12 Special requirements relating to IMO portable tanks for the transport of solid dangerous substances (e.g. powdery or granulated materials) 3.12.1 Certain solid dangerous substances are permitted in portable tanks. Such portable tanks should be at least an IMO type 2 or type 4 tank as described in the Note to 4.2.0 unless indicated in chapter 3.2 - the Dangerous Goods List.
Page 9 3.12.2 Tanks used for the transport of solid dangerous substances (such as powdery or granulated substances) should comply with 6.9 except that instead of provisions of 6.7 they should comply at least with the provisions of 3.0 in so far as they relate to IMO type 2 and type 4 tanks. However, the required service equipment may be in accordance with 6.9.3.2 and 6.9.3.3. 3.12.3 Special provisions for tanks dedicated to the transport of solid substances which do not liquefy during transport are in 6.9.3. 3.13 Portable tank transitional arrangements The portable tank special provisions of 4.2.4.3, chapter 4.2 shall be applied to the use of IMO portable tanks taking into account any relevant transitional periods mentioned above in.1.2 of this guidance. 4.0 General requirements for IMO type 5 portable tanks for non-refrigerated liquefied gases of class 2. The provisions of 6.7.3 and 6.8.3.2 apply to IMO type 5 portable tanks and IMO type 6 tanks as appropriate except that the provisions in the sections below may be substituted for certain provisions identified in the sub-section. 4.1 Capacity of IMO portable tanks for non-refrigerated liquefied gases of class 2 The requirements of this subsection do not apply to rail wagons, non-metallic tanks or tanks having a capacity of less than 1000 litres. 4.2 Definitions The definitions of the terms below shall apply to IMO type 5 tanks instead of those in 6.7.3.1: 4.2.1 Maximum allowable working pressure (MAWP) means the maximum gauge pressure permissible at the top of the tank in its operating position. It may be no less than the vapour pressure at the design reference temperature less one bar of any product which can be loaded and carried, and any pressure which might be used during loading or unloading. In no case should the MAWP be less than 7 bar. 4.2.2 Test pressure means the maximum gauge pressure at the top of a tank during a hydraulic test. 4.2.3 Design reference temperature means the temperature at which the vapour pressure of the tank contents is determined for the purpose of calculating the MAWP. The design reference temperature should be less than the critical temperature of the gas to be transported to ensure that the gas at all times is liquefied.
Page 10 For type 5 tanks the temperature to be taken is as follows:.1 for a tank with a diameter of 1.5 metres or less: 65 C;.2 for a tank with a diameter of more than 1.5 metres:.2.1 without insulation or sun shield: 60 C;.2.2 with sun shield: 55 C; and.2.3 with insulation: 50 C.* * This reference temperature is envisaged but dependent on the quality of the insulation system. 4.2.4 Mild steel means a steel with a guaranteed minimum tensile strength of 360 N/mm2 and a guaranteed minimum percentage elongation of 27. 4.3 General requirements for the design, construction and operation of tanks for nonrefrigerated gases The following requirements shall apply to the design of IMO type 5 tanks for nonrefrigerated gases. The following requirements in 6.7.3.2.1 of chapter 6.7 shall be replaced by the following: 4.3.1 Shells should be made of steel suitable for shaping. For welded shells only a material whose weldability has been fully demonstrated should be used. If the manufactureprocedure or the materials make it necessary, the tanks should be heat-treated with a suitable heat treatment both after welding operations and after forming. Welds should be skilfully made and afford complete safety. Tank materials should be suitable for the external environment in which they may be carried, e.g. the marine environment. The use of aluminium as a material of construction should be specifically authorised for use in the marine mode in the appendix. In those cases where aluminium is authorised, it should be insulated to prevent significant loss of physical properties when it is subjected to a heat load of 2.60gcal/cm2.s for a period of 30 minutes. The insulation system should remain effective at all temperatures of up to 650 C and should be jacketed with a material with a melting point of not less than 650 C. The insulation system should be approved by the competent authority. Steel should be resistant to brittle fracture and to fissuring corrosion under stress. For type 5 tanks the temperature range to be taken into account should be between -30 C and the design reference temperature unless more stringent conditions are specified by the competent authority. For road tank vehicles the temperature range is to be agreed by the competent authorities. 4.3.2 In 6.7.3.2.1, the provision for fine grain steels when used to construct portable tanks, to have a guaranteed yield strength maximum of 460 N/mm2 and tensile strength limit of 725 N/mm2 is not required. [However, in so far as it is possible, these values should be taken into account in selecting materials for the repair of IMO portable tanks]. 4.3.3 The following requirements shall apply in place of the requirements at 6.7.3.2.9 of chapter 6.7:The minimum dynamic loads to be withstood should be based on:
Page 11.1 in the direction of travel: twice the total mass;.2 horizontally at right angles to the direction of travel: the total mass where the direction of travel is not clearly determined, the maximum permissible load should be equal to twice the total mass);.3 vertically upwards: the total mass; and.4 vertically downwards: twice the total mass (total loading, including the effect of gravity). The said loads should be considered separately. 4.3.4 Where an IMO type 5 tank is fully insulated, the thermal conductance is required in 6.7.3.2.12.2, chapter 6.7 to be not more than 0.67 Wm -2 K -1 is not required. [However, it should be taken into account during their use.] 4.3.5 IMO type 5 tanks intended to contain certain gases, should be provided with additional protection. These gases are indicated below:.1 The calculated wall thickness for UN 1017 CHLORINE and UN 1079 SULPHUR DIOXIDE should be increased by 3mm, to be verified ultrasonically at intervals midway between the periodic hydraulic test..2 The wall thickness for UN 1067 DINITROGEN TETRAOXIDE and UN 3057 TRIFLUOROACETYL CHLORIDE should be not less than 8mm. The tanks should be hydraulically tested and internally inspected at intervals not exceeding 2.5 years. 4.4 Cross-sectional design 4.4.1 The ratio of the test pressure to the maximum allowable working pressure (MAWP) for IMO Type 5 tanks is 1.3. Minimum requirements for the MAWP of IMO type 5 tanks were specified in the IMDG Code Amendment 29-98 and earlier amendments. These are similar to those laid down in T50 of chapter 4.2. However, the following variations may continue to be applied to IMO type 5 tanks: UN 1021 1-CHLORO-1,2,2,2-TETRACHLOROETHANE Bare tanks: 8.9 bar. UN 1582 CHLOROPICRIN AND METHYL CHLORIDE MIXTURE: Small tanks: 15.2 bar Bare tanks: 13.0 bar Sun shield tanks: 11.6 bar Insulated tanks: 10.1 bar UN 1974 CHLOROFLUOROBROMOMETHANE (R12B1) Small tanks: 7.3 bar
Page 12 4.4.2 The following requirements may be used in place of paragraph 6.7.3.2.9 of chapter 6.7: At the test pressure the primary membrane stress in the shell should conform to the material-dependent limitations prescribed below:.1 for metals and alloys exhibiting a clearly defined yield point or characterised by a guaranteed conventional yield stress Re (generally 0.2% residual elongation; for austenitic steels, 1% residual elongation), the stress should not exceed 0.75 Re or 0.50 Rm, whichever is lower;.2 the elongation at fracture of steel, in per cent, should not be less than 10,000, with an absolute minimum of 20%; the elongation at fracture of aluminium, in per cent, should not be less than 10,000, with an absolute minimum of 12%;.3 Rm is the guaranteed minimum tensile strength, given in N/mm 2 ; and.4 when fine-grain steel is used for road tank vehicles, the minimum elongation at fracture of material used is to be agreed between the competent authorities but should not be less than 16%. It should be noted that the specimens used to determine the elongation at fracture should be taken transversely to the direction of rolling and be so secured that: where: L o = 5d, or L o =5.65 A L o = gauge length of the specimen before the test; d = diameter; and A = cross-sectional area of the test specimen. [4.4.3 Materials with an Re/Rm ratio greater than 0.85 are not allowed for the construction of welded UN portable tanks (see 6.7.3.3.3.2, chapter 6.7). IMDG Code Amendment 29 98 did not require these provisions. Nevertheless these requirements should be taken into account as far as practicable for IMO type 5 tanks including the requirements of 6.7.3.3.3.4 of chapter 6.7 regarding the determination of these values.] 4.5 Minimum shell thickness Instead of the requirements at 6.7.3.4.4 of chapter 6.7 the following requirements shall apply to the determination of minimum shell thickness.
Page 13 4.5.1 The cylindrical portions and ends of tanks should have a thickness of not less than that determined by the following formula *: where: e = C. 3 (Rm x A) e = minimum required thickness of the metal to be used, in mm; Rm = guaranteed minimum tensile strength of the metal to be used, in N/mm2; A = guaranteed minimum elongation (as a percentage) of the metal to be used on fracture under tensile stress; see 3.1.3.2 of this Annex; C = 107 (equivalent to 5 mm mild steel) for tanks of not more than 1.80 m in diameter; and C = 128 (equivalent to 6 mm mild steel) for tanks of more than 1.80 m in diameter. *The constant C is derived from the following formula: e 3 (Rm x A) = e o 3 (Rm o x A o ), where the sub-index `o' refers to mild steel and the part of the equation without sub-index `o' refers to the metal used. The relationship with mild steel as employed by this Code is attached to the constant C, where C = e o 3 (Rm o x A o ). 4.6 Capacity of relief devices 4.6.1 The requirements of 6.7.3.8 of chapter 6.7 shall apply to the determination of the total capacity of relief devices with the exception that the pressure (including accumulation) inside IMO type 5 tanks should not exceed 110% of the MAWP; and 4.6.2 The melting point of insulation jackets used for the purpose of reducing the venting capacity may be taken as 649 o C in place of 700 o C. 4.7 Marking of pressure-relief devices 4.7.1 The requirements of 6.7.3.9 of chapter 6.7 shall apply to IMO type 5 tanks with the following exceptions:.1 that where the rated flow capacity has been determined in some other way than is prescribed in ISO 4126-1:1996, the alternative standard used where practicable shall be marked on the device and;.2 the capacity should be marked on devices at a pressure not greater than 110% of the set pressure.
Page 14 4.8.1 Inspection and testing 4.8.1 The requirements of 6.7.3.15.1 of chapter 6.7 concerning impact testing shall not apply to IMO type 5 tanks. Note: IMO type 5 tanks may be required to undergo a prototype impact test in order to comply with other standards, national or international requirements. This exemption does not take the place of those other standards, national or international requirements. 4.9 Marking The particulars to be marked on the corrosion-resistant metal plate for IMO type 5 tanks shall correspond to that shown below instead of that shown at 6.7.3.16.1 of chapter 6.7: Every tank should be fitted with a corrosion-resistant metal plate permanently attached in a place readily accessible for inspection. At least the following particulars should be marked on the plate in characters at least 3 mm in height by stamping, engraving, embossing or any similar method. If, for reasons of tank arrangements, the plate cannot be permanently attached to the shell, the shell shall be marked with at least those particulars required by a recognised pressure vessel code in a manner prescribed by that code. [4.9.2 The plate should be kept free of any paint to ensure that the markings will be legible at all times.] Country of manufacture... IMO tank Approval Approval type no... country.. number.. Manufacturer s name or mark... Registration number... Year of manufacture... Test pressure.... (bar)/(mpa) gauge* Maximum allowable working pressure... (bar)/(mpa) gauge* Water capacity at 20 C... (litres) (The water capacity should be established to within 1% by practical test rather than by calculation.) Original hydrostatic test date and witness identification... Code to which tank is designed...
Page 15 Design reference temperature... ( C) Metallurgic design temperature (only if below 30 C)..... Tank material... Equivalent thickness in mild steel... (mm) Month, year and test pressure of most recent periodic test:... month... year... (bar)/(mpa) gauge* *The unit used should be marked. The following particulars should be marked either on the tank itself or on a metal plate firmly secured to the tank. Names of owner and operator... Name of gas being carried (and maximum mean bulk temperature if other than 50 C)... Date of the last inspection... Maximum permissible gross mass... (kg) Unladen (tare) mass... (kg) 4.10 Portable tank special provisions The portable tank special provisions of 4.2.4.3, chapter 4.2 be applied to the use of IMO type 5 tanks taking into account any relevant transitional periods mentioned above in 1.2 of this guidance. 5.0 General requirements for IMO type 7 portable tanks for deeply refrigerated liquefied gases of class 2. The provisions of 6.7.4 and 6.8.3.3 apply to IMO type portable tanks and IMO tanks as appropriate except that the provisions in the sections below may be substituted for the indicated provisions of 6.7.4. 5.1 Capacity of IMO portable tanks for non-refrigerated liquefied gases of class 2 The requirements subsection do not apply to rail tanks wagons, non-metallic tanks or tanks having a capacity of 1000 litres or less. 5.2 Approval of Existing Tanks Existing tanks and their service equipment not conforming strictly to the requirements of Amendment 29 98 and earlier Amendments, but having acceptable alternatives, could
Page 16 be considered by the competent authority for approval. The certificates of these tanks were required to have the entry Approved in accordance with 13.201.3 of the IMDG Code. IMO type 7 tanks with this endorsement on their certificates may continue in service. 5.3 Definitions The following definitions of the terms below shall apply to IMO type 7 tanks instead of those in 6.7.4.1: 5.3.1 Holding time means the time that will elapse from the moment the liquid starts boiling at atmospheric pressure up to the moment the pressure of the tank contents reaches the MAWP under equilibrium conditions. 5.3.2 Tank means a construction which normally consists of:.1 a jacket and one or more inner shells where the space between the shell or shells and the jacket incorporates thermal insulation and is exhausted of air (vacuum insulation); or.2 a jacket and an inner shell with an intermediate layer of solid thermally insulating material (e.g. solid foam); or.3 an outer shell with an inner layer of solid thermally insulating material. 5.4 General requirements for the design, construction and operation of tanks for refrigerated liquefied gases The following requirements shall apply to the design of IMO type 7 tanks for deeply refrigerated liquefied gases. [5.4.1 In 6.7.4.2.1, the provision for fine grain steels for portable tanks, to have a guaranteed yield strength maximum of 460 N/mm2 and tensile strength limit of 725 N/mm2 is not required for IMO type tanks. [However this provision should be taken into account in selecting materials for the repair of IMO portable tanks.] 5.4.2 Instead of the procedure to determine a reference holding time required in 6.7.4.2.8, chapter 6.7, the following requirement for determining a holding time shall apply to IMO type 7 tanks: A holding time should be calculated at the design stage and take into account:.1 effectiveness of the insulation system provided;.2 MAWP;.3 degree of filling;.4 assumed ambient temperature of 50 C;.5 physical properties of the individual substance to be transported.
Page 17 5.4.3 The requirements of 6.7.4.2.8.2 of chapter 6.7 need not be applied to IMO type 7 tanks. 5.4.4 The following requirements shall apply in place of the requirements at 6.7.4.2.12 of chapter 6.7: IMO type 7 tanks and their fastenings should be capable of withstanding separately applied forces based on:.1 twice the total mass acting in the direction of travel of the tank simultaneous with the weight of the tank;.2 the total mass acting horizontally at right angles to the direction of travel of the tank (where the direction of travel is not clearly determined, the total mass should be used) simultaneous with the weight of the tank;.3 the total mass acting vertically upwards;.4 twice the total mass acting vertically downwards. Under each of these loads, for type 7 tanks, the safety factors to be observed should be:.1 for metals having a clearly defined yield point, a safety factor of 1.5 in relation to the determined yield stress; or.2 for metals with no clearly defined yield point, a safety factor of 1.5 in relation to the guaranteed 0.2% proof stress (1.0% proof stress for austenitic steels). 5.4.5 The following requirements may be used instead of paragraph 6.7.4.3.3 of chapter 6.7: At the test pressure, the primary membrane stress in the shell should conform to the material-dependent limitations prescribed below:.1 for metals and alloys exhibiting a clearly defined yield point or characterised by a guaranteed conventional yield stress Re (generally 0.2% proof stress; for austenitic steels 1.0% proof stress), the membrane stress should not exceed 0.75 Re or 0.50 Rm, whichever is lower, where Rm in N/mm 2 is the guaranteed minimum tensile strength;.2 in the case of steel, the elongation at fracture, in per cent, should not be less than 10,000, where Rm is in N/mm 2, with an Rm absolute minimum of 17%. In the case of aluminium, the elongation at fracture, in per cent, should not be less than 10,000, where Rm is in N/mm 2, with an absolute minimum of 12%. The specimens used to determine the elongation at fracture should be taken transversely to the direction of rolling and be so secured that: L o = 5d, or
Page 18 L o =5.65 A where: L o = gauge length of the specimen before the test; d = diameter; and A = cross-sectional area of the test specimen. [5.4.6 In 6.7.4.3.3.2, chapter 6.7materials, with an Re/Rm ratio greater than 0.85 are not allowed for the construction of welded UN portable tanks. These provisions are not required for IMO type 7 tanks. Nevertheless these requirements should be taken into account as far as practicable for IMO type 7 tanks including the requirements of 6.7.4.3.3.4 of chapter 6.7 regarding the determination of these values.] 5.4.7 In no case should the test pressure of IMO type 7 tanks be less than 300 kpa (3 bar) gauge pressure. 5.5 Minimum shell thickness In place of the requirements at 6.7.4.4.6 of chapter 6.7 the following requirements IMDG Code Amendment 29 apply to the determination of minimum shell thickness. 5.5.1 The shells of IMO type 7 tanks should have a thickness of not less than that determined by the following formula *: e = C. 3 (Rm x A) where: e = minimum required thickness of the metal to be used, in mm; Rm = guaranteed minimum tensile strength of the metal to be used, in N/mm 2 ; A = guaranteed minimum elongation (as a percentage) of the metal to be used on fracture under tensile stress; see 6.7.4.3.3; C = 107 (equivalent to 5 mm mild steel) for tanks of not more than 1.80 m in diameter C = 128 (equivalent to 6 mm mild steel) for tanks of more than 1.80 m in diameter. C = 64 for shells of vacuum-insulated tanks (equivalent to 5 mm mild steel) for tanks of not more than 1.80 m in diameter C = 85 for shells of vacuum-insulated tanks (equivalent to 6 mm mild steel) for tanks of more than 1.80 m in diameter. *The constant C is derived from the following formula: e 3 (Rm x A) = e o 3 (Rm o x A o ), where the sub-index `o refers to mild steel and the part of the equation without sub-index
Page 19 `o refers to the metal used. The relationship with mild steel as employed by this Code is attached to the constant C, where C = e o 3 (Rm o x A o ). 5.6 Capacity of relief devices The requirements of 6.7.4.7 of chapter 6.7 shall apply to the determination of the total capacity of relief of IMO type 7 tanks except that the combined capacity of all relief devices should be sufficient to limit the pressure to 110% of the MAWP. 5.7 Marking of pressure-relief devices The requirements of 6.7.4.8 of chapter 6.7shall apply to IMO type 7 tanks with the following exceptions:.1 that where the rated flow capacity has been determined in some other way than is prescribed in ISO 4126-1:1996, the alternative used, where practicable, shall be marked on the device and;.2 the capacity should be marked on devices at a pressure not greater than 110% of the set pressure. 5.8 Inspection and testing The requirements of 6.7.4.14.1 of chapter 6.7 concerning impact testing shall not apply to IMO type 7 tanks. Note: IMO type 7 tanks may be required to undergo a prototype impact test in order to comply with other standards, national or international requirements. This exemption does not take the place of those other standards, national or international requirements. 5.8 Marking The particulars to be marked on the corrosion-resistant metal plate for IMO type 7 tanks shall correspond to that shown below instead of that shown at 6.7.4.15.1 of chapter 6.7: 5.8.1 Every tank should be fitted with a corrosion-resistant metal plate permanently attached in a place readily accessible for inspection. At least the following particulars should be marked on the plate in characters at least 3 mm in height by stamping, engraving, embossing or any similar method. 5.8.2 If, for reasons of tank arrangements, the plate cannot be permanently attached to the shell, the shell should be marked with at least those particulars required by a recognised pressure vessel code in a manner prescribed by that code. [5.8.3 The plate should be kept free of any paint to ensure that the markings will be legible at all times.]
Page 20 Country of manufacture... IMO tank Approval Approval type no.. country. number. Manufacturer s name or mark... Registration number... Year of manufacture... Test pressure..... (bar)/(mpa) gauge* Maximum allowable working pressure (bar)/(mpa) gauge* Water capacity at 20 C of each compartment....(litres) (The water capacity should be established to within 1% by practical test rather than by calculation.) Original pressure test date and witness identification... Code to which the shell is designed... Minimum design temperature... ( C) Maximum total mass... (kg) Unladen (tare) mass... (kg) Shell material.... Month, year and test pressure of most recent periodic test:... month... year... (bar)/(mpa)* gauge Stamp of expert who carried out most recent test... The names, in full, of the gases for whose transport the tank is approved...... Either thermally insulated or vacuum-insulated... *The unit used should be indicated. The following particulars should be durably marked either on the tank itself or on a metal plate firmly secured to the portable tank. Name of owner and operator....
Page 21 Name of gas being transported (and minimum mean bulk temperature)... Date of the last inspection... Total mass... (kg) Holding time... (days) 5.9 Portable tank special provisions The portable tank special provisions of 4.2.4.3, chapter 4.shall be applied to the use of IMO portable tanks taking into account any relevant transitional periods mentioned above in 1.2 of this guidance.