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The UN Sub-committee of Experts on the Transport of Dangerous Goods (TDG) held its 56th session this past 4 to 10 December with Duane Pfund (US) as chair and Claude Pfauvadel (France) sitting as vice-chair. The session was attended by experts from 18 countries and representatives from the EU, the Intergovernmental Organisation for International Carriage by Rail (OTIF), the International Civil Aviation Organisation (ICAO), the International Maritime Organisation (IMO), the Food and Agriculture Organisation (FAO), the World Health Organisation (WHO) and 20 non-governmental organisations.

The session was the second of four planned for the current regulatory biennium, which will result in the adoption this coming December by the parent Committee of the changes that will appear in the 22nd revised edition of the UN Recommendations on the Transport of Dangerous Goods (alternatively known as the UN Model Regulations or the ‘Orange Book’).

The first part of this three-part report on the December meeting in last month’s issue (HCB April 2020, page 50) covered discussions on the transport of explosives, classification and packaging, and electric storage systems. This second part focuses on some significant changes involving the transport of gases.

STANDARDS UPDATE

The International Standardisation Organisation (ISO) arrived with its usual proposals to update the standards referenced in Part 6 relating to gas cylinders, which were agreed with some textual amendments.

In 6.2.2.1.2, references to “UN tubes” and “composite tubes” will be replaced by “UN tube shells” and “composite tube shells”, respectively. The existing entry in the table for UN 11515:2013 will now expire on 31 December 20206 and a new row is added referencing the 2018 amendment. This introduces the gun fire test and revises the blunt impact test.

In 6.2.2.1.8, the entry in the table for ISO 21172-1:2015 will now expire on 31 December 2026 and a new row is added referencing the 2018 amendment, which removes the restriction on the carriage of corrosive gases in drums with dished ends.

In 6.2.2.4, the first sentence is amended to read:

The following standards apply to periodic inspection and testing of UN pressure receptacles:

In the first table, the existing entries for ISO 6406:2005 and ISO 10461:2005/A1:2006 will now expire on 31 December 2024. A new row is added for ISO 18119:2018. As a consequential amendment, Note 3 to 6.2.1.6.1 is amended to read:

The check of internal conditions of 6.2.1.6.1 (b) and the hydraulic pressure test of 6.2.1.6.1 (d) may be replaced by ultrasonic examination carried out in accordance with ISO 18119:2018 for seamless steel and seamless aluminium alloy cylinder shells. For a transitional period until 31 December 2024 the standard ISO 10461:2005 +A1:2006 may be used for seamless aluminium alloy cylinders and ISO 6406:2005 may be used for seamless steel cylinder shells for this same purpose.

In addition, the existing entry for ISO 10460:2005 will now expire on 31 December 2024 and a new row is added for ISO 10460:2018. This now provides provisions for stainless steel and aluminium alloy welded cylinders, in addition to carbon steel. The row for ISO 11623:2002 is deleted as it is not applicable after the end of 2020.

PRESSURE RECEPTACLES

A joint paper from the European Industrial Gases Association (EIGA), the Compressed Gases Association (CGA) and the European Cylinder Makers Association (ECMA) followed up on discussion at the previous session with a very long list of revised proposals to amend the provisions for pressure receptacles and their closures. They included a number of changes in the definitions in 1.2.1:

In the definition of “Bundle of cylinders”, “an assembly of cylinders” is replaced by “a pressure receptacle comprising an assembly of cylinders or cylinder shells”
A new Note is added under the definition of “Closure”:

For pressure receptacles, closures are, for example, valves, pressure relief devices, pressure gauges or level indicators.

The definition of “Cryogenic receptacle” is amended to read:

Closed cryogenic receptacle means a transportable thermally insulated pressure receptacle for refrigerated liquefied gases of a water capacity of not more than 1 000 litres;

In the definitions of “Cylinder”, “Pressure drum” and “Tube” the word “transportable” is deleted
In the definition of “Metal hydride storage system”, “receptacle” is replaced by “pressure receptacle shell”
In the definition of “Pressure receptacle”, after “Pressure receptacle” are added the words “means a transportable receptacle intended for holding substances under pressure including its closure(s) and other service equipment and”
The definition of “Working pressure” is amended to read:

(a) For a compressed gas means the settled pressure at a reference temperature of 15˚C in a full pressure receptacle;

(b) For UN 1001 acetylene, dissolved means the calculated settled pressure at a uniform reference temperature of 15 °C in an acetylene cylinder containing the specified solvent content and the maximum acetylene content;

(c) For UN 3374 acetylene, solvent free the working pressure corresponds to the working pressure which was calculated for the equivalent cylinder for UN 1001 acetylene, dissolved.

There are also three new definitions to be added:

Inner vessel, for a closed cryogenic receptacle, means the pressure vessel intended to contain the refrigerated liquefied gas;

Pressure receptacle shell means a cylinder, a tube a pressure drum or a salvage pressure receptacle without its closures or other service equipment, but including any permanently attached device(s) (e.g. neck ring, foot ring, etc.);

NOTE: The terms “cylinder shell”, “pressure drum shell” and “tube shell” are also used.

Service equipment of a pressure receptacle means closure(s), manifold(s), piping, porous, absorbent or adsorbent material and any structural devices, e.g. for handling;

In 4.1.6.1.6, the first sentence is extended with the addition at the end of “and taking into account the lowest pressure rating of any component”. A new second sentence is added:

Service equipment having a pressure rating lower than other components shall nevertheless comply with 6.2.1.3.1.

The final sentence of 4.1.6.1.6 is deleted.

In the first sentence of 4.1.6.1.10, “closed” is inserted before “cryogenic receptacle” and “P205 or P206” is replaced by “P205, P206 or P208”.

In 5.2.1.7.1, third indent, and 5.2.1.6.2(a), “cryogenic receptacles” is replaced by “closed and open cryogenic receptacles”.

In 6.2.1.1.1, after “Pressure receptacles”, “and their closures” is deleted. At the end of that sentence, “transport” is replaced by “transport and intended use”.

In 6.2.1.1.4, at the end of the sentence, “used” is replaced by “welded”.

In 6.2.1.1.5, first sentence, “cylinders, tubes, pressure drums” is replaced by “pressure receptacle shells”. In the final sentence, “shell” is inserted after “The test pressure of a cylinder”.

In 6.2.1.1.6, at the beginning of the first and second sentences and in the final sentence, “Pressure receptacles” is replaced by “Cylinders or cylinder shells”.

In 6.2.1.8.2, in the third and fourth sentences, “pressure receptacle” is replaced by “inner vessel”. At the end of the fourth sentence, “fittings” is replaced by “service equipment”.

In 6.2.1.1.9, at the end of the heading, “pressure receptacles for acetylene” is replaced by “acetylene cylinders”. In the first sentence, “Pressure receptacles” is replaced by “Cylinder shells”, with a similar change in sub-paragraph (a). In the final sentence, “compatible with the pressure receptacle” is replaced by “compatible with those parts of the cylinder that are in contact with it”.

In 6.2.1.2.1 and 6.2.1.2.2 “and their closures” is deleted after “pressure receptacles”.

In 6.2.1.3.1, “Valves, piping and other fittings” is replaced by “Service equipment”. “excluding pressure relief devices” is replaced by “excluding porous, absorbent or adsorbent material, pressure relief devices, pressure gauges or indicators”.

6.2.1.3.2 is amended to read:

Service equipment shall be configured or designed to prevent damage and unintended opening that could result in the release of the pressure receptacle contents during normal conditions of handling and transport. All closures shall be protected in the same manner as is required for valves in 4.1.6.1.8. Manifold piping leading to shut-off valves shall be sufficiently flexible to protect the shut-off valves and the piping from shearing or releasing the pressure receptacle contents.

In 6.2.1.3.3, “shall be fitted with devices” is amended to read “shall be fitted with handling devices”.

In 6.2.1.4.1, the second sentence beginning “Pressure receptacles…” is deleted.

A new 6.2.1.4.3 is inserted:

Pressure receptacle shells and the inner vessels of closed cryogenic receptacles shall be inspected tested and approved by an inspection body.

A new 6.2.1.4.4 is inserted:

For refillable cylinders, pressure drums and tubes the conformity assessment of the shell and the closure(s) may be carried out separately. In these cases, an additional assessment of the final assembly is not required.

For bundles of cylinders, the cylinder shells and the valve(s) may be assessed separately, but an additional assessment of the complete assembly is required.

For closed cryogenic receptacles, the inner vessels and the closures may be assessed separately, but an additional assessment of the complete assembly is required.

For acetylene cylinders, conformity assessment shall comprise either:

(a) one assessment of conformity covering both the cylinder shell and the contained porous material; or

(b) a separate assessment of conformity for the empty cylinder shell and an additional assessment of conformity covering the cylinder shell with the contained porous material.

There are several changes in 6.2.1.5.1, including the addition of “and bundles of cylinders” after “closed cryogenic receptacles, metal hydride storage systems” and the addition of “or recognised technical codes” after “the applicable design standards”. Further, the following new provisions are added after (j):

On an adequate sample of closures:

(k) Verification of materials;

(l) Verification of dimensions;

(m) Verification of cleanliness;

(n) Inspection of completed assembly;

(o) Verification of the presence of marks.

For all closures:

(p) Testing for leakproofness.

6.2.1.5.2 has been completely amended and will read:

Closed cryogenic receptacles shall be subjected to testing and inspection during and after manufacture in accordance with the applicable design standards or recognized technical codes including the following:

On an adequate sample of inner vessels:

(a) Testing of the mechanical characteristics of the material of construction;

(b) Verification of the minimum wall thickness;

(c) Inspection of the external and internal conditions;

(d) Verification of the conformance with the design standard or code;

(e) Inspection of welds by radiographic, ultrasonic or other suitable non-destructive test method according to the applicable design and construction standard or code.

For all inner vessels:

(f) A hydraulic pressure test. The inner vessel shall meet the acceptance criteria specified in the design and construction technical standard or technical code;

NOTE: With the agreement of the competent authority, the hydraulic pressure test may be replaced by a test using a gas, where such an operation does not entail any danger.

(g) Inspection and assessment of manufacturing defects and either repairing them or rendering the inner vessel unserviceable;

(h) An inspection of the marks.

On an adequate sample of closures:

(i) Verification of materials;

(j) Verification of dimensions;

(k) Verification of cleanliness;

(l) Inspection of completed assembly;

(m) Verification of the presence of marks.

For all closures:

(n) Testing for leakproofness.

On an adequate sample of completed closed cryogenic receptacles:

(o) Testing the satisfactory operation of service equipment;

(p) Verification of the conformance with the design standard or code.

For all completed closed cryogenic pressure receptacles:

(q) Testing for leakproofness.

In 6.2.1.5.3, in the first sentence “receptacles” is replaced by “pressure receptacle shells”.

A new 6.2.1.5.4 is added:

For bundles of cylinders the cylinder shells and closures shall be subjected to initial inspection and tests specified in 6.2.1.5.1. An adequate sample of frames shall be proof load tested to two times the maximum gross weight of the bundles of cylinders.

Additionally, all manifolds of bundle of cylinders shall undergo a hydraulic pressure test and all the completed bundles of cylinders shall undergo a leakproofness test.

NOTE: With the agreement of the competent authority, the hydraulic pressure test may be replaced by a test using a gas, where such an operation does not entail any danger.

In 6.2.1.6.1, the text of (c) and (d) is amended to read:

(c) Checking of the threads either:

(i) if there is evidence of corrosion; or

(ii) if the closures or other service equipment are removed;

(d) A hydraulic pressure test of the pressure receptacle shell and, if necessary, verification of the characteristics of the material by suitable tests;

In note 2, “pressure test of cylinders or tubes” is replaced by “pressure test of cylinder shells or tube shells”. Note 3 is amended to read:

A new Note 4 is inserted:

For bundles of cylinders the hydraulic test specified in (d) above shall be carried out on the cylinder shells and on the manifold.

Sub-paragraph (e) is amended and a new (f) is added:

(e) Check of service equipment, if to be reintroduced into service. This check may be carried out separately from the inspection of the pressure receptacle shell;

(f) A leakproofness test of bundles of cylinders after reassembly.

In 6.2.1.6.2, “Pressure receptacles” is replaced by “Cylinders”.

6.2.1.7.2 is amended to read:

A proficiency test of the manufacturers of pressure receptacle shells and the inner vessels of closed cryogenic receptacle shall in all instances be carried out by an inspection body approved by the competent authority of the country of approval. Proficiency testing of manufacturers of closures shall be carried out if the competent authority requires it. This test shall be carried out either during design type approval or during production inspection and certification.

In 6.2.2, note 2, “and service equipment” is deleted after “UN pressure receptacles”.

In 6.2.2.1.1, first sentence, “UN cylinders” is replaced by “refillable UN cylinder shells”. In the table, the rows for ISO 11118:1999 and ISO 11118:2015 are deleted. In the notes, “composite cylinders” is replaced by “composite cylinder shells”.

In 6.2.2.1.4, “UN cryogenic receptacles” is replaced by “UN closed cryogenic receptacles”.

In 6.2.2.1.6, second sentence, “UN cylinder” is replaced by “UN cylinder or UN cylinder shell”. The current note is amended to read:

Changing one or more cylinders or cylinder shells of the same design type, including the same test pressure, in an existing UN bundle of cylinders does not require a new conformity assessment of the existing bundle. Service equipment of the bundle of cylinders can also be replaced without requiring a new conformity assessment if it complies with the design type approval.

A new 6.2.2.1.9 is inserted:

The following standards apply to the design, construction and initial inspection and test of non-refillable UN cylinders except that the inspection requirements related to the conformity assessment system and approval shall be in accordance with 6.2.2.5.

The table attached references ISO 11118:1999, ISO 13340:2001 and ISO 11118:2015.

In 6.2.2.2, first sentence, “pressure receptacle” is deleted.

In the title of 6.2.2.3, “Service equipment” is replaced by “Closures and their protection”. The first sentence will now read:

The following standards apply to the design, construction, and initial inspection and test of closures and their protection:

In the first table, the row for ISO 13340:2001 is deleted.

In 6.2.2.4, the first sentence is amended to read:

The following standards apply to periodic inspection and testing of UN pressure receptacles:

In 6.2.2.5, 6.2.2.5.1 is renumbered 6.2.2.5.0 and a new Note is added at the end:

In this subsection when separate assessment is used the term pressure receptacle shall refer to pressure receptacle, pressure receptacle shell, inner vessel of the closed cryogenic receptacle or closure, as appropriate.

A new 6.2.2.5.1 is added:

The requirements of 6.2.2.5 shall be used for the conformity assessments of pressure receptacles. Paragraph 6.2.1.4.3 gives details of which parts of pressure receptacles may be conformity assessed separately. However, the requirements of 6.2.2.5 may be replaced by requirements specified by the competent authority in the following cases:

(a) conformity assessment of closures;

(b) conformity assessment of the complete assembly of bundles of cylinders provided the cylinder shells have been conformity assessed in accordance with the requirements of 6.2.2.5; and

(c) conformity assessment of the complete assembly of closed cryogenic receptacles provided the inner vessel has been conformity assessed in accordance with the requirements of 6.2.2.5.

The text of 6.2.2.5.4.9(c) is replaced by:

As required by the pressure receptacle standard or technical code, carry out or supervise the tests of pressure receptacles as required for design type approval.

A new sentence is added at the end of the penultimate paragraph of 6.2.2.5.4.9:

If it was not possible to evaluate exhaustively the compatibility of the materials of construction with the contents of the pressure receptacle when the certificate was issued, a statement that compatibility assessment was not completed shall be included in the design type approval certificate.

In 6.2.2.7, the Note is amended by adding “and marking requirements for closures are given in 6.2.2.11” after “6.2.2.9 and marking”.

A new note is added at the end of 6.2.2.7.2(b):

For acetylene cylinders the standard ISO 3807 shall also be marked.

A new note is added after 6.2.2.7.2(e):

When an acetylene cylinder is conformity assessed in accordance with 6.2.1.4.3 (b) and the inspection bodies for the cylinder shell and the acetylene cylinder are different, their respective marks (d) are required. Only the initial inspection date (e) of the completed acetylene cylinder is required. If the country of approval of the inspection body responsible for the initial inspection and test is different a second mark (c) shall be applied.

A new note is added at the end of 6.2.2.7.3(i):

When a cylinder shell is intended for use as an acetylene cylinder (including the porous material), the working pressure mark is not required until the acetylene cylinder is completed.

In 6.2.2.7.3, paragraphs (k) and (l) are replaced as follows:

(k) In the case of cylinders for UN 1001 acetylene, dissolved:

(i) the tare in kilograms consisting of the total of the mass of the empty cylinder shell, the service equipment (including porous material) not removed during filling, any coating, the solvent and the saturation gas expressed to three significant figures rounded down to the last digit followed by the letters "KG". At least one decimal shall be shown after the decimal point. For pressure receptacles of less than 1 kg, the mass shall be expressed to two significant figures rounded down to the last digit;

(ii) the identity of the porous material (e.g.: name and trademark); and

(iii) the total mass of the filled acetylene cylinder in kilograms followed by the letters “KG”;

(l) In the case of cylinders for UN 3374 acetylene, solvent free:

(i) the tare in kg consisting of the total of the mass of the empty cylinder shell, service equipment (including porous material) not removed during filling and any coating expressed to three significant figures rounded down to the last digit followed by the letters "KG". At least one decimal shall be shown after the decimal point. For pressure receptacles of less than 1 kg, the mass shall be expressed to two significant figures rounded down to the last digit;

(ii) the identity of the porous material; and

(iii) the total mass of the filled acetylene cylinder in kilograms followed by the letters “KG”;

A new note is added after 6.2.2.7.4(n):

If the manufacturer of the acetylene cylinder and the manufacturer of the cylinder shell are different, only the mark of the manufacturer of the completed acetylene cylinder is required.

In 6.2.2.8, “pressure receptacles” is replaced by “cylinders” several times.

In 6.2.2.10.1, “cylinders” is replaced by “cylinder shells” and a new second sentence is added:

Individual closures in a bundle of cylinders shall be marked in accordance with 6.2.2.11.

A new 6.2.2.11 is added:

Marking of closures for refillable UN pressure receptacles

For closures the following permanent marks shall be applied clearly and legibly, (e.g. stamped, engraved or etched):

(a) Manufacturer’s identification mark;

(b) Design standard or design standard designation;

(c) Date of manufacture (year and month or year and week) and

(d) The identity mark of the inspection body responsible for the initial inspection and test, if applicable.

The valve test pressure shall be marked when it is less than the test pressure which is indicated by the rating of the valve filling connection.

OTHER BUSINESS

An informal document from Germany sought to more closely define the conditions under which pressure relief devices for pressure receptacles should be triggered or must not yet be triggered, offering two suggested amendments. The Sub-committee noted that there are existing provisions at national and regional level on operating temperatures but encouraged delegations to send comments to Germany so that the issue could be pursued.

The third and final part of this report on the UN Sub-committee’s December 2019 session in next month’s HCB will cover the remaining discussions, which included further significant amendments to the UN Model Regulations.

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