17.16 Methyl acetylene-propadiene mixtures
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Statutory Documents - IMO Publications and Documents - Resolutions - Maritime Safety Committee - Resolution MSC.370(93) – Amendments to The International Code for The Construction and Equipment of Ships Carrying Liquefied Gases In Bulk (IGC Code) – (Adopted on 22 May 2014) - Annex - Amendments to The International Code for The Construction and Equipment of Ships Carrying Liquefied Gases In Bulk (IGC Code) - Chapter 17 — Special Requirements - 17.16 Methyl acetylene-propadiene mixtures

17.16 Methyl acetylene-propadiene mixtures

  17.16.1 Methyl acetylene-propadiene mixtures shall be suitably stabilized for transport. Additionally, upper limits of temperatures and pressure during the refrigeration shall be specified for the mixtures.

  17.16.2 Examples of acceptable stabilized compositions are:

  • .1 Composition 1:

    • .1 maximum methyl acetylene to propadiene molar ratio of 3 to 1;

    • .2 maximum combined concentration of methyl acetylene and propadiene of 65 mol%;

    • .3 minimum combined concentration of propane, butane, and isobutane of 24 mol%, of which at least one third (on a molar basis) shall be butanes and one third propane;

    • .4 maximum combined concentration of propylene and butadiene of 10 mol%;

  • .2 Composition 2:

    • .1 maximum methyl acetylene and propadiene combined concentration of 30 mol%;

    • .2 maximum methyl acetylene concentration of 20 mol%;

    • .3 maximum propadiene concentration of 20 mol%;

    • .4 maximum propylene concentration of 45 mol%;

    • .5 maximum butadiene and butylenes combined concentration of 2 mol%;

    • .6 minimum saturated C4 hydrocarbon concentration of 4 mol%; and

    • .7 minimum propane concentration of 25 mol%.

  17.16.3 Other compositions may be accepted, provided the stability of the mixture is demonstrated to the satisfaction of the Administration.

  17.16.4 If a ship has a direct vapour compression refrigeration system, this shall comply with the following requirements, subject to pressure and temperature limitations depending on the composition. For the example compositions given in 17.16.2, the following features shall be provided:

  • .1 a vapour compressor that does not raise the temperature and pressure of the vapour above 60°C and 1.75 MPa gauge during its operation, and that does not allow vapour to stagnate in the compressor while it continues to run;

  • .2 discharge piping from each compressor stage or each cylinder in the same stage of a reciprocating compressor shall have:

    • .1 two temperature-actuated shutdown switches set to operate at 60°C or less;

    • .2 a pressure-actuated shutdown switch set to operate at 1.75 MPa gauge or less; and

    • .3 a safety relief valve set to relieve at 1.8 MPa gauge or less;

  • .3 the relief valve required by .2.3 shall vent to a mast meeting the requirements of 8.2.10, 8.2.11 and 8.2.15 and shall not relieve into the compressor suction line; and

  • .4 an alarm that sounds in the cargo control position and in the navigation bridge when a high-pressure switch, or a high-temperature switch, operates.

  17.16.5 The piping system, including the cargo refrigeration system, for tanks to be loaded with methyl acetylene-propadiene mixtures shall be either independent (as defined in 1.2.28) or separate (as defined in 1.2.47) from piping and refrigeration systems for other tanks. This segregation shall apply to all liquid and vapour vent lines and any other possible connections, such as common inert gas supply lines.

Parent topic: Chapter 17 — Special Requirements
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