UN/SCETDG/17/INF.37

Sub-Committee of Experts on the

Transport of Dangerous Goods

(Geneva, 6-15 December 1999,

agenda item 5 (a))

Results of the Informal Working Group on ST/SG/AC.10/C.3/1999/93

Draft amendments to the Model Regulations

6.7.2.1	Replace (b) (i) below the headings Maximum allowable working pressure (MAWP) and Design pressure to read:

"(i) the absolute vapour pressure (in bar) of the substance at 65 °C [(at the highest temperature during filling, discharge or transport for elevated temperature substances transported above 65 °C)], minus 1 bar;"

6.7.2.2.17	Add the following new paragraph:

"6.7.2.2.17	Thermal insulation directly in contact with the shell intended for substances transported at elevated temperature shall have an ignition temperature at least 50 °C higher than the maximum design temperature of the tank."

6.7.2.5	Add the following new paragraphs:

"6.7.2.5.12 The heating system shall be designed or controlled so that a substance cannot reach a temperature at which the pressure in the tank exceeds its MAWP or causes other hazards (e.g. dangerous thermal decomposition).

6.7.2.5.13	The heating system shall be designed or controlled so that power for internal heating elements shall not be available unless the heating elements are completely submerged. The temperature at the surface of the heating elements for internal heating equipment, or the temperature at the shell for external heating equipment shall, in no case, exceed 80% of the autoignition temperature (in °C) of the substance carried.

6.7.2.5.14	If an electrical heating system is installed inside the tank, it shall be equipped with an earth leakage circuit breaker with a releasing current of less than 100mA.

6.7.2.5.15	Electrical switch cabinets mounted to tanks shall not have a direct connection to the tank interior and shall provide protection of at least the equivalent of type [IP 56] according to IEC 144 or IEC 529."

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