WPC 2BJZCourier#|x8i6X@`7 @HP LaserJet 4LHPLAS4L.PRS4i6X@`7\-R @ .,., USUK 3'3'Standard6&6&StandardrJet 4Lzư 2CE ZUz#|xHP DeskJet 500HPDES500.PRSx  @xX,,0i϶X@ .,., USUK 3'3'Standard6&6&StandardHPDES500.PRSx  *Ұ 2t "XFZ*Courier 10cpiLetter Gothic 12cpi ?xxx,Zx6X@8;X@1ddd,M]d H@g.;X@2 1 #d H@g.;M]X@# +  b  3 3 $;;).3CC8Distr.  3 3 $;;).3CC8RESTRICTED  3 3 $;;).3CC8ST/SG/AC.10/R.455  3 3 $;;).3CC812 September 1994  3 3 $;;).3CC8Original: ENGLISH COMMITTEE OF EXPERTS ON THE TRANSPORT OF DANGEROUS GOODS (Eighteenth session, Geneva, 28 November 7 December 1994, agenda item 3 (i)) f REVIEW OF CHAPTER 12 AND MULTIMODAL TANK TABLES !Multimodal gas tanks t#Use of gas tanks ( Transmitted by the Expert from Belgium Introduction  1p 1.The existing recommendations are not clear in relation to the degree of filling of tanks for liquefied gases. Tanks are built according to a pressure vessel code which gives them technical characteristics such as the test pressure. The test pressure is at least equal to 1.3 times the maximum allowable working pressure (see paragraph 12.26.2) and the start to discharge pressure of the pressure relief valve is not less than the maximum allowable working pressure (paragraph 12.30.1).  1@ 2.The degree of filling is calculated according to paragraph 12.40 and, for pure gases, is mentioned in table 12.1. The maximum allowable working pressure is not taken into account for determining the degree of filling.  1# 3.Table 12.1 also indicates the maximum allowable working pressure. Furthermore, it is not forbidden to use a tank with a higher maximum allowable working pressure (e.g. for Butane the maximum allowable working pressure is 7 bar; a tank with a maximum allowable working pressure of 21 bar may be used). GE.94 /a:\STR.')))bb  +#  bN ST/SG/AC.10/R.455 page 2 Formulation of the problem  1 4.$$When using a tank with a maximum allowable working pressure that is much higher (e.g. 21 bar) than the maximum allowable working pressure indicated in table 12.1 for that substance (e.g. 7 bar) and the start to discharge pressure of the safety valve is equal to that higher maximum allowable working pressure (e.g. 21 bar) and the degree of filling as mentioned in table 12.1 is used, the following can happen in the event of total fire engulfment:  1` $$| | before the start to discharge pressure of the valve is reached, the tank will be liquid full because the temperature for reaching the start to discharge pressure of the safety valve (e.g. 21 bar) is higher than the reference temperature of 60 $C in paragraph 12.40 and liquefied gases have a high cubical coefficient of expansion.Ɵ#|  1 $$| | the safety valve will relieve liquid. It is not designed to do so and it is very dangerous in the case of flammable liquefied gases (great increase of the fire, great chance of rupture and explosion of the tank).Ɵ#| Action requested  1P 5.$$The Committee is invited to give its opinion whether it is necessary to take account of the foregoing, by lowering the degree of filling or by using a lower set pressure of the safety valve, or whether the risk is negligible and no measures should be taken. 5%  1  $$ $$| |