UP FRONT
05
INBOX Dear Sir,
Dangerous Polymerisers – Flow Capacity through the Pressure Relief System on Tanks
Astute and conscientious readers of your columns will be aware that four new UN numbers will be added to the Dangerous Goods List of the modal regulations from 2017. These are:
UN 3531 POLYMERIZING SUBSTANCE, SOLID, STABILIZED, N.O.S.
UN 3532 POLYMERIZING SUBSTANCE, LIQUID, STABILIZED, N.O.S.
UN 3533 POLYMERIZING SUBSTANCE, SOLID, TEMPERATURE CONTROLLED, N.O.S.
UN 3534 POLYMERIZING SUBSTANCE, LIQUID, TEMPERATURE CONTROLLED, N.O.S.
Let me say straight away that I fully support the decision to provide classification criteria for the inclusion of such substances in the regulations. As I write they will be allocated to Class 4.1, though there is still a query going on as to whether this is the right class for them – some would support inclusion in Class 9 instead. At the same time we are going to be faced with the situation where these substances, which heretofore could be transported as non-dangerous, suddenly become dangerous goods. I hasten to add that I do not have any idea (nor I guess do others - including competent authorities) how many substances will be caught up in these changes, though one assumes that divinyl benzene will be one. Come what may, readers interested in these
developments may like to note that for transport in portable tanks, the T-code T7 has been allocated to them. For operators of portable tanks in the form of the ISO tank container, this is not too much of a problem in itself, I suggest. However where difficulties could potentially
occur surround the decision of the UN Subtcommittee of Experts to assign Portable Tank Special Provision TP6 to these four entries.
TP6 states:“To prevent the tank bursting in any event, including fire engulfment, it [the Portable Tank] shall be provided with pressure-relief devices which are adequate in relation to the capacity of the tank and to the nature of the substance transported. The device shall also be compatible with the substance.” This rule will require, effectively, the
determination of the quantity of vapour that could be produced once a polymerisation reaction starts, to ensure the pressure relief devices have sufficient flow capacity to allow them all to escape and to prevent bursting. Consignors and operators of tanks arguably should start right now determining what flow capacity is needed should polymerisation start and if the tanks currently in service are not provided with sufficient flow capacity alternative tanks substituted or the existing tanks modified. Either way time will be needed to source replacement tanks should that be necessary or to modify existing tanks.
Now, I hope I am not being alarmist and that e.g. it will be found that the flow capacity on existing portable tanks is sufficient to meet the requirements of TP6. However, extended transitional arrangements have been provided to meet TP6. In extremis I could imagine that at least two years may be needed (a) make the flow rate calculations (b) ensure there is sufficient lead time so to source suitable pressure relief devices and then (c) either to then fit the devices to newly constructed tanks or burn holes in existing tanks where the additional and/or larger devices can be fitted. Behind all this may be a need for owner/operators to find the finance to fund the conversions or build new portable tanks.
As it stands at this moment, a 12-month period is all that is allowed to achieve all this for anyone wishing to transport these new dangerous goods by sea (IMDG Code). Anyone needing to use rail, road or inland waterways transport in Europe (RID/ADR/ADN) will only get six months to make the changes. There is a further complication in all this.
In Europe we have another set of provisions for the transport of dangerous goods in tanks found in Chapters 4.3 and 6.8 of RID and ADR. In response to the decisions taken by the UN Subcommittee of experts, the RID/ADR/ADN Joint Meeting had to allocate a European tank code for the transport of these materials. There is no direct equivalent in Chapter 4.3.or Chapter 6.8 to the TP6 assigned to UN portable tanks so their experts came up decided to add the term “(+)
” to their chosen tank codes as a form of
equivalency to TP6. Hmmm... This term effectively either means
that you have to use tanks dedicated to the transport of just one substance or at best a few similar substances – see 4.3.4.1.3 of RID and ADR. I ask whether this is a regulation too far for these substances – to go from non-regulated up to 31.06.2017 when the normal transitional period ends to being regulated in this way? I am told that no consideration was
given either by the UN Subcommittee or the RID/ADR/ADN Joint Meeting to extending the normal transitional periods, by the way. Anyone who may be concerned about these issues ought to contact their modal competent authorities as soon as they can.
Yours sincerely
Roy Boneham Principal Consultant New Alchemy Southport, UK
rboneham@premiumuk.com
WWW.HCBLIVE.COM
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