De-Commissioning of Ammonia Cold-Storage Tanks

Keywords: Ammonia storage, Maintenance procedures, De-commissioning.

This paper describes the recent de-commissioning and re-commissioning of two large liquid ammonia storage tanks; one on the Ny-Nitrogen site at Fredericia in Denmark and the other on the Kemira fertiliser production site at Ince in the United Kingdom.

As these types of tank are inspected very infrequently it is difficult to build up a familiarity with the de-commissioning and re-commissioning of them. It is common for the personnel involved to have no previous first hand experience of such tasks and for much experience from previous outages to have been forgotten. For this reason alone it is valuable to make good records of plans and actual experiences for use in future shutdowns and to allow others to learn.

In addition, there is more than one way to carry out a tank outage. Many differing techniques have been used successfully and what is ideal for one situation is often not so suitable for others. The two tank inspections described here took place in very different situations and therefore different approaches were required. Despite following the same basic procedures the two projects were carried out in markedly different ways.

The challenges faced are described in detail along with the methods chosen for overcoming them. Accounts of the shutdowns are included along with actual timings. The findings of the tank inspections are described briefly.

The conclusion reflects upon the shutdowns and looks forward to the next whilst drawing comparisons between the two approaches.

Jan Kristensen, Ny-Nitrogen A/S, Fredericia, Denmark.

Rob Fogg, Kemira Agro UK Ltd, Ince, Chester, UK.

44 Pages, 20 Figures, 3 Tables.