Keywords: Ammonia safety, Stress corrosion, Liquid ammonia, Cracking.

Safe operation of liquid ammonia storage tanks depends on good control of the tendency for stress corrosion cracking in the welds. Institute for Energy Technology has performed four research projects in the field of ammonia stress corrosion cracking for an international group of ammonia producers and safety authorities over a ten year period. The research work includes both the effect of various oxygen and water contents in the ammonia, prevention of SCC with electrochemical methods, crack growth rate studies and the behaviour of different welds. Both ambient temperature pressure vessels and low temperature ammonia storage tanks operating at -33^oC are covered. The results from these research projects are summarised and practical recommendations are given for both construction, inspection, repair, commissioning and recommissioning and operation of ammonia storage tanks.

R Nyborg, L Lunde and P-E Drønen, Institute for Energy Technology, Kjeller, Norway.

35 pages, 14 figures, 2 tables, 35 refs.