Issue 20

A. Borruto et alii, Frattura ed Integrità Strutturale, 20 (2012) 22-31; DOI: 10.3221/IGF-ESIS.20.03 24 1) Arabian Light: the medium percentage is 45%, characterized by two negative peaks, the first one in June (29.01%) and the second one in November (31.77%). 2) Arabian Medium: the medium percentage is 24% till June and nears 0% in September. 3) Ural: the medium percentage is very low till May (6.6%), then, after May, it remains at 21%. 4) Basrah: this crude is added in a small percentage till March (3.2%). 5) Buri: the medium percentage is about 11% from January to March, at 0% in April, May, June and 13% from July to November. 6) Iranian Heavy: this crude is fed in April; the medium percentage remains at 18% in the following months. 7) Bonny Light: this crude is added in very small percentages till June (1.5%). Figure 2 : Crude composition (weight %) during the last operating year. In November the feed’s composition was: 31.77% Arabian Light, 27.67% Ural, 18.36% Buri and 22.20% Iranian Heavy. As a consequence of this crude oil charge, a variation in the working conditions of the pipes is observed:  sulphur percentage entering the furnace S% = 3.3;  TAN of the feed charge entering the furnace 0.39. Annual graphic of the crude blending mass rate G M (t/h) in function of time (month) is shown in Fig. 3. In the penultimate operating year a relevant but slow decrease in the flow rate is shown from January to April. A fast increase occurred from April to May. During the last operating year, again, a flow rate decrease is noticed in April, but this is negligible compared to the one which occurred in the penultimate operating year. The data processed in the atmospheric distillation unit shows that the thickness of the pipe walls during the last two operating years decreased from 7.14 mm to 4.30 mm. Figure 3 : Comparison of crude blending mass rate v.s. the time.