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each point. Calculate the difference between ECP and AET for each cut point.

X2.6.9.2 Table X2.4 defines the standard efficiency performance of a Test Method D 2892 TBP (15/5) distillation, including the standard spread for individual data points. Fig. X2.2 is a graphical presentation of the standard efficiency and the acceptable upper and lower limits of Test Method D 2892 column efficiency performance (14 to 18 theoretical plates). A discussion on the acceptability of deviations, probable causes and corrective actions is given in the next chapter.

X2.7 Frequency of Test and Data Interpretation

X2.7.1 It is recommended to carry out a full performance check at the first time of commissioning or any other point of time when there are significant changes to the equipment. After that, a shortened evaluation may be satisfactory, if carried out at regular intervals, for example, once or twice a year, to verify that the equipment is still performing satisfactory.

X2.7.2 Full Performance Check—Determine the ECP and the efficiency ^minimum for at least two, but if possibly three, cut points at each of the three most frequently used pressure levels. One of the cut points should be the maximum cut point (AET) usually obtained at the appropriate pressure level and one of the cut points should be obtained at the lower end of the temperature range usually covered at the appropriate pressure level. Table X2.5 gives an example of such a scheme.

X2.7.2.1 Only three pressure levels are permitted in Test Method D 2892. Distillation at 0.266 kPa provides an alterna-

TABLE X2.4 Standard Efficiency for 15/5, Test Method D 2892 Columns

Note 1—The data from Table X2.4 were estimated from the efficiency results obtained as a spin off of a round robin carried out in 1978 on a crude oil with an API-gravity of 35. However, the lack of detailed documentation of these results prevents rigid statistical treatment.

Cut Point, °C

Standard Efficiency,

^minimum

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