The calculation of the weight per unit volume from the specific gravity is based on
the US measure of volume (i.e., US gallons). A summary table of the relationship
between specific gravity at 60
F,
API, and lbs per gallon is shown in Table 13.
ASTM Distillations
There are two types of ASTM distillations that are used in the refinery for plant
control and finished product quality. These are the ASTM D86 for naphtha and its
equivalent products and for kerosenesand ASTM D1160. ASTM D1160 is an
equivalent method run at reduced pressures.
ASTM D86
The diagram in Fig. 1 is the apparatus used for ASTM distillations. Only the
apparatus item sizes will change and the temperature levels in the condenser bath.
The measured sample is introduced into a glass Engler flask (A) at 100 ml for the
D86 test. The liquid fills about two-thirds of the flask, leaving the space above the
liquid to the cork in the vessel neck as vapor space. About halfway along the neck of
the flask, there is a vapor offtake tube. The open end of this tube is connected to the
condenser tube which is routed through the condenser bath (B). This condenser tube
Table 13 Relationship of specific gravity at 60
F,
API, and lbs/US gal
API
10
20
30
40
50
60
Spec gravity
1.000
0.934
0.878
0.825
0.780
0.739
Lbs/gal
8.328
7.778
7.296
6.870
6.490
6.151
A
B
C
D
E
F
Fig. 1 Diagram of a typical ASTM distillation apparatus
Quality Control of Products in Petroleum Refining
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