Flow Cups Equations
These equations convert cup drain time, collected at 25 °C and between the minimum and maximum drain times indicated, into kinematic viscosity values in mm²/s (cSt). For more information on cups, contact Technical Service.
Equations and ranges of viscosity flow cups at 25 °C
|
Cup number |
Equations† where |
Drain time (sec) |
Approximate kinematic viscosity (cSt) |
||
|
min |
max |
min |
max |
||
|
Zahn Cup (see ASTM D4212) |
|||||
|
1 |
n = 1.1 (t−29) |
35 |
80 |
5 |
60 |
|
2 |
n = 3.5 (t−14) |
20 |
80 |
20 |
250 |
|
3 |
n = 11.7 (t−7.5) |
20 |
80 |
100 |
800 |
|
4 |
n = 14.8 (t−5) |
20 |
80 |
200 |
1200 |
|
5 |
n = 23t |
20 |
80 |
400 |
1800 |
|
Shell Cup (see ASTM D4212) |
|||||
|
1 |
n = 0.226 (t−13) |
20 |
80 |
2 |
20 |
|
2 |
n = 0.576 (t−5) |
20 |
80 |
10 |
50 |
|
2½ |
n = 0.925 (t−3) |
20 |
80 |
20 |
80 |
|
3 |
n = 1.51 (t−2) |
20 |
80 |
30 |
120 |
|
3½ |
n = 2.17 (t−1.5) |
20 |
80 |
40 |
170 |
|
4 |
n = 3.45 (t−1) |
20 |
80 |
70 |
270 |
|
5 |
n = 6.5 (t−1) |
20 |
80 |
125 |
520 |
|
6 |
n = 16.2 (t−0.5) |
20 |
80 |
320 |
1300 |
|
Ford Cup (see ASTM D1200) |
|||||
|
1 |
n = 0.49 (t−35.0) |
55 |
100 |
10 |
35 |
|
2 |
n = 1.44 (t−18.0) |
40 |
100 |
25 |
120 |
|
3 |
n = 2.31 (t−6.58) |
20 |
100 |
49 |
220 |
|
4 |
n = 3.85 (t−4.49) |
20 |
100 |
70 |
370 |
|
5 |
n = 12.1 (t−2.00) |
20 |
100 |
200 |
1200 |
† While the above equations are widely used, n = at − b/t is often more applicable at short flow times and low KV
