SDI Silt Density Index
P30 % plugging at 2.1 bars (30 psig) feed pressure2
Tt Total test time in minutes2
Ti Time in seconds required to obtain the initial 500 ml (17 fl oz.) sample
Tf Time in seconds to obtain the final 500 ml (17 fl oz.) sample
Notes:
1. The time required to collect a 500 ml (17 fl oz.) sample should be approximately 5-times greater than the time required
to collect a 100 ml (3.4 fl oz.) sample. If the 500 ml (17 fl oz.) sample time is much greater than 5-times that of
the 100 ml (3.4 fl oz.) sample, the SDI should be calculated using 100 ml (3.4 fl oz.) sample collection times.
2. The total test time is usually 15 minutes. However, it may be less than 15 minutes if 75% plugging occurs in less than
15 minutes. To obtain accurate SDI measurements, P30 should not exceed 75%. If P30 does exceed 75%, the test
should be repeated to obtain Tf in a shorter period of time (T)