Hi,
Hydraulic institute 14.6 edition 2011 says
In clause 14.6.6.1.1 Translation of test result into data based on the specified speed of rotation (or Frequency) and density, says
(NPSHR)T =(NPSHR)(nsp/n)^x
Where,
(NPSHR)T NPSHrequired during test
NPSHR Actual value...