Best practice no. 25

Solution B. The theorical maximum allowable suction lift h s for this pump at these conditions would be -10.42 ft. A safety margin of 10 percent to allow for variations in suction head flow conditions is recommended. Then: Recommended NPSHR = NPSHR + 0.10 NPSHR = 16 + (0.10 x 16) = 17.6 Substituting this value in the general equation the recommended suction lift:

NPSHR = h s – h f + h a - h vap

17.6 = h s – 5 + 32.8 – 1.38 h s = - 8.82 ft