General Pump Knowledge

Question 1

Affinity Law: What is “X” in Q2 = Q1*(N2/N1)^X

Answer 1

1

Question 2

Affinity Law: What is “X” in h2 = h1*(N2/N1)^X

Answer 2

2

Question 3

Affinity Law: What is “X” in bhp2 = bhp1*(N2/N1)^X

Answer 3

3

Question 4

What is the equation for specific speed?

Answer 4

Ns = (N*Qbep^.5)/(Hbep^.75)

Question 5

What is the equation for suction specific speed?

Answer 5

Nss = (N*Qbep^.5)/(NPSHRbep^.75)

Question 6

When calculating Nss for a double-suction, what flow do you use?

Answer 6

Qbep/2

Question 7

When calculating Nss for a double-suction, what NPSHR do you use?

Answer 7

NPSHbep

Question 8

What trim recovery is typical recovered by underfile?

Answer 8

3/16” to 1/4” Trim

Question 9

When flow increases, what may happen to NPSHA? Why?

Answer 9

decrease - frictional losses in suction

Question 10

Stepping NPSH curve upward requires what exponent?

Answer 10

2

Question 11

Stepping NPSH curve downward requires what exponent?

Answer 11

1.6

Question 12

Degree of expansion in a volute to avoid recirculation is —

Answer 12

below 7-10 degrees

Question 13

What % drop in efficiency is typical for an inch of trim?

Answer 13

1%

Question 14

Specific Speed, number of vanes, and vane discharge angle can be used to determine what?

Answer 14

% head rise from BEP to shut off (Lobanoff p30)

Question 15

Define peripheral speed

Answer 15

The speed that a point in the circumference of a certain radius moves about it’s axis.

Question 16

Define Cm1

Answer 16

Average velocity at vane inlet

Question 17

Define Cm2

Answer 17

Radial velocity at impeller discharge

Question 18

Define B1

Answer 18

Blade radius at outer radius of impeller eye

Question 19

Define Ut and give formula

Answer 19

Peripheral velocity of impeller blade = ED*N/229