Common Pumping Mistakes
by Jim Elsey
When you think of your pump knowledge, does the word “ninja” come to mind? Take this quiz and write down your answers. Then find out if you are a true Pump Ninja by referencing the answer key here.

1. A centrifugal pump converts mechanical energy to pressure energy (head). It works…
a) by pure phenomenal magic as the impeller sucks the fluid into the pump and then rapidly expels it in the discharge pipe.
b) because the impeller imparts a velocity to the fluid, and the casing subsequently collects and converts the velocity to pressure head.
c) because the impeller sucks the fluid from the suction side of the system and creates a pressure by utilizing Charles’s and Bernoulli’s Law of Ideal Gases and Fluids in a pressure temperature relationship (fixed volume and constant temperature).

2. If you double the operating speed of a centrifugal pump…
a) the flow rate will double (simple speed ratio).
b) the head generated will increase by a factor of 4 (speed ratio squared).
c) the BHP will increase by a factor of 8 (speed ratio cubed).
d) all of the above: a, b and c.
e) flow, head and BHP will all simply double.

3. Refer to the same pump that you doubled the speed on in the previous question: There would be no need to change the pipe sizes because the higher fluid velocity would compensate for the added friction losses.
a) True
b) False

4. NPSH is an acronym for…
a) net pump suction hysteresis
b) not pumping so hot
c) net positive suction head
d) negative pump static head

5. NPSH3 is an acronym used by pump engineers to designate…
a) that the pump will require 3 times more NPSH than others of the same size.
b) that after three years of operation, the pump will require this amount of suction energy—unless it has a dual suction impeller.
c) the point during an NPSHR test where the developed head will drop by 3 percent with the flow rate held constant.

6. You have a pump with a “flooded suction,” so there is no valid reason to calculate the NPSHA, and to do so would be a waste of time and effort.
a) True
b) False

7. Your new self-priming pump is installed at a location that is basically at sea level. Ignoring friction losses and assuming the water you wish to pump is at or below 70 F (21.1 C), how high is your theoretical maximum suction lift?
a) 2.31 feet
b) 14.7 feet
c) 33.95 feet
d) No limits

8. You are installing a new American National Standards Institute (ANSI) B73.1M pump package that is motor-driven. The motor is 20 horsepower (hp), 460 volt, 3 phase and 60 Hertz. It operates at 3,550 rpm with a service factor of 1.15. It is Insulation Class G, totally enclosed fan-cooled (TEFC) enclosure and rated for chemical duty. You are upset that the manufacturer has not installed the coupling but has instead shipped it in a separate box attached to the baseplate. You …
a) contact the manufacturer to give a piece of your mind and refuse to pay some portion of the bill.
b) quietly install the coupling—and make a promise to never purchase from this vendor again—because of consumer protection afforded by and in accordance with National Electrical Manufacturers Association (NEMA) specifications CFR 19.20-2.BS.
c) realize that the coupling was left off because you have yet to perform a phase rotation check, set the mechanical seal and perform the alignment.

9. Is it 100 percent acceptable to have some water mixed with the oil in the pump bearing housing?
a) As long as it does not exceed 5 percent and the oil viscosity index is above 110
b) As long as the housing operating temperature is above 190 F
c) As long as the water stays below 500 parts per million (5 percent)
d) As long as the oil is a high-grade synthetic with the correct International Organization for Standardization (ISO) designation
e) None of the above

10. A stainless steel (ASM rated 316-SS) pump with 150-pound ANSI flanges is perfectly acceptable to use in which application?
a) With 285 pounds per square inch gauge (psig) suction pressure because the developed differential pressure across the pump will be less than 130 psig
b) With 285 psig suction pressure because you will use raised face flanges and an HP cadmium confined gasket in accordance with ANSI B 31.4 specifications
c) With 285 psig suction pressure because the temperature of the fluid is below 70 F (21.1 C)
d) None of the above. These applications are not acceptable.

11. You can operate any variable speed industrial centrifugal pump at extremely slow speeds (less than 200 rpm) for as long as you want without any ill effects to the pump, especially if it is multistage with close clearance wear rings.
a) True
b) False