Below are the questions with the correct answer only. Total up the number of answers you got correct and see if you are a Pump Ninja at the end of the article. If you missed the issue, take this quiz here.
1. A centrifugal pump converts mechanical energy to pressure energy (head). It works…
b) because the impeller imparts a velocity to the fluid, and the casing subsequently collects and converts the velocity to pressure head.
2. If you double the operating speed of a centrifugal pump…
d) all of the above: a, b and c.
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.
4. NPSH is an acronym for…
c) net positive suction head
5. NPSH3 is an acronym used by pump engineers to designate…
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.
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?
c) 33.95 feet
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 …
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?
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?
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.
12. A typical centrifugal pump operating backward (rotation in opposite direction) will…
d) will generate about 50 percent of its normal flow and, depending on the specific speed of the impeller, produce 45 to 65 percent of the normal head.
13. Water will boil at what temperature (F)?
e) It depends on the pressure.
14. Cavitation is defined as…
c) the formation of vapor bubbles in the fluid due to a drop below its vapor pressure and the subsequent collapse of those bubbles as the fluid moves to an area of higher pressure.
15. If you cannot hear the pump cavitating, then it is not cavitating.
16. Which fluid, when subjected to cavitation conditions, will normally create the most damage in a pump (assuming all other conditions are the same)?
e) water at 68 F
17. Specific speed (Ns) is generally defined as…
d) a calculation method (tool) and subsequent result (with no units) to define the impeller geometry and performance characteristics.
18. Which best describes suction specific speed (Nss)?
a) A concept calculation (no units in the answer) initially postulated by a guy named Igor in his kitchen with several other pump engineers over breakfast on a Saturday morning in the 1930s
19. Submergence is defined as…
c) the vertical distance from the pump inlet pipe to the top of the liquid being pumped.
20. Submergence is an important parameter to the pump because…
e) Both b and c.
21. Pump shafts have hp and speed limitations. Which of these apply?
d) All of the above.
22. When starting up a centrifugal pump, the suction valve should always be…
b) fully open.
23. When starting up a centrifugal pump, the discharge valve should be…
d) It depends. All of the above can apply or not because it depends on the pump specific speed, the system design and operating procedures.