Chapter 29 Flashcards
(30 cards)
Frequently, a lubricating material such as _____, called the saturant, is incorporated into the packing material.
Select one:
A.
Lead
B.
Antimony
C.
Oil
D.
Soap
E.
Graphite
E.
Graphite
Which of the following statements about centrifugal pumps is false?
Select one:
A.
Make sure an adequate flow of cooling liquid is flowing to the seal
B.
Start the pump with the inlet valve closed
C.
Start the pump with the discharge valve closed
D.
Vent any air present from the seal housing before start up
E.
Never run the pump in a dry condition even for a few minutes
B.
Start the pump with the inlet valve closed
Possible causes of a centrifugal pump experiencing excessive vibration may include all of the following except:
Select one:
A.
Pump misalignment
B.
Balanced rotor
C.
Gas or air in liquid
D.
Insufficient suction head
E.
Worn or loose bearings
B.
Balanced rotor
To reduce leakage around the pump shaft where it passes through the casing, rings of packing, made of a _____ yet durable material, are placed in the stuffing box.
Select one:
A.
Hard, pliable
B.
Hard, ductile
C.
Soft, stiff
D.
Soft, pliable
E.
Stiff, malleable
D.
Soft, pliable
A leaking mechanical seal may be caused by all of the following except:
Select one:
A.
Seal housing bolts too tight, causing distortion of rings
B.
Misalignment of piping, causing distortion of pump parts
C.
Smooth seal faces
D.
Excessive pump shaft vibration
E.
“O” ring gaskets cut or nicked during installation
C.
Smooth seal faces
Wear rings are found in dynamic centrifugal pumps between the:
Select one:
A.
Volute and the diffuser
B.
Impeller and the casing
C.
Volute and the casing
D.
Impeller and the volute
E.
Diffuser and the impeller
B.
Impeller and the casing
Possible causes of a centrifugal pump experiencing overheated bearings may include all of the following except:
Select one:
A.
Moisture in oil
B.
Dirt in bearings or oil
C.
Oil level too low
D.
Poor or wrong grade of oil
E.
Sufficient cooling water
E.
Sufficient cooling water
Misalignment of shafts connected by rigid couplings does NOT cause:
Select one:
A.
Low pump flows
B.
Excessive wear of the bearings
C.
Increased power consumption
D.
Shaft failure, vibrations and noise
E.
Overheating of bearings
A.
Low pump flows
Possible causes of a centrifugal pump not delivering enough liquid may include all of the following except:
Select one:
A.
Air leaks in suction line and stuffing boxes
B.
Undersized foot valve
C.
Worn wearing rings
D.
Damaged impeller
E.
Suction head too high
E.
Suction head too high
What size packing should be used if the stuffing box bore on a pump is 50.8 mm (2 in.) and the shaft diameter is 41.275 mm (1.625 in.)?
Select one:
A.
4.76 mm (3/16 in)
B.
6.35 mm (1/4 in)
C.
19.05 mm (3/4 in)
D.
12.7 mm (1/2 in)
E.
9.525 mm (3/8 in)
A.
4.76 mm (3/16 in)
When the pump is located above the source of supply and a separate hand-operated priming pump is used the pump is primed in the following manner except:
Select one:
A.
The priming pump valve is shut and the main pump is primed
B.
Close the discharge valve
C.
Water issues from the priming pump discharge
D.
Close the priming valve
E.
The pump is operated exhausting air from the main pump casing and suction line
D.
Close the priming valve
Flexible couplings will compensate for:
Select one:
A.
Axial shaft misalignment
B.
Shaft eccentricity due to a badly bent shaft
C.
Overheating of packing
D.
Impeller imbalance
E.
Worn bearings
A.
Axial shaft misalignment
Possible causes of a centrifugal pump overloading the driver may include all of the following except:
Select one:
A.
Speed too low
B.
Wrong liquid, viscosity too high
C.
Wrong direction of rotation
D.
Packing too tight
E.
Discharge head too low resulting in excessive capacity
A.
Speed too low
The usual materials favored for wear rings are _____ which tend to wear in a smooth manner.
Select one:
A.
Bronze and cast iron
B.
Bronze and copper
C.
Bronze and steel
D.
Copper and cast iron
E.
Brass and cast iron
A.
Bronze and cast iron
Priming of a centrifugal pump means:
Select one:
A.
Evacuating the casing of air
B.
Starting the pump first
C.
Filling the casing with the fluid being pumped
D.
Installing a foot valve on the pump discharge line
E.
Filling the casing and suction line with the fluid being pumped
E.
Filling the casing and suction line with the fluid being pumped
When the pump is located above the source of supply and the priming water comes from an external source the pump is primed in the following manner except:
Select one:
A.
Water flows into the pump and suction line where it is prevented from escaping by the foot valve
B.
Close the discharge valve
C.
Open the external supply valve
D.
Open the air vent valve
E.
When air flows from the vent valves the pump is primed
E.
When air flows from the vent valves the pump is primed
What size packing should be used if the stuffing box bore on a pump is 76.2 mm (3 in.) and the shaft diameter is 57.2 mm (2.25 in.)?
Select one:
A.
4.76 mm (3/16 in)
B.
12.7 mm (1/2 in)
C.
19.05 mm (3/4 in)
D.
9.525 mm (3/8 in)
E.
6.35 mm (1/4 in)
D.
9.525 mm (3/8 in)
Possible causes of a centrifugal pump stuffing box overheating may include all of the following except:
Select one:
A.
Excessive seal lubricant
B.
Insufficient packing lubricant
C.
Incorrect installation of packing
D.
Packing too tight
E.
Wrong grade of packing
A.
Excessive seal lubricant
Packing in the stuffing box of a centrifugal pump:
Select one:
A.
Should not stop leakage entirely
B.
Should stop leakage entirely
C.
Consists of ceramic and graphite components
D.
Be of an extremely hard material
E.
Requires no lubrication
A.
Should not stop leakage entirely
Possible causes of a centrifugal pump discharge pressure being too low may include all of the following except:
Select one:
A.
Speed too low
B.
Impeller diameter too large
C.
Damaged impeller
D.
Worn packing
E.
Worn wearing rings
B.
Impeller diameter too large
In the case where the pump is below the source of supply the pump is primed in the following manner except:
Select one:
A.
When water flows from the vents the pump is primed
B.
Trap the air in the pump casing
C.
Open the air vent valve
D.
Open the suction valve
E.
Close the discharge valve
B.
Trap the air in the pump casing
Which of the following statements about stationary mechanical seals is false?
Select one:
A.
The mating ring is fastened rigidly to the shaft
B.
As the pump shaft turns, so does the mating ring
C.
The spring is held stationary within the pump housing
D.
As the pump shaft turns, so does the sealing ring
E.
The sealing ring is held stationary within the pump housing
D.
As the pump shaft turns, so does the sealing ring
Wear rings for a centrifugal pump can be installed on the:
Select one:
A.
Stuffing box
B.
Pump casing or shaft or both
C.
Pump shaft
D.
Impeller or casing or both
E.
Seal cage
D.
Impeller or casing or both
Possible causes of a centrifugal pump experiencing rapid bearing wear may include all of the following except:
Select one:
A.
Vibration
B.
Excessive thrust due to mechanical failure
C.
Lack of lubrication
D.
Wrong bearings
E.
Straight shaft
E.
Straight shaft
