millwright level 3 > dynamic pumps > Flashcards

dynamic pumps Flashcards

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1
Q
A
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2
Q

What are dynamic pumps also known as?

A

Continuous flow, kinetic, centrifugal, or non-positive displacement pumps

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3
Q

What is the primary difference between dynamic pumps and positive displacement pumps?

A

Dynamic pumps have no seal between the suction and discharge sides and produce a continuous, non-pulsating flow of liquid

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4
Q

When are dynamic pumps typically used?

A

When large volumes of liquid need to be moved at relatively low discharge pressures

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5
Q

What is density?

A

The mass or weight of a substance per unit of volume

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6
Q

What are the typical units of measurement for density in the imperial system?

A

Pounds/cubic foot (Ib/ft)

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7
Q

What are the typical units of measurement for density in the metric system?

A

Kilograms/cubic metre (kg/m³)

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8
Q

What is specific gravity (S.G.)?

A

The ratio of the density of a substance to that of water

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9
Q

What is the specific gravity of water?

A

One

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10
Q

What is the specific gravity of substances lighter than water?

A

Less than one

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11
Q

What is the specific gravity of substances heavier than water?

A

Greater than one

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12
Q

How is pressure defined?

A

A measure of intensity of effort described as force per unit of area

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13
Q

What units are used to measure pressure in the imperial system?

A

Pounds per square inch (psi)

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14
Q

What units are used to measure pressure in the metric system?

A

Newtons per square metre

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15
Q

What is the approximate conversion between psi and kPa?

A

1 psi = 6.9 kPa

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16
Q

What is the formula used to determine pressure?

A

Pressure = force ÷ area

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17
Q

What are gauge readings in pressure measurement?

A

Readings that use atmosphere as a reference point

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18
Q

What are absolute readings in pressure measurement?

A

Readings that use absolute zero as a reference point

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19
Q

What are the abbreviations for gauge readings?

A

psig or kPa gauge

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20
Q

What are the abbreviations for absolute readings?

A

psia or kPa absolute

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21
Q

What is head pressure?

A

Head pressure is the height in feet of a column of water that is one foot square at the base.

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22
Q

How is head pressure calculated?

A

Head pressure is calculated by determining the weight of the water in the vessel and dividing it by the area of the base.

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23
Q

What is the weight of water per cubic foot?

A

Water weighs 62.4 lb/ft³.

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24
Q

What is the weight of water in a vessel that is 10 feet high and has a base of one square foot?

A

The weight of water in the vessel is 624 lb.

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25
What is the formula to find the pressure on the base of the vessel?
Pressure on the base = Weight of water ÷ Area of base.
26
What is the pressure exerted by a 10 foot head of water?
The pressure exerted by a 10 foot head of water is 4.33 psi.
27
What is the head pressure of one foot of water?
The head pressure of one foot of water is 0.433 psi.
28
Fill in the blank: The volume of a tank that is 10 feet high and has a base of one square foot is _______.
10 cu ft
29
True or False: Before pressure gauges were developed, measuring the height of the liquid was the only way to obtain a pressure reading.
True
30
What is head pressure?
Head pressure is the height in feet of a column of water that is one foot square at the base.
31
How is head pressure calculated?
Head pressure is calculated by determining the weight of the water in the vessel and dividing it by the area of the base.
32
What is the weight of water per cubic foot?
Water weighs 62.4 lb/ft³.
33
What is the weight of water in a vessel that is 10 feet high and has a base of one square foot?
The weight of water in the vessel is 624 lb.
34
What is the formula to find the pressure on the base of the vessel?
Pressure on the base = Weight of water ÷ Area of base.
35
What is the pressure exerted by a 10 foot head of water?
The pressure exerted by a 10 foot head of water is 4.33 psi.
36
What is the head pressure of one foot of water?
The head pressure of one foot of water is 0.433 psi.
37
Fill in the blank: The volume of a tank that is 10 feet high and has a base of one square foot is _______.
10 cu ft
38
True or False: Before pressure gauges were developed, measuring the height of the liquid was the only way to obtain a pressure reading.
True
39
What is the specific gravity of cold, fresh water?
One
40
What happens to the power used by a pump when pumping heavier fluids?
The pump uses more power
41
What happens to the power used by a pump when pumping lighter fluids?
The pump uses less power
42
How can the power used for a pump to pump a new liquid be calculated?
Multiply the power required for the pump to pump water by the specific gravity of the new liquid
43
What is the term for the difference between the discharge pressure and the suction pressure of a pump?
Differential pressure
44
What is the head produced by the pump measured in?
Feet of head
45
True or False: The head produced by the pump is equal to the differential pressure converted into psi.
False
46
Fill in the blank: The head produced by the pump is the differential pressure converted into _______.
Feet of head
47
What is pump head?
Pump head is defined in various ways depending on where it occurs in the system: * velocity head * friction head * suction head * discharge head * net positive suction head * net positive suction head required ## Footnote These definitions are crucial for understanding hydraulic systems.
48
How is velocity head defined?
The energy in a system due to the liquid's velocity can be expressed as a velocity head. ## Footnote Velocity head is a measure of the kinetic energy of the fluid.
49
What is the formula for calculating velocity head?
Velocity head (ft) = V² ÷ 2g * V = the velocity measured in feet/second (fps) * g = the acceleration due to gravity (32.2 ft/second/second) ## Footnote This formula helps quantify the energy associated with the fluid's motion.
50
What is friction head?
Friction head is the energy lost due to friction between the liquid and the bore of the pipe as it flows. ## Footnote This energy is converted into heat and sound energy.
51
What factors affect frictional losses in a pipe?
Frictional losses vary according to several factors, including: * the size, type and condition of the piping and fittings * the flow velocity * the viscosity and density of the liquid being pumped ## Footnote Understanding these factors is essential for efficient system design.
52
What happens to the bore area if the pipe diameter is halved?
If the pipe diameter is halved, the bore area is quartered. ## Footnote This affects the flow characteristics significantly.
53
What is the consequence of halving the pipe diameter on flow velocity to maintain the same flow in gpm?
The resulting velocity has to be four times greater to maintain the same flow in gpm. ## Footnote This highlights the importance of pipe diameter in hydraulic systems.
54
What is pump head?
Pump head is defined in various ways depending on where it occurs in the system: * velocity head * friction head * suction head * discharge head * net positive suction head * net positive suction head required ## Footnote These definitions are crucial for understanding hydraulic systems.
55
How is velocity head defined?
The energy in a system due to the liquid's velocity can be expressed as a velocity head. ## Footnote Velocity head is a measure of the kinetic energy of the fluid.
56
What is the formula for calculating velocity head?
Velocity head (ft) = V² ÷ 2g * V = the velocity measured in feet/second (fps) * g = the acceleration due to gravity (32.2 ft/second/second) ## Footnote This formula helps quantify the energy associated with the fluid's motion.
57
What is friction head?
Friction head is the energy lost due to friction between the liquid and the bore of the pipe as it flows. ## Footnote This energy is converted into heat and sound energy.
58
What factors affect frictional losses in a pipe?
Frictional losses vary according to several factors, including: * the size, type and condition of the piping and fittings * the flow velocity * the viscosity and density of the liquid being pumped ## Footnote Understanding these factors is essential for efficient system design.
59
What happens to the bore area if the pipe diameter is halved?
If the pipe diameter is halved, the bore area is quartered. ## Footnote This affects the flow characteristics significantly.
60
What is the consequence of halving the pipe diameter on flow velocity to maintain the same flow in gpm?
The resulting velocity has to be four times greater to maintain the same flow in gpm. ## Footnote This highlights the importance of pipe diameter in hydraulic systems.
61
What does Bernoulli's Principle state?
In the absence of friction, when an incompressible liquid moves at a constant flow rate, energy remains constant but its components may change.
62
What are the two components of total energy in a closed system according to Bernoulli's Principle?
* head pressure * velocity head
63
What happens to the velocity of liquid when the pipe diameter increases?
The velocity of the liquid reduces.
64
How does an increase in pipe diameter affect head pressure?
Head pressure increases as the velocity decreases.
65
In a small diameter pipe, what is the relationship between velocity and pressure?
Velocity is high, so pressure is lower.
66
What occurs to velocity and pressure when liquid flows into a larger pipe?
Velocity decreases and pressure increases.
67
What is ignored in the application of Bernoulli's Principle?
Friction loss.
68
How is Bernoulli's Principle utilized in dynamic pump applications?
To achieve optimum operating conditions and minimal energy losses.
69
Fill in the blank: The total energy in a closed system is the total _______.
head
70
True or False: According to Bernoulli's Principle, energy can be created or destroyed in a flowing liquid system.
False
71
What happens when the diameter of a pump is reduced?
The liquid velocity increases, resulting in a lower pressure ## Footnote This may affect minimum suction and discharge requirements.
72
What are the different ways pump head is defined?
* velocity head * friction head * suction head * discharge head * net positive suction head * net positive suction head required
73
What is defined as the energy in a system due to the liquid's velocity?
Velocity head
74
How is velocity head expressed in a formula?
Velocity head (ft) = V2 ÷ 2g
75
What does 'V' represent in the velocity head formula?
The velocity measured in feet per second (fps)
76
What does 'g' represent in the velocity head formula?
The acceleration due to gravity (32.2 ft/second/second)
77
What is friction head?
Energy converted into heat and sound energy due to friction between the liquid and the bore of the pipe
78
What factors affect frictional losses in a pipe?
* Size, type, and condition of the piping and fittings * Flow velocity * Viscosity and density of the liquid being pumped
79
What happens to the bore area if the pipe diameter is halved?
The bore area is quartered
80
How much must the velocity increase if the pipe diameter is halved to maintain the same flow in gpm?
Four times the previous value
81
If the velocity increases to maintain flow, what happens to the frictional losses?
Frictional losses are four times greater
82
What must be calculated to choose the correct pump in a system?
All friction heads in a system must be calculated
83
What is suction head?
Suction head is when the level of the supply liquid is above the centreline of the pump
84
What is static suction head?
The vertical distance from the centre of the suction eye of the pump to the surface of the supply
85
What is total static head?
The sum of static suction head and static discharge head
86
What is static discharge head?
The vertical distance from the centreline of the pump to the discharge point
87
Fill in the blank: Static suction head is the vertical distance from the centre of the suction eye of the pump to the _______.
surface of the supply
88
True or False: Suction head occurs when the supply liquid level is below the centreline of the pump.
False
89
What does the impeller centreline refer to in a pump system?
The horizontal line that passes through the center of the impeller
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