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Transcript of 1 Pumping 101. 2 Learning Outcomes Upon completion of this training one should be able to: Know what...
1
Pumping 101
2
Learning OutcomesUpon completion of this training one should be able to:
•Know what are the key pump components and how they impact pump performance.
•Know what the impact of pump efficiency is on annual operating cost.
•Know what TDH is and how to calculate it.
•Define the three Pump Affinity Laws.
•Know the difference between NPSHR and NPSHA.
•Describe the difference between series and parallel pumping.
•Know what WWE is.
•Know the difference between a dry running and wet running pump.
3
Unit 1Pump Mechanics
4
What is a pump?
5
What is a Pump?
• A pump is a machine which adds energy to a fluid for the purpose of increasing the pressure or moving it along a pipeline.
• Pumps don’t make water.• Pumps don’t make pressure, it just operates
against the pressure.
6
Basic Types of Pumps
• Positive displacement pumps, add energy directly to a movable boundary, which imparts the energy to the fluid.– Examples include screw pumps, piston
pumps, gear pumps.• Roto-dynamic pumps, add the energy
indirectly through a rotating part in the form of velocity, and subsequently converts the velocity to pressure.– These pumps are commonly referred to as
centrifugal pumps.
7
Basic Impeller Types
OPEN SEMI-OPEN CLOSED
8
Impeller Discharge Configurations
9
Centrifugal Impellers
A. Width = Flow
B. Diameter = Head
C. Vane Design = BEP / Efficiency
B
AC
10
Impeller Direction of Rotation
11
The fluid enters the pump through the inlet (suction eye) where the impeller adds energy (in the form of velocity) through centrifugal force.
When the fluid leaves the impeller, there is a decrease in velocity.
Velocity and pressure are inversely proportional.
The decrease in velocity results in an increase in pressure as the fluid leaves the pump.
Centrifugal Action
12
Other Pump Parts
• Coupling: Connects motor to shaft.
• Shaft: Mount for impeller.
• Bearings: Keeps shaft aligned.
• Mechanical Seal: No leak at shaft.
• Nameplate: Data about pump.
13
Dry Running (Three-Piece)
• Requires shaft seal.• Can change the size of motors.• Repairable.
Shaft Seal
14
Dry Running (Three-Piece)
Shaft Seal
• Requires shaft seal.• Can change the size of motors.• Repairable.
15
Wet Running (Wet Rotor)
• Does not require shaft seal.• Cannot oversize motors.• Not repairable.
16
Wet Running (Wet Rotor)
• Does not require shaft seal.• Cannot oversize motors.• Not repairable.
Water Cooled Areas
17
Questions on Wet Runners
• Can you mount a wet running pump in a vertical position with the bearing facing up? – No, airlock can occur. Also, the bearings may not be
lubricated which could cause bearing failure.
• Can you pump syrup with a wet running pump? – No, the “fluid” lubricates the pump and pumping syrup
would generally gum up the pump.
18
Unit 2Pump Curves, Affinity
Laws, and System Curves
19
A TypicalPump Curve
Format
Performance Curve
Efficiency ( or eta) Curve
BHP Curve
NPSHr Curve
20
A Typical Catalog Performance Curve
21
Head, H
• Centrifugal pump curves are generally not rated in psi.
• Rating is in feet of head.• Total Dynamic Head (TDH) is found by adding:
1. Elevation (He) – rated in feet.2. Pressure (Hp or ∆P) – rated in psi.3. Friction loss (Hf) – usually rated in feet.
22
Determining Elevation Head (He)
What is the total elevation head of the above system?200 ft
200 ft
S
D
23
2.311 psi = _______ Feet of Water*
2.31 feet
Converting Between Head and Pressure
*Water @ 32°F ~ 60°F
1 psi
24
Converting between Hp & ∆P
..
31.2)()(
gs
psiPftH
31.2
..)()(
gsftHpsiP
Pg. 8 HVAC Technical Guide
25
What is 2.31?
31.24.62
144 3
2
2
2
lb
ftX
ft
inX
in
lb
Where:62.4 = specific weight of water @ 32°F ~
60°F
26
100 ft
23 ft
80 ft
43.29 psi 34.6 psi 9.956709957 psi
Head and Pressure Based on Water
27Gasoline Salt Water Sugar Water0.70 s.g. 1.03 s.g. 1.30 s.g.
165 ft 165 ft165 ft
50 psi 50 psi93 psi74 psi50
psi
Effect of s.g. on Pressure and Head
28
Determining Friction Head
29
Friction of WaterAsphalt-dipped Cast Iron and New Steel Pipe
(Based on Darcy’s Formula) 8 Inch
Note: No allowance has been made for age, difference in diameter, or any abnormal condition of interior surface., Any factor of safety must be estimated from the local conditions and the requirement of each particular installation. It is recommended that for most commercial design purposes a safety factor of 15 to 20% be added to the values in the tables.
Asphalt-dipped Std. wt. steel Extra strong steel cast iron sch 80 Schedule 160 steel
8.0" inside dia. 7.981" inside dia. 7.625" inside dia. 6.813" inside dia.Flow Ve- Ve- Head Ve- Ve- Head Ve- Ve- Head Ve- Ve- HeadU.S. locity locity loss locity locity loss locity locity loss locity locity lossgal. ft. per head ft. per ft. per head ft. per ft. per head ft. per ft. per head ft. per
per min. sec. ft. 100 ft. sec. ft. 100 ft. sec. ft. 100 ft. sec. ft. 100 ft.130 .83 .011 .037 .83 .011 .036 .91 .01 .046 1.14 020 .079140 .89 .012 .042 .90 .013 .042 .98 .01 .052 1.33 024 .090150 .96 .014 .048 .96 .014 .047 1.05 .02 .059 1.32 027 .102160 1.02 .016 .054 1.03 .016 .053 1.12 .02 .066 1.41 031 .115170 1.08 .0187 .060 1.09 .018 .059 1.19 .02 .074 1.50 035 .128180 1.15 .021 .067 1.15 .021 .066 1.26 .02 .082 1.58 039 .142190 1.21 .023 .067 1.22 .023 .073 1.33 .03 .091 1.67 043 .157200 1.28 .025 .082 1.28 .026 080 1.41 .03 .099 1.76 048 .172220 1.40 .031 .098 1.41 .031 .095 1.55 .04 .118 1.94 058 .205240 1.53 .037 .115 1.54 .037 .111 1.69 .04 .139 2.11 069 .241
30
Friction in Fittings
The friction loss through one 1¼ inch standard
90° elbow is equal to the friction loss through
how many feet of straight 1¼ inch pipe?
3.6 ft
These are NOT friction
values!!!
31
Friction Head
10 gpm thru 250 ft – 1” Sched. 40 steel pipe
1. What is the friction head in feet? _______________
2. What is the pressure head in feet? _______________
3. What is the elevation head in feet? _______________4. What is the total head? (4 = 1+2+3) _______________
0 ft
0 ft
17 ft
17 ft
S D
Total Length Per
100’ Friction Factor Total Friction Loss
250 ÷ 100 X 6.81 = 17
32
Calculating Horsepower
3 9 6 0
s .g .T D Hgp mW H P (P 3 )
p u mpp u mp η3 9 6 0
s .g.T D Hgp m
η
W H PB H P (P 2 )
mo t o rp u mpmo t o rp u mpmo t o r ηη3 9 6 0
s .g.T D Hgp m
ηη
W H P
η
B H PE H P (P 1 )
33
Where do we get “3960” ?
1HP = 550 Foot Pounds per SecondX 60 Seconds per Minute33,000 Foot Pounds per Minute÷ 8.333 Pounds per Gallon of Water3960
34
Practice Problems
• What is WHP(P3) for a pump moving 200 gpm of 60°F water against a TDH of 500’?
(200 gpm X 500 feet) ÷ 3960 = 25.25 WHP
35
Practice Problems
• What is BHP(P2) if the efficiency of the pump is 83%?
25.25 WHP ÷ 0.83 = 30.42 BHP
36
Practice Problems
• What is EHP(P1) if the efficiency of the motor is 90%?
30.42 BHP ÷ 0.90 = 33.81 EHP
37
Convert EHP to Kilowatts
33.81 EHP X 0.746 = 25.21 kW
• What is kW value if the EHP of the pump is 33.81?
38
Calculate Energy Cost
25.21 kW
X 1000 hours per year
25,210 kW/hrs per year
X $0.10 per kWh
$2,521.00 cost per year
39
An Important Point!!!!!
• At a given speed, with a given impeller diameter:the pump will perform along its characteristic curve, from run out to shut off.
40
Pump Affinity Laws
41
FLOW changes DIRECTLY as a change in speed or diameter*
HEAD changes as the SQUARE of a change in speed or diameter*
HORSEPOWER changes as the CUBE of a change in speed or diameter*
FLOW changes DIRECTLY as a change in speed or diameter*
HEAD changes as the SQUARE of a change in speed or diameter*
HORSEPOWER changes as the CUBE of a change in speed or diameter*
Pump Affinity Laws
* May not be true for higher specific speeds
42
3
2
1
2
1
*
2
1
2
1
2
2
1
2
1
*
2
1
2
1
2
1
2
1
*
2
1
2
1
N
N
BHP
BHPOR
D
D
BHP
BHP
N
N
H
HOR
D
D
H
H
N
N
Q
QOR
D
D
Q
Q
Important...Remember these:
Pump Affinity Laws
Pg. 14 HVAC Technical Guide
43
What are the affects of the Affinity Laws?
%SPEED
POWER
PG: 113PG: 113
HEAD
FLOW
44
As we trim, we would expect the efficiency to stay the same, but remember the internal losses!
What are the affects of the Affinity Laws?
ACTUAL PUMP CURVE
HH
THEORETICAL PUMP CURVE
LOSSES DUE TO SHOCK, TURBULENCE, RECIRCULATION AND FRICTION
45
Catalog Pump Curve
46
System Curves
47
Creating a System Curve
48
Graph the head required through point for 100’ Equivalent Length of 2” Type L Copper Tubing for the following flows:
GPM 10 20 30 40 50
TDH .29
•
.98
•
2.01
•
3.36
•
5.01
•
•
Creating a System Curve
49
Graph the head required through point for 200’ Equivalent Length of 2” Type L Copper Tubing for the following flows:
GPM 10 20 30 40 50
TDH
•
.58
• ••
•
•
•
1.96
•
4.02
•
6.72
•
10.02
•
•
Creating a System Curve
50
System Curve
51
Operating Point
Duty Point
System and Pump Curves
52
System CurvesOpen System w/ Static Head
53
System CurvesOpen System w/ Static Head
54
Overlaying the pump curve and the system curve for systems with static head
Operating Point
Duty Point
System Curves
55
Unit 3 NPSH &
Multiple Pump Operation
56
NPSH
Net Positive Suction Head
57
Why Worry About NPSH ?
• Pumps Don’t Suck.
58
• The fluid needs to enter the impeller before the impeller can begin adding energy.
• NPSH defines the energy available to the fluid above it’s vapor pressure.
Remember Pump Basics
59
Two “Types” of NPSH
• NPSHR is the NPSH required by the pump.– It is a function of the pump design. (This is the NPSH shown on
the pump curve.)
• NPSHA is the NPSH available to the pump. – It is a function of the system design.
60
NPSH is Like a Checkbook
• NPSHR is like the money needed to pay your bills
• NPSHA is income.
• You need much more income than bills!
61
The “Rule”:
For practical purposes, forget the equal sign:NPSH Available must be GREATER than theNPSH Required.
NPSHA NPSHR
62
Take This Note!!!!
• Add minimum 2 foot safety factor to NPSHR!
63
NPSHR
• Chief factors influencing NPSHR include:– impeller eye area– vane inlet design– the relationship with the casing.
• NPSHR is determined by factory testing.
64
NPSHA
• The NPSHA is influenced by several factors, many of which are controllable or modifiable.
• These factors include:– Absolute pressure– Vapor pressure– Suction pressure– Friction loses– Highly aerated water (as seen in cooling towers)
65
NPSHA Formula
• NPSHA = HA + HS - HVPA - HF
• Where:
• HA = Absolute pressure
• HS = Suction pressure (head)
• HVPA = Vapor pressure
• HF = suction piping Friction head
66
In Suction Lift Example B, HS will be a Negative
Number
67
Question:
• What is difference between PSI, PSIA and PSIG?
– PSI is a unit of measurement.
– PSIG is Gauge pressure, and is relative to atmospheric pressure (reads 0 psi on the bench).
– PSIA is Absolute pressure, and includes atmospheric pressure (reads about 14.7 psi on the bench at sea level).
68
Absolute Pressure
• The absolute pressure is the pressure (energy) added to the fluid by an outside source.
• In an open system, this is the atmospheric pressure.
69
Atmospheric Pressure• 1 PSI = 2.31 ft H20 @ 70OF
= 2.0438 inches of mercury (hg).• 14.7 PSI = 33.9 ft = 30 inches of mercury (hg).• (Watch the weather report!)
70
Atmospheric Pressure vs. AltitudeAtmospheric Pressure Pg. 31 HVAC
Technical Guide
71
Vapor Pressure of Water
Pg. 30 HVAC Technical Guide
72
Vapor Pressure Curve
73
Multiple Pump Operation
74
Pumping in Series
75
Pumping in Parallel
76
Unit 4The Cost of Pumping
77
Cost Per Hour of Pumping
$ /k W H.7 4 6 (k W ) W W E3 9 6 0
s .g .T D Hg p mC P H
$ /k W H.7 4 6 (k W ) ηη3 9 6 0
s .g.T D Hgp mC P H
mo t o rp u mp
WWE = Wire To Water EfficiencyFixed Speed WWE = (PE) (ME)Variable speed WWE = (PE) (ME) (DE)
OR
78
Calculating Operating CostsDESIGN POINT: 3200GPM @ 160’TDH
(PUMP “A”)
79
Calculating Operating Costs Assume $0.10 /kWH Assume 92% Motor Efficiency Assume 84.5% Pump Efficiency Assume 1 Pump Assume 24 Hrs / Day Assume 365 Days / Yr Assume 60°F Water (s.g. = 1)
80
Calculating Operating Costs
≈ $108,711 / YEAR
1 0..7 4 6 9 2.8 4 5.3 9 6 0
11 6 02 0 03C P H
1 0.7 4 6.5.0 7 8,3
0 0 0,5 1 2C P H
4 1.1 2$C P H
Y e a r/D a y s3 6 5D a y/H r s2 4C P H
81
Calculating Operating Costs
Assume $0.10 /kWH Assume 92% Motor Efficiency Assume 90.5% Pump Efficiency Assume 1 Pump Assume 24 Hrs / Day Assume 365 Days / Yr Assume 60°F Water (s.g. = 1)
82
Calculating Operating Costs
DESIGN POINT: 3200GPM @ 160’TDH(PUMP “B”)
83
Calculating Operating Costs
≈ $102,054 / YEAR
1 0..7 4 6 9 2.09.3 9 6 0
11 6 02 0 03C P H
1 0.7 4 6.8 8.2 7 8,3
0 0 0,5 1 2C P H
6 5.1 1$C P H
Y e a r/D a y s3 6 5D a y/H r s2 4C P H
84
The Difference is Savings
The difference in PUMP EFFICIENCY between the 84.5% Efficient Pump “A” and the 90% Efficient Pump “B” Results in Real Operating Cost Savings
Pump “A” Operating Cost ≈ $108,711 / YearPump “B” Operating Cost ≈ $102,054 / Year
$Operating Cost Savings = $6,657 / Year
85
What Questions Do you Have?