Get documents about "Flow in Submersible Pumping Systems
Document Sample
Flow Repositioning
1
System Head Losses- Diagram
Dynamic Head Loss
Causes of Dynamic Head Losses- At Higher
Flow Parts of the System
Leak Detector
Valves
Piping Trunk
Piping Branches
Causes of Dynamic Head Losses- At Lower
Flow Parts of the System
Dispenser, meter
Breakaway
Filter
Hose
Nozzle
Swivels
Static Head Loss
Caused by the height a fluid must be
lifted from tank to nozzle
2
The Flow System - Resistance to Flow
Overview- Static Head in Flow Systems
• Pump and Motor in the tank create pressure to overcome resistances
to flow. The two types of resistances are “static head” and “dynamic
head”
Static Head
The effect of static head does not vary with the flow rate
• The height that a fluid must be lifted. This is the distance from the
product in the tank to the point of discharge into a car tank or
loading rack discharge point.
• In the submersible pumping system that distance is taken as
the worst case scenario of a nearly empty tank
• In bottom loading applications the highest point in the tanker
is taken as the point of discharge.
• The static head may vary with the tank level. The resulting
variation can make a difference of 7- 11 ft, or about 2-3psi in
the pressure of a pump.Usually the rest of the station
configuration will keep the static head requirement constant.
3
The Flow System - Resistance to Flow
Static Head in a Retail Fueling System
Point of discharge Static Head includes:
Product level to
the packer,
Bury depth
Grade Rise rise in grade to the
Actual Static Head
islands
Bury Depth
Height to discharge
point
Worst case Static Head Static Head
4
The Flow System - Resistance to Flow
Overview - Dynamic Head Resistance in Flow Systems
Dynamic Head-
What is Dynamic Head
• Dynamic Head is resistance to the movement of product from the tank to the nozzle caused by
fueling system components
• This resistance varies with the flow rate of the product through the component. The higher the
flow rate, the higher the resistance
• The relationship between the pressure and resulting flow is exponential and not proportional.
(twice the flow requires four times the pressure, not twice the pressure.)
• The resistance profile of each component causes a decrease in head or pressure as fluid passes
through that component. The pressure at the pump starts at a higher value and every component
the product passes through decreases the pressure at that point until the pressure is “0” at the
point of discharge.
• Total system resistances vary depending on the total flow passing through the component.
• Component resistances are additive and can be translated into a total pressure loss for the
system.
5
The Flow System - Resistance to Flow
Overview - Dynamic Head Resistance in Flow Systems
Dynamic Head
Components That Create Dynamic Flow Resistance in a Retail Fueling System-
Any component that has product flowing through it affects the total resistance or dynamic head of the system
• Piping-
• The trunk (closest piping to the submersible pump) has the highest flow rate
• The branches have less flow through them (only those nozzles and dispensers on that
line segment)
• Flexible Connectors
• Accessories:
• Leak Detectors
• Valves, such as check valves, ball valves
• In-line filters and screens
• Safety Valves
• Dispensers and “Hanging Hardware”
• Dispenser losses, including meter, filters
• Nozzles
• Hoses
• Breakaway fittings
• Swivels
• Usually about 2/3 of the resistance of a flow system is due to hanging hardware.
6
Dynamic Head Losses of Components
Head Loss of 1 ½ vs. 2 in Pipe per 100 ft
85 ft head loss
60 GPM
12 ft head loss
Notice that the head increases exponentially, not proportionally. Increasing the
pressure by a factor of 4 only increases the flow by a factor of 2. This is true for
all the components of the flow system that the product flows through.
Piping size is important in the areas of the piping system that have the potential
to carry the highest flows—generally near the pump.
7
Dynamic Head Losses of Components
Pressure vs. Flow for Encore Vapor Vac Dispensers with
Various Hanging Hardware
2/3 of the head loss at the island is
due to “Hanging Hardware– nozzles,
hoses breakaways
Total Dispenser and Hanging Hardware head loss
Dispenser Loss=
about 1/3 of pressure loss
Hanging hardware head loss=
about 2/3 of pressure loss
8
Pressure & Head Relationship
Pumps will pump
all fluids to a
maximum height at
no flow condition or
at called dead
head (in this
example—100 ft.).
Depending on the
fluid, even though
the height a pump
can push to is the
100 ft. 100 ft. 100 ft.
same, the pressure
at the pump is
different. Heavier
products, such as
diesel will exhibit a
higher pressure
than lighter
products such as
43 P.S.I 31 P.S.I 37 P.S.I
gasoline.
Water Gasoline Diesel
9
Pressure & Head Relationship
Converting Feet Head to PSI :
To convert the feet of head to pressure Divide 2.31 by S.G of the new fluid to get feet of
product per PSI for that fluid
• Example Calculations:
• Calculate the feet of product that exert 1 psi pressure of static head: Divide
2.31 by S.G to get feet of product per PSI.
• Gasoline: 2.31 ft per psi / .71 s.g=. 3.25 ft per psi
• Diesel: 2.31 / .85 s.g.= 2.72 ft per psi
• (remember water has a specific gravity of 1)
• Calculate the fluid pressure from head curves: Divide ft head from curve by
2.31 and multiply times S.G:
• Gasoline: (100 ft. /2.31)X 0.71=30.7 PSI
• Diesel: (100 ft /2.31)X0.85=36.8 PSI
Specific Gravity (S.G): Density of a product relative to water. Numbers less than 1.0 are fluids lighter than water.
Numbers over 1.0 are fluids heavier than water.
Water =1.0
Diesel =.82- .87( use average of 0.85)
Gasoline= .71
2.31 Ft depth of water=1 PSI for a fluid with a S.G of 1.0
Divide 2.31 by S.G of the new fluid to get feet of product per PSI for that fluid
10
The Flow System – Generating Flow
Overview – Universal Motor and Pump (UMP)
Motor
Pump
11
The Flow System – Generating Flow
Overview – Universal Motor and Pump (UMP)
Motors
• Motors can be fixed speed or variable speed and drive the pump
section of a UMP.
• Fixed speed motors run at a fixed rpm. Pumps attached to
them have one fixed output curve.
• Variable speed motors can be controlled to generate a
constant pressure output on the pumps they are attached to.
Pressure output varies with the desired output programmed
into the controller. The higher the rpm of the motor, the
higher the output pressure of the pump.
12
The Flow System – Generating Flow
Overview – Universal Motor and Pump (UMP)
Pumps
• Centrifugal pumps create pressure by accelerating fluid from the
center of a spinning impeller to the outer perimeter
• They may have several stages, each of which imparts increasing
pressure to the fluid being pumped comprising of the parts
below.
• Each stage typically has 3 parts:
• Impeller- is spun by the motor. Product enters at the central
“eye” and is accelerated to the perimeter – producing
pressure
• Diffuser- directs the fluid leaving the impeller to the center of
the pump, into the eye of the next stage’s impeller.
• Diffuser plate- With the diffuser, the diffuser plate encloses
the impeller, forming one stage.
13
The Flow System – Generating Flow
Overview – Universal Motor and Pump (UMP)
Impellers spins fluid outward,
accelerating it and creating
pressure
Fluid leaving the
Diffusers redirect product to the impeller into the
diffuser
eye of the next impeller
About 14-15 P.S.I. is created in
each stage in 60 hz pumps and
about 9-10 psi in 50 hz pumps
Direction impeller is turning
14
The Flow System – Generating Flow
Overview – Universal Motor and Pump (UMP)
Methods For Increasing Flow
Increase the speed – higher HP
motor
Increase the diameter
Increase the vane width
Methods for increasing the output
pressure of an impeller or pump Vane width
Increase the speed – higher
HP motor
Increase the diameter of the
impeller
Additional stages add Impeller
incremental output pressure to Diameter
the pump
15
STP - Pump Performance Curves
Pump performance curves typically show pressure in the form of
“HEAD”on the left Y axis and flow rate on the X bottom axis.
The head , or pressure on the Y axis represents the pressure at which
the pump can deliver the flow rate on th X axis.
16
STP - Pump Performance Curves
Example: Against a head (pressure) of 60 ft, a 1 ½ hp pump will deliver 58
gallons per minute
The pump cannot vary from this curve. When running, it supplies the flow it
can against the pressure it experiences in the flow system
60 ft head P150S1 Pump Curve
58 GPM
17
STP - Pump Performance Curves
The pump cannot vary from the flow curve –
Changes in upstream components to reduce frictional pressure
loss will improve overall system flow by reducing the amount of
pressure the pump must overcome to deliver flow at the nozzle
As the pressure requirement decreases, the amount of flow a
pump can deliver increases
The analogy is a garden hose that is throttled with a thumb. With a lot of
pressure against the hose, there is very little flow. As the pressure against
the hose is relaxed, the flow from the hose increases.
18
STP - Pump Performance Curves
Variable speed pumps
have multiple
programmable set
points for desired
output pressure.
They will follow the
chosen curve by
Constant output of chosen pressure slowing or speeding up
the motor to react to
the varying system flow
Point at which pump resistances.
cannot supply the
The pressure holds
required pressure
constant until the load
is too great for the
pump to maintain the
pressure.
19
STP - Pump Performance Curves
160
1 P150U1 and Manifolded P150U1 Pump Performance
2
140
3 4 5
6 ber
Num of Nozzles operating
7 8
120
9
10
100
12
TDH-Feet
80
14
60
Single Pump Flow Manifolded Pump Flow 16
40
20
0
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
60 GPM @ 60 ft FLO -G
W pm
120 GPM @ 60 ft
Manifolded Pump curves are Additive on the flow Axis (X axis)
Actual flow rate increase depends on the other system components
Adding manifolded pumps will not increase flow in an additive manner at the
nozzle due to the pressure loss created by other system components
20
The Static and Dynamic Losses in the Pump Flow Program
120
1 P150S1 with 8 nozzles running produces 68 GPM or 8.5 GPM per nozzle
2
100 3 4 5
6 ber
Num of Nozzles operating
7 8 Combined head loss curve
80
9
10
for 8 Nozzles operating
12
TDH-Feet
60
14
E
16
40 D
C
20 B
68 GPM A
0
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
FLOW-Gpm
A= Static head The equipment head losses are
B=Leak Detector loss additive to make up a total system
C=Piping Loss head loss curve.
D=Dispenser loss
E= Hanging Hardware loss
21
