Pressure Limiting Driver (PLD)
Discharge Pressure Control
Suction Pressure Control
June 9 2009
Mark Evans – Clarke Fire Protection Products
Justin Strousse – Clarke Fire Protection Products
Overview –
Discharge Pressure Control
• Causes
C
off System
S t
Over-Pressure
O
P
• NFPA 20 2003/2007 Approved
pp
Methods for
Controlling System Over-Pressure
• ‘Variable
Variable Speed Pressure Limiting Control’
Control Language
Defined in NFPA 20 2003/2007
• Graphs
G h reviewing
i i h
how V
Variable
i bl S
Speed
dD
Drivers
i
control
t l
system over-pressure
• Benefits of using Variable Speed Drivers
Causes of
System Over-Pressure
Over Pressure
• Variable
V i bl S
Suction
ti P
Pressure
• Pump
p Pressure Curve “Rise to Shutoff”
• Engine Speed Increase to Shutoff
– commonly referred to as “Droop”
Droop
Variable
Suction Pressure
• Systems are designed for a minimum supply pressure
when typically the water pressure is much higher.
• During a 24 hour period demand for water fluctuates.
• Over time new consumers, feeder branches and/or
water pumps are added or removed from the municipal
system.
• Regions which get water from mountain sources have
seasonal fluctuations.
Note: A fire can occur at anytime; not
necessarily at the design suction pressure.
Pump Curve
Pressure Rise to Shutoff
• Pumps are allowed to have up to 140% rise in pump
pressure from rated pressure
• The higher the rise in shut off pressure, the less
amount of horsepower is needed to obtain the rated
pressure
• The higher the rise in shut off pressure, the greater
the chance of over pressurizing the sprinkler system
system.
Speed Increase
to Shutoff
• When the load or horsepower demand is reduced on
either a Diesel Engine or an Electric Motor, the driver
speed increases.
• This increase in speed is known as “Slip” for an
Electric Motor and “Droop” for a Diesel Engine.
-NFPA 20 allows a 10% droop
droop.
• One of the Affinity Laws state that pump pressure
varies by the square of the speed. The increase in
rpm, due to reduced load at no-flow, could overpressurize the sprinkler system.
Note: At 1760 rpm, a 10% increase in
speed results in a 21% increase in pressure.
System Pressure
• Supply pressure is generally the highest at
pump
pp
pressure and engine
g
shut-off where the p
droop are the greatest. All 3 factors must be
taken into account to prevent over
pressurization.
pressurization
Controlling Sprinkler System
Over Pressure
Over-Pressure
•
NFPA 2003/2007 Approved Options:
1) Break Tank
Requirements-An automatic fill –
May reduce the overall reliability
-More floor space –
Adds significant cost to the installation.
Controlling Sprinkler System
Over Pressure
Over-Pressure
•
NFPA 2003/2007 Approved Options:
2) Ground Storage Tank
Requirements-Sized to meet the total fire flow requirement
Adds Significant cost to the installation
-Physical Space
May not have room on property
Controlling Sprinkler System
Over Pressure
Over-Pressure
•
NFPA 2003/2007 Approved Options:
3) Variable Speed Pressure Limiting Control
Requirements-Device on Engine
-Sensing Line
-Pressure Relief Valve
-Additional visible and audible alarm on the controller
Variable Speed Approved
2003/2007 Edition of NFPA 20
Variable Speed Definition
3.3.45 (2003) “Variable Speed Pressure Limiting Control
(VSPLC). A speed control system used to limit the total
discharge pressure by reducing the pump driver speed
from the rated speed
speed.”
3.3.55 (2007) “Variable Speed Pressure Limiting Control.
A speed
d control
t l system
t
used
d tto limit
li it th
the ttotal
t l di
discharge
h
pressure by reducing the pump driver speed from the
rated speed.”
Variable Speed Approved
2003/2007 Edition of NFPA 20
Variable Speed is recognized as a Solution
to system Over-pressure
5.7.4.3 (2003) “Variable Speed Pressure Limiting Control”
5.7.6.3 (2007) “Variable Speed Pressure Limiting Control”
5.7.4.3.1 (2003) “Variable speed pressure limiting control
drivers, as defined in this standard, are acceptable to meet
the requirements of 5.7.4.1”
5.7.6.3.1 (2007) “Variable speed pressure limiting control
drivers, as defined in this standard, are acceptable to limit
system
y
pressure.
p
Variable Speed Approved
2003/2007 Edition of NFPA 20
Variable Speed is recognized as a Solution
to system Over-pressure
5.7.4.1
5
7 4 1 (2003) “The
“Th nett pump shutoff
h t ff (churn)
( h ) pressure
plus the maximum static suction pressure, adjusted for
elevation,, shall not exceed the pressure
p
for which the
system components are rated.”
5.7.6.1
5
7 6 1 (2007) “The
The net pump shutoff (churn) pressure
plus the maximum static suction pressure, adjusted for
elevation, shall not exceed the pressure for which the
system
t
components
t are rated.”
t d”
Variable Speed Approved
2003/2007 Edition of NFPA 20
Pressure Relief Valves and System Over-pressure
Over pressure
5.7.4.2
5
7 4 2 (2003) “Pressure
Pressure relief valves shall not be used
as a means to meet the requirements of 5.7.4.1”
5.7.6.2
5
7 6 2 (2007) “Pressure
Pressure relief valves and pressure
regulating devices in the fire pump installation shall not
be used as a means to meet the requirements of
5.7.6.1”
Variable Speed Approved
2003/2007 Edition of NFPA 20
Pressure Relief Valves and System
y
Over-pressure
p
5.18.1.3 (2003) “Where a variable speed pressure
limiting control driver is installed
installed, a pressure relief valve
shall be installed.”
5.18.1.1
18 1 1 (2007)
(200 ) “Where
“Wh
a diesel
di
l engine
i fifire pump iis
installed and where a total of 121 percent of net rated
p
p
plus the maximum static suction
shutoff ((churn)) pressure
pressure, adjusted for elevation, exceeds the pressure
for which the system components are rated, a pressure
relief valve shall be installed
installed.
Variable Speed Approved
2003/2007 Edition of NFPA 20
Requirements for Variable Speed Pressure Limiting
11.2.4.2.3 (2003) “In the event of a failure of the
pressure limiting control system, the engine shall be fully
functional with the governor defined in 11.2.4.1.”
(Governor regulates
(G
l t the
th engine
i speed
d within
ithi a
10% range between shutoff and maximum load)
11.2.4.2.3
11
2 4 2 3 (2007) “In
In the event of a failure of the
pressure limiting control system, the engine shall be fully
functional with the governor defined in 11.2.4.1.”
Example
The next group of slides will show how variable
suction can affect the sprinkler system pressure
pressure.
The graphs are general examples. Specific jobsite
d t may vary from
data
f
this
thi example.
l
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
250
150
100
Pump Curve
50
2200
0
Pump Speed
2000
1800
1600
0
500
1000
1500
Flow (GPM)
2000
2500
Pump
p Speed (RPM)
Pressure (PSI))
200
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
w/ Design Suction Supply Pressure Curve and Discharge Pressure Curve
250
Discharge Pressure -
1 0
150
100
Pump Curve
Design Suction
Pressure Curve
50
2200
0
Pump Speed
2000
1800
1600
0
500
1000
1500
2000
Flow (GPM)
Sprinkler
p
System
y
is designed
g
for 1500 GPM @ 145 PSI
(125 PSI Pump + 20 PSI Suction = 145 PSI)
2500
Pump Speed (RP
PM)
Pressure (P
PSI)
200
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
w/ Max Suction Supply Pressure Curve and Discharge Pressure Curve
Discharge Pressure Max Suction Pressure
250
Pressure (PS
SI)
200
Pump
150
100
50
Max Suction
Pump
2000
1800
1600
0
500
1000
1500
2000
Flow (GPM)
Sprinkler System Pressure vs Flow with an additional
suction pressure variation of 55 PSI.
(This gives 75 PSI total suction pressure.)
2500
Pump Speed (RPM
P
M)
2200
0
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
Discharge Pressure Curves
250
Discharge Pressure Max Suction Pressure
150
100
Discharge Pressure Design Suction
S
Pressure
50
2200
0
Pump Speed
2000
1800
1600
0
500
1000
1500
Flow (GPM)
Discharge pressure curves based upon minimum
and maximum suction pressure at design flow
rate.
t Pressure
P
varies
i from
f
145 PSI tto 200 PSI
PSI.
2000
2500
Pump Speed (RPM
P
M)
Pressure (PS
SI)
200
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
Discharge Pressure Curves w/ 175 PSI System Pressure Limit
Discharge Pressure Max S
M
Suction
ti Pressure
P
250
Over Pressure Region
175 PSI Pressure Limit
150
100
Discharge Pressure Design Suction Pressure
50
2200
0
2000
Pump Speed
1800
1600
0
500
1000
1500
Flow (GPM)
Based upon a system designed for a 175 PSI max
working pressure, the yellow region shows the
system Over-Pressure region as suction
pressure increased from 20 PSI to 75 PSI.
2000
2500
Pump Speed (R
RPM)
Pressure (P
PSI)
200
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
Max Discharge Pressure Curve Up To 1500 GPM w/ PLD Off
Discharge Pressure Max Suction Pressure
w/ PLD Off
250
Pressure (P
PSI)
200
1 0
150
175 PSI Pressure Limit
100
50
Pump Speed
2200
2000
1800
1600
0
500
1000
1500
Flow (GPM)
Shows system pressure from 0 GPM to 1500 GPM.
This is the region of the system pressure that
exceeds the PLD set point of 175 PSI. This slide
shows normal system pressure vs flow and RPM
with the PLD turned ‘Off’.
2000
2500
Pump Speed (RP
PM)
0
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
System Performance 1200 - 1500 GPM w/ PLD On
Discharge Pressure Max S
M
Suction
ti Pressure
P
w/ PLD Off
250
Pressure (PS
SI)
200
150
175 PSI Pressure Limit
Discharge Pressure Max Suction Pressure
PLD On
100
50
Pump Speed PLD
Off
2200
2000
1800
Pump Speed PLD
On
1600
0
500
1000
1500
2000
Flow (GPM)
This slide shows the PLD at work. At 1500 GPM system pressure
begins to be “trimmed”
trimmed .
Note: Pump Speed vs Flow Curve the pump speed drops
to accomplish this pressure “trimming”.
2500
Pump Speed (RPM
P
M)
0
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
System Performance 900 - 1500 GPM w/ PLD On
Discharge Pressure Max Suction Pressure
w/ PLD Off
250
Pressure (P
PSI)
200
1 0
150
175 PSI Pressure Limit
Discharge Pressure Max Suction Pressure
PLD On
100
50
Pump Speed PLD
Off
2200
2000
1800
Pump Speed PLD
On
1600
0
500
1000
1500
Flow (GPM)
With the flow reducing to 900 GPM.
Note: The PLD continues “Trimming” pressure as
speed continues to reduce.
2000
2500
Pump Speed (RP
PM)
0
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
System Performance 600 - 1500 GPM w/ PLD On
Discharge Pressure Max S
M
Suction
ti Pressure
P
w/ PLD Off
250
Pressure (PS
SI)
200
150
175 PSI Pressure Limit
Discharge Pressure Max Suction Pressure
PLD On
100
50
Pump Speed PLD
Off
2200
2000
1800
Pump Speed PLD
On
1600
0
500
1000
1500
Flow (GPM)
With the flow reducing to 600 GPM.
Note: The PLD continues “Trimming” pressure as
speed continues to reduce.
2000
2500
Pump Speed (RPM
P
M)
0
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
System Performance 300 - 1500 GPM w/ PLD On
Discharge Pressure Max S
M
Suction
ti Pressure
P
w/ PLD Off
250
Pressure (PS
SI)
200
150
175 PSI Pressure Limit
Discharge Pressure Max Suction Pressure
PLD On
100
50
Pump Speed PLD
Off
2200
2000
1800
Pump Speed PLD
On
1600
0
500
1000
1500
Flow (GPM)
With the flow reducing to 300 GPM.
Note: Pressure “Trimming” is maintained by speed
reduction.
2000
2500
Pu
ump Speed (RPM))
0
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
System Performance Up To 1500 GPM w/ PLD On
Discharge Pressure Max Suction Pressure
w/ PLD Off
250
150
175 PSI Pressure Limit
Discharge Pressure Max Suction Pressure
PLD On
100
50
Pump Speed PLD
Off
0
2200
2000
1800
Pump Speed PLD
On
1600
0
500
1000
1500
Flow (GPM)
With flow now reduced to shut-off (0 GPM).
Note: Pressure “Trimming” and speed reduction
curves.
2000
2500
Pump Speed (RPM
P
M)
Pressure (PS
SI)
200
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
Complete System
Discharge Pressure Max Suction Pressure
w/ PLD Off
250
175 PSI Pressure Limit
Pressure (PS
SI)
200
150
Discharge Pressure Max Suction Pressure
PLD On
100
50
Pump Speed PLD
Off
2200
2000
1800
Pump Speed PLD
On
1600
0
500
1000
1500
Flow (GPM)
Previous slides show system pressure with VSD
with 75 PSI suction pressure at < rated GPM
GPM.
2000
2500
Pump Speed (RPM
P
M)
0
Typical System Performance W/ Pressure Limiting Driver (PLD)
Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM
Complete System
Discharge Pressure Max Suction Pressure
w/ PLD Off
250
Over Pressure Region
175 PSI Pressure Limit
150
100
Discharge Pressure Design Suction Pressure
50
Discharge Pressure Max Suction Pressure
PLD On
Pump Speed PLD
Off
0
2200
2000
1800
Pump Speed PLD
On
1600
0
500
1000
1500
Flow (GPM)
Control of over pressure depending upon suction
pressure.
2000
2500
Pump Speed (RPM
P
M)
Pressure (PS
SI)
200
PLD Benefits
• Pressure Limiting
g Drivers ((PLD)) will Prevent Sprinkler
p
System Over-Pressure due to:
• Variable Suction Pressure
• High Pump Shut-Off Pressure
• Engine Droop
PLD Benefits
• No device in the main supply
pp y line with p
potential
obstructions to the water flow.
• Saves design time by not having to review multiple
engine/pump combinations, to confirm shut off pressure
will NOT exceed the system pressure.
• Reduces quantity of pressure control valves on high
rise applications
pp
by
y capping
pp g the maximum p
pressure sent
to the sprinkler system.
PLD Benefits
• Enables yyou to use p
pumps
p with steeper
p shut off curves
requiring less horse power to potentially reduce the
engine/pump cost.
•Eliminate routine discharge of excess water during
weekly tests
Mechanical vs Electronic PLD
Discharge Control
• Mechanical Engine
g
– Pressure settings of 100, 170 or 240 psi
– Engine has droop
• Electronic Engine
– Factory Set any control pressure between 100 and 350
psi for precise pressure control
– Engine has 0% droop
– No water discharge from pressure sensing line during
operation
Pressure Limiting Driver
Applications
• Pumps
p using
g municipal
p water with a p
pressure rating
g of
125 psi or higher.
• Facilities that requires 2 sources of water.
• One pump used for multiple buildings.
• A large pressure difference between the static suction
pressure and residual suction pressure.
Electronic Pressure Limiting
Driver Applications
•High
g Rise Applicationpp
• Capable of 350 psi allowing the engine to protect
the maximum rating of the riser
riser.
• Reduce the amount of pressure reducing valves on
th upper floors
the
fl
off a building.
b ildi
p
calculated
• Can be Factoryy Set to a specific
pressure to allow for 100 psi on the roof while
preventing system over pressure.
Electronic Pressure Limiting
Driver Applications
•Replacement
p
Pump
p Sets
• Protect Underground Loop.
• Protect older sprinkler systems by using the engine
to reduce the maximum pressure.
Summary –
PLD Discharge Control
• Pressure Relief Valves are no longer
g allowed to be
used to control sprinkler system over-pressure.
• The PLD is an effective way of controlling system over
overpressure by reducing the rpm of the driver according to
the 2003/2007 NFPA 20 regulations.
Overview –
Suction Pressure Control
• Causes of Suction Under-Pressure
• ‘Variable Speed Suction Limiting Control’ Language
Defined in NFPA 20 (2010 Draft)
• Graphs reviewing how Pressure Limiting Drivers
control
t l suction
ti under-pressure
d
Need for Suction
Pressure Control
• Local water companies
p
typically
yp
y require
q
a minimum
suction pressure to be maintained.
Causes of Suction
Under Pressure
Under-Pressure
• During
g a 24 hour p
period demand for water fluctuates.
• Over time new consumers, feeder branches and/or water
pumps are added or removed from the municipal system.
• Regions which get water from mountain sources have
seasonal fluctuations
fluctuations.
• Excessive water demand beyond 150% of rated flow or
demand beyond design point
point.
Suction Variable Speed Draft
2010 Edition NFPA 20
• 3.3 General Definitions ((2007))
• NFPA 20 par. 3.3 “Variable Speed Suction Limiting
Control A speed control system used to maintain a
Control.
minimum positive suction pressure at the pump inlet by
reducing the pump driver speed while monitoring
pressure in
i th
the suction
ti piping
i i th
through
h a sensing
i liline.””
Suction Variable Speed Draft
2010 Edition NFPA 20
• 5.15.9 Low Suction Throttling
g Valves ((2007))
• NFPA 20 par. 5.15.9.1 “Low suction throttling valves or
variable speed suction limiting controls for pump driver
that are listed for fire pump service and that are suction
pressure sensitive shall be permitted where the authority
having jurisdiction requires positive pressure to be
maintained on the suction piping.”
Suction Variable Speed Draft
2010 Edition NFPA 20
• 5.14.9 Devices in Suction Piping
p g ((2007))
• NFPA 20 par. 5.14.9.2 (2) “Where the authority having
jurisdiction requires positive pressure to be maintained
on the suction piping, a pressure-sensing line for low
suction pressure control, specifically listed for fire pump
service,
i
shall
h ll b
be permitted
itt d tto b
be connected
t d tto th
the
suction piping.”
Example
The next group of slides will show how variable
suction can affect the sprinkler system pressure
pressure.
The graphs are general examples.
S
Specific
ifi jjobsite
b it d
data
t may vary ffrom thi
this example.
l
Suction Pressure Limiting Device
For
Typical 1500 GPM Horizontal Split Case Pump System Performance
System Design Point
250
Sprinkler System Pressure - 2100 RPM Rated Speed
2370 GPM M
Max Fl
Flow R
Rate
t att
20 PSI Minimum Suction Pressure
200
Design Point
Pump
100
Typical
System
Curve
Minimum Design Suction
Supply Pressure
50
0
20 PSI Minimum Suction
Pressure Set Point
2000
2100 RPM
Rated Speed
1500
1000
0
500
1000
1500
2000
2500
Flow
System flow design point 1500 GPM at 175 PSI
Typical warehouse with 45 ft elevation to the sprinkler grid.
Water company requires 20 PSI minimum suction pressure.
Pump Speed (RP
P
PM)
Pre
essure (PSI)
150
Suction Pressure Limiting Device
For
Typical 1500 GPM Horizontal Split Case Pump System Performance
Flow Increases
250
Sprinkler
p
System
y
Pressure - 2100 RPM Rated Speed
p
2370 GPM M
Max Fl
Flow R
Rate
t att
20 PSI Minimum Suction Pressure
200
Minimum Design
Suction Supply
Pressure
100
Operating Point
20 PSI Minimum Suction
Pressure Set Point
50
0
2000
2100 RPM
Rated Speed
1500
1000
0
500
1000
1500
2000
2500
Flow
System flow 2370 GPM at 120 PSI at 20 PSI minimum suction
pressure as additional sprinkler heads open
open.
Minimum suction pressure could occur under
150% of rated flow.
Pump Speed (RP
P
PM)
Pre
essure (PSI)
150
Suction Pressure Limiting Device
For
Typical 1500 GPM Horizontal Split Case Pump System Performance
Engine Speed Reduced To Maintain Minimum Suction Pressure
250
Sprinkler System Pressure - 2100 RPM Rated Speed
2370 GPM M
Max Fl
Flow R
Rate
t att
20 PSI Minimum Suction Pressure
200
PLD On
Minimum Design
Suction Supply
Pressure
100
PLD Off
1900 RPM
Operating Point
50
Suction
Pressure Below
Set Point
20 PSI Minimum Suction
0
2000
1900 RPM
2100 RPM
Rated Speed
1500
1000
0
500
1000
1500
2000
2500
Flow
As additional sprinkler heads open, suction pressure tries to
reduce below 20 PSI
PSI, but engine speed is reduced to 1900 rpm to
maintain 20 PSI suction pressure.
Flow is maintained at 2370 GPM at 100 PSI.
Pump Speed (RP
P
PM)
Pre
essure (PSI)
150
Suction Pressure Limiting Device
For
Typical 1500 GPM Horizontal Split Case Pump System Performance
Engine Speed Reduced To Maintain Minimum Suction Pressure
250
Sprinkler System Pressure - 2100 RPM Rated Speed
2370 GPM M
Max Fl
Flow R
Rate
t att
20 PSI Minimum Suction Pressure
200
PLD On
Minimum Design
Suction Supply
Pressure
100
PLD Off
1900 RPM
1700 RPM
Operating Point
20 PSI Minimum Suction
Pressure Set Point
50
Suction
Pressure Below
Set Point
0
2000
1900 RPM
2100 RPM
Rated Speed
1700 RPM
1500
1000
0
500
1000
1500
2000
2500
Flow
As additional sprinkler heads open, suction pressure tries to
reduce below 20 PSI
PSI, but engine speed is reduced to 1700 rpm to
maintain 20 PSI suction pressure.
Flow is maintained at 2370 GPM at 90 PSI.
Pump Speed (RP
P
PM)
Pre
essure (PSI)
150
Suction Pressure Limiting Device
For
Typical 1500 GPM Horizontal Split Case Pump System Performance
Engine Speed Reduces To Maintain Minimum Suction Pressure
250
Sprinkler System Pressure - 2100 RPM Rated Speed
2370 GPM M
Max Fl
Flow R
Rate
t att
20 PSI Minimum Suction Pressure
200
PLD On
Minimum
Mi
i
D
Design
i
Suction Supply
Pressure
100
PLD Off
1900 RPM
1700 RPM
1500 RPM
Operating Point
20 PSI Minimum Suction
Pressure Set Point
50
Suction
Pressure Below
Set Point
0
2000
1900 RPM
2100 RPM
Rated Speed
1700 RPM
1500
1500 RPM
1000
0
500
1000
1500
2000
2500
Flow
As additional sprinkler heads open, suction pressure tries to
reduce below 20 PSI
PSI, but engine speed is reduced to 1500 rpm to
maintain 20 PSI suction pressure.
Flow is maintained at 2370 GPM at 73 PSI.
Pump Speed (RP
P
PM)
Pre
essure (PSI)
150
Suction Pressure Limiting Device
For
Typical 1500 GPM Horizontal Split Case Pump System Performance
Engine Speed Reduces To Maintain Minimum Suction Pressure
250
Sprinkler
p
System
y
Pressure - 2100 RPM Rated Speed
p
2370 GPM Max Flow Rate at
20 PSI Minimum Suction Pressure
200
PLD On
Minimum Design
Suction Supply
Pressure
100
PLD Off
1900 RPM
1700 RPM
1500 RPM
1300 RPM
20 PSI Minimum Suction
Pressure Set
S Point
50
Suction
Pressure Below
Set Point
Operating
p
g Point
0
2000
1900 RPM
2100 RPM
Rated Speed
1700 RPM
1500
1500 RPM
1300 RPM
Minimum Speed
1000
0
500
1000
1500
2000
2500
Flow
As additional sprinkler heads open, suction pressure tries to
reduce
d
b
below
l
20 PSI
PSI, but
b t engine
i speed
d is
i reduced
d
d tto 1300 rpm tto
maintain 20 PSI suction pressure.
Flow is maintained at 2370 GPM at 60 PSI.
Pump Speed (RPM
M)
Pre
essure (PSI)
150
PLD Suction Calculator
• Will be available on the www.Clarkefire.com web
site.
• Produce a curve showing minimum discharge
pressure, maximum flow rate, based upon the
minimum suction pressure.
PLD Benefits
•
Reduces water flow to maintain minimum suction
pressure so water is available to the sprinkler
system.
•
No valve in-line with water supply.
•
S
Substitute
ffor break tank. More economical.
•
Designed
g
to p
protect water supply
pp y when the number
of open sprinkler heads exceed the design criteria.
Summary –
PLD Suction Control
•
PLD and suction control valve both control p
pressure
while maintaining the same flow.
•
PLD send a signal to diesel controller if minimum
pressure (rpm) is obtained.
• Added Benefit
f – Both Discharge control and Suction
S
control can be provided on one engine.
VSD Benefits
Thank You