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