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 of System Over-Pressure NFPA 20 2003/2007 Approved Methods for Controlling System Over-Pressure Variable Speed Pressure Limiting Control Language Defined in NFPA 20 2003/2007 Graphs reviewing i how Variable Speed Drivers control system over-pressure Benefits of using Variable Speed Drivers
Causes of System Over-Pressure Variable Suction Pressure Pump Pressure Curve Rise to Shutoff Engine Speed Increase to Shutoff commonly referred to as 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.
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. 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 shut-off where the pump p pressure and engine droop are the greatest. All 3 factors must be taken into account to prevent over pressurization.
Controlling Sprinkler System 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 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 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. 3.3.55 (2007) Variable Speed Pressure Limiting Control. A speed control system used to limit it the total t discharge 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 pressure.
Variable Speed Approved 2003/2007 Edition of NFPA 20 Variable Speed is recognized as a Solution to system Over-pressure 5741(2003) 5.7.4.1 The net pump shutoff (churn) pressure plus the maximum static suction pressure, adjusted for elevation, shall not exceed the pressure for which the system components are rated. 5761(2007) 5.7.6.1 The net pump shutoff (churn) pressure plus the maximum static suction pressure, adjusted for elevation, shall not exceed the pressure for which the system components are rated.
Variable Speed Approved 2003/2007 Edition of NFPA 20 Pressure Relief Valves and System Over-pressure 5742(2003) 5.7.4.2 Pressure relief valves shall not be used as a means to meet the requirements of 5.7.4.1 5762(2007) Pressure relief valves and pressure 5.7.6.2 (2007) 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 Over-pressure 5.18.1.3 (2003) Where a variable speed pressure limiting control driver is installed, a pressure relief valve shall be installed. 5.18.1.1 1811(200 (2007) Where a diesel engine fire pump is installed and where a total of 121 percent of net rated shutoff (churn) pressure plus the maximum static suction pressure, adjusted for elevation, exceeds the pressure for which the system components are rated, a pressure relief valve shall be 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 the engine speed within a 10% range between shutoff and maximum load) 112423(2007) In the event of a failure of the 11.2.4.2.3 (2007) 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. The graphs are general examples. Specific jobsite data may vary from this example.
Typical System Performance W/ Pressure Limiting Driver (PLD) Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM 250 200 ) Pressure (PSI) 150 100 Pump Curve 50 0 2200 Pump Speed 2000 1800 1600 0 500 1000 1500 2000 2500 Flow (GPM) Pump Speed (RPM)
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 250 200 Discharge Pressure - Pressure (P PSI) 150 100 50 Pump Curve Design Suction Pressure Curve 0 2200 Pump Speed 0 500 1000 1500 2000 2500 Flow (GPM) 2000 1800 1600 Pump Speed (RP PM) Sprinkler System is designed for 1500 GPM @ 145 PSI (125 PSI Pump + 20 PSI Suction = 145 PSI)
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 250 Discharge Pressure - Max Suction Pressure 200 Pressure (PS SI) 150 100 Pump 50 0 Max Suction 2200 Pump 0 500 1000 1500 2000 2500 Flow (GPM) 2000 1800 1600 Pump Speed (RPM M) Sprinkler System Pressure vs Flow with an additional suction pressure variation of 55 PSI. (This gives 75 PSI total suction pressure.)
Typical System Performance W/ Pressure Limiting Driver (PLD) Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM Discharge Pressure Curves 250 200 Discharge Pressure - Max Suction Pressure Pressure (PS SI) 150 100 50 Discharge Pressure - Design Suction Pressure 0 2200 Discharge pressure curves based upon minimum and maximum suction pressure at design flow rate. Pressure varies from 145 PSI to 200 PSI. Pump Speed 0 500 1000 1500 2000 2500 Flow (GPM) 2000 1800 1600 Pump Speed (RPM M)
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 250 Discharge Pressure - Max Suction Pressure 200 Over Pressure Region 175 PSI Pressure Limit Pressure (P PSI) 150 100 Discharge Pressure - Design Suction Pressure 50 0 2200 Pump Speed 2000 1800 1600 0 500 1000 1500 2000 2500 Flow (GPM) Pump Speed (R RPM) 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.
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 - 250 Max Suction Pressure w/ PLD Off 200 Pressure (P PSI) 150 100 175 PSI Pressure Limit 50 0 Pump Speed 2200 0 500 1000 1500 2000 2500 Flow (GPM) 2000 1800 1600 Pump Speed (RP PM) 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.
Typical System Performance W/ Pressure Limiting Driver (PLD) Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM System Performance 1200-1500 GPM w/ PLD On 250 Discharge Pressure - Max Suction Pressure w/ PLD Off 200 Pressure (PS SI) 150 100 Discharge Pressure - Max Suction Pressure PLD On 175 PSI Pressure Limit 50 0 Pump Speed PLD Off 2200 Pump Speed PLD On 0 500 1000 1500 2000 2500 Flow (GPM) This slide shows the PLD at work. At 1500 GPM system pressure begins to be trimmed. Note: Pump Speed vs Flow Curve the pump speed drops to accomplish this pressure trimming. 2000 1800 1600 Pump Speed (RPM M)
Typical System Performance W/ Pressure Limiting Driver (PLD) Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM System Performance 900-1500 GPM w/ PLD On 250 Discharge Pressure - Max Suction Pressure w/ PLD Off 200 Pressure (P PSI) 150 100 Discharge Pressure - Max Suction Pressure PLD On 175 PSI Pressure Limit 50 0 Pump Speed PLD Off 2200 Pump Speed PLD On 0 500 1000 1500 2000 2500 Flow (GPM) 2000 1800 1600 Pump Speed (RP PM) With the flow reducing to 900 GPM. Note: The PLD continues Trimming pressure as speed continues to reduce.
Typical System Performance W/ Pressure Limiting Driver (PLD) Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM System Performance 600-1500 GPM w/ PLD On 250 Discharge Pressure - Max Suction Pressure w/ PLD Off 200 Pressure (PS SI) 150 100 Discharge Pressure - Max Suction Pressure PLD On 175 PSI Pressure Limit 50 0 Pump Speed PLD Off 2200 Pump Speed PLD On 0 500 1000 1500 2000 2500 Flow (GPM) 2000 1800 1600 Pump Speed (RPM M) With the flow reducing to 600 GPM. Note: The PLD continues Trimming pressure as speed continues to reduce.
Typical System Performance W/ Pressure Limiting Driver (PLD) Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM System Performance 300-1500 GPM w/ PLD On 250 Discharge Pressure - Max Suction Pressure w/ PLD Off 200 Pressure (PS SI) 150 100 Discharge Pressure - Max Suction Pressure PLD On 175 PSI Pressure Limit 50 0 Pump Speed PLD Off 2200 Pump Speed PLD On 0 500 1000 1500 2000 2500 Flow (GPM) With the flow reducing to 300 GPM. Note: Pressure Trimming is maintained by speed reduction. 2000 1800 1600 ) Pu ump Speed (RPM)
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 250 Discharge Pressure - Max Suction Pressure w/ PLD Off 200 Pressure (PS SI) 150 100 Discharge Pressure - Max Suction Pressure PLD On 175 PSI Pressure Limit 50 0 Pump Speed PLD Off 2200 Pump Speed PLD On 0 500 1000 1500 2000 2500 Flow (GPM) 2000 1800 1600 Pump Speed (RPM M) With flow now reduced to shut-off (0 GPM). Note: Pressure Trimming and speed reduction curves.
Typical System Performance W/ Pressure Limiting Driver (PLD) Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM Complete System 250 Discharge Pressure - Max Suction Pressure w/ PLD Off 200 175 PSI Pressure Limit Pressure (PS SI) 150 100 Discharge Pressure - Max Suction Pressure PLD On 50 0 Pump Speed PLD Off 2200 Pump Speed PLD On 0 500 1000 1500 2000 2500 Flow (GPM) 2000 1800 1600 Pump Speed (RPM M) Previous slides show system pressure with VSD with 75 PSI suction pressure at < rated GPM.
Typical System Performance W/ Pressure Limiting Driver (PLD) Typical Pump Performance - 1500 GPM, 125PSI, 2100 RPM Complete System 250 Discharge Pressure - Max Suction Pressure w/ PLD Off 200 Over Pressure Region 175 PSI Pressure Limit Pressure (PS SI) 150 100 50 Discharge Pressure - Design Suction Pressure Discharge Pressure - Max Suction Pressure PLD On 0 Pump Speed PLD Off 2200 Pump Speed PLD On 0 500 1000 1500 2000 2500 Flow (GPM) 2000 1800 1600 Pump Speed (RPM M) Control of over pressure depending upon suction pressure.
PLD Benefits Pressure Limiting Drivers (PLD) will Prevent Sprinkler System Over-Pressure due to: Variable Suction Pressure Variable Suction Pressure High Pump Shut-Off Pressure Engine Droop
PLD Benefits No device in the main supply line with 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 by capping the maximum pressure sent to the sprinkler system.
PLD Benefits Enables you to use pumps p with steeper 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 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 using municipal water with a pressure rating 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 A large pressure difference between the static suction pressure and residual suction pressure.
Electronic Pressure Limiting Driver Applications High g Rise Application- Capable of 350 psi allowing the engine to protect the maximum rating of the riser. Reduce the amount of pressure reducing valves on the upper floors of a building. Can be Factory Set to a specific calculated pressure to allow for 100 psi on the roof while preventing system over pressure.
Electronic Pressure Limiting Driver Applications Replacement p Pump 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 allowed to be used to control sprinkler system over-pressure. The PLD is an effective way of controlling system over The PLD is an effective way of controlling system 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 suction under-pressure
Need for Suction Pressure Control Local water companies typically y require a minimum suction pressure to be maintained.
Causes of Suction Under-Pressure 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. Excessive water demand beyond 150% of rated flow or demand beyond design 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 minimum positive suction pressure at the pump inlet by reducing the pump driver speed while monitoring pressure in the suction piping i through h a sensing line.
Suction Variable Speed Draft 2010 Edition NFPA 20 5.15.9 Low Suction Throttling 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 (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, shall be permitted to be connected to the suction piping.
Example The next group of slides will show how variable suction can affect the sprinkler system pressure. The graphs are general examples. Specific jobsite data may vary from this example.
250 200 Sprinkler System Pressure - 2100 RPM Rated Speed Suction Pressure Limiting Device For Typical 1500 GPM Horizontal Split Case Pump System Performance System Design Point 2370 GPM Max Flow Rate at 20 PSI Minimum Suction Pressure 150 Design Point Pre essure (PSI) Typical Pump System 100 Curve Minimum Design Suction Supply Pressure 50 0 20 PSI Minimum Suction Pressure Set Point 2100 RPM Rated Speed 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. 2000 1500 1000 Pump Speed (RP PM)
250 200 Sprinkler System Pressure - 2100 RPM Rated Speed Suction Pressure Limiting Device For Typical 1500 GPM Horizontal Split Case Pump System Performance Flow Increases 2370 GPM Max Flow Rate at 20 PSI Minimum Suction Pressure 150 Pre essure (PSI) 100 50 20 PSI Minimum Suction Pressure Set Point Minimum Design Suction Supply Pressure Operating Point 0 2100 RPM Rated Speed 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. Minimum suction pressure could occur under 150% of rated flow. 2000 1500 1000 Pump Speed (RP PM)
250 200 Sprinkler System Pressure - 2100 RPM Rated Speed Suction Pressure Limiting Device For Typical 1500 GPM Horizontal Split Case Pump System Performance Engine Speed Reduced To Maintain Minimum Suction Pressure 2370 GPM Max Flow Rate at 20 PSI Minimum Suction Pressure 150 PLD On Pre essure (PSI) 100 50 20 PSI Minimum Suction Minimum Design Suction Supply Pressure 1900 RPM Operating Point Suction Pressure Below Set Point PLD Off 0 2100 RPM Rated Speed 0 500 1000 1500 2000 2500 Flow As additional sprinkler heads open, suction pressure tries to reduce below 20 PSI, but engine speed is reduced to 1900 rpm to maintain 20 PSI suction pressure. Flow is maintained at 2370 GPM at 100 PSI. 1900 RPM 2000 1500 1000 Pump Speed (RP PM)
250 200 Sprinkler System Pressure - 2100 RPM Rated Speed Suction Pressure Limiting Device For Typical 1500 GPM Horizontal Split Case Pump System Performance Engine Speed Reduced To Maintain Minimum Suction Pressure 2370 GPM Max Flow Rate at 20 PSI Minimum Suction Pressure 150 PLD On Pre essure (PSI) 100 50 20 PSI Minimum Suction Pressure Set Point Minimum Design Suction Supply Pressure 1900 RPM 1700 RPM Operating Point Suction Pressure Below Set Point PLD Off 0 2100 RPM Rated Speed 0 500 1000 1500 2000 2500 Flow As additional sprinkler heads open, suction pressure tries to reduce below 20 PSI, but engine speed is reduced to 1700 rpm to maintain 20 PSI suction pressure. Flow is maintained at 2370 GPM at 90 PSI. 1900 RPM 1700 RPM 2000 1500 1000 Pump Speed (RP PM)
250 200 Sprinkler System Pressure - 2100 RPM Rated Speed Suction Pressure Limiting Device For Typical 1500 GPM Horizontal Split Case Pump System Performance Engine Speed Reduces To Maintain Minimum Suction Pressure 2370 GPM Max Flow Rate at 20 PSI Minimum Suction Pressure 150 PLD On Pre essure (PSI) 100 50 20 PSI Minimum Suction Pressure Set Point Minimum i Design Suction Supply Pressure 1900 RPM 1700 RPM 1500 RPM Operating Point Suction Pressure Below Set Point PLD Off 0 2100 RPM Rated Speed 0 500 1000 1500 2000 2500 Flow As additional sprinkler heads open, suction pressure tries to reduce below 20 PSI, but engine speed is reduced to 1500 rpm to maintain 20 PSI suction pressure. Flow is maintained at 2370 GPM at 73 PSI. 1900 RPM 1700 RPM 1500 RPM 2000 1500 1000 Pump Speed (RP PM)
250 200 Sprinkler System Pressure - 2100 RPM Rated Speed Suction Pressure Limiting Device For Typical 1500 GPM Horizontal Split Case Pump System Performance Engine Speed Reduces To Maintain Minimum Suction Pressure 2370 GPM Max Flow Rate at 20 PSI Minimum Suction Pressure Pre essure (PSI) 150 100 50 20 PSI Minimum Suction Pressure Set Point Minimum Design Suction Supply Pressure 1900 RPM 1700 RPM 1500 RPM 1300 RPM Operating Point Suction Pressure Below Set Point PLD On PLD Off 0 2100 RPM Rated Speed 1900 RPM 1700 RPM 1500 RPM 1300 RPM Minimum Speed 0 500 1000 1500 2000 2500 Flow As additional sprinkler heads open, suction pressure tries to reduce below 20 PSI, but engine speed is reduced d to 1300 rpm to maintain 20 PSI suction pressure. Flow is maintained at 2370 GPM at 60 PSI. 2000 1500 1000 ump Speed (RPM M) P
PLD Suction Calculator Will be available on the www.clarkefire.com web site. Produce a curve showing minimum discharge 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. Substitute for break tank. More economical. Designed to protect water supply when the number g p ppy of open sprinkler heads exceed the design criteria.
Summary PLD Suction Control PLD and suction control valve both control pressure while maintaining the same flow. PLD send a signal to diesel controller if minimum pressure (rpm) is obtained. Added Benefit Both Discharge control and Suction control can be provided on one engine.
VSD Benefits
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