Presentation on theme: "Preferred Utilities Manufacturing Corp"— Presentation transcript:
1Preferred Utilities Manufacturing Corp Fuel Oil Handling SystemsFuel System Design ConsiderationsPart 1Preferred Utilities Mfg. Corp.31-35 South Street • Danbury • CT
2Or Not So Common Knowledge A review of a few important basics We Hate to AssumeIs it Common Knowledge?OrNot So Common KnowledgeA review of a few important basics
3Pressure BasicsThe atmosphere (air) has weight that exerts a pressure which envelopes the earth. This pressure is known as atmospheric pressure, and its force at sea level, under normal conditions is pounds per square inch (psi), or 14.7 psi. As the altitude above sea level is increased, the atmospheric pressure decreases. Have you ever noticed that water boils at a lower temperature at a high elevation? This is due to the reduced pressure on the surface of the water. Although the potatoes are in boiling water, it will take them significantly longer to cook at the lower boiling temperature.NOTES:The “Pressure” on the surface of the Earth (at sea level)is 14.7 pounds/square inch (psi).
4More Pressure Basics14.7 psia = atmospheric or barometric pressure at sea levelBarometric is absolute pressure expressed as inches of mercury (Hg) Sea Level = in. Hg.Psig= gauge pressure (reads zero at sea level)Psia = gauge pressure + atmospheric pressure1 psi = in. Hg1 psi = in. waterNOTES:
5Head Pressure Attached to process Inches of Head The atmosphere (air) has weight that exerts a pressure which envelopes the earth. This pressure is known as atmospheric pressure, and its force at sea level, under normal conditions is pounds per square inch (psi), or 14.7 psi. As the altitude above sea level is increased, the atmospheric pressure decreases. Have you ever noticed that water boils at a lower temperature at a high elevation? This is due to the reduced pressure on the surface of the water. Although the potatoes are in boiling water, it will take them significantly longer to cook at the lower boiling temperature.NOTES:For Water 1 psi = 27.7 inches of “water column”No matter how wide or large.
6Specific Gravity and Head Pressure Specific Gravity of water is 1.0The Specific Gravity (SG) of any other fluid is a ratio comparison to water. Numbers below 1.0 mean the fluid is lighter than water. Numbers above 1.0 means heavier than water.The SG Of #2 oil is .876The Specific Gravity of mercury is
7Head Pressure Comparisons 1 PSI of Head Pressure equals:27.68 inches of water (SG = 1.0)2.036 inches of mercury (SG = )31.6 inches of #2 oil (SG = .876)2.31 feet of water2.60 feet of #2 oil
8The Rules of ThumbThe atmosphere (air) has weight that exerts a pressure which envelopes the earth. This pressure is known as atmospheric pressure, and its force at sea level, under normal conditions is pounds per square inch (psi), or 14.7 psi. As the altitude above sea level is increased, the atmospheric pressure decreases. Have you ever noticed that water boils at a lower temperature at a high elevation? This is due to the reduced pressure on the surface of the water. Although the potatoes are in boiling water, it will take them significantly longer to cook at the lower boiling temperature.NOTES:
9Pressure Scales and Gauges The atmosphere (air) has weight that exerts a pressure which envelopes the earth. This pressure is known as atmospheric pressure, and its force at sea level, under normal conditions is pounds per square inch (psi), or 14.7 psi. As the altitude above sea level is increased, the atmospheric pressure decreases. Have you ever noticed that water boils at a lower temperature at a high elevation? This is due to the reduced pressure on the surface of the water. Although the potatoes are in boiling water, it will take them significantly longer to cook at the lower boiling temperature.NOTES:All different names for the same thing, “Pressure”.
10Positive Displacement Pumps Most fuel handling systems use positive displacement pumps.For most practical purposes:Positive displacement pumps are self primingFlow stops when pump stopspump discharge flow is constant for a given rpmpressure is determined by downstream restrictionswhen discharge flow is blocked, something breaksmotor horsepower is proportional to pressureA safety relief valve with an unobstructed path to a tank is essential to prevent mechanical damage.Pump-motor combinations produce fixed flowsMotor HP will determine max capable pressurePositive Displacement Pumps are the pump of choice of Fuel Oil.Need the lifting and constant flow & self priming - (with a price)These pumps are constant flow (not pressure) machines.Seals leakage, shaft strength govern pump limitsMotor determines design pressure: LO-201 is 50 psi, LO-202 is100 psi same pump, different motor.We use IMO/Delaval, Viking and TutleTypical mechanical engineer sees 10 centrifical pumps for one positive displacement type
11Positive Displacement Pumps Spur Gear Pumps- (not that popular)two meshed spur gears, one driven, one idlingsuitable for high pressureInternal Gear Pumps - (most commonly used)two meshed gears, one driven, one idlingouter gear has internal teeth, inner spur gearabove 100 gets noisyScrew Pump - (best pump, very expensive)one driven and two idler screws pull oil throughSpur Gear <> 100 PsiInternal Gear < 100 psi too noisy above 100psi, most ecomical, 80% of appicationsScrew >< 100psi , IMO typeLO-10 - TutleLO-20 - Viking
12Spur Gear Pump more prone to wear, not as mech eff., noisy Volume pumpedIdlerDischargeSuctionTight fit prevents back flowDriven
13Internal Gear Pumps Discharge Suction Volume pumped Attached to shaft Oil FilmCresent Piece is stationary
14Screw Pump Twin rotor Screw Pump Three rotor Screw Pump Heavy oil suited, quite, more eff mechanicallyBalanced construction, no axial thrustIMO, etc. per specificationViking has pump curves in book, press/speed vs flowRPM 1150 on #6 to keep filmRPM 3450 for #2 to keep filmTwin rotor Screw PumpThree rotor Screw Pump
15Pump Slip Some oil does bypass the pump internals Typically less than 10% of pump displacementie: a 100 gpm pump must pump 110 to deliver 100 gpmHigher pressure produces greater slipLower viscosity produces greater slipAlways size pumps for the expected pressure and flow rateSize for worst caseFlow- size for min ViscosityPipe- size for max Viscosity100 GPM pump pumps 100 GPM to output, but actually pumps 110GPM,Light oils produce up to 20% slipSize pump for worst case sinario so we get desired pressure and flow:Size flow for min viscositySize inlet piping for max viscosity
18Designing a Fuel Oil Pumping System The Five Basic Steps in designing a fuel oil pumping system.Calculate the required flow rate.Estimate the maximum inlet suction pressure.Estimate the required discharge pressure.Choose a fuel oil pumping systemSelect the proper control strategy
19Step 1- Determine the Flow Rate Fuel Handling System DesignsFor E-Gen day tank systemsRate of use vs. duty cycle determines pump flowLength of time without power to the pump set determines tank sizeE-Gen sets – “RULE of THUMB” 7 GPH per 100kwE-Gen sets - “RULE of THUMB” Use a 4:1 ratio so the pump runs only 25% of time. (Strictly engineer’s preference. Some say 1.5 times the E-Gen usage is enough. Each application will be different.)For burner/boiler systemsSupply loops to multiple burners are usually piped series or parallel.Series loops: total burning rate plus the pumping rate of the last burner only.Parallel loops: total pumping rate of all burner pumps.
20Day Tank SystemsDay tanks are used when it is desired to provide a supply of oil with a gravity head to:small burners (10 to 50 gph, 100 bhp or smaller)diesel generatorsprotects pump seals on burner or engine pumpMultiple day tanks may be filled from one pump set.Day tanks are used when the burner or generator is a great distance from or above the main storage tank.For emergency generators, day tank provides a period of operation without power to the pump set.Oil in the day tank can be used for cooling generator components.Day tanks can be drained and refilled automatically if oil gets too hot for use.
21Day Tank Schematic Use an RBS, it’s expensive to dump oil on the roof A motorized ball valve will work better than a solenoid valve due to low dp across valve may leak and flood tank not in service.locating near tank will help prevent free-fall into tank and causing foamingkeep at max distance apartSome city codes limit the amount of oil that can be stored above ground level
22Generators with a Header System Header could be up 35 floors.200 ft = 76 psiPressure at pump will be 76 psi plus friction losses plus the head to reach the overflow line.Mount a RLS switch in the vent to shut off the pump.A header pressure switch will back up the RBSA BPV at the bottom of the return loop set at a pressure lower then the head will help prevent foaming in the tank.
23Example of a E-Gen Day Tank System Parameters:Generator is rated for 800 KW.The generator must be able to operate for 3 hours without power to the pump set.Use the recommended 4:1 run ratio.Requirements: Very BasicGenerator usage is 56 GPHMinimum day tank is 168 gallonsMinimum pump flow rate is 3.73 GPM (224 GPH)
24Example Continued Apply that information to the real world: The recommended day tank depends on how the E-Gen is using the oil.Local fire codes may limit the amount of storage above ground level.The day tank may have to be larger to act as a heat sink for hotter return oil from the generator.Spill containment size is based on local code requirements.The pump capacity should have a 20% margin of error.
25Burner/Boiler Systems Most burners have a supply and return line.Burner pumps will usually pump more oil than the burner will use.5 gph burner might pump 45 gph100 gph burner might pump 150 gphBurners may be piped as parallel or series loops.The oil pump set might provide atomizing pressure for the burner requiring high pressure loops (100 PSI)Or the pump set may just flood the suction of the burner pump requiring a low pressure loop (10 PSI).Flow numbers must come from the burner vendor. There are no rules of thumbAtomizing pressure refers to mechanical atomizationSeries loop is a low pressure loop - NYC schools must be low pressureParallel loop is a high pressure loop
26Burner Loop Piped in Series “Flooded Supply Loop”Return line must be piped to the bottom of the tank to prevent foaming, air entrainment and possible loss of prime during off cycles.All three burners are operating at 100% firing rate – 100 GPHTypical piping of Preferred Inject Aire Burners.
27Burner Loop Piped in Parallel “High or Low Pressure Loop”Use BPR toInsure min. PSI at Burner inlet
28Advantages of Series vs. Parallel With a series loop, pump flow is smallerIn a series loop if oil is heated, the heaters are smallerTraditional series loop is usually very low pressureParallel loop may operate at high pressuresfor pressure atomizing without burner pumpsuse a back pressure valve where the supply and return headers meet to keep pressure only on the supply headerFlooded series loops have less air problems.
29Determine the Pump Capacity Once the minimum flow capacity is determined, the actual pump capacity must be chosen.Allowances must be made for pump wear especially with high outlet pressures and low viscosity oil.Consider a safety factor to cover design approximations.“Rule of Thumb”- Once the actual flow requirement is determined, add a 25% margin of safety.Your not done yet! You still need to determine the system pressures.
30Step 2- Maximum Inlet Suction Atmospheric pressure (29.92" Hg)(14.7 PSIA) provides the force to get oil into the pump.Most pumps can produce a 26" Hg vacuumGood practice limits suction to a 15" vacuum or lessTypical design piping loss is 3" Hg or lessThis leaves 10" Hg for static lift with a 2” margin of safety.Pump must not be located more than 12 ft. above the bottom of the tank
31Determining Inlet Suction Determine gravity head in feet of oil.One foot of oil is approximately 0.78" Hg. This means a maximum lift of 12 ft to stay at 10”Hg or less.Determine loss through suction piping.convert fittings, valves, etc. to equivalent diametersadd total length of pipe to equivalent for fittingsadd loss through strainer and Anti-Syphon valvesIf the suction pressure calculation is too high, increase the pipe size or lower pump relative to the tank.
32Suction Piping Precautions If both pumps in a duplex set may be run together, use total flow in the calculationsFigure static lift from bottom of tankUse a 100% safety factor for strainer dropUse a 40 or 100 mesh strainer for #2 oilUse worst case viscosity in figuring loss
33Pressure Drop through Pipe Number 2 Fuel OilExample:250 GPH in a 1” pipe has a 1.0 PSI per100 ft of pipeAnd it’s not linear-Twice the flow triples the pressure drop.Flow, Gallons per hour
34Add Equivalent Lengths of Straight Pipe in Feet for Fittings and Valves Measure the straight pipe and add the below lengths to determine the total friction loss.Example using 1,2&3 inch pipe:Fitting 1 inch 2 inch 3 inchGate ValveGlobe Valve90 Deg. Elbow45 Deg. ElbowTee (straight thru)Tee (rt. Angle flow)180 Deg. ReturnChoose fittings and valves with the least pressure drop.
35Step 3- Estimate Discharge Pressure Pressure at the pump discharge is a sum of:pressure needed at point of use plus:total gravity head andpipe lossesGenerally, discharge piping is smaller than suction piping
36Miscellaneous Cautions Beware of entrained airlocate return and supply at opposite ends of tankPipe return line to bottom of tankAvoid high lifts and “traps”Allow for easy priming of pumpsProvide adequate vent linesProvide properly sized day tank overflow linesDesign the system so it can be tested regularlyProvide a means to remove oil from the day tank so pump cycle can be testedGenerator testing usually not often enough or long enough to provide pump cycle testing.
37Step 4- Choose a Fuel Oil Pumping Systems Pick pump-motor pair with next greater flow rateMotor HP based on PSI required (use the manufacturer’s pump curves for the correct combination)Pump based on required flow- confirm pump curve – PSI vs FlowDuplex and Triplex pumps share common suction and discharge pipingMost common is a duplex settwo 100% pumps, one for backupcontrol system can monitor flow, start lag pumpTriplex pump sets for large plantsthree 50% pumps allow for one sparetwo 100% “winter pumps” - one 50% “summer pump”
38Step 5- Select a Control Strategy What determines when the pump will start and stop?continuous operation is usual for burner pumpsintermittent operation for day tank systemsAre you sequencing for filling multiple day tanks?Do you have provision for automatic pump back-up?based on flow or pressure at pump dischargeflow switch is used where gravity head is constantWhat alarms do you need for a malfunction?Do you require automatic testing?What will cause a safety shutdown?
40Automatic Start-Stop of Pumps Burner loop pumps might automatically start with a gas changeovermake certain that the pumps are tested and primedmight start pumps at 25 degrees if changeover is at 20Burner loop pumps should run continuouslyCycling the main pumps with the burner is not recommendedenergy saved doesn’t pay for nuisance shutdowns on loss of primeOn generator header systems, the supply pumps start when a generator runsDay tank filling pumps will cycle on and off when a tank needs fuel
41Semi-Automatic Pump Set Starts and stops based on a remote demand.Designed for low cost applications.Could be relay logic for simplicity or a small PLC for flexibility.Usually used when there is a call for operation where the pump will stay on during the boiler or Egen operation.Very limited options.Will usually have a pump base leak switch to shut down the pumps.Lead pump fail back-up.Alternates Lead/Lag operation of pumps.
42Automatic Pump Set Plant Wide Controller Motor Starter Cabinet UL Labeled ControlOne (1) PWC-Cxxxxxx ControllerOne (1) "D" 120 VAC Discrete Input CardOne (1) "H" HOA-ROUT Relay Output BoardMotor Starter CabinetControl circuit transformer (if required)Alarm BellTwo magnetic motor starters with overload protectionTwo motor circuit breakers
43Automatic Pump Set Features Built In Run Time MetersBAS Modbus StandardBuilt In Tank GaugeAuto Pump Prime & Suction Line Integrity Checking based on day of weekAutomatic Alternation Based on Run hrsLarge 16 line x 40 character display200 Point Alarm and Event Summary with Time and Date Stamp
44Automatic Pump Set Features Advanced Communications ModemDial In from PCDial out to pagerWire Float and Analog Input BoardAccepts up to 8 tanks or discriminating sensorsBAS Discrete Signals for Leak, Overfill etcDrip Pan Leak SwitchDuplex StrainerDuplex Strainer DP Switch & Indicator
45Sample Alarms Failure of a pump to provide flow Failure of both pumps to provide flowLow level in a day tankHigh pressure in systemHigh level in a day tankLeak in a day tank or pump set containmentLeak in double wall pipingDirt buildup in strainers and filtersHigh oil temperature in the day tank
46What About Automatic Testing Will that pump set be ready when you need it the most?Start burner loop pumps daily for 10 minutesStart generator header pumps dailyCheck for proper flow or pressureAlarm on system failure for preemptive repair
47Pump Failure and Backup Operation The lead pump is call on for operation.Within 15 seconds all inputs must be proven or the lead pump will be considered failed.-Starter not tripped on overload or failed.-Flow switch or pressure switch proven.If the lead pump fails the lag pump will automatically start.If the lead pump starts and runs ok for a time beyond the first 15 seconds, a loss of any input will result in an immediate start (no timed delay) of the lag pump.If the lead pump can not keep up with the demand and the day tank reaches the low level float, the lag pump will start to assist the lead pump.
48Sample Shutdown Conditions Leak in piping (oil detected in the containment area)Day tank leak (oil in the containment basin)On multiple day tank applications, all day tanks must show a leak condition to stop pumps.Pump set leak (oil in the base pan)Low level in the main tankAll pumps failedSupply and return valves not properly aligned
49Control System Summary Different applications need different strategiesControl system is as important as the mechanical design of the systemCustom design to suit an application is the key to a reliable fuel systemPLC and PWC logic allows maximum flexibility and monitoring of many pointsSystem may be interfaces with a building management systemMake sure you know the complete scope of the system before you complete your design
50Preferred Utilities Manufacturing Corp 31-35 South Street • Danbury • CTT: (203) • F: (203)