2 METERING PUMP DEFINITION Convey (like any pump)Measure (repeated displacement of defined volume)AdjustVolume per displacementFrequency of displacementsConveyAdjustMeasure
3 METERING PHILOSOPHYThink of the pump as a continuous fluid measurement deviceConverts batch processes (fluid measured, then mixed), to in-line processes (fluids continuously measured and mixed)
4 What is a Metering Pump? Hydraulic Institute Definition: “A controlled volume pump (also called a “metering”, “proportioning” or “chemical injection pump”) is a reciprocating power pump used to accurately displace a predetermined volume of liquid in a specified time period and is driven by power from an outside source applied to the pump mechanism. It includes a mechanism for varying the effective plunger, piston or diaphragm displacement.”Some Pump Manufacturers Add:“It includes a mechanism for varying the effective frequency of displacements.”ProMinent Fluid Controls
5 What claims to be a Metering Pump, but isn’t? Gear PumpDisplacement per revolution not adjustable. Not linear from high to low RPMs due to slip at low speed.Air OperatedDiaphragm PumpDisplacement per stroke not adjustable. Not repeatable due to variable air pressure, flexible diaphragm.ProgressingCavity PumpDisplacement per revolution not adjustable. Chemical incompatibility common w/ rotor.Displacement per revolution not adjustable. Tube stretch prevents repeatability.PeristalticPumpProMinent Fluid Controls
7 Metering Pump System Hydraulics and Application of Accessories The metering pump system design, the fluid pumped, and the accessories installed all play a vital role in system safety, repeatability and reliability.Key Concept: Metering Pump SystemProMinent Fluid Controls
8 Suction Head Negative Suction Head (suction lift) Positive Suction Head(flooded suction)ProMinent Fluid Controls
9 Suction LiftAtmospheric pressure always pushes down on any fluid surface. When the pump diaphragm creates a negative pressure in the pump head, atmospheric pressure forces fluid up the suction tube to fill the cavity.Atmospheric pressure at 500 feet above sea level = 14.5 psia = 1 bar = 34 feet of waterIf the pump pulled a perfect vacuum, the maximum suction lift possible on earth, pumping water, is 34 feet.14.5 psiaProMinent Fluid Controls
10 What happens if the tank is not vented (open to atmosphere)? Suction LiftWhat happens if the tank is not vented (open to atmosphere)?14.5 psia14.5 psia14.5 psiaProMinent Fluid Controls
11 Specific GravitySpecific Gravity is the fluid’s density in relation to the density of water (S.G. 1.0). For example:Sulfuric acid density = lbs/gal Therefore:Water density = lbs/gal S.G. = 1.84Ammonia density = lbs/gal ThereforeWater density = lbs/gal S.G. = 0.63Because atmospheric pressure forces fluid into the pump head during the suction stroke, if the fluid has a specific gravity greater than 1.0, the suction lift ability will be reduced.Specific gravity is independent of viscosity, and does not impact pump capacity, only suction lift capability.ProMinent Fluid Controls
12 Specific Gravity Impact on Suction Lift Actual Suction Lift =Rated Suction Lift (water) / S.G.Rated Suction Lift for VAMb04120 = 6.6 feetApplication: Chromic Acid (1.4 SG)Actual Suction Lift = 6.6 / 1.4 = 4.7’ProMinent Fluid Controls
13 Viscosity Viscosity is a measure of a fluid’s resistance to flow. Viscosities greater than that of water increase friction loss and result in reduced pump capacity.When selecting a pump for viscous fluids:Oversize the pumpPut springs in the valves to help seat the ballsUse high viscosity solenoid pumpsReduce stroking rate to minimum possibleKeep stroke length as great as possibleProvide flooded suction with oversized suction lineProMinent Fluid Controls
14 Specific Gravity and Viscosity of Common Fluids Fluid S.G. Viscosity (SSU)AmmoniaSAE 30 oil deg FBrineGasolineGlycerineNitric AcidSulfuric AcidWaterProMinent Fluid Controls
15 Vapor PressureMatter exist as solids, liquids or gasses. The state of matter depends on the compound itself, the pressure around it, and the temperature.The Vapor Pressure of any fluid relates to the pressure and temperature at which it flashes from a liquid phase to a gas phase. It is defined as the pressure exerted when a liquid is in equilibrium with its own vapor.The higher the vapor pressure, the more likely the fluid will vaporize on the suction side of a pump during the suction stroke, causing cavitation.
17 Pressure Relief Options - Flooded Suction Pressure Relief may discharge back to tank, but where tank is distant from pump, relief back to suction line is common.3-port PRV2-Port BPV on Tee
18 Pressure Relief Options - Suction Lift Two port back-pressure valve off of a tee on the discharge lineThree port in-line pressure relief valve discharges to tank through relief port
19 Backpressure Valve Provides backpressure to improve repeatability. Prevents siphoning when suction head exceeds discharge head.Pressure Adjusting NutSpringDiaphragmDiaphragm Hub
20 Backpressure ValveThe injection quill can create a venturi effect in a flowing pipe, developing a vacuum. This can draw chemical through the system even if the pump is stopped.The anti-siphon (backpressure) valve prevents the vacuum from causing chemical to be drawn into water line.
21 Backpressure ValveThe backpressure valve also prevents fluid from simply free-flowing through the system when the suction port is higher than the point of discharge.
22 Backpressure ValveWhen discharging into a vacuum line, use two backpressure valves to ensure maximum protection against siphoning.Regulatory agencies may require use of two anti-siphon valves in certain applications such as adding fluoride to drinking water.The backpressure created by the two valves (and the injection valve) is not additive. Whichever valve is set at the highest pressure will determine the system pressure at the pump.
23 Pulsation DampenerIn a reciprocating pump system, the entire fluid column between the pump and injection point stops flowing at each suction stroke and is forced to flow at each discharge stroke.Overcoming inertia creates large momentary pressure spikes on the pump system.
24 Pulsation DampenerAIRFLUIDA pulsation dampener minimizes the pressure spikes by using compressed air to absorb the forces due to momentum of the fluid inertia.The flow losses are called acceleration/deceleration forces.
25 Pulsation DampenerPrinciple of Operation: Air is compressible, fluid is not.Size dampener volume to 26 times fluid displacement per stroke, or consult piping program.Charge dampener air pressure to 90% of fluid pressure. You must have backpressure for dampener to be effective.Locate dampener as close to pump as possible, preferably as shown.
26 Suction Lift vs. Flooded Suction Actual lift = Rated lift (water)/ Specific GravityRequires foot valve/strainerShort suction line best. Line should always be sloping upwards.Required for self-degassing pumps and degassing bleed valves.Flooded SuctionMinimizes cavitation and off-gassing problems.Best for viscous fluids.Requires isolating valve.Short suction line best. Line should always be sloping upwards.Diaphragm failure can drain tank.
27 Suction Side Pulsation Dampening Where losses in suction line cause cavitation, a suction side pulsation dampener may be required. The air side of the dampener should be at atmospheric pressure (not charged).
28 Foot ValveThe foot valve is used in a suction lift application to prevent loss of prime when the pump is stopped, and to improve repeatability by preventing cavitation.Suction TubeTube FittingCheck BallBall Check Seat30 mesh screen keeps solids outCeramic weight keeps suction line straight, ports let fluid in.
29 Injection ValveInjection quill puts chemical into flow for good mixingNPT thread to mount into pipeValve Spring (not used in PTFE valves) provides backpressure, ensures ball seating.Check BallBall Check SeatTube FittingDischarge Tubing from Pump
30 noelt:Real pic of cal columnCalibration ColumnProvide a verification of the flow rate of the chemical feed pumpAvailable in borosilicate glass or PVCSizes from 100 mL to mLMarked in gallons or milliliters
31 Multifunction ValveOperated by smooth-action rotary knobs which automatically return to their initial position when releasedMounted directly on the liquid end of the pump for:BackpressureAntisiphonPressure reliefPrimingDraining the discharge line
32 Float Switch Monitors the fluid level in the chemical tank Single stage functionMinimum level indication with simultaneous shut down of the pumpTwo stage functionFirst stage early warning annunciationSecond stage will shut down the pump after an additional drop in the fluid level
33 Flow MonitorThe metering monitor is used to monitor the volume per pump stroke by using a plastic encapsulated metal float that is detected by the adjustable proximity sensor. Adjustable from strokes. Plugs into front of pump.
34 Typical Accessory Installation Suction Lift noelt:Ken to find different graphicTypical Accessory Installation Suction LiftInjection Valve prevents backflow from pipeBackpressure/Antisiphon valve provides backpressure for repeatability, prevents siphoningPressure gauge allows setting valve pressuresPulsation dampener reduces head loss, pulsationPressure relief valve protects system componentsFoot valve/strainer prevents loss of prime, plugging by solids
35 Piping Simulation Used for motor driven pumps only Shows if you need accessoriesSolves problems BEFORE they happenApplication will run well
36 Information Necessary Pump typeInformation from the technical data in the catalogChemical being meteredSuction liftChemical tank pressureSize and length of suction and discharge linesNumber of valves and fittings in the linesBack-pressureDischarge head