1. Metering Pumps and Pump Systems

2. METERING PUMP DEFINITION
Convey (like any pump)
Measure (repeated displacement of defined volume)
Adjust
Volume per displacement
Frequency of displacements
Convey
Adjust
Measure

3. METERING PHILOSOPHY
Think of the pump as a continuous fluid measurement device
Converts 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.”
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5. What claims to be a Metering Pump, but isn’t?
Gear Pump
Displacement per revolution not adjustable. Not linear from high to low RPMs due to slip at low speed.
Air Operated
Diaphragm Pump
Displacement per stroke not adjustable. Not repeatable due to variable air pressure, flexible diaphragm.
Progressing
Cavity Pump
Displacement per revolution not adjustable. Chemical incompatibility common w/ rotor.
Displacement per revolution not adjustable. Tube stretch prevents repeatability.
Peristaltic
Pump
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6. What’s all This?

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 System
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8. Suction Head Negative Suction Head (suction lift)
Positive Suction Head
(flooded suction)
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9. Suction Lift
Atmospheric 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 water
If the pump pulled a perfect vacuum, the maximum suction lift possible on earth, pumping water, is 34 feet.
14.5 psia
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10. What happens if the tank is not vented (open to atmosphere)?
Suction Lift
What happens if the tank is not vented (open to atmosphere)?
14.5 psia
14.5 psia
14.5 psia
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11. Specific Gravity
Specific 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. = 1.84
Ammonia density = lbs/gal Therefore
Water density = lbs/gal S.G. = 0.63
Because 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.
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12. Specific Gravity Impact on Suction Lift
Actual Suction Lift =
Rated Suction Lift (water) / S.G.
Rated Suction Lift for VAMb04120 = 6.6 feet
Application: Chromic Acid (1.4 SG)
Actual Suction Lift = 6.6 / 1.4 = 4.7’
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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 pump
Put springs in the valves to help seat the balls
Use high viscosity solenoid pumps
Reduce stroking rate to minimum possible
Keep stroke length as great as possible
Provide flooded suction with oversized suction line
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14. Specific Gravity and Viscosity of Common Fluids
Fluid S.G. Viscosity (SSU)
Ammonia
SAE 30 oil deg F
Brine
Gasoline
Glycerine
Nitric Acid
Sulfuric Acid
Water
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15. Vapor Pressure
Matter 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.

16. Pressure Relief Valve
Prevents over-pressurizing pump and piping system.
Pressure Adjusting Nut
Diaphragm
Spring
Diaphragm Hub

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 PRV
2-Port BPV on Tee

18. Pressure Relief Options - Suction Lift
Two port back-pressure valve off of a tee on the discharge line
Three 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 Nut
Spring
Diaphragm
Diaphragm Hub

20. Backpressure Valve
The 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 Valve
The 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 Valve
When 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 Dampener
In 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 Dampener
AIR
FLUID
A 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 Dampener
Principle 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 Gravity
Requires foot valve/strainer
Short suction line best. Line should always be sloping upwards.
Required for self-degassing pumps and degassing bleed valves.
Flooded Suction
Minimizes 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 Valve
The 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 Tube
Tube Fitting
Check Ball
Ball Check Seat
30 mesh screen keeps solids out
Ceramic weight keeps suction line straight, ports let fluid in.

29. Injection Valve
Injection quill puts chemical into flow for good mixing
NPT thread to mount into pipe
Valve Spring (not used in PTFE valves) provides backpressure, ensures ball seating.
Check Ball
Ball Check Seat
Tube Fitting
Discharge Tubing from Pump

30. noelt:
Real pic of cal column
Calibration Column
Provide a verification of the flow rate of the chemical feed pump
Available in borosilicate glass or PVC
Sizes from 100 mL to mL
Marked in gallons or milliliters

31. Multifunction Valve
Operated by smooth-action rotary knobs which automatically return to their initial position when released
Mounted directly on the liquid end of the pump for:
Backpressure
Antisiphon
Pressure relief
Priming
Draining the discharge line

32. Float Switch Monitors the fluid level in the chemical tank
Single stage function
Minimum level indication with simultaneous shut down of the pump
Two stage function
First stage early warning annunciation
Second stage will shut down the pump after an additional drop in the fluid level

33. Flow Monitor
The 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 graphic
Typical Accessory Installation Suction Lift
Injection Valve prevents backflow from pipe
Backpressure/Antisiphon valve provides backpressure for repeatability, prevents siphoning
Pressure gauge allows setting valve pressures
Pulsation dampener reduces head loss, pulsation
Pressure relief valve protects system components
Foot valve/strainer prevents loss of prime, plugging by solids

35. Piping Simulation Used for motor driven pumps only
Shows if you need accessories
Solves problems BEFORE they happen
Application will run well

36. Information Necessary
Pump type
Information from the technical data in the catalog
Chemical being metered
Suction lift
Chemical tank pressure
Size and length of suction and discharge lines
Number of valves and fittings in the lines
Back-pressure
Discharge head

37. Any Questions?