1 hydraulic principles. 2 the information provided in this presentation should be fully understood...

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Hydraulic Principles

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• The information provided in this presentation should be fully understood to ensure success in those non-typical, P/C fluids handling applications. Proper selection of Moyno® progressing cavity pumps is dependent upon understanding Fluid Dynamics and Hydraulic Principles, i.e., Net Positive Suction Head conditions [(available vs. required) and stated as NPSHA or NPSHR)], friction loss calculations and horsepower sizing.

• Moyno credits the Cameron Hydraulic manual for basic definitions. Because this manual typically deals with centrifugal pumping applications, we have clarified some of these definitions to better relate with our progressing cavity pumping principles.

Overview

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• Pumping…To move a liquid against gravity, as with a pump, work must be expended. A pump may actually raise the liquid, force it into a pressure vessel, or merely give it enough head to overcome pipe friction.

• No matter what the service required of a pump, all forms of energy imparted to the liquid in performing this service must be accounted for in establishing the work performed.

• In order that all these forms of energy may be algebraically accounted for, it is customary to express them all in terms of ‘head’ expressed in “feet of liquid” or “feet of fluid”.

Overview

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Hydraulic Principles

• Hydraulics deal with the behavior of liquids at rest or in motion.

• Proper selection of Moyno® progressing cavity pumps is dependent upon understanding :– NPSHA – Friction loss calculations– Horsepower sizing– Viscosity– Fluid rheology

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Liquid Flow

• During passage through a pipe, the flow of a liquid is said to be laminar, or turbulent, depending upon the velocity of the fluid through the pipe, the size of the pipe, and the viscosity of the liquid.

• Laminar flow is defined as a streamline flow with consistent velocity of a fluid near a solid boundary.

• Turbulent flow is defined as a fluid flow in which the velocity at a given point varies erratically in magnitude and direction.

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• A Reynolds number is used to calculate the line loss exhibited by a

liquid; Moyno’s Computer Aided Pump Selection (CAPS) program will take this into consideration for you.

• In fluid mechanics, the Reynolds number is the ratio of inertial forces to viscous forces.

• Calculating the Reynolds number will help in determining whether the flow is turbulent or laminar. The main application where the Reynolds number and turbulence is considered relates to the settling of solids in a slurry.

• Laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and are characterized by smooth, constant fluid motion, while turbulent flow on the other hand occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce random eddies, vortices and other flow fluctuations.

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Where...

V = Average velocity (ft./sec.)

vVD

R =v = Kinematic viscosity pumped fluid

(ft.2/sec.) (ex. Kin. Visc. of water = .00001211 ft.²/sec.)

D = Average internal pipe diameter (ft.)

Liquid Flow

• For values of “R” less than 2,000, the flow is considered LAMINAR.• For values above 4,000, it is said to be TURBULENT.• Any value between 2,000 and 4,000 is considered the CRITICAL ZONE

where the flow is generally said to be turbulent for the purpose of friction loss or pressure drop calculations, because turbulent flow results in higher friction losses than laminar flow.

• The Reynolds number, although important to know, is not often used when selecting Moyno progressing cavity pumps. We do suggest, however, you remain familiar with the principles and terms.

• Again, the main application where R and turbulence is considered, relates to the settling of solids in a slurry.

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• An example application is illustrated in the next two slides showing the CAPS screens when utilizing the: Calculating Pipe Loss feature.

• Example: Water moving through 100 feet of 3 inch diameter schedule 80 pipe, at a flow of 100 GPM and at a velocity of 5 feet / second, has a Reynolds number of 109,034.479, and “head loss” more commonly stated as 7.859 psi (see CAPS Pipe Friction Loss chart below).

Example

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Reynolds Number is used to calculate the Line Loss in CAPS

Reynolds Number For Water at 5 ft/sec

Note: 5 ft/sec is the Velocity & Turbulence required for acceptable CIP Cleaning

Reynolds Number in Caps

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Rule Of Thumb

•Use Sch 80 to approximate sanitary tubing ID

• Increasing viscosity decreases turbulence & Reynolds Number

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Fluid Principles

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Viscosity

• In moving liquids, resistance to flow is called Viscosity.

• Viscosity plays an important role when selecting Moyno progressing cavity pumps because you need to understand how the fluid is going react in the pump i.e. at the suction and in the pumping elements.

• It is vital to proper pump selection, and all efforts must be made to obtain accurate viscosity data during the sizing process.

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Viscosity

• Viscosities of most liquids vary with changes in temperature.

• Viscosity of moving fluids can change depending upon the extent to which the liquid is agitated or sheared.

• However, pressure changes normally have no effect on the viscosity of a fluid.

• The following chart illustrates various viscosity ratings from zero to a million centipoise.

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Viscosity

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Cavity only half full

•1 CPS = Above 1800 RPM

•100 CPS = 700 RPM

•1000 CPS = 150 RPM•10,000 CPS = 30 RPM

Effects of Viscosity

• The more viscous a fluid, the slower the pump should operate in order to permit the fluid to enter into the cavity.

• Even at reduced speeds, the pump may not develop 100% volumetric efficiency and this must be accounted for in the selection process.

• Loss of fill efficiency as it relates to viscosity vs. maximum pump speed for any given element

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• Most fluids shear thin to a level well below their static viscosity (single Brookfield point)

• Pumps are applied based on shear viscosity in a flow condition. Moyno can provide shear rate testing free of charge

• For higher viscosity ranges, open throat style pumps are used with auger screw on the connecting rod to enhance feed

Flights on Conrod offers low cost auger feed compared to other gear, lobe or hose PD pumps

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PEC 449

• Developed to determine Volumetric Efficiency• Consult with your regional manager to explain its use• CAPS utilizes a math model of PED 449 curve

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1.Transfer 65%

2.Metering 98%

3.Extrusion 95-100%

Application Efficiency


• Minimum Recommended Volumetric Fill Efficiencies • Rule of Thumb – strive to obtain these minimum levels

before moving up to the next element size• CAPS uses the term “Intake Index”, where 0 = 0% and

10.0 = 100%

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Viscosity

• A liquid is said to be a NEWTONIAN fluid if its viscosity is unaffected by agitation (shear) as long as the temperature remains constant. Examples of Newtonian fluids would be water, mineral oil or silicone.

• A liquid is Non-NEWTONIAN and also displays “THIXOTROPIC” characteristics if its viscosity decreases as it is “sheared” at constant temperatures. 98% of Moyno’s applications fall into this category; examples of thixotropic fluids would be molasses, glues, paints, coatings, and mustards.

• A fluid is Non-NEWTONIAN and said to be “DILATANT” when agitation [putting energy into a product] of the liquid causes the viscosity to increase. Examples of Dilatant fluids are candy compounds and special paper clay slurries.

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• Additional Non-Newtonian terms and their explanations for you to be aware of are found in the definition of terms section at the end of this chapter.

• Again, viscosities of most liquids vary with changes in temperature, but pressure changes exerted upon them, normally has no effect. So, the viscosity of moving fluids will change depending upon the extent to which the liquid is agitated / sheared and most typically affected by flowing through a pipe at a specific velocity.

• Most liquids are Thixotropic (shear thinning) as noted in the following Brookfield viscosity chart.

Summary

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Most Products are Thixotropic (Shear Thinning)

• As part of Moyno’s Ultra-Serve program, we provide Shear Rate verses Viscosity testing “Free of Charge”

• Velocity used instead of Sec -1. Allows you to use for pipe loss calculations based on the pipe shear rate.

Coating Color (52% Solids) with Dilatant

Characteristics

Thixotropic (Shear Thinning)

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System Head Calculations

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• The pressure existing at any point in a liquid at rest is a result of the atmospheric pressure exerted on the surface, plus the weight of the liquid above the specific point in question.

• This pressure is equal in all directions and acts perpendicularly with any surface in contact with the liquid.

• A column of liquid is called the “pressure head” or “static head” and is normally expressed in feet of liquid.

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• A column of liquid is called the “pressure head” or “static head” and is normally expressed in feet of liquid.

• Unlike centrifugal pump applications, it is strongly recommended that total head calculations for the suction side be listed separately from those on the discharge side, to help avoid the possibility of overlooking severe suction conditions.

• H = hd – hs (flooded suction)H = hd + hs (suction lift)

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Static Suction head

Static suction head (expressed in feet) is the vertical measurement of the liquid above the centerline of the pump rotor and is generally a positive head measured in feet/fluid.

The total suction head is equal to the static height in feet that the liquid supply level is above the pump suction, less all suction line losses plus any pressure existing at the suction supply source.

System Head Calculations• Static Suction Head exists when the liquid supply level is

above the pump suction centerline. This is most often referred to as a “flooded suction”.

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• It should be noted that even when the liquid supply level is above the pump suction, the equivalent of a lift could exist if the total suction line losses exceed the positive static suction head.

• An example of applications where this condition exists would be pumping from an evaporator or de-aerator tank, in which case there exists a vacuum effect.

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• Static Suction Lift exists when the liquid supply level or suction source is below the pump suction. Total suction lift is equal to the static lift in feet, plus all friction losses in the suction line. Moyno pumps are able to suction lift 28 feet of Water at Sea level.

• When the liquid supply or suction source is above the pump suction and under a vacuum, the equivalent of the suction lift will exist.

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Static Suction Lift

Static lift conditions are present when the liquid level on the suction side of the pump is below the centerline of the pump rotor.

When discussing suction lift conditions, it is important to recognize the vertical lift measurement is taken from the lowest level in the reservoir.

In many instances, the liquid level will vary dramatically..


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• When the liquid supply or suction source is above the pump suction and under a vacuum, the equivalent of the suction lift will exist.

• Static discharge head.• All piping and friction losses on the discharge

side of the pump including pipe, elbows, valves, strainers, etc.

• Pressure in the discharge chamber (if a closed vessel).

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Static Discharge Head

This figure is based upon the upper most level the fluid accumulates in the receiving vessel.

Static discharge head is the measurement, expressed in head in feet, from the centerline of the pump to the highest elevation in the discharge system.


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Net Suction head

Net Discharge Head

Total Dynamic Head (TDH)

Net Discharge Head- Net Suction Head= Total Dynamic Head (TDH)


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Net Suction Lift

Net Discharge Head

Net Discharge Head+ Net Suction Lift= Total Dynamic Head (TDH)


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H = hd – hs (flooded suction) H = hd + hs (suction lift)

Where... H = Total system head

hd = Total discharge

hs = Total suction head


• The total system head or total dynamic head is equal to the total discharge head, minus the total suction head, if positive, or plus if a suction lift.

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Liquid Head ( Feet ) =PSI x 2.31

Sp Gr

Pressure ( PSI ) =Head in Feet x Sp Gr

2.31


• Head and Pressure are interchangeable terms provided they are expressed in their correct units. The following are key conversion formulas for you to use when analyzing pumping systems:

• Sp gr =Specific gravity of the liquid.

• Pressure and friction loss calculations also play a vital role in selecting Moyno progressing cavity pumps.• Suction and discharge pressures must be known to ensure the proper pump and accessory equipment is

selected.• More will be discussed on this topic in the “How to Select” section.

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Summary

• Pressure and friction loss calculations play an important role in properly selecting Moyno progressing cavity pumps.

• Suction and discharge pressures must be known to ensure the proper pump is selected.

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NPSH Available in the Application

≥ NPSH Required by the pump

+Safety Factor

Net Positive Suction Head

• The Net Positive Suction Head (NPSH) calculation is vital when selecting Moyno progressing cavity pumps.

• Failure to have adequate net positive suction head available in a pumping system will result in inefficient pump operation up to and including damage to the pump in the form of cavitation. This will result in loss of flow and failure of the pumps Stator.

• Per Hydraulic Institute standards - Safety Factor = 3 FT Head or 1 PSI

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• The NPSH is the total suction head in feet of liquid less the absolute vapor pressure (in feet) of the liquid being pumped.

• NPSH must always have a positive value and can be calculated by using the following equations:

Net Positive Suction Head

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For suction lift... NPSHa = ha – hvpa - hst - hfsFor positive (flooded) suction... NPSHa = ha – hvpa + hst - hfsWhere...

ha = Absolute pressure in feet of liquid on the surface of the liquid supply level (this will be barometric pressure if suction is from an open tank or sump, or the absolute pressure existing in a closed tank such as an evaporator or de-aerator).hvpa =The head in feet corresponding to the vapor pressure of the liquid at the temperature being pumped.

hst = Static height in feet that the liquid supply level is above or below the pump suction centerline.

hfs = All suction line losses in feet including entrance losses and function losses through pipe, valves, filters, etc.

Net Positive Suction Head Available - NPSHa

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68 Degree F Water

Atmospheric Pressure

10 Ft.

Open System, 68°F Water At Sea Level

Atmospheric Pressure = 14.696 psia

14.696 psia = 33.96 ft. abs.

Vapor Pressure of Water @ 68°F = 0.783

100 gpm, 3” line, 1 cps (for suction losses, hfs)

NPSHa = ha – hvpa + hst – hfs

NPSHa =33.96 - 0.783 + 10.00 - 0.236 = 42.94 Ft

NPSHa Example 1


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10 Ft. LiftAtmospheric Pressure

68 Degree F Water

NPSHa Example 2

Open System, 68°F Water At Sea Level, 10’ lift

Atmospheric Pressure = 14.696 psia

14.696 psia = 33.96 ft. abs.

Vapor Pressure of Water @ 68°F = 0.783

100 gpm, 3” line, 1 cps (for suction losses, hfs)

NPSHa = ha – hvpa - hst – hfs

NPSHa = 33.96 - 0.783 - 10.00 - 0.236 = 22.94 Ft


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Net Positive Suction Head Required - NPSHR

• When sizing Moyno pumps, two values of NPSH must be considered.

• The first is Net Positive Suction Head Required, determined by Moyno, Inc., and can be calculated from the performance curves provided by Moyno.

• NPSHR figures can be located in the upper right-hand corner of all of our standard performance curves.

• From the chart, the higher the pump RPM, the higher the NPSH required, this is because the cavity is opening and closing at a much higher rate, leading to higher entrance losses

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Net Positive Suction Head Required - NPSHr

• CAPS is capable of returning the NPSHR value for a particular pump by entering 1 cps into the viscosity line

• If a viscosity greater than 1 is entered, no NPSHr value will be given

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• The work performed in pumping or moving a liquid from one point to another equals the required horsepower. Horsepower also depends on the weight of the liquid being handled and the total differential pressure being developed. The following is the most commonly used HP formula:

• Brake HP = GPM x psi /1714

• Where…– GPM = Gallons per minute – psi = Pounds per square inch– GPM should be noted as: theoretical flow + slip = actual flow

• Horsepower calculations will be discussed more thoroughly in the “How to Select” section.

Horsepower

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Definitions

The below definitions are provided for your clarification and can also be foundon the home screen of Moyno’s CAPS program under the Glossary button….

• Liquid: A substance in that state in which its particles have enough cohesion to tend to remain in one mass, but still are capable of moving freely among themselves upon the application of the slightest force, the mass having, like solids, a definite volume but, unlike solids, no definite shape.

• Pressure: (Common Usage) – Pressure per unit area or “intensity” of compressive stress within the liquid, above local atmospheric pressure. It is commonly expressed as “pounds per square inch”, “kilograms per square centimeter” or “bars”.

• Three pressure terms are commonly used in pumping opportunities … absolute, barometric and gauge pressure.

1. Barometric Pressure -- The atmospheric pressure at the locality of the application and varies with altitude and climatic conditions.

2. Absolute Pressure -- The pressure above absolute zero. It may be above or below the atmospheric pressure existing at the point under consideration.

3. Gauge Pressure -- The pressure above atmospheric at the locality where it is measured. A vacuum is a negative gauge pressure.

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• Pressure Head or Head: Designates the vertical height of a static column of the fluid that would cause the same pressure or compressive stress as exists in the fluid mass at the point in question, also know as….Static Head.

• Static Head: The height of a column of liquid acting on the pump suction or discharge.

• Atmospheric Pressure: Pressure exerted by the atmosphere, which varies with the applications elevation, typically in the mid-west US = 14.7 PSI

• Vacuum: The difference between atmospheric pressure at a given elevation and some pressure below the atmospheric pressure. Usually expressed in inches or millimeters of mercury, but can be converted to PSI, i.e. 3 inches of mercury = 3 PSI or 155 millimeters of mercury = 3 PSI.

Definitions

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Definitions

• Vapor Pressure: Every liquid at any temperature above its freezing point exerts a pressure due to formation of vapor at its free surface. This pressure, known as the vapor pressure of the liquid, is a function of the temperature of the liquid. The higher the temperature, the higher the vapor pressure. In any pumping system the pressure at any point should never be reduced below the vapor pressure corresponding to the temperature of the liquid, because the liquid will form vapor which will partially decrease liquid flow into the pump.

• Static Suction Lift: The vertical distance, in feet, from the liquid supply level to the pump center line, the pump being above the supply level.

• Static Suction Head: The vertical distance, in feet, from the liquid supply level to the pump center line, the pump being below the supply level.

• Static Discharge Head: The vertical distance, in feet, from the pump center line to the point of free delivery of the liquid.

• Total Static Head: The vertical distance, in feet, between the supply level and the discharge level of the liquid being handled.

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• Friction: Measured in feet of the liquid handled, this is the equivalent head needed to overcome the resistance of the pipe, valves and fittings in the pumping system. Friction head exists on both the suction and discharge sides of the pump and varies with liquid flow rate, pipe size, interior condition of the pipe, type of pipe and nature of the liquid being handled. Converting to PSI = ft/hd X specific gravity; divided by the constant of 2.31.

• Velocity Head: Liquid moving through a pipe at any velocity possesses kinetic energy due to its movement. Velocity head is the distance through which the liquid must fall to acquire a given velocity and is found from hv = v2/2g, where hv = velocity head, ft. of liquid; v = liquid velocity, ft. per sec.; g = acceleration due to gravity = 32.2 ft. per sec2.

• NPSH Available: A function of the system. It is the sum of the suction head or lift, friction head and the vapor pressure of the liquid being handled.

• NPSH Required: A function of pump design. It varies from one make of pump to the next and with the capacity and speed of any given pump.

• Pascal’s Law: Pressure, if extended anywhere upon a mass of liquid, (1) is transmitted with equal intensity in all directions; (2) acts with the same force on all equal areas; and (3) acts in a direction at right angles to those areas.

Definitions

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• Specific Gravity: The ratio of the specific weight of a substance to the specific weight of some standard substance. For liquids, the standard usually employed is water.

• Barometers: The pressure gauges used to measure atmospheric pressure.

• Newtonian Fluids: Those fluids whose viscosity depends only on temperature and ambient pressure and are independent of the rate of shear or the length of time the fluid is sheared.

Shear Stress Viscosity

Shear Rate Shear Rate

Definitions

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• Non-Newtonian Fluids: Those fluids whose viscosity depend not only on temperature and ambient pressure, but may also depend on the rate of shear and/or the length of time that the fluid is sheared.

• Types of Non-Newtonian Fluids:A. Time Independent – the fluid can be sheared for any length of time at a constant shear

rate with no subsequent change in viscosity.– Bingham Plastic – Shear thinning after an initial stress is overcome.– Pseudo Plastic – Shear thinning.– Dilatant – Shear thickening.

B. Time Dependent – The fluid viscosity is affected by the length of time the fluid is sheared.

– Thixotropic – Shear thinning.– Rheopectic – Shear thickening.

C. Viscoelastic Fluids – Possess both elastic and viscous properties (bread dough is an example).

Definitions