High Lifter Gravity Water Pump? All Answers

There are three factors that affect the pressure in your irrigation or sprinkler system. These factors are the capacity (or total flow rate), the diameter and overall length of the hose, and any elevation change between your water source and the sprinkler.

efficiency or total flow rate

Capability is the first thing to consider when figuring out how far you can pump water and how much pressure you have to operate your sprinkler(s). How much water can your pump move and at what pressure? If in doubt, you should be able to inquire with the manufacturer of the pump.

What is the total flow rate or gpm required for the sprinkler to operate? How much pressure (or psi) can your pump produce at that flow rate? Knowing this will give you the base print to start with. From there you can calculate the other factors causing the pressure loss.

hose diameter and length

In order to choose the correct diameter of tubing, you need to know the total flow rate (gpm) going through the tubing to calculate “Frictional Loss”.

Friction loss is the pressure loss that occurs in hose flow due to the friction of the fluid near the hose surface.

The friction loss increases the more gallons per minute you push through a fixed sized hose. To reduce friction losses, you need to increase your hose diameter to achieve the desired flow rate and distance your water has to travel to reach your sprinkler.

The friction loss increases with increasing hose length. There is a friction loss chart with the measurements calculated for you, measured per 100 feet of hose.

Using this calculation, multiply the friction loss factor by the number of 100 feet of hose you need from your pump to the sprinkler. Here’s how to find your total friction loss through your hose.

elevation change

You need to know the full elevation change from your water source to your sprinkler or sprinkler. Altitude can change your pressure both positively and negatively. Pushing water uphill requires pressure, and when water flows downhill, pressure is built up.

A simple calculation is that for every 10 feet of gain you lose -4.33 psi. For every 10 feet of elevation gain, you get +4.33 psi.

Once you know your total pressure drop, subtract it from your starting pressure. If you have enough remaining pressure and flow, your pump will feed your sprinklers of any configuration.

*Note: You can increase the hose diameter if necessary to reduce pressure drop and adjust your number accordingly.

…in the vicinity of sewage treatment plants are called low-lift pumps. These move large amounts of water at relatively low delivery pressures. Pumps that introduce treated water into arterial mains are called high-lift pumps. These work under higher pressures. Pumps that increase the pressure in the distribution system or pump water into an elevated…

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I’m working on a small project where I have to pump the water up about 2 meters from a well with a diameter of 30 cm in a relatively small space.

I’ve looked at ram pumps but don’t see a way to use that as I don’t have a “higher” water source. I’ve also looked at electric pumps on Alibaba and it seems I’m ending up at around 2W, which seems like a lot for an iot device – I really don’t want to have to charge the device every week, especially. as there is little energy to harvest nearby.

The requirements are:

Ability to pump water up 2 meters

A flow of about 12 liters per hour would be sufficient

Ideally 12v or lower

What are the best options? 🙂 I know product endorsements aren’t allowed, but what techniques should I look at overall? Is there a resource somewhere that compares the efficiency of different pumping methods?

[EDIT] RE Comments: In terms of efficiency, I mean as few watts as possible. I won’t have easy access to charge (sun and wind are off but potentially the energy of the water flowing into the fountain could create a small charge for the battery). If we can get to the point where the battery only needs to be changed once a month, that would be perfect.

: A pump with a solid piston for drawing in and forcing a liquid (such as water) through valves to a considerable height above the pump or under a considerable pressure

Earth’s gravity is strong, but can water ever naturally work against it and flow uphill?

The answer is yes, if the parameters are right. For example, a wave on the beach can flow uphill, even if it’s just for a moment. Water in a siphon can also flow uphill, as can a puddle of water if it lifts a dry paper towel immersed in it.

Even stranger, Antarctica has a river that flows uphill under one of its ice sheets. How does science explain these watery uplegs? [Where did the water of the earth come from?]

waves and siphons

Waves (driven by wind), tides (mainly caused by the gravitational forces of the moon), and tsunamis (often caused by earthquakes and underwater landslides or volcanoes) can move water against gravity. The energy and forces generated by these natural phenomena can push water upwards, allowing it to naturally rise into a wave or run up a coast.

A siphon acts under different pressures. People have used siphons since ancient times; According to a 2014 study published in the journal Scientific Reports (opens in new tab), the ancient Egyptians used siphons for irrigation and winemaking. Nowadays, thieves could use siphons to steal gasoline from cars. However, there is still debate about how siphons work.

You can think of a siphon by thinking of two cups connected by a tube shaped like an upside down “U”. The cup filled with water stands on a step and an empty cup stands below it. If an experimenter sticks one end of the tube into the water-filled beaker and sucks out the air like you would with a straw, the water is allowed to flow into the tube.

A siphon is created when the water flows up one side of the pipe and down the other into the empty cup.

According to a 2011 study in the Journal of Chemical Education, siphons work in a vacuum, so atmospheric pressure doesn’t appear to be a factor. Rather, gravity and molecular cohesion appear to play a role, according to a 2015 study in the journal Scientific Reports (opens in new tab).

Gravity accelerates the water through the “lower” part of the tube into the lower cup. Because water has strong cohesive bonds, these water molecules can pull the water behind them through the uphill portion of the tube, according to Wonderopolis, a site where daily questions are answered.

However, many liquids that don’t have strong cohesive bonds still work in siphons, so Wonderopolis says it’s unclear exactly how siphons work in different cases.

capillary action

What about the paper towel example? This action, called capillary action, causes small amounts of water to flow uphill against gravity as long as the water flows through tight and small spaces.

This upward flow occurs when adhesion of a liquid to the walls of a material, such as B. the paper towel, according to the U.S. Geological Survey is stronger than the cohesive forces between their liquid molecules.

In plants, water molecules are pulled up in capillaries called the xylem, which help the plant draw water from the soil, the USGS said. [Are trees vegetarian?]

Antarctic River

According to Robin Bell, professor of geophysics at Columbia University’s Lamont-Doherty Earth Observatory in New York, a river flows uphill beneath one of Antarctica’s ice sheets.

Beneath the continent’s ice lie the Gamburtsev Mountains, a massive mountain range with peaks and valleys about the size of the European Alps, she said. “There’s water in the valleys,” Bell told Live Science. “We can tell because when we fly over it, the echo from the [ice-penetrating] radar is much stronger.”

Interestingly, researchers can say the river is flowing backwards because the ice on it is oriented against the direction of ice flow, Live Science previously reported. That alignment and the tremendous pressure from the overlying ice sheet are pushing the water uphill, Bell said.

A diagram showing the river flowing uphill in Antarctica. (Image credit: Robin Bell)

“We found that the ice was pushing the water up the hill and pushing the water backwards,” Bell said.

There are other instances where water has naturally run uphill. For example, an 8.0 magnitude earthquake shook southeastern Missouri so hard that the Mississippi temporarily flowed backwards, Live Science previously reported. Additionally, a 2006 study in the journal Physical Review Letters showed that small amounts of water placed on a hot surface — say, a scallop pan — can “climb” tiny stairs of steam if the water is hot enough to live Science reported.

Original article on Live Science.

Water issues in India have always been problematic, both in rural and urban areas. Whether the rainfall has been good enough or the lakes that provide water are full or not, we are often faced with the wrath of water scarcity. To fight back, humanity has come up with a smart device called “Water Pumps”.

With a simple mechanism and innovative technology, these water pumps draw water from underground springs and supply it to our homes. In most rural and industrial areas, these water pumps eliminate the problem of water shortage and have proven to be an amazing help.

Now that there are many options on the market; You may be confused as to which one to invest in. Here’s a simple guide to help you make a wise choice.

WHAT TYPES OF PUMPS ARE AVAILABLE ON THE MARKET?

Depending on your needs and necessities, there are two main types of pumps on the market namely domestic and agricultural pumps. They are designed so that one device is the perfect choice. Among the broad section of these two types of pumps, there are several different types that have their salient features. Read on to understand better.

A. Household Pumps

As the name suggests, domestic pumps are used in homes for daily water consumption. These pumps have a lower flow rate and power compared to agricultural pumps because they have to pump into small areas. The different household pumps are:

1. Self-priming regenerative pumps

A regenerative pump has vanes mounted on either side of the rim that rotate in an annular conduit within the pump’s body. The liquid does not exit at the top of the impeller but is returned to the bottom of the impeller. Through this circulation or regeneration, the pump primes itself again.

These pumps are suitable for pumping clear, cold fresh water, free from abrasive particles and chemically aggressive substances. Suitable for domestic water supply, lawn sprinklers, gardens etc. These pumps can remove air due to their self-priming ability and are therefore suitable for priming water from plumbing and therefore do not require a foot valve.

2. Centrifugal pumps

Centrifugal pumps are used to circulate water by converting kinetic rotational energy into hydrodynamic energy of the water flow. The rotational energy is derived from an electric motor. The other type of centrifugal pump with a similar mechanism is the jet centrifugal pump, which uses a stream of suctioned water to create a jet to improve suction from the underground resources.

These pumps are suitable for pumping clear, cold fresh water, free from abrasive particles and chemically aggressive substances. Suitable for domestic water supply, lawn sprinklers, gardens, small farms, irrigation, agricultural applications, draining wells and tanks, filling water in swimming pools, etc. These pumps have a higher flow rate compared to regenerative pumps. The pump must be installed with a quality ISI foot valve. Outstanding hydraulic performance and higher operational efficiency compared to regenerative pumps with lower maintenance costs.

3. Submersible pumps

A submersible pump is a device with a sealed motor that is completely submerged in bodies of water, especially open wells and artesian wells. They are an efficient and smarter choice as they do not require a primer as they are already submerged in water. They are further divided into two types:

Open Well Submersible Pumps (Water Cooled/Oil Cooled) (For Open Well Applications)

Submersible Tube Well Pumps (Water Cooled/Oil Cooled) (For Downhole Applications)

These pumps are suitable for pumping clear, cold fresh water, free from abrasive particles and chemically aggressive substances. Submersible pipe well pumps are suitable for 3″, 3.5″ and 4″ bore wells.

4. Bore Well Compressor Pumps

Bore Well Compressor Pumps are specifically designed to extract water from deep bore wells of specific diameters. Air pressure is used in this machine to lift the water out of deep wells.

These pumps are best suited for comparatively low yield artesian wells up to 600 feet deep. Compressor pumps can be used in artesian wells with muddy water where tube well pumps are not suitable. There are two types of compressor pumps, monobloc and belt driven types. The flow rate of the compressor pumps depends on the flow rate of the borehole.

5. Booster Pumps

A booster pump is a quality piece of equipment to have if you want a smooth and pressurized water supply in your home. They are specially designed to provide you with the pressurized water you need when you need it.

The automated pumping system is supplied with a pressure tank for constant water pressure across all openings connected to the piping system, making it an ideal choice for residential use. When the water pressure drops to a set level, the pump will automatically start pumping water, and when the consumption drops, the pump will automatically stop when the outlet pressure increases to the preset stop pressure.

6. Shallow well pumps

Shallow Well Pumps are a very novel choice for shallow wells. The reason for this is that they have great suction power and are a good choice for rural areas.

Shallow well pumps with a suction lift of up to 8 meters and can therefore be chosen as an alternative when the suction lift is greater than 6 metres, which is the capacity for normal self-priming pumps.

B. agricultural pumps

Agricultural pumps are the lifesaver in rural areas as water pumps are necessary for good crop production. It is also very important to choose the right pump and to help you make that informed decision here are the different types of agricultural pumps:

1. Monobloc centrifugal pumps

Like normal centrifugal pumps, monobloc pumps circulate water by converting the kinetic energy of rotation into the hydrodynamic energy of water flow. However, because they have to cover a larger area, these pumps are more efficient and have a higher flow rate (approx. 25LPS).

2. Submersible pumps

Submersible pumps keep the priming problem away and are a better option in the agricultural sector. Submersible farm pumps also work in the same way, but there is a wider range available in this category.

While there are the regular open well pumps, we also offer 4″, 6″ and 8″ well options. These pumps have a higher horsepower rating of 60 hp, a maximum operating depth of 1640 feet and a flow rate of up to 38LPS.

What should you look for in a water pump?

Vertical suction

This is the distance that water has to be drawn from its source to get to the pump. If your pump is mounted at the top of the well, the distance from the water level to the pump location is the vertical suction. This parameter must be compared with the suction height of the pump before buying.

Vertical conveyor head

The vertical distance between the pump and the pumping tank is referred to as the vertical head. This height must be matched with the pump head to ensure the pump selected is correct for your application.

references

You may have additional questions about investing in a suitable water pump for your home. Please visit our FAQ section on the V-Guard website to learn more. If you have any further questions, please contact our customer service

There you have it! Our complete water pump buying guide. Armed with this, you are sure to be able to make a wise decision in purchasing a water pump that best suits your needs.

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A pump can be defined as “a mechanical device that adds energy to a fluid to increase its flow rate and static pressure.”[1] This process can be accomplished with positive displacement pumps or kinetic energy pumps.

Flow principles and hydraulics

types of liquids

Pumps are used to move liquids including:

liquids

Dissolved gases – dissolved air and hydrocarbon vapors

Solids – sand, clay, corrosion by-products and scale

The most common types of liquids pumped in upstream operations are:

crude oil

condensate

lubricating oils

glycols

amines

water

Each fluid has different physical properties that must be considered when sizing and selecting a pump. The most important physical properties are suction pressure, specific gravity, viscosity, vapor pressure, solids content and lubricity.

types of pumps

positive displacement pumps

Positive displacement pumps add energy to a liquid by applying force to the liquid with a mechanical device such as a piston, plunger, or diaphragm. There are two types of positive displacement pumps:

back and forth movement

rotating

Piston pumps use pistons, plungers, or diaphragms to displace the fluid, while centrifugal pumps work through the meshing action of gears, cams, or screw shafts.

Kinetic energy pumps

Kinetic energy pumps (energy associated with motion) are added to a fluid to increase its speed and indirectly its pressure. Kinetic energy pumps work by drawing fluid into the center of a rapidly rotating impeller. Radial vanes on the impeller throw the liquid outwards to the impeller rim. When the liquid leaves the impeller, it comes into contact with the pump casing or the volute. The housing is shaped to direct liquid to a dispensing port. The casing slows the fluid down and converts some of its velocity into pressure. There are three classes of kinetic energy pumps:

Centrifugal, radial, axial and mixed flow designs

Regenerative Turbine

effect pumps

Centrifugal pumps account for more than 80% of pumps used in manufacturing plants because they have smooth flow, are free from low-frequency pulsations, and are not subject to mechanical problems. Fig. 1 shows pumps commonly used in upstream production operations.

Fig. 1—Pumps commonly used in manufacturing plants.

Design of pumping systems

Designing a pumping service involves three main activities: process design, mechanical design, and vendor selection.

process design. The first step in process design is to obtain a design flow rate. The design flow rate should be selected after considering all flow variations such as: e.g.:

starting conditions

Future Extensions

Maximum expected flow

The next step is to determine the fluid properties critical to the pump design. These properties include:

specific weight

temperature

viscosity

pour point

etc.

Values ​​are required at pumping conditions and in some cases also at ambient conditions. The next step is to calculate the available suction conditions such as Nominal Suction Pressure, Maximum Suction Pressure and Available Positive Suction Lift (NPSHA). (See Hydrodynamics for information on NPSHA.) Once the available suction conditions have been established, the effect of the selected control system on pump performance requirements must be determined (see Flow Rate Regulation). The next step is to calculate the minimum head pressure requirements of the pump. The last step is to calculate the total dynamic head (TDH) at the specific gravity corresponding to the nominal pumping temperature.

mechanical construction

The first step in mechanical design is to determine the design pressure and temperature required for the pump and associated piping. Once this is done, a pump type and materials of construction are selected. The next step is to determine the sparing (backup) requirements, the need for parallel operation, and the details of the control system. Then select a shaft seal type and determine the requirements for an external flushing or sealing system and estimate the power requirements and select a drive (motor, motor or turbine) for the pump. Finally, document the design by including calculations, studies, design specifications, utility requirements, and a summary of the estimate.

dealer choice

Factors that have the greatest impact on selecting the most economical pump type are:

capacity

TDH

maintenance

viscosity

capacity control

Within the general type selection, a particular building style is most influenced by:

dispensing pressure

NPSHA

liquid temperature

space and weight restrictions

liquid shear properties

hydraulic principles

Hydraulics deals with the mechanical properties of water and other fluids and the application of these properties to engineering. The hydraulics are divided into two areas:

Hydrostatics (resting liquids)

hydrodynamics (fluids in motion)

hydrostatic

A liquid has a specific volume compared to a gas, which tends to expand to fit its container. If a liquid isn’t trapped, it seeks the lowest possible level. Due to its fluidity, a liquid adapts to the shape of its container.

Print

The pressure at any point in a body of liquid at rest is caused by the atmospheric pressure exerted on the surface plus the weight of the liquid above that point. This pressure is the same in all directions.

temperature

For most fluids, an increase in temperature decreases viscosity, decreases specific gravity, and increases volume. Temperature affected:

The design of the pump

material selection

Corrosive properties of the liquid

The flange pressure/temperature ratings of the pump

air properties

Air is a mixture of oxygen, nitrogen and other compounds. Standard air pressure is defined at 60°F, 36% relative humidity and sea level. The weight of a column of air above the Earth’s surface at 45° latitude and sea level is 14.696 psia (29.92 inches of mercury). Atmospheric pressure decreases by about 0.5 psi for every 1,000 feet of elevation above sea level.

head

The head to pressure ratio is expressed as

(Eq. 1)

Where

h = height of the liquid column above a reference point

p = pressure.

The liquid column is unrelated to the area occupied by the liquid. Figure 2 illustrates head types.

Fig. 2—Types of Head.

(Eq. 2)

Where

γ = specific gravity of the liquid

ρ f = density of the pumped liquid

ρ w = density of water at standard conditions of temperature and pressure.

It is important to realize that although the pressure heads of different liquids are the same, their pressures are different due to differences in specific gravities. For example, suppose three tanks 100 feet tall, each filled with gasoline, water, and molasses. The pressure measured at the bottom of each tank is different due to the different specific gravities of gasoline (0.75), water (1.0), and molasses (1.45).

Centrifugal pump considerations

Working pressure is expressed in feet of fluid being pumped. Suction and delivery pressure are expressed as suction lift and delivery head, respectively. Pressures are expressed in feet overhead because knowing how much a pump can lift the fluid it is pumping is more important than knowing how much pressure the pump is adding to the fluid.

Positive displacement pump considerations

Operating pressures are almost always expressed in pressure (psi).

Static pressure, static buoyancy and immersion terminology

Fig. 3 illustrates the relationship between static pressure, static buoyancy and immersion. Static head is the vertical distance between a liquid level and a datum line when the supply is above the datum line. Static buoyancy is the vertical distance between a liquid level and a reference level when the reference point is above the liquid. The datum line is the center line of the pump inlet port or the horizontal center line of the first stage impeller in vertical pumps.

Fig. 3 – Relationship between static pressure, static buoyancy and immersion.

Theoretical Buoyancy

A pump that develops a perfect vacuum at its suction end can lift a column of water 34 feet. This vertical distance is called the theoretical stroke. The pressure to raise the liquid comes from atmospheric pressure. At sea level, the atmospheric pressure is approximately 14.7 psia.

Actual suction height

Because perfect vacuum is never achieved and some lift is lost due to friction in the suction line, the maximum actual suction lift for a positive displacement pump is approximately 22 feet. The maximum actual suction lift for a centrifugal pump is approximately 15 feet when pumping water from an open air tank. Positive displacement pumps can work with lower suction pressures or high suction lifts because they can create stronger vacuums. Suction lift is greater when the pressure in a closed tank is greater than atmospheric pressure.

submerge

Immersion is often confused with either static suction lift or static buoyancy. For vertical pumps, the immersion depth relates the liquid level to the setting of the pump. For horizontal pumps, the immersion depth refers to the liquid level height required in the source vessel or tank to prevent the formation of vortices and the consequent vaporization of vapors in the pump suction.

vapor pressure

As the pressure on a liquid decreases, vapor bubbles tend to be released. The vapor pressure of a liquid is the pressure at which the first vapor bubble appears at a given temperature. At 60°F, the vapor pressure of water is 0.3 psia (0.7 ft). At 212°F, the vapor pressure of water is 14.7 psia (34 ft). Fig. 4 shows the vapor pressure of water for different temperatures. For other fluids see standard references (e.g. Hydraulic Institute Engineering Data Book1).

Fig. 4 – Vapor pressure of water at different temperatures.

suspended solids

The amount and type of suspended solids entrained in the liquid can affect the properties and behavior of that liquid. Increased concentrations of solids increase the specific gravity, viscosity and abrasiveness of a liquid. The type and concentration of suspended solids can affect the type of pump selected and the materials of construction. Suspended matter also influences the choice of impeller design in centrifugal pumps, which in turn affects wear rate, efficiency and power consumption.

dissolved gases

Small amounts of dissolved gases have little effect on flow rate or other pumping requirements. When large amounts of gas enter the liquid through pipe leaks or as a result of turbulence in vessels, the specific gravity of the liquid decreases. Dissolved gases can also reduce the NPSHA level at the pump suction. (See Hydrodynamics for a discussion of NPSHA).

viscosity

Viscosity provides resistance to flow due to friction within the fluid. Viscosity levels have a significant impact on pump type selection, efficiency, head and warm-up. Highly viscous liquids reduce the efficiency and head of a centrifugal pump and at the same time increase the power requirement. The viscosity of all liquids varies with temperature. For fluid viscosity information, refer to industry standard references (e.g. Hydraulic Institute Engineering Data Book[1]).

corrosivity

The corrosive nature of the pumped medium affects pump type selection, materials of construction and corrosion tolerance. If necessary, special mechanical seals and flushing devices are required.

hydrodynamics

Hydrodynamics is the study of fluids in motion. The Bernoulli equation says so

(Eq. 3)

Where

v = mean velocity of the liquid in the tube

g = acceleration due to gravity

p = pressure, ρ = density

Z = height above a reference point

h f = friction loss between points 1 and 2. Subscripts 1 and 2 refer to points along a pipe. An examination of each of the terms in Eq. 3 provides a better understanding of the general equation for modeling a pumping system.

speed head. The velocity head is the potential energy that has been converted to kinetic energy. The velocity head can be expressed as

(Eq. 4)

(Eq. 5) where

Q = flow

d = pipe inside diameter.

The head increases the workload of a pump. Velocity level is not normally factored into actual system calculations when pipeline velocities are maintained within regulatory limits of 3 to 15 ft/sec. Velocity level is included in the total dynamic level of the centrifugal pump curves.

printhead

The energy contained in the liquid is expressed as a head and given as p/ρ in Eq. 3.

elevation head

The energy contained in the liquid as a result of its elevation relative to a reference point is called elevation and is denoted as Z in Eq. 3.

head losses

Pressure losses are potential energy lost due to frictional resistance of the piping system (pipes, valves, fittings, and inlet and outlet losses). Unlike the velocity head, the friction head cannot be ignored in system calculations. The pressure drop values ​​vary quadratically with the flow rate. Pressure drops can account for a significant portion of the total head.

loss of control

Control losses occur on the discharge side of a centrifugal pump equipped with a back pressure valve to regulate the flow. As the fluid flows through the control valve, energy is lost. Regulating losses are often the most important factor when calculating the total dynamic head of the pump, along with the static head. In pump applications, control losses are treated separately from head losses, although they are included in the hf term in Eq. 3.

acceleration head

Acceleration level is used to describe the losses associated with the pulsating flow of piston pumps. In theory, the accelerating head should fit into the hf term of Eq. 3. The Hydraulic Institute Engineering Data Book[1] covers acceleration height calculation.

Totally dynamic head

TDH is the difference between the head and the suction head of the pumping system. It is also equal to the difference in gauge readings (converted to feet) across an existing operating pump (minus head).

suction head

Suction lift is defined as the sum of the suction tank working pressure (converted to feet), the vertical distance between the suction tank liquid level and the pump datum point, minus suction line pressure drops [less velocity change,

(Eq. 6)

and acceleration head]. Suction head can be expressed as

(Eq. 7)

what can be reduced

(Eq. 8)

Where

H s = suction lift of the pumped liquid

p 1 = suction tank operating pressure

H 1 = Height of the liquid suction tank above the pump reference point

p f1 = pressure drop due to friction in the suction line.

discharge head

Head is defined as the sum of pump head working pressure (converted to feet), liquid level in the pump head above the pump datum point, pressure drop due to friction in the pump line, and control losses (head discount rate). It can be expressed as

(Eq. 9)

what can be reduced

(Eq. 10)

Where

H d = head of pumped liquid

p 2 = operating pressure of the pressure vessel

H 2 = Operating or normal head of liquid in pressure vessel above pump reference

p f2 = pressure drop due to friction in the pressure line

P c = outlet flow control valve losses.

Calculate TDH

The TDH of the pump is the difference between suction and discharge head.

(Eq. 11)

which can be replaced as

(Eq. 12)

Where

H td = required total dynamic head of a pump.

Net Suction Lift (NPSH)

NPSH is defined as the total suction lift in feet of liquid (absolute at the pump centerline or at the impeller eye) minus the vapor pressure (in feet) of the liquid being pumped.

Net positive suction lift required

Required Positive Suction Lift (NPSHR) is defined as the amount of NPSH required to move and accelerate the fluid from the pump suction into the pump itself. It is determined either by testing or calculation by the pump manufacturer for the specific pump in question. NPSHR is a function of fluid geometry and surface area smoothness. For centrifugal pumps, other factors that control NPSHR include:

The type of impeller

Impeller eye design

speeds

NPSHR is determined based on cold water handling. Field experience combined with laboratory testing has confirmed that centrifugal pumps handling gas-free hydrocarbon liquids and water at elevated temperatures perform satisfactorily, with harmless cavitation and less NPSHR than would be required for cold water.

Net positive suction lift available

NPSHA must be equal to or greater than NPSHR. If this is not the case, cavitation or flashing can occur in the pump suction. Cavitation occurs when small vapor bubbles form in the liquid due to a drop in pressure and quickly collapse explosively when the pressure in the pump increases. Cavitation reduces efficiency, capacity and head and can cause serious erosion of pump parts. Flashing causes the suction cavity of the pump to be filled with vapors and as a result the pump becomes vapor locked. This usually causes the pump to freeze, known as pump seizure.

NPSHA is not a function of the pump itself but of the piping system for the pump. You can count on that

(Eq. 13)

Where

p A = atmospheric pressure

p va = liquid vapor pressure at pumping temperature.

NPSHA decreases with increasing fluid temperature and pipe friction losses. Since pipe friction losses change quadratically with flow, NPSHA also changes quadratically with flow. Thus, NPSHA is lowest at the maximum flow requirement. Accordingly, it is important to recognize the need to calculate NPSHA (and NPSHR) at maximum flow conditions as well as at maximum liquid temperature, not just at design conditions. Unless supercooled, a pure hydrocarbon liquid is typically in equilibrium with the vapors in a pressure vessel. Thus, increases in vessel operating pressures are almost entirely offset by a corresponding increase in vapor pressure. when this happens

(Eq. 14)

NPSH Margin

The NPSH range is NPSHA minus NPSHR. The Hydraulic Inst. recommends a NPSH range of 3 to 5 feet.[1]

When a new system provides insufficient NPSH margin for optimal pump selection, either the NPSHA must be increased or the NPSHR decreased, or both. To increase NPSHA, one can increase the fluid level, decrease the height of the selected pump, switch to a low NPSHR pump, or cool the fluid. To reduce NPSHR, one can use differently designed impellers or inductors, or use multiple smaller pumps with lower NPSHRs in parallel.

If an existing pumping system has an insufficient NPSH margin, it is too late to use these solutions without making an expensive change. Most of these problems can be traced back to suction flow restrictions (orifices, clogged screens, partially closed valves, etc.) and insufficient liquid levels in the source tank.

power requirement

After the TDH has been calculated, the power requirement can be determined

(Eq. 15)

For kinetic energy pumps,

(Eq. 16)

For positive displacement pumps,

(Eq. 17)

Where

P B = braking power

e = pump efficiency obtained from the pump manufacturer.

In the case of pumps driven by electric motors, the energy consumption can also be estimated

(Eq. 18)

nomenclature

h = height of the liquid column above a reference point p = pressure γ = specific gravity of the liquid ρ f = density of the pumped liquid ρ w = density of water at standard temperature and pressure v = average velocity of the liquid in the pipe g = acceleration due to gravity p = pressure ρ = Density Z = height above a reference point h f = friction loss between points 1 and 2. Q = flow rate d = pipe inner diameter H s = suction height of the pumped liquid p 1 = operating pressure of the suction tank H 1 = height of the liquid suction tank above the reference point of the pump p f1 = Pressure drop due to friction in the suction line

indices

1,2 = places along a pipe

references

1.0 1.1 1.2 1.3 World LNG Source Book 2001. 2001. Des Plaines, Illinois: Gas Technology Inst.

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See also

PEH: pumps

positive displacement pumps

centrifugal pumps

Low_shear_pumps

pump driver