(e.g., 0.00015 for steel)
(e.g., 0.001 for water)
(e.g., 1000 for water)
Unit Conversion: For flow rate (GPM, LPM, m³/s), head (m, ft, psi), diameter and roughness (m, ft), viscosity (Pa·s, cP), and density (kg/m³, lb/ft³).
Reynolds Number Calculation: To determine the flow regime (laminar or turbulent) to select the appropriate friction factor equation.
Colebrook-White Approximation: A suitable approximation of the Colebrook-White equation for the friction factor (f) is used. This avoids the need for the Moody chart lookup.
Turbulent Flow Assumption: The simplified friction factor calculation is valid for turbulent flow (generally Re > 4000), which is common in most pump systems. For laminar flow, a different equation would be needed.
Pump Power Calculation: The pump power calculation now includes a pump efficiency factor (η). You can adjust this value as needed.
The Silent Struggle: When Pumps Don't Speak Your Language
Imagine a bustling factory floor. Machines hum, gears grind, and fluids flow, the lifeblood of the operation. At the heart of it all sits a pump, tirelessly pushing liquid through pipes, a silent workhorse. But what happens when this vital organ falters? What if the flow is sluggish, the pressure erratic? More often than not, the culprit isn't a mechanical failure, but a simple miscommunication – the pump just isn't speaking the system's language. It's a problem of improper sizing.
We've talked about the basics: flow rate, head, friction loss. Every online calculator covers that. But pump sizing is more than plugging numbers into equations. It's about understanding the story your system is trying to tell.
Let's take the case of a brewery. They're not just pumping water; it's a complex dance of wort, beer, and cleaning solutions, each with its own viscosity, temperature profile, and chemical properties. A standard centrifugal pump might handle the initial water stages, but what about the thick, viscous wort during the brewing process? Suddenly, friction losses skyrocket, the pump struggles, and the brewmaster's dream of the perfect IPA turns into a foamy nightmare.
This is where the deeper understanding comes in. It's not just about Darcy-Weisbach; it's about rheology. How does the fluid's viscosity change with shear rate? Is it shear-thinning, shear-thickening, or something in between? A simple online calculator won't tell you that. You need specialized testing, maybe even CFD simulations, to truly understand the fluid's behavior.
And what about the pipes themselves? We often think of smooth, uniform conduits. But real-world systems are messy. They have elbows, bends, valves, and sometimes even unexpected obstructions. Calculating equivalent lengths is a good start, but it's an approximation. What about the biofilm that builds up inside the pipes over time, increasing roughness and restricting flow? That's not in any textbook equation.
Then there's the human factor. Operators might tweak settings, maintenance crews might replace components with slightly different ones, and suddenly, the carefully calculated pump is no longer operating at its sweet spot. It's a dynamic system, constantly evolving, and the pump needs to be able to adapt.
This is where the real artistry of pump sizing comes in. It's not just about picking a pump; it's about designing a system. It's about understanding the fluid's personality, the pipe network's quirks, and the human element's unpredictability. It's about anticipating the unexpected and building in flexibility.
We've built a calculator, yes, but it's not just a black box spitting out numbers. It's a tool for exploration. Play with the inputs. See how viscosity changes things. Experiment with different pipe sizes. Use it to understand the why behind the numbers, not just the what.
Pump sizing isn't a science; it's a conversation. It's about listening to the system, understanding its needs, and choosing a pump that speaks its language. And sometimes, it requires a little bit of magic.
Auto-cad engineering model of four-stage centrifugal pump cross-section.
High-efficiency multistage pump
The multistage pump performance depends on the driving power. It has high-performance characteristics when the variable speed drive system is preferred when compared to the constant drive mechanism. Using the numerical analysis auto cad model shown above consists of four stages with inlet and outlet provision. A single shaft buckled up with the mechanical seal and gearbox included in the design. Impellers preferred for the design is a two-row system which was found to achieve the high radial flow by computer modelling. Computational fluid dynamics is the only way to find the optimal design by numerical simulation for advanced multistage pumps. The 3D model is much more complex for analysis the pressure points fluctuate and deviate the model from the real impeller operations.
The above diagram includes the supporting section and casing section as the common block without any individual parts. This provides an economic advantage in manufacturing and electric power consumption. Inlet and outlet connections are provided on the top section of the pump so that while installation the bends requirements in piping can be avoided. Bends add up the power loss factor in the system.
Handy Multistage Pump Calculator
This calculator is designed to help you calculate the power, speed, and impeller diameter of a multistage pump.
How to Use the Calculator:
1. Enter the flow rate (Q) in cubic meters per hour (m³/h).
2. Enter the head (H) in meters (m).
3. Enter the efficiency (η) as a percentage (%).
4. Enter the number of stages (n).
5. Enter the specific speed (Ns) in revolutions per minute (rpm).
6. Click the "Calculate" button to get the results.
Results:
The calculator will display the following results:
- Power (kW): The power required to drive the pump.
- Speed (rpm): The speed at which the pump operates.
- Impeller Diameter (m): The diameter of the impeller.
Note: This calculator assumes that the pump is operating at a steady state and that the fluid being pumped is incompressible. The results should be used as a rough estimate only and should not be used for final design or purchasing decisions without consulting a qualified engineer or manufacturer's documentation.
Multistage Pump Calculator
High-Performance Multistage Pump Design for Viscous Liquids
Pumping high-viscosity liquids demands substantial power and efficiency. Our multistage pump design leverages variable speed drive systems, surpassing traditional constant drive mechanisms. This innovative approach ensures optimal performance.
Design Overview
Our pump features:
1. Four-stage configuration: Enhances pressure handling and flow rate.
2. Single shaft design: Streamlines maintenance and reduces mechanical losses.
3. Mechanical seal and gearbox: Ensures reliability and efficient power transmission.
Reliable access to groundwater is paramount for countless homes and industries, and submersible pumps are often best preferred for this essential service. But these powerful tools require more than just plugging them in. Maximizing their performance, longevity, and efficiency depends on a holistic approach that spans from careful selection and precise installation to proactive maintenance and effective troubleshooting. This comprehensive guide goes beyond the basics, providing in-depth knowledge and practical advice to empower you to make informed decisions, avoid costly mistakes, and ensure a dependable water supply for years to come. Whether you're a homeowner, a contractor, or an engineer, this resource will equip you with the expertise you need to master the world of submersible pumps. Handy calculation tools are presented below they use parameters (e.g., pipe length, diameter, static lift, required pressure) as input to calculate TDH (Total Dynamic Head) and an estimation of flow rate depending on pipe size. Let's know about the selection of the submersible pump set and how it works.
1. Selection of pump set:
A proper selection of submersible pump sets ensures trouble-free working for a longer duration. The following criteria have to be considered for selection.
Borewell size:
As submersible pump sets are normally installed on bore wells, the diameter of the bore well is the restricting factor in selecting the size of the pump set. The best size of the borewell is a 6 to 7-inch diameter because the pump can be inserted into the bottom of the ground and fixed easily.
Discharge:
The yield of the bore well is an important criterion for pump selection. For overall efficient performance, the rated discharge of the pump should be taken as 80% of the yield of the bore well. It is desirable to obtain a yield certificate from a bore well contractor. Discharge can be around approximately 0.5 hp is 5 gallons per minute. So you do not need to struggle for calculations just take an approximation from the list provided by the manufacturer and select the amount of water you need to fill your overhead tank. Almost all manufacturers provided the same specification because of standard physical if followed for the design of the submersible pump.
Total Head:
To work out the total Head, add static head, drawn down, seasonal variation in water level and the frictional losses in bends, reducers, non-return valve, column pipe and delivery pipe. This is simply other terms that include the height of the discharge outlet of the pipe because the height is directly proportional to the pressure of the liquid at that particular position, the pressure at which the liquid to pumped out the discharge outlet point is termed as the head of the pump.
Total Dynamic Head and Estimated Flow
Motor H.P number of stages:
From the pump selected above and the desired head, select the number of stages and the corresponding H.P/ phase from the performance chart having maximum efficiency at that duty point.
2. Description of submersible pump set:
The motor and pump are together called a pump set and they are explained individually:
The submersible pump set which is wet type will have a motor of type squirrel cage which can be completely filled with cold, clear water. Motors are suitable for operating in a voltage range of 350 to 440 volts in three phases and 180 to 240 volts in the case of a single-phase power supply. If it contains thrust bearing then it can withstand axial thrust loads with minimal wear and tear. A seal ring and sand guard should be provided to protect the pump from the sand and other foreign particles.
Pump:
Submersible pump sets have a mostly centrifugal multi-stage pump, and there are two types depending on the requirements like for high heads radial flow type of pump is used and for high discharge mixed flow type of centrifugal multi-stage pump is used.
3. Installation of Submersible pump:
Motor filling: The position of the motor should be kept vertical. Mostly a water filling plug is provided at the top of the pump casing so that it can be primed with clean, acid-free water. The water should be oil-free and sand-free before pouring into the plug hole. Gently move the motor to and fro and leave it for 10-15 minutes, with the plug holes open so that any air bubble trapped in the winding will escape. Now pour more water to the loss of volume caused by the escaped air bubbles and screw up the two plugs, the motor is to be checked thoroughly for leakage of water before it is installed. The motor is now ready to be coupled to the pump and installed.
Cable Connection and Megger Test: Connect additional cable length to the standard 3-meter cable supplied with the pump.
The selection of the additional cable must be proper to ensure the proper functioning of the pump. The cable - section/size should match the motor power, line length and starting system. To select the correct cable diameter size we must know the details regarding the nominal voltage of the motor, the nominal power of the motor and the supply cable total length details.
To connect the additional cable to the pump cable, cut off and strip the cable ends so that each lead joints are staggered at regular intervals. The colors of the leads which are to be joined together must be identical.
Insert the bottom plug and plastic tube into the pump cable and the top plastic plug must be inserted into the jointing cable. Join each lead and solder properly. Ensure that after jointing approximately 15 mm of intact sheathing lies within the interior of the cable splicing sleeve on each side. After soldering file off the sharp corners on the soldering joints. insulate each joint separately by winding the rubber taps and adhesive tape tightly to at least 2 inches across the joint.
Push the plastic tube over the joints and ensure that it is central. Cap the bottom plug and push it securely into the bottom of the tube. Wind the Adhesive tape tightly around the bottom end of the tube plug and the pump cable, and press firmly to ensure a perfect seal.
suspend the joint vertically so that the bottom end of the tube points downwards. Heat the tar-based compound in a small tin and pour the molten compound into the tube from the top end. Refill the cavity to overcome any shrinkage and allow the compound to cool. Slide the top plug down the pump cable and push it securely into the topside of the tube. Take the adhesive tape and wind tightly over the top plug and tube.
To check the insulation, conduct a megger test with 500v megger, after keeping the joint in water.
4. Operation of Submersible Pump:
Turn on the power supply and verify the voltage indication at the voltmeter. Check whether all three-phase supply voltage is the same or not. If not, do not start the pump.
The direction of Rotation:
The direction of rotation can be changed by interchanging two phases, Higher discharge shows the correct direction of rotation.
Sand Test:
Care should be taken before installing the pump so that the borewell is well-flushed so that it is free from sand and silt. The pump set is suitable for pumping clear cold water with a maximum permissible sand content of 10 gms per cubic meter. A recently installed bored well, submersible pump is to be started with the gate valve on the discharge line partially opened at the initial condition. The underground water should be examined and tested for the percentage of sand content. Sand content in the water is visible in the glass tube, then the pump set should be run continuously with the gate valve on the discharge line partially opened till the sand content of the water comes to a satisfactory level. A noticing action to be considered is that the pump should not be stopped until we observe clear water, i.e. it should not be turned off during pumping sand-contained water. A high level of sand content will cause a premature tear and wear of the pump's internal parts.
Shut -Down Periods:
The pump set must not be left idle for a week or so since it might cause jamming of moving parts. It should be started at least once every week for five minutes. This will ensure that the pump set is ready for service at any desired time.
Operation at Shut Off:
The pump set must not be run for more than three minutes at zero discharge since the pump will get overheated due to the churning of water in the pump. If the low discharge is required at least 25 percent of the maximum discharge must be allowed.
Switching Frequency:
The stand-still time of the pump between switching off and switching on again should be at least five minutes.
5. Troubleshooting submersible pump problems:
For every operation, I have to pour water into the pipe to start the motor to pump water from the underground bore well to the overhead tank.
Causes and remedies:
Failure of NRV (non-return value or check value) on the discharge line of the pump. Check if solid particles are stuck in it, and clean it if possible if not replace the value. It helps to hold the water in the pump casing and suction line after the pump is switched off. This prevents the pump from becoming empty for the next operation. So no need to fill the water again and again.
Maybe the water level in the ground is dropped down and so the suction lift is not possible by the pump. Airlocks will be created in the suction, they are removed when we pour water
Which type of discharge pipe is suitable for the submersible pump to discharge water from a bore well.
selection
Usually, GI pipe is used as a discharge pipe, however, this pipe corrodes quickly due to the water and moisture in the well.
HDPE pipe is corrosion-resistant to the bore well environment and can withstand underground temperatures. However, if there is a need to remove the motor and pump out of the bore well for maintenance there is a chance of jamming. HDPE pipe may stretch by the applied pressure during pull-out and deform its size and shape.
In the world of fluid mechanics, pumps play a vital role in transferring liquids from one place to another. Just as the human heart pumps blood throughout the body, maintaining life and vitality, reciprocating pumps work tirelessly to circulate fluids through industrial systems, keeping them running smoothly and efficiently. Like the rhythmic beating of the heart, reciprocating pumps operate with a steady cadence, using a piston and cylinder arrangement to transfer fluids with precision and reliability. In this post, we'll delve into the operation and performance of reciprocating pumps, exploring the intricacies of their mechanism and what makes them tick.
Theory:-
Imagine a mechanical device that can harness the power of mechanical energy and transform it into hydraulic energy, allowing liquids to flow effortlessly through a pipeline. This device is none other than a pump, a crucial component in various industrial and domestic applications. In essence, a pump is a mechanical workhorse that converts the mechanical energy supplied to it from an external source into hydraulic energy, thereby increasing the energy of the flowing liquid.
Mathematically, this can be represented using vector analysis. Let's consider the velocity vector (v) of the fluid, which can be resolved into two components: the pressure energy vector (P) and the potential energy vector (PE). As the pump imparts energy to the fluid, the pressure energy vector increases, allowing the fluid to flow against gravity and overcome frictional losses. This increase in pressure energy is subsequently converted into potential energy as the fluid is lifted from a lower level to a higher level.
The various pumps can be broadly classified into two types: those that increase the pressure energy of the liquid, such as centrifugal pumps and reciprocating pumps, and those that increase the potential energy of the liquid, such as positive displacement pumps and rotary pumps. Each type of pump has its unique characteristics, advantages, and applications, making them an essential part of various industries, including oil and gas, chemical processing, and power generation.
(i) Positive-Displacement Pumps
Positive-displacement pumps guarantee a precise amount of fluid delivery, regardless of pressure or head. These pumps work by literally pushing or displacing the liquid using a moving member. The reciprocating pump is a classic example, where a piston or plunger moves back and forth, creating a chamber that fills and empties with each stroke.
From a tensor analysis perspective, the flow rate (Q) of a positive-displacement pump is represented by:
Q = (V * N) / (2 * π)
where V is the displacement volume and N is the rotational speed.
Formula
Description
Variables
Q = V × N
Flow Rate
Q = Flow Rate (L/min), V = Displacement per revolution/stroke (L/rev), N = Pump Speed (RPM)
P = (Q × ΔP) / η
Theoretical Power
P = Power (W), Q = Flow Rate (m³/s), ΔP = Differential pressure (Pa), η = Overall efficiency (decimal)
S (%) = ((Qtheoretical - Qactual) / Qtheoretical) × 100
Slippage
Qtheoretical = Theoretical Flow, Qactual = Actual Flow
ηv (%) = (Qactual / Qtheoretical) × 100
Volumetric Efficiency
Qtheoretical = Theoretical Flow, Qactual = Actual Flow
Ps = Absolute pressure at the pump suction inlet (Pa), ρ = Fluid density (kg/m³), g = Acceleration due to gravity (≈ 9.81 m/s²), vs = Average fluid velocity at the suction inlet (m/s), Pv = Vapor pressure of the fluid at the operating temperature (Pa)
Pinlet = Absolute pressure at the pump inlet, hsuction = Suction lift (or suction head)
Qcorrected = Qnominal (1 - (k × log(viscosity)))
Viscosity Correction Factor
Qcorrected = Corrected flow rate, Qnominal = Nominal flow rate, viscosity = Fluid viscosity, k = Constant based on experimental data for the specific pump (range: 0.01 to 0.2)
Flow Rate Calculator (Positive Displacement)
Theoretical Power Calculator (Positive Displacement)
Rotodynamic pumps, also known as dynamic-pressure pumps, rely on angular momentum transfer to increase fluid pressure energy. These high-performance pumps are designed for applications requiring large volumes of fluid at high pressures. Centrifugal pumps are a common example, where an impeller rotates at high speed, imparting energy to the fluid.
From a tensor analysis perspective, the flow rate (Q) of a rotodynamic pump is represented by:
Q = (ρ * g * H * D^2 * N) / (2 * π)
where ρ is fluid density, g is gravitational acceleration, H is head, D is impeller diameter, and N is rotational speed.
Simplified NPSH Available Calculator (Rotary Pumps)
Main Components and Working of a Reciprocating Pump:
A reciprocating pump essentially consists of a plunger and a cylinder where the plunger is enclosed by the cylinder. The cylinder is connected to suction and delivery pipes, each of which is provided with a non-return or one-way valve called a suction valve and delivery valve respectively. The function of a non-return or one-way valve is to admit liquid in one direction only. Thus the suction valve allows the liquid only to enter the cylinder and the delivery valve permits only its discharge from the cylinder. The piston Of the plunger is connected to a crank by means of a connecting rod.
As the crank is rotated at a uniform speed by a driving engine or motor, the piston or plunger moves to and fro (or backward and forward) in the cylinder. When the crank rotates from e =0' to e = 180', the piston or plunger which is initially at its extreme left position (that is, it is completely inside the cylinder), moves to its extreme right position, (that is, it moves outwardly from the cylinder). During the outward movement of the piston or plunger, a partial vacuum (pressure below atmospheric) is created in the cylinder, which enables the atmospheric pressure to act on the liquid surface in the well or sump below, to force the liquid up the suction pipe and fill the cylinder by forcing open the suction valve.
Since during this operation of the pump, the liquid is sucked from below it is known as its suction stroke. Thus at the end of the suction stroke, the piston or plunger is at its extreme right position, the crank is at e = 180' (i.e., at its outer dead center), the cylinder is full of liquid, the suction valve is closed and the delivery valve is just at the point of opening.
Types of Reciprocating Pumps:
The reciprocating pumps can be classified according to the liquid being in contact with one side or both the sides of the piston or plunger; and according to the number of cylinders provided.
According to the first basis of classification, the reciprocating pumps may be classified as:
(i) Single-acting pump.
(ii) Double-acting pump.
If the liquid is in contact with one side of the piston or plunger only, it is known as a single-acting pump. Thus as shown in Fig. a single-acting pump has one suction and one delivery pipe and in one complete revolution of the crank, there are only two strokes-one suction and one delivery stroke. On the other hand, if the liquid is in contact with both sides of the piston or plunger, it is known as a double-acting pump. As shown in Fig. a double-acting pump has two suction and two delivery pipes with appropriate valves, so that during each stroke when suction takes place on one side of the piston, the other side delivers the liquid. In this way, in the case of a double-acting pump in one complete revolution of the crank, there are two suction strokes and two delivery strokes.
According to the number of cylinders provided the reciprocating pumps may be classified as :
(i) Single cylinder pump.
(ii) Double cylinder pump.
(iii) Triple cylinder pump.
(iv) Duplex double-acting pump.
(v)Quintuplex pump.
The function of air vessel: -
The air vessel is a cast iron chamber, which has an opening at the base, through which water can flow, one chamber is fitted on the suction pipe just near to suction valve and one on the delivery pipe just near the delivery valves. Each channel is converted through a small length of pipe. For efficient working, vacuum vessels should be 3 to 5 times the discharge per stroke and the air vessel on the delivery side 6 to 10 times the discharge per stroke.
During the middle of the delivery stroke, when the pump is facing the water into the delivery pipe at a velocity greater than the average, excess water flows into the air vessel and compresses the trapped air in the upper portion of the chamber. At the end of the stroke when water flows into the delivery pipe at a rate less than the average water flows out of the air vessel from the excess amount of water already stored to keep the discharge more uniform. This fluctuating water column causes the acceleration head to be reduced between the pump cylinder and the air vessel, which allows the pump to run at higher speeds. Thus in this way, it saves a large amount of power lost in developing accelerating heads on the suction side, water first collects in the air vessel and then flows in the cylinder on the delivery side. Water first goes to the air vessel and then flows with a uniform velocity. An air vessel provided in a reciprocating pump acts like a flywheel of an engine.
Other functions of an air vessel:-
1. Reduces the possibility of separation and cavitation.
2. Allows the pump to run at high speed.
3. The suction head can be increased by increasing the length of the pipe below the air vessel.
4. A large amount of power is saved due to a low acceleration head.
5. Uniform discharge.
Operating characteristic curves of reciprocating pump:-
The operating characteristic curves indicate the performance of the reciprocating pump are obtained by plotting discharge, power input, and overall efficiency against the head developed by the pump when it is operating at a constant speed under ideal conditions. The discharge of a reciprocating pump operating at constant speed is independent of the head developed by the pump. However, in actual practice, it is observed that the discharge of a reciprocating pump slightly decreases as the head developed by the pump increases almost linearly beyond a certain minimum value with the increase in head developed by the pump. The overall efficiency of this pump also increases with an increase in head developed by the pump.
Determining the Performance of a Reciprocating Pump by Experimentation
Learning Objectives
Calculate the efficiency of the reciprocating pump.
Determine the relationship between efficiency and head.
Aim
To study the performance of the reciprocating pump.
Apparatus
Reciprocating pump test rig
Tachometer
Stopwatch
Description of Apparatus
The apparatus consists of a single-cylinder, double-acting reciprocating pump mounted on the sump tank. The pump is driven by an AC motor with a stepped cone pulley. An energy meter measures electrical input to the motor. A measuring tank is provided to measure the discharge of the pump. The pressure and vacuum gauges were provided to measure the delivery pressure and suction vacuum respectively.
Specifications
Component
Specification
Reciprocating Pump
Bore diameter (D): 38.11 mm, Stroke length: 45.3 mm, Double-acting with air vessel on discharge side, Suction pipe diameter: 31 mm, Delivery pipe diameter: 25 mm
AC Motor
3 HP, Speed variations controlled by a stepped pulley
Measuring Tank
Dimensions: 400 x 400 x 450 mm
Sump Tank
Dimensions: 600 x 900 x 600 mm
Piston Rod
Diameter: 9.52 mm
Measurements
Pressure Gauge: 0 to 7 kgf/cm² for discharge pressure
Vacuum Pressure: 0 to 760 mm of Hg for suction pipe
3-Phase Energy Meter: for motor input measurement
Procedure
Fully open the discharge valve.
Start the pump and observe the discharge.
For a particular discharge, note down the discharge head (Hd), suction head (Hs), and time required for 10 liters of water collection.
Also, note down the time taken for 5 revolutions of the energy meter and the speed of the pump (N).
Repeat step 3 at different discharge pressures and tabulate the values.
Industrial Vacuum Pumps: A Crucial Component in Diverse Manufacturing Processes
In various industrial sectors, including the production of sensitive paper products and the intricate refining of petrochemicals, vacuum pumps operate as indispensable yet often overlooked machinery. These versatile devices fulfill a vital function in a multitude of processes, ranging from the maintenance of precise pressure in distillation columns to the secure transportation of hazardous liquids.
This comprehensive guide provides an in-depth examination of industrial vacuum pumps, with a particular emphasis on dependable and efficient water ring vacuum pumps. By exploring the fundamental principles, operational characteristics, and applications of these pumps, this guide aims to elucidate the significance of vacuum pumps in modern industrial processes.
A vacuum pump having a capacity range from 500 cubic meters per hour to 5400, which can attain a maximum vacuum of up to 670mm of Hg used widely in paper, sugar, and petrochemical industries. The operating procedure varies depending on the type they are driven but the concept is the same for most of them. The water ring vacuum pump operation is somewhat easier to understand and it can be installed with less effort, a vacuum pump is installed at the front of the streamline which is used to create a vacuum in a distillation column. As it works on the principle of creating negative pressure, highly concentrated acids and liquids which are hazards are transported by creating a vacuum in the respective vessel with the help of a vacuum pump which is in contrast to a centrifugal rotary pump(which creates positive pressure ) It has a set up as
Vacuum pump
Base frame
Coupling set
Electric motor
Vacuum gauge
Automatic drain valve
Non-return valve
Petcock (Air vent cock)
Water on/off valve (Ball valve)
Water regulation valve (stopcock)
Safety valve
Pressure gauge
These parts are standard for all vacuum pumps.
Start-Up of Vacuum Pump:
In this case of a pump, the rotation direction will be clockwise when viewed from the motor-driven end. In a pump of normal execution, the suction line is fitted with a non-return valve and the silencer is connected to the discharge line.
Before starting the electric motor turn the shaft by hand to ensure the pump's free run.
Start the motor and check the direction of rotation. Water supply should be given only when the pump is started.
Now open the ball valve which water is passed into the casing of the pump at least with a pressure of 1.5kg/cm2.
The pump starts to build up the vacuum in its suction line which is indicated by the pressure gauge, do not open the suction valve immediately after starting the pump, and if a rattling sound is observed slightly open the air vent cock on the discharge side to remove the air locked inside the casing.
Fix the water supply flow rate which acts as a ring in the vacuum pump casing.
Open the suction valve slowly to prevent the sudden load on the pump and motor.
STOPPING:
Close the water supply line and ensure that no water flows into the casing
Close the suction valve
Stop the motor
MAINTENANCE:
Grease to be filled in bearing housing twice in a month if it runs 14 to 16 hours per day
Alignment of the pump shaft and motor shaft be checked once a month this will increase the pump life
Remove the scaling formed by the supply water. The range of water hardness must be around 50-500ppm.
TROUBLESHOOT:
If the pump jammed: fill the pump with diesel or kerosene and allow for 24 hr most cases the problem will be solved if not loosen the nuts of the casing. Create a gap between the casing and the casing cover. Rotate the shaft with a free hand which describes the formation of any scaling in the pump.
If sufficient vacuum is not developed:
Discharge line chock.
Water supply blocked or not enough pressure.
Gland leak (can be found by soap test)
Automatic drain valve leak.
Rattling sound: open the air and release cock which stops the noise.
Mathematical Models and Formulas:
Areas Where the Calculators provided here Would be Helpful in four areas:
Vacuum Pumpdown Time Estimator
A common challenge is to know how long it will take for a vacuum pump to evacuate a system to a desired vacuum level. Based on the system volume, pump displacement (pumping speed), and target vacuum level we can calculate pump-down time.
Formula: t = (V / S) * ln(P₀ / P₁)
t = Pumpdown Time (seconds).
V = System Volume (liters).
S = Pumping speed (liters/second)
P₀ = Initial Pressure (Torr or mbar).
P₁ = Target Pressure (Torr or mbar).
ln = Natural logarithm
Important note: This simplified equation assumes a constant pumping speed, and doesn't take into account the performance of pumps in deeper vacuum regions
Leak Rate Calculator
Quantifying leaks in a vacuum system is essential for troubleshooting. we can estimate the leak rate based on the pressure rise over time in a closed system.
Well, the operators, trainees, and freshers who just moved into the process industries will have their introduction, to fluid transporting devices which are mainly "PUMPS". All chemical process industries have the basic and the most optimized device known as a centrifugal pump. It is a superb piece of equipment where most of the fluids which are viscous and coarse form are handled easily and it is cheaper when compared to other pumping devices, even though maintenance cost is much lesser than reciprocation pumps. When coming to its standard operating procedure, there is a sequence of steps to be followed for every centrifugal pump. which may vary in some situations based on design but mostly the following procedure is well practised:
The standard operating procedure to operate the centrifugal pump is:
1.The suction valve of the pump is to be opened which causes the fluid to flow to the impeller and fill the volute of the centrifugal pump.
2.Open the vent valve which is on the discharge line before the discharge valve of the centrifugal pump which causes all air to move out of the casing and fill with the pumping fluid only.
3.When some quantity of the fluid comes out from the vent valve close the valve.
4.Now open the bypass valve of the discharge valve which is near or side of the discharge valve on the discharge line.
5.Now start the pump and let it attain its capacity in the pressure gauge on the discharge line.
6.When the pressure gauge is stable it is time to open the discharge valve of the centrifugal pump.
These steps are considered the standard operating procedure for most of the centrifugal pumps in chemical industries.
Note: check the periodical maintenance logbook to confirm the cleaning of the strainer in the suction line and fitted back, to protect the impeller from damage. Know what parts a centrifugal pump is made off
Centrifugal pump diagram
Operation Theory of centrifugal pumps:-
Centrifugal pumps are classified as a rotary dynamic type of pumps in which a dynamic pressure is developed which enables the lifting of liquids from a low datum height source to a higher position. The basic principle on which a centrifugal pump works is that when a certain mass of liquid is made to rotate by an external force, it is thrown away from the central axis of rotation and a centrifugal head is impressed which enables it to rise to a higher level. Now if more liquid is constantly made available at the centre of rotation, a continuous supply of liquid at a higher level may be ensured. Since in these pumps, the lifting of the liquid is due to centrifugal action, these pumps are called centrifugal pumps. In addition to the centrifugal action, as the liquid passes through the revolving wheel or impeller, its angular momentum changes, which also results in increasing the pressure of the liquid.
According to the general direction of the flow of liquid within the passage of the rotating wheel or impeller, the rotodynamic pumps are classified as
(i) Centrifugal pumps,
(ii) Half axial or screw or mixed flow pumps,
(iii) Axial flow or propeller pumps.
In the impeller of a centrifugal pump, the liquid flows in the outward radial direction, while the flow of liquid in a propeller pump impeller is in the axial direction, parallel to the rotating shaft. The mixed flow pump impeller has an intermediate form so that the flow of liquid is in between the radial and axial directions. However, no rigid boundaries separate these three types of pumps, and often all three types of pumps are called centrifugal pumps.
In general, all the rotodynamic pumps closely resemble the reaction type of hydraulic turbines and they may be regarded as reversed reaction turbines. Thus the action of a centrifugal pump is just the reverse of a radially inward flow reaction turbine. Similarly, the axial flow pumps are the reverse of propeller or Kaplan turbines and the mixed flow pumps are the reverse of mixed flow type turbines such as the Francis turbine. In the present chapter, only centrifugal pumps have been described.
The main advantage of a centrifugal pump is that its discharging capacity is very much greater than that of a reciprocating pump which can handle a relatively small quantity of liquid only, A centrifugal pump can be used for lifting highly viscous liquids such as oils, muddy and sewage water, paper pulp, sugar molasses, chemicals etc. But a reciprocating pump can handle only pure water or less viscous liquids free from impurities as otherwise, its valves may cause frequent trouble. A centrifugal pump can be operated at very high speeds without any danger of separation and cavitation.
As such it can be coupled directly through flanged coupling to the electric motor. The maximum speed of a reciprocating pump is limited by the considerations of separation and cavitation. As such reciprocating pumps can be operated at low speeds only and for that these pumps are mostly belt-driven. The maintenance cost of a centrifugal pump is low and only periodical checkup is sufficient. But for a reciprocating pump, the maintenance cost is high because the parts such as valves etc. may need frequent replacement. However, a reciprocating pump can build up very high pressures as high as 69 x 106 N/m2 {700 kg(f)/cm2} or even more and hence these pumps are used for lifting oil from very deep oil wells.
COMPONENT PARTS OF A CENTRIFUGAL PUMP
The main component parts of a centrifugal pump are described below:
(i) Impeller. It is a wheel or rotor which is provided with a series of backward curved blades or vanes. It is mounted on a shaft that is coupled to an external source of energy (usually an electric motor) which imparts the required energy to the impeller thereby making it rotate.
The impellers may be classified as.
(a) shrouded or closed impeller,
(b) semi-open impeller; and
(c) open impeller,
The closed or shrouded impeller is that whose vanes are provided with metal cover plates or shrouds on both sides. These plates or shrouds are known as crown plates and lower or base plates The closed impeller provides better guidance for the liquid and is more efficient. However, this type of impeller is most suited when the liquid to be pumped is pure and comparatively free from debris.
If the vanes have only the base plate and no crown plate, then the impeller is known as a 'semi-open type impeller'. Such an impeller is suitable even if the liquids are charged with some debris.
An 'open impeller' is one whose vanes have neither the crown plate nor the base plate. Such impellers are useful in the pumping of liquids containing suspended solid matter, such as paper pulp, sewage and water containing sand or grit. These impellers are less liable to clog when handling liquids charged with a large quantity of debris.
(ii) Casing. It is an airtight chamber which surrounds the impeller. It is similar to the casing of a reaction turbine. The different types of casings that are commonly adopted are described later.
(iii) Suction Pipe. It is a pipe that is connected at its upper end to the inlet of the pump or to the center of the impeller which is commonly known as the eye. The lower end of the suction pipe dips into liquid in a suction tank or a sump from which the liquid is to be pumped or lifted up.
The lower end of the suction pipe is fitted with a foot valve and strainer. The liquid first enters the strainer which is provided to keep the debris (such as leaves, wooden pieces and other rubbish) away from the pump. It then passes through the foot valve to enter the suction pipe. A 'foot valve' is a non-return or one-way type of valve that opens only in the upward direction. As such the liquid will pass through the foot valve only upwards and it will not allow the liquid to move downwards back to the sump.
(iv) Delivery Pipe. It is a pipe that is connected at its lower end to the outlet of the pump and it delivers the liquid to the required height. Just near the outlet of the pump on the delivery pipe, a delivery valve is invariably provided. A delivery valve is a regulating valve that is of sluice type and is required to be provided in order to control the flow from the pump into the delivery pipe.
WORKING OF CENTRIFUGAL PUMP
The first step in the operation of a centrifugal pump is priming. Priming is the operation in which the suction pipe, casing of the pump and portion of the delivery pipe up to the delivery valve are completely filled with the liquid which is to be pumped so that all the air from this portion of the sump is driven out and no air pocket is left. It has been observed that even the presence of a small air pocket in any of the portions of the pump may result in no delivery of liquid from the pump.
The necessity of priming a centrifugal pump is because the pressure generated in a centrifugal pump impeller is directly proportional to the density of the fluid that is in contact with it. Hence if an impeller is made to rotate in the presence of air, only a negligible pressure would be produced with the result that no liquid will be lifted up by the pump. As such it is essential to properly prime a centrifugal pump before it can be started. The various methods used for priming a centrifugal pump are discussed later.
After the pump is primed, the delivery valve is still kept closed and the electric motor is started to rotate the impeller. The delivery valve is kept closed to reduce the starting torque for the motor. The rotation of the impeller in the casing full of liquid produces a forced vortex which imparts a centrifugal head to the liquid and thus results in an increase of pressure throughout the liquid mass. The increase of pressure at any point is proportional to the square of the angular velocity and the distance of the point from the axis of rotation. Thus if the speed of the impeller of the pump is sufficiently high, the pressure in the liquid surrounding the impeller is considerably increased.
Now as long the delivery valve is closed and the impeller is rotating, it just churns the liquid in the casing. By opening the delivery valve the liquid is forced to flow out from the pump casing outlet portion. At the eye of the impeller due to the centrifugal action, a partial vacuum is created. This causes the liquid from the sump, which is at atmospheric pressure, to rush through the suction pipe to the eye of the impeller thereby replacing the liquid which is being discharged from the entire circumference of the impeller. The high pressure of the liquid leaving the impeller is utilized to flow the liquid to the higher end through the delivery pipe.
As the liquid flows through the rotating impeller it receives energy from the vanes which results in an increase in both pressure and velocity energy. As such the liquid leaves the impeller with a high absolute velocity. So that the kinetic energy corresponding to the high velocity of the leaving liquid is not wasted in eddies and the efficiency of the pump thereby lowered, this high, velocity of the leaving liquid must be gradually reduced to a lower velocity of the delivery pipe, so that the larger portion of the kinetic energy is converted into useful pressure energy.
Usually, this is achieved by shaping the casing such that the leaving liquid flows through a passage of gradually, expanded area, the gradually increased cross-sectional area of the casing also helps in maintaining uniform velocity of flow throughout because as the flow proceeds from the tongue T to the delivery pipe, more and more liquid is added from the impeller. Different types of casings are adopted for this purpose and based on the type of casing used; the centrifugal pumps are classified into different types as described in the next section.
Centrifugal Pumps Operation and Selection
Performance of Pumps – Characteristic Curves:-
A pump is usually designed for one speed, flow rate and head, but in actual practice, the operation may be at some other conditions of head or flow rate and for changed conditions, the behavior of the pump may be quite different. To predict the behavior and performance of the pump under varying conditions tests are performed and the results of the test are plotted. The curves are called characteristic curves
(a). Main and operating characteristics:-
To obtain the main characteristic curves of the pump, it is operated at different speeds. Each speed rate of flow discharge is varied using a delivery valve and different values of manometric head Hm, shaft power P and overall efficiency Eo, are measured or calculated. The same operation is repeated for different speeds of the pump. Then Hm Vs Q, P Vs Q and Eo Vs Q curves for different speeds are plotted, so that three sets of curves are obtained, which represent the main characteristics of the pump.
Specific Speed Calculator
Affinity Laws Calculator
Multi-Stage Pump Head Calculator
Pump Efficiency Calculator
(b). Constant efficiency curves:-
The iso-efficiency curves facilitate the direct determination of the range of operations of a pump with particular efficiency.
Cavitation Margin Calculator
System Curve Calculator
Mathematical Models and Formulas
Formula
Variables
Specific Speed (Ns)
Ns = (N * √Q) / (H^3/4)
Ns = Specific speed (dimensionless), N = Pump speed (RPM), Q = Flow rate (gpm), H = Total Dynamic Head (feet)
Specific Speed (Nq)
Nq = (N * √Q) / (H^3/4)
Nq = Specific speed (dimensionless), N = Pump speed (RPM), Q = Flow rate (m³/hr), H = Total Dynamic Head (meters)
