beginners guide

Introduction

Every industry today requires a pump somewhere in its operation. From food processing to oil wells, pumps play a critical role in the production and maintaining our standard of living. Pipes carry the fluid, but pumps supply the energy to move it. Because the piping and pumps work together, they must be thought of and designed as an integrated system. Change one part, and the system can become less efficient. In this Beginner’s Guide to Pumps, we attempt to keep the Information basic and non-technical as possible. Bear in mind that pumping systems are highly technical in nature. Every length of pipe, elbow, valve, the height of the pump above or below the reservoir, fluid viscosity and inside diameters of all equipment effect the optimal discharge flow for the system. This guide covers the short history of pumps to see how they evolved over time. We then cover the basic parts, Types of Pumps and the industries that use them. Lastly, we include some basic troubleshooting topics. We hope that you find this guide useful. When it comes time to plan for a new pumping system or repair an existing one, you can rely on the
experts at All Pumps to get the job done right the first time… every time.

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HOW PUMPS WORK

Pumps work by creating a vacuum in which ambient air pressure forces the liquid. All pumps work by creating areas of low pressure. In a centrifugal pump, centrifugal force accelerates the water to the outside of the impeller creating a low pressure at the eye or centre of the impeller. With reciprocating pumps, the upstroke of the plunger or piston creates a vacuum. In gear pumps or lobe pumps, as the teeth or lobes mesh then come apart, a vacuum is created. The difference in pressure creates suction. A liquid under higher pressure will move to an area of lower pressure.

General Arrangement

Parts
#Description
1Volute Casing
2Wear Ring
3Impeller
4Screw Plug
5Mechanical Seal
6IEC Standard
Motor
7Adapter
8Slinger
9Shaft
10Impeller Nut
General Arrangement

PRESSURE TERMINOLOGY FOR PUMPS

Atmospheric Pressure

At sea level, air pressure exerts a pressure of 14.7 psi all around us. By placing one end of a tube in water and applying a perfect vacuum to the other end, that 14.7 psi could hold a  Column of water 33.9 feet high. However, this is only attainable at sea level and with a perfect vacuum. Centrifugal pumps can lift water no more than 26 feet at sea level because the pressure drops off approximately 2 feet for each 1000 feet of altitude above sea level.

Head – Head refers to the height at which a pump can raise a fluid and can be calculated from H (metres)= pressure in kPa/ (9.8 x specific gravity).
Static Suction Head – The vertical distance between the centre line of a pump and the level to which the liquid is pumped.
Suction Lift – The distance between the level of the where the liquid enters the suction line to the height of the centre line of the pump when the pump is higher than the reservoir.
Vacuum – Defined as any pressure lower than atmospheric. Each pump creates a vacuum into which fluids flow under atmospheric pressure.

Pumps create low pressure or suction in a variety of ways and define the type of pump. Pumps that rotate use centrifugal force to accelerate the fluid, creating low pressure in the centre of the impeller. Positive displacement pumps use plungers, pistons or diaphragms to displace water and create a vacuum using a linear reciprocating motion of a piston moving in and Out of a cylinder.

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PUMP PERFORMANCE

Pumps have strict tolerances and precise conditions under which they must operate to generate the Best Efficiency Point or BEP. Every pump has a chart showing the performance curves and how to attain the BEP. Pump manufacturers calculate performance curves with a pressure gauge and a flow meter connected to the discharge port to find the optimal configurations of piping, type of fluid and head. The discharge capacity can be calculated for any head.

Discharge Quantity

Considerations for BEP

Pump performance factors include:
• How high the pump will sit above the water source (static suction head).
• How high the discharge end is above the pump (static discharge head)
• Determine what the discharge capacity at gallons per minute (GPM).
• Friction losses to fluid viscosity, type and length of hose or pipe.
• Altitude above sea level where the pump will operate.
• Discharge Head or height of the discharge above the pump.
• Restrictions, couplers, elbows and valves.
As you can see, there are several forces acting upon a pump that directly affects its performance. Each
force has a mathematical calculation that helps define the BEP for each pump. Consider a manufacturer’s
performance curves to be your mathematical cheat sheet for helping you select and properly install the right
pump for your application.

BASIC PARTS OF PUMPS

Although pumps come in all shapes, sizes and configurations, most pumps contain five basic components:

The Casing – this is the outer shell or housing that encases the pump.

Fluid Displacement Device – The two main ways of moving fluid are centrifugal and positive displacement.
In centrifugal pumps, impellers are the rotating discs with fins or vanes attached. They spin rapidly
accelerating the fluid outwards to the discharge port. Positive displacement pumps use different types of
pistons, gears, lobes or screws to pump fluids.

Bearings – a mechanical support that allows continuous rotation of the impeller, reduce the rotational
friction and support the loads in other pump assemblies.

The Hub – the central part of a wheel attached to the bearing assembly. It is the source of power for impeller
rotation in centrifugal pumps.

The Seal – protects the bearing assembly from excess grease loss and contamination. Seals also keep fluids
inside the pump from leaking while allowing the shaft to spin or reciprocate depending upon the pump.

centrifugal-water-pump-components

Centrifugal Water Pump Components

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Positive Displacement Water Pump Components

INDUSTRIES AND APPLICATIONS FOR PUMPS

We find pumps in every area of our modern lives. They are essential equipment for manufacturing the goods we take for granted. From running water to the box of cereal on the table, they all require pumps as part of the process.

Four general industries that rely on pumps are:
• Industrial
• Mining, Oil & Gas
• Building and Construction
• Food Manufacturing

Within each industry, there are many variations of pumps depending upon the amount and type of fluid they move. Let’s look at some examples for each industry.

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Industrial

Industrial pumps are typically part of an assembly process. These pumps move liquids from a storage tank to be mixed with other components like a chemical process or directly applied to a part such as paint. Industrial pumps must be built to withstand highly corrosive or volatile chemicals, extremely high or low temperatures, high pressure and constant use. Pump materials and construction vary depending upon the liquids they handle and their environment. Pumps used for industrial purposes include both centrifugal pumps and positive displacement pumps.

Mining, Oil & Gas

Most mining operations are always battling rising water from underground sources. Mining pumps must be durable enough to pump not only water but mud and rocks that get sucked into the intake. These pumps are “Trash” or “Slurry” pumps built to let small stones pass through the pump without damaging the impeller. The oil and gas industry uses a variety of pumps due to the different densities of fluids such as crude oil, distillates, gas and slurries. In drilling operations, cement or mud is pumped around the well casing to hold the pipe in place and seal the well. Crude oil is typically high viscosity and very hot when pumped to the surface. Along with the oil is a variety of corrosive and toxic gasses such as H2S or Hydrogen Sulphide. The gas must be separated and pumped to a holding tank or pumped to a flare boom where it is released and burned. H2S will corrode iron aggressively, so these pumps are made of other materials.

slurry-pump-bgn-manual
submerisible-pump-bgn-manual

Building and Construction

If you live or work in a building higher than two storeys, you can thank a pump for the water pressure. Every tall building uses pumps to push water to the top and to pressurize fire water systems. Pumps also move sewage water to the central sewer lines.

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Food Manufacturing

Every bottle of sauce or oil found in a grocery store requires a food-grade pump for production and packaging. Food manufacturing facilities require pumps for most processes. For example, in fresh vegetable production, the cut vegetables undergo sanitisation by pumping through a chlorinated closed flume system.

The canning industry requires pumps that handle live steam and boiling liquids such as soup and stews. For buildings handling frozen food, cryogenic pumps handle liquid nitrogen or other pressurized gas at below freezing temperatures.

Pumps in the food industry are not limited to liquids. They must move powders, granulated solids, whole grains and finished cereals all without damaging the products.

examples-of-food-grade-pumps

Examples of Food Grade Pumps

TYPES OF PUMPS

Basic Pump Configurations

Pumps are categorized by the way they move the fluid, and the two main categories are Rotodynamic and Positive Displacement.

Rotodynamic pumps use centrifugal force to move liquids and are commonly called Centrifugal pumps. Positive Displacement pumps displace a known quantity of liquid with each revolution of the pumping elements and have two major sub-categories, Reciprocating and Rotary. These categories are further classified based on the way they move the fluid. The outline below shows the basic breakdown of pump classifications by design.

Positive Displacement pumps work best with a high viscosity application as a centrifugal pump becomes very inefficient at even modest viscosity. The acceptable viscosity ranges for centrifugal pumps depends on pump size.

• Rotodynamic
— Centrifugal
• Horizontal Split Case
• Magnetic Drive
• Self-Priming
• Single Stage, End Suction
• Slurry Pumps
• Submersible Pumps
• Dry Pit Submergible Pumps
• Vertical Multi-Stage
• Vertical Turbine

• Positive Displacement
— Reciprocating
• Diaphragm
• Duplex
• Multiplex
• Piston or Plunger
— Rotary
• Gear
• Lobe
• Peristaltic Pumps
• Progressive Cavity Pumps
• Screw Vane

Rotodynamic-Pump
positive-displacement-pump

Another difference between Centrifugal and Positive Displacement pumps is how they discharge their contents. Displacement pumps typically have a pulsating flow or periods when there is no flow whereas rotodynamic pumps have a continuous flow.

Other factors in pump classification include:
• Whether the fluid delivery is constant or variable at a given speed
• Type of application
• Materials from which they are constructed
• Type of fluids or materials they move
• Structural features

Although the pipes that go from the source to the pump are called “suction lines,” pumps do not “suck” liquid; they push it. The pump creates a vacuum into which the fluid flows forced by atmospheric pressure, the same pressure when using a drinking straw or vacuum cleaner. For example, centrifugal pumps create a low pressure in the eye of the impeller and air pressure pushes the fluid into the pump via the suction line. Now let’s look at each pump type in more detail.

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Centrifugal Pumps

Horizontal Split Case pumps have a design feature that allows for the upper casing to be unbolted and removed for easier inspection, maintenance, or replacement of the impeller,  without disconnecting the piping or altering the alignment. This access is especially important for heavy industrial pumps and tight fitting areas.

Split case pumps can contain multiple impellers, or stages, to generate higher head. Bearings on both ends of the shaft support and provide balance for the impellers. Double suction pumps use closed impellers with two opposing eyes, each receiving half the flow further balancing axial thrust.

The horizontal split case pumps are best suited for applications that require high capacities and high head where the fluid contains no solids such as boilers and cooling towers.

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Magnetic Drive pumps coupled to the motor magnetically, rather than by a direct mechanical shaft. These pumps are critical in manufacturing processes to transfer highly corrosive liquids. Facilities requiring a continuous process benefit by using magnetic because there are no seals to replace or leak

Magnetic-drive
Magnetic Drive

However, Mag drive pumps only work with liquids that have no suspended solids. Although they are more expensive than pumps with mechanical seals, over the life of the pump, there will be considerable savings from reduced maintenance and production downtime.

Self-Priming Pumps are a design of centrifugal pumps that use an air-water mixture to reach a fullyprimed pumping condition. By using fluid left in a reservoir, the impeller forces out the air from the casing, creating a vacuum and suction that primes the pump. The advantage is the pump stays in areas that are dry and easy to access for maintenance.

Self-priming pump applications including sewage, construction dewatering, slurries and flood control. Some pumps can handle solids up to three inches.

self-priming

Single Stage, End Suction Pumps are the most common centrifugal pump. The are available in ll sizes, impeller types and discharge pressures. They are best at pumping low viscosity fluids without solids.

Fluid enters the pump in line with the drive shaft at the opposite end of the motor or driver. The fluid contacts the eye of the spinning impeller, and the vanes accelerate the fluid radially outward 90 degrees to the discharge outlet. The pressure of the fluid increases due to the centrifugal force of the impeller, but the amount of pressure depends on the type of impeller, the size of the suction and discharge nozzles and the rpm (speed) of the shaft.

single-stage-end-suction

Slurry Pumps are the workhorses of the mining industry. They are robust pumps usually constructed from thick cast iron to withstand abrasive fluids mixed with solids like concrete, mud and other viscous, abrasive materials. The casing has a replaceable rubber coating or lining to protect the metal from damage. The impeller vanes are shorter to allow passage of stones and solids without damaging the system.

slurry-pumps

Submersible Pumps stay below the surface of the fluids they pump, typically inside tanks or wells. The pump motor is hermetically sealed and close-coupled to the pump end. They have the advantage of being self-priming but can be more problematic to maintain. Submersible pumps are also called stormwater pumps, sewage pumps and septic pumps and effectively used in building services, commercial, domestic, municipal, rural, industrial, and rainwater reuse for subsoil water, stormwater, sewage, grey water, black water, trade waste, rainwater, bore water, chemicals and food waste. They come in a variety of sizes and impeller types depending on the fluid viscosity, type of solids to be processed and pumped.

Submersible-Pump-Kits

The Dry pit submersible pump differs from a typical submersible in that it can run both above and below the level of the fluid. They are designed to de-water areas that only flood occasionally. A conventional submersible would overheat, but dry pit pumps have the motor housing filled with a cooling oil.

Vertical Multi-Stage Pumps are centrifugal pumps with multiple impellers placed in series on the same shaft in a single casing. The fluid increases in pressure as it leaves each impeller chamber or stage. The more stages the pump has, the higher the discharge pressure.

Vertical Multi-stage pumps require less space for installation. The pump uses only one motor to power multiple stages and is best suited for boosting pressure to any clear liquid. Practical applications include increasing water pressure in buildings, light industrial water supply, washing and cleaning systems, such as car washes, irrigation systems and providing cooling lubricants to machine tooling processes.

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Vertical Turbine Pumps primarily to pump water from deep wells in mining and for agriculture irrigation where the high head and pressure is required. The unit consists of a motor on top, the discharge head below that and one or more flanged columns that house the drive shaft and one or more impeller bowls or stages. There is usually a type of strainer at the suction end to filter out stones and debris.

Vertical turbine pumps are used for small, single pump commercial applications as well as large, multipump municipal water supply systems. One disadvantage is the high headroom required for installation and maintenance. The advantage of these pumps is that they have a small footprint, are easily customised and very efficient
for high head, low flow applications.

Positive Displacement Pumps

A positive displacement pump operates by drawing in a fluid, filling a cavity and then displacing the same volume of fluid, delivering a constant amount of liquid for each cycle that the pump makes regardless of the discharge pressure or head.

Positive displacement pumps differ from centrifugal pumps in that the volume of the chamber changes, driving the fluid. When the plunger draws back the volume increases, creating a vacuum and the cylinder fills. Pushing on the plunger has the opposite effect and forces the fluid out. The mechanical devices that move the fluid in a positive displacement pump can be a plunger, piston, diaphragm, gears or intermeshing lobes.

PD Pumps are the designed for use where there are solids or abrasive material suspended in the fluid. High velocities within a centrifugal pump will wear out the impeller and casing rapidly if they pump anything but low viscosity clear fluids. Positive displacement pumps run at lower internal speeds and should be a more economical option for viscous or abrasive liquids.

PD Pumps are the best choice if:

• The smallest available centrifugal pump needs to operate at a flow less than 50% of best efficiency flow.
• The fluid is high viscosity.
• You need to produce higher heads or pressures at a more economical price.
• You require a near constant flow that makes it possible to match the flow to the process requirements.
• For metering applications.

positive-displacement-pumps

Reciprocating pumps use a crankshaft-connecting rod mechanism the same way it works on the engine in a car. It converts the crankshaft’s rotary movement into straight or linear movement of the piston.

There are three moving parts including the inlet valve, the plunger or piston and the outlet or discharge valve. As the piston retracts, ambient air pressure forces the fluid in through an inlet check valve to fill the vacuum left by the piston.

As the piston reverses the cycle, pressure closes the inlet check valve, and the outlet check valve opens discharging the fluid. The volume of fluid remains constant with each revolution of the crank, but pump configuration determines pressure and system flow. Pump shaft speeds are relatively low, requiring speed reduction from the motor or driver to the pump shaft.

reciprocating-pumps

Diaphragm Pumps also, called Membrane Pumps, Diaphragm Pumps use a flexible membrane to create low and high pressure by flexing in and out of a chamber. Check valves direct the flow of liquid in and out of the chamber with each reciprocating cycle of the diaphragm. These pumps work well pumping high viscosity fluids such as sludges and slurries containing solid materials. They can reach discharge pressures up to 1,200 bars.

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Air-operated double diaphragm (AODD)

Duplex Pumps the official name of the Duplex Pump is Direct Acting Reciprocating Steam Pump. Invented by Henry R. Worthington in 1840 they are still used today. However, the steam has been replaced with compressed air.

Duplex pumps have two steam and two water cylinders that work in tandem. Compressed air enters the top of the cylinder on one side or the other depending on the motion of the
rocker arm over the intake ports creating constant lateral motion of the pump plunger. This is an efficient arrangement as there are no “dead spots.” With the two cylinders about 1/4 cycle out of synchronization, there is always a piston under pressure during the entire cycle.

The duplex pump is used where a high volume of water is required without the threat of backwash. Backwash could contaminate large freshwater storage tanks and render the system unfit for use. They are commonly used in oil drilling to cool drilling heads as well as to flush out the boring holes. Duplex Pumps also work well for transferring low viscosity fuels like
heating oil.

duplex-pumps

Multiplex Pumps Simply put, Multiplex pumps are a series of plunger pumps with a common power end and fluid end. The power end contains a crankshaft in a crankcase with connecting rods connected to crossheads instead of pistons to alleviate sideways forces to the piston. The fluid end includes individual plungers, each having different spring loaded intake and discharge check valves.

Multiplex pumps provide higher flow rates at lower pressures due to the load limits on the crankshaft and primarily used in oil field applications.

Regardless of the well pressure, multiplex pumps can move significant amounts of fluid.

multiplex-pumps

Piston and Plunger Pumps Both Piston and Plunger Pumps work with the linear motion displacing fluid inside of a cylinder. The difference is that the seal on the piston moves with the piston contacting the cylinder wall to create a seal. The plunger on a Plunger pump passes through a stationary seal and will generate higher pressure than piston pumps.

There are two types of piston pumps, Lift and Force. In a lift pump, it takes three strokes to complete the cycle. The first stroke or upstroke of the piston draws water, through a valve, into the lower part of the cylinder. With the second or downstroke, water passes through valves in the piston, filling the upper portion of the cylinder. On the third or upstroke, water discharges from the top part of the cylinder via a spout.

Force pumps need only an upstroke to fill the cylinder and a down stroke to force the fluid out.

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Rotary Pumps

Because of their design, Rotary pumps can produce more fluid than reciprocating pumps of the same weight, and they are self-priming. The pump classifications under Rotary pumps are Gear, Lobe, Peristaltic and Screw or Moving Vane.

Rotary pumps are capable of pumping more fluid than reciprocating pumps of the same weight. Unlike the centrifugal pump, the rotary pump is a positive-displacement pump meaning that for each revolution of the pump, a fixed volume of fluid is moved regardless of the resistance against which the pump is pushing.

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Gear Pumps Rotary Gear Pumps consist of at least one or two sets of rotating gears with intermeshing teeth. As the teeth separate, they create a partial vacuum which is filled by the fluid. When the gears continue to rotate, the fluid becomes trapped and carried around the casing to the discharge port of the pump. Gear pumps can be external or internal.

Internal Gear Pumps handle low and high viscosity liquids from solvents and fuel oil to asphalt and adhesives. The viscosity range is 1cPs to over 1 million cPs. Moreover, they perform well pumping high-temperature liquids up to 400⁰C because the clearance is adjustable to account for the temperature expansion. The internal gear pump has self-priming capabilities and can even run dry for short periods. These pumps are birotational and are used to load and unload the same tanks. With only two moving parts they are reliable and easy to maintain.

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