variable displacement hydraulic pump animation free sample

A rotary vane pump is a type of positive-displacement pump that consists of vanes mounted to a rotor that rotates inside a cavity. In some cases these vanes can have variable length and/or be tensioned to maintain contact with the walls as the pump rotates.

The simplest vane pump has a circular rotor rotating inside a larger circular cavity. The centres of these two circles are offset, causing eccentricity. Vanes are mounted in slots cut into the rotor. The vanes are allowed a certain limited range of movement within these slots such that they can maintain contact with the wall of the cavity as the rotor rotates. The vanes may be encouraged to maintain such contact through means such as springs, gravity, or centrifugal force. A small amount of oil may be present within the mechanism to help create a better seal between the tips of the vanes and the cavity"s wall. The contact between the vanes and the cavity wall divides up the cavity into "vane chambers" that do the pumping work. On the suction side of the pump the vane chambers are increased in volume and are thus filled with fluid forced in by the inlet vacuum pressure, which is the pressure from the system being pumped, sometimes just the atmosphere. On the discharge side of the pump the vane chambers decrease in volume, compressing the fluid and thus forcing it out of the outlet. The action of the vanes pulls through the same volume of fluid with each rotation.

Multi-stage rotary-vane vacuum pumps, which force the fluid through a series of two or more rotary-vane pump mechanisms to enhance the pressure, can attain vacuum pressures as low as 10−6 mbar (0.0001 Pa).

Vane pumps are commonly used as high-pressure hydraulic pumps and in automobiles, including supercharging, power-steering, air conditioning, and automatic-transmission pumps. Pumps for mid-range pressures include applications such as carbonators for fountain soft-drink dispensers and espresso coffee machines. Furthermore, vane pumps can be used in low-pressure gas applications such as secondary air injection for auto exhaust emission control, or in low-pressure chemical vapor deposition systems.

Rotary-vane pumps are also a common type of vacuum pump, with two-stage pumps able to reach pressures well below 10−6 bar. These are found in such applications as providing braking assistance in large trucks and diesel-powered passenger cars (whose engines do not generate intake vacuum) through a braking booster, in most light aircraft to drive gyroscopic flight instruments, in evacuating refrigerant lines during installation of air conditioners, in laboratory freeze dryers, and vacuum experiments in physics. In the vane pump, the pumped gas and the oil are mixed within the pump, and so they must be separated externally. Therefore, the inlet and the outlet have a large chamber, perhaps with swirl, where the oil drops fall out of the gas. Sometimes the inlet has louvers cooled by the room air (the pump is usually 40 K hotter) to condense cracked pumping oil and water, and let it drop back into the inlet. When these pumps are used in high-vacuum systems (where the inflow of gas into the pump becomes very low), a significant concern is contamination of the entire system by molecular oil backstreaming.

One of the major advantages of the vane pump is that the design readily lends itself to become a variable-displacement pump, rather than a fixed-displacement pump such as a spur-gear (X-X) or a gerotor (I-X) pump. The centerline distance from the rotor to the eccentric ring is used to determine the pump"s displacement. By allowing the eccentric ring to pivot or translate relative to the rotor, the displacement can be varied. It is even possible for a vane pump to pump in reverse if the eccentric ring moves far enough. However, performance cannot be optimized to pump in both directions. This can make for a very interesting hydraulic-control oil pump.

A variable-displacement vane pump is used as an energy-saving device and has been used in many applications, including automotive transmissions, for over 30 years.

Introduction A pump converts mechanical energy into hydraulic energy. The mechanical energy is delivered to the pump via a prime mover such as an electric motor. The energy is used to increase the pressure of the fluid passing through the pump, allowing it to overcome frictional losses and other loads in the circuit. There are two broad classifications of pumps: Positive Displacement Pumps Dynamic Pumps Hydraulic Cylinder Electric Motor T x ω V x I Hydraulic Pump P x Q Hydraulic Motor F x v

A positive displacement pump increases the pressure of the fluid by trapping a fixed amount of it into a cavity then reducing the volume of the cavity be mechanical means. As the volume of the fluid inside the cavity is reduced, its pressure is increased, allowing it to be forced against the higher pressure in the pipe

Dynamic Pumps Centrifugal pump In dynamic pumps, kinetic energy is added to the fluid by increasing its velocity. This increase in energy is then converted to a gain in potential energy (pressure) when the velocity is reduced as the flow exits the pump into an expanding discharge pipe. According to Bernoulli principle, a reduction in flow velocity is accompanied by an increase in its pressure. Dynamic pumps are generally used for low pressure, high volume applications. Because they are not capable of withstanding high pressure, they are of little use in the fluid power field. This type of pump is primarily used for transporting fluids in pipeline. The two most common types are centrifugal and axial flow propeller pumps. Axial Flow pump

Positive displacement pumps eject a fixed amount of fluid into the hydraulic system per revolution of pump shaft rotation. For fluid power applications, positive displacement pumps have the following advantages over dynamic pumps: High-pressure capability (up to 80,000 kPa) (800 kgf/square cm) Small, compact size High volumetric efficiency Small changes in efficiency throughout the design pressure range. Can operate over a wide range of pressure requirements and speed ranges 1 square cm cylinder

Piston Pump Operation Piston movement to the left creates a partial vacuum in the pump cavity, causing check valve 2 to close and check valve 1 to open. This allows atmospheric pressure to push the fluid out of the oil tank and into the pump cavity through the inlet line. Flow continues as long as the piston is moving to the left When the piston stops at the end of the stroke, pressure in the cavity increases, causing check valve 1 to close. This pressure may not be sufficient to open valve 2, though. Atmospheric pressure TANK High Pressure Outlet Suction

Piston Pump Operation When the piston starts moving to the right, the pressure in the pump cavity rises sharply, opening valve 2 and tightly closing valve 1. The quantity of fluid displaced by the piston is forcibly ejected out of the discharge line leading to the hydraulic system. The volume of fluid displaced by the piston during the discharge stroke is called the displacement volume of the pump TANK High Pressure Outlet Compression Atmospheric Pressure

Dynamic Pumps The two most common types of dynamic pumps are the centrifugal and the axial (propeller) pumps These pump types provide continuous non-pulsating flow, but their flow output is reduced dramatically as circuit resistance is increased. The pump will produce no flow at high pressure head. The pressure at which produces no flow is called the shutoff head or the shutoff pressure. It is the maximum pressure that can be delivered by the pump. Centrifugal pump Axial Flow pump

Dynamic Pumps They are not suitable for handling viscous fluids, and thus are not suitable for use in hydraulic applications. Dynamic pumps are typically used for low pressure, high volume flow applications. Unlike positive displacement pumps, dynamic pumps are not self priming. This is because large clearance between the rotating part and the stationary housing does not allow a suction pressure to occur at the inlet port when the pump is turned on. Centrifugal pump Axial Flow pump

There are three main types of positive displacement pumps: gear, vane and piston. Because of tight sealing design, these pumps eject a fixed quantity of fluid per revolution of the pump shaft. Pump flow is almost constant and not dependent on system pressure. Their ability to produce large amounts of pressure without loosing their efficiency makes them well suited for fluid power systems.

Positive displacement pumps must be protected against overpressure if the flow resistance becomes very large. A pressure relief valve is used to protect the pump against overpressure by diverting pump flow back into the hydraulic oil tank.

Positive displacement pumps can be classified by the type of mechanical motion of its internal elements that produces the volume change in the liquid. The motion may be reciprocating or rotary. There are essentially three basic types: 1. Gear Pumps External gear pumps Internal gear pumps Lobe pumps Screw Pumps 2. Vane Pumps Unbalanced Vane Pump (Fixed or variable displacement) Balanced Vane Pump (Fixed Displacement Only) 3.Piston Pumps Axial Design Radial Design

Develop flow by carrying fluid between the teeth of two meshing gears. One of the gears is connected to the drive shaft, the other is driven as its meshes with the driver gear. Oil chambers are formed between the gear teeth, the pump housing and the side wear plates. The suction side is where teeth come out of mesh, and this is where the volume expands, bringing about a reduction in pressure. The discharge side is where teeth go into mesh, and this is where the volume decreases between mating teeth. Oil is positively ejected into the outlet port since the pump has an internal seal against leakage.

The volumetric displacement, VD of a gear pump may be defined as the theoretical volume of fluid displaced per one rotation of the gear. If the theoretical displacement is known, the theoretical volume flow rate, QT , may be related to the pump speed, N, using the relation:

Because of the small clearance (about 20 µm) between the teeth tip and pump housing, some of the oil at the at the discharge port can leak directly back toward the suction port. This means that the actual flow rate is QA is less than the theoretical flow rate QT. The internal leakage, also called pump slippage is quantified by the term volumetric efficiency, ηv . P Q Theoretical Flow Curve Actual Flow Curve Internal Loss

The volumetric efficiency for positive displacement pumps operating at design pressure is usually about 90%. It drops rapidly if the pump is operated above its design pressure because pressure increases the clearances though which leakage takes place. Pump manufacturers usually specify the volumetric efficiency at the pump rated pressure, which is the design pressure at which the pump may operate without causing mechanical damage to the pump, and does not produce excessive leakage. P Q Theoretical Flow Curve Actual Flow Curve Internal Loss

Operating the pump above its rated pressure produces excessive leakage and can damage the pump by distorting the casing and overloading the shaft bearing.

Pump operation above its rated pressure could occur when a high resistance to flow is encountered. This could result from a large actuator load or a closed (blocked) valve in the pump outlet line.

Dimensions: 25 x 25 x 10 mm Used as a lubrication pump to drive oil for lubricating machine tools. Flow rate of 3 ml/min with pump speed of 1750 to 3450 rpm Can accommodate fluids of varying viscosity ( mm2/s) Low to medium pressure head ( psi) ~ (15,000 – 25,000 kPa).

Gear pumps utilizing spur gear teeth design could develop severe vibrations and noise at high pump speeds due to sudden teeth contact in spur gears. To reduce noise and produce smoother operation, helical gears are sometimes employed. Helical gears, however, are limited to low pressure applications (below 1500 kPa) because they produce excessive axial thrusts due to the action of the helical gear.

Herringbone gear pumps eliminate end thrust and can be used to develop a pressure up to 3000 psi ~(20,000 kPa). Herringbone gears consist of two rows of helical teeth cut into one gear. One of the rows of each gear is right handed, while the other is left handed. This arrangement cancels out axial thrust force. Herringbone gear pumps operate as smoothly as helical gear pumps, and provide greater flow rates, because they could be run at higher speeds. They also produce less pulsating action because of the higher speeds.

Internal Gear Pump The internal spur gear drives the outside ring gear which is set off center. Between the two gears on one side is a crescent-shaped spacer around which oil is carried. The inlet and outlet ports are located in the end plates between where the teeth mesh and the ends of the crescent-shaped spacer.

Internal Gear Pump In operation, the internal gear drives the external ring gear and makes a fluid tight seal at the place where the teeth mesh. Rotation causes the teeth to unmesh near the inlet port, the cavity volume to increase, and suction to occur. Oil is trapped between the internal and external gear teeth on both sides of the crescent-shaped spacer and is carried from the inlet to the outlet cavity of the pump. Meshing of the gear teeth reduces the volume in the high pressure cavity near the outlet port and fluid exits from the outlet port. Wear on internal gear pumps has a tendency to reduce the volumetric efficiency more quickly than on external gear pumps. They are used mostly for lubrication and charge pumps at pressures under 1000 psi.

Internal Gear Pump The internal gear drives the external ring gear and makes a fluid tight seal at the place where the teeth mesh. Rotation causes the teeth to unmesh near the inlet port, the cavity volume to increase, and suction to occur. Oil is trapped between the internal and external gear teeth on both sides of the crescent-shaped spacer and is carried from the inlet to the outlet cavity of the pump. Meshing of the gear teeth reduces the volume in

Gerotor Pump This pump operates very much like the internal gear pump. The inner gear rotor (gerotor) is power driven and draws the outer gear rotor around as they mesh together. The tips of the inner and outer rotors make contact to seal the pumping chambers from each other. The inner gear has one tooth less than the outer gear, and the volumetric displacement is determined by the space formed by the extra tooth in the outer rotor. The gerotor pump is a compact and simple pump with only two moving elements.

Screw Pump In a screw pump, three precision ground screws meshing within a close fitting housing deliver non pulsating flow quietly and efficiently. The screw pump is an axial flow positive displacement unit. The two symmetrically opposed idler rotors act as rotating seals, confining the fluid in a succession of closures or stages.

Screw Pump The idler rotors are in a rolling contact with the central power rotor, and are free to float in their respective housing bores in a hydrodynamic oil film. There are no radial bending loads on the rotor set, and axial hydraulic forces are balanced, which eliminates the need for a thrust bearing

Lobe Pump This pump operates in a fashion similar to the external gear pump. But unlike the external gear pump, both lobes are driven externally and they do not actually contact one another. They are therefore quieter in operation than other types of gear pumps. Due to the smaller number of mating elements, lobe pumps have a higher volumetric displacement than other types of gear pumps of the same size and speed. They will, however, produce a higher amount of pulsation.

Vane Pump The rotor contains radial slots and is splined to the drive shaft. The rotor rotates inside a cam ring. Each slot contains a vane designed to mate with the surface of the cam ring as the rotor turns. Centrifugal forces keep the vanes in contact with the cam ring. During rotation, the volume increases between the rotor and the cam ring near the inlet and decreases near the outlet. This causes a continuous suction and ejection of the fluid from the inlet port to the discharge port.

If the eccentricity is less than the maximum, the theoretical volumetric displacement is Some vane pumps have provision for mechanically varying the eccentricity. Those pumps are called variable displacement pumps. A handwheel, or a pressure compensator can be used to move the cam ring to change the eccentricity. The direction of flow through the pump can be reversed by movement of the cam ring on either side of center.

In a pressure compensated vane pump, system pressure acts directly on the cam ring via a hydraulic piston on the right side as shown. This forces the cam ring against the compensator spring-loaded piston on the left side of the cam ring.

If the discharge pressure is large enough, it overcomes the compensator spring force, and shifts the cam ring to the left, reducing the eccentricity. If the discharge pressure continues to increase, zero eccentricity is finally achieved, and the pump flow becomes zero. Such a pump has its built-in protection against pressure buildup.

The pressure at which the hydraulic force piston force is equal to the compensator spring force is called the cutoff pressure, Pcutoff. The eccentricity is below its maximum value at a pressure above Pcutoff. The pressure at which the eccentricity is zero is called the dead head pressure, Pdeadhead. At dead head pressure, no pumping occurs, no power is wasted, and fluid heating is reduced. Pdeadhead Q Slope determined by stiffness of compensator spring e = emax e = 0 Pcutoff P P-Q Curve of a pressure compensated vane pump

Balanced Vane Pump A side load is exerted on the bearing of a vane pump because of pressure unbalance. This undesirable side load is also present in gear pumps. These pumps are hydraulically unbalanced.

Balanced Vane Pump A balanced vane pump is one which has two intakes and two outlets diametrically opposite each other. This produces complete hydraulic balance and minimum side load is exerted on the bearings. This permits the pump to operate at a higher pressure.

Balanced Vane Pump Instead of the circular cam ring, a balanced design vane pump has an elliptic housing, which forms two separate pumping chambers on opposite sides of the rotor. One disadvantage of a balanced vane pumps is that it can not be designed as a variable displacement unit.

Piston Pump Types A piston pump works on the principle that a reciprocating piston can draw in fluid when it extends out of a cylinder bore, and discharges it when it retracts into the bore. This principle can be applied to pump fluid, but the resulting flow will suffer from large pulsations. In order to reduce pulsations, a series of reciprocating piston pumps working with a time shift between them need to be utilized. Suction Compression

Piston Pump Types There are two mechanical arrangements which allows a set of pump to work with a time shift between them. The axial piston pump, and the radial piston pump.

In this pump, the pistons are at an angle to the drive shaft and Thrust Plate. The piston block shaft is connected to the drive shaft by a universal joint. The drive shaft, thrust plate, piston block shaft, and piston block all revolve. The connecting rods are attached to the thrust plate and revolve with it. The outlet ports are semi-circular holes in the Valve Plate, shown on the far right of the animation on edge and in a head-on view below, right. As the pump revolves, half the pistons suck in fluid as they pass over the intake port. The other pistons discharge their fluid through the outlet port.

The volumetric displacement of the pump varies with the offset angle, α. No flow is produced when the cylinder block centerline is parallel to the drive shaft centerline, (α = 0) The offset angle can vary between 0⁰ to a maximum of about 30⁰. Fixed displacement units are usually provided with 23⁰ or 30⁰ offset angle.

Radial Piston Types The working pistons extend in a radial direction symmetrically around the drive shaft, in contrast to the axial piston pump. The stroke of each piston is caused by a rotating block which houses the pistons. The pistons are held against a fixed ring which is placed eccentrically to the rotating block. The pistons are held against the ring by centrifugal force or by a set of springs. The inlet and outlet ports are placed in the center cavity in the rotating block. The placement is dependent on the direction of eccentricity between the rotor and the ring. In the figure shown, the inlet port is placed in the upper part where suction takes place, and the outlet port in the lower part, where compression takes place.

Pump Performance Pump performance is primarily a function of the precision of its manufacture. This influences both the mechanical efficiency and the volumetric efficiency of the pump. Suction Compression

Pump manufacturers specify pump performance characteristics in the form of graphs. The figure shows typical performance curves for a variable displacement piston pump operating at full displacement.

Pump Type Pressure Rating (PSI) Speed Rating (RPM) Overall Eff. (%) HP / LB Ratio Capacity (GPM) Cost ($ per HP) External Gear 2000 – 3000 1200 – 2500 80 – 90 2 1 – 150 4 – 8 Internal Gear 500 – 2000 70 – 85 1 – 200 Vane 1000 – 2000 1200 – 1800 80 – 95 1 – 80 6 – 30 Axial Piston 2000 – 12,000 1200 – 3000 90 – 98 4 6 – 50 Radial Piston 3000 – 12,000 85 – 95 5 – 35

Pump Noise Prolonged exposure to loud noise can result in loss in hearing. In addition, noise can mask sounds that people want to hear, such as voice communication between people and warning signals emanating from safety equipment. The sound that people hear come as pressure waves through the surrounding air medium. The pressure waves, which possess an amplitude and frequency, are generated by a vibrating object such as a pump, hydraulic motor, or pipeline. The human ear receives the sound waves and converts then into electrical signals that are transmitted to the brain. The brain translates these electrical signals into the sensation of sound.

Source treatment: treat misaligned pump motor/coupling, improperly installed pump/mounting plate, cavitation,i excess pump speed or pressure Modify components connected to the primary source of noise, e.g., clamping hydraulic piping at specifically located supports. Use sound absorbing material in nearby screens or partitions.

Pumps are used to increase the pressure of liquids. Liquid pressure at the inlet of the pump when the pump is not running is called the static suction pressure, and the pressure at the pump’s exit is called the static discharge pressure. The difference between the static discharge pressure and the static suction pressure is called the total static pressure of the pump. The term ‘head’ is frequently used as an alternative to pressure, particularly in US standards

When a pump is used to elevates water from a lower level to a higher level, and installed such that its centerline is at a certain height below the free surface of the inlet tank, this height becomes becomes the static suction head for the pump. Similarly, the static discharge head is the difference in level between the pump’s centerline and the liquid level at the free surface of the discharge tank . The total static pressure is the difference in elevation between the free surface of the discharge tank and the inlet tank.

During operation, the pressure of the liquid entering into the pump is reduced due to the losses in the piping connecting the supply tank to the pump’s inlet. The head loss is due to the resistance to flow presented by system piping, pipe fittings, and valves in the inlet piping. For a specific piping section, head loss depends on pipe length pipe diameter and fluid’s velocity. In addition to these parameter, it depends on fluid viscosity for the case of laminar flow, and on fluid density and surface roughness for the turbulent flow.

The pressure at the pump’s suction is the static suction head minus the head loss due to piping resistance. It is called the total suction head. In centrifugal pumps, liquid pressure may be reduced even further as its speed is increased in the narrow passages leading to the impeller of the pump. Due to the repeated drop in liquid pressure, its pressure inside the casing may become significantly lower than the atmospheric pressure.

A more serious situation occurs if the pump is placed at an elevation above the free surface of the supply tank. In this case, the pressure at the pump inlet is already below atmospheric pressure even when there is no drop due to flow. Suction head is already negative, and is called the static suction lift. When flow takes place, the resistance of the piping increases the suction lift, and fluid gets into the pump at a an even further reduced pressure.

In either case, the pressure of the liquid entering the pump may drop below the atmospheric pressure (Total suction head is negative). When the liquid pressure drops below atmospheric pressure, two things can take place: The liquid may reach its boiling pressure at the given temperature, and start to boil. Air bubbles can form inside the liquid as the air dissolved in the liquid becomes oversaturated due to the drop in its solubility at the reduced pressure.

Cavitation Cavitation is the formation of cavities in the liquid inside the pump. Cavities in the form of air bubbles and vapor bubbles can develop at reduced pressure zones, and they will collapse when they reach a high pressure region inside the casing. Bubble collapse is accompanied with high velocity jet which could hit a solid surface inside the casing with high noise and vibration. The repeated formation and collapse of the bubbles produces severe impacts which can erode the metallic components of the pump and shorten its life.

The difference between the pressure at the pump’s inlet during operation (total suction head) and the liquid’s vapor pressure is called the net positive suction head (NPSH). To avoid cavitation, the NPSH must be kept above a certain value specified by the pump’s manufacturers. This value is called NPSH required, or (NPSHr) The NPSH actually present at the suction line must be kept above NPSHr. The actual available NPSH is labeled NPSHa.

Pump Cavitation Cavitation is the formation of cavities in the liquid inside the pump. Cavities in the form of air bubbles and vapor bubbles can develop at reduced pressure zones, and will implode when they reach a high pressure zone. Vapor bubbles form when the liquid boils at a pressure below its vapor pressure at the respective temperature. Air bubbles form when the air dissolved in the liquid becomes oversaturated due to the drop in pressure.

Pump Cavitation Cavitation occurs when the pump suction lift is excessive such that the inlet pressure falls below the vapor pressure of the fluid. As a result, air or vapor bubbles, which form in the low-pressure inlet region of the pump are collapsed when they reach the high pressure discharge region. This produces high fluid velocity, noise, vibration and severe impacts which can erode the metallic components of the pump and shorten its life.

Keep suction line velocities low (below 1.2 m/s) Keep pump inlets lines as short as possible. Minimize the number of fittings in the inlet line. Mount the pump as close as possible to the reservoir. Use low pressure drop inlet filters of strainers. Use indicating-type filters and strainers so that they can be replaced at proper intervals as they become dirty.

Use the proper oil as recommended by the pump manufacturer. Use proper control on oil temperature. Operating oil temperature should be kept in the range of 50°C to 65°C to provide an optimum viscosity range and maximum resistance to liberation of air and the formation of vapor bubbles

Pump Selection Determine the flow rate requirements. This involves calculating the flow rate necessary to drive the actuator to move the load through a specified distance within a given time limit.

Pump Selection Select the system pressure. This ties in with the actuator size and the magnitude of resistive forces produced by external loads on the system. Also involved here the total amount of power to be delivered by the pump.

Pump Selection Determine the pump speed and select the prime mover. This together with the flow rate calculation, determines the pump size (volumetric displacement)

Pump Selection Select the reservoir and the associated plumbing, including piping, valving, filters and strainers, and other miscellaneous components.

Pump Selection Consider factors such as pump noise levels, power loss, need for a heat exchanger due to generated heat, pump wear and scheduled maintenance service to provide a desired life of the total system.

How to read a pump performance curve remains a topic of great interest across the food, dairy, beverage, and pharmaceutical processing industries, so in this post we provide important information on two of our most popular styles —

With manufacturing lead times growing, selecting the right pump the first time is more important than ever. At the same time, understanding the full range of each pump’s capabilities under specific operating conditions gives you a window to your options, so you’re not locked in to just a few choices during the selection process.

Also called a pump selection curve, pump efficiency curve, or pump performance curve, a pump curve chart gives you the information you need to determine a pump"s ability to produce flow under the conditions that affect pump performance. Reading pump curves accurately helps you choose the right pump based on application variables such as:

A pump has to produce enough pressure differential to overcome head loss created in pipe systems by friction, valves, and fittings. A pump curve shows the two performance factors on the X,Y axis so you can see the volume of fluids a pump can transfer under various pressure conditions.

For example, if you know the flow rate your application requires, you find the gallons per minute (or hour) rate along the bottom horizontal line of the curve and then draw a line up to the head/PSI you require. The curve will show you if the pump you have selected will perform in that application.

Centrifugal pump curves are useful because they show pump performance metrics based on head (pressure) produced by the pump and water-flow through the pump. Flow rates depend on pump speed, impeller diameter, and head.

Head is the height to which a pump can raise water straight up.Water creates pressure or resistance, at predictable rates, so we can calculate head as the differential pressure that a pump has to overcome in order to raise the water.

Common units are feet of head and pounds per square inch. (A pump curve calculator might offer different units such as Bar or meters of head). As Figure 1 illustrates, every 2.31 feet of head equals 1 PSI.

Flow is the volume of water a pump can move at a given pressure. Flow is indicated on the horizontal axis in units like gallons per minute, or gallons per hour, as shown in Figure 2.

Total Dynamic Head (TDH) is the amount of head or pressure on the suction side of the pump (also called static lift), plus the total of 1) height that a fluid is to be pumped plus 2) friction loss caused by internal pipe roughness or corrosion.

Let"s say you want to know the flow rate you can achieve from the pump in Figure 3 at 60 Hz when the design pressure is 80 PSI. In this case, the curve shows that the pump can achieve a flow rate of 1321 gallons per hour at 80 PSI of discharge pressure.

Because some centrifugal pumps operate across a range of horsepower, their curves will include additional information. Figure 4, for example, features a pump that can operate from 2 to 10 horsepower depending on desired performance.

Impeller size is another variable for meeting performance requirements. The curve above shows impeller trim sizes, at the right end of each curve, ranging from a minimum of 4.33" to a maximum of 6.42".

Reducing impeller size enables you to limit the pump to specific performance requirements. The curve above shows maximum pump performance with a full-trim impeller, minimum pump performance with a minimum-trim impeller, and performance delivered by the design-trim impeller, or the impeller trim closest to the design condition. Impellers are typically trimmed 0.20 inches (or 5mm) at a time.

In addition to pressure and flow, the curve at the bottom of Figure 4 indicates NPSHr, which stands for Net Positive Suction Head Required.NPSHr is the minimum amount of pressure required on the suction side of the pump to avoid cavitation, or the introduction of air into the fluid stream. NPSHr is determined by the pump. You always want NPSHa>NPSHr.

Good pump efficiency means that a pump is not wasting energy in order to maintain its performance point. No pump is 100% efficient, however, in the work it has to do to transfer liquids.

When selecting a pump and motor combination, consider not only the total current demand but future demand to ensure your selection has the capacity to meet changing requirements. To that end, sizing the pump for performance variables rather than peak efficiency is a common practice.

For example, while the middle of the pump efficiency curve is generally where a pump is operating at maximum efficiency in terms of pressure and flow rate, moving right on the curve above shows an increase in horsepower needed to maintain a flow rate as head increases. For example, 2 hp is required for a flow rate of 40 gpm with 80 feet of head, but maintaining 40 gpm of flow at 110 feet of head would require a 3 hp motor.

You can audit pumping systems using pump performance characteristics. Once you determine the best efficiency point (BEP) for your application, you can make adjustments to improve overall system efficiency, such as adding a variable frequency drive (VFD) and changing the diameter of the pump impeller. Controlling flow rate by adjusting pump speed via VFD instead of pressure valves can result in better efficiency and greater energy savings.

When using pumps in parallel, you can increase flow rate at the same rate of head.As figure 5 illustrates, using pumps in parallel gives you a flow rate that is the sum of pump A and pump B’s flow rates.

A positive displacement (PD) pump produces the same flow at a given speed (in revolutions per minute--RPM) no matter what the discharge pressure. Positive displacement pump curves give you the information you need to determine a pump"s ability to produce flow under the conditions that affect pump performance.

Curves answer those questions by displaying intersections of several important variables, including capacity, work horsepower, viscous horsepower, and Net Positive Suction Head required (NPSHr).

As RPM increases, the pump flow increases, from 0 gallons per minute or (GPM) at 0 RPM, to about 130 GPM at 500 RPM. Remember that some performance curve calculators might include units such as liters per minute (LPM), so check calculation units when using calculators.

Fig. 7. A PD pump curve indicates pump capacity, on the horizontal lines, in units per minute. In this example, the curve indicates gallons per minute (GPM)andliters per minute (LPM)in the left margin and the vertical lines indicates pump speed in revolutions per minute (RPM).

Positive displacement pumps deliver a constant flow of fluid at a given pump speed. When viscosity increases, however, resistance to flow increases, so to maintain system flow at higher viscosities, pumps require more horsepower.

Low viscosity also affects pump performance in the form of slip. Slip is the internal recirculation of low viscosity fluid from the discharge side of the pump back to the suction side of the pump.The amount of slip in a PD pump is influenced by the fluid’s viscosity and the discharge pressure.

As discharge pressure increases, keeping viscosity constant, more fluid slips from the discharge side to the suction side of the pump, so the pump must spin at a higher RPM to maintain output.

In Fig. 8, a positive displacement pump curve shows the influence of viscosity on slip with a correction chart. With changes in viscosity and pressure, slip correction indicates that flow capacity drops from a high of about 7 GPM to a low of about 3.5 GPM. Once viscosity is over 1000 cPs, slip basically doesn’t occur in liquid sanitary pumps. If slip is not a factor, use the 0 PSI line to determine flow rate.

Because PD pumps generate flow to transport relatively high viscosity fluids, PD pump selection requires analysis of three key influences on fluid transfer:

Dynamic viscosity is a measure of a fluid’s resistance to flow. By common sense alone, we can imagine that water is less viscous, or resistant to flow, than corn syrup, so corn syrup has a higher viscosity than water. We measure internal resistance to flow as absolute viscosity (also referred to as dynamic viscosity). It is critical for the viscosity used to be consistent with “in pump” shear conditions, or shear rates of 800 or more s-1 (inverse seconds). As the following comparison shows, differences in viscosity vary dramatically by fluid:

Shear-sensitive liquids change viscosity when under stress,such as when they are hit by an impeller inside a pump. Some liquids become less viscous with increased force (called shear thinning), while others become more viscous with increased force (called shear thickening).

Continuing with the ketchup processing example, the next section discusses additional important information on pump curves: work horsepower (WHP), viscous horsepower (VHP), and Net Positive Suction Head required (NPSHr).

When you size a PD pump it will be important to select the correct brake horsepower. Brake horsepower (BHP) is the power the pump requires to overcome the discharge pressure. BHP is determined by adding the work horsepower (WHP) and the viscous (VHP) horsepower.

Work horsepower (WHP) is the horsepower required for the selected PD pump to achieve the desired flow rate considering the anticipated pressure drop from system components. Components like valves, heat exchangers, and filter/strainers, to name a few. WHP is sometimes called external horsepower.

Fig. 9. Work horsepower (WHP), is the horsepower required to operate a Positive Displacement Pump. As pressure from the discharge side of the pump increases, the pump requires additional horsepower to operate. For example, at 300 RPM and with 150 PSI, the pump requires 6.7 working horsepower.

Maintaining pump capacity at various viscosities requires meeting horsepower minimums, as shown in Fig. 10. There is a certain minimum horsepower requirement to force the rotating parts of the pump to turn, considering the viscosity of the fluid in the pump. VHP is sometimes called internal horsepower.

Fig. 10. Viscous Horsepower (VHP) is the power needed to turn rotating parts of the pump against the fluid inside the pump. At 300 RPM and a viscosity of 500 CPS, a pump requires 4 VHP.

As you processor, you need a pump that transfers product safely and efficiently from point A to point B. But with such a large variety of pumps, motors, and applications, picking the right pump can be difficult.That"s where we come in!

CSI is known as the experts in the specification, sizing, and supplying of pumping technology for hygienic industry processes. Speak with our knowledgeable pump team today and be confident in your next pump purchase!

Central States Industrial Equipment (CSI) is a leader in distribution of hygienic pipe, valves, fittings, pumps, heat exchangers, and MRO supplies for hygienic industrial processors, with four distribution facilities across the U.S. CSI also provides detail design and execution for hygienic process systems in the food, dairy, beverage, pharmaceutical, biotechnology, and personal care industries. Specializing in process piping, system start-ups, and cleaning systems, CSI leverages technology, intellectual property, and industry expertise to deliver solutions to processing problems. More information can be found at www.csidesigns.com.

This guide is intended for engineers, production managers, or anyone concerned with proper pump selection for pharmaceutical, biotechnology, and other ultra-clean applications.

800+ science quizzes:Absorption and generation of EM waves quizAcceleration quizAccommodation quizAccuracy, precision, repeatable and reproducible quizAccuracy and precision quizAcid and insoluble base quizAcid or base quizAcids and alkalis quizAcids and carbonates quizAdaptations quizAdaptations against predators quizAdaptations of flowering plants quizAddition polymerisation quizAddition polymers quizAdrenaline quizAerobic and anaerobic respiration quizAerobic respiration quizAerobic respiration 1 quizAerobic respiration 2 quizAlcohols quizAlgae and plants quizAlkali metals and water quizAlkanes GCSE quizAlkenes GCSE quizAlloys quizAlpha radiation quizAlternative ways to extract copper quizAluminium quizAluminium and titanium quizAluminium extraction plants quizAmino acids and proteins quizAnaerobic respiration quizAnaerobic respiration 2 quizAnalysing a water sample quizAnalysing substances quizAnimal and plant cells quizAnimal and plant cells (2) quizAnimal organs quizAntacid quizAntibiotic resistant strains quizAntibiotics quizAntibiotics (2) quizAntibiotics and painkillers quizAr and Mr quizArteries and veins quizAsexual reproduction quizAtmosphere quizAtmospheric carbon dioxide and oxygen levels quizAtom economy quizAtom ideas quizAtomic numbers and Mass numbers quizAtomic structure quizAtomic structure (2) quizAtomic structure (3) quizAtomic structure (4) quizAtomic structure (5) quizAtoms quizAtoms elements and compounds quizAuxins quizBacterial cells vs plant cells quizBacterial diseases quizBalanced diet quizBalancing equations quizBalancing equations (2) quizBalancing equations (3) quizBalancing numbers quizBalancing numbers in symbol equations quizBeta radiation quizBicarbonate of soda quizBig Bang theory quizBiodiesel quizBiodiesel GCSE quizBiodiversity quizBiofuels quizBioleaching quizBiological detergents investigation quizBlood glucose levels quizBlood vessels quizBody defences against bacteria quizBond enthalpies quizBones and joints quizBones and joints (2) quizBurning fuels quizCalculating density quizCalculating masses quizCalculating percentage by mass quizCalculating percentages quizCalculating resistance quizCalculating the mean quizCalculations quizCancer quizCarbon dioxide and rate of photosynthesis quizCarbon dioxide removal quizCarboxylic acids quizCarboxylic acids and esters quizCatalysis quizCatalysts quizCatalysts (2) quizCell differentiation quizCell division 1 quizCell division 2 quizCells, tissues, organs and organ systems quizCells and batteries quizCells and cell structure quizCellular respiration quizCeramics and composites quizChanges of state quizChanging from gas to liquid to solid quizChemical bonds quizChemical formulae and symbol equations quizChemical reactions quizChemical symbols quizChromatography quizChromatography method quizCircuit symbols quizCircuit symbols (2) quizCircular motion quizClassification of living organisms (1) quizClassification of living organisms (2) quizClearing rainforests to grow crops quizClimate change models quizCloning quizCollision theory quizCollision theory and activation energy quizColoured objects and filters quizCombustion of alkanes quizCombustion of alkenes quizCommand words quizComparing Group 1 and Transition metals quizComparing a camera with the eye quizComparing copper and graphite quizComparing different methods of contraception quizComparing inks using chromatography quizComparing ultrasound and X rays quizCompetition quizCompetition (2) quizComplete combustion quizCompounds quizConcentration and rate of reaction quizConcentration of solutions quizCondensation polymerisation quizConduction quizConductors and insulators quizConservation and dissipation of energy quizContact and non contact forces quizContinental drift theory quizContraception (1) quizContraception (2) quizControl in plants quizControl of blood glucose concentration quizControlling blood water levels quizControlling fertility quizControlling internal conditions quizConvection quizCopper 2 complex ions reactions quizCoronary heart disease quizCorrosion and its prevention quizCovalent bonding quizCovalent bonding (2) quizCovalent bonding 2 quizCracking quizCracking GCSE quizCracking and alkenes quizCracking hydrocarbons quizCrystallisation quizCulturing bacteria quizCulturing microorganisms quizCurrent and potential difference quizCurrent and potential difference graphs quizCurrent atmosphere quizCurrent in series and parallel circuits quizDNA quizDNA and the genome quizDNA as a polymer quizDangers of static electricity quizDay and night quizDecay processes quizDefending against microorganisms quizDeforestation quizDehydration quizDensity quizDevelopment of the periodic table quizDiamond and Graphite quizDiet quizDiffusion quizDiffusion (2) quizDiffusion and active transport quizDigestive enzymes quizDigestive enzymes 1 quizDigestive enzymes 2 quizDigestive system quizDirect and alternating current quizDisadvantages of using fossil fuels quizDisease risk factors quizDisplacement reactions quizDisplacement reactions (2) quizDisplacement reactions (3) quizDisplacement reactions (4) quizDisposal of polymers quizDissolved substances quizDistance-time graphs quizDistance and displacement quizDistance time graphs quizDistillation quizDistribution of organisms quizDynamic equilbrium quizEarly atmosphere quizEarly atmosphere (2) quizEarly periodic table quizEffect of changing concentration on equilibrium quizEffect of changing pressure on equilibrium quizEffect of changing temperature on equilibrium quizEffect of exercise on the body quizEffects on the environment quizElastic potential energy quizElectric current quizElectric motors quizElectrical circuits quizElectricity equation calculations quizElectrode potentials quizElectrolysis quizElectrolysis half equations quizElectrolysis of a melt quizElectrolysis of aluminium oxide quizElectrolysis of copper chloride solution quizElectrolysis of salt solution quizElectrolysis of sodium chloride solution quizElectrolysis of sodium sulfate solution quizElectrolysis to extract aluminium quizElectromagnetic Induction quizElectromagnetic waves quizElectromagnetic waves (2) quizElectromagnets quizElectron arrangements quizElectron diagrams quizElectron shells quizElectronic structure quizElectronic structure of ions quizElectrons quizElectrostatic forces quizElements Compounds Mixtures quizElements Compounds Mixtures (2) quizElements Compounds Mixtures (3) quizElements and compounds quizEmbryo stem cells vs bone marrow stem cells quizEmpirical formulae quizEmulsions quizEndothermic reactions quizEnergy changes in reactions quizEnergy equation calculations quizEnergy for melting or boiling quizEnergy in a system quizEnergy in biomass quizEnergy loss in a food chain quizEnergy stores quizEnergy stores (2) quizEnergy stores and transfers quizEnergy transfer by heating quizEnergy transfer in electrical devices quizEnergy transfer in electrical devices (2) quizEnergy transfer in falling objects quizEnergy transfer when braking quizEnergy transfers quizEnergy transfers and efficiency quizEnergy transfers by heating quizEnergy transfers in electrical devices quizEnergy transfers when cycling quizEnvironmental change quizEnvironmental effects of different energy sources quizEnzymes quizEnzymes (2) quizEnzymes in digestion quizEnzymes in industry quizEquilibria quizErrors quizEsters quizEstimating number of daisies in field quizEthanol quizEthanol as a fuel quizEthene gas in the food industry quizEukaryotes and prokaryotes quizEvaporation and condensation quizEvolution quizEvolution in plants quizEvolution of flowering plants quizExamples of energy transfers quizExchange systems in plants quizExchanging materials quizExoendo quizExothermic and endothermic quizExothermic and endothermic reactions quizExothermic and endothermic reactions (2) quizExothermic or endothermic quizExothermic reaction experiment quizExothermic reactions quizExpansion and contraction quizExtracting aluminium from bauxite vs recycling quizExtracting copper quizExtracting copper from ores quizExtracting metals quizExtraction of metals quizExtraction of metals and reduction quizFactors affecting daisy distribution quizFactors affecting food security quizFactors affecting speed quizFactors affecting stopping distance quizFalling coin and feather quizFarming techniques quizFertilisation quizFertilisers quizFiltration quizFlame emission spectroscopy quizFlame tests quizFlame tests vs flame emission spectroscopy quizFood chains quizFood production quizForce and acceleration quizForce equation calculations quizForce vs extension for plastic strip quizForce vs extension graph quizForce vs extension investigation quizForces quizForces and braking quizForces and elasticity quizForces and motion quizForces and terminal velocity quizForces on a skydiver quizFormation of crude oil quizFormation of ionic compounds quizForming ions quizForming sodium oxide quizForms of energy quizFormulations quizFossil fuels quizFossil fuels and nuclear power quizFossils quizFossils (2) quizFractional distillation quizFractional distillation (2) quizFractional distillation (3) quizFractional distillation vs Cracking quizFuel cells quizFuels from crude oil vs fuel from plants quizFuels from plants vs crude oil quizFullerenes quizFullerenes (2) quizFungal diseases quizFurther electrolysis quizGamma radiation quizGamma rays quizGas chromatography quizGas chromatography2 quizGas pressure quizGaseous exchange quizGases in our atmosphere quizGene expression quizGeneral properties of waves quizGenerating electricity quizGenerating electricity (2) quizGenetic disorders quizGenetic engineering quizGenetic engineering (2) quizGenetic variation quizGenetically modified plants quizGibberellins quizGlobal warming quizGlobal warming and biofuels quizGonorrhoea quizGraph skills quizGraphene quizGravitational potential energy quizGravitational potential energy calculations quizGravitropism in roots quizGravitropism in shoots quizGreenhouse gases quizGreenhouses quizGroup 0 quizGroup 1 quizGroup 1 and Group 7 quizGroup 2 quizGroup 7 quizGroup 7 physical properties quizHPV vaccination quizHaber process quizHaber process conditions quizHalf equations quizHalf life quizHard and soft water quizHard and soft water quizHardwater quizHarmful effects of smoking quizHazards and risks quizHealth issues quizHealthy diet quizHeating and insulating buildings quizHome insulation quizHomeostasis quizHomeostasis (2) quizHomeostasis and response quizHormones quizHormones in the menstrual cycle quizHousehold electricity quizHow Science Works quizHow genetic engineering works quizHuman defence systems quizHydraulics quizHydrocarbons and alkanes quizHydroelectric generators quizHydrogen vs petrol as a fuel for cars quizIV characteristics of a diode quizIV characteristics of a filament lamp quizIV characteristics of a resistor quizIdeal gas equation quizIdentification of common gases quizIdentifying halide ions quizIdentifying ions 1 quizIdentifying ions 2 quizIdentifying ions 3 quizIdentying halide ions quizIgneous rocks quizImportance of diffusion quizImportance of light in photosynthesis quizIncomplete combustion quizIndependent and dependent variables quizIndicators quizInertia quizInfectious diseases quizInfrared radiation quizInsulation experiment quizInterconverting units for distance quizInterconverting units for energy quizInterconverting units for mass quizInterdependence quizInterdependence and competition quizInternal energy quizInverse square law quizInvestigating a mixture using chromatography quizInvestigating density of irregular shaped objects quizInvestigating density of liquids quizInvestigating density of regular shaped objects quizInvestigating different insulating materials quizInvestigating enzymes quizInvestigating factors affecting reaction time quizInvestigating how force affects acceleration quizInvestigating how light intensity affects plant distribution quizInvestigating how mass affects acceleration quizInvestigating infrared absorption quizInvestigating infrared emittance quizInvestigating infrared radiation quizInvestigating infrared radiation (2) quizInvestigating length of wire vs resistance quizInvestigating making salts quizInvestigating metal reactivity quizInvestigating osmosis quizInvestigating photosynthesis rate quizInvestigating population size by random sampling quizInvestigating rate of reaction quizInvestigating rate of reaction (2) quizInvestigating reaction times quizInvestigating specific heat capacity quizInvestigating specific heat capacity (2) quizInvestigating temperature changes quizInvestigating thermal conductivity quizInvestigating water waves quizInvestigating waves in a solid quizInvestigation quizIonic bonding quizIonic bonding (2) quizIonic compounds quizIonic compounds (2) quizIron and Steel quizIsotopes quizKidney failure quizKidneys quizKinetic energy quizKinetic theory quizLD and HD poly(ethene) quizLD and HD polyethene quizLand use quizLaw of conservation of mass quizLegal and illegal drugs quizLenses and refraction quizLevel of hazard of nuclear radiation quizLife cycle assessment quizLife cycle assessment (2) quizLife cycle assessment (3) quizLife cycle assessment for shopping bags quizLife cycle of a star quizLife processes quizLight intensity and rate of photosynthesis quizLimestone quizLimestone as a building material quizLimestone quarrying quizLimiting reactants quizMIcroscopy quizMagnetic field around a wire quizMagnetic fields quizMagnets quizMains electricity quizMaintaining biodiversity quizMaking ammonia quizMaking ammonium sulfate (industrial) quizMaking ammonium sulfate (laboratory) quizMaking copper sulfate crystals quizMaking copper sulfate crystals (2) quizMaking drugs quizMaking electricity quizMaking ethanol quizMaking ethanol from ethene conditions quizMaking insoluble salts quizMaking lithium sulfate crystals quizMaking magnesium chloride crystals quizMaking potassium chloride crystals quizMaking potassium sulfate crystals quizMaking proteins quizMaking salts quizMaking soluble and insoluble salts quizMaking soluble salts quizMaking soluble salts from acids quizMalaria quizManufacture use and disposal of products quizMass and charge of subatomic particles quizMass calculations quizMass of solid dissolved in a liquid quizMeasuring rate of reaction quizMeasuring rate of reactions (2) quizMeasuring skills quizMeasuring the speed of sound quizMeasuring the speed of sound (2) quizMeasuring the speed of water waves quizMeasuring the speed of waves in a solid quizMedical diagnosis using X rays quizMeiosis quizMelting points and boiling points quizMelting points and boiling points (2) quizMelting points and boiling points (3) quizMetabolic rate quizMetabolism quizMetal-aqua ions quizMetal extraction quizMetal ores quizMetallic bonding quizMetallic bonding (2) quizMetals and non-metals quizMetals and nonmetals quizMetamorphic rocks quizMicroorganism cultures quizMicroscopy quizMitosis and the cell cycle quizMitosis and the cell cycle quizMitosis vs meiosis quizMixtures quizModels of the atom quizModels of the atom (2) quizMole calculations quizMoles quizMoles in solution quizMoles in solution2 quizMoments and levers quizMomentum quizMonoclonal antibodies quizMore redox titration quizMutations and protein synthesis quizNaming alkenes quizNaming salts quizNaming salts (2) quizNanoscience quizNatural selection quizNatural selection in tree frogs quizNeutralisation quizNeutralisation (2) quizNewtons first law of motion quizNewtons second law of motion quizNitrate and magnesium ion deficiencies quizNuclear fission quizNuclear fission (2) quizNuclear fusion quizNuclear power stations quizNuclear radiation quizOld and new species quizOsmosis quizOur solar system quizOxidation quizOxidation and reduction quizOxidation of copper and magnesium quizOzone quizOzone layer quizPainting vs galvanising to prevent rusting quizPaper chromatography quizPaper cups vs polystyrene cups quizParallel circuits quizParticle model quizParticle model (2) quizParticle model equation calculations quizPathogens and white blood cells quizPeer review quizPercentage by mass quizPercentage by mass2 quizPercentage by mass3 quizPercentage yield quizPeriod 3 elements and oxygen quizPeriodic table quizPeriodic table (2) quizPhosphate rock quizPhotosynthesis quizPhotosynthesis (2) quizPhotosynthesis (3) quizPhototropism quizPhysical and chemical changes quizPhysics equations (1) quizPhysics equations (2) quizPhysics equations (3) quizPhysics equations (4) quizPhysics equations (5) quizPhytomining quizPlanets quizPlanets (2) quizPlanning an investigation quizPlant diseases quizPlant organs quizPlant structure quizPlastic bags quizPlate tectonics quizPlotting the magnetic field pattern quizPlum pudding model vs nuclear model quizPlum pudding model vs nuclear model (2) quizPoles of a magnet quizPollution quizPolymerisation quizPolymers quizPotable water quizPotential difference quizPower quizPowering electric cars quizPreclinical tests and clinical trials quizPregnancy quizPressure quizPressure in liquids quizPreventing rusting quizProducts of combustion quizProducts of photosynthesis quizProkaryotic and eukaryotic cells quizProperties of Group 1 metals quizProperties of electromagnetic waves quizProperties of hydrocarbons quizProperties of metals and non metals quizProperties of metals and nonmetals quizProperties of nuclear radiation quizProperties of transition metals quizProperties of waves quizProtein synthesis quizProteins quizProteins and enzymes quizProtist diseases quizProtons electrons and neutrons in ions quizProtons electrons and neutrons quizProtons electrons and neutrons quizProtons electrons and neutrons in ions quizPuberty quizPure and impure substances quizPure metals and alloys quizPurifying water quizPyramid of biomass quizRadio waves quizRadioactive contamination quizRadioactive decay quizRadioactive substances quizRadiotherapy quizRainforests quizRandom errors and systematic errors quizRange of vision quizRate of chemical reactions quizRate of heat transfer quizRate of photosynthesis quizRate of reaction quizRate of reaction graphs quizRate of reaction investigation quizRatios quizRaw materials quizRay diagrams quizReaction of sodium thiosulfate and acid quizReaction profiles quizReaction times quizRecycling copper quizRecycling copper metal quizRecycling copper old quizRecycling copper vs extraction from ores quizRed shift quizReducing friction quizReducing the spread of infectious diseases quizReflection quizReflection of light quizReflex actions quizRefraction quizRefractive index quizRelative atomic mass quizRelative formula mass quizRelative formula mass2 quizRelative formula mass3 quizRelay switch quizRenewable energy sources quizReproduction quizReproductive organs quizResistance quizResistance in different lengths of wire quizResistant bacteria quizResistors quizRespiration quizResponse to exercise quizResponse to exercise (2) quizResultant forces quizReversible reactions quizReversible reactions (2) quizRf values quizRoasting sulfides in air quizRoot hair cells quizRusting quizRusting experiment quizSalmonella quizSampling quizSatellites quizScalar and vector quantities quizScience investigation 1 quizScience investigation 2 quizScience investigation 3 quizScience investigation 4 quizScientific models quizScientific theories quizScientific theories and models quizSeasons quizSedimentary rocks quizSeismic waves quizSelective breeding quizSeparating a mixture of sand and salt quizSeparating hydrocarbons quizSeparating mixtures quizSeparating sand and salt quizSeries and parallel circuits (2) quizSeries and parallel circuits quizSeries and parallel circuits (2) quizSeries circuits quizSex determination quizSexual reproduction quizSexual reproduction (2) quizShadows and reflections quizShapes of molecules quizShort sight and long sight quizSignificant figures quizSignificant figures (2) quizSimple calorimetry quizSimple distillation quizSimple electrolysis quizSize and mass of atoms quizSkydiving and terminal velocity quizSmoking quizSodium and lithium quizSolar cells quizSolar panels quizSolar radiation quizSolar radiation and temperature on Earth quizSolids, liquids and gases quizSolids liquids and gases quizSolubility quizSound quizSpecialised cells quizSpecialised cells (2) quizSpecific heat capacity quizSpecific latent heat quizSpecific latent heat of fusion quizSpectrometry quizSpeed quizSpeed and velocity quizSpeed equation calculations quizSpotting patterns quizSquash ball experiment quizStability quizStandard form quizStar formation quizStars quizStates of matter quizStates of matter (2) quizStates of matter (3) quizStates of matter (4) quizStatic charges quizStatic electricity quizStatins and stents quizStem cells quizStem cells (2) quizStopping distance quizStopping distance (2) quizStructure and formulae of alkenes quizStructure determination quizStructure of DNA quizStructure of atoms quizStructure of the Earth quizSubatomic particles quizSugar control quizSustainable development quizSustainable development old quizSustainable fisheries quizSwitch mode transformers quizTectonic Plates quizTemperature and rate of photosynthesis quizTemperature and rate of reaction quizTemperature control quizTerminal velocity quizTesting a leaf for starch quizTesting drugs quizTesting for lipids and protein quizTesting for nutrients in foods quizTesting for sugars and starch quizTesting new drugs quizTesting the law of conservation of mass quizThe Ear quizThe Eye quizThe National Grid quizThe blood quizThe blood system quizThe carbon cycle quizThe carbon cycle (2) quizThe digestive system quizThe digestive system (2) quizThe energy change of reactions quizThe fire triangle quizThe greenhouse effect quizThe heart quizThe human nervous system quizThe immune system quizThe kidney quizThe lungs quizThe lungs (2) quizThe lungs (3) quizThe menstrual cycle quizThe mole quizThe motor effect quizThe motor effect (2) quizThe nervous system quizThe pH scale quizThe periodic table quizThe power of a lens quizThe reactivity series quizThe rock cycle quizThe spring constant quizThe structure of an atom quizThe water cycle quizThe water cycle (2) quizTheory of evolution quizTherapeutic cloning quizThermal decomposition quizThermal conductivity quizThermal decomposition quizThermosetting and thermosoftening plastics quizThree-pin plugs quizThree core cables quizThree pin plugs quizThree states of matter quizThyroxine and negative feedback quizTissue in plant leaves quizTitration calculations quizTitration method quizTitrations quizTitrations (2) quizTobacco smoke quizTooth decay quizTransect lines and quadrats quizTransferring electrical energy quizTransformers quizTransition metals quizTranspiration quizTransport systems in plants quizTransverse and longitudinal waves quizTreating infertility quizTrends in Period 3 quizTrophic levels quizUltrasound quizUltrasound waves and echo sounding quizUltraviolet waves quizUnderstanding equations quizUnderstanding paper chromatography quizUnderstanding rate of reaction quizUnhealthy diet quizUnit prefixes (1) quizUnit prefixes (2) quizUses and dangers of electromagnetic waves quizUses and dangers of nuclear radiation quizUses and extractio