What is Fluid Power? (2023)

To visualize a basic hydraulic system, think of two identical syringes connected together with tubing and filled with water (see Figure 1). Syringe A represents a pump, and Syringe B represents an actuator, in this case a cylinder. Pushing the plunger of Syringe A pressurizes the liquid inside.

This fluid pressure acts equally in all directions (Pascal’s Law), and causes the water to flow out the bottom, into the tube, and into Syringe B. If you placed a 5 lb. object on top of the plunger of Syringe B, you would need to push on Syringe A’s plunger with at least 5 lbs. of force to move the weight upward. If the object weighed 10 lbs., you would have to push with at least 10 lbs. of force to move the weight upward.

What is Fluid Power? (1)

If the area of the plunger (which is a piston) of Syringe A is 1 sq. in., and you push with 5 lbs. of force, the fluid pressure will be 5 lbs./sq. in. (psi). Because fluid pressure acts equally in all directions, if the object on Syringe B (which, again has an area of 1 sq. in.) weighs 10 lbs., fluid pressure would have to exceed 10 psi before the object would move upward. If we double the diameter of Syringe B (see Figure 2), the area of the plunger becomes four times what it was. This means a 10 lb. weight would be supported on 4 sq. in. of fluid.

Therefore, fluid pressure would only have to exceed 2.5 psi (10 lbs. ÷ 4 sq. in. = 2.5 psi) to move the 10 lb. object upward. So moving the 10 lb. object would only require 2.5 lbs. of force on the plunger of Syringe A, but the plunger on Syringe B would only move upward ¼ as far as when both plungers were the same size. This is the essence of fluid power. Varying the sizes of pistons (plungers) and cylinders (syringes) allows multiplying the applied force.

(Video) Fluid Power Basics

In actual hydraulic systems, pumps contain many pistons or other types of pumping chambers. They are driven by a prime mover (usually an electric motor, diesel engine, or gas engine) that rotates at several hundred revolutions per minute (rpm). Every rotation causes all of the pump’s pistons to extend and retract — drawing fluid in and pushing it out to the hydraulic circuit in the process. Hydraulic systems typically operate at fluid pressures of thousands of psi. So a system that can develop 2,000 psi can push with 10,000 lbs. of force from a cylinder about the same size as a can of soda pop.

What is Fluid Power? (2)

Off-highway equipment is probably the most common application of hydraulics. Whether it’s construction, mining, agriculture, waste reduction, or utility equipment, hydraulics provides the power and control to tackle the task at hand and often to provide motive power to move equipment from place to place — especially when track drives are involved. Hydraulics is also widely used in heavy industrial equipment in factories, in marine and offshore equipment for lifting, bending, pressing, cutting, forming, and moving heavy work pieces.

The principles of pneumatics are the same as those for hydraulics, but pneumatics transmits power using a gas instead of a liquid. Compressed air is usually used, but nitrogen or other inert gases can be used for special applications. With pneumatics, air is usually pumped into a receiver using a compressor.

(Video) Introduction to Fluid Power Systems (Full Lecture)

The receiver holds a large volume of compressed air to be used by the pneumatic system as needed. Atmospheric air contains airborne dirt, water vapor, and other contaminants, so filters and air dryers are often used in pneumatic systems to keep compressed air clean and dry, which improve reliability and service life of the components and system. Pneumatic systems also use a variety of valves for controlling direction, pressure, and speed of actuators.

What is Fluid Power? (3)

Most pneumatic systems operate at pressures of about 100 psi or less. Because of the lower pressure, cylinders and other actuators must be sized larger than their hydraulic counterparts to apply an equivalent force. For example, a hydraulic cylinder with a 2 in. diameter piston (3.14 sq. in. area) and fluid pressure of 1,000 psi can push with 3140 lbs. of force. A pneumatic cylinder using 100 psi air would need a bore of almost 6½ in. (33 sq. in.) to develop the same force.

Even though pneumatic systems usually operate at much lower pressure than hydraulic systems do, pneumatics holds many advantages that make it more suitable for many applications. Because pneumatic pressures are lower, components can be made of thinner and lighter weight materials, such as aluminum and engineered plastics, whereas hydraulic components are generally made of steel and ductile or cast iron.

Hydraulic systems are often considered rigid, whereas pneumatic systems usually offer some cushioning, or “give.” Pneumatic systems are generally simpler because air can be exhausted to the atmosphere, whereas hydraulic fluid usually is routed back to a fluid reservoir.

Pneumatics also holds advantages over electromechanical power transmission methods. Electric motors are often limited by heat generation. Heat generation is usually not a concern with pneumatic motors because the stream of compressed air running through them carries heat from them. Furthermore, because pneumatic components require no electricity, they don’t need the bulky, heavy, and expensive explosion-proof enclosures required by electric motors.

(Video) Introduction to Fluid Power | Skill-Lync

In fact, even without special enclosures, electric motors are substantially larger and heavier than pneumatic motors of equivalent power rating. Plus, if overloaded, pneumatic motors will simply stall and not use any power. Electric motors, on the other hand, can overheat and burn out if overloaded. Moreover, torque, force, and speed control with pneumatics often requires simple pressure- or flow-control valves, as opposed to more expensive and complex electrical drive controls. And as with hydraulics, pneumatic actuators can instantly reverse direction, whereas electromechanical components often rotate with high momentum, which can delay changes in direction.

Another advantage of pneumatics is that it allows using vacuum for picking up and moving objects. Vacuum can be thought of as negative pressure — by removing air (evacuating) from the volume between two parts, atmospheric pressure outside the volume pushes the parts together. For example, attempting to pick up a single sheet of paper or a raw egg presents a challenge with conventional grippers. But with a vacuum pneumatic system, evacuating a suction cup in contact with a sheet of paper or eggshell will cause atmospheric pressure to push the paper or egg against the cup, allowing it to be lifted.

What is Fluid Power? (4)

Factory automation is the largest sector for pneumatics technology, which is widely used for manipulating products in manufacturing, processing, and packaging operations. Pneumatics is also widely used in medical and food processing equipment. Pneumatics is typically thought of as pick-and-place technology, where pneumatic components work in concert to perform the same repetitive operation thousands of times per day.

But pneumatics is much more. Because compressed air can have a cushioning effect, it is often called on to provide a gentler touch than what hydraulics or electromechanical drives can usually provide. In many applications, pneumatics is used more for its ability to provide controlled pressing or squeezing as it is for fast and repetitive motion. Moreover, electronic controls can give pneumatic systems positioning accuracy comparable to that of hydraulic and electromechanical technologies.

(Video) Fluid Power Lesson Pt. 1

Pneumatics is also widely used in chemical plants and refineries to actuate large valves. It’s used on mobile equipment for transmitting power where hydraulics or electromechanical drives are less practical or not as convenient and in on-highway trucking for various vehicle functions. And of course, vacuum is used for lifting and moving work pieces and products. In fact, combining multiple vacuum cups into a single assembly allows lifting large and heavy objects.

Standard electric motors typically rotate at 1,800 or 3,600 revolutions per minute (rpm) — much faster than is practical for most machines. Gasoline and diesel engines also rotate at thousands of rpm when powering equipment. Therefore, some form of power transmission is needed to convert power from the motor or engine to a more useable form — slower speed and, often, linear motion instead of rotary.

Mechanical power transmission methods include gear, chain, belt, and other mechanical drives that convert the high-speed mechanical power from the engine or motor’s output shaft to a slower speed with higher torque (twisting force). Mechanical power transmission components also include ball screws, rack-and-pinion assemblies, chain drives, and other components that convert rotational motion and torque to linear motion and force.

Electrical methods of power transmission regulate electrical power to the motor to control speed and torque. But these methods cannot convert the rotary motion of a motor to linear. When linear output is needed, a linear motor may be used, but, its high cost generally makes a mechanical rotary-to-linear motion device more practical for producing linear motion and force.

In many cases, however, mechanical and electrical methods cannot provide a practical power transmission solution. In these cases, fluid power — whether hydraulic or pneumatic — is used because it can deliver linear and rotary motion with high force and torque within a smaller, lighter package than is possible with other forms of power transmission.

(Video) Fluid Power Engineering

A cement mixer is an example illustrating how different methods of power transmission can be used. Early cement mixers used mechanical drives driven either by the truck’s engine or transmission. A system of gears, chain drives, and drive shafts provided the speed and torque necessary to rotate the heavy drum of concrete, but speed was difficult to control. The rotational speed of the drum depended on the engine speed or transmission speed. As the driver shifted gears, the drum would speed up or slow down, and rarely rotated at the ideal speed. Plus, the complexity and bulk of all the mechanical components were highly maintenance intensive.

An electrical drive could provide good speed control but would require a high-power electric generator, controls, and a motor to drive the drum. Plus, the motor would either be prohibitively large or would require a large gearbox to achieve the low-speed rotation of the mixer drum. Either solution would be much larger and heavier than a hydraulic drive.

Hydraulic drives are the primary choice for cement mixer drives. They use a pump, hydraulic motor, and valves to precisely control speed regardless of the engine or transmission speed. The drum rotates at optimum speed or can be manually controlled. Plus, the components are relatively compact: the pump is tucked away within the framework of the truck, and the hydraulic motor is only a small fraction of the size of a comparable electric motor-gearbox combination.


What is meant by fluid power? ›

Fluid power is the use of fluids under pressure to generate, control, and transmit power. Fluid power is subdivided into hydraulics using a liquid such as mineral oil or water, and pneumatics using a gas such as air or other gases.

What are examples of fluid power? ›

There are two basic types of fluid power systems: hydraulic systems, which use liquids such as water and oil, and pneumatic systems, which utilize neutral gases such as air.

What is the importance of fluid power? ›

Fluid power systems generally can transmit equivalent power within a much smaller space than mechanical or electrical drives can, especially when extremely high force or torque is required. Fluid power systems also offer simple and effective control of direction, speed, force, and torque using simple control valves.

How can fluid power help the world? ›

Industrial: Fluid power is used to provide power transmission and motion control for industrial machinery. End use industries range from plastics working to paper production. Applications include metalworking equipment, controllers, automated manipulators, material handling and assembly equipment.

Where is fluid power used? ›

While fluid power can be used in most any industry or application, it is commonly seen in markets that include packaging, off-highway, mining, offshore/marine, medical, material handling, construction, aerospace, automation, robotics, and entertainment.

What is fluid in simple words? ›

: a substance (such as a liquid or gas) tending to flow or conform to the outline of its container.

What is fluid power symbol? ›

Fluid Power Symbols. Circles generally represent devices that can deliver or use oil. Notice that the symbol does not describe the component construction. Symbols describe component functions only.

What are three advantages of fluid power? ›

force or torque can be held constant — this is unique to fluid power transmission. high torque at low speed — unlike electric motors, pneumatic and hydraulic motors can produce high torque while operating at low rotational speeds. Some fluid power motors can even maintain torque at zero speed without overheating.

How is fluid power measured? ›

(PSI) = Force (Pounds) / Area ( Sq. In.) (Pounds) = Pressure (psi) × Area (sq.

What impact does fluid power have on our everyday lives? ›

Fluid power is in our ever day life. We see the use of fluid power in Cooling systems in most vehicles as it also is the heating system. Power steering systems in vehicles, Hydro electric generation, Lift tilt system on forklift and brake systems in cars. Fluid power helps us achieve everyday activities.

What are 5 applications for fluid power? ›

Our hydraulic control units are used in a wide range of applications across many markets:
  • • Material Handling. • Aircraft Ground Support. • Access Platforms. • Security & Parking Barriers.
  • • Marine. • Disability Lifts. • Mining & Construction. • Light Industrial.
  • • Agriculture. • Motor Sports. • Leisure & Entertainment.

When was fluid power discovered and how? ›

1648: French physicist Blaise Pascal realized that pressure on a confined fluid exerted an equal force in all directions, and those forces could be harnessed. 1738: Nearly 100 years later, Daniel Bernoulli put Pascal's fluid power discovery to use by pressurizing water in pumps and mills using Bernoulli's principle.

What are the fluid power equipments? ›

The fluid power equipment can be defined as industrial equipment or components that use fluids (liquid or gas) to transmit power from one destination to another. These types of tools are majorly operated by using two methods called hydraulic and pneumatic.

What is fluid in a sentence? ›

Examples from Collins dictionaries

Make sure that you drink plenty of fluids. The forehand stroke should be fluid and well balanced. The situation is extremely fluid and it can be changing from day to day. The viscosity of a fluid is a measure of how easily it will flow.

Why are they called fluids? ›

Liquids and gases have the tendency to flow, i.e., their molecules can move freely from one place to another. Therefore, they are known as fluids.

What is pressure in fluid power? ›

In order to understand the finer points of fluid power, one must first understand the concept of pressure. Pressure is defined as the measure of force acting perpendicular to a unit area. In mathematics, pressure is stated as P=F/A where P equals the Pressure, F equals force and A equals the area we are discussing.

What is viscosity in fluid power? ›

Viscosity is a measure of a hydraulic fluid's resistance to flow. It is a hydraulic fluid's most important characteristic and has a significant impact on the operation of the system. When a hydraulic oil is too thin (low viscosity), it does not seal sufficiently. This leads to leakage and wear of parts.

Why is fluid power preferred in Mobile? ›

Power can be transmitted without any delay: 2. When overloaded, fluid power systems stop without damaging the components 3. Speed variation cannot be achieved.

What are the advantages and disadvantages in using fluid power? ›

Advantages of hydraulic systems include power, accuracy, efficiency and ease of maintenance. But they disadvantages too: they can leak, which makes them messy, and the fluids inside them are often caustic to paint and some seals.

What are the limitations of fluid power system? ›

The main disadvantages are lack of understanding of the equipment and poor circuit design, which can result in overheating and leaks. Overheating occurs when the machine uses less energy than the power unit provides. (Overheating usually is easy to design out of a circuit.)

What is the unit of fluid? ›

DimensionCGS unitsSI units
Length (L)Centimeter (cm)meter, (m)
Mass (M)Gram (g)kilogram (kg)
Time (T)Second (sec)Second (s)
Force (F)Dyne (Dyn)Newton (N) (=kg m/s2)
3 more rows

How does fluid power equipment work? ›

Fluid power is a term describing hydraulics and pneumatics technologies. Both technologies use a fluid (liquid or gas) to transmit power from one location to another. With hydraulics the fluid is a liquid (usually oil but can be water) whereas pneumatics uses a gas (usually compressed air).

What is the device used to measure fluid? ›

A hydrostatic gauge can be used to measure the pressure of the liquid.

How do hydraulics make life easier? ›

Hydraulic systems are capable of moving heavier loads as well as providing greater force than mechanical, electrical or pneumatic systems. The fluid power system means it can easily cope with a large weight range without having to use gears, pulleys or heavy leavers.

What are the two most common power sources in fluid power systems? ›

Most fluid power circuits use compressed air or hydraulic fluid as their operating medium. Whilst these systems are the same in many aspects, they can also have very different characteristics.

What is fluid power automation? ›

The use of air or liquids to provide motion in actuators is known as fluid power. In addition to electric motors and actuators it is one of the most common method of creating motion in automated processes.

Who discovered fluids? ›

Daniel Bernoulli

His theory of the motion of fluids, the germ of which was first published in his memoir entitled Theoria nova de motu aquarum per canales quocunque fluentes, communicated to the academy of St Petersburg as early as 1726, was founded on two suppositions, which appeared to him conformable to experience.

Why are hydraulics important? ›

Hydraulics are used for critical components. They are used in car brakes, gasoline pumps, elevators, and amusement park rides. If they were not reliable, we would be anxious every time they crossed our path. Hydraulics are made meticulously to ensure safety.

What is the formula for fluid power? ›

(PSI) = Force (Pounds) / Area ( Sq. In.) (Pounds) = Pressure (psi) × Area (sq.

What do you mean by fluid power system Mcq? ›

Explanation: Fluid Power system is a power transmission system in which, the transmission of power takes place by means of “oil under pressure” or “compressed air”.

How does a fluid power system work? ›

Fluid power technology uses a pump to deliver pressurized fluid to a cylinder, motor, or rotary actuator. Output speed and direction is controlled by varying flow rate from the pump or through valves within the fluid power circuit.

What is power formula? ›

The formula is P = E/t, where P means power, E means energy, and t means time in seconds. This formula states that power is the consumption of energy per unit of time.

What converts fluid power into work? ›

Actuator - A device which converts hydraulic power into mechanical force and motion. (Examples: hydraulic cylinders and motors.)

What are the 3 formula for power? ›

To calculate the power calculation formula, we have to remember three equations. They are: P (watts) = V (volts) x I (amps) P (watts) = I2 (amps) x R (Ω)

What is fluid mechanics * Mcq? ›

b) Study of fluid behaviour in motion. c) Study of fluid behaviour at rest and in motion. d) Study of fluid behaviour at rest and in motion. Explanation: The study of fluid behaviour (liquids, gases, blood, and plasmas) at rest and in motion is known as fluid mechanics.

Why is water called a fluid class 3rd? ›


What are the 3 types of power systems? ›

Radial, Loop, & Network Systems

There are three basic types of distribution system designs: Radial, Loop, or Network. As you might expect, you can use combinations of these three systems, and this is frequently done.

What are the 3 disadvantages of fluid power? ›

The main disadvantages are lack of understanding of the equipment and poor circuit design, which can result in overheating and leaks. Overheating occurs when the machine uses less energy than the power unit provides. (Overheating usually is easy to design out of a circuit.)


1. Discovering Fluid Power
(International Fluid Power Society - IFPS)
2. How Fluid Systems Work
(Learning & Development)
3. What is Fluid Power | Introduction of Oil Hydraulic System | Unit - 1 | Industrial Fluid Power
(Engineers Aadhar)
4. Calculating Work, Power and Horsepower in Fluid Power
5. Discovering Fluid Power
6. Fluid Power Technology
(Balluff Worldwide)
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