How to Understand How Hydraulic Jack Work

Definition of Jack and Its Types:

Jack is commonly known as a tool or device for lifting the heavy objects especially the automobile vehicles in order to change a tire or the car’s undercarriage or for the underside inspection. It is used to lift vehicles from one side from the ground. Jacks are available in a variety of sizes and they lift weight according to their size. Jacks can be categorized by the type of force they employ. The force applied by the jacks runs on these two primary mechanisms i.e. screw threads and hydraulic cylinders. Therefore, jacks categorized in these two types:

  • Hydraulic Jack
  • Mechanical Jack

Hydraulic Jack:

These types of jacks are more powerful than mechanical as they are used to raise the elevator in the buildings. The power source used by the hydraulic jacks to lift up the weights is hydraulic fluid, these jacks contain two cylinders which are of different sizes connected with a pipe, hydraulic fluid is forced by a plunger into these cylinders. Oil goes into the pump chamber when the plunger is pulled back and oil pushed back into the cylinders when the plunger moves forward. This movement of oil creates pressure that powers the jack. The two types of hydraulic jack are floor jack and bottle jack, which I have described in detail in the section below.

Mechanical Jack:

Mechanical jacks include house jacks or car jacks. These types of jacks are often found in houses and garages to raise heavy objects and in order to raise or lower the objects, this type of jacks use physical means. They are rated on its capacity to lift a weight. The most common type of mechanical jack is the screw jack, and it works by using the lever moved by an operator. To raise and lower the weight screw jacks use its shape of thread. Mechanical jacks are also used for changing stage design, in altering the setting of woodwork machine and in construction.

What are Hydraulic Jacks?

Hydraulic jacks are one of the types of jacks which are used to lift up the weights or to lift up the automobile vehicle up from one side from the ground so that the vehicle can be tooled. These are the jacks which work on the Pascal principle. In the construction industry, many tools use hydraulic jacks in order to accomplish their tasks. Hydraulic jacks create pressure by using the hydraulic fluid and this fluid is generally oil. The movement of oil from the pump chamber to cylinders builds up the pressure in these jacks.

Why We Need Hydraulic Jacks?

Hydraulic jack is a useful device that is used to lift up heavy vehicles such as bulldozers, elevators, these jacks make work a lot easier and save a lot of time. Hydraulic jacks are also used in homes for door stopper, cars, bikes, etc. but they are usually small in size. Hydraulic jacks are useful devices and convenient in use. Businesses that involved lifting or unloading of heavy objects these jacks are useful for doing this. Hydraulic brakes are used in motorbikes which makes the braking system efficient. Hydraulic jacks are used for multiple purposes according to the needs and requirements of people, these jacks are also needed in industries for lifting heavy objects, and multiple hydraulic jacks are needed in cranes in order to increase its functionality. If you need to install a hydraulic jack in your industry then you should consult to an experienced person because the jack should be installed properly in order to function effectively and the jack should be installed in such a way that it takes less space.

These jacks are easy to use and they are lightweight devices. If you have hydraulic jack then you don’t need to employ heavy duty and to buy expensive equipment in order to lift heavy objects. Hydraulic jacks make the process of lifting effortless and quick and also make the process safe, anyone can use this type of jack by doing proper care of it.

How Hydraulic Jack Works?

The hydraulic jack is a simple and easy to use device which lifts up heavy loads. It consists of two cylinders which are of different size one is larger than other these cylinders are used to hold the hydraulic fluid and there is a pumping system which consist of a pump used to apply pressure on the fluid the pump is either mechanically powered or hand pump. The hydraulic jack working is described below:

Working Pricinciple:

The main power source used by the hydraulic jacks is hydraulic fluid which is generally oil, and they create pressure by the movement of this oil in two cylinders through the plunger. As the one cylinder is larger than the other, the force produces by the larger one will be higher however, the pressure will equally build in both the cylinders. First, the oil is moved into the pump chamber in order to do so the pump plunger is pulled back, due to this movement of the plunger the suction valve will open up and oil moves into the chamber. Second, the oil is then moved into the cylinder chamber, to do so the pump plunger is pushed down due to which the oil is drawn into the cylinders by going through the external discharge valve. After this, the suction valve closes which results in creating a pressure in the chamber and due to this pressure, the piston of the chamber rises and this will help to lift up the heavyweight. Basically, the hydraulic jack working is based on the movement of hydraulic fluid from the pump chamber to the cylinders and this movement can be done many times in order to lift weight higher and higher.

Working Principle of Hydraulic Jack:
The hydraulic jack works on the simple principle i.e. Pascal principle. This principle was first developed by the French scientist named as Blaise Pascal. The Pascal law states that:

“Pressure applied at any point of a liquid enclosed in a container is transmitted without loss to all other parts of the liquid”.

In any liquid, enclosed in a container, the static pressure is applied to the walls of the container, this force is applied perpendicular to the walls and within the liquid. When the external pressure is applied to this static liquid then this pressure is equally distributed in all the directions of the liquid and this is called Pascal principle.

In order to understand this lets take an example of glass vessel which is filled with the water and there are holes in the vessel and there is a small piston on the top of the vessel as shown in figure 1 if we applied force on the piston then it will build pressure in the water and this pressure will distribute equally in all directions due to which water rushes out of the holes with the same pressure applied to the piston.

                                                             Figure 1

The formula discovered with this Pascal principle is as follows:

F1/A1 = F2/A2

Or we can rewrite this formula as:

F2= F1 * A2/A1


F1 = is the force applied to piston A.

F2 = is the force produced by the piston B.

A1 = is the area of piston A.

A2 = is the area of piston B.



Let’s say in a hydraulic system piston A has an area of 20 square centimeters on which force F1 of 30 newton is applied to the liquid in container and piston B which is connected by the pipe to the other end as shown in figure 2 has an area of 100 square centimeters, now what will be the force on the piston B?

Figure 2


F1 = 30 newton.

F2 =?

A1= 20 square centimeter.

A2 = 100 square centimeter.

Applying the formula of Pascal principle, we get:

F2= F1 * A2/A1

     = 30 x 100 / 20

     = 150 N.

This means that by applying a small force on piston A the much greater force will be produced on piston B which is used to lift the heavy weight easily without any effort.

Now I will describe the hydraulic jack working according to the Pascal principle.

The functioning of hydraulic jack can be described easily with Pascal’s principle, which states that the force applied to the enclosed liquid will distribute in all directions of the liquid equally. Hydraulic jack works on this simple principle which I have explained above with the examples. In the hydraulic jack when the plunger is activated it applies pressure on the hydraulic fluid which is generally oil, filled in the cylinder. As the one-way suction valve is enclosed completely and the cylinders are filled with fluid when the plunger is active, the pressure builds within the cylinders. The pressure wants to escape from the easiest way possible so it pulled up the piston on the other side connected with a pipe so it will lift whatever us on the plate placed on the other side. The pump applies this small force continuously multiple times on the hydraulic fluid until the fluid has enough pressure to lift up the weight placed on the jack, as shown in figure 3.

Figure 3

In order to fully understand the hydraulic jack working principle consider the images below:


In this there are ram and plunger operating in the two cylinders which are of different sizes and these cylinders are interconnected with the chamber at the bottom which is filled with the hydraulic fluid.


W = is the weight that we want to lift up.

F    = is the force we applied on the plunger.

A1 = is the area of the ram.

A2 = is the area of the plunger.

The pressure build by the applied force on the plunger will be equal to:

P = F / A2,

As the Pascal principle states that the above pressure will distribute equally in all directions, so the pressure build on the ram is equal to:

P = F / A2

P = W/ A1 or,

W = F * A1/A2.

This means that if we apply small force on plunger then the ram will produce much larger force W, which lifts our weight up.

Components of Hydraulic Jack:

Below is the hydraulic jack components diagram.

The main components of hydraulic jack are as follows:

  • Reservoir or buffer tank.
  • Pump.
  • Check valve.
  • Release valve.
  • Main or large cylinder.
  • Small Cylinder.

The explanation of the above components is described below.


The reservoir is basically a buffer tank which is used to store the hydraulic fluid i.e. oil and it also used to supply oil to pump and to store the oil which is returned back and also safe the hydraulic fluid from the external materials or impurities it also used to cool down the oil through its walls and allow impurities to settle at the bottom and air to separate.


The pump is used to transfer hydraulic fluid from one point to another, the resistance occurs in the flow of hydraulic fluid cause pressure to build up. Positive displacement pumps are used in hydraulics which transfers only a fixed amount of hydraulic fluid from suction irrespective of the weight that is going to be lifted. The air should not be entered in the pump if so, then it will cause aeration which means pump runs with high noise in order to get rid of this noise there should be sufficient oil in the reservoir.

Check Valve:

This is the valve which is used to flow the hydraulic oil in one direction only it is generally after the pump in order to take care of the pump’s reverse rotation. It is also known as a non-return valve.

Release Valve:

As the pump is used to increase the pressure of the hydraulic fluid and this pressure is moved toward the cylinders but if due to any reason the pump fails and the pressure becomes too large then it required to release that pressure in order to save jack from damage so this valve is used to release that pressure.

Main or Large Cylinder:

Two cylinders are used in the jack one is small and the other one is large, it is filled with the hydraulic fluid on the large cylinder the weight is placed that we are going to lift up.

Small Cylinder:

The small cylinder is used to apply pressure on the large cylinder. It is also filled with the hydraulic fluid i.e. oil.

Types of Hydraulic Jack:

There are two types of hydraulic jacks:

  • Floor Jack.
  • Bottle Jack.

Floor Jack:

A floor jack is commonly known as the tool for lifting vehicles like cars in order to change a tire or the car’s undercarriage. It is used to lift vehicles from one side from the ground and with the use of floor jack we can do this easily as floor jacks use hydraulics. Floor jacks are easy and safe to use if we used them according to the specifications of manufacturers. In order to use a jack, we have to place them on the ground. Floor Jacks are available in a variety of sizes and they lift weight according to their size.

Working of Floor Jack:

The floor jack is operated by placing it under the car or point from which we won’t lift up the car. The handle of the jack is pumped repeatedly this pumping sucks the oil from the reservoir of jack and builds up the pressure in the hydraulic fluid and this pressure is moved into the lift chamber due to this pressure the bearing pad of the jack begins to rise vertically and thus raise the weight i.e. car or anything.

Bottle Jack:

The popularity of bottle began to rise in early 1900 when the industry of automobile was taking off this type of jacks are easy to use for an individual in order to inspect the vehicle or to provide any other service they are also known as hand jacks. This type of jacks is named due to their cylinders which have resemblance with milk bottle they are used commonly in the industry of automobile because it is the simple way to raise and lower the vehicle. They are also used in other fields as warehouse load lifters, cable slicers, and stretcher lifts.

Working of Bottle Jack

The configuration of the bottle is that it consists of a vertical shaft which has a platform for lifting the weight on the top it carries the weight of the load. Bottle jack has also come in a manual form which consists of a pump and the user has to push this pump in order to lift the weight up. The bottle jack works in the following way:

The hydraulic fluid is pumped into the cylinder with an upstroke of jack’s handle and creates pressure in the hydraulic fluid this pressurized hydraulic fluid or oil is then moved to the main cylinder and raise the main piston with the downstroke of jack’s handle, this main piston will raise continuously and lift the weight up as the jack is pumped.

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