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Grade 9

Hydraulic and pneumatic systems

Module 12

How valves function in hydraulic systems


To be able to describe the functioning of valves in hydraulic systems

[LO 2.3]

The simplest valve is the one-way valve. It is used to keep the piston that moved up as a result of pressure on the hydraulic liquid, in position.

The valve is necessary because unlike gases, liquid cannot be compressed. The functioning of a valve can be explained as follows:

1. In the figure a force is exerted on the piston of cylinder A and is transmitted through the liquid as pressure. This causes cylinder B to rise and to experience a force.

Should the force be removed, piston B will fall back again.

2. This can be prevented by using a valve that moves to the right when the force is exerted on piston A and moves to the left when the force is removed.

Pressure is distributed to the right through liquid and then the valve also moves to the right.

3. When pressure is no longer being exerted, the liquid recedes and the spring then forces the valve to move to the left.

The valve closes as a result of the liquid that recedes when the force is removed and this allows the spring to push the valve to the left.


Study figures 1 and 2 and answer the questions:

A single hydraulic jack consists of a small input piston, A, and a larger output piston, B. The oil is stored in the reservoir and is let into the system at point C.

A small force is exerted on the small area of the input piston, A, through the action of the lever. This causes a small amount of oil to move from the reservoir into the main cylinder, D. The one-way valve prevents the piston, B from moving back after the first pumping action, and in this way a great force is lifted little by little gradually lifting the car.

1. What is the function of the valves in both figure 1 and figure 2?

2. Why must the lever move back and forth in order to raise piston, B to the top?

3. Why is the diameter of the input cylinder smaller than that of the output cylinder?


LO 2
TECHNOLOGICAL KNOWLEDGE AND UNDERSTANDINGThe learner will be able to understand and apply relevant technological knowledge ethically and responsibly.
We know this when the learner:
systems and control:2.3 demonstrates knowledge and understanding of interacting mechanical systems and sub-systems by practical analysis and represents them using systems diagrams:gear systemsbelt drive or pulley systems with more than one stage;mechanical control mechanisms (e.g. ratchet and pawl, cleats);pneumatic or hydraulic systems that use restrictorsone-way valves;systems where mechanical, electrical, or pneumatic or hydraulic systems are combined.



1. Prevents the reverse flow of the liquid/fluid so that the piston/plunger remains in position and the pressure is maintained.

2. When the lever moves upwards, a small amount of oil is released from the reservoir to the small cylinder.

When the lever moves downwards and input force is brought to bear on the small cylinder, the oil flows through the one-way valve to the large cylinder. The pressure is propagated through the liquid according to Pascal's principle and provides a great output force on the large cylinder.

When the lever is raised again, the one-way valve shuts and the oil is unable to flow back. This maintains the power advantage. The process is repeated from the beginning.

3. A small force on a small cylinder provides great force on a large cylinder.

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
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Source:  OpenStax, Technology grade 9. OpenStax CNX. Sep 15, 2009 Download for free at http://cnx.org/content/col11071/1.1
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