Question

Release valve is seen in
A. \[Hydraulic\text{ }breaks\]
B. \[Hydraulic\text{ }jack\]
C. \[Hydraulic\text{ }press\]
D. \[All\]

Answer 1

Hint: Release valves are used to release pressure. In order to lower the piston, manually operable release valves can be used to return the liquid to the reservoir which is provided near the base and remote from the actuating pump lever. When pressure is released load can be lowered so that the system can restart the cycle again.

Complete answer:
The release valve helps to reduce the pressure in a hydraulic jack. When the release valve is opened, fluid is ported back into the reservoir and the ram piston returns to the main cylinder. When the jack is in remote places it is dangerous for the operator to manipulate the valve to lower the pressure. Hence the release valves are provided at the base and away from the pump actuating lever.

So, the correct answer is “Option B”.

Additional Information:
Hydraulic jacks work under the concept of Pascal’s Principle which states that in a closed container, the pressure is the same at every point. It consists of two cylinders in which one is bigger than the other. When a pressure is applied to the cylinder containing fluid, the fluid will exert pressure throughout the volume. And the pressure will be magnified at the second cylinder with a larger area.
In other words, if two large and small cylinders are connected by an incompressible fluid and a given amount of pressure is applied to one cylinder, that same pressure is imparted to the second cylinder through the fluid connecting them. Larger cylinder has more area compared to the smaller one; it will experience a force multiplication effect. Even though the pressure on both cylinders is the same, the force produced on the larger cylinder will be higher.
Pascal’s law can be expressed as,
\[\dfrac{{{F}_{1}}}{{{A}_{1}}}=\dfrac{{{F}_{2}}}{{{A}_{2}}}\]
Where,
\[{{F}_{1}}\]= Force applied to piston 1.
\[{{F}_{2}}\]= Force applied to piston 2.
\[{{A}_{1}}\]= Area of piston 1
\[{{A}_{2}}\]= Area of piston 2

By rearranging the above equation, we get,
 \[{{F}_{2}}={{F}_{1}}\dfrac{{{A}_{2}}}{{{A}_{1}}}\]
The above equation illustrates that the applied force of a hydraulic jack is amplified directly by the ratio of the surface area of the two pistons.

Note:
There are two types of valves present in hydraulic systems. Relief Valves and release valves. Relief valves help to control pressure in a system. When the pressure reaches above a specific level, the relief valve responds and feeds the excess flow from the system back to the tank and stops after the preset limit is reached. Wherein release valves help to immediately release the pressure.