Technician A says that hydraulic oil is not compressible.
Technician B says that hydraulic oil is less compressible than water.
Who is right?
A. Technician A only
B. Technician B only
C. Both A and B
D. Neither A nor B
The correct answer and explanation is :
The correct answer is B. Technician B only.
Explanation:
Hydraulic fluids, such as hydraulic oil, are designed to be incompressible to ensure efficient and predictable operation of hydraulic systems. However, it is important to understand the specifics of compressibility and how it compares to other fluids like water.
- Technician A’s statement: “Hydraulic oil is not compressible.”
- While hydraulic oils are often referred to as “incompressible” in practical terms, it is technically incorrect to say that hydraulic oils are completely incompressible. All fluids, including hydraulic oils, have a slight degree of compressibility, which becomes noticeable under extremely high pressures. The compressibility of a fluid refers to the change in volume that occurs when pressure is applied. Hydraulic oils, even though designed for minimal compressibility, do experience slight volume reductions under high pressure.
- Technician B’s statement: “Hydraulic oil is less compressible than water.”
- This statement is correct. Water, being less viscous and having a different molecular structure, is more compressible than hydraulic oil. Water has a higher bulk modulus, which refers to the measure of the resistance of a fluid to compression. Hydraulic oils are typically formulated with additives and have higher viscosities, making them less compressible than water. This means that under the same pressure, hydraulic oils will experience less change in volume compared to water.
Why Technician B is correct:
The compressibility of a fluid is determined by its bulk modulus. Hydraulic oils generally have a higher bulk modulus than water, meaning that they are less compressible. This is a key reason why hydraulic systems are designed with oils instead of water—the minimal compressibility of hydraulic oil ensures that the force applied in the system is more predictable and efficient.
In summary, Technician B is correct because hydraulic oil is less compressible than water, even though both are slightly compressible.