Question

Given below are two statements:
Statement (I): A closed-central valve has land width greater than the port width when the spool is in centre
Statement (II): An accumulator in hydraulic systems is used to supply energy when the demand of motors and cylinders is greater than the capacity of pump

In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are true.
• B. Both Statement (I) and Statement (II) are false.
• C. Statement (I) is true but Statement (II) is false.
• D. Statement (I) is incorrect but Statement (II) is true.

Hint:

A spool valve with land width equal to port width has zero overlap (critical center).
A closed-center valve requires positive overlap (land width $\gt $ port width) to guarantee no leakage in neutral.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Spool design parameters in hydraulic control valves determine fluid flow paths.
Accumulators store hydraulic energy under pressure to stabilize circuit flow.

Step 3: Detailed Explanation:
1.

Statement (I): In a closed-center spool valve, the flow of hydraulic fluid must be completely blocked when the spool is in its neutral (center) position.
To guarantee complete closure and prevent high-pressure internal leakage across the clearance, the land width of the sliding spool must be slightly greater than the port opening width (a condition known as positive overlap). Thus, Statement (I) is true.
2.

Statement (II): A hydraulic accumulator stores pressurized fluid during periods of low actuator demand.
When actuators (motors/cylinders) require a sudden surge of flow that exceeds the pump's displacement capacity, the accumulator discharges its stored fluid to supplement the pump flow. Thus, Statement (II) is true.

Step 4: Final Answer:
The correct option is 1, which corresponds to "Both Statement (I) and Statement (II) are true."