Exam Question
If a radial piston hydraulic pump fails to deliver rated fluid volume, the cause can be (16)
(a) Contaminated fluid
(b) Pitted thrust rings
(c) Worn pintle bearings
(d) Obstructed suctions passage
Briefly justify your answer.
Class 4 (4th Engineer)
MEKG
📅 Jun 2024
Reference Answer
The correct answer is **(d) Obstructed suction passage**.
### Justification for (d) Obstructed Suction Passage
A hydraulic pump is a positive displacement machine. Its theoretical output volume is a direct function of its displacement (volume per revolution) and rotational speed. For a pump to deliver its rated volume, it must first be able to completely fill its displacement chambers (cylinders) during the suction stroke. An obstructed suction passage is the most direct and immediate cause of failure to achieve this, a condition known as **pump starvation**.
1. **Principle of Operation**: During the suction stroke, the pistons move outwards, creating a low-pressure area within the cylinders. The higher atmospheric or head pressure in the reservoir then pushes the hydraulic fluid into these cylinders via the suction passage and the pintle valve.
### Justification for (d) Obstructed Suction Passage
A hydraulic pump is a positive displacement machine. Its theoretical output volume is a direct function of its displacement (volume per revolution) and rotational speed. For a pump to deliver its rated volume, it must first be able to completely fill its displacement chambers (cylinders) during the suction stroke. An obstructed suction passage is the most direct and immediate cause of failure to achieve this, a condition known as **pump starvation**.
1. **Principle of Operation**: During the suction stroke, the pistons move outwards, creating a low-pressure area within the cylinders. The higher atmospheric or head pressure in the reservoir then pushes the hydraulic fluid into these cylinders via the suction passage and the pintle valve.
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