Reciprocating pump with air vessel — percentage saving of work By fitting an air vessel to a reciprocating pump, work and power savings occur due to flow smoothing. What is the typical percentage saving for a double-acting reciprocating pump?
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A39.2%
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B48.8%
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C84.8%
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D88.4%
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E24.4%
Answer
Correct Answer: 48.8%
Explanation
Introduction:Air vessels are used on suction and delivery lines of reciprocating pumps to reduce acceleration head, smoothen discharge, and lower the fluctuating power requirement. The percentage saving differs between single-acting and double-acting pumps because the flow pulsation patterns differ.
Given Data / Assumptions:
- Double-acting reciprocating pump.
- Idealized analysis of acceleration head reduction with properly sized air vessels.
Concept / Approach:The principal benefit is the reduction of periodic acceleration and deceleration of the fluid column. This reduces pressure fluctuations and the corresponding work over a cycle. Standard results show that for single-acting pumps the saving is higher, whereas for double-acting pumps it is approximately half that magnitude due to inherently smoother flow.
Step-by-Step Solution:
Recall typical results: single-acting ≈ 84.8% savingFor double-acting: ≈ 48.8% savingThus, select 48.8% for a double-acting pumpVerification / Alternative check:These percentages appear consistently in standard fluid machinery texts. Practical installations show significant reduction in pressure pulsations and motor size for the same duty.
Why Other Options Are Wrong:
- 39.2% / 24.4%: lower than the accepted value for double-acting arrangements.
- 84.8% / 88.4%: align more with single-acting results or exceed typical theoretical values.
Common Pitfalls:Mixing up single- and double-acting savings; assuming air vessels eliminate all fluctuations (they reduce, not remove, pulsations).
Final Answer:
48.8%