SSC JE Civil Engineering 23-Mar-2021 Shift 1 Paper

Concept:
Pump in Series:
● In a series arrangement, each pump handles the same flow rate, but the total head produced by the combination of pumps will be additive. Since each pump generates a head H corresponding to a flow Q.
● When connected in series, the total head developed is Ht=H1+H2 , where H1, H2 are the heads developed by the pump in series at the common flow rate Q. Pump in Parallel:
● With pumps in parallel, the flow rates are additive with a common head. The flow rate Qt(Qt=Q1+Q2) is split between the inlet into Q1‌and‌Q2 .
● Each pump develops the same head H at the corresponding capacity. Thus, the first pump at capacity Q1 develops the same head H as the second pump at capacity Q2 . Explanation:
Given Data:
P and R are available for use in a pipe flow system and their head-discharge characteristics are as follows.

Pump P		Pump R
Discharge(cumecs)	Head(m)	Discharge(cumecs)	Head(m)
0	40	0	45
0.12	35	.014	40
0.2	28	0.24	35
0.3	18	0.3	28

When P and R in Series:
Flow rate is the same in P and R pump(Q) = 0.3 cumecs
So, the corresponding Head( Ht )
Ht = H1+H2
where H1 = 18 m and H2 = 28 m
Head(Ht) = H1 + H2 = 18 + 28 = 46 m
Hence S3 Statement is correct
When P and R in Parallel:
Head is the same in P and R pump(H) = 35 m
So, the corresponding flow rate(Qt)
Qt=Q1+Q2
where Q1 = 0.12 cumecs and Q2 = 0.24 cumecs
flow rate(Qt) = Q1+Q2 = 0.12 + 0.24 = 0.36 cumecs
Hence S1 Statement is correct