Bissoy.com
Doctors Medicines MCQs Q&A

Two centrifugal pumps 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 0.14 40 0.2 28 0.24 35 0.3 18 0.3 28   The following statements (S1, S2, and S3) pertain to the head and discharge values during actual operation. Neglect losses in the system. Which of the following statements are correct? S1: When the two pumps P and R are connected in parallel, the discharge is 0.36 cumecs corresponding to a head of 35 m. S2: When the two pumps P and R are connected in parallel, the discharge is 0.36 cumecs corresponding to a head of 70 m. S3: When the two pumps P and R are connected in series, the discharge is 0.3 cumecs corresponding to a head of 46 m.

Two centrifugal pumps 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 0.14 40 0.2 28 0.24 35 0.3 18 0.3 28   The following statements (S1, S2, and S3) pertain to the head and discharge values during actual operation. Neglect losses in the system. Which of the following statements are correct? S1: When the two pumps P and R are connected in parallel, the discharge is 0.36 cumecs corresponding to a head of 35 m. S2: When the two pumps P and R are connected in parallel, the discharge is 0.36 cumecs corresponding to a head of 70 m. S3: When the two pumps P and R are connected in series, the discharge is 0.3 cumecs corresponding to a head of 46 m. Correct Answer S1 and S3

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.

[ alt="F1 Shraddha Akhil 23.12.2021 D13" src="//storage.googleapis.com/tb-img/production/21/12/F1_Shraddha_Akhil_23.12.2021_D13.png" style="width: 272px; height: 121px;">

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 Q1 and Q2.
  • 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.

[ alt="F1 Shraddha Akhil 23.12.2021 D14" src="//storage.googleapis.com/tb-img/production/21/12/F1_Shraddha_Akhil_23.12.2021_D14.png" style="width: 245px; height: 184px;">

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

0.14

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

Related Questions

In the following question, two statements are numbered as A and B. On solving these statements, we get quantities A and B respectively. Solve both quantities and choose the correct option. Quantity A: Pipe A takes thrice the time taken by Pipe B to fill a tank. Together they can fill the tank in 15 hours, tank A and B is opened together for 4 hours and then Pipe A is closed and after 2 more hours Pipe B is closed and an outlet Pipe C is opened which when working alone can empty the tank in 10 hours. Calculate the time taken by C to empty the tank. Quantity B: A pipe A can fill the tank in 10 hours another pipe B can fill the tank in 15 hours and with the help of third pipe C they can fill the tank in 5 hours. Pipe A is opened for 4 hours then it is closed, pipe B is closed 3 hours before filling of tank and tank C is opened the whole time. Calculate the time taken to fill the tank
In the following question, two statements are numbered as A and B. On solving these statements, we get quantities A and B respectively. Solve both quantities and choose the correct option. Quantity A: Pipe A takes thrice the time taken by Pipe B to fill a tank. Together they can fill the tank in 15 hours, tank A and B is opened together for 4 hours and then Pipe A is closed and after 2 more hours Pipe B is closed and an outlet Pipe C is opened which when working alone can empty the tank in 10 hours. Calculate the time taken by C to empty the tank. Quantity B: A pipe A can fill the tank in 10 hours another pipe B can fill the tank in 15 hours and with the help of third pipe C they can fill the tank in 5 hours. Pipe A is opened for 4 hours then it is closed, pipe B is closed 3 hours before filling of tank and tank C is opened the whole time. Calculate the time taken to fill the tank.
Two pipes are connected to tank 1 and one pipe connects tank 1 and tank 2 at the bottom of both tanks. At first pipe A and pipe B will filling tank 1 and then pipe C would be opened to fill tank 2. Capacity of tank 1 is twice capacity of tank 2. Pipe C takes 8 minutes to fill the whole tank 2 wherein discharging capacity of pipe C is 62.5 liters per minute. Ratio of time taken by pipe A and B to fill the tank when operating alone is 4 : 5 then find approximate discharging capacity of pipe A and B in liters/ minute if both the pipes discharge equal amount of water in tank. Time taken by pipe A and B to fill the tank 1 is 20/ 3 minutes
Four pipes P, Q, R and S are connected to a tank. Pipe P, Q, R and S can fill the whole tank in 300/37 minutes. Ratio of time taken by pipe P to fill the tank when operating alone and pipe Q to fill the tank when operating alone is 3 : 2, pipe Q is 20% more efficient then pipe R and time taken by pipe S is 10 minutes more than pipe R. Find difference between time taken by pipe Q and pipe P to fill up the tank alone. 
Cconsider the following statements: 1. Pumps used in series are generally of the centrifugal type. 2. Centrifugal pumps, though yielding comparatively smaller discharges than axial flow pumps, yield higher heads (at each stage) compared to axial flow pumps. Which of the above statements is/are correct?
A container of 425 liters was filled with chemicals through two pipes. The first pipe was kept open for 5 hours more than the second pipe. If the first pipe remains open for as long as the second pipe remains open, and the second pipe remains open for as long as the first pipe remains open, then the quantity of chemical filled by the first pipe was half the quantity of chemical filled by the second pipe. If both the pipes are opened simultaneously, the tank will be filled in 17 hours. For how long was the second pipe open?
Pipe A takes 10 hours more than Pipe B to fill a tank. Pipe C(which is equally efficient as Pipe A and Pipe B together), fills the same tank in 12 hours. In how many hours will Pipe A, Pipe B and Pipe C fill the tank if Pipe A is accompanied by B and C on alternate hours.
To fill the tank Pipe A and Pipe B takes 12hours. Pipe B and Pipe C takes 9 hours to fill the tank and Pipe C and Pipe A together take 15 hours to fill the tank. Find the time taken to fill the tank when Pipe A, Pipe B and Pipe C opened together(approximately).
Pipe A is 40% more efficient then pipe E, Pipe B requires 4 minutes less to fill up the tank alone then pipe E, ratio of time taken by Pipe C and pipe A is 5 : 6, pipe C requires 15 minutes to empty the whole tank, if all the pipes are opened together then it requires 48/ 11 minutes to fill up the whole tank. Find the ratio of time taken by pipe B and pipe C to fill up the tank alone.
A pipe, working at full speed, can fill an empty cistern in 1 hour. However, during the first hour it worked at one-twenty-fourth of its capacity, during the second hour at one-twelfth of its capacity, during the third hour at one-eighth of its usual capacity, during the fourth hours at one-fourth of its usual capacity and during the fifth hour it was only one-half as efficient as it was supposed to be. A second pipe also displayed similar performance, but if it worked at full speed would have filled the empty cistern in 2 hours. Together with a drain pipe that drained water out of the tank a constant rate, the empty cistern could be filled in 5 hours, all the three pipe working concurrently. How many hours will it take the drain pipe to empty the filled cistern if no other pipe was functioning during the time?