Reciprocating Pump MCQ Quiz - Objective Question with Answer for Reciprocating Pump - Download Free PDF
Last updated on May 12, 2025
Latest Reciprocating Pump MCQ Objective Questions
Reciprocating Pump Question 1:
If a pump’s theoretical manometric head is 30 metres and its measured head is 27 metres, what is its manometric efficiency?
Answer (Detailed Solution Below)
Reciprocating Pump Question 1 Detailed Solution
Explanation:
To determine the manometric efficiency of the pump, we need to use the formula for manometric efficiency (
The formula for manometric efficiency is given by:
In this case, the theoretical manometric head is 30 meters, and the measured head is 27 meters.
Substituting these values into the formula, we get:
Therefore, the manometric efficiency of the pump is 0.9 or 90%, which corresponds to option 3.
Now, let's analyze the other options to understand why they are incorrect:
- Option 1: 0.75 - This value would be obtained if the measured head was 22.5 meters (0.75 × 30 meters), which is not the case here.
- Option 2: 0.85 - This value would be obtained if the measured head was 25.5 meters (0.85 × 30 meters), which is not the case here.
- Option 4: 0.8 - This value would be obtained if the measured head was 24 meters (0.8 × 30 meters), which is not the case here.
All these options do not match the given data, which indicates that the correct answer is indeed option 3.
Important Information:
Understanding manometric efficiency is crucial for evaluating the performance of pumps. Manometric efficiency helps in determining how effectively a pump converts the energy supplied to it into useful work. High manometric efficiency indicates that the pump is effectively converting the input energy into the desired output in terms of head, while low manometric efficiency suggests energy losses within the pump system. The efficiency can be impacted by various factors such as mechanical losses, hydraulic losses, and leakage, which need to be minimized to ensure optimal pump performance. Regular maintenance and proper design can help in achieving and maintaining high manometric efficiency.
Reciprocating Pump Question 2:
In a reciprocating pump, which of the following options connects the piston to the crankshaft?
Answer (Detailed Solution Below)
Reciprocating Pump Question 2 Detailed Solution
Explanation:
Connecting rod
- In a reciprocating pump, the connecting rod connects the piston to the crankshaft.
- It transmits the rotational motion of the crankshaft to the linear motion of the piston, enabling the pump to move fluid through the system.
Additional Information
Reciprocating Pump:
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A reciprocating pump is a positive displacement pump that uses a piston to move fluid.
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It operates by the back-and-forth (reciprocating) motion of the piston inside a cylinder, which creates a vacuum to draw in fluid during the suction stroke and forces it out during the discharge stroke.
Connecting Rod:
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The connecting rod plays a crucial role in converting the rotary motion of the crankshaft into the linear reciprocating motion of the piston.
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It connects the piston to the crankshaft and is typically made of strong materials like steel.
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During the operation of the pump, the crankshaft rotates, and the connecting rod transmits the rotational force to the piston, causing it to move back and forth within the cylinder.
Crankshaft and Bearings:
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The crankshaft is responsible for converting rotational motion into the reciprocating motion of the piston.
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Bearings support the crankshaft and reduce friction during its rotation.
Suction and Delivery Pipes:
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The suction pipe brings fluid into the pump, and the delivery pipe carries the fluid out of the pump once it’s displaced by the piston.
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These pipes are connected to the inlet and outlet of the pump, but they don’t connect the piston to the crankshaft.
Applications:
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Reciprocating pumps are commonly used in applications requiring precise fluid transfer, such as in hydraulic systems, high-pressure water pumps, and in industries where accurate flow control is important.
Reciprocating Pump Question 3:
Consider the following statements regarding reciprocating pump -
(1) Frictional losses are maximum at the middle of the stroke.
(2) maximum inertia effect occurs in place with zero frictional losses.
(3) Negative slip may occur when the delivery head is high.
Which of the above statements are corrects?
Answer (Detailed Solution Below)
Reciprocating Pump Question 3 Detailed Solution
Concept:
Reciprocating pumps are positive displacement pumps that use a piston or plunger to move fluid. Understanding the dynamics and losses associated with reciprocating pumps is essential for efficient design and operation.
∴ Frictional losses, inertia effects, and slip are critical factors to consider in reciprocating pumps.
Statement (1): In a reciprocating pump, the velocity of the fluid in the suction or delivery pipe varies with the position of the piston during its stroke. The fluid velocity is maximum at the middle of the piston stroke, as this is when the piston reaches its highest speed. Frictional losses are proportional to the square of the fluid velocity: hf ∝ v2. Since the fluid velocity is highest at the middle of the stroke, the frictional losses in the pipe are also highest at this point.
Statement (2): Maximum inertia effect occurs in place with zero frictional losses. This is correct because the inertia effect is related to the acceleration and deceleration of the piston, which is maximum where there is no frictional loss to counteract it.
Statement (3): Negative slip may occur when the delivery head is high. This is incorrect because negative slip usually occurs when the pump is running at a higher speed, causing the actual discharge to be higher than the theoretical discharge due to the fluid's inertia.
Reciprocating Pump Question 4:
Which of the following statements is correct about negative slip in a reciprocating pump?
Answer (Detailed Solution Below)
Reciprocating Pump Question 4 Detailed Solution
Concept:
Slip:
- It is the difference between the theoretical discharge and actual discharge.
Slip = Qthe - Qact
Positive slip:
- When the theoretical discharge is more than actual discharge is known as positive slip. i.e. Qthe > Qact
Negative slip:
- When the theoretical discharge is less than actual discharge is known as negative slip. i.e. Qthe < Qact
Conditions of "Negative slip":
- Due to High speed
- Due to short delivery pipe
- Due to long suction pipe
This happen because of inertia pressure in suction pipe will be large as compared to pressure of the delivery valve. This causes delivery valve open before suction stroke is completed.
Coefficient of discharge
Cd = \(\frac{Q_{act}}{Q_{the}} \) and % slip = \(\frac{{Q_{the}}-~Q_{act}}{Q_{the}}\)
Reciprocating Pump Question 5:
Which of the following statements is INCORRECT about double acting reciprocating pump?
Answer (Detailed Solution Below)
Reciprocating Pump Question 5 Detailed Solution
Explanation:
Reciprocating Pump:
- A reciprocating pump is a positive displacement pump as sucks and raises the liquid by actually displacing it with a piston or plunger that executes a reciprocating motion in a closely fitted cylinder.
- The amount of liquid pumped is equal to the volume displaced by the piston.
- The reciprocating pump is best suited for relatively small capacities and high heads.
Single-Acting reciprocating pump:
- A single-acting reciprocating pump has one suction pipe and one delivery pipe.
- Initially, the crank is at the inner dead centre and rotates in the clockwise direction. As the crank rotates the piston moves towards the right and a vacuum is created on the left side of the piston. This vacuum causes the suction valve to open and consequently the liquid is forced from the sump to the left side of the piston.
- When the crank is outer dead centre the suction stroke is completed.
- When the crank turns from ODC to IDC, the piston moves inward to the left, and high pressure builds up in the cylinder.
Double-acting reciprocating pump:
- In a double-acting reciprocating pump, suction and delivery strokes occur simultaneously.
- When the crank rotates from IDC in a clockwise direction, a vacuum is created on the left side of the piston and the liquid is sucked in from the sump through valve S1. At the same time, the liquid on the right side of the piston is pressed and high pressure causes the delivery valve D2 to open and the liquid is passed on to the discharge tank. This operation continues till the crank reaches ODC.
- Because of continuous delivery strokes, a double-acting reciprocating pump gives a more uniform discharge.
Top Reciprocating Pump MCQ Objective Questions
Which of the following is a positive displacement pump?
Answer (Detailed Solution Below)
Reciprocating Pump Question 6 Detailed Solution
Download Solution PDFExplanation:
Positive displacement pump:
- Positive displacement pumps are those pumps in which the liquid is sucked and then it is pushed or displaced to the thrust exerted on it by a moving member, which results in lifting the liquid to the required height.
- Reciprocating pump, Vane pump, Lobe pump are the examples of positive displacement pump whereas the centrifugal pump is the non-positive displacement pump.
The theoretical power (in h.p.) required to drive a reciprocating pump is
Where w = specific weight of liquid to be pumped
Q = discharge of the pump in m3/s
Hs = suction head in m
Hd = delivery head in m
Answer (Detailed Solution Below)
Reciprocating Pump Question 7 Detailed Solution
Download Solution PDFConcept:
Reciprocating Pump:
- A reciprocating pump is a positive displacement pump as sucks and raises the liquid by actually displacing it with a piston or plunger that executes a reciprocating motion in a closely fitted cylinder.
- The amount of liquid pumped is equal to the volume displaced by the piston.
- The reciprocating pump is best suited for relatively small capacities and high heads.
Discharge through a pump per second:
\(Q = \frac{{ALN}}{{60}}\)
Discharge for a double-acting pump:
\(Q = 2\frac{{ALN}}{{60}}\)
where, A = Area of piston; L = Stroke length
Hnet = hd + hs = Total height through which water is lifted
Hence, the power required is given by
P = Q ρ g Hnet
P = Q ρ g (hd + hs) (in W) = \(\frac{{wQ\space ({H_s}\space +\space {H_d})}}{{75}}\)(in h.p.)
In a reciprocating pump, air vessels are used to
Answer (Detailed Solution Below)
Reciprocating Pump Question 8 Detailed Solution
Download Solution PDFExplanation:
- The air vessel, in a reciprocating pump, is a cast iron closed chamber having an opening at its base.
- These are fitted to the suction pipe and delivery pipe close to the cylinder of the pump.
The vessels are used for the following purposes,
- To get continuous supply of liquid at a uniform rate.
- To save the power required to drive the pump. This is due to the fact that by using air vessels, the acceleration and friction heads are reduced. Thus, the work is also reduced.
Note:
It may be noted that by fitting an air vessel to the reciprocating pump, the saving of work and subsequently the power is about 84.8 % in case of a single acting reciprocating pump and 39.2 % in case of double acting reciprocating pump.
What is the discharge capacity of the reciprocating pump as compared to the centrifugal pump?
Answer (Detailed Solution Below)
Reciprocating Pump Question 9 Detailed Solution
Download Solution PDFThe hydraulic machines which convert the mechanical energy into hydraulic energy are called pumps.
Classification of pump.
Centrifugal pumps |
Reciprocating pumps |
The discharge is continuous and smooth |
The discharge is fluctuating and pulsating |
It can handle a large quantity (Discharge) of liquid |
It handles a small quantity (Discharge) of liquid only |
It can be used for lifting highly viscous liquids |
It is used only for lifting pure or less viscous liquids |
It is used for large discharge through smaller heads |
It is meant for a small discharge and high heads |
Cost of a centrifugal pump is less as compared to reciprocating pump |
Cost of a reciprocating pump is approximately four times the cost of a centrifugal pump |
Centrifugal pump runs at high speed. They can be coupled to an electric motor |
It runs at low speed. Speed is limited due to consideration of separation and cavitation |
The operation of a centrifugal pump is smooth and without much noise. The maintenance cost is low |
The operation of a reciprocating pump is complicated and with much noise. The maintenance cost is high. |
It requires a smaller floor area and installation cost is low |
It requires a larger floor area and installation cost is high |
Efficiency is low |
Efficiency is high |
Which of the following is not a correct statement for a reciprocating pump?
Answer (Detailed Solution Below)
Reciprocating Pump Question 10 Detailed Solution
Download Solution PDFExplanation:
Reciprocating Pump:
- A reciprocating pump is a positive displacement pump as sucks and raises the liquid by actually displacing it with a piston or plunger that executes a reciprocating motion in a closely fitted cylinder.
- The amount of liquid pumped is equal to the volume displaced by the piston.
- The reciprocating pump is best suited for relatively small capacities and high heads.
Single-Acting reciprocating pump:
- A single-acting reciprocating pump has one suction pipe and one delivery pipe.
- Initially, the crank is at the inner dead centre and rotates in the clockwise direction. As the crank rotates the piston moves towards the right and a vacuum is created on the left side of the piston. This vacuum causes the suction valve to open and consequently the liquid is forced from the sump to the left side of the piston.
- When the crank is outer dead centre the suction stroke is completed.
- When the crank turns from ODC to IDC, the piston moves inward to the left, and high pressure builds up in the cylinder.
Double-acting reciprocating pump:
- In a double-acting reciprocating pump, suction and delivery strokes occur simultaneously.
- When the crank rotates from IDC in a clockwise direction, a vacuum is created on the left side of the piston and the liquid is sucked in from the sump through valve S1. At the same time, the liquid on the right side of the piston is pressed and high pressure causes the delivery valve D2 to open and the liquid is passed on to the discharge tank. This operation continues till the crank reaches ODC.
- Because of continuous delivery strokes, a double-acting reciprocating pump gives a more uniform discharge.
Air vessels:
- An air vessel is a closed chamber containing compressed air in the upper part and liquid being pumped in the lower part.
- One air vessel is fixed on the suction pipe just near the suction valve and one is fixed on the delivery pipe.
The air vessels are used for the following purposes:
- To get a continuous supply of liquid at a uniform rate.
- To save the power required to drive the pump (By the use of air vessels, the acceleration and friction heads are considerably reduced and the work is also reduced).
- To run the pump at a much higher speed without any danger of separation (By fitting the air vessels as close to the pump as possible, the length of the pipe in which acceleration takes place is reduced due to which acceleration head is reduced, and the pump can run at a high speed without separation).
The percentage of work saved in pipe friction by fitting air vessels in the case of a single-acting reciprocating pump is approximately 84.8% and in the case of double-acting, it is approximately 39.2 %.
A single-acting reciprocating pump has a 15 cm piston with a crank radius of 15 cm. The delivery pipe is 10 cm in diameter. At a speed of 60 rpm, 310 litres /minute of water is lifted to a height of 15 cm. Find the coefficient of discharge.
Answer (Detailed Solution Below)
Reciprocating Pump Question 11 Detailed Solution
Download Solution PDFExplanation:
Theoretical discharge from a single-acting reciprocating pump:
\(Q_{th}={LAN\over 60}\)
Where L = Stroke length = 2 × crank radius
A = Area of Piston
N = Pump rotation in rpm
Calculation:
Given data:
Piston diameter (d) =15 cm or 0.15 m
Crank radius (r) = 15 cm or 0.15 m
Diameter of delivery pipe (D) = 10 cm
L = 0.30 m
Pump rotation (N) = 60 rpm
Actual discharge (Qact) = 310 liters/minute
Lifting height (h) = 15 cm
Coefficient of discharge (Cd) =?
\(Q_{th}={0.30× 60×({\pi \over 4})× 0.15^2\over 60}\)
\(Q_{th}=0.00530\, m^3/s\)
given, \(Q_{act}=310\, liters/minute\)
1000 liters = 1 m3
\(Q_{act}={310\over 1000× 60}\, m^3/s\)
\(Q_{act}=0.00516\, m^3/s\)
\(Coefficient\, of\, discharge\,(C_d)={Actual\, discharge\,(Q_{act})\over Theoretical\, discharge\,(Q_{th})}\)
\(C_d={0.00516\over 0.00530}=0.9735\approx 0.974\)
\(C_{d}=0.974\)
Hence, the most appropriate answer is option 4.
Negative slip occurs in reciprocating pumps, when delivery pipe is
Answer (Detailed Solution Below)
Reciprocating Pump Question 12 Detailed Solution
Download Solution PDFConcept:
Slip: It is the difference between the theoretical discharge and actual discharge.
Slip = Qthe - Qact
Positive slip: When the theoretical discharge is more than actual discharge is known as positive slip. i.e. Qthe > Qact
Negative slip: When the theoretical discharge is less than actual discharge is known as negative slip. i.e. Qthe < Qact
Conditions of "Negative slip":
- Due to High speed
- Due to short delivery pipe
- Due to long suction pipe
This happen because of inertia pressure in suction pipe will be large as compared to pressure of the delivery valve. This causes delivery valve open before suction stroke is completed.
Coefficient of discharge
Cd = \(\frac{Q_{act}}{Q_{the}} \) and % slip = \(\frac{{Q_{the}}-~Q_{act}}{Q_{the}}\)
The air vessel in a reciprocating pump is:
Answer (Detailed Solution Below)
Reciprocating Pump Question 13 Detailed Solution
Download Solution PDFExplanation:
Air vessel:
- It is a closed chamber fitted on the suction as well as delivery side, near the pump cylinder to reduce the accelerating head.
- To reduce the acceleration head we need to reduce the length of the suction pipe and the length of the delivery pipe in which fluctuation of velocity occurs.
- This is done by fitting air vessels as close as possible.
- Thus between air vessel and cylinder only fluctuating velocity will occur. Below air vessel on the suction side and above air vessel on delivery side velocity will be constant.
Functions of air vessel:
1) On the suction side:
- Reduction of the possibility of separation of flow
- The pump can run at a higher speed.
- The length of the suction pipe below the air vessel can be increased.
2) On the delivery side:
- A constant rate of discharge can be ensured.
- Save power required to drive the pump (For single-acting pump, percentage work saved is 84.8% and for double-acting pumps the percent work save is 39.2%)
A positive displacement pump has an overall efficiency of 88% and a volumetric efficiency of 92%. What is the mechanical efficiency?
Answer (Detailed Solution Below)
Reciprocating Pump Question 14 Detailed Solution
Download Solution PDFExplanation:
In the case of a centrifugal pump, the power is transmitted from the shaft of the pump to the impeller and then from the impeller to the water. The following are the important efficiencies of a centrifugal pump:
- Manometric Efficiency (ηman): It is the ratio of the manometric head to head imparted by the impeller to the water.
\({η _{man}} = \frac{{{H_m}}}{{\frac{{{V_{w2}}{u_2}}}{g}}} = \frac{{g{H_m}}}{{{V_{w2}}{u_2}}}\)
- Mechanical Efficiency (ηm): It is the ratio of the power available at the impeller to the power at the shaft of the centrifugal pump.
\({η _m} = \frac{{{\rm{Power\;at\;the\;impeller}}}}{{{\rm{Power\;at\;the\;shaft}}}} = \frac{{\frac{W}{g}\left( {\frac{{{V_{w2}}{u_2}}}{{1000}}} \right)}}{{{\rm{SP}}}}\)
\(\rm n_m=\frac{p-p_{mech\ loss}}{p}\)
- Overall Efficiency (ηo): It is defined as a ratio of the power output of the pump to the power input to the pump.
ηo = ηman × ηm
Calculation:
Given:
ηo = 88%, ηvol = 92%
88 = 92 × ηm
ηm = 95.65%
What will be the theoretical discharge of a double-acting reciprocating pump? (Stroke length = 250 mm, bore = 150 mm and crank speed = 60 rpm)
Answer (Detailed Solution Below)
Reciprocating Pump Question 15 Detailed Solution
Download Solution PDFConcept:
Discharge through a reciprocating pump:
- The discharge in m3/min through a single acting reciprocating pump is given as
- Q = Volume of water delivered in one revolution × number of revolutions per minute
- Q = V × N
- Q = (Length of stroke × Area) × N
- Q = LAN
For a single-acting reciprocating pump
- Q = LAN
For a double-acting reciprocating pump
- Q = 2LAN
Calculation:
Given:
L = 250 mm = 0.25 m, D = 150 mm = 0.15 m, N = 60 rpm
\(A=\frac{\pi}{4} \times D^2\)
\(A=\frac{\pi}{4} \times 0.15^2=0.0176~m^2\)
Q = 2 × L × A × N
Q = 2 × 0.25 × 0.0176 × 60 = 0.53 m3/min = 530 liter/min = 8.8 liter/sec
Hence the required discharge will be 8.8 liter/sec