Weekly Q/A by Pumpsense

Weekly Q/A List :

Q1 : Which of the following is not a primary function of the pump casing?

a. Transmit torque from the driver to the impeller
b. To convert kinetic energy into pressure energy
c. To develop dynamic head
d. Directing flow into and out of impeller
e. Provide support to the bearing bracket
f. Incorporate nozzles to connect suction & discharge piping.

Q2 : A pump develops 100 m head while handling kerosene with specific gravity of 0.8. What head will the pump develop if the liquid handled is water:

a. 120m
b. 100m
c. 80m
d. 60m

Q3 : A pump lifts water from a sump. Static height of the pump center line from the water level in the sump is 5m. Friction loss in the suction pipe line 0.5m, vapor pressure at pumping temperature is 0.5m and the atmospheric pressure is 10.3m of water column. What is the approximate NPSH available at this installation?

a. 14.3 m
b. 4.3 m
c. 4.8 m
d. 14.8 m

Q4 : Which of the following statements about cavitation is not true?

a. Cavitation occurs when NPSH available is less than the NPSH required by the pump.
b. Cavitation is caused by the collapse of air bubbles in the suction side of the pump.
c. Cavitation does not occur during part flow operation since available NPSH is high.
d. Cavitation occurs only on the suction side of the impellers.
e. Cast Iron impellers have the least ability to resist cavitation damage.

Q5 : The following diagram shows pump performance curve superimposed on system characteristics. Can you identify the various terms in the table?

Description

a. System Resistance Curve
b. Friction Head
c. Static Head
d. Total Dynamic Head
e. Head Capacity Curve
f. Operating Point

A. (a) - 2 (b) - 5 (c) - 4 (d) - 6 (e) - 1 (f) - 3
B. (a) - 1 (b) - 4 (c) - 6 (d) - 5 (e) - 2 (f) - 3
C. (a) - 2 (b) - 6 (c) - 4 (d) - 5 (e) - 1 (f) - 3
D. (a) - 1 (b) - 4 (c) - 5 (d) - 6 (e) - 2 (f) - 3

Q6 : For each of the following duties which is the most appropriate type of impeller:

a. Radial flow
b. Francis Vane
c. Mixed Flow
d. Axial Flow

1. c - b - a - d
2. a - d - b - c
3. d - a - b - c
4. b - a - d - c

Q7 : In a pumping system where the major component of the total head is friction, which of the following three methods of flow control is the most energy efficient? The flow through a pump can be controlled by:

a) Throttling
b) Connecting or disconnecting pump running in series or parallel
c) Speed control

Q8 : Which of the following properties are important for selecting the material of construction of an impeller:

a) Endurance Limit
b) Corrosion Resistance
c) Abrasive Wear Resistance
d) Cavitation Resistance
e) Casting and machining properties
f) Tip speed
g) Cost
h) Working Pressure
i) Galling Characteristics

Q9 : According to American Standard NFPA20 for fire pumps, pumps are generally provided with gland packing and mechanical seals are not used. What is the main reason for using gland packing in place of mechanical seals for these pumps?

a) Gland Packing is easily installed.
b) Gland Packing is cheaper than mechanical seal.
c) Leakage tends to increase gradually giving early indication of impending failure.
d) Gland Packing is less sensitive to the axial movement of shaft compared to mechanical seal.
e) Gland Packing is easily replaced when the gland is split.

Q10 : The following is a list of some of the Quality Assurance checks carried out by a pump manufacturer:

a) Shaft Ultrasonic test
b) Casing UTS, hardness test, chemical test
c) Impeller - chemical analysis
d) Impeller – dynamic balancing
e) Casing - hydrostatic pressure test
f) Pump - Performance test
g) Pump - dimensional check
h) NPSH test

The following is a list of the Test Reports as required by a user:

Please identify the QA document which contains the appropriate test report from the following options:

A.	B.
C.	D.

Q11 : Which of the following impeller types has the highest efficiency potential?

a) Radial flow impeller
b) Francis Vane impeller
c) Mixed flow impeller
d) Axial flow impeller

Q12 : The following are four End Suction ISO 2858 pumps. Pump efficiencies are

1. 72%
2. 75%
3. 81%
4. 83%

Can you place the correct efficiencies in the appropriate boxes?

Pump Size	Best efficiency duty point at 1480 rpm	Efficiency
A. 125x80-400	140 m3/hr, 50m
B. 125x100-400	190 m3/hr, 50m
C. 150x125-400	300 m3/hr, 50m
D. 200x150-400	450 m3/hr, 50m

a) A-1 B-2 C-3 D-4
b) A-4 B-3 C-2 D-1
c) A-3 B-1 C-2 D-4
d) A-2 B-4 C-3 D-1

All the pumps generate the same head and impeller diameters are identical (400mm) - Why are the efficiencies different?

Q13 : Select the Pumps for the given duty points:

S/N	SPEED (RPM)	HEAD (m)	FLOW (Litre Per Sec)
1	1480	20	100 LPS
2	1480	22	140 LPS
3	1000	80	564 LPS
4	1480	100	564 LPS

a) 1: 6HS14 2: 8HS10 3: 16HS32 4: 12HS23
b) 1: 8HS12 2: 8HS12 3: 14HS32 4: 14HS26
c) 1: 6HS12 2: 8HS12 3: 16HS32 4: 12HS23
d) 1: 6HS10 2: 10HS12 3: 18HS25 4: 10HS22

Q14 : You have two pumps conforming to ISO 2858 standard one from Europe (KSB) and the other from Australia (TKL). Both have the same designation - 100x80-315 and both run at 1500 rpm. You would expect both the pumps to have:

a) Same design capacity, head and impeller diameter
b) Identical foot-print and installation interface dimensions
c) Same materials of construction
d) None of the above

Q15 : American Petroleum Institute Standard API 610 (10th edition) is a process pump standard for petrochemical plants and refineries. A user will insist on pumps complying to this standard when which of the following is required?

a) Optimum pump efficiency is wanted
b) Lowest life cycle cost for the installation
c) Highest reliability in a critical application
d) Lowest environmental impact

Q16 : A double suction split-case pump is sometimes preferred over an end suction pump because of?

a) Smaller installation dimensions
b) Ease of maintenance
c) Absence of radial thrust load
d) All of the above

Q17 : There are two identical end suction pumps A and B of designation 200x150-500. Both A and B have identical impellers and shafts, the only difference between these two pumps being that A has a single volute casing while B uses a double volute casing. Which of the following statements is true?

a) B is likely to be more efficient than A at the best efficiency point (design point)
b) Shaft deflection at the stuffing box will be higher for B
c) A will have lower axial thrust load
d) B will have lower radial thrust load at part flow operation

Q18 : There are two axially split-case pumps with the following description:

Parameters	Pump model- 6x8-21	Pump model- 8x10-14
Rated capacity	450 m3/hr.	750 m3/hr.
Rated head	90 m	36 m
Impeller diameter	540 mm	360 mm
Impeller width at outlet (including shrouds)	40 mm	76 mm
Speed	1480 rpm	1480 rpm
Type of casing	Single volute	Single volute
Type of impeller	Double entry	Double entry

Which of the following statements is true?

a) Axial thrust of 8x10-14 is likely to be greater than that of 6x8-21
b) 6x8-21 is likely to be more efficient than 8x10-14
c) Radial thrust at 50% flow will be more in case of 6x8-21
d) None of the above

Q19 : Which of the following statement is not true for a two stage axially split-case pump with two back-to-back single-entry impellers?

a) Protect the shaft from abrasion and wear
b) Increase the stiffness of the rotating element (shaft to be more precise)
c) Reduce leakage losses through the stuffing box
d) None of the above

Q20 : Which of the following statement is not true for a two stage axially split-case pump with two back to back single-entry impellers?

a) Total head developed by the pump is the sum of heads developed by each stage.
b) The pump axial thrust is balanced because of two opposed single-entry impellers.
c) The pump radial thrust is balanced because the volutes of two stages are at 1800 to each other.
d) The total capacity of the pump is the sum of the flow through each stage.

Q21 : Which of the following statements is not true about packed gland pumps?

a) Packed gland pumps are preferred over mechanical seal fitted pumps in services such as fire protection where catastrophic failure of mechanical seals cannot be tolerated.
b) Compared to a mechanical seal fitted pump, mechanical efficiency of a packed gland pump is lower.
c) It's possible to reduce leakage to zero through a packed gland stuffing box.
d) Packed gland pumps generally have shaft sleeves to protect the shafts from abrasive wear at the stuffing box.

Q22 : Which of the following statements about pump shaft is not true?

a) Diameter of the pump shaft depends mainly on the power absorbed (kW), speed of the pump and the permissible shear stress for the shaft material selected.
b) Shaft stiffness factor (L3/D4) where L is the bearing span and D is the average shaft diameter is one of the measures of the shaft deflection.
c) Keyways, threads and sharp changes of section are stress raisers in a pump shaft.
d) A double volute pump needs shaft of larger diameter compared to a single volute pump.

Q23 : Which of the following statements about pump casings is not true?

a) Pump casing plays an important role in the generation of dynamic head, same as the pump impeller.
b) Thickness of the pump casing depends on the yield strength of the material used, permissible deflection, corrosion allowance required and the maximum test pressure.
c) Single volute casing is easier to cast compared to a double volute casing.
d) Casings are vulnerable to leakage, during pressure test, in areas where there are sharp changes of section.

Q24 : Euler's equation H_e = U₂V_U2 / ^g assumes infinite no of vanes and radial entry into impeller eye (V_u1 = 0). According to this equation, Euler's head depends on which of the following?

a) Impeller type, speed and outlet diameter.
b) Impeller outlet vane angle, speed and outlet diameter.
c) Impeller inlet and outlet diameter, speed and flow.
d) None of the above.

Q25 : For the pumping system shown in the figure below, calculate the total head and the power absorbed by the pump. Assume pump efficiency of 80%.

Power absorbed is given by:

BkW = (Q×H×S.G.) / (3.67×efficiency)

Q – Flow rate in m³/hr
H – Total Dynamic Head in meter water column (m)
S.G – Specific Gravity of the working fluid

a) 30 m and 46 kW
b) 32 m and 49 kW
c) 35 m and 53.6 kW
d) 30 m and 4.6 kW

Q26 : A centrifugal pump generates a pressure of 100 psi (a head of 231 ft = 100 psi x 2.31), while handling clean water of specific gravity 1.0. What pressures and head will this pump generate when pumping brine with sp. gr. 1.2 and kerosene with sp. gr. 0.8?

a) Brine (head = 192.5 ft, pressure = 100 psi) & kerosene (head = 288.7 ft, pressure = 100 psi)
b) Brine (head = 231 ft, pressure = 83.3 psi) & kerosene (head = 231 ft, pressure = 100 ps)
c) Brine (head = 231 ft, pressure = 120 psi) & kerosene (head = 231 ft, pressure = 80 psi)
d) Brine (head = 192.5 ft, pressure = 120 psi) & kerosene (head = 208.7 ft, pressure = 80 psi)

Q27 : The affinity laws of centrifugal pumps suggest that pump capacity varies directly with the impeller diameter, pump head as the square of the diameter and power as the cube of the diameter (assuming the efficiency is unchanged). The law holds good for impeller trims limited by the pump specific speed, impeller type and inlet diameter of the impeller. Assuming that the affinity laws hold good for the impeller trim shown below, what will be the capacity, head and efficiency for the current operating point?

a) Q = 450 m³/hr., H= 81 m, η = 82% and power = 121 kW
b) Q = 405 m³/hr., H= 72.9 m, η = 73.8% and power = 109 kW
c) Q = 450 m³/hr., H= 72.9 m, η = 82% and power = 109 kW
d) Q = 405 m³/hr., H= 81 m, η = 82% and power = 109 kW

Q28 : A pump manufacturer has to test an external firefighting pump for ship (FiFi pump) of the following specifications:

Capacity	2400 m³/hr.
Head	150 m
Efficiency	86%
Speed	1800 rpm
Medium	Sea water (sp. gr. = 1.03)
Driver	Main propulsion engine through power take-off and gear box

The manufacturer can test pump at his works, using one of the test motors at six pole speed (1000 rpm synchronous). What will be the rated duty condition of the pump at 1000 rpm at the test bed and what should be the rating of the test- motor. Test bed uses clean cold water (sp. gr. = 1.0) for testing.

a) Q = 1333 m³/hr., H = 83.3 m, motor = 400 kW, 6 pole
b) Q = 1333 m³/hr., H = 46.3 m, motor = 230 kW, 6 pole
c) Q = 740 m³/hr., H = 83.3 m, motor = 215 kW, 6 pole
d) Q = 740 m³/hr., H = 83.3 m, motor = 215 kW, 6 pole

Impeller- 5HS12	Impeller- 6HS17	Impeller- 6HS22	Impeller- 8HS26
Q = 1110 US gpm	Q = 1760 US gpm	Q = 2200 US gpm	Q = 3170 US gpm
H = 72 ft.	H = 180 ft.	H = 295 ft.	H = 460 ft.
N = 1450 rpm	N = 1480 rpm	N = 1480 rpm	N = 1480 rpm

Pump A	Pump B	Pump C	Pump D
Q = 2400 m³/hr.	Q = 1200 m³/hr.	Q = 600 m³/hr.	Q = 300 m³/hr.
H = 150 m	H = 140 m	H = 140 m	H = 140 m
N = 1800 rpm	N = 1800 rpm	N = 1800 rpm	N = 2100 rpm

Type of Losses	Labels
A) Entrance Shock losses	1
B) Mechanical losses	2
C) Leakage loses	3
D) Disk friction losses	4
E) Casing hydraulic losses	5

System	Options
Boiler Feed Pump	A)
Town Water Distribution	B)
Heat Exchanger	C)
Mine Dewatering	D)

Item No. & Description of curve	Level
1. H-Q curve of one pump
2. System characteristics corresponding to highest water level in suction sump
3. H-Q curve of two pumps running in parallel
4. System characteristics corresponding to lowest water level in suction sump
5. Run-out flow when only one pump operate with highest water level in the suction sump

Case A	Case B	Case C
Q = 1362 m³/hr	Q = 2043 m³/hr	Q = 2043 m³/hr
H = 68.6 m	H = 103 m	H = 68.6 m
Eff. = 85%	Eff. = 85%	Eff. = 85%
Power = 300kW	Power = 674.5kW	Power = 449.3kW
NPSHr = 7.5 m	NPSHr = 7.5 m	NPSHr = 3.3 m

Cost Heads	Cost Figures
1. Maintenance Cost	a. 10%
2. Operating Cost	b. 40%
3. Downtime Cost	c. 25%
4. Environmental Cost	d. 3%
5. Installation Cost	e. 10%
6. Pump Purchase Cost	f. 7%
7. Energy Cost	g. 5%

Location	Type of Losses
A) Impeller shroud faces	1) Impeller hydraulic losses
B) Suction volute	2) Mechanical losses
C) Impeller - wear ring gap	3) Leakage loses
D) Gland Packing	4) Disk friction losses
E) Vane passage	5) Casing hydraulic losses

Capacity	108 m³/hr
Head	500 m
Speed	2950 rpm
Temperature	900c
Specific gravity	0.956
Medium	De-mineralized water
Pump Efficiency	72 %

Pump A - 8x8-12	Pump B - 6x8-14	Pump C - 6x8-17	Pump D - 6x8-21
Q = 450 m³/hr	Q = 450 m³/hr	Q = 450 m³/hr	Q = 450 m³/hr
H = 22 m	H = 32 m	H = 55 m	H = 90 m
N = 1460 rpm	N = 1480 rpm	N = 1480 rpm	N = 1480 rpm

Pump A	900
Pump B	975
Pump C	1263
Pump D	1954

Pump A	975
Pump B	1954
Pump C	1263
Pump D	840

Pump A	1954
Pump B	1263
Pump C	975
Pump D	840

Pump A	1263
Pump B	1954
Pump C	975
Pump D	900

Type	Vertical shaft axially split-case
Capacity	2200 m³/hr
Head	35 m
Suction	3.0 m positive head on the suction side
Supply System	50 Hz

Pump A	Pump B	Pump C
Q = 2200 m³/hr	Q = 2200 m³/hr	Q = 2200 m³/hr
H = 35 m	H = 35 m	H = 35 m
N = 1480 rpm	N = 980 rpm	N = 740 rpm
Type - Axially split-case	Type - Axially split-case	Type - Axially split-case

Weekly Q/A List :

Q1 : Which of the following is not a primary function of the pump casing?

Q2 : A pump develops 100 m head while handling kerosene with specific gravity of 0.8. What head will the pump develop if the liquid handled is water:

Q4 : Which of the following statements about cavitation is not true?

Q5 : The following diagram shows pump performance curve superimposed on system characteristics. Can you identify the various terms in the table?

Q6 : For each of the following duties which is the most appropriate type of impeller:

Q7 : In a pumping system where the major component of the total head is friction, which of the following three methods of flow control is the most energy efficient? The flow through a pump can be controlled by:

Q8 : Which of the following properties are important for selecting the material of construction of an impeller:

Q9 : According to American Standard NFPA20 for fire pumps, pumps are generally provided with gland packing and mechanical seals are not used. What is the main reason for using gland packing in place of mechanical seals for these pumps?

Q10 : The following is a list of some of the Quality Assurance checks carried out by a pump manufacturer:

Q11 : Which of the following impeller types has the highest efficiency potential?

Q12 : The following are four End Suction ISO 2858 pumps. Pump efficiencies are

Q13 : Select the Pumps for the given duty points:

Q14 : You have two pumps conforming to ISO 2858 standard one from Europe (KSB) and the other from Australia (TKL). Both have the same designation - 100x80-315 and both run at 1500 rpm. You would expect both the pumps to have:

Q15 : American Petroleum Institute Standard API 610 (10th edition) is a process pump standard for petrochemical plants and refineries. A user will insist on pumps complying to this standard when which of the following is required?

Q16 : A double suction split-case pump is sometimes preferred over an end suction pump because of?

Q17 : There are two identical end suction pumps A and B of designation 200x150-500. Both A and B have identical impellers and shafts, the only difference between these two pumps being that A has a single volute casing while B uses a double volute casing. Which of the following statements is true?

Q18 : There are two axially split-case pumps with the following description:

Which of the following statements is true?

Q19 : Which of the following statement is not true for a two stage axially split-case pump with two back-to-back single-entry impellers?

Q20 : Which of the following statement is not true for a two stage axially split-case pump with two back to back single-entry impellers?

Q21 : Which of the following statements is not true about packed gland pumps?

Q22 : Which of the following statements about pump shaft is not true?

Q23 : Which of the following statements about pump casings is not true?

Q24 : Euler's equation He = U2VU2 / g assumes infinite no of vanes and radial entry into impeller eye (Vu1 = 0). According to this equation, Euler's head depends on which of the following?

Q25 : For the pumping system shown in the figure below, calculate the total head and the power absorbed by the pump. Assume pump efficiency of 80%.

Q26 : A centrifugal pump generates a pressure of 100 psi (a head of 231 ft = 100 psi x 2.31), while handling clean water of specific gravity 1.0. What pressures and head will this pump generate when pumping brine with sp. gr. 1.2 and kerosene with sp. gr. 0.8?

Q28 : A pump manufacturer has to test an external firefighting pump for ship (FiFi pump) of the following specifications:

Q29 : The specific speed of an impeller is expressed as (N√Q) / H^0.75 , where N = speed, Q = flow in USGPM and H = head/stage in ft. Following are four impellers for double suction split-case pumps with their rated duties. What are their specific speeds (US units)?

Q30 : Referring to Fraser-Sabini efficiency chart attached, what will be the efficiencies of the four pumps listed?

Q31 : Suction specific speed is an indicator of the suction capability of a pump. It is also a measure of suction energy of the pump & its permissible range of operation. External fire pumps for ships (FiFi pumps) operate at a single duty point and the typical duties are as follows:

Q32 : A ship-owner is considering installation of two diesel engine driven external fire pumps on the ship deck. Pump duty and suction conditions are as follows: -

Q33 : What is the NPSHa for the following system:

Q34 : The following figure shows various types of losses in a centrifugal pump. Please identify the labels with their positions & select the right option.

Q35 : Pump H-Q curve has been superimposed on the system curve in the figure below. Identify the head figures.

Q36 : The figure below represents curves for a pumping system. One would expect a system curve of this nature in the following systems.

Q37 : If the system head is over estimated or if multiple margins are added to arrive at the pump total head, the Pump performance will be sub-optimal. Which of the following statement is not true for such a system?

Q39 : The figure represents two identical pumps working in parallel in a water supply system. Water level in the suction sump varies between high & low limits. Please identify the labels in the diagram & put a tick mark against their right match:

Q40 : Air entrainment in the suction side of the pump can affect pump performance in diverse ways. Which of the following statements about air entrainment is not true for centrifugal pumps?

Q41 : The following is a mixed-up list of advantages of split case (SC) and end suction (ES) pumps. Each option contains some item nos. under the boxes. Please select the right option that correctly segregates the advantages for both the pump types :

Q43 : Following are the typical cost items in a life cycle cost (LCC) analysis of a pumping system. Approximate % costs are presented as a separate list. Please try to match the cost items with your best estimate of percentage figures :

Q44 : Losses in a centrifugal pump can be classified, for convenience of analysis, into the following categories :-

Q47 : Disk friction drag is a major component of pump losses in low specific speed pumps. The following are the duties of five split-case pumps - all pumps are single stage with double suction impellers. Pump D uses a double volute casing while all others have single volute casings :

Q24 : Euler's equation H_e = U₂V_U2 / ^g assumes infinite no of vanes and radial entry into impeller eye (V_u1 = 0). According to this equation, Euler's head depends on which of the following?