[Chemical Engineering Laboratory 2]: Experiment 5: Series And Parallel Pump

[Chemical Engineering Laboratory 2]

EXPERIMENT 5: SERIES AND PARALLEL PUMP

Candidate’s Name: GONG WEE JIE Student ID: SCM-023815 1.

Group Member’s Name: 1) Marie Rachel Chan Chee Mei 2) Sabrina Najwa bt Termizi

3) Steffi Untin Reginald Iggan 4) Shahrukh Ahmed 5) Mohammad Hussain

Lecturer/ Supervisor: Dr Yap Pow Seng Date of Submission: 25/02/2014

1.0 Objective

The main objective of this experiment is to show the basic operation and characteristic of centrifugal pump and to differentiate the flow rate and pressure head of a single pump and of two identical pumps that is running in series or parallel. The graphs of pressure different vs. flow rate for single, series and parallel pump operation is to be obtained from the experiment. The pump head and volumetric flow rate of single pump with series and parallel pump operation are compared from the results obtained from the experiment.

2.0 Introduction

Centrifugal pump converts mechanical energy from a motor to energy of a moving fluid and is one the commonly used pumps for transferring liquids. In this experiment, flow rates and pressure head of a single pump and two identical pump that are running in series and parallel are observed and recorded. Two pumps connected through a pipe work that allows them to be operated individually either in series or in parallel. When identical pumps are in series the pressure head is doubled but the flow rate remains constant. This is useful when high pressure is required but the same flow rate of a single pump is sufficient. On the other hand, when pumps are running in parallel the flow is increased and the pressure head generated is about the same as a single pump. There are two general classifications of pump: positive displacement and dynamic. Only Horizontal Single Stage Centrifugal pump ( P1) and (P2) in different arrangement-single, parallel and serial are operated in this experiment.

2.1 Horizontal Single Stage Centrifugal Pump

Centrifugal pumps have two major components: housing (also called casing) and impeller that consist of a number of curved blades that is connected to the rotating driveshaft. The prime mover rotates the driveshaft and it creates very low pressure in the centre opening hence the fluid in drawn into the centre opening( called the eye) of housing. The fluid is pushed radially along the impeller to the casing. As energy is added to the fluid by rotating blades, the pressure and the velocity increase until the fluid reaches the outer tip of the impeller. The fluid then enters the volute-shaped housing where the

increase in flow area causes the velocity to decrease. This is followed by decrease in kinetic energy and subsequently increase in pressure. The volute-shaped housing also provides a continuous increase in flow area in the direction of flow to produce a uniform velocity as the fluid moves around the outer portion of housing and discharge opening.

Although centrifugal pumps provide smooth, continuous flow, their flow rate output (also called discharge) is reducing as the external resistance is increase. In fact, by closing a system valve (thereby creating theoretically infinite external system resistance) even while the pump is running at design speed, it is possible to stop pump output flow completely. In such a case, no harm occurs to the pump unless this no-flow condition occurs over extended period with resulting excessive fluid temperature build up. Thus pressure relief valves are not needed. The tips of the impeller blade merely shear to through the liquid, and the rotational speed maintains a fluid pressure corresponding to the centrifugal force established. Figure 2 shows the cutaway of a centrifugal pump.

2.2 Pump Head versus Flow rate Curves for Centrifugal Pumps

Figure 3 shows pump head versus flow rate curves for a centrifugal pump. The solid curve shows the rate for water, whereas the dashed curve is for a more viscous fluid such as oil. From Figure 3, using a fluid having a higher viscosity than water results in a smaller flow rate at a fixed pump head.

Figure 3 Pump Head versus Flow rate Curves for Centrifugal Pump for water and for a more viscous liquid

The maximum head produced by a centrifugal pump is called pump shutoff head because an external system valve is closed and there is no flow. As the external system resistance decrease, the flow rate increases at the expense of reduced pump head.

2.2.2 Performance Characteristic Curves for Centrifugal Pumps

Figure 5 shows these three curves plotted on the same graph. As the flow rate increases from zero, the efficiency increases from zero until it reaches maximum, and then it decreases as the maximum flow rate is approached. The point where the maximum efficiency occurs is the best efficiency point (BEP), and the corresponding flow rate is the design flow rate. Maximum efficiency values for centrifugal pump typically range from 60% to 80%.

2.3 Centrifugal pump connected in Parallel

Connecting two pumps in parallel as shown in Figure 4 can provide higher flow rates. The effective two-pump performance curve is obtained by adding the flow rates of each pump at the same head. When two pumps are connected in parallel, the operating points shift from A to B, providing not only increased flow rate as required but also slightly greater head. Figure 6 shows identical pumps, but the pumps do not have to be the same.

Figure 4 Two centrifugal pumps connected in parallel

2.4 Centrifugal pump connected in series

Two pumps connected in series can provide higher head than a single pump , as shown in Figure 5. The effective two-pump performance curve is obtained by adding the head of each pump at the same flow rate. As, shown, the operating point shifts from A to B, thereby providing not only increased head as required but also greater flow. Figure 5 shows identical pumps, but the pumps do not have to be the same.

Figure 5 Two centrifugal pumps connected in series

3.0

Apparatus

Figure 6 Equipment Assembly

3.1Specifications

The unit consists of the followings: a) Pumps v 2 units of Horizontal Single Stage Centrifugal Pump (PI) and (P2) Flow rate : 2090 LPM Head : 20.7-15 m Max. Head: 22 m b) Circulation Tank Transparent acrylic water tank is provided to supply water to PI and P2. c) Flow rate and pump head All gauges and meters are provided in a way for easy viewing and data collection. d) Process piping The process piping is made of industrial PVC pipes. Valves used are non-ferrous to minimize rust and corrosion.

Overall Dimensions Height: 700 mm Width: 650 mm Depth: 1100 mm General Requirements Electrical: 240 VAC, 1-phase, 50Hz Water

:

Clean tap water.

Figure 7 Process Diagram for Serial / Parallel Pump Test Unit

3.2 Commissioning Procedures 1. Equipment is installed according to Section 3.1. 2. Check that all valves are initially closed. 3. The sump tank is filled with clean water until the water level is sufficient to cover the return flow pipe. 4. The pumps are tested according to Section 5.1. 5. Pumps, flow meter and the gauges are checked to ensure they are working properly. 6. pumps are turned off after the commissioning.

4.0 PROCEDURES

4.1 General Start-up Procedures Before the experiment is conducted, it is necessary to inspect to avoid any malfunction of the equipment. 1. The circulation tank is filled with water up to at least the end of the pipe output is submerged with water. 2. The V5 is in partial opened position. 3. The main power supply is switched on. 4. The appropriate pump is selected by referring to table 1 and the valve position is checked.

Table 1 Valve Position for General Start Pump Operation

Running Pump

Open Valve

Close Valve

Single

Pump 1, PI

1,4

2,3

Serial

Both Pump, PI &P2

1,3

2,4

Parallel

Both Pump, PI &P2

1,2,4

3

5. Turn on pump and slowly open V5 until maximum flow rate is achieved as shown in Table 2.

Table 2 Flow Rates of Pump Orientation

Minimum Flow Rate(LPM) Maximum Flow Rate(LPM)

Single

20

90

Series

20

90

Parallel

40

180

4.2 General Shut-down Procedures 1. Pump is turned off. 2. Valve V5 is in fully closed position. 3. Main power supply is switched off.

4.3 Experiment 1: Single Pump Operation Objective: Single pump operation with variable flow rate

Table 3 Equipment Set Up of Experiment 1 Fully Close valve

Fully Open Valve

Variable parameter

Pump ON

2&3

1& 4

Valve 5

Pump 1

Procedures: 1. The equipment is set up following the settings. 2. Valve V5 is slowly opened until the flow rate reaches 20 LPM. 3. Pressure reading on the pressure indicator is observed. Flow rate and pressure value is recorded when stable condition is achieved. 4. Observation is repeated by increasing the flow rate with increment by 10 LPM until the flow rate reaches 90 LPM. 4.4 Experiment 2: Series Pump Operation Objective: Series pump operation with variable flow rate

Table 4 Equipment Set Up of Experiment 2 Fully Close valve

Fully Open Valve

2,4

1,3

Variable parameter Valve 5

Pump ON Both Pump

Procedures: 1. The equipment is set up following the settings. 2. Valve V5 is slowly opened until the flow rate reaches 20 LPM. 3. Pressure reading on the pressure indicator is observed. Flow rate and pressure value is recorded when stable condition is achieved. 4. Observation is repeated by increasing the flow rate with increment by 10 LPM until the flow rate reaches 90 LPM.

4.5 Experiment 3: Parallel Pump Operation Objective: Parallel pump operation with variable flow rate

Table 5Equipment Set Up of Experiment 2 Fully Close valve 3

Fully Open Valve

Variable parameter

1,2 & 4

Valve 5

Pump ON Both Pump

Procedures: 1. The equipment is set up following the settings. 2. Valve V5 is slowly opened until the flow rate reaches 40 LPM. 3. Pressure reading on the pressure indicator is observed. Flow rate and pressure value is recorded when stable condition is achieved. 4. Observation is repeated by increasing the flow rate with an increment of 20 LPM until the flow rate reaches 180 LPM.

5.0

Results

Table 6 result of experiment 1 Rotameter (FL1)LPM

20 30 40 50 60 70 80 90 Rotameter (FL1)LPM

20 30 40 50 60 70 80 90

Digital pressure Gauge 1 (DPL 1) Bar

1.05 1.05 1.05 1.04 1.03 1.03 1.02 1.01


Digital pressure Gauge 1 (DPL 1)


Analog pressure Gauge 1 (APL 1)

Analog pressure Gauge 2 (APL 2)

kgf/cm2

kgf/cm2

kgf/cm2

kgf/cm2

3.08 3.02 2.97 2.91 2.82 2.74 2.65 2.55

1.07 1.07 1.07 1.06 1.05 1.05 1.04 1.03

3.14 3.08 3.03 2.97 2.88 2.79 2.70 2.60

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.1 2.1 2.0 2.0 1.8 1.8 1.7 1.6

Digital pressure difference (Gauge 2-gauge 1)

kgf/cm2

Analog pressure difference (Gauge 22 gauge 1) kgf/cm

2.07 2.01 1.96 1.91 1.83 1.74 1.66 1.57

2.10 2.10 2.00 2.00 1.80 1.80 1.70 1.60

pressure difference (kgf/cm^2)

Graph of pressure difference (gauge 2- gauge1) vs flowrate 2.5 2 1.5

Digital pressure difference ( gauge 4 - gauge 1)

1

Analog pressure difference (gauge 4- gauge 1)

0.5 0 0

20

40

60

80

Florate (LPM)

Graph experiment 1

100

Table 7 result of experiment 2 Rotameter (FM 1) LPM

20 30 40 50 60 70 80 90






Digital pressure Gauge4 (DPL4)

kgf/cm2

kgf/cm2

kgf/cm2 kgf/cm2 kgf/cm2 kgf/cm2

1.05 1.05 1.04 1.04 1.03 1.02 1.01 1.00

3.06 3.01 2.94 2.88 2.80 2.71 2.65 2.51

5.00 4.91 4.78 4.67 4.50 4.35 4.23 3.99

1.07 1.07 1.06 1.06 1.05 1.04 1.03 1.02

3.12 3.07 3.00 2.94 2.86 2.76 2.70 2.56

5.10 5.01 4.87 4.76 4.59 4.44 4.31 4.07

Rotameter (FM 1) LPM

20 30 40 50 60 70 80 90

Analog pressure gauge 1 (APL 1)



0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.10 2.10 2.00 1.90 1.90 1.80 1.70 1.55

4.20 4.18 4.00 3.90 3.80 3.60 3.40 3.20

Digital pressure difference (gauge 4-gauge 1)

Digital pressure Difference (gauge 3-gauge 1)

Analog pressure difference (gauge 4-gauge 1)

Analog pressure difference ( gauge 3-gauge 1)

kgf/cm2

kgf/cm2

kgf/cm2

kgf/cm2

4.03 3.94 3.81 3.70 3.54 3.40 3.28 3.05

2.05 2.00 1.94 1.88 1.81 1.72 1.67 1.54

4.20 4.18 4.00 3.90 3.80 3.60 3.40 3.20

2.10 2.10 2.00 1.90 1.90 1.80 1.70 1.55

Graph of pressure difference (gauge 4gauge 1) vs flowrate Pressure difference (kgf/cm^2)

4.5 4 3.5 3 Digital pressure difference ( gauge 4 gauge 1)

2.5 2

Analog pressure difference (gauge 4gauge 1)

1.5 1 0.5 0 0

20

40

60

80

100

Flowrate (LPM)

Experiment 2

Pressure difference (kgf/cm^2)

Graph of pressure difference (gauge 3-gauge 1) vs flowrate 2.5 2 Digital pressure difference ( gauge 3 gauge 1)

1.5 1


0.5 0 0

20

40

60

80

flowrate (LPM)

Experiment 2

100

Table 8 results of experiment 3 Rotameter (FM 1) LPM

40 60 80 100 120 140 160 180


Digital pressure Gauge2 (DPL 3) Bar




Digital pressure Gauge 4 (DPL4)

kgf/cm2

kgf/cm2

kgf/cm2 kgf/cm2 kgf/cm2 kgf/cm2

1.05 1.04 1.04 1.03 1.02 1.01 1.01 1.00

3.05 3.00 2.94 2.87 2.80 2.72 2.62 2.52

3.00 2.95 2.89 2.82 2.76 2.68 2.58 2.48

1.07 1.06 1.06 1.05 1.04 1.03 1.03 1.02

3.11 3.06 3.00 2.93 2.85 2.77 2.67 2.57

3.06 3.01 2.95 2.87 2.81 2.73 2.63 2.53

Rotameter (FM 1) LPM

40 60 80 100 120 140 160 180




0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2.18 2.15 2.00 1.90 1.85 1.80 1.75 1.60

2.18 2.15 2.10 2.00 1.85 1.80 1.70 1.60



Analog pressure difference (gauge 4-gauge 1)

Analog pressure difference, (gauge 2-gauge 1)

kgf/cm2

kgf/cm2

kgf/cm2

kgf/cm2

1.99 1.95 1.89 1.82 1.77 1.70 1.60 1.51

2.04 2.00 1.94 1.88 1.81 1.74 1.64 1.55

2.18 2.15 2.10 2.00 1.85 1.80 1.70 1.60

2.18 2.15 2.00 1.90 1.85 1.80 1.75 1.60

Pressure difference (kgf/cm^2)

Graph of pressure difference (gauge 4 -gauge 1) VS Flowrate 2.5 2 Digital pressure difference ( gauge 4 gauge 1)

1.5 1


0.5 0 0

50

100

150

200

Flowrate (LPM)

Experiment 3

Rressure difference (kgf/cm^2)

Graph of pressure difference (gauge 2gauge 1) vs flowrate 2.5 2 Digital pressure difference ( gauge 4 gauge 1)

1.5 1


0.5 0 0

50

100

150

200

Flowrate (LPM)

Experiment 3

5.1 Calculation

Sample calculation: Convert bar to 1 bar = 1.0197

For experiment 1,When LPM=20, digital pressure gauge 1 = 1.05Bar 1.05 Bar x 1.0197= 1.07 Digital pressure difference (gauge 2 –gauge 1) 3.14

- 1.07

2.07

[Chemical Engineering Laboratory 2]: Experiment 5: Series And Parallel Pump

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