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SERIES PIPELINE SYSTEMS Now we bring together all the losses we have studied to investigate the total loss for a pipe network Series pipeline fluid flows in a single flowpath through the system What were the various losses we discussed???

- Friction loss in pipes (major)

hL = f * (L/D) * v2/2g

- losses due to bends, fittings, valves, etc (minor losses)

)2/( 2 gvKhL = We will be studying 3 types of series pipe systems CLASS I:

Given pipe size, flow rates Determine pressure at some point, total head from a

pump

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CLASS II:

Given pipe sizes, valves, fittings etc. Given allowable pressures or pressure drops Determine the allowable flow rate Q in the system

CLASS III:

Given pipe layout and flow rates Determine pipe sizes

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CLASS I Computations Apply General Energy Equation

hL = sum of

- entrance loss - friction loss in suction line - loss in valve - loss in elbows - friction loss in discharge line - exit loss

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Example Problem 11.1

Determine Power supplied to pump If

Efficiency = 76% Fluid = methyl alcohol at 25C Q = 54 m3/hr Suction line 4 steel pipe 15 m long Discharge line 2 steel pipe 200 m long Valve globe valve Entrance from 1 square edged inlet

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NOTE see appendices F-G in TEXT for areas and inside diameters for steel pipes.

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Correction 789! (table appendix B)

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Table 10.5

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Table 10.4

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ASSIGNMENT # 7: CLASS 1 PIPE SYSTEMS

11.1M 11.2M

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***Some Design Considerations for Series Pipelines:

Keep pressure at inlet to the pump as high as practical but checks should be made to ensure that cavitation does not occur in the suction line.

Minimize energy losses in the pipelines. Large diameter

pipes should be selected for long pipe line lengths so as to reduce friction losses. However the pipe dia should not be excessively large increases costs.

Length of suction lines should be as short as practical.

ON or OFF valves should be preferred, such as GATE or

BUTTERFLY valves. Where flow needs to be gradually reduced, GLOBE valves should be used.

Often preferable to put valves on either side of the pump.

Design Changes to CLASS I Problem to reduce losses:

Length of suction line = 15m, appear excessively long, shorten if possible.

Provide a GATE valve in the suction line

Energy loss in 200m discharge line too high = 185.9 m

(friction); associated with high velocity = 6.92 m/s.

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Recommended range of velocities Suction lines = 0.6 to 1.2 m/s Discharge lines = 2-5.5 m/s To reduce the velocity in the discharge line increase the diameter of the pipe. Currently you have 2 inch pipe. Refer to Figure 6.2 (next page) says to use ~ 21/2 inches; Adopt 3-inch Velocity head due to 2-inch = 2.44 m Velocity head due to 3-inch = 0.504 m

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A reduction in energy losses of about 5 times!!

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Currently you have Globe valve in discharge line which has an equivalent-length ratio = 340. The same value for a fully-open GATE valve is = 8. A reduction of about 42 times in the energy loss.

Final Summary of proposed design changes

Decrease suction line length from 15 to 1.5 m. Add that length to discharge line.

Add fully open gate valve in suction line.

Increase discharge line dia from 2 to 3.

Replace globe valve in discharge line with gate valve.

All these changes will lead to reduction in energy added by pump from 217 m to 37.9 m. the power supplied to the pump would decrease from 33.2 kW to 5.8 kW a reduction by a factor of 6!!! Cost analysis should also be done. CLASS II:

Given pipe sizes, valves, fittings etc.

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Given allowable pressures or pressure drops Determine the allowable flow rate Q in the system

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274.5)/(7.3

1log 9.0

25.0

+

=RND

f

- (Swamee & Jain eqn)

Note Correction D/ = 8889 in eq above!

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CLASS III: Given pipe layout and flow rates Determine pipe sizes

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