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Intake Design: Data

The document provides design details for an intake structure including: - A design discharge of 8.68 m3/s with no desilting chamber or silt flushing capabilities. - Rectangular conduit dimensions of 1.4m depth and 1.55m breadth to accommodate the design discharge velocity of 4 m/s. - An elliptical bellmouth opening with a total width of 2.6m and height of 2.69m to smoothly transition flow into the conduit. - A trash rack above the intake with 3m wide panels, 10 degree inclination, and vertical bars spaced 100mm apart to screen debris while maintaining design velocities under partial clogging conditions.

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304 views4 pages

Intake Design: Data

The document provides design details for an intake structure including: - A design discharge of 8.68 m3/s with no desilting chamber or silt flushing capabilities. - Rectangular conduit dimensions of 1.4m depth and 1.55m breadth to accommodate the design discharge velocity of 4 m/s. - An elliptical bellmouth opening with a total width of 2.6m and height of 2.69m to smoothly transition flow into the conduit. - A trash rack above the intake with 3m wide panels, 10 degree inclination, and vertical bars spaced 100mm apart to screen debris while maintaining design velocities under partial clogging conditions.

Uploaded by

Gokul
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as XLSX, PDF, TXT or read online on Scribd
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INTAKE DESIGN

IS 9761:1995

DATA:
Design discharge 8.68 m3/s
Provision of desilting chamber after intake NO
Over load power generation 0%
Discharge for silt flushing 0%
Discharge with overload 8.68 m3/s
Angle of inclination of conduit 00
Full reservoir level(FRL) 1941.00 m
Minimum drawdown level(MDDL) 1937.50 m
Base level at Trench weir 1934.00 m
Nature of opening FLATBOTTOM

CALCULATION
1.Conduit design
Velocity of flow in intake(Assumed) 4 m/s
Area of conduit 2.17 m2
Shape of conduit RECTANGULAR
Depth (assume) 1.4 m
Breadth b 1.55 m
Head 7.775 m
H/d Ratio 5.55
Head type LOW
Type of flow Pressurised flow

2.Opening and transition


Area of the conduit 2.17 m2
Velocity through the conduit 4.00 m/s
Co-efficient of contraction 0.7
Opening Area 3.10 m2
Height of opening
h1 1.99 m
h2 0.70 m
Total Height of opening h 2.69 m
Width of opening be 2m

Width of the bellmouth along the section a1 1.54 m


Height of the bellmouth along the section b1 0.41 m
Length of the bellmouth along the plan a2 0.77 m
Width of the bellmouth along the plan b2 0.30 m
Froude's number 1.08
Submergance depth 3.72 m
Centre line of intake 1934.00 m
Conduit invert level 1933.30 m

RESULT
1 Ellipse equation
At section X2 2 Y2 2`
+ =1
1.54 0.41

At plan X2 2 Y2 2`
+ =1
0.77 0.30

2 Conduit invert level 1933.30 m


3 Submergance depth 3.72 m
4 Total width of opening 2.60 m
5 Total height of opening 2.69 m

AIR VENT PIPE


Discharge (b/w 21% to 22%) Q 1.91 m3/s
Factor of safety S 4
Thicknessof conduit(assume) t 0.1 m
Intake valves ORDINARY
Co-efficient of discharge c 0.5
Area of vint pipe F 533.50 mm2
Diameter of air vent pipe 26.06 mm
Data:
Design Discharge,Q 8.68 m3/s
Provision of desilting chamber after intake NO
No. of Trashrack 1 no
Discharge througheach trash rack with overload 9.55 m3/s
Minimum Draw Down Level 1937.50 m
Centre line of intake 1934.00 m
Sill level of trash rack 1933.00 m
No. of Trash rack bay 1 no
Clear width (assumed) of each panel 3m

Calculations:
Total width(clear) ofpanel of trash rack 3m
Thickness of end pier 1m
Top of intake 1942.5 m
Top level of bell mouth opening 1932.01 m
Sill level of trash rack provided 1933.00 m
Height of trash rack arrangrement from top 9.50 m
C/C (vertical ) spacing of horizontal beams 2m
Depth of beam 0.3 m
Height of trash rack arrangrement from MDDL 4.50 m
No. of Beams below MDDL 2 nos
Angle of trashrack 10 deg
Actual length of trash rack 4.57 m
Net height of trash rack without beam 3.97 m

Trash rack bars


Area of Trash Rack arrangement 13.71 m2
Thickness of vertical steel bars 10 mm
Spacing between bars 100 mm
Clear spacing of vertical bars 90 mm
Thickness of horizontal Girders 40 mm
C/C spacing of horizontal Girders 700 mm
Clear spacing if horizontal Girders 660 mm
Considering one square meter panel of trash rack 1m
Gross area 1 m2
No. of bars required
Vertical 11
Horizontal 2
Total area of bars 0.19 m2
Net area of trash Rack for 1mX1m 0.81 m2
Total net Area of whole trash rack 11.10 m2

Velocity for Different clogging condition:


a) Considering 50% clogging
Area For 50% clogging 5.55 m2
Velocity based on clogging, v 1.719789 m3/s

b) Considering 25% clogging


Area For 25% clogging 2.78 m2
Velocity based on clogging, v 3.439577 m3/s

c) Considering no clogging
Area For no clogging 11.10 m2
Velocity based on clogging, v 0.859894 m3/s

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