blow-off valve sizing1
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8/13/2019 Blow-Off Valve Sizing1
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Design Rationale:1.) Blow-off assembly is used to flush out accumulated sediments at low spots and dead-ends of
pipelines and for draining pipelines for repairs, maintenance, and inspection.2.)
Design Data:Cd = unitless Coefficient of DischargeDT = - hr Recommended Discharge TimeVD = - m/s Recommended Discharge Velocity
(AWWA M51 Chapter 4)L = m Length PipeD = m Diameter of Pipe
Elev. 1 = m Low Level Point of the WaterlineElev. 2 = m High Level Point of the Waterline
H = m Pressure Head at the Outlet(Assumed to be Half of the Dif ference in Pipe Elevation)
g = m/s Acceleration due to Gravity
Solving for the Volume to be DrainedV = A x LV = xV = m³ Volume of Water to be Drained
Solving for Diameter of the Blow Off DT = hrs or secs Assumed Discharge Time
V
DT
Q = m³/s Discharge Rate
Solving for the Area of Blow Off using Torricelli's Theorem
Q = Cd x A x (2g x H) ½
Cd x (2g x H) ½
A = m²
Solving for the Diameter of Blow Off π x d ²
4 x A ½
d = m use d = mm
0.62 4
0.03
8.3
9.81
A =4
d =π
45.91
0.3 0.6
10151.8
2.54 10152583
3 10800
Q =
0.24
A =Q
29.31
0.2 200
8/13/2019 Blow-Off Valve Sizing1
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PROJECT :DESCRIPTION :DATE :DESIGNED BY : CHECKED BY :
EngineeringDevelopment Corp. ofthe Philippines
8/13/2019 Blow-Off Valve Sizing1
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PROJECT :DESCRIPTION :DATE :DESIGNED BY : CHECKED BY :
EngineeringDevelopment Corp. ofthe Philippines
8/13/2019 Blow-Off Valve Sizing1
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PROJECT :DESCRIPTION :DATE :DESIGNED BY : CHECKED BY :
EngineeringDevelopment Corp. ofthe Philippines
8/13/2019 Blow-Off Valve Sizing1
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PROJECT :DESCRIPTION :DATE :DESIGNED BY : CHECKED BY :
EngineeringDevelopment Corp. ofthe Philippines
8/13/2019 Blow-Off Valve Sizing1
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PROJECT :DESCRIPTION :DATE :DESIGNED BY : CHECKED BY :
EngineeringDevelopment Corp. ofthe Philippines
8/13/2019 Blow-Off Valve Sizing1
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PROJECT :DESCRIPTION :DATE :DESIGNED BY : CHECKED BY :
EngineeringDevelopment Corp. ofthe Philippines
8/13/2019 Blow-Off Valve Sizing1
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PROJECT :DESCRIPTION :DATE :DESIGNED BY : CHECKED BY :
EngineeringDevelopment Corp. ofthe Philippines
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