Methodology
55
β =0,4
δ = 0,5
S =
0,31
1
= 0,31 m
2
6.5.1.2.3. Calculating load losses
According to KIRSCHMER, load losses at the screen are depending on the spacing between
the bars, the width of the bars, the shape of the bars, the approach speed and the inclination of
the screen. They are calculated using the following formula:
Δh =
í µí¼·× í µí²ƒ 𝟒/𝟑
𝒆 𝟒/𝟑
×
𝑽
𝟐 𝒈
×sin α
Where :
Δh: Load loss in meter of water (m).
β : Coefficient of the bars shape (β= 1.79 for circular-section bars).
b : Grid bar thickness (m).
e : Spacing between bars (m).
V: Approach velocity or water velocity in front of the screen(m/s).
g: Gravity acceleration (g= 9.81 m/s).
α: Angle of inclination of the screen with the horizontal (α=60°).
 Calculating load losses for the coarse screen (𝚫𝐡 𝒂 )
The choice of the shape of the screen bars is based on the shape that generates less load
losses. In this case, I opted for the circular shape.
With :
β = 1,79
α =60°
e = 50mm
g = 9,81m/s
b = 20mm
v = 1m/s
 Calculating load losses for the fine screen ( 𝚫𝐡 𝒃 )
we have :
β = 1,79
α =60°
e = 15mm
g = 9,81m/s
b = 10mm
v = 1m/s.