Methodology
57
The basin will be equipped with a scraper bridge from which a sand extraction pump will be
suspended. Oils will be scraped into a pit by the surface scrapers. We opt for a circular sand
and oil removal.
6.5.1.3.1.Sizing the dessander and oil remover
 Calculation of the dessander and oil remover surface area
A velocity of 49 m/h is assumed.The surface area is calculated using the
following formula:
S=
𝑸 𝑹𝒘𝒑
𝑽𝒂𝒔𝒄
With :
𝑸 𝑹𝒘𝒑 : Rainy weather peak flow.
𝑽 𝒂𝒔𝒄 : Ascendant velocity.
 Calculation of the dessander’s radius
The radius is calculated using the following formula:
S= π×r
2
Therefor :
r =√
𝑺
𝝅
Where :
r : The dessander radius (m).
S : The surface of the dessander (m
2 ).
 Calculation of the dessander’s volume
The volume of the dssander is calculated using the following formula:
V= S× H
With :
V : Volume of the dessander (m
3 ).
S : horizontal surface (m
2 ).
H : Height of the dessander (we assume that : H=4 m).
 Calculation of dwell time
Dwell time is calculated using the following formula:
𝒕 𝒔 =
𝑽
𝑸 𝑹𝒘𝒑
With :
𝒕 𝒅 : Dwell time (min).