2.9.2 Design of Filtered Water Outlet Pipe

Equation governing the flow through the Filtered water Pipe is as follows:

Q = cA (2gh)1/2

Where:

Flow through each Filter = Q (Cusecs)
= 2.91 Cusecs
X - Area of pipe = A (Sft)
Head loss or Differential Head = h (ft)
= 1.6 Ft
Acceleration due to gravity = g (Ft /s2)
Coefficient of Discharge = c (0.6)


X- Area of Pipe (A) = Q / c x (2gh)1/2

= 2.91 / 0.6 x (2 x 32.2 x 1.6) ½
= 0.48 Sft

Dia of Pipe = (A x 4 /3.14) ½
= 0.78 Ft
= 10 “

It is proposed to install 10 “ dia Filter Water Outlet Pipe fitted with a butterfly valve in Balancing Chamber of each filter bed to carry water from filter beds to the Filtered Water Collection Channel.

The operation of butterfly valve installed on the Filtered Water Outlet Pipe is controlled by the ultrasonic level gauge installed above the filter bed to measure the water level in the bed. As the water level rises due to clogging of filter bed, ultrasonic level gauge sends message to the controller for opening butterfly valve installed on the Filtered Water Outlet Pipe for opening valve proportionate to the rise in water level. This operation maintains a constant water level on the filter bed. It is this very reason this type of filtration is called Constant Rate Filtration. The automatic operation of the level gauge and butterfly valve takes place through electric actuation and the three components together are called Rate Controller.