Inlet works- Determining water level through a channel 2

[MatSA92]

Hi all,

Some guidance please. Refer to the attached pdf of a preliminary inlet structure into a pump station sump.

My question is how does one go about calculating the water levels in the inlet channel?

To clarify:
1. Only one channel will be open at a time, thus the PWWF volume of 130l/s will be the design volume.
2. The pipeline to sump ends in an open air drop into the sump.

I am struggling with finding a control within the channel from which I can establish a known water level in which to work from.

Hope the question posed is clear enough. Let me know if you need any clarification on anything.

 

[MFJewell]

I assume the pump station intake is gravity fed from a body of water? If so, the normal level will be whatever the source level is (assuming low dP across the sand trap and fairly clean screens). On pump stations I was around, inlets we fed from the Mississippi river and Susquehanna river could vary by 30+ feet.

If your feed is from a canal and the canal is undersized, I suppose you could end up with a slightly lower level in the intake versus the canal feed.

 

[ashtree]

I assume you are trying to ascertain the working level for your comminutor.

There are several components that are going to provide some control of the level. You have mentioned using 130l/sec as the design flow. Therefore the level in the head works will be determmined by the head loss caused by:
1) The outlet pipe
2) The comminutor- this will depend on the machine and the stage in its cycle of operation. The manufacturer will probably offer some generic headloss graphs.
3) The coarse bar screen- dependent on the degree of fouling.

There will obviously some head generated by the flow through the various channels and grit sump etc but the above items will most likely contribute most to level control in the headworks.

I would suggest that you work backwards from the outlet and plot the headloss through the channel using best and likely worst cases for the two screens.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[bimr]

Use Manning's equation for open channel flow:

http://www.nesc.wvu.edu/pdf/dw/publications/ontap/2010_tb/hydraulics_pressure_DWFSOM150.pdf

 

[cvg]

start at the downstream end and determine your control points. Any one of those may limit or "control" your flow. you will need to evaluate each one for flow capacity and headloss to determine which is controlling. you can use mannings for the open channel parts, weir and orifice flow equations for others and you will need flow/headloss data for your channel "muffin" monster

a) pipeline at sump, this is probably flowing at critical depth
1) pipe outlet which will act as an orifice
2) grinder pump which has a limiting capacity and head loss
3) screen (clogged or not clogged)
4) sluice gate (full or partial open)
5) inlet pipe at the splitter


the head at the inlet pipe splitter will need to account for all the head losses that will occur downstream in a through 5

note that head is not "generated" unless you are pumping.