Equivalent Length

[easaw]

How can we transform the computed equivalent length, which is a minor losses to get the total sewer line flow rate?

 

[bimr]

The computed equivalent length X the headloss per foot plus the minor head losses and the elevation difference gives you the total headloss of the pumping system.

If you have all of the above information, you can work backwards to come up the the headloss per foot. The Camerons Handbook will give you the flow rate if you know the headloss per foot and the pipe description.

 

[dicksewerrat]

Where can I find this book?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bimr]

The use of the terms "equivalent length" and "minor losses" indicates that the poster's project makes use of a force main. Of course most people do not call a force main a "sewer line" either.

http://www.amazon.com/Cameron-Hydraulic-Data-Reference-Hydraulics/dp/9990620393

 

[jartgo]

bimr, I think you took me in a circle with your suggestion. Although, I'm not sure the original poster asked a question that could be answered with the information given.

Equivalent length allows you to calculate total headloss from approximations, as bimr meant to describe, not flow rate. The headloss and flowrate are then indirectly proportional (and dependent on one another).

In general, equivalent lengths allow you to lump minor losses all into a length term. That is, say you have a 1000 foot pipeline with various bends, valves, tees, etc. These appurtenances introduce losses that aren't easily characterized. So, various texts will suggest equivalent lengths for the various appurtenances based on their size and configuration. For example, an elbow might be assigned a value of 6 feet...again, the values are published in various texts. These values would be summed and that total additional length added to the real pipeline length. So, this theoretical "length" would then be used directly in the conventional equations for headloss. In doing so, you would also need to know at what flow rate you are evaluating the loss. In generating a system curve you would do this over your range of interested flows.

 

[bimr]

Not sure exactly what the poster is asking. But I guess what I was thinking is that the poster would like to be able to approximate the flow from a pump knowing all of the piping information, but not having the pump information available.

Working backwards with the piping information, it is possible to estimate the pump flow.

 

[bimr]

Here is an example:

At what flow rate is the pump operating?

I know the following:

1. Total pumping head = 200 ft. water pressure

2. Elevation head = 100 ft. water pressure

3. Equivalent Length of piping = 200 feet


The headloss through the piping than is the difference = 100 ft water pressure (200-100)

Equivalent piping length = 200 linear feet

Head loss through the piping = 100 ft water pressure/ 200 linear feet (Common unit being ft-headloss/100 feet pipe)

Knowing the pipe diameter and material as well as the headloss through the piping, you can estimate the flow rate using the tables in the Camerons Handbook.

 

[jartgo]

gotcha. reading your first post as written looked as if you were using headloss per foot to calculate headloss per foot.