definition 1

[TimJim]

What is the difference in definitions between an "invert elevation (IE) and "flowline elevation" (F/L)?

 

[RWF7437]

As far as I know, they are synonymous. Some might prefer "flow line" for natural streams or ditches while using invert for a pipe or manmade channel.

good luck

 

[PELS]

OK, I'll take a shot.

"Invert" by definition means to "turn upside down". It is normally used with reference to a structure such as a drain inlet or manhole. "Invert Elevation" then, refers to the bottom side of the structure, or the bottom elevation.

"Flowline" is a term to describe the point in a pipeline or other conveyance facility (channel) where fluid will flow towards because it is the lowest elevation in the conveyance structure (as opposed to the top or the sides). Therefore, if a fluid is introduced to the structure, it will initially form a line along the lowest point(s) in the structure as gravity and slope influences its direction and velocity.

 

[msquared48]

PELS:

Your descriptions flowed quite well.

Mike McCann
McCann Engineering

 

[dicksewerrat]

I thought the flow line was the elevation of the water surface as the water moved down the pipe.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bimr]

A flowline is a line through the center of a channel reach or a water body, which defines the main direction of flow.

Invert refers to the flowline of the culvert (inside bottom).

 

[gbam]

OK -- An invert is the lowest point of a conveyance. This can be a channel or pipe. A flow line is similar. When used together to define a culvert, the flowline is the top of dirt and the invert is the bottom of culvert.

 

[RWF7437]

OK, I can't stand it any more so here are some suggestions.

gbam wrote:
"OK -- An invert is the lowest point of a conveyance. This can be a channel or pipe."

This is, I believe, what most engineers understand by the word invert . The definition offered by PELS is correct if you are using invert as a verb.

gbam also wrote:

"A flow line is similar. When used together to define a culvert, the flowline is the top of dirt and the invert is the bottom of culvert."

This simply confuses the issue, I believe. The word flowline is never, in my experience, used to refer to the dirt over the top of a culvert or any other conveyance structure.

dicksewerat wrote:

"I thought the flow line was the elevation of the water surface as the water moved down the pipe. "

This is also confusing. I have never heard the word flowline used this way. In a pipe or culvert with a free water surface the highest elevation to which the water may rise may be called any of the following: " water surface elevation" sometimes the "hydraulic grade line" or just "water surface".

Flowline may be used to refer to the low point in a pipe, culvert, ditch, stream or other structure that conveys water, WHEN VIEWED IN PROFILE. That term may sometimes be used to refer to the thread of a stream WHEN VIEWED IN PLAN. This use is synonymous to the German word "thalweg".

When words are our only tools it seems important to agree on their meaning. Fortunately, engineers have other tools, such as pictures, drawings and numbers and symbols.

 

[gbam]

RWF7437 --

It is standard in my area to refer to a flowline as the elevation of sand and/dirt resulting in siltation and covering of an invert. This, I thought, was standard practice. Apparently it is not. However, I did not state it was the top, or crown(Outside Top), of a culvert.


|=======================|<<SOFFIT(Inside Top)
| |
| |V Flowline
___________|_______________________|V_________________
| |
|=======================|<<INVERT(Inside Bottom)

Hopefully this clears up my previous post.

 

[cvg]

gbam - what country / area are you located in?

I basically agree with the definitions as clarified by RWF7437, they are the same in my area (southwestern U.S.)

 

[RWF7437]

gbam,

thanks for the clarification. I understand what you mean now but I would doubt that this is a universal "standard practice".

I have worked in Oregon, Washington and California mostly for the last 47 years and had not run across your practice in those areas.

 

[gbam]

cvg
I am also in the SW U.S. I have seen these definitions for 14+ years. Maybe its a local thing? no biggy

 

[BRIS]

After 30 years in the industry working in all continents I have never before come across the term "flow line" – my conclusion is therefore whatever it means you can manage without it.