I have a 8" gravity feed line curre

[mechanicalbro]

I have a 8" gravity feed line sized to handle 1359gpm flow (% solids is 15% and sg 1.13). Total length of this line is almost 100ft. I calculated the total head in the line to be 32'. I would like to increase the flow in the line by installing a vent pipe in the line as i believe there are some air issues in the line. This Vent pipe height should be > 32’ (head) such that it is tall enough that head in the pipe at that location doesn’t let the solution flow out of the vent. However, I would need help in sizing the vent pipe diameter. Also, help me determine if I require to install any relief valve ? Can someone please help me on this ?

 

[bimr]

What is the difference in elevation from beginning to the end?

 

[mechanicalbro]

the elevation difference is 11'

 

[katmar]

You need to provide a sketch showing the actual slopes, high points, low points etc. The detailed geometry is much more important than the overall elevation difference. For example, it is hard to envisage a head of 32' in a gravity fed line with an overall elevation difference of 11' unless there is an extreme low point. If you provide a good sketch you will get much better advice.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[mechanicalbro]

The way I calculated head is
Head = density x g x height = 0.15 * 9.81 * 11 = 16.18’ (sorry i mentioned 32' previously)
i considered density as 0.15 because %solids are 15% (is it right ?)

i have uploaded picture of the 8" pipeline i was referring to

 

[LittleInch]

OK.

Your line if able to do 1360 gpm is flowing at about 3 m/sec / 10 ftps. That's fast for a slurry line.

Your equation is wrong. That's the way you calculate pressure.

Your data is all over the place.

You need to draw this out so we can understand what's going on.

I don't think a vent pipe is going to help you.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

Carrying liquid is?
Slurry is?
Percent air in the flow?
You must have an accurate elevation profile to design gravity pipelines.

 

[katmar]

i have uploaded picture of the 8" pipeline i was referring to

https://files.engineering.com/getfile.aspx?folder=beafaf06-da76-411a-961b-6

That doesn't look like an 11' drop


Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[1503-44]

Nor 100 ft

 

[mechanicalbro]

Thanks for all the replies, appreciate it. And thanks for being more patient in responding to my half baked question. I just got started so i am still learning. The picture does not show complete pipeline but shows major part of the 8" line, however the elevation difference from beginning to end point is 11' only. I was asked to hydroblast this line and install breather/vent pipe to address any air flow issues (if there are any) and check if that increases flow in the line. So I would like to know what would be the ideal diameter and length of the vent pipe would be. Slurry details are % solids is 15% and sg 1.13.

 

[LittleInch]

Which idiot is asking you to do this?

At the flow rate you quote the will be no air issues as its going too fast.

Why anyone thinks adding a vent line will increase flow is beyond me.

First you need to draw up this in section and add information such as depth of liquid at the inlet and what happens at the outlet. Fluid drops into tank?

What is the flow now?
What do you want it to be?
Why did anyone think there are air issues?
Can you get a photo of the slurry exiting out the end of your pipe?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[katmar]

It is very doubtful that you would achieve a flow rate of 1359 gpm if the only driving force is the 11' drop in elevation. Is there some head in the supply tank?

I agree with LittleInch that the velocity is high enough to flush any air out of the system and installing vents will not help. Nothing to argue with 1503-44 about here.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[1503-44]

What happened to the 32ft elevation?

 

[pierreick]

Hi,
To get a meaningful answer, supply the current isometric or elevation of the line from the start until the end of the line, including tanks downstream and upstream .
Your picture is useless to resolve this type of problem ,let you work as an engineer with a sketch.
I don't believe the current situation based on data supplied , too little pressure gradient or head to overcome the head loss for such big flowrate .
BTW, why do you multiply the specific gravity by 15% ?????
Definitely you need to provide more information, starting with an accurate sketch and existing process condition.

https://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-73862001000300007

Good luck
Pierre

 

[katmar]

What happened to the 32ft elevation?

(OP)[/b]]The way I calculated head is
Head = density x g x height = 0.15 * 9.81 * 11 = 16.18’ (sorry i mentioned 32' previously)

 

[1503-44]

Oh. OK. I guess a wrong number in an incorrect calculation matters little in the grand scheme of things.

 

[Nutzman]

With a gravity fed line, you dont want to allow more than 81% "full flow". Fuller than that and the line "gurgles", causing velocity changes and possible settling

 

[LittleInch]

It depends. You can have gravity lines full, but sure , if you have a transition between partially full and full then you can end up with gurgling and instability.

all depends on the slope, length, viscosity etc.

hydro power penstock lines are gravity fed and they are full...



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Nutzman]

Littleinch,

Look behind the curtain and give me a shout. Need to discuss something.