Maximum flowrate the pipeline can handle

[mechanicalbro]

Hi Everyone,
I have a HDPE pipeline carrying slurry which has % solids of 20-25% and specific gravity 1.13. The pipeline starts off as a 12" line, then reduces to 8" for majority of path and finally before discharging into a thickener it becomes 12" again. The elevation difference between first point and final point of discharge is 10' 11". I have attached a rough sketch showing the route and pipeline details (size and lengths). Could you help me determine the maximum flow this line can handle in the form of calculations ? Please let me know if you need additional information to calculate the flow ? Appreciate all the help.

 

[LittleInch]

Any idea what the viscosity is?

The vast majority of the pressure drop will be in the 8 inch.

What's the liquid level in that first tank? What's s distributor box?

Is that the plan view??

Can you sketch the vertical profile? Or give elevation at the start and end point of the 8 inch.

At 10ft total Head loss over 150 ft, I'm not anticipated more than 1m/sec velocity.

What calculations have you tried?[pre][/pre]

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

 

[mechanicalbro]

Hi,
Currently no idea about viscosity, for now could you consider some value, say

The distributor is just a normal one, the total length of that box is 10' and it is half filled

The elevation at the start and end point of the 8 inch is 3732'-1" and 3721' - 1"

Does this help to do flowrate calculations ? I am needing to determine if this line is capable of handling 1750 gpm of flow ? If not what size line should I upgrade this line to ? Please help. This is a hdpe pipe

 

[mechanicalbro]

This line shows 12" coming from bottom of that distributor box

 

[mechanicalbro]

this pictures shows 12" line reducing to 8"

 

[mechanicalbro]

this picture shows path of 8" (ignore vent line thing)

 

[mechanicalbro]

this shows 8" converting to 12" before discharging

 

[MJCronin]

I am confused by your word selection ..."bro"....

You describe a situation where there will be gravity induced flow of a thick slurry through a piping system.

But you ask "Could you help me determine the maximum flow this line can handle..".... then you talk of 1750 gpm flowrate

To me, this word usage implies that you are somehow in control of the flowrate (like if you were going to add a pump)

To get 1750 gpm through an 8 inch NPS pipe, you will have about 11.2 fps velocity...... far higher than will be developed by gravity.

I think that your gravity induced slurry system will only develop 2 to 3 fps velocity ..... maximum of around 300 - 450 gpm

MJCronin
Sr. Process Engineer

 

[mechanicalbro]

sorry if i am confusing with word selection.
Basically, what I am trying to determine is whether the current configuration is capable of handling 1750gpm or not. If not, what should be the size of upgraded line to handle 1750gpm.

 

[LittleInch]

mechanical,

There's no such thing as a typical value for slurry viscosity or physical properties and at 20-25% solids I can only imagine this stuff (what is it?) is pretty viscous / sticky.
Particle size and density also has lots to do with it, not just % solids. Transporting large rocks is a lot different to a powder solution.
Is it a Newtonian or non Newtonian substance??

Does it settle out if left or need a certain minimum speed?
Without this information you could be out by a factor of 5 or 10 in any calculation, good or bad. Or the line could simply block up and stop because you can't generate sufficient velocity to keep it all in suspension.

So you really need to get as much information as you can on this slurry before you can start to do any calculations that would hold up in practice. Even then slurry is notorious for not behaving as predicted so a decent margin is normally a good idea above any minimum velocities and also fit a flushing system for when the line stops or it may never start again....

But this seems to be a current existing set-up - what's changed? How much did you get through before?

PE is pretty good with slurries as it doesn't really erode, has a low friction value and so long as they made the internal bore smooth when they made it works quite well.

But with only 10 feet head driving it I struggle to see it working well and not at your desired flow rate.

But bottom line you only have about 10% of the required information. or you're only telling us 10% of what you know.



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

 

[pierreick]

Hi,
Let you consider this resource

http://www.svlele.com/piping/slurry_piping.htm

Good luck
Pierre

 

[MJCronin]

Agree strongly with LittleInch ......

At 20-25% solids, is this stuff like toothpaste or a wet sand mixture ? This makes a big difference

With only 10ft of gravity head driving this system, you may even get zero flow..... IMHO

MJCronin
Sr. Process Engineer

 

[mechanicalbro]

i was told density is same as % solids, the viscosity is similar to water. The highest flow we have seen on that flowmeter is 1100gpm

 

[mechanicalbro]

S.G 1.13

 

[mechanicalbro]

Also, just found t=out that we need to consider froth factor due to air line content in the line. froth factor of 1.25 can be considered

 

[LittleInch]

Two different things. The SG of 1.13 implies your density of solid is about 1600 kg/m3.

So you do know what the viscosity is!

So if you're now getting 1100 games, why do you think this frothy mixture can suddenly double in flow rate?

Please take some time and tell us the FULL story and then we might get somewhere.

No one can calculate anything until you actually provide some details on what this stuff is.

Also as you have a low point, there's no way this will have an air gap for the "froth"

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

 

[mechanicalbro]

thanks again for trying to help. The current configuration does 1100gpm and i was asked to determine what line size should we upgrade the line for it to achieve 1750gpm. Other than that, the material properties that i gave all are what i received. Please let me know what additional information you will need to determine this.

 

[LittleInch]

ON that basis, you need to turn your "8" pipe" or whatever actual PE size it is into the same size as your bigger pipe (~12").

PE pipe tends to come in different sizes than steel so would be good to know exactly what OD those pipes are? but make it all the same as the bigger pipe and you're good for more or less the same velocity you have now.

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

 

[LittleInch]

but to size this prooerly you do need to have all the data I've listed above.

If this is the same viscosity as water what is this stuff?

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

 

[mechanicalbro]

Thank you. I will try to upgrade entire line to 12" hdpe. The current configuration has all HDPE SDR 11 on both 12" and 8" pipes.