Pipe size adjustment with pulp consistency
Pipe size adjustment with pulp consistency
(OP)
The number below are velocities in pipes depending on stock consistencies, from what i know these are the recommended velocities you should aim for in your pipes. But i am trying to understand how companies that design pipes come up with these numbers, and if it has anything to do with the Duffy method for pulp friction loss calculation. They usually have a fixed flow and try to change pipe diameter thus changing the velocity in order to get optimal results for their pipe system.
Pipe size(diameter)/velocity is adjusted with c%
Water: discharge pipe: 3-4m/s
Stock 0.1% to 1%,discharge pipe: 2.5-3m/s
Stock 1.1 to 2.5%, discharge pipe: 2-2.5m/s%
Stock 2.6 to 3.5%, discharge pipe: 1.5-2m/s
Stock>3.5%, discharge pipe: 1.5m/s
Gravity line or lines on inlet to pump, velocity is 1m/s
Thank you,
Fadi
Pipe size(diameter)/velocity is adjusted with c%
Water: discharge pipe: 3-4m/s
Stock 0.1% to 1%,discharge pipe: 2.5-3m/s
Stock 1.1 to 2.5%, discharge pipe: 2-2.5m/s%
Stock 2.6 to 3.5%, discharge pipe: 1.5-2m/s
Stock>3.5%, discharge pipe: 1.5m/s
Gravity line or lines on inlet to pump, velocity is 1m/s
Thank you,
Fadi





RE: Pipe size adjustment with pulp consistency
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pipe size adjustment with pulp consistency
RE: Pipe size adjustment with pulp consistency
If you want correct velocities use Duffy's data,available on the net, check Gould pump website.
I did a lot of work with Geoff Duffy and his data is valid.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pipe size adjustment with pulp consistency
I don't know a lot about pulp mixtures and what their viscosities are, but from the data above my suspicion is that the viscosity increases a lot over that percent and hence what they are trying to do in a fairly course manner is keep the pressure drop similar for each percent increase and hence as viscosity increases you decrease velocity to hit the same band of pressure drop.
If you have available the viscosities for those percentages this might shed a bit more light, but that's my best guess at the moment.
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RE: Pipe size adjustment with pulp consistency
For over 10 years before Duffy rewrote the rules, I used standard water friction data for upto 6% stock which is the approaching the upper limit for std. paper stock pumps. For interest at 6% you can walk on the stock with snow shoes (so Duffy said although I never tried it😊).
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pipe size adjustment with pulp consistency
Can you please also explain how duffy's method is used ? I know it is used to calculate pulp friction losses, but then what? assuming i am designing a piping system. I read the TAPPI technical sheet and the explanation about the pulp flow at low, medium and high velocities.
also in duffy's method,bulk velocity is known whereas when designing a piping system and trying to find the optimal diameter, it would be a result of that diameter and thus wouldn't be known. (is it assumed and then changed by trial and error until the pulp friction loss value is minimal ?)
Thank you for your quick response btw
RE: Pipe size adjustment with pulp consistency
http://www.eng-tips.com/viewthread.cfm?qid=119063
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pipe size adjustment with pulp consistency
RE: Pipe size adjustment with pulp consistency
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pipe size adjustment with pulp consistency
It's pretty clear to me that this stuff is a bit weird in it's properties, but equally has been studied a fair bit and there is a lot of history and background to it.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pipe size adjustment with pulp consistency
RE: Pipe size adjustment with pulp consistency
Could someone answer these questions that i previously asked pls
"Why are those values nonsense ? These values were given to me by the head of engineering at the tissue mill i am interning at, saying that they were standard values used by pipe system design companies. Can you please explain in which way do you consider them nonsense?
Can you please also explain how duffy's method is used ? I know it is used to calculate pulp friction losses, but then what? assuming i am designing a piping system. I read the TAPPI technical sheet and the explanation about the pulp flow at low, medium and high velocities.
also in duffy's method,bulk velocity is known whereas when designing a piping system and trying to find the optimal diameter, it would be a result of that diameter and thus wouldn't be known. (is it assumed and then changed by trial and error until the pulp friction loss value is minimal ?)"
RE: Pipe size adjustment with pulp consistency
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Pipe size adjustment with pulp consistency
RE: Pipe size adjustment with pulp consistency
They tend over time to develop certain guidelines to get them an initial sizing and layout without having to spend hours analyzing each small section of pipe. These guidelines have generally proven themselves over time to provide the optimal solution or fairly close to it. They are though guidelines and this issue of velocity in pipes appears on a regular basis with engineers wanting hard numbers and code references. They don't exist.
As the percent pulp increases, from what I've seen, the viscosity does increase, but might start at low percentages to be lower than water, but ends up higher. Thus as your percent goes up the pressure drop goes up if you try to maintain the same velocity and gets to a point where it is more economic to increase the pipe size to reduce the velocity and pressure drop to a more reasonable number.
You might have other issues when you work with non Newtonian fluids like pulp - I saw somewhere you don't want to go too slow otherwise the stuff starts to stick and jump along the pipe (!!) and at reducers it can lock up. Then you need to find someone who's done this before and understand the weird behavior of the fluid.
good luck!
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pipe size adjustment with pulp consistency
That's what i thought at first, and i think there is some truth to it. But according to G.G.Duffy's model of the pulp friction loss curve, for a constant consistency (percent pulp), friction loss increases linearly, decreases until a velocity point called the onset of turbulence where it is minimal, and increases again to become lower than water once velocity reaches the onset of drag reduction.
Behaviour of pulp flow at different velocities is explained a bit in the TAPPI TIS along with Duffy's method and i have read a bit about pulp rheology.
I am trying to understand the procedure of finding optimal velocities and pipe diameters using (or not) Duffy's method for pulp friction loss calculation. Preferably using duffy.
RE: Pipe size adjustment with pulp consistency
If you have the time and inclination to read up on it you will pretty soon find yourself knowing more than many people who have been working with it for years... Just be sure to not rely on a single source of information, but try and make sure more than one source is there. If you're working in an operating plant, you have an ideal chance to take actual measurements and see of your calculations get close.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Pipe size adjustment with pulp consistency