Minimum Allowable Velocity in Pipe
Minimum Allowable Velocity in Pipe
(OP)
Hi,
I am working on installation of water wells. The design is for 15 wells in total, each wells should give me a maximum of 50GPM. In the design we received each group made of 5 wells is connecting to a 100mm HDPE line and the 3 groups branch together in a 200mm HDPE. At the moment we can only start up one group, which means I would only have 250GPM in the 200mm.
My research on the internet mostly ended up about Maximum velocity in lines and I found no serious documents on how to calculate the minimum velocity. I read somewhere that the 'rule of thumb' for the minimum was between 0.8-1m/s. From my calculation I would only have 0.14 m/s in the pipe (but than again, even with the 15 wells I wouldn't reach 0.8m/s ... ).
So my question is, is it dangerous when I get in very low density that the water will 'stall' ? If so how do I calculate it ?
Thank you,
I am working on installation of water wells. The design is for 15 wells in total, each wells should give me a maximum of 50GPM. In the design we received each group made of 5 wells is connecting to a 100mm HDPE line and the 3 groups branch together in a 200mm HDPE. At the moment we can only start up one group, which means I would only have 250GPM in the 200mm.
My research on the internet mostly ended up about Maximum velocity in lines and I found no serious documents on how to calculate the minimum velocity. I read somewhere that the 'rule of thumb' for the minimum was between 0.8-1m/s. From my calculation I would only have 0.14 m/s in the pipe (but than again, even with the 15 wells I wouldn't reach 0.8m/s ... ).
So my question is, is it dangerous when I get in very low density that the water will 'stall' ? If so how do I calculate it ?
Thank you,





RE: Minimum Allowable Velocity in Pipe
RE: Minimum Allowable Velocity in Pipe
Dejan IVANOVIC
Process Engineer, MSChE
RE: Minimum Allowable Velocity in Pipe
It answers my question.
And yeah you are right Emmanuel, my mistake I meant 50LPM.
RE: Minimum Allowable Velocity in Pipe
This flow seems quite slow (note 0.14 x 3 = 0.42 m/sec for all 15 wells) so unless you have some very serious head loss issues, you seem to be using a bigger pipe than you need to...
Otherwise I agree with the others - there is no recognised minimum flow for lines with no solids.
The only other issue with low velocities is that they will not sweep out any bubbles or areas where air can gather e.g. at the top of a hill and this can lead to sluggish flow or surging if it gets too bad and air is not bled out. Also pigging becomes quite difficult below 0.5m/sec and the pig tends to "hop" along the line.
This all applies if the pressure is maintained in the line to prevent slack flow, but you haven't given any details.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Minimum Allowable Velocity in Pipe
From my calculation I will be in the fully turbulent flow.
Good point for the air accumulation, I will make sure to install a saddle + valve at the high points.
Pumps will be running 24/7 and a expending pressure vessel is connected to the system, so pressure should be maintain.
RE: Minimum Allowable Velocity in Pipe
If so you might find the system very difficult to start or commission and hence it will become your problem....
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Minimum Allowable Velocity in Pipe
I haven't heard of a well that wouldn't be susceptible to getting some sand out of it at one time or another. A reasonable minimum line sweep velocity is a good idea to keep in mind.
RE: Minimum Allowable Velocity in Pipe
RE: Minimum Allowable Velocity in Pipe