pipe diameter & pump capacity 1

[ahmedalorafi]

Hello all:
For calculating the diameter of a polyethylene pipe and the capacity of the pump to supply drinking water in the quantity of 20 liters / second for a distance of 30 km and the difference between the points 20 meters on the efficiency of the pump 0.75 ...
Please help determine the internal tube diameter and pump capacity ??
Thanks

 

[LittleInch]

Have you tried to do this yourself yet?

The name of this site is "Eng tips", not "Free design engineering"....

Try looking at the website of a pipe supplier to get an understanding of the friction drop or try engineering toolbox.

https://www.engineeringtoolbox.com/

The plastic pipe industry website has a lot of good info and links

https://plasticpipe.org/

There - I've given you a few tips, now it's up to you.

Try doing it yourself and then come back here if you run into problems or don't understand anything.

LI





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

 

[Artisi]

Lesson 1, pipe friction loss 101. It should take you about 5 minutes to come up with a good estimate of the pipe size and calculate pump requirements. Of course the final pipeline engineering and pump selection will take much longer requiring a lot more info than you have supplied.

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.)

 

[SandCounter]

Find the flow rate (20 ^L/_s) and efficiency (75%) on your pump's curve supplied by the manufacturer. Use the corresponding head and flow from this point and input them into the following equation and solve for "D".

h = 0.0006 × ^F2/_D⁵ × L + h_lift

Where
h is head in feet
F is flow in gpm
D is pipe diameter in inches
L is pipe length in feet
h_lift is change in height from pump suction to discharge in feet

I used to count sand. Now I don't count at all.

 

[mk3223]

It looks like this is a good size of the pipeline project with the proper pump station as required. Instead of the quick and simple reply online, suggest to consult this with a professional engineer who can provide a design solutions, such as alternative options, cost estimate, etc., for a complete evaluation and final decision.
Good luck.

 

[ahmedalorafi]

Thank you for answering SandCounter ... Yes I have the calculations necessary for the diameter of the pipe used the following equation
d = (1.27Q/V)0.5
Where:
d = inside diameter of the pipe, in feet
Q = flow rate, in cubic feet per second
V = flow velocity, in feet per second
And obtained an internal diameter of 200 mm (ie, outside 250 mm and pressure of 16 bar HDPE) and after the loss calculation, the loss of 45 meters + 20 meters difference between the two points.
Pump capacity was calculated from the equation:

P =  g Q H (in watt) H=hl+h
P =13.08 kw
P= 17.5 horsepower
is that right?

 

[bimr]

No, the 200 mm diameter is too large for the flow. The pipeline velocity will be too low causing air binding and stagnant water. Consider a 150 mm pipeline with a 67.9 meter headloss if plastic pipe used. Add the 20 meters of elevation head to the headloss to size the pump.

Reasonable Velocities for the Flow of Water through Pipe:

Boiler Feed.............8 to 15 ft/sec
Pump Suction ............4 to 7 ft/sec
General Service.........4 to 10 ft/sec
City.......................to 7 ft/sec
Transmission Pipelines...3 to 5 ft/sec

Go to a basic hydraulics book. Try Cranes Technical Paper 410 as a reference for the above velocities.

Online Calculators

 

[LittleInch]

ahmed,

much better.

Now lets look at this another way.

PE is a great material, but it's not very strong so pressure ratings are limited. 30 km in PE is a long way so flow velocities need to be low to not exceed the pressure ratings. this makes the pipes much bigger than e.g. a steel pipe.

Unless you are limited to PE I would do an engineering assessment of the alternatives including pump costs and power costs. PE might still be cheaper overall, but until you run the numbers you'll never know.

Also you don't say anything about the terrain / elevation between your two end points. Anything more than 10-20m above or below the average gradient from one end to the other and you've got to start considering the pressure / head impacts of this.

Bimr - I think you're right on the velocity issue, but 68 meters head in a 150mm pipe (ID or OD?) for 30km doesn't look right. I get over 200m

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