Using Nomographs

[Cheese]

Why is it that when I try to solve problems using nomographs, the answers are typically errored signifigantly.

I've tried to use

http://dl.clackamas.cc.or.us/wqt121/hazen-williams-6.pdf

same as the H-W nomograph in the CERM

to solve several problems (example 101 solved 4th ed. proble 3.1 page 11) with little success.

I am trying to be very careful with my lines, but still - huge errors.

Am I using this method incorrectly?

Using these methods would be a huge time saver, but is this a lost cause?

Cheese

 

[mmmbeer]

Why is it that when I try to solve problems using nomographs, the answers are typically errored signifigantly.
I've tried to use

http://dl.clackamas.cc.or.us/wqt121/hazen-williams-6.pdf

same as the H-W nomograph in the CERM

to solve several problems (example 101 solved 4th ed. proble 3.1 page 11) with little success.

I am trying to be very careful with my lines, but still - huge errors.

Am I using this method incorrectly?

Using these methods would be a huge time saver, but is this a lost cause?

Cheese

Cheese . . .

usually these nomographs are FAIRLY accurate . . i believe you are making a mistake somewhere . . . .

do yourself a favor and order a Gravity Flow calculator from the National Clay Pipe Institute.

WWW.ncpi.ORG

ITS WORTH IT!!

GOOD LUCK!

 

[Guest]

Why is it that when I try to solve problems using nomographs, the answers are typically errored signifigantly.
I've tried to use

http://dl.clackamas.cc.or.us/wqt121/hazen-williams-6.pdf

same as the H-W nomograph in the CERM

to solve several problems (example 101 solved 4th ed. proble 3.1 page 11) with little success.

I am trying to be very careful with my lines, but still - huge errors.

Am I using this method incorrectly?

Using these methods would be a huge time saver, but is this a lost cause?

Cheese

Cheese --

I looked at problem 3.1 - I don't think you can use the nomograph you provided as part of the solution of the problem. Ultimately, you are looking for velocity (v) for each pipe length for substitution back into the Energy Equation. Velocity (v) cannot be determined from that nomograph you provided.

If you look in the back of the CERM, Appendix 17.E, Page A-32 has a Hazen-Williams Nomograph. This nomograph has an axis (column) for determining velocity. It is important to note---> This nomograph is for C = 100.

In order to use this nomograph for your problem (C = 150) you must correct the obtained value of V by the forumla

Vactual = (Vchart * Cactual)/100

You have to be really careful with nomographs and other charts. That's why it is important to get practice in now to figure out the pros/cons and common pitfalls.

Please post if you are still having difficulty with using nomographs or this problem.

JR

 

[Cheese]

hmmmm.

I just used the flow rates for each segment. Didn't bother with velocities. The pdf nomograph is in gal/min as provided.

Looking back, I can get 'close' to the head loss using the chart I provided.

I think I introduce lots of error due to the long lenghts of each pipe segment.

Pipe lenghts are 16000, 14000, and 8000 feet. Reading the nomograph off even a little, and then multiplied by 16000/1000 (x16) introduces some large errors.

My feeling is that nomographs would probably be 'closer' for shorter pipe lenghts.

Thanks for the help.

Cheese