## Weymouth Formula Example

## Weymouth Formula Example

(OP)

Hi,

Have located a metric version of the Weymouth formula in ASPE Data Book Volume 2 (screenshot attached).

I am a bit confused about the results I am getting however.

If I enter the following data:

D = 98.34mm

L = 300m

P1 = 70kPa

P2 = 50kPa

S = 0.6

I get 12067601.01 which the formula notes as being L^3/s.

Could it be right that I then need to apply 1/3 as power to get plain l/sec i.e. 12067601.01^(1/3)

If I do I get 229.37 which is 825m3/hr which in turn is 31956 MJ/Hr which sounds about right but don't have anything to check against.

Urgently need a metric Waymouth example with results to check against.

K

## RE: Weymouth Formula Example

Q = flow rate of gas, m3/day at

baseconditionsTs = base absolute temperature, K

Ps = base absolute pressure, kPa (abs)

E = pipeline efficiency factor (fraction)

P1 = inlet pressure, kPa (abs)

P2 = outlet pressure, kPa (abs)

Lm = length of line, kilometers (km)

γ = relative density of flowing gas (air = 1.0)

T = absolute temperature of flowing gas, K

Zavg = average compressibility factor

d = internal diameter of pipe, mm

You also need to verify if the actual flow conditions fall within range of applicability of Weymouth formula.

Dejan IVANOVIC

Process Engineer, MSChE

## RE: Weymouth Formula Example

To me, it has been an invaluable resource for understanding and solving compressible fluid issues. It even has an example of using Weymouth and other natural gas equations and compares their results.

## RE: Weymouth Formula Example

## RE: Weymouth Formula Example

With today's computers I don't know why anyone would not use the Isothermal Gas Flow Equation and get friction factors from itteratively solving Colebrook. It is a pretty simple solve block and program in MathCad. Even doable in Excel if you hate yourself.

David Simpson, PE

MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.Galileo Galilei, Italian Physicist## RE: Weymouth Formula Example

## RE: Weymouth Formula Example

David Simpson, PE

MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.Galileo Galilei, Italian Physicist## RE: Weymouth Formula Example

## RE: Weymouth Formula Example

I agree with you about using the isothermal gas flow equation. I don't have a warm fuzzy for the empirical gas equations like I do for Hazen-Williams and Mannings for water. It's probably because I do so much more work with water distribution systems and sewer and storm drainage collection systems than I do with natural gas.

You and the others here may interested in some Mathcad worksheets I posted on the PTC Mathcad forums last year on this topic: https://www.ptcusercommunity.com/docs/DOC-5465 (an appraisal of more than two dozen approximations to Colebrook-White) and https://www.ptcusercommunity.com/docs/DOC-6371 (for small natural gas distribution systems). The Mathcad worksheets are Prime 3.0, but for users of other versions of Mathcad and for people who don't use Mathcad, there are also .pdf files for each worksheet. I have also posted Mathcad worksheets on other topics, which you can peruse at your leisure.

Comments and critiques are welcome (especially from experts…i.e., people who used to be perts), either here or on the PTC Mathcad forums.

Fred

==========

"Is it the only lesson of history that mankind is unteachable?"

--Winston S. Churchill

## RE: Weymouth Formula Example

## RE: Weymouth Formula Example

Even though I am often the prissy, picky "expert", I used to do much the same thing. Now, when I have to face some jerk as pedantic as I am I show them the results from the Isothermal equation and a list of the things about my problem that make each of the various equations invalid. That happened often enough that I developed this graph for AGA and Panhandle A (I have other graphs for other correlations, this one is kind of the Moody diagram, but I hate Moody's logarithmic y-axis)

David Simpson, PE

MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.Galileo Galilei, Italian Physicist