Colebrook-White Approximation - Goulds Pump Manual

[Jay_1995E]

Hi Everyone,

This is my first post however I have been reading the forum for years!

I have recently started a new job in the food and beverage industry. Their existing pump calculation is based on the 1982 Goulds Pump manual apparently. I cannot track this down and have never come across it previously. The K values vary based on pipe size which I believe is close to Cranes method, however the numbers don't match Crane's 410.

The Colebrook-White approximation that is used is below:

0.0056*(1+(18000*(e/d)*1+31*(e/d)+1248000/Re)^0.32)

I have no idea where this approximation has come from and can't seem to track to down!

I have compared the calculation overall with the 3-K fittings method and the Haaland approximation and the figures aren't too different for water. However, the calculation sheet is used for varying fluids of varying viscosity. There have been reports of pumps being oversized and having to be throttled back significantly during commissioning.

I am trying to push to update the calc sheet to the 3K method. Any insight into the accuracy of the Gould Manual or the source of the above approximation would be greatly appreciated. I am uneasy about using a calculation that I don't know inside out and back to front. I am of the opinion that a system should be sized as accurately as possible (given how easy this is with excel etc) and the a % contingency added.

Thanks in advance,

Jason

 

[Latexman]

Jason,

Did you look at faq378-1236 and faq378-1237 ?

Did you Google it? I did - Colebrook-White equation

I think the Goulds Pump Manual (GPM) method would be fine for water. It's almost always turbulent. What is your viscosity range? Maybe there were cases that were in the transitional or laminar flow regime.

Good Luck,
Latexman
Pats' Pub's Proprietor

 

[Jay_1995E]

Hi Pat,

Thanks for your reply.

I did have a good look through google to try and find it and couldn't see anything, It looks like a modification of the Moody equation?

The viscosity could go from 1 up to 890cP! I can't see Gould's holding for that?

Jason

 

[Latexman]

A' la Tony Stark, I am Latexman. The first Pat retired and the second Pat passed away. So, I am the current proprieter of "Pats' Pub".

Correct, 890 cP will probable be laminar flow, and there needs to be corrections made to the pump curves per the Hydraulic Institute.

Good Luck,
Latexman
Pats' Pub's Proprietor

 

[Jay_1995E]

Apologies Latexman,

Thanks for your advice.

Jason