×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Pipelines, Piping and Fluid Mechanics engineering FAQ

## Flow in Pipe

 NPSHa - Net Positive Suction Head available by itsmoked faq378-1598 Posted: 12 Jan 10 (Edited 16 Jan 10) This FAQ is a reduction of tbarkerjr's question and BigInch's response on: 12 Jan 2010.I found it to be clear, concise, and informative.Thanks you two!----------------------------------------The only two that are important are NPSHa and NPSHr.  You don't calculate NPSHr, you get it from the mfgr's pump data. You only have to calculate NPSHa which must be >= NPSHr.Use absolute pressures. (If tank is open or closed, it makes no difference to the equation, as long as you calculate the tank's absolute pressure correctly).  Vapor pressure is always absolute.NPSHa = p(on_fluid_surface)/y - p(v)/y + v(s)^2/2g + h(e) - h(l)Note: The velocity term can be ignored normally as it doesn't contribute significantly.p(on_fluid_surface)absolute pressure on_fluid's_surfacey = specific weight of fluidv(s) = velocity of fluidg = acceleration of gravityp(v) = vapor pressureh(e) = elevation from surface to pumph(l) = head lossThe sign convention for h(e) is positive when the fluid surface is above the pump and negative when below the pump's Center Line(CL).Dropping the velocity term is common as it's almost always relatively small, not worth calculating, and yields a conservative result. Back to Pipelines, Piping and Fluid Mechanics engineering FAQ Index Back to Pipelines, Piping and Fluid Mechanics engineering Forum

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!