×
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.

# How do I calculate impeller size?

## How do I calculate impeller size?

(OP)
Currently I have a pump with an 11" impeller at a discharge pres of 22psi and 112GPM.

I'd like to know how much will the flow and/or pressure will change if I trim or increase my impeller size.

is there a formula for this ?

thank u

### RE: How do I calculate impeller size?

Flow may not change. Pressure will be proportional to diameter squared.

### RE: How do I calculate impeller size?

shup0739

For general terms the pump affinity laws apply to impeller size or rotating speed.

FYI:
22 PSI at 112 GPM sounds low for an 11 inch impeller.  Hope this is a slow running pump.

### RE: How do I calculate impeller size?

shup0739,

As suggested by D23 use the affinity laws to provide a rough appoximation of the effect of changing impeller size.

Q1/Q2=D1/D2
Hd1/Hd2=(D1/D2)squared
HP1/HP2=(D1/D2)cubed.

You can expect this formula to give you accuracy within 10 to 30%.

### RE: How do I calculate impeller size?

Affinity laws are the best equations to calculate and estimte the changes, however these are constant efficiency equations. But when there is a change in impellar size, efficiency does change and hence these equations may not predict the changes very accurately, however they definitely give a close estimate.

hope this helps.

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

#### Resources

White Paper - Implementing a Multi-Domain System
IoT systems are multi-domain designs that often require AMS, Digital, RF, photonics and MEMS elements within the system. Tanner EDA provides an integrated, top-down design flow for IoT design that supports all these design domains. Learn more about key solutions that the Tanner design flow offers for successful IoT system design and verification. Download Now

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!