×
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.

#### Jobs

(OP)

Motor is 50hp. Pressure gauge on discharge is reading 116psi. CAD drawing says the pump is 465 gallons @ 245 ft TDH. Does this mean the impeller should be trimmed to ~8 inches? Thanks.

### RE: Help reading pump curve

116 psi = 266ft.
What is the impeller diameter now?
What is the current draw at 116 psi?
What is the actual motor speed at 116 psi, not curve speed?
What is your problem - if you actually have a problem?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

### RE: Help reading pump curve

(OP)
The pressure is too high and I'm not sure if the impeller ever was trimmed. I'm just wondering if the impeller were trimmed to 8", based on the curve, shouldn't the head be closer to what specs call for?

### RE: Help reading pump curve

Depends of a couple of things, but in theory yes, that's assuming the impeller is oversized.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

### RE: Help reading pump curve

first question: discharge pressure is 116 psig. what is suction pressure?

### RE: Help reading pump curve

(OP)
Suction pressure is about 15. There is a dp gauge across the pump and it's usually around 98 psi. I also did some more research this morning and found that the impeller was trimmed to 8".

### RE: Help reading pump curve

What is the pump speed? not the curve speed.
Can you measure the flowrate?
The pump is probably just running up the curve, it will run against the imposed head - not where you want it to operate.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

### RE: Help reading pump curve

465 gpm @ 245 ft differential head is your pump duty point. Unless TDH is supposed to mean something different to differential head....??

Your differential head, assuming you are pumping water is 225 ft. Not much of a difference but your pump curve is quite flat, hence you flow could be somewhere around 550 gpm for an 8" impellor. Just as well they put the bigger motor on it....

The pressure is too high for what? if there is no control valve on this system then the flow clearly needs the pressure you are generating, but then we nothing about your system.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Help reading pump curve

I see no mention of fluid density. Normally the power demand assumes water. A different fluid will mess with both your head-to-pressure conversion and your horsepower.

I used to count sand. Now I don't count at all.

#### 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.

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!