Ideal motor for pumps question 1

[PUMPDESIGNER]

I have a question that everyone is welcome to respond to (please do if you can help), but acmotorengineer is specifically requested to respond.

Most of the pumps I work with are larger than 5 hp, but my company would like to get back into providing highly controlled small pump packages. We lost this market due to severe price cutting by competitors using very inferior equipment that we cannot use.

The horsepower range will be 2, 3, and 5 hp.
Pumps will be centrifugal.
Motors will be 3500 rpm, 1 & 3 phase, TEFC.

We do not assume that the entire industry went the right way 30 or 40 years ago, so we are starting from scratch.

Pump can be horizontal or vertical.
Pumps will be either close coupled or framed mounted.

JP, JM, and other similar type motors have problems:
1. Excessive impeller overhang (bearing problems)
2. Production quantities too low (high price)
3, Long thick shafts (high price).

We will design the pump to fit the best motor value we can get. Priorities for the motor are (in proper order):
1. High quality
2. Easily available
3. Capable of moderate thrust loads
4. Price

In this market we have made one key observation:
The pump is secondary, the motor is the main issue as far as reliability of the pump assembly.
What is the best motor type(s) to design the pump around? Richard Neff
Irrigation Craft

 

[acmotorengineer]

Your best bet is to find the lowest cost product and test it, under normal application conditions and extreme application conditions, to failure.

You will need to do extreme testing on a routine basis. Motor design quality and manufacturing quality is constantly changing from manufacturing equipment changes, material changes and workmanship changes.

Don't discount the CCP motor - it has a really good mix of design and price. i.e. large output bearing, locked for internal thermal growth, close mounting tolerance, high efficiency with spike resistant wire, and low OEM pricing structure, if you can get it, and high availability.

There are some unbelievable low prices from off-shore manufacturers (i.e. dumping), but you need to carefully evaluate what you're getting. You should be OK with a comprehensive testing program per above.

RE: single phase - you have most reliability problems with this product. Be sure your manufacturer supplies both three phase and single phase, unless your primary volume is single phase, in which case you can buy three phase from a larger list of suppliers.

RE: "The pump is secondary, the motor is the main issue as far as reliability of the pump assembly", motor people thought it was the other way around ??

Good Luck.

 

[PUMPDESIGNER]

Thank you acmotorengineer.
I thought you might pick up on that little statement about the motor being the main issue.
I put that in my post because many pump manufacturers treat motors like a commodity - "All are the same, lowest price wins".

No comment on the JP & JM impeller overhang?
Richard Neff
Irrigation Craft

 

[jbartos]

Suggestion: Visit

http://www.armstrongpumps.com/Data/pdfbrochures/Links/01_01_004/Series4280MotorMounted_2.11.pdf

http://www.griswoldpump.com/cent/cent.htm

http://airpowerofohio.com/pumps.htm

etc. for more info

 

[PUMPDESIGNER]

Thank you jbartos.
I am studying those sites now.
Richard Neff
Irrigation Craft

 

[acmotorengineer]

Re: pump overhang - that is why the big bearing and close tolerance.

You might want to also investigate a partial motor. This is where the motor manufacturer only supplies the back half of the motor. The motor frange register mounts directly to the pump housing. The motor shaft mounts the pump impellars. This eliminates the shaft end motor bearing and motor end bracket and the pump input bearing. Very low cost.

Drawback - tied to one manufacturer, because most registers are different. However a minor pattern change will allow you to accomodate another vendor.

Drawback - normally requires overbolts.

One manufacturer supplies a thru bolt thru the rotor for a one bolt attachment. Normally for 4P and 6P, but may work on small 2 Pole.