Where Is The Knowledgable Pump Customer Service…

Have a look at this calculator....are you taking all these factors into account?

http://checalc.com/calc/pump.html

Yes, of course,... What your missing is you size the pump to the system curve... not to match the system the maximum of the pump curve.

My point being as an example, when it falls under a 25HP range to do the job of 200GPM @ 160 ft Head, what go beyond that. at , Why 800 GPM @ 120 ft HD.

It ridicules, because the system curve in the process can't handle it.

In this case, The process system itself is physically located is 30 ft above the pump the air with 12 spray nozzles designed at say 65 PSI (after you subtract the 30 ft head for process elevation), at 200 GPM. 16-18 GPM/nozzle.

I agree that running the pump as close to it's best efficiency flow rate is preferred....

http://www.waterworld.com/articles/print/volume-23/issue-12/departments/pump-tips-techniques/operating-pumps-close-to-best-efficiency-flow-rates-extends-life.html

I just never heard of NOL before,... and if left unchallenged, there are oversized motors to the pumps being spec'd out.

I'm going to have to specify that the spec's are for the system curve next time,... because over specifying the pump can really raise hell to the system.

Agreed, That's where the system curve is the basis of sizing a pump.

I have designed systems with modulating valves,... when that happens, I'll size a pump so its not at the border limits.

But to have a pump sized out with the HP that is capable of flow rate 4 times the requirement is ridicules.

Also, in past pump curves, they use to add efficiency of the pump, similarly to the HP rating.

But it seems pump curve graphics are getting really basic ^{(if any are readily available to the pubic in the first place)} and less information to them.

You are right, it seems the pendulum has swung the other way. In industry in the last 40 years, we would often find motors tripped out on overload because something in the process changed, a throttle valve left open, some piping change.

It used to be to get the job, the pump suppliers would size to the exact system requirements specified by the customer, because that was the lowest cost. Then some large industrial customers realized they were spending a lot of money and lost production time changing out pump motors, the bases would be too small, coupling spacing too short, the friction losses lower than expected, customer hydraulic design calculations incomplete. So many started specifying motors to run the pump out on the impeller curve, but usually starting close to the BEP, so not a huge investment like you are looking at. So in doing that, retrained some of the pump suppliers, perhaps a little too much, so now it appears to be a knee-jerk reaction with little basis in fact.

One needs to have planned ahead. We did an expansion about 3-4 years ago on a cooling tower. As I was sizing it, I was on a trip to the plant on the company plane with one of the owners and we were talking. He found out I was sizing the cooling pumps and he said, nonchalantly, "I can't give you the specifics, but whatever you size increase it by 50%."

I did.

But even if you expand a process, the pump curve does not change; one can easily check to see if the current specs of the pump can match the new system curve.

I can understand why a pump vendor would be reluctant to sell such a grossly oversized pump, even allowing for simplicity of spares inventory.

You can understand? How? Or you can't understand?

The other thing,.. This may be semantics, the pump isn't oversized, the motor is.

I was talking to our plant engineer, and he mentioned he noticed that Waukesha was oversizing the motors when he'd asked to spec'd out.

as I mentioned earlier, I used to size the out earlier in my career. And when I started working for the company were I'm at not, the plant engineer, told me that not my job, and to let the supplier do that. And only supply the requirements, but from now on, I will add specs for the systems curve.

its just this is the first time noticed NOL.

The reason the vendor is oversizing the motor is that the pump is oversized in the first place. It's kind of a CYA thing, of course, but the pump supplier can't guarantee that the end user has taken adequate steps to ensure that the pump won't run too far to the right on its curve.

That's the problem with incompetent engineers and sales, they cya to ridicules measures. Why have them and instead have one size fits all.

With the acceptance of this practice, they are spending so much time and effect and other people's money covering their incompetent asses, that if this is what engineers are coming down to, they are no longer engineers but just place holders.

ridicules ≠ ridiculous

effect ≠ effort

Thanks