Inadequate HP for a diesel driven pump

[Zuke]

I have a customer who has given me a pump curve that he wishes for me to compete with. When my quote came back "to high" (aren't they always), he said I used an engine that was much larger than another quote. When I showed him that the curve actually stated (on the power curve) the requirements and that I was going 15% over, he said he has seen the pump work with a much smaller engine (rated below the power curve requirements for the pump).

I know all the things that are suppossed to happen, but am i missing something? The pump curve follows the power curve from about 150 hp to about 255 hp and they are sizing a 225 hp engine and the punp will be running at several points on the curve. I do not think that I can ethically downsize the engine.

 

[rmw]

Are you required to pump all the way out to the end of the curve, or just provide the required power at the operting point?

rmw

 

[BigInch]

What power curve is it following exactly.
Head curves are the same for all products with reasonably low viscosities, however power curves vary with the specific weight of the liquid being pumped.
Pump power curves that come on standard pump catalogue curves, that are not calculated for your specific application, will be based on water. It sounds like you may have looked at one of those pump power curves based on water.
If diesel were to be pumped instead of water, diesel's specific gravity relative to water = 0.86 or so, the power required would be 14% lower than what would be needed for the same flowrate of water.



"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[Artisi]

Sizing diesel engines for pump drives can be a bit tricky,
1. are you sizing on the continuous rated curve?
2. are the opposition using the nominal power curve?
3. if using the nominal power curve you can accept some overload for short periods.
4. will the pump have sufficient NPSHa at the end of curve - if not then you probably don't require the higher HP.

Post the pump curve and the engine curve and the operating conditions so we can all see what you are talking about.

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.)

 

[Pumpsonly]

As Artisi pointed out, there are a few power rating curve for a diesel engine.
The power curve published by the engine manufacturer is based on a certain standard condition.
You need to derate the power according to site altitude and temperature.

 

[BigInch]

Sorry, I read what I wanted to read... so, Diesel engine, not diesel pump.

Perhaps the competition is using a higher operating speed to deliver the required power using a smaller engine.

-----------------------------------------
pumpsonly, you need to INCREASE the engine's rated power in order to get the required amount of power out of it after being derated for altitude and temperature.


"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[BigInch]

That would imply more maintenance costs for the higher speed pump.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[rickfer]

Perhaps the competitor quoeted an smaller pump.
So probably pump will be working at the extreme right of the curve.

Perhaps you quoted a bigger pump, and pump is running at the extreme left of the pump.

 

[Artisi]

Seems they both quoted using the same curve - see OP's post

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.)