Existing system, new pump, minor losses

[darthsoilsguy2]

Interested in hearing experiences putting a new pump on existing infrastructure and minor losses. i've got a system that i just can't explain at this time as to why we're not getting twice the flow from. The sole source pump distributor apparently doesn't comp system curves when they recommend a pump and haven't bothered to take a stab at the comps even for troubleshooting either so those guys aren't really a resource to tap.

i can't really put the entire project history and troubleshooting investigation here. The current troubleshooting idea we're tossing around is that the old pipe fittings have minor losses much greater than book values. i'm interested in hearing thoughts of what people use for existing fittings in their design assumptions. We use darcy-weisbach equation for the pipe losses

https://www.engineeringtoolbox.com/hazen-williams-water-d_797.html

and add the minor losses

https://www.engineeringtoolbox.com/minor-loss-coefficients-pipes-d_626.html

 

[bimr]

The current troubleshooting idea we're tossing around is that the old pipe fittings have minor losses much greater than book values.

Probably not.

Consider posting:

Age of system.
Length of piping system.
Capacity of system.
Pipe diameter.
Elevation difference.
Fluid properties, water, sewage?
NPSH.
Pump type.
Suction and discharge pressures.
Are all of the valves open?
What was the condition of the piping when the pump was replaced?
What do you mean by minor losses?
Original capacity compared to new capacity?
Why was pump changed?
Who sized new pump?

 

[LittleInch]

i've got a system that i just can't explain at this time as to why we're not getting twice the flow from.

Because maybe you don't have four times the pressure drop from the pump?
You're going to have give us the info bimr suggests to have even half a chance.

Surely for the old system you had performance data in which to create / benchmark your system curve? Then this will have already included the pressure losses within your current system.

Pump suppliers supply the pump you asked for. Designers work out what pump to ask for. Big difference.

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

 

[darthsoilsguy2]

sorry i just can't get into a crowd source troubleshoot here as much as i would like to. i do appreciate the comments and acknowledge i'm holding back info. the old system data was the compressed air pressure for 50-gallon ejectors so it wasn't very useful for benchmarking the system curve for a replacement sewage pumping system. seems like we're all three on the same page more than you might think.

 

[EdStainless]

So the original flows and pressure drops were unknown, and someone took a stab at a replacement.
Well, they aimed too low.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[darthsoilsguy2]

There is a risk to damage more expensive equipment owned by others if the system is arbitrarily over-pressured. I would like to stick to the topic of the OP and am looking for people's thoughts of minor losses being 2x, 3x, or 4x greater than off the shelf... or not much difference than shelf.

 

[bimr]

Unless the old pipe fittings have some sort of blockage, corrosion, or scaling, the minor losses will be in the range of the published data.

From your description, an older system using compressed air to blow sewage through some type of collection system will not have the same headlosses as a fluid system that is operating with pipes flowing full.

Are you familiar with the eone system that incorporates pd pumps?

 

[darthsoilsguy2]

thanks bimr. my thoughts were that minor losses in old pipes are not the droids i was looking for, but i had to throw it out there because others were pushing this concept and i was wondering if there might be something to it. the parts in question were scoped, 40 yrs so they are not new, but didn't seem alarming either...