Pump Designing
Pump Designing
(OP)
Hi All,
I am going to replace an old constant speed pump with a bigger capacity VFD driven pump. This is a result of an increasing demand of potable water in the locality.
old pump has these numbers:
Size 10 x 12 x 13.34"
Motor HP 250
Capacity 4,150 GPM
TDH 150 ft.
RPM 1775
Please give me your opinions on what size is appropriate if my expected peak demand is 12000 GPM and minimum demand of 3,800 GPM. Will it make sense if i use the existing head of 150 ft. as the basis of my computation for HP requirement? You can ask me other data you may want.
Thanks for the helps...
I am going to replace an old constant speed pump with a bigger capacity VFD driven pump. This is a result of an increasing demand of potable water in the locality.
old pump has these numbers:
Size 10 x 12 x 13.34"
Motor HP 250
Capacity 4,150 GPM
TDH 150 ft.
RPM 1775
Please give me your opinions on what size is appropriate if my expected peak demand is 12000 GPM and minimum demand of 3,800 GPM. Will it make sense if i use the existing head of 150 ft. as the basis of my computation for HP requirement? You can ask me other data you may want.
Thanks for the helps...





RE: Pump Designing
Or employ an engineer experienced in this field.
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: Pump Designing
First off you need to try and figure out what your system curve is that you're pumping into. Probably quite difficult for a potable water supply, but if you can try plotting flow rate vs pressure to see what sort of curve it gives you and then try and extrapolote for your much higher flows you are looking at, but if this is a fixed speed piston pump I don't know how you can vary flow at the moment?
When you increase flowrate, your required head will increase by a different (higher) factor than flowrate depending on what your static head loss is.
Before you can work anything else out work this out.
Also think about having a mixture of fixed speed units to do your base load and then a VFD to work the extra load. Having a 3:1 turndown on a single pump will be quite ambitious and will be difficult to work efficiently or effectively. Read up on VFD pumps on this forum - there's lots of previous posts on things similar.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pump Designing
More thought and data needed.
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: Pump Designing
A three fold increase in flow should mean a whole heap more system resistance and power consumtion unless, as usual, there is a lot more information which we're not being told. A 3: 1 turndown a single unit is still a bit high IMHO.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Pump Designing
So GPM increase around 3 times, and it is huge change.
If static head is 0, then TDH will increase 9 times, about 1350ft of TDH!!!!
So you may take care about pipeline system too.
Maybe modify to try to not to go to 1350 ft.
If you like to keep 150 TDH constant, you have to calculate pressure losses on pipeline
for these new capacity to see with which pipeline diameter TDH will keep constant.
At 12000 GPM @ 150 ft, you will need a split case pump around 18x20x30 or 14x16x26.
I hope it helps.
RE: Pump Designing
regards,
arthur stack
softedge=innovation