Cost as a function of pressure.

[John31415]

Hi,
Can anyone point me to a comparison of the cost of pumps as a function of pressure (all else being kept constant).
For example, is it cheaper to use two 10bar pumps or one 20-bar pump (ignoring station cost) and how do these numbers scale with pressure and number of pumps.
If a complete curve of pressure vs cost is not readily available, would you happen to have some estimations for e.g. 10,30, 80 bar.
While I'm primarily interested in capital costs if you have some numbers of life cycle that is also useful.

 

[stanier]

Suggest you go to

http://www.pump-zone.com

http://www.mcnallyinstitute.com

http://www.pumpsystemsmatter.org

http://www.pumpfundamentals.com/pump_glossary.htm#gl441

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[John31415]

I can;t find any concrete numbers there

 

[1gibson]

Well, we can't find any concrete questions here so somebody is going to have to do some research.

I guess the answer is to look at the water horsepower and pump/motor efficiency.

 

[John31415]

The concrete question is how much does a 10-bar, 30-bar and 80-bar pump cost assuming we can control for everything else (such as flow etc). Representative numbers are good just trying to get a feeling.

 

[bimr]

The cost of pumps is directly related to capacity, perhaps indirectly related to pump discharge pressure. Pump HP is directly related to capacity as well.

 

[bimr]

Here is a link to an estimating method. The pump cost estimate is related to pump HP.

http://www.pdhonline.org/courses/g127/g127content.pdf

 

[Pumpsonly]

Cost of a pump is directly related to both capacity and discharge pressure/differential head.
Your question is too general to answer.
For a 20 m3/hr pump the factor of cost increase from 10 bar to 20 bar is definitely much lower than a 200m3/hr pump.

 

[GHartmann]

Unfortunately you're going to have to look at this with some more specific flows and pressures. Not to mention type of pump needed (vertical wet pit or horizontal centrifugal) and fluid being pumped.

Once you start getting into the higher pressure multi-stage pumps the complexity and cost of the pumps don't necessarily increase according to any rule of thumb.

The estimating method cited above mostly relates to scaling from one known cost to another.

Good luck.

 

[stanier]

I recall that there was some estimating information in Perry's Chemical Engineering Handbook that you could research.

You not only have to consider the pump(s) but also the pump staion, switchroom, cabling, switchgear, interconnecting piping, operation etc etc. It is a detailed estimating exercise not a rule of thumb thing.

Location can affect things as the ratio of labour to capex will be different.

Connected load versus power usage also affects tariffs.

Dont forget the dreaded carbon dioxide taxes or trading schemes.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[SNORGY]

The "point six" rule (or the "six tenths" rule in bimr's link) has always worked well for me.

 

[poli60]

John31415,
I'd just like to note that you can't substitute one 20 bar pump with two 10 bar pumps; you'll add the capacities but not the pressure!

 

[BigInch]

" you'll add the capacities but not the pressure"
True for parallel configurations, however in a series configuration, pump capacities can be roughly added together, exclusive of system curve effects.

If it ain't broke, don't fix it. If it's not safe ... make it that way.

 

[SNORGY]

In parallel pump configurations, assuming identical pumps, capacities "sort of" add but head "sort of" does not add. It depends on the system head curve to what extent either holds true.

In series pump configurations, capacities do not add but head does add.

 

[gerhardl]

Hello John31415!

Your original question is quite a 'classical' cost/value/lifetime question: how do I solve a process requirement best? With one or several mechanical components?

The variables are on a general basis:

a) Process specifications (as stated by others above) eg. here: fluid specification, amounts, delta P's, pipeline lengths, surroundings, etc.
b) Requirements for components: (as stated by others) such as: quality, materials, lifelength expectancy, power specification and consumption, type etc.

The third, and often underestimated, set of variables is:

c) Commercial surroundings: price of components, availability in market, state of 'art' regarding development of available solutions (available pump technology: is this the best/latest and to what risk/cost), experience and references for service and suppliers, cost/lifetime as comparison to buying cost, risk and responsibility evaluation for different mechanical solutions.

Conclusion: Your question can be answered, but only at asking suppliers directly and this only if points a) and b) are specified and c) is caretaken and specified. That is: for one set of specifications in one market, at a given time, but not generally answerable for all markets at any time.

In addition: different pump makers might have different increasing price steps for differing sizes and types.

Advice: Could possibly suppliers be asked for preliminary budget prices and suggestions (in their opinion) for best alternatives, giving their comments on one or two step solutions?

If equal dependability of all components a two step serial operation will generally tend to be higher in total installation, operational and maintenance cost than a one step operation, but this is not an 'absolute' truth.

 

[GHartmann]

I was thinking of this of as a pipeline installation where you might have 3 20 bar pumps along the way versus a single 60 bar pump.

If you are at a single specific site I would lean more toward the single no-series type installation just for simplicity. Your costs for intallation, electrical, piping, tend to go up proportional to the number of pumps installed.

You will also want to think of the pumps according to ANSI pressure ratings (150#, 300#, 600#, 900# etc) or their DIN equivalents. The higher pressure ratings begin to seriously impact the pump prices.

Good luck.

 

[poli60]

BigInch and SNORGY are perfectly right in their comments to my previous post. Thanks.