Pump Sizing

[doomster]

In choosing a pump, what will be the safety factor for the head and flowrate that will be multiplied to your theoretical head and flowrate so you can meet your demand and anticipate the decline of efficiency over time of the pump for at least 10 years?
For our practice, an additional of 10% of the head and flowrate will be our allowance to account the decline in efficiency of the pump. Is it safe to only have a 10% allowance?

Thank you for your thoughts

 

[horacio Torres]

I use 10 % of overdesing.  If is a severe fluid services for the pump casing consider 15 %.

horacio

 

[LittleInch]

For a pump this isn't a safety factor, it's quite possibly a large waste of money.

The theoretical values are usually quite conservative so adding more margin on top of margin in design simply leads to pumps which in reality are 25% bigger.

Then they run inefficiently or create higher pressure and higher flow than you need.

Vendors often add on a little bit as well to meet the data sheet.

So think very carefully.

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

 

[don1980]

If we're talking about a centrifugal pump, there's no need to include any safety factor in the design values for head or flow. Instead, select a pump that can accommodate an increase in impeller size.

 

[bimr]

Agree with LittleInch, it is a waste of energy to oversize a pump and not necessary. Oversizing a pump has adverse results because the pump no longer is operating at its best efficiency point (BEP) for extended periods of time and and the design margin increases the cost of ownership.

Carefully review the method for calculating head loss in your pipe network.