Pump sizing for Sewerage Lift Station

[MCSEng]

We have just finished sizing the pumps for a sewerage lift station. The static head is approximately 40 meters water pressure gauge. The pump delivers approximately 19.8 litres per second.

The friction loss is approximately 5 meters water pressure gauge. In theory, the pump must overcome at least 45 meters water gauge pressure.

We selected a pump with a total dynamic head of 50 meters water pressure gauge. Is the maximum pump discharge pressure too close to the system pressure? Do you think that after say 1 year of operation, the system pressure can increase due to factors such as say soiling on the internal surface of the pipe? Too large a pump is inefficient. Are there any standards that provide a guide on how much greater the pump's TDH should be above the system pressure?

 

[BigInch]

Match the pump head to system head at design flow. If you follow the instructions when you selelct a pump, you will generally have left yourself some flexibilities for normal wear and tear and the change of system characteristics with age. You can usually fit at least the next larger sized impeller inside the same casing for example.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[Artisi]

What BigInch is saying is, select your pump with approx 85 -90% of full diameter impeller, this allows for future upgrades or an increase in head if the case arise. However, in saying this - there are engineeing decisions to be made based on many considerations only you or the designer can make as you are privy to all aspects of the station / pipline design.

It is worthwhile calculating 1, 2 or even 3 system curves for the hydraulic requirements of the station, ie 1.) new condition 2.)fouled pipe line and 3.)any anticipated increased demand.

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.)

 

[stanier]

Download Flyps from ITT Flygt or preferrred pump manuafcturers website . This will enable you to do the calculations and check the vendors selection.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

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