Pump Selection for Lift Station 2

[allie075]

I'm a new engineer who is just getting into designs.
I have to design a lift station to handle 0.127cu m/s of flow. I've calculated the horsepower requirement for the pump(s) but folks at the office think i shouldn't have. They say all i need to give the manufacturer is the flow and TDH.
Is this standard engineering practice? The HP rating is 100. I'm thinking about 2-50HP pumps and 2 more for standby. I was thinking that during low flow, one pump could be used...possibly. Also, more pumps would give the system more robustness.... minimising the risk of the station being out of operation. (Note: This LS serves a large area). The office folks say 1-100HP and another standby. Please tell me what you think, i don't want to fall into lax engineering practices.

One more thing...the equation: Water HP = Q x TDH/3960, would it work for sewage pumps?

Looking forward to your responses,
Allie

 

[Pipeline1972]

I ALWAYS have to calculate the HP, if only to coordinate with the electrical folks. They need this number for their design..


Process - Piping

 

[Artisi]

I would suggest 3 x 50% pumps, this gives you sufficient coverage and standby capabilty.
If very low flows are expected 1 unit could even be put on VFD drive - plus 3 units can also cover for any exceptional high inflows should this ever occur.

Your HP calculation should be Q x TDH / 3960 / pump Eff.

And yes, the HP calc. is of use for a couple or reasons - 1 as pointed out by Pipeline1972 and secondly it gives you a fell for what size equipment you are looking at.

 

[BigInch]

If you don't calculate power, how are you going to know how much it costs to run the pump? Not knowing power cost makes optimizing the flowrate-pump power-pipe diameter very difficult. Seems your company doesn't worry much about energy efficiency.

"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics

http://virtualpipeline.spaces.msn.com

 

[allie075]

Thank you Artisi (and everyone else). What I wanted to know in particular is whether you've used that TDH formula on sewage pumps as opposed to water pumps. The density of sewage is slightly higher and I wanted to know if the 3960 constant was computed taking this into consideration.

Thanks again,
Allie

 

[BigInch]

No, that's for water. If density is different, multiply by the specific gravity of your fluid (water = 1)

"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics

http://virtualpipeline.spaces.msn.com

 

[stanier]

ITT Flygt have some free software for design of sewage pump systems. It is known as Flyps. You could possibly download same or get you local sales guy to provide a copy. ABS & Grundfos pumps have similar software available. I am sure others also have software. I only mention these as they are the most common in Australia although they are worldwide companies.

If you use their software then you can select the pump that best suits your system and all its scenarios.

 

[allie075]

Stanier,

Omigosh...Thanks a million! I didn't get flyps but in my search, i stumbled upon PUMP-FLO.com and this site is amazing...it has got a pump selector for every manufacturer i've ever heard of and many, many more.

So, once again, thanks for the heads-up on the free software availability.

Regards,
Allie

 

[Artisi]

Allie
How about posting the link to PUMP-FLO

 

[BigInch]

Its a "free" demo.

"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics

http://virtualpipeline.spaces.msn.com

 

[Artisi]

Thnx

 

[allie075]

Artisi

Just in case you still want the link, it's attached.