WILO sump pump-selection issues

[moideen]

4 LPs at 37 meters are designed a sump pump for a new project. I just looked at their submission, and from what I can tell, the system head curve isn't shown. This pump will move water at the design head at a rate of 32 l/s instead of 4 l/s, and both the power input and NPSR will go up. The hydraulic data does not match what was asked for or what was planned. If I'm wrong, please correct me.[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1672298787/tips/wilo_sump_pump_bfypdf.pdf[/url]

The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-

 

[TugboatEng]

You may find that the manufacturer does not have a pump capable of making your requested head pressure while having such a low flow rate. The pump specified is likely the lowest flow rate that can exceed your pressure requirement. You can use orifice plates to reduce the flow rate. You should verify that 4 l/s exceeds the minimum flow rate required by the pump.

 

[moideen]

Thanks, TugboatEng. Right now, I can ask team WILO to come up with a selection that matches the consultant's design value. There is nothing in the submittal about how the valve or orifice plate would slow the flow.

The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-

 

[LittleInch]

Be careful as you're mixing units.

At 37m head , the flow is 32 M3/hr = 8.8 L/ sec, not 32 l/sec. SO double what you want.

But at 8.8 l/s, what is your system resistance?

No pump supplier I know puts on a system curve because they don.t know what it is. That's down to you to do that?

As a sump pump I imagine quite a bit is static lift, but not all of it, so there is a curve element to it.

At this size of pump, vendors provide set sizes and generally don't alter them except in steps.

If this is too big for you then find a smaller pump from another vendor or see what the next one down is in their range.

How did you get to 4 l/sec? Would 2 be ok?

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

 

[moideen]

@LittleInch; After head calculation, the design consultant gave a value of 4 l/s at 37 m. There is one duty/one standby. The vendor sends 8.8 l/s for 46 meters. Even though the selection shows a steep curve, at 37 m or lower, the flow will be doubled.

The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-

 

[TugboatEng]

The manufacturer has to supply a pump that "exceeds" your specifications. This will always be the case. The listed pump is likely the one that exceeds your specifications by the smallest amount.

If you need to reduce performance look in to impeller trimming or VFD speed control.

 

[LittleInch]

"The vendor sends 8.8 l/s for 46 meters."

No he didn't. He's sent a pump which would do 8.8 @ 37m or 4.3l/sec@47 m

It all depends why the consultant chose this figures and how big the sump is and what is the inflow of water.

Too big a lump and the pump will stop and start and liable to burn out, but we know nothing about how this pump is supposed to work.

It might be ok, it might be oversized. We have no idea.

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