High Head Pumping of Well Water 4

[pumpingtips]

Greetings Earthlings,
Question about pumping 130 m3/h along a 12 km pipeline, clean water, TDH will be about 430m (static is 300m), minesite application. Pipeline diameter will be 8". Any recommendations for type of pump or system of pumps? Keep in mind that the plant consumption (destination end) may only require 70 m3/hr. Would you recommend ON/OFF pumping? or would you recommend to keep the pumps and flow moving and have two pumps in series with one variable speed. Appreciate some assistance and comments.
Regards
Pumpingtips.

 

[pumpingtips]

forgot to mention... the pumps are not the well pumps. The pumps in question are the transfer pumps located at the well head.
thanks

 

[TenPenny]

Keep in mind that the pipeline will have to be capable of the discharge pressure of the pumps. I would think that having two or three booster pumps spread out along the line would be more economical, but that probably depends on your geography and site specifics.

If you used one pump station, that's going to be some pretty hefty piping.

 

[LittleInch]

pumping tips,

That's not a particularly onerous duty or pressure as far as I'm concerned, so there are many options.

you need to work out how often this system pumps at 70 or 130. Maybe I haven't understood the planned operation, but if 70 is an occasional use, then just use a single centrifugal pump rated for 130m3/hr @ 430 m and accept that at 70 it won't operate quite as efficiently, but will use less power because the flowrate is less. You don't want a VFD for this duty as your static head is so high. Just back the pump down the curve a bit ( outlet pressure will go up so you will to throttle a bit at the far end to get to your 70m3/hr) using a fixed speed motor.

If 70 is your main flow and 130 occasionally then you will probably be able to get 2 identical pumps in parallel to work for the two flows. Your friction element of the pump curve is quite low compared to the static head so it should work well.

When you get pump quotes have a look at the power consumption at your flow rates as one big pump can be much more efficient than two smaller ones.

Again, without know what your planned operation is, whether you have storage tanks or not at either end, etc, it's a bit difficult to advise on the on/off option or continuous flow. Normally you would go for the continuous flow unless your flows in and out are very erratic.

Bit more info needed.

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[Valvecrazy]

If you put in well pumps large enough to produce the pressure you need, there would be no need for added complexity of an additional booster pump.

 

[pumpingtips]

TenPenny... the pipe runs along a valley next to a dry creek zone and it do not want to entertain intermediate pumping given the diesel generator requirements with associated costs.

LittleInch...great comments. You have grasped this well. The fresh water demand for the new minerals plant we are designing is quite low due to filtered tailings. But we do not know exactly what the demand will be. We think 70 m3/hr but it could creep up over time. The maximum well licence rate we have is 144 m3/hr. This will be the pipeline design flow rate. I like the idea of two in parallel, one spare, all fixed speed. What type of pump would you install. Feed tank is on the ground at the well head and has a capacity of 50 m3. I forgot also to mention that the pumps will be supplied by genset power with Eroom. Why is variable speed an issue with high static head. I realise that the sensitivity will increase but what type of issues does this cause? Is there potential instability from hunting up and down the curve?

Valvecrazy... I too like the direct pumping approach out the well to the plant. But if we include the well lift we will be close to about 550m. Thanks.

 

[itsmoked]

I believe with high static head the VFD will ultimately have little authority since the pump will need to operate very close to its rated speed to do anything at all against the high head demand. This renders the cost, complexity, reduced reliability, and efficiency hits all -- not worth it.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[EdStainless]

The head is no issue for high lift submersibles that are used in oil field opperations.
A REDA GN10000 is BEP at about 1600m3/day (10,000Bpd), it would take a 55 stage pump to deliver 550m of head, and the HP would be 175hp.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[LittleInch]

Variable speed doesn't work in these situations for high static head due to the way the flow and head changes with speed.

If we assume at 70 m3/hr for the same pipe, pump etc, your required head is 340m (300m for static and 40 for friction), then your speed needs to reduce by about 11% ( head is prop to speed^2)

However this only reduces your flow by 11% = 115m3hr. To get to your 70 you will need to move along (left) the pump curve using a control vslve. A VFD isn't worth it.

you do need to work out your design cases though and also how you plan to operaste and control the system.

There's nothing wrong with piping the well pump straight into the inlet of the second pump. in the main higher power submersibles will cost more than the same pump on the surface.


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

 

[pumpingtips]

Some great comments from you all and has helped a great deal, even towards put the correct phrasing in a project memo. Such is the value of good discussion "over a coffee".
all the best.

 

[Artisi]

If it were my project, I would design pipework, sites and electrics for the maximum condition and select a smaller pump unit to cover the lower flow rate with a bit of latitude to increase the flow and head as conditions change, you can then move onto a larger pump unit once conditions dictate the need to change.

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.)

 

[77JQX]

If this was my project, I'd design for one constant speed pump at buildout demands and use on/off controls. I don't think you'll save money by installing a smaller pump now and replacing it later.

 

[pumpingtips]

Plunger pumps too expensive for this duty? Just worried about the variability of flows, and accompanying NPSH issues if only one of the two / three pumps is operating. We are at altitude (4500) and low atmospheric pressure brings the NPSH evaluation to the forefront a bit more than other projects. Other issue is cold conditions and potential freezing. Keeping the fluid running is preferable, even at small flows.

 

[LittleInch]

NPSH would be better at low flow.

4,500m is some altitude! Where are you - the Andes?

If you're hurting for NPSH, then either lift the tank or lower the pump. A can pump will do this duty easily. Many ways to not have NPSH bother you, given you're going to find it pretty hard to breathe at that altitude...

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