Pump Efficiencies

[macan]

Pumping water is an issue that comes up regularly on the forum and Maizefarmer recently mentioned the efficiency of a pto driven centrifugal pump. Rather than hijack that thread to find out more I thought I better start a new one.

Our 8" axial flow pumps used for draining ponds average about 65 cubic meters of water per litre of diesel with a maximum head required of about 4 meters. How does that compare with the pto or iron buffallo driven pumps?

[Maizefarmer]

Macan

I think its important to note that in reffering to “efficiency” I was not only reffering to the fuel costs but had in mind the overall versatility that pto power sources offer i.e. that one tractor with one portable pto pump can be used to take care of a dozen different tasks, as opposed to having different pumps and power sources – and that the “package” is easy to move around from one location to another.

Putting all the above aside, assuming the power source was matched to the pump, one wasn’t using any more power than was required, the pump had being chosen with suction head in mind, one had defined the time period over which they wished to pump the 65 cubic meters of water which would be more efficient – axial or centrifugal?

There are arguments in favour of both (like those mentioned above – and others) ….. axial flows are used in Thailand to drain/fill ponds because, without veined impellers they are able to handle small stones, fish and a load more stuff in the water than a centrifugal of the same size. They are also able to handle negative heads better than centrifugal, they don’t cost as much to purchase, they are easier to maintain (not necasserily cheaper in the long run), but centrifugal pumps take up a lot less space, they are easier/quicker to move around and put in position (is your pump being moved or is it only being used in one location?).

Another consideration would be how often is it used – daily, weekly, monthly, or less frequently?

Macan, I know you asked specifically about fuel consumption, but that would never be a stand alone factor in determining which pump was more efficient to run. It really needs to be considered against the background of a whole bunch of other practical issues.

From a fuel only point of view I can think of setups in which axial would beat centrifugal and I can think of setups in which centrifugal would beat axial.

One thing is certain though – it costs about half as much to drive any water pump in Thailand with 3phase than it does with diesel – so if you have a fixed location and can use 3phase, don’t even think of using diesel.

[chownah]

Our 8" axial flow pumps used for draining ponds average about 65 cubic meters of water per litre of diesel with a maximum head required of about 4 meters. How does that compare with the pto or iron buffallo driven pumps?

Your axial flow pump will be more fuel efficient than a centrifugal pump for the application you describe.

Here is a link to a pretty good talk about irrigation pumps comparing different kinds and discussing their various features:

http://www.ag.ndsu.edu/pubs/ageng/irrigate/ae1057w.htm

Chownah

[Maizefarmer]

Our 8" axial flow pumps used for draining ponds average about 65 cubic meters of water per litre of diesel with a maximum head required of about 4 meters. How does that compare with the pto or iron buffallo driven pumps?

Your axial flow pump will be more fuel efficient than a centrifugal pump for the application you describe.

Here is a link to a pretty good talk about irrigation pumps comparing different kinds and discussing their various features:

http://www.ag.ndsu.edu/pubs/ageng/irrigate/ae1057w.htm

Chownah

You speaking rubbish again Chownah - Macan has not provided sufficient information for you to make that calculation.

[macan]

Thanks for the analysis from MF, I appreciate the other factors you mentioned and am a big fan of broad utility in machinery, and thanks to Chownah for the nice link.

I wasn't trying to get in a pissing competition about 'my pumps bigger than yours' (or i would have mentioned the 12 inchers that run of pickup truck engines), what i wanted to know was if anyone had quantified the output and fuel use from these low rev pump setups. We've got several pumps here but not one of those so i was curious.

When I see these big pumps hammering away at full throttle I cant help thinking that there must be a better way. The pumps are in use several times per week and must be mobile to move from pond to pond. Switching some of them over to electric is probably on the cards and I see our local mechanic is doing a steady business in this. But i also would like to know what might be the cost of running another pumping system whenever possible even if it took a bit of planning because of the longer time required. I thought about a large bore Archimedes screw type pump as I understand them to be pretty efficient... maybe even hook some buffalo up to it.

Regarding mobility, I shall try to get a picture that my colleague took of the 3 wheeler self-propelling axial flow pump that we came across being driven along a road in Chachoengsao. It was built by an enterprising local mechanic and you can drive it into the pond, uncouple the drive shaft and couple it to the propellor to start pumping. It looks like something out of Mad Max.

[chownah]

For low head high volume pumping axial flow pumps are more efficient than centrifugal pumps.

Chownah