Centrifugal pump with two suctions-curious.

[Teddy]

'Evening all
Attached I hope you will find pics of an unusual centrifugal pump.

Stands about 600mm (2 feet) high, shaft length about 1100mm, (3 foot 6"or  3 foot 7" approx)
Shaft diameter 1 1/2 inches, impeller diameter hard to tell, but about 12-15 inches.

Each suction is 5 inches diameter, the delivery is 6 inches diameter.

Both suction pipes have a tapping to allow fresh water to  pressurise the glands, normally found in bigger pumps and sludge and  gravel suckers.

I bought it from the Engineering School at the Uni of Tas, but they told me it came from the "Zinc Works", Hobart's well known zinc smelter, owned by Nyrstar. Its duty there was not known.

Seems to me some type of mixer pump. Anyone else have any knowledge of such a machine?

With thanks, in advance
Teddy.

[cobbadog]

That is one unusual pump Teddles.
Is it possible that it could have been used to pump out 2 tanks at one time? Or 2 inlets from elevated tanks and then it pressurises better?
As you can see I don't have a clue, just tossing out a few ideas.

[Teddy]

Thanks for your interest Cobba.

Both your thoughts have merit, no doubt.
We both await to see if there is a definitive reply.
Teddy

[Scott]

Hello Teddy.
I'm probably totally wrong here but I'm guessing the pump goes the other way. Inlet at the top and two outlets at the bottom.

Any arrows on the pump?

Cheers Scott

[rustyengines]

 I'm probably totally wrong
Sorry Scott, it is a centrifugal pump and the inlet has to be the in the center
I don't know what other people have been doing BUT my computer has been in over drive look at pumps, I can find twin outlets but not twin inlets on a centrifugal pump
I wounder if it is a 'one off' for a special use, Looking at the size of the impeller and the size of the outlet the volume or pressure would be low
Ian

[cobbadog]

Now I'm confused as I know very little about pumps but I am about to learn something here. Teds original message says that 'each suction' (meaning 2 inlets I guess) and a 6" delivery (outlet). Ian has just stated 'it is a centrifugal pump and the inlet has to be in the centre'
So do we have twin inlets or twin outlets?

[rustyengines]

So do we have twin inlets or twin outlets?

TWIN INLETS YES

 ONE OUTLET YES

Each suction is 5 inches diameter, the delivery is 6 inches diameter.
Each (TWIN OR TWO) suction is 5 inches diameter, the delivery (ONE) is 6 inches diameter.

Ian

[Teddy]

Good evening all
Going through the replies (and I thank you all for your interest):
Scott, no arrows on the pump, and of course no maker's name or other ID.

I'm totally with Ian on this. The volute (casing) shows you the direction of flow, by its design.  Centrifugal pumps draw the fluid in through the centre of the impeller and fling it out. It just won't work the other way.

My gut feeling is a high volume low head (i.e. low pressure) pump.

Based on all the foregoing, we have twin inlets. But, its a point to ask about, once again I've not come across before- normally a centrifugal pump has (by example) a 2 inch suction and an  1 1/2 inch delivery, or a 1 inch suction and a 3/4 inch delivery. This pump  goes the other way and has a bigger delivery than suction. But of course, two 5 inch suctions will bring more than a 6 inch delivery outlet can handle, so I suppose it is "normal" in that regard.

And John, (Cobba) the two suctions are aligned with the centre of the impeller, the shaft goes through glands to lubricate and prevent air being sucked in, and then drive the impeller, which is central to the two suction lines.

Finally, the impeller itself is about 2 inches across, but has a casting down the centre, so that each suction is independent of the other.

I'm not a mechanical or hydraulics engineer, but have been working with pumps (hands on) for nigh on 50 years ( I didn't
 believe myself when I worked it out (LOL)), and this one is unique. Well so far, anyway.

Thanks again
Teddy

[Scott]

Hello all
Thanks so much for the explanations chaps.
It's snippets of information (just like above) that let me learn from people with experience. I for one, appreciate the effort people take to explain things and I thank them for that.

Cheers Scott 

[cobbadog]

Thanks for the explanation Ian and Teddy. It now sits better in my small brain than it did before. I'm with Scott when we learn from others, thanks again.

[Teddy]

Scott and Cobba, thank you for your kind remarks.
You've got me wound up now, look out!!

Just a couple of (final?) comments.
I guess it's stating the bleeding obvious, but centrifugal pumps are called that because it is that good old centrifugal force that flings the fluid out from the centre of the impeller to the outer edge, and then out of the casing (volute) through the discharge.

I made a comment earlier about the glands having a tapping to allow flushing when used for pumping gritty liquids. Normally, pumps with packed glands have them set to allow a very small flow of liquid though them, running from the casing along the shaft to the housing and open air. This trickle keeps the shaft both lubricated and cool, and reduces wear. Many people see this "leak" and tighten the gland to stop the "leak". This is incorrect.

However, If the glands are allowed to become too 'loose" and a strong flow of water is coming along the shaft, then the glands must be taken up to reduce the flow. This is because, on startup, the pump may suck air along the shaft past the loose glands, thus making the pump difficult or impossible to prime.

When pumping gritty liquids, the flow of gritty water past the gland will quickly cut out the gland packing and wear the shaft. So, for example, when sucking sand in channel dredging (for shipping) a supply of clean water is delivered to the tapping on the gland housing, thus providing a clean lubricating flow instead of the gritty material being pumped.

Here endeth the lesson from the silly old blighter, but I hope it may be of assistance to someone just starting out.

Happy Easter

Teddy
PS These comments are about centrifugal pumps, other pumps-other problems! T.

[jopeter]

Ted another chapter to your lesson is Atmospheric  pressure ,ie the vacuum when the centrifugal force throws the water out .It is impossible to get a centrifugal pump to work if it has a badly leaking gland,ie no vacuum.
On your pump with two inlets ......could it be for suction from two sources , perhaps two tanks ,one a reserve tank say in the case of boiler feed .However your pump does not look like a boiler feed pump. It may well be a pump for some process that requires a back up source .
I have a small five stage centrifugal pump ,Siemens & Hirch , must do something with it one day!