I am working on a project where we 1

[AJB1262]

I am working on a project where we want to pump down a quarry for water supply during times of drought.
The quarry consists of two pits with a dividing wall. The quarry has limited access around the perimeter and we are trying to avoid having multiple large pumps in order to drain the second pit into the first. The first pit is substantially deeper than the second. It appears to me, a siphon would work, but I am not aware of an accepted design procedure that would demonstrate this. I understand this would be an application of the Bernoulli equation. I provided schematic below. We are ultimately pumping the first basin to elevation 173 ft and the draw-down pool for the second basin will be 213 ft. How do I account for losses in the 700+ LF of pipe we are proposing?
If anyone can point me in the right direction it would be much appreciated.

Al

 

[LittleInch]

Ok. Your diagram is in metres but you talk about ft. Which one?

Where is each basin?

Is the green line the ground/pipe profile?

This had nothing to do with bernoulli.

Syphons only work if the high point of the pipe is less than about 7 or 8m higher than your water level before falling to a point lower than the water level you are trying to pump out of.

It looks to me like it might work for a limited time before this is exceeded. Flow in the pipe will be affected by frictional losses. Easy to work out.

But need more data.

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

 

[Artisi]

How about a simple sketch showing relative pond levels, distance etc, pipe lengths, pump location etc. Make it easy for us old guys.

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.)

 

[AJB1262]

Thanks for responding.
All elevations and lengths are in feet. The blue line is top of pipe, green original ground.
Ultimate head at end of discharge (213-173) 40 ft (12m). Head difference between bench and pit 2 final elevation (263-213) 50 ft(15m)
I provided an additional schematic to illustrate the elevation relationships.

 

[btrueblood]

Nope, the siphon will choke (vapor bubble will stop flow) when the top of the pipe is some 20-30 ft. above the water level of the upper pool as LittleInch mentioned. Why the control valve in any case, wouldn't you want the pools to equilibrate to the same level, i.e. leave the pipe/channel open? Why not trench or tunnel the middle bench? If you drew down the lower pool, then one guy with a shovel could start the upper pool draining and erosion would likely do the rest...unless the bench is solid rock, in which case call in a blaster.

 

[AJB1262]

Solid Rock (abandoned quarry), and 50 feet rock removal to equalize at 213 ft elevation. Moving about 50,000 CY. At $40/CY = $2 million. Access is limited to the bench to get drilling equipment for blasting.

My question is how do I show this won't work mathematically to rule this out as an option? We could provide a vacuum pump or an air release to keep the line full of water. Control valve would be used to regulate flow into the first pit.

 

[miningman]

The expression solid rock is one of the most misleading expressions ever imposed on those of us who work with rock. What type of rock is this ??? If the two pits have been developed using explosives , what makes you think the "dividing wall" is not fractured to h*ll ? I suggest a bit of basic hydrology study is called for here before spending any money on a siphon system which may or may not be practical.

 

[LittleInch]

Your key elevations are the high point of the syphon (263 ft asl) and the level of pit 2.

In terms of a calculation you can only persuade the water to climb vertically upwards without using any pumps by reducing the pressure in the pipe below atmospheric pressure which causes flow by the atmospheric pressure pushing the liquid (water) up the pipe.

The lowest pressure you can get at the highest point is the vapour pressure of the liquid (water). at this point the water is boiling.

at ambient temps (say 20C), this is about 3 kPa.

So the maximum lift possible is your atmospheric pressure (say 101 kpa) - VP (3) = 98 kPa.

Translated into metres head is 10 metres (33ft)

In reality a syphon starts to break down when bubbles start appearing in the fluid drawn out by the low pressure and proximity of the vapour pressure.

So you might get to 25ft of lift ( your pond 2 at 238ft), especially if you can a decent vacuum pump at the high point sucking out vapour. Then you just hit the laws of physics and your syphon stops. Then you need a pump at the lower end.

The lower you can get your high point ( even 10 ft would make a big difference) the better so may become a bit more practical to build?

also the bigger the difference in level between pond 2 and pond 1 the more flow you will get. An 8" pipe 200+m long will need a reasonable pressure drop to get flow - I wouldn't bother with a valve - just let the two pits equalize over time.

Or drop a submersible in off the bottom of a floating dock and pump away.

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

 

[AJB1262]

Miningman, its Dolomite. The quarry is no longer in operation and the bench road to the dividing wall is no longer accessible or available. If you could get a drill rig on the dividing wall there maybe a possibility of blasting the rock, leaving the fractured rock in place then let the water equalize between the two pits;However, there is no way to predict or control the flow rate through the fractured rock. Thanks Littleinch for the detailed explanation. That was what I was looking for.

 

[dhengr]

AJB1262:
Is there any chance that you could horizontally drill through the dividing wall, at about elev. 213’, from the bench in pit #2? That way, only the bottom 1/3 if pit #2 would be being drained by a siphoning action, and the siphon would already have been established as the water level went from above elev. 213’ to below that elev. Alternatively, depending upon the lay-of-the-land and elevations, you might run your 8” siphoning piping around either end of the dividing wall. The length of pipe may be increased (thus, greater friction loss), but this might significantly reduce the elev. head ( “In reality a syphon starts to break down when bubbles start appearing in the fluid drawn out by the low pressure and proximity of the vapour pressure.” Per LittleInch, para. 7, 14NOV19, 12:02 ) which is the real killer. Or, it might just be easier to do any excavating, tunneling, blasting, in the dry, out around the end of the dividing wall.

 

[Artisi]

In all this round and round discussion, it would be of interest to know the flowrate.

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.)

 

[Artisi]

AJB1262:
I've looked back over this thread, and while the replies have been helpful, it prompted my previous post, what is the flowrate. I see your problem as one of a
pump logistics - having an idea of the pump size suitable to pump from one pit to another at the flowrate and head is step 1 of the solution in conjunction of the site restraints.
If the second pond is near impossible to access, could electric power be made availability to run an electric pump, either conventional type of a submersible raft mounted pump?
Could the necessary equipment be lifted in by helicopter?
Establish the pump size / configuration / driver requirement and then worry about how, when and why you can get it in place.



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.)