Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

Tim


--
Please don't feed the trolls

On 04/08/2019 20:04, Tim+ wrote:
Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

Tim


and sook really hard ....

On 04/08/2019 20:04, Tim+ wrote:
Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

I'd hate to have to suck on the end to get it started

Seriously. Yes, I would have thought siphoning from behind the dam, over
the top and down to the bottom would make sense. Even if it wasn't as
effective as pumping, it could surely supplement it.

SteveW

On 04/08/2019 20:16, Steve Walker wrote:
On 04/08/2019 20:04, Tim+ wrote:
Why not syphons?Â* I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

I'd hate to have to suck on the end to get it started

Seriously. Yes, I would have thought siphoning from behind the dam, over
the top and down to the bottom would make sense. Even if it wasn't as
effective as pumping, it could surely supplement it.

SteveW
you can't siphon up more than 32ft


--
There is something fascinating about science. One gets such wholesale
returns of conjecture out of such a trifling investment of fact.

Mark Twain

On 04/08/2019 23:30, The Natural Philosopher wrote:
On 04/08/2019 20:16, Steve Walker wrote:
On 04/08/2019 20:04, Tim+ wrote:
Why not syphons?Â* I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized
bit of
pipe.

I'd hate to have to suck on the end to get it started

Seriously. Yes, I would have thought siphoning from behind the dam,
over the top and down to the bottom would make sense. Even if it
wasn't as effective as pumping, it could surely supplement it.

SteveW
you can't siphon up more than 32ft

Correct, but that's a fair way down that dam.

SteveW

On 04/08/2019 23:30, The Natural Philosopher wrote:
On 04/08/2019 20:16, Steve Walker wrote:
On 04/08/2019 20:04, Tim+ wrote:
Why not syphons?Â* I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized
bit of
pipe.

Pumps can also move a lot more water per unit time than a siphon.

I'd hate to have to suck on the end to get it started

Seriously. Yes, I would have thought siphoning from behind the dam,
over the top and down to the bottom would make sense. Even if it
wasn't as effective as pumping, it could surely supplement it.

SteveW

you can't siphon up more than 32ft

And you would need a pipe on the up side to the top that can stand
having 1 atm of pressure trying to crush it. It could work though to get
the level down to 10m below the level of the spillway.

A pump always ensures positive pressure inside the pipe keeping it open.

--
Regards,
Martin Brown

The Natural Philosopher wrote:
you can't siphon up more than 32ft

An interesting discussion he

"The height limit of a siphon"

A. Boatwright, S. Hughes. J. Barry

Scientific Reports volume 5, Article number: 16790 (2015)

https://www.nature.com/articles/srep16790

#Paul

On 05/08/2019 09:26, wrote:
The Natural Philosopher wrote:
you can't siphon up more than 32ft

An interesting discussion he

"The height limit of a siphon"

A. Boatwright, S. Hughes. J. Barry

Scientific Reports volume 5, Article number: 16790 (2015)

https://www.nature.com/articles/srep16790

#Paul

I am sure that putting the Whaley dam in a vacuum chamber to break the
cavitation limit was seriously considered by the team


--
No Apple devices were knowingly used in the preparation of this post.

The Natural Philosopher wrote:
"The height limit of a siphon"
A. Boatwright, S. Hughes. J. Barry
Scientific Reports volume 5, Article number: 16790 (2015)
https://www.nature.com/articles/srep16790

I am sure that putting the Whaley dam in a vacuum chamber to
break the cavitation limit was seriously considered by the team

Well, that doesn't seem very likely to me; I just thought
some of the background info - from a reputable source -
as to *why* there was (usually) a limit might be interesting.
Still, as usual, I am sure you think you know best.

#Paul

On 04/08/2019 20:04, Tim+ wrote:
Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

Tim


You've already said it: suitably sized.

I don't know how far they need to deliver the water, but the flow rate
is dependent on the frictional losses. The pumped system still recovers
available potential energy. To get the same flow rate from a syphon will
require *much* larger hoses, especially if they are long.

On 04/08/2019 20:17, newshound wrote:
On 04/08/2019 20:04, Tim+ wrote:
Why not syphons?Â* I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

Tim


You've already said it: suitably sized.

I don't know how far they need to deliver the water, but the flow rate
is dependent on the frictional losses. The pumped system still recovers
available potential energy. To get the same flow rate from a syphon will
require *much* larger hoses, especially if they are long.

The videos show them pumping into a nearby river very close to the dam.
Presumably some would only need getting to the bottom of the dam and
would go downhill from there anyway. In either case, the hoses would be
fairly short. Even if it couldn't replace pumping, it surely could
supplement it.

SteveW

newshound explained :
The pumped system still recovers available potential energy.

That energy recovery will be minimal, because the flow in the outlet
pipe usually breaks up, with air filling the top of the pipe, so no
much syphon effect if any. Watch what happens in a flexible/ none rigid
discharge pipe.

On Sun, 4 Aug 2019 20:17:45 +0100, newshound wrote:

I don't know how far they need to deliver the water, but the flow rate
is dependent on the frictional losses. The pumped system still recovers
available potential energy. To get the same flow rate from a syphon will
require *much* larger hoses, especially if they are long.

See, for instance, the syphons on the Thirlmere - Manchester route.
Not much pumping there!

"Tim+" wrote in message
...
Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

I suppose they would still need a pump to "prime" the syphon, and it would
have to remain "in circuit" afterwards, because would be very difficult to
remove safely when there's a lot of water flowing, and an unpowered pump may
significantly reduce the possible flow rate. It also depends on there being
a significant head of water between the inlet point and the point where it
discharges into the spillway after going over the "hump" between reservoir
and spillway.

I wonder whether the power needed to drive the pumps does decrease once
water is flowing and syphon conditions exist, or whether it is substantially
the same no matter if the outlet is at the same level as the input or if the
output is a lot lower than the input.

On 04/08/2019 20:20, NY wrote:
"Tim+" wrote in message
...
Why not syphons?Â* I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

I suppose they would still need a pump to "prime" the syphon, and it
would have to remain "in circuit" afterwards, because would be very
difficult to remove safely when there's a lot of water flowing, and an
unpowered pump may significantly reduce the possible flow rate.

You can start a syphon by placing the whole pipe in the water, letting
it fill, closing a valve on the end, lifting the end over and down and
opening the valve. A job for a mobile crane.

It also
depends on there being a significant head of water between the inlet
point and the point where it discharges into the spillway after going
over the "hump" between reservoir and spillway.

If the outlet were placed at the bottom of the dam, there would be a
decent head until the reservoir was virtually empty.

Even if the flow were not as great as with the pumps, more syphons could
be used or they could be just used to supplement the pumps and drain the
reservoir faster.

I wonder whether the power needed to drive the pumps does decrease once
water is flowing and syphon conditions exist, or whether it is
substantially the same no matter if the outlet is at the same level as
the input or if the output is a lot lower than the input.

I would presume that the syphon effect would assist the pumps, at least
be reducing the back pressure and counterbalancing frictional effects.

SteveW

On 04/08/2019 20:30, Steve Walker wrote:
On 04/08/2019 20:20, NY wrote:
"Tim+" wrote in message
...

Why not syphons?Â* I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized
bit of
pipe.

I suppose they would still need a pump to "prime" the syphon, and it
would have to remain "in circuit" afterwards, because would be very
difficult to remove safely when there's a lot of water flowing, and an
unpowered pump may significantly reduce the possible flow rate.

You can start a syphon by placing the whole pipe in the water, letting
it fill, closing a valve on the end, lifting the end over and down and
opening the valve. A job for a mobile crane.

You probably don't want to be driving a mobile crane on the top of the dam.

Yes it *could* be done with a Chinook and a lot of men on top of the dam.

In the big scheme of things, fire engines have the pumps and hoses and
experienced staff. A few thousand gallons of diesel is neither here nor
there.

In article ,
newshound scribeth thus
On 04/08/2019 20:30, Steve Walker wrote:
On 04/08/2019 20:20, NY wrote:
"Tim+" wrote in message
...

Why not syphons?* I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized
bit of
pipe.

I suppose they would still need a pump to "prime" the syphon, and it
would have to remain "in circuit" afterwards, because would be very
difficult to remove safely when there's a lot of water flowing, and an
unpowered pump may significantly reduce the possible flow rate.

You can start a syphon by placing the whole pipe in the water, letting
it fill, closing a valve on the end, lifting the end over and down and
opening the valve. A job for a mobile crane.

You probably don't want to be driving a mobile crane on the top of the dam.

Yes it *could* be done with a Chinook and a lot of men on top of the dam.


In the big scheme of things, fire engines have the pumps and hoses and
experienced staff. A few thousand gallons of diesel is neither here nor
there.

And it can only be supposed that the river their pumping into is at or
near capacity?..

--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

On Sunday, 4 August 2019 22:42:12 UTC+1, tony sayer wrote:

A lake near here was drained a few years ago for maintenance
of its dam. They used two siphon hoses each about 15cm diameter
and it took about two weeks.

Each hose had a strainer at the sucking end. I don't know how
the siphons were started, but they kept going happily until the
lake was nearly empty.

John

After serious thinking Steve Walker wrote :
If the outlet were placed at the bottom of the dam, there would be a decent
head until the reservoir was virtually empty.

That works with a small pipe where the surface tension helps, but not
in larger pipes of this size.

Theoretical maximum head is 32 feet, practical is much less than that
even trying to pump - you are not so much pumping it up to a pump as
sucking it up to a pump and letting gravity deliver it down the
discharge pipe.

Even if the flow were not as great as with the pumps, more syphons could be
used or they could be just used to supplement the pumps and drain the
reservoir faster.

Both ends of the pipe would need to be under water, or the syphon
effect would be lost immediately as air entered the discharge pipe. The
syphon effect doesn't work quite so well in a large pipe unless both
ends are well submerged.

In article , steve@walker-
family.me.uk says...


You can start a syphon by placing the whole pipe in the water, letting
it fill, closing a valve on the end, lifting the end over and down and
opening the valve. A job for a mobile crane.


Like a Chinook, possibly?

If the outlet were placed at the bottom of the dam, there would be a
decent head until the reservoir was virtually empty.


Sorry - only about 34 feet. Beyond that, you would just create
a vacuum in the pipe as the weight of the water exceeeds the
atmospheric pressure needed to push the water up the pipe.


--

Terry

---
This email has been checked for viruses by AVG.
https://www.avg.com

On 05/08/2019 19:01, Terry Casey wrote:
In article , steve@walker-
family.me.uk says...


You can start a syphon by placing the whole pipe in the water, letting
it fill, closing a valve on the end, lifting the end over and down and
opening the valve. A job for a mobile crane.


Like a Chinook, possibly?

If the outlet were placed at the bottom of the dam, there would be a
decent head until the reservoir was virtually empty.


Sorry - only about 34 feet. Beyond that, you would just create
a vacuum in the pipe as the weight of the water exceeeds the
atmospheric pressure needed to push the water up the pipe.

I was assuming that the depth behind the dam was less than it actually
is. Today's report was that they'd got down to 8m below the top of the
dam, with another 8m to go. I didn't expect it to be quite as deep.

SteveW

"NY" wrote in message
...
"Tim+" wrote in message
...
Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

I suppose they would still need a pump to "prime" the syphon, and it would
have to remain "in circuit" afterwards,

No it wouldnt.

because would be very difficult to remove safely when there's a lot of
water flowing,

No it isnt. Just a couple of quick release valves like those
used with street fire hoses would work fine.; Have one
near the pump that is closed when priming, and another
between the pump and the bottom of the syphon.

Once the syphon is primed, open the valve that
lets the water out of the syphon near the pump,
close the one between the pump and the syphon,
remove the pump.

and an unpowered pump may significantly reduce the possible flow rate.

Thats why its removed, so it can be used to start another syphon.

It also depends on there being a significant head of water between the
inlet point and the point where it discharges into the spillway after
going over the "hump" between reservoir and spillway.

Yes, but by definition any dam has that.

I wonder whether the power needed to drive the pumps does decrease once
water is flowing and syphon conditions exist,

No it doesnt.

or whether it is substantially the same no matter if the outlet is at the
same level as the input or if the output is a lot lower than the input.

Thats correct.

On Mon, 5 Aug 2019 14:30:15 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

I suppose they would still need a pump to "prime" the syphon, and it would
have to remain "in circuit" afterwards,

No

LOL

No

LOL

No

LOL

--
Kerr-Mudd,John addressing senile Rot:
"Auto-contradictor Rod is back! (in the KF)"
MID:

NY was thinking very hard :
I wonder whether the power needed to drive the pumps does decrease once water
is flowing and syphon conditions exist, or whether it is substantially the
same no matter if the outlet is at the same level as the input or if the
output is a lot lower than the input.

The power input required, does reduce dramatically when a syphon effect
begins to operate.

On 04/08/2019 20:04, Tim+ wrote:
Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

Tim



Good luck syphoning at the rate the pumps have been working.

https://www.buxtonadvertiser.co.uk/n...voir-1-9914361

At what level will they be able to check things out as to integrity etc? I
feel sorry for all the probably dead abandoned pets, so I'm just waiting for
the court cases to start.
Brian

--
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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Richard" wrote in message
...
On 04/08/2019 20:04, Tim+ wrote:
Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

Tim



Good luck syphoning at the rate the pumps have been working.

https://www.buxtonadvertiser.co.uk/n...voir-1-9914361

On 04/08/2019 21:16, Brian Gaff wrote:
At what level will they be able to check things out as to integrity etc?

They say it is necessary to bring the water level down eight metres to
bring it below the level of the damage to the dam. That is about one
third of the overall height.

The dam has a long history of problems with leaks and structural
problems and the reservoir has been drained before to carry out
maintenance work.

I
feel sorry for all the probably dead abandoned pets, so I'm just waiting for
the court cases to start.

From the reports, pets are what most people who went back into the area
for their allotted 15 minutes brought out.


--
Colin Bignell

I got dragged into one of these years ago...under the building scotland
act a small dam is a dangerous building believe it or not....I didn't.....

On 04/08/2019 20:04, Tim+ wrote:
Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

You also need an arrangement to start the siphon, which for
the scales under discussion mean a valve or tap at both ends
of the pipe, and a removable cover at the top of the siphon
through which the whole caboodle is filled with water.

On 4 Aug 2019 19:04:59 GMT, Tim+ wrote:

Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive.

The Fire and Rescue service high volume pumps are part of the
national reslience system. Seems there are 51 dotted about the
country to be called upon locally or nationally as required. Each one
is capable of delivering 7,000 litres per minute (enough to meet the
demand of up to three fire engines all running flat out) over several
km of hose. They are floating "sump pumps", the small red boxes in
the water in some of the pictures. Seen reported that 16 of these are
in use. The same pictures also reveal larger yellow pumps, presumably
commercial pumps of even higher capacity.

The coverage of these "technical" details is sadly lacking. Most
people won't have any idea of the size of pipes and speed of flow
that shifting that volume of water requires.

For a syphon, you just need a suitably sized bit of pipe.

And some means of priming it and some means of keeping the inlet
clear enough of the bottom to stop it sucking that up and some means
of shutting it off without needing to reprime. Shutting off if the
outflow starts to cause damage at the discharge point of whatever is
being used to carry the flow starts to flood further down stream due
to local rain.

--
Cheers
Dave.

Dave Liquorice wrote:
On 4 Aug 2019 19:04:59 GMT, Tim+ wrote:

Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive.

The Fire and Rescue service high volume pumps are part of the
national reslience system. Seems there are 51 dotted about the
country to be called upon locally or nationally as required. Each one
is capable of delivering 7,000 litres per minute (enough to meet the
demand of up to three fire engines all running flat out) over several
km of hose. They are floating "sump pumps", the small red boxes in
the water in some of the pictures. Seen reported that 16 of these are
in use. The same pictures also reveal larger yellow pumps, presumably
commercial pumps of even higher capacity.

The coverage of these "technical" details is sadly lacking. Most
people won't have any idea of the size of pipes and speed of flow
that shifting that volume of water requires.

I see under the scheme that you mention our Brigade, Hampshire has deployed
some resources.
They have some pumps in their inventory that are intended for use on ships
in in the ports of the county
which are a type of ejector pump with no moving parts into which high
pressure water is pumped.

I have witnessed some in use on exercise with where they emptied the
ballast tanks of a ship using it,
it seems strange to see water pumped into a space you want to empty of it
but more is removed than is being pumped in by quite a percentage using the
Venturi effect .

They are mentioned in this document around page 46.

https://www.ukfrs.com/sites/default/...Supplies.pd f


The lack of moving parts is a great advantage especially in a ships hold
where floating debris could jam or damage a mechanical one, one of the
pumps uses is to pump water accumulating within a hull from shoreside hoses
deployed on a fire as by the time you bring a fire under control may have
sunk or destabilised the ship.

ICBW but I think at one time the version they used was known as the
Southampton Ejector Pump as it was developed by the brigade in that city
(town at the time) due to the large amount of dock estate they cover.

GH

Marland pretended :
but more is removed than is being pumped in by quite a percentage using the
Venturi effect .

The venturi effect as invented by Dyson.

On 05/08/2019 11:29, Harry Bloomfield wrote:
Marland pretended :
but more is removed than is being pumped in by quite a percentage
using the
Venturi effect .

The venturi effect as invented by Dyson.

Dyson Hoovers - - - poor suckers for poor suckers?

A Henry at £99 is one third of the price of a dyson

On 05/08/2019 11:29, Harry Bloomfield wrote:
Marland pretended :
but more is removed than is being pumped in by quite a percentage
using the
Venturi effect .

The venturi effect as invented by Dyson.

Are you sure he didn't get the idea from Frank Whittles
original jet engine design ?.

Andrew was thinking very hard :
On 05/08/2019 11:29, Harry Bloomfield wrote:
Marland pretended :
but more is removed than is being pumped in by quite a percentage using
the
Venturi effect .

The venturi effect as invented by Dyson.

Are you sure he didn't get the idea from Frank Whittles
original jet engine design ?.

Sorry, I ommited a smiley on the end of my post.

Chris Hogg expressed precisely :
"The Venturi effect is named after Giovanni Battista Venturi
(1746?1822), an Italian physicist"

https://en.wikipedia.org/wiki/Venturi_effect

Correct and my car makes use of it. My suggestion of Dyson was intended
as a joke.

On 05/08/2019 11:29, Harry Bloomfield wrote:
Marland pretended :
but more is removed than is being pumped in by quite a percentage
using the
Venturi effect .

The venturi effect as invented by Dyson.

Yes

Not only didn't he come up with the idea, but industial cyclones had
been in use for decades. I am amazed that he was granted a patent -
there was no novel technology there.

SteveW

On 05/08/2019 11:00, Marland wrote:
Dave Liquorice wrote:
On 4 Aug 2019 19:04:59 GMT, Tim+ wrote:

Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive.

The Fire and Rescue service high volume pumps are part of the
national reslience system. Seems there are 51 dotted about the
country to be called upon locally or nationally as required. Each one
is capable of delivering 7,000 litres per minute (enough to meet the
demand of up to three fire engines all running flat out) over several
km of hose. They are floating "sump pumps", the small red boxes in
the water in some of the pictures. Seen reported that 16 of these are
in use. The same pictures also reveal larger yellow pumps, presumably
commercial pumps of even higher capacity.

The coverage of these "technical" details is sadly lacking. Most
people won't have any idea of the size of pipes and speed of flow
that shifting that volume of water requires.

I see under the scheme that you mention our Brigade, Hampshire has deployed
some resources.
They have some pumps in their inventory that are intended for use on ships
in in the ports of the county
which are a type of ejector pump with no moving parts into which high
pressure water is pumped.

I have witnessed some in use on exercise with where they emptied the
ballast tanks of a ship using it,
it seems strange to see water pumped into a space you want to empty of it
but more is removed than is being pumped in by quite a percentage using the
Venturi effect .

They are mentioned in this document around page 46.

https://www.ukfrs.com/sites/default/...Supplies.pd f


The lack of moving parts is a great advantage especially in a ships hold
where floating debris could jam or damage a mechanical one, one of the
pumps uses is to pump water accumulating within a hull from shoreside hoses
deployed on a fire as by the time you bring a fire under control may have
sunk or destabilised the ship.

They are commonly used in chemical and nuclear plants where you don't
want to have to deal with leaky pump seals, moving parts, etc. and can
have the power source outside the danger area.

SteveW

Yes but its really low pressure and if you want to move a lot at a time
there is no benefit to using a siphon. Incidentally, where ARE they putting
all that water?
Brian

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"Tim+" wrote in message
...
Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

Tim


--
Please don't feed the trolls

"Brian Gaff" wrote in message
...
Yes but its really low pressure and if you want to move a lot at a time
there is no benefit to using a siphon. Incidentally, where ARE they
putting all that water?

Where it would go if the dam had not failed
and it was flowing into the spillway when full.

"Tim+" wrote in message
...
Why not syphons? I mean, pumps use power, quite a lot of it and are
relatively expensive. For a syphon, you just need a suitably sized bit of
pipe.

Tim


--
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