Whaley Bridge pumps...

[Steve Walker]

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

SteveW

[Chris Hogg]

On Sun, 04 Aug 2019 21:11:12 +0100 (BST), "Dave Liquorice" [e-mail] wrote:>

You'd only need an air-inlet valve at the highest point of the syphon, that could be opened to break the syphonic action.

[Chris Hogg]

A chap on radio 4 this AM has just said that if you de-water too fast, you can get problems on the upstream side of the dam as the pressure on it is reduced.

[Harry Bloomfield, Esq.]

newshound explained :

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.

[Chris Green]

Is there a size of pipe above which a syphon won't work because the water empties out of the down pipe without 'sucking' the water above down? It works well with small pipe because, I assume, surface tension helps to prevent the water from 'dropping out'.

[Harry Bloomfield, Esq.]

NY was thinking very hard :

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

[Martin Brown]

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

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.

[Harry Bloomfield, Esq.]

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.

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.

[Harry Bloomfield, Esq.]

Chris Green formulated the question :

Correct!

Air has to be prevented from being sucked up the discharge pipe, by having the discharge under water, or the syphon will be immediately lost with a larger pipe.

[nightjar]

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.

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

[news19k]

An interesting discussion here:

"The height limit of a siphon"

A. Boatwright, S. Hughes. J. Barry

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

#Paul

[nightjar]

You can see some of the outlet pipes emptying onto the concrete spillway, on the opposite side from the failure. Other pictures seem to show more outlets running straight into a waterway.

[The Natural Philosopher]

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

[NY]

I may have missed something in the earlier new reports, but why are they having to *pump* water out of the reservoir? Is there a problem with taking water out in the normal way? I think it's a canal feeder reservoir. Can the canals not cope with a greater flow of water into them than was originally intended? Are the water courses that the pumps drain into separate from the canal network - is the canal not also fed from them and the spillway?

I don't understand about blocking the streams that feed into the reservoir? Won't water just build up behind the temporary "dams" that the Chinooks are making, causing them to burst catastrophically at some stage in the future?

[Martin Brown]

Canals are designed to lose as little water as possible with each lock movement so they cannot be used to dump water into without seriously damaging the mechanisms. There is usually a small bypass for any excess.

The natural rivers that drain that area. Snag is you can't dump too much into them quickly either without consequential flood damage downstream. They have to balance competing risks.

It buys a bit of time and the trapped water may well soak away more slowly rather than overtopping the barriers. One trick they have been using for a while it to put multiple small barriers into high moor becks to slow the rate it runs off the top in a massive deluge. Mainly to slow erosion but also to alleviate flooding in some places.

[Mike Clarke]

Canals weren't designed to carry a significant flow of water.

They're a series of long thin "lakes" connected by locks where there's a change in level. Every time a boat passes through a lock a lock's worth of water escapes from the higher section to the lower one. Apart from that there's very little flow.

[newshound]

Presumably a non-urgent job?

[Marland]

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.

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]

How far away is the nearest lager plant.

GH

[tony sayer]

It sez that Jeremy Corbyn was there yesterday so brewery piss up organise all adds up;!...