Accident at Russia's Biggest Hydroelectric -Heavy waterhammer 3

[LSThill]

Accident at Russia's Biggest Hydroelectric -Heavy waterhammer in the spiral case and penstock, causing their collapse

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http://www.dailymail.co.uk/news/wor...electric-plant-leaves-seven-workers-dead.html

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http://www.newsdaily.com/stories/tre57h1qb-us-russia-dam/

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http://news.bbc.co.uk/2/hi/europe/8204860.stm

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http://englishrussia.com/?p=4853

? http://

http://www.1tv.ru

Additional detail from Euler Cruz,Consulting Engineer – Turbines,Rafael Cesário,Mechanical Engineer,Brasil – 2009 Aug 24,



L S THILL

 

[BigInch]

There's a few more believers now.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[cvg]

check out the attached powerpoint

 

[ginsoakedboy]

BigInch, What do you mean by your statement?

 

[BigInch]

The general lack of attention paid to waterhammer primarily due to the belief that velocities less than around 10 to 15 fps are perfectly safe. Flow velocity is only half the problem. Accelaration or decelleration is the other half. A mass moving at 5 fps decellerated over 30 seconds may not result in much force. A mass moving at 5 fps, decelarated in 1 second can result in relatively quite a lot of force.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[jmw]

Plus, the greater the mass, the greater the problem.
Take large enough or long enough (or both) pipe and you have the mass equivalent of a car, or a truck moving at speed and you try and stop it in a split second with a fast closing valve.... what you get is a lot of energy to split pipes, destroy valves and pumps .... or worse.

In this case, how much mass? moving how fast? and trying to stop how quickly?

What happens when the flow goes from large diameter to smaller diameter? Velocity increases, yes but does it make hammer better or worse (the mass rate of flow remains the same?)

Water Hammer is not the only way to destroy things catastrophically.

I recall seeing the pictures of a steam turbine generator plant after a drop (don't ask me how big a drop) of water bulleted into the blades. (These were used by Solartron to show the benefits of Hydratec, a water detection system similar to their boiler drum level system Hydrastep. Impressive.) The turbine, suddenly unbalanced, destroyed itself and its surroundings.

I guess there is some of that here too, the energy stored in the suddenly unbalanced spinning turbines adding to the destruction.


JMW

http://www.ViscoAnalyser.com

 

[sailoday28]

BigInch A mass moving at 5 fps decellerated over 30 seconds may not result in much force??
Check your water hammer equations. Distance has a significant impact on severity of water hammer.
Consider 5fps with a downstream valve 1200 ft away, closing
in less than 0.4 seconds (assuming sound velocity 3000 fps)
will cause approx 60 psi pressure rise at the valve. For same distance a longer closer time will lessen impact of water hammer.
Clearly slower closing time will help, but distance must be considered.

 

[msquared48]

That's what surge tanks are for, and that's why I asked the question in the other thread. There ewas never a mention of any surge tanks in the sustem. But with short, but large penstocks, maybe there was no place to put them.

Mike McCann
MMC Engineering

 

[LSThill]

msquared48 (Structural)

Dose the Design of Hover Dam have any surge tanks (large penstocks)? or other US HYDRO FACILITIES.

 

[msquared48]

Yes. Diablo Dam on the Skagit River in Washington State, a dam I became very familiar with when I worked for Seattle City Light.

The other two dams in the system, Ross and Gorge High do hot have surge tanks.

Mike McCann
MMC Engineering

 

[msquared48]

I do not know if Hoover dam has any surge tanks, but I have never seen any in the project photos.

The surge tank at Diable is a concrete cylinder 50 feet in diameter, allowing for a 50 high foot surge from a single 22 foot diameter pennstock. The top is open to the atmosphere. The powerhouse is about 1/2 mile as the crow flies downstream of the intake at the north abutment of the dam, the gravity section. The dam was completed about 1922.

On second thought, I think that the Gorge High Dam might have a surge tank too, but cannot be sure. This dam was completed in the early 60's, the youngest of the three dams.

The greater the static head, the longer the pennstock (mass of water), and the greater the velocity (Kinetic energy), the more need there is for a surge tank.

Mike McCann
MMC Engineering

 

[msquared48]

A quote from the second article above I believe:

"Shoigu said that a sudden surge in water pressure had burst through one of the turbines and caused the flood. "The main reason for the accident was a hydraulic pressure surge, but the cause of that surge still needs to be investigated," he said."

So, the question now is, what caused the water hammer? It could have been a sudden (automatic) shutdown to cause that kind of overpressure, assuming the structure or turbine had not degraded to the point to fail with a lesser amount of water hammer than designed for (big assumption here I know in the Soviet Era - kind of the least bidder syndrome for government contracts here).

The results will be interesting to say the least. Apparently Russia has infrastructure problems too.

Mike McCann
MMC Engineering

 

[BigInch]

Thank you Sailoday27 for reminding me about ... friction. Its been such a long time since engineering K11.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[itsmoked]

msquared48; Go check the thread in the Electrical Power forum.

They put in new turbine gate controls that had issues. It's thought that a gate came off, gutted everything in its path, and broke most/all of the other control gates.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[msquared48]

Wouldn't you know it.

I shouldn't be surprised that the USSR had control issues. Thanks for the info.

Mike McCann
MMC Engineering

 

[chicopee]

Wouldn't grates in the intakes of penstocks stop logs from entering these turbines? I would understand a piece of wood or bare tree branches getting in but not logs.

 

[msquared48]

I don't think that itsmoked was talking about material getting thru the trashrack at the intake. It sounds to me that there was some other mechanical control surface that broke free further down the line to the turbine(s) and then wreaked havock further downstream. I am not familiar with the nomenclature he uses though of a "turbine control gate". I have to assume though that he is not talking about the vanes. Perhaps some kind of butterfly, slice gate, or ball valve.

Sounds like the failure may have only happended in one turbine system, but affected the other two turbines to either side.

The photos show one penstock feeding each turbine of the 10 to 12 turbines as I count.

Mike McCann
MMC Engineering

 

[itsmoked]

The gates are large vanes that are controlled like venetian blinds. As they are servo controlled to maintain the generator's power input, they are opened and shut slightly.

It's my understanding and experience that they were typically all controlled by a single huge yoke assembly. However lately they have been migrating to individual servos for each vane, all individually fed by communications lines. I think they'd just gone to this and were initially setting up the new control system.

As for the other generators they're HUGE units that have extremely large rotors moving at very large tangential speeds only a few millimeters from their stator assemblies. When the water from the failed unit(s) poured into that space hydraulic forces immediately disassembled them.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[msquared48]

So, I guess you were talking about the vanes.

I thought that these vanes were at the bottom of the turbine assembly, at the end of the main shaft, and at the end of the scroll case, prior to the tailrace shaft. If these are the vanes you describe, the failure of one vane would mushroom, tearing up the other vanes, causing an instantaneous imbalance in the system, instantaneous rotational friction, creating a huge braking force that could literally tear the turbine apart.

In this scenario is your water hammer.

Mike McCann
MMC Engineering

 

[BigInch]

Once the control valve failed, it probably made little difference if there were parts of the valve contained in the flow or not.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/