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Electro-Hydraulic control resources

3K views 31 replies 11 participants last post by  Going_Commando 
#1 · (Edited)
Hey guys, the hydroelectric power plant I work at has the hydraulics all jacked up. There have been a few leaks from the hydraulic pump to control the gates, and oil got into the kraut solenoid valves and whatnot, and things are all kinds of screwed up. Anyone know some good resources to read up on how this stuff works? The turbine and control system is all Ossberger, which is a German company (system in its current form was installed in 1985), and all the manuals we have are in German. There is also not a US distributor or parts supplier anymore, so we are basically on our own. I am weak when it comes to hydraulics and need to learn more about it, so any books, websites, what have you that you guys can point me towards would be greatly appreciated. Right now we are running on manual control with the backup hand pump, which is getting f*cking ridiculous. :laughing:

ETA: I am still going through the process of tracing out all the wiring in the control cabinet (the wiring diagrams we have might as well be used to start a campfire), so I will probably have a ton more questions as time goes on. Depending on how long we can keep the German system creeping along, I would like to work towards replacing it with new equipment run from a PLC, but that is down the road a ways.
 
#3 ·
interesting stuff.

while you are figuring this stuff out, try to get your company to fork out for some trips to Packer's games, or maybe to Germany for Oktoberfest later in the year, under the guise of learning the language haha.

lets see some pics of the controls !
 
#5 ·
the 2 biggest weaknesses with hydraulic control systems are leakage and air
cavitation in the hydraulic fluid caused by excessive turbulence can leave air bubbles in the high points in the system and decrease the efficiency of operation.
leakage usually caused by seals wearing out due to heat, contamination, and in some cases seal deterioration from using the wrong fluid type.

if the pressure is jacked up in the system then its either air or an attempt to make it run with the leaking conditions.
over pressure conditions can indeed cause leakage.

all in all hydraulic control systems are reliable and usually have a long life span.

in any event though you have a real mess on your hands to deal with
 
#8 ·
Wish I could get my hands on it, been years since I worked electro-hydraulics. I spent 22 weeks @ 12 hours a day learning it for the navy back in 86.

Change the fluid, filter and flush it out.. Take your time drawing it out and you'll see how easy it is..

I'll look up a book left over from back then to get a company name for training.
 
#10 ·
Big John said:
I've always said electricians were well suited to it. The schematics are similar to control diagrams. Think of pilot pressure as low-voltage.
Back then it was mostly Transistor logic for control of the gun mount. Funny how fast that equipment operated and it was more reliable then the new fangled digital controls that were out.

Control work boiled down to a simple concept, "Every control circuit component was on or off".
 
#12 ·
Generator Cabinet with protective relays:


Breaker to tie generator to grid:


Original generator setup, kept as spare parts for whatever reason, with a rotary exciter behind it:



Ossberger turbine. Horizontal setup, generator is a 600kW with a 1.5 service factor. Don't mind the mess, we just did annual maintenance a little while ago and still haven't cleaned everything up yet :laughing::

 
#14 ·
Honestly, I don't remember. I'd have to read the faceplate of it. :laughing:. I've only been in the plant like 4 or 5 days in the past 6 months. I was doing daily checks for a while, but now I am more of an extra hand, troubleshooter, that type of thing. I haven't done the day to day stuff since before I moved to California, so I am a bit rusty what all the protective relays and such do. I've got my work cut out for me now though, especially since getting this crap working again is going to be a spare time, nights and weekends gig. We also have to rebuild one side of the tailrace this summer, and a bunch of other work, so I am going to be one busy mofo at some point. I might be over there tomorrow, and if I am I will find out what the Basler is for. Reverse power maybe?

Funny thing about that breaker. A few years ago, a mouse made a nest in between the contacts when we were offline for the winter. That spring we got everything going, didn't check the breaker, and it went BANG when we hit the contact close button (manual sync). We ended up ordering all new contacts and such, rebuilt the breaker, and got it going again. Then, while we were doing some cleaning last summer, I asked the bossman what the wooden crate was for next to they hydraulics control cabinet. He said, "I've been here for 15 years, and I don't have a clue." Lo and behold, we pop the top off the crate and it is a brand new Westinghouse breaker. :laughing:
 
#17 · (Edited)
What's the deal with someone manually opening and closing the wicket gates? Someone manned there all the time to adjust them for load changes? That must be inefficient. Then again, that's how they used to do it...

Wait handpump? Wouldn't your frequency on that machine be all over the show? Surely that couldn't be fast enough :S
 
#25 ·
Well **** maybe I was told wrongly then. I was taught that when load comes on, you get a magnetic field in the stator opposing the rotation of the rotor, slowing the rotor down, and thus your frequency would drop as the speed drops. In response to this the governor opens the wicket gates to allow more water to flow which speeds up the generator to maintain frequency (over here 50hz). And vice versa with load coming off, generator would overspeed, governor closes gates. We get pinged really badly for over or under frequency from the station which wouldn't really make sense if the frequency was fixed outside of our control.
 
#26 ·
Let me see if I can work through this. I am a bit tired, but will do my best. So, when we are working to get the generator synced with the grid, we are bringing it up to the exact RPM necessary to generate 60 Hz (167 RPM in this case). When the generator reaches the correct frequency, the breaker is closed and the generator is synced. We then adjust the guide vanes (Ossberger turbines don't use wicket gates, bit different design) to match the power output we want based on river flow. To keep the generator from loading the grid or the grid loading the generator, the excitation current is adjusted via a voltage regulator circuit to keep the correct voltage being induced into the stator. The guide vane acts as a governor, as only so much water volume is going to be passed through the turbine, since the pressure is essentially fixed. Once the generator is synced, the voltage regulator will automatically adjust the excitation current to match what it needs to be based on the position of the guide vanes.

Forgetting to mention the exciter in my explanation before was my bad. I've been working on 2 hours of sleep all day and am a bit loopy. Speaking of that, I need to go to bed so I can get up in 6 hours. :laughing:
 
#30 ·
Big John said:
What's the score there? You've got two layers of voltage protection, are the bottom ones unit protection and the top one is utility?
Not sure. Next time I'm over there I'll dig into it some more and fight out.

So, we have found out part of our problems with the system is that several of the relays in the bottom of the cabinet have bad coils, and they are 1970s vintage. We are planning on just replacing all of them.

Has anyone used the Weg relays from Automation direct? We need 4 pole contactors with 2 NC and 2 NO contacts to replace the old ones, and it seems hard to argue with $13.

We removed all of the solenoid valves on the hydraulic unit, cleaned them up, and replaced all the prints on the unit, so the leaks are finally gone! Once we hit summer shut down we are really going to tear into the controls and flush the hydraulic unit, and also see about getting the variable valve going again. We are also going to see about ripping out the pond level controller and some other parts in the cabinet that aren't necessary. The pond has never had the volume for the pond level control to actually work. It would just bounce between full power and about 50kW. Stupid design.we will most likely add a Plc to operate the variable speed setup and whatnot to clean up the cabinet and allow for easier control.
 
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