Mid-Winter, maybe cold, miserable but not wet! Who has stolen all our rain?? According to the Met Office, this January has been one of the driest on record. However, as we are blessed with having a Variable Speed Drive at the heart of our installation, we continue to generate power—albeit on some days only enough to boil a kettle of water—which we don’t have! So, another milestone was achieved – 90MWh generated.
A snapshot of the end of Jan key data is shown below:
The generating break in the early hours of the morning was caused by a low water level trigger. As a reminder we must retain a cosmetic flow of 6 cm of water over the Weir, if we drop below this level for more than a few minutes we stop generating. This of course has the effect of increasing the weir level and generating restarts (with an overshoot to start). On the above snapshot, we only had one low water level break but on some days in January, these were happening on a quite frequent basis.
One of the visual impacts of low levels is a reduction in the volume of water feeding Archie and therefore the speed is reduced (but we continue to generate). This sometimes causes water turbulence and water splashing out of the vanes into the side channels. Some observant people like Dave, noticed this and were worried that Archie was broken! who sent us this email:
I went past the Havannah Weir yesterday. Although the site is not really visible from the road it seemed there may be a problem. I could see that there were spurts of water coming out the side of the Archimedes screw on the right-hand side as you look from the road and about halfway down the length of the screw.
I do hope it isn’t damaged.
We welcome feedback on any aspect of the Hydro and especially its operation and we do try to respond promptly. You may be interested in our feedback to Dave, shown below:
Thanks for your note.
You are observant!!
Yes, there are spurts of water “erupting!!” from the Archimedes Screw but No, it is not broken!
The geometry of the screw is designed for an optimum speed of 30rpm and when operating at (or somewhere near this speed) there is very little overspill of water.
However, Congleton Hydro uses a Control System with a variable speed AC drive at its core. This means that we can continue to generate electrical energy at very low river water levels (providing we maintain the agreed cosmetic level of 6 cm flow over the Weir head.
One of the “negative consequences” of this, is at very low operating screw rotations we do get water splashing/turbulence rather than a more laminar/smooth transit of the water down the screw. Whilst visually it looks like water wastage, in reality we lose very little electrical power generated.
Hope this gives you confidence that Archie is alive and well—although a drop of rain would be useful to satisfy his appetite.
Thanks again for your interest and getting in touch with us,
Now we’ve been successfully generating for approx. four months (and on broad target with the business plan), it would be nice to put our feet up and relax for a while—no such luck, Archie and all that surrounds him, needs regular maintenance and sometime unplanned maintenance. A flavour of what need doing can be seen from the headline columns of the maintenance logs shown below (Each activity has a detailed process associated with it and where necessary training is undertaken). Some of the activities are just an inspection and no adjustment/repair/cleaning activity is needed until required—just like your car really.
However, some activities e.g., Upper Bearing greasing must be done every month and to do this, we must power down the system—this is a nuisance but does allow us to safely have a more detailed inspection of other parts of the system e.g., silt build up in forebay tank.
A key regular task (at least three times a week but checked daily) is the raking out of the debris (twigs, branches, tree trunks, leaves and all other sorts of debris, but thankfully no dead sheep yet!!) from the trash rack in the water intake. A great team of volunteers, on a rota basis handle this task and do a great job.
A couple of them are shown below, fully kitted up with life-preserver and safety harness.
The observant amongst you might have noticed that a three-month activity is a check on the state of the high-speed coupling—this couples the output of the gearbox to the generator. On a visual check, we noticed what we thought was brake dust (just like the brake disc pads on your car gradually wearing) coating the baseplate of the brake unit. Thought no more of it until we decided that the colour of the dust did not seem correct—it was black not grey! The investigation then pointed us to the high-speed coupling. This is a “Eupex Coupling “, essentially two chunky metal units, one half fitted to the gearbox output, the other half fitted to the generator shaft. The two “coupled together” by interlocking machined keyways, shock absorbed by special “rubber inserts”. The “black dust” was essentially these rubber inserts starting to disintegrate. Really worrying, but why? Looking closely, we could see that the two halves of the coupling were at least 5mm out of alignment—way, way out of spec, root cause the very large generator bolts that secure the generator to the baseplate were not tight (an understatement –they were rather loose!!) This had caused the generator to slightly shift its alignment and screw up the integrity of the coupling.
Generator Securing Bolt System
Why these had come loose is a bit of a worry, we hope (fingers crossed) that we did not adequately torque them down during installation— (a good learning point that we should have known, once something is torqued correctly, mark it !!!—we did not do this). Over the past weeks, we constantly check –no movement against our now present markings, so hopefully now secure for the future.
So, 99.9% sure this was the root cause of the movement and start of the disintegration of the high-speed coupling. We ordered a new set of rubber inserts (approx. £60) and they arrived in a couple of days. Being responsible Engineers! we read the manual and watched the repair process video, and all seemed to be straightforward. The video showing the repair process was very informative, 5mins 20 secs from start to finish i.e., slide coupling halves apart, remove “knackered” rubbers (good descriptive engineering term) and replace with the new ones. Tighten two halves back together and hey presto, press the Start button and begin generating. Being prudent, we thought that maybe as this was the first time, we would allow one hour instead of 5min 20secs!!
Two days later we finally managed to get the system back together! In the video, the “technician” is wearing a spotless pair of white gloves and just uses a screwdriver and spanner. We had to use massive crowbars, baulks of wood and a large sledgehammer. The moral of this story for manufacturers/designers etc is to write and illustrate your repair manuals for the real world and then come to try them out on a hostile Customer (a friendly one would allow them to get away with murder!!), under “operating working conditions” as opposed to brand new units on a lab bench. The photos below show the coupling, “old and new” rubbers and “them” and “Us”.
We will need to strip the system down again, as after two days, we had had enough and left the final “dead-on” alignment for another day—to do this we will have to grind out and elongate the generator mounting holes to give us more latitude of adjustment
The High-Speed Coupling separated into its two halves minus the rubber inserts
Snip from the Repair Video —-dead easy, not a mark on the white gloves!!
Paul started clean, full of hope and optimism. After two days with a sledgehammer, despair starts to set in!!, check google, there must be an easier way—-Oh, the joys of maintaining Congleton Hydro!!
No doubt future newsletters will contain the good, the bad and ugly of further maintenance forays (e.g. why does the upper screw bearing purge at least twice as much grease as we put in every month!!, Landustrie says this is normal and don’t worry—but we do worry, as at this rate the bearing will eventually be empty of grease!!) .
Previous newsletters have touched on the subject of Interpretation Boards that the Education Team Volunteers have been planning, researching, and designing. After many iterations, these have now been manufactured and were installed last week (Feb 4th).
The rather smart Oak Cased board at the entrance is shown below, together with a couple of the other boards.
Each board contains a “QR” code, easily accessed by the QR reader app on mobile phones. This will then “transport” the user to our website which will eventually contain a wealth of detail on the topic and links to other sources of information and learning. These web pages are in the initial stages of development, and we hope to start populating the website during the coming months.
These Interpretation Boards of course are designed to be a valuable aid to those undertaking a visit/tour of the Hydro System. We are very mindful of the fact that we keep on promising to get these tours organised (via a booking system on the website) but for a variety of genuine reasons we keep on failing to do this. Now the boards are installed, and the weather (hopefully) will start to become more benign we can get our act together and hopefully start to get organised in time for tours to start around Easter.
This newsletter started with a comment that this January has been one of the driest days on record, with low river levels consequently frustrating Archie’s ability to gyrate at high speed. Well, this weekend (Feb 5th) has made up for it and the river is in full flood (of course we hate a lot of water as this means we have a reduced “head of water” which also restricts power generation). The River Dane is one of the highest Spate Rivers in the UK.
Literally, overnight the water level can increase sometimes by well over a Metre—and then 24hours later drop back down again. More, information on spate rivers can be found HERE.When you access this, click on “River Levels by name”, scroll down to River Dane, click on link and you will be able to access live data from the gauging stations e.g. Congleton Park together with the historic “high and low “levels.
We’ll end this newsletter with some more key operating data taken this evening (feb 6th)
What a difference a drop of rain makes!!
As with previous newsletters, we hope you have found this one to be of interest and hopefully informative. We do value your feedback and suggestions. Please contact us via firstname.lastname@example.org
|PS. Stop Press! 100 and still Batting!!!|