Integrated woodburner, solar tubes, oil combi and underground heatstore.

[noelsquibb]

oops 

probably meant pottED plant

then again ....

[KLD]

No, honest  , I meant those green things that would enjoy a bit of extra warmth and reward you with their pleasant (overpowering?) odour  And that without bits ripped off, dryed , roled and burned 
But I gather plant-wise you are not the ultimately deciding institution around your place ? 

Klaus

[noelsquibb]

But I gather plant-wise you are not the ultimately deciding institution around your place ?

depends -   

[KLD]

Were the tracks of the little digger made from aluminium -- now re-used as sacrificial anode 
Klaus

[Stuart]

And i'm wondering about the statue infront of the 360

[noelsquibb]

Were the tracks of the little digger made from aluminium -- now re-used as sacrificial anode 

they should last a while then, as tonights report shows the rate of sacrifice.

Ah Stuart,

the Statue,   how did it end up there ?   

In case you thought this sparkling setup was mine, I regret to tell you that I was at the digger graveyard after parts from the trackless machine and took photos to show an 'expert' what condition the machines were in, prior to purchasing. Good old German engineering in those O&K's.

Doesnt really answer the question though ...

So, Sunday saw the routine of pumping the water out of the insulation layers, topping up the water inside the heatstore and as a special treat, some repairs to the expanding foam that always ends up stuck to the GRP it sits on.

pic 1 shows the three bits of aluminium alloy that are electrically connected to the circuit with the steel radiators and immersed in the gravy.

pic 2  shows the undisturbed skin of what might be magnetite.

[noelsquibb]

As you can see theres still some grime on the aluminium drive sproket and the brake lever is the only piece that looks slightly 'dulled' , so not exactly ripping the metal away.
I do wonder if the chemical pong wasnt a bit less than on previous visits but that could just be olfactory degradation from exposure.

Anyway, as even more expanding foam had separated from the cellotex cover, I cut up some bits of plastic sheet and scattered em round the seating area of the cover and blobbed some replacement foam around. That should make the next cover removal interesting.

pic 3  cover and failed foam seal

pic 4. I noticed the paint that covers the top part of the steel radiator was looking quite lumpy in the zone that is above the water for some of the time. It was possible to move the paint layer by pushing it with my thumb.
Not good then. I guess this is going to be the most chemically active zone with acidic steam at temps up to 75c and plenty of oxygen.

[noelsquibb]

pic 5 - much the same as pic 4 but shows that once the magnetite skin has been knocked down by the hose pipe topping up the store, the liquid in the store is not quite as brown and murky as it was.
Imagination or development of the chemistry ?

pic 6 - shows the water in the sample bottles that I took to Frotlabs a couple of weeks ago is a lot more 'gravyfied' than it was when first removed from the store. So what makes the iron 'come out'  ?

Chemistry eh, if only I had listened ...

[Tombo]

I wonder if it would be worth removing the anodising on the sprocket to increase the cathode surface area?

[daftlad]

I could easily put a few more bits of copper in the backfill around the gravy pit and create a more direct bonding link though.

Yup, worth a try.
The ground does have resistance so if you are leaking to earth (even a little from a computer) then the voltage between the existing earth spike and the pit o gravy could a bit. I have heard of earth spikes being fenced off because if a cow had its front legs near a spike and it's rear legs futher away, current could go through the cow and kill it.
So even a couple of meters of ground could provide a voltage. I guess you would need DC current to strip metal but a simple diode could be created anywhere in the circuit?

I am not sure the effect of putting in an earth electrode near the pit which has more resistance than the current earth? Maybe the additional earth spikes need to be quite good? Or just use the new electrodes near the pit? (get an electrician to help if you do this because the new electrodes will need testing)
Not really sure about that one?

Hopefully you can fix this one by just fixing the leak and replacing the radiators and bonding all the metal! rather than digging the whole thing up?
have fun
ta ta

[noelsquibb]

Tombo,

I chucked in the anodised sprocket because I was thinking it would offer a greater combination of metals for the acidic conditions to work on. If the aluminium looked like it was being sacrificed I would put more of it in.

The right metal to put in is a lump of zinc but that requires some strenuous internet activity and the use of a rather worn piece of plastic. 

Seeing as I've had a couple of weeks proper work, perhaps I could treat myself .....


Daftlad,

You like the electrical approach, others favour the chemical one and the interplay between the two is what I have to consider.

I go a bit weak at the mention of diodes and transistors cos that's a whole nuther subject I ignored at college ( no way will I ever need this Oh, how I wish it was better.....) Actually I think I probably ignored most of what I sat through at college and had to learn it the hard way as its importance eventually became apparent.

So what I want is for you to tell me I need a 6v motorcycle battery charger with the negative connected to the plummin and the positive dangling in the electrolyte via a lump of something suitable. 2 Hours on a Friday and we've put all the metal back on the radiators ... or something along those lines

I like the extra copper in the ground suggestion, mainly cos its easy to do 
Whaddya mean get an electrician 
What test would the new electrodes, err scrap copper pipe, be requiring ?



Desp

if you are still about and not lost in 'chemistry for plummers - volume 8',  my mate Jim didn't say it was chlorides in the water he said it was chlorine in the oxygenated mains water that started things off ( c4p volume 12-appendix 3 )
He even knew what gas I would get ( I forgot what he said it was though )  and described its smell correctly.
He said when I refill, I should use stream water or ground water and also recommended sacrificial zinc.

thanks everyone for all the replies, I'm still learning and loving it.

noel

[knighty]

(from the flow battery thread)

I love chemistry me!

Hi Pontiff,
You could be just the chap Im looking for .....
http://www.navitron.org.uk/forum/index.php/topic,8946.60.html
We seem to be edging towards understanding why my heatstore has battery like qualities ( well this is a thread about batteries )  but Im not exactly sure how I can switch them off.
Any thoughts ?
noel

nole... as above 10% antifrees will stop the electrolosis in your system.... you always get electrolosis with mixed metals in a pumped system...

[noelsquibb]

Cheers Knighty

When the heat exchanger gets lifted out and the pit emptied, so I can address the small leak into the insulation and rebuild the heat exchangers using only one metal ( plus a bit of solder ), I need to be able to dump the contents in the nearby drainage system which then discharges into the duck pond.

Not convinced I want to be putting 140 litres of antifreeze in that direction. 

However, when its rebuilt and the contents look like they are staying in the pit, I am happy to dose with antifreeze, inhibitor and an oil slick to top it all off, plus cross bonded pipework connected to a set of earth rods close to the pit and the most effective sacrificial metal dangling in the gravy.

In the meantime I'm interested in finding out what I have inadvertently concocted and possible ways of stopping or even reversing the metal removal in the hope of getting it to hold together long enough for the ground to dry and heating no longer required.

BTW, the pumped side of the heat delivery circuit has a fair amount of inhibitor in it, so hopefully its not a race to the middle of the steel rad skins but corrosion from outside to inside.

noel

[desperate]

Hi Noel,

 been a bit busy of late, but am still following the tale... to be honest I aint quite sure what the next step is.
When you heated that black "Magnetite" stuff did it impart any kind of colour to the flame? Mind you even if it did, we dont know if it is a pure compound, so that wouldn't be conclusive..........

Zinc...........a freebie source of zinc is old dry cell batteries, carefully cut em up to reveal a carbon rod in some black slimy gloop, all in a......... ZINC can   or rip some Zinc flashing off the local church roof, no I didn't say that
 might be worth a try.

All the best

Desp

[pontiff]

Hello Noelsquibb,
Just finished reading this mammoth thread. It would take me weeks to figure out your plumbing without diagrams but it looks amazing from the pictures.

On the chemistry front I'm afraid I don't have many answers to preventing your radiators from disintegrating slowly.
The reason it's causing such debate is because there is an awful lot of chemistry going on here.

The main problem is that your radiators are acting as giant anodes, the copper as the cathode, all the brown gravy and black deposits are iron compounds in various stages of oxidation, the electrolyte ( water ) will have dissolved calcium and magnesium salts which allows it to conduct. The copper will be fine but the radiators are slowly dissolving.

The different colours of the deposits are caused by the changing concentrations of oxygen. The brown oxides are usually formed first, the black solid is probably lodestone which forms in low oxygen concentrations.

You have made a giant cell which will will have a cell potential of up to 0.6v, depending on the type of steel.

Unfortunately this type of galvanic corrosion is not uniform, it usually causes severe pitting in the steel which is probably the cause of the rad faliure.

In addition, with it being connected to earth via the pipes this will probably speed up the rate of corrosion ( canal boats suffer from this when they are connected to onshore power supplies).

The rads are also rusting in the traditional way due to the presence of oxygen and water, oxygen will dissolve readily at the surface because of the convection currents produced by heating the water. The water would have to be kept constantly near boiling to prevent it dissolving and only tiny amounts are needed for rusting to take place.
The coating of the radiators will be insufficient to stop water penetration, you would have to give them treatment similar to what modern car bodywork has.

Finally, the acidic conditions speed up the rusting process many times ( very little effect on the copper)

The usual solutions for heating systems are to use dielectric couplings to join copper and steel pipes, ensure little /no oxygen is present, and to use additives ( fernox etc). Even so, the water inside a radiator will still darken as iron oxides and hydroxides are formed.

There have been some great suggestions so far to slow down the corrosion, oil on water, adding antifreeze, sacrificial anodes etc. I'm sure they would all work to some extent but as you have a combination of many different factors causing the problem I think the best long term bet is to remove the rads.

I dearly wish there was a simple solution to this as I can see the huge amount of work you have put into your project. On the other hand , a combination of the previous suggestions might slow the corrosion down enough to get a couple more years of use out of the current setup.

p.s the zinc sacrificial electrodes( or you could use magnesium if the water isn't too hard) needs to be attached directly to the steel.