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Post by thefodenman on Apr 22, 2007 13:47:51 GMT
Hello everyone, Its nearly the start of another steam rally season hurray!!. Thoughts turn to getting my 3" scale Foden wagon ready to go once more. I feel after 20yrs rallying perhaps the time has come to descale the boiler? (horizontal locomotive type ) as it doesn't blow down as easily as it used to  . But what to use?, I once tried 'kettle descaler' but I didn't feel it was very successful  . I wondered about 'citric acid' as this is fairly mild, the wife suggests 'lemon juice, bicarb and white vinegar', what does the team think to that idea?. No rude jokes about wives!. So any positive suggestions from the collective workshops out there will be gratefully received . I'm sure some of you will have successfully descaled your boiler. Cheers Andy  |
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Post by havoc on Apr 22, 2007 14:49:30 GMT
Citric acid is used for descaling hot water boilers in house and for coffee makers. Vinager can also be used but it smells...
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Post by ron on Apr 22, 2007 15:59:46 GMT
I used dilute sulphuric acid very successfully on a badly scaled Stuart Turner copper boiler.
Ron
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waggy
Statesman
Posts: 744
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Post by waggy on Apr 22, 2007 17:01:51 GMT
Andy,
In the good old days of BR, we used Sulphamic acid to descale catering car boilers. It is supplied in powder / chrystal form. The diluted strength needs to be approx 20%. I can't remember what was used to neutralise the mix prior to disposal. Have a look on the net for COSSH sheets and suppliers, there are a couple out there.
Waggy.
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Post by alanstepney on Apr 22, 2007 20:02:13 GMT
Much / most of the crud in the boiler will be alkali, so any acid will work.
I have used suphuric (diluted of course) but acetic is often easier to obtain and slightly "milder".
If it is badly furred up, then two or three applications, with a good wash through with water in between.
A good, but careful, scrape around anything that you can reach through any orifices will help loosen it too.
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Post by alanstepney on Apr 22, 2007 20:07:09 GMT
Posted sperately, deliberately.
The clean out after de-scaling is most important. Leave any residue of cleaner in and it will probably prime.
Also, bits of scale will find there way everywhere, especially where you dont want them. Clacks, injectors, safety valves for example.
Best to remove them all first, but beware of odd bits left which will surely find their way out, via the worst (for you) possible route.
Then, will you coat the inside of the boiler?
DM was, probably still is, the best for a steel boiler.
Most of the preserved railways use that or a similar mixture, and can often be persuaded to part with a small amount for a nominal contribution to their funds.
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jackrae
Elder Statesman
Posts: 1,333
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Post by jackrae on Apr 22, 2007 20:30:35 GMT
Excuse the question but if the only problem you have is blowing down, what makes you think iit's scaled up. If it steams OK and produces as well as it did when it was new then it probably isn't scaled on the basis that the heat transfer rate is still good. Perhaps your blow-down is simply blocked with sludge in which case removing it and using a bit of mechanical tickling with a soft steel wire (florists wire) might do the trick.
However having said that and supposing it is scaled then your treatment should be based upoin the boiler metal. You need something which will disolve the scale but not the metal.
If it's steel then you shouldn't be letting sulphuric acid anywhere near it - better to use phosphoric acid as the solvent since this won't attack the steel and will passivate any internal rust spots - but heat transfer rate might drop slightly due to the resultant iron phosphate coating.
If copper then a normal pickling solution of sulphuric or citric should suffice.
Whatever solvent you use the chemical reaction will produce small gas bubbles which will indicate the effectiveness of the process. You may have to replace it with fresh solvent until such time as a fresh charge produces no more gas. Warming the solvent will also speed the reaction.
Jack
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Post by steammadman on Apr 22, 2007 21:02:18 GMT
use WHITE vinegar, strip your boiler of ALL valves etc, bung all the holes with corks, wine bottle type, fill boiler with vinegar , leave overnight, and then give it a good washing out,i usually take just 2 corks out and then stick the nozzle of the pressure washer in , then repeat the whole process a couple of times, but taking 2 diferent corks out, usually that leaves mine nice and clean.
(white vinegar is much better than malt vinegar,i get mine from asda.)
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Post by Shawki Shlemon on Apr 23, 2007 9:04:48 GMT
May be my reply is not 100% related to the topic but is related . I always pour halve a glass of white vinegar in my tender or tank every steaming to keep my copper boilers clean .Does it work ? I don't know but so far I had no problems .
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Post by thefodenman on Apr 23, 2007 10:48:40 GMT
Sorry everybody,
I should have put in the original post, the boiler is copper and the blow down valve is clear, I checked that first by removing the screw, I did of course wait for the pressure to reduce before removing it, Safety first as always!.
Sorry to appear thick but as some of the attached clack valves are difficult to reach/ remove, why do I need to take them off? or is it that the clack balls will be marked by the acid ?
thanks for all the messages so far,
Andy
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Post by steammadman on Apr 23, 2007 21:19:14 GMT
yer makes yer choice yer taes yer chances ! ! ! ! !
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Post by spurley on Apr 24, 2007 7:15:54 GMT
Hi Andy
I think the point about removing fittings is to ensure that no scale or contamination is trapped in them during and after the process and, of course, the potential for damage to them during the descale itself. If it's been 20 years since build I would suggest that it would be a good time to inspect these fittings anyway?
I have always found that white vinegar, slightly warmed whilst soaking, is hard to beat for descaling. You will find that several fills may e necessary before all te scale is removed. It is important to wash the boiler out thoroughly before it's first steaming otherwise you may experience 'foaming' and/or priming when in steam.
Cheers
Brian
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Post by stantheman on Apr 24, 2007 7:38:23 GMT
Maybe a bit 'tongue in cheek' but some years ago I inadvertantly overturned a nearly full can of 'Fosters' into my tender without realising it, certainly did something towards de-scaling mine! Lemon juice is a good bet, gentle but effective if left to work over a fairly good time, without the risk of eating too much away if still trapped in small places due to poor flushing.
Stan.
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Post by spurley on Apr 24, 2007 7:52:36 GMT
Nice to know there is a use for Foster's then  Since they abandoned the Oval! Cheers Brian |
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Noddy
Statesman
Posts: 672
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Post by Noddy on Apr 24, 2007 9:58:49 GMT
a few thoughts.
Sulphuric is probably not the best acid to use, as calcium sulphate (gypsum / plaster of paris) is pretty insoluble.
Phosphoric acid would be a very poor choice as calcium hydroxy phosphate is the mineral our teeth and bones are made of. It is much less soluble than calcium sulphate.
Adding Bicarb to an acid mix may give a nice fizz and the illusion of activity, but all you are doing is neutralizing the acid with an alkali. putting bicarbonates into a copper boiler will also encourage verdigris (green copper carbonate to form)
Citric acid is probably your best bet, as it is safe to use and dispose of.
Vinnegar, apart from smell is also good. Actually, the smell will let you know when you have to do more flushing out to get rid of the last traces of acid.
Of the strong acids, hydrochloric would work, and it would also increase the solubility of any calcium sulphate present, but it will corrode everything and any steel parts will rust for ever more
All nitrates are soluble in water, so in theory nitric would work, but you are unlikely to be able to get hold of it, and it is probably a bit too active to use on your boiler.
It’s a digression, I know, but ammonia is a fantastic copper solvent and being alkaline will do nothing to the scale... don’t be tempted, it is great on greasy floors, but will eat copper.
as for Australian p**s, sorry, lager. it makes the copper and brass fittings on the urinal go green...
Just a thought on future prevention. I live in an old stone house and with the wet winter, I get about a gallon a day of distilled water from my de humidifyers. no scale forming minerals in that stuff...
Keith
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Post by thefodenman on Apr 27, 2007 12:53:18 GMT
Hello everyone, Spurley is right about inspecting fittings. Last year I had a injector clack valve (brought from a reputable source) this had been on the wagon for a number of years, 10+ at least, It looked like it had a minute leak around the body. So I decided to change it. To my horror when I tried to remove it, the body of the valve parted company from the threaded part! It appeared to have corroded or some electrolytic process had perished it. So fittings do age and don't last for ever, its worth checking them periodically, good advice Spurley I agree Andy |
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Post by Shawki Shlemon on Apr 27, 2007 12:59:25 GMT
Specially if they are brass .
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. But what to use?, I once tried 'kettle descaler' but I didn't feel it was very successful 
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Since they abandoned the Oval!