Incoloy Elements Failing in Stainless Steel Tanks

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richie rich Participant Join Date: Apr 2007 Posts: 2	Incoloy Elements Failing in Stainless Steel Tanks 04/20/2007 6:09 AM
	I am at the end of my teather with this "work related issue:" our company has just released solar hot water systems which are comprised of stailess steel tanks (no anode) with a heating element made with incaloy. Now we are experiencing unaceptable failure rates of these heating elements and seniour management seem to think it is related to the rubber seal leaking between the element flange and the tank. We also use these elements in our conventional electric storage tanks which have anodes in them, and virtually no failures. This is why i disagree with the argument that it is caused by moisture seeping past the seal and more to the fact that there must be some sort of " catode/anode" effect with the stainless tank and the incaloy element. It also interests me that every element failure shows the failure spot/rust spot on the left hand electrical connection to the element. It would be most appreciated if someone could shed a different light on the subject. kind regards
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Incaloy elements failing in Stainless steel tanks 04/20/2007 6:18 AM
	Assuming the heated medium is water, what is the pH (acidity), the total dissolved solids [TDS] and the total suspended solids [TSS]? corrosion chart __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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richie rich Participant Join Date: Apr 2007 Posts: 2	#2 In reply to #1 Re: Incaloy elements failing in Stainless steel tanks 04/20/2007 7:24 AM
	Hard to say. these failures are metropolitan wide with no hot spots in one paticular area. if i can answer this in any way by saying that all failures are using water within Australian Drinking Water Standards.
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Yuval Guru Join Date: Feb 2007 Location: Israel Posts: 2968 Good Answers: 24	#7 In reply to #1 Re: Incaloy elements failing in Stainless steel tanks 04/20/2007 11:57 PM
	Slack, salinated water make an electrolyte, provided the tank/electrode act in bimetal fashion. A battery/capacitor formed?
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bhrescobar Guru Join Date: Jan 2007 Location: Porto Alegre - RS - Brazil 30deg01'39.73"S 51deg13'43.45"W Posts: 831 Good Answers: 28	#3 Re: Incaloy elements failing in Stainless steel tanks 04/20/2007 8:12 AM
	You're working with AC power, as a domestic application, right? __________________ Humm... suspicious you are...
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techno Guru Join Date: Jan 2007 Location: Canada Posts: 1024 Good Answers: 40	#4 Re: Incoloy Elements Failing in Stainless Steel Tanks 04/20/2007 10:27 AM
	Water itself is corrosive, An annode on the stainless steel will only protect the stainless steel. The element should be isolated from the stainless steel box. If it is not, a short could develop. The annode will not protect the element. Incaloy is used as a coating for elements to protect it from the corrosive elements of the water and dissolved chemicals. It may be possible that: the manufacturing or installation process is damaging the Incaloy coating in the one spot, or the insulation is damaged due to inadequate packaging or rough handling during transport. __________________ Perfection is a subjective and abstract concept.
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techno Guru Join Date: Jan 2007 Location: Canada Posts: 1024 Good Answers: 40	#5 Re: Incoloy Elements Failing in Stainless Steel Tanks 04/20/2007 10:35 AM
	Sacrificial Annodes require electrical continuity to be effective. __________________ Perfection is a subjective and abstract concept.
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Anonymous Poster	#6 Re: Incoloy Elements Failing in Stainless Steel Tanks 04/20/2007 2:41 PM
	You are * correct, analyse the differences between the 2 systems insomuch as they vary.. and thats where to attack problem. Clue, utility companies use small bias chargers to prevent water & gas pipe failures...the presence of a repeated location...indicates electrical activity. a sacrificial rod may be the easy fix here. Google search marine techniques for dealing with spurious electrical/ionic buildups. Your challenge falls into that category. *"This is why i disagree with the argument that it is caused by moisture seeping past the seal and more to the fact that there must be some sort of " catode/anode" effect with the stainless tank and the incaloy element."
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bhrescobar Guru Join Date: Jan 2007 Location: Porto Alegre - RS - Brazil 30deg01'39.73"S 51deg13'43.45"W Posts: 831 Good Answers: 28	#8 In reply to #6 Re: Incoloy Elements Failing in Stainless Steel Tanks 04/23/2007 7:20 AM
	Yeah, your failures are near the element root just because this is probably the nearest point to the sst walls. Temperature up, and you have a good corrosion accelerator. If contamination os not a problem, a sacrifice anode and a small current rectifier could do you active cathodic protection for (almost) a life. __________________ Humm... suspicious you are...
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Anonymous Poster (1); bhrescobar (2); PWSlack (1); richie rich (1); techno (2); Yuval (1)

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