Duplex boilers (split thread)

[alanstepney]

The following posts are split from the thread:
modeleng.proboards.com/index.cgi?board=general&action=display&thread=4623&page=2

[alanstepney]

SDL wrote:
Re: Brit Progress: TIG Boiler Update
« Reply #23 Yesterday at 10:55pm »

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Yesterday at 7:39pm, marco wrote:My name is Marco (Steam Technology) I wonder what comments I will receive next year when we will be putting on the market Nickel- Duplex and Super Duplex boilers that are already in use in other European countries with the CE stamp.
Our intention is to be innovative and to be of help to people in the model engineering world by introducing new techniques so we are not left behind in technology.
This country was the forerunner in train technology and if we are sceptical about new processes we run the risk of other countries overtaking us.
Any comments or enquiries gratefully received.

Marco
www.steam-technology.co.uk




Have you been able to section any old Superduplex boilers to see the effect of crevice corrosion as the make up water will be very variable?

Steve Larner

[alanstepney]

Marco wrote:

Steve
The super duplex alloy 2507 - uns s 32750 is a super duplex s/s with 25% chromium 4% molybdenum and 7% nickel.
Industries to use: oil and gas - power industry FGD systems - desalination plants - high pressure RO-Plant - sea water piping.
Corrosion resistant: the high chromium and molybdenum conten is resistant to corrosion by organic and inorganic acids like chlorides is not like the 316L s/s which cannot be use in hydrochloric acid due to the risk of localized and uniform corrosion. From february 2010 Australia will start to accept Duplex boilres for the model engineering.
I hope this information help.
Marco

[alanstepney]

ausden wrote:


Yesterday at 11:49pm, marco wrote:Steve
. From february 2010 Australia will start to accept Duplex boilres for the model engineering.
Marco



That statement is 100% incorrect...duplex boiler paper was tabled and that's it at this years convention.....there a a few who would like to push it through, but it sounds very floored and the material seems totally useless when heated to standard miniature boiler temperature as run with Coal in Aus.
There was lengthy conversation on the COALs email group by AMBSC officials who have distanced themselves a long way from this speculation, they looked at because somebody tabled it, but that doesn't mean its approved.
By all means you could have one designed and approved by the local government agency if you can, but no chance with the AMBSC code.

[houstonceng]

Of course the key problem that any purchaser of a S/Steel Boiler will face is Section 3.5 of "The Examination & Testing of Miniture Steam Boilers" (Revised Edition 2008) - aka "The Blue Book". This clearly states:-

"Due to the specific requirements and difficulties associated with the examination of Stainless steel boilers they shll not be tested under this code."

That means no club boiler inspector in a UK ME Club affiliated to the three main Associations/Federations of MES, or the 71/4 Gauge Soc., will be allowed to "touch them". You could, of course, get them professionally tested, but many (if not all) MES would probably refuse to let them run on their track.

Like all innovations in "Safety Critical Areas", only tried and trusted mechanisms can be used. The problem being, how to you get the trials - - - - - - - - - - - - - Catch 22.

[klendo]

From the original thread quote Havoc

"Because insurers have full-time qualified, permanently up-to-date staff and technology for this. While a ME boiler inspector is a knowledgable amateur. The insurer's tester signs for the insurer, not his person: if the boiler fails in the former case the insurer is the first in line (unless they can proof carelessness), in the latter case the boiler tester is the first in line."

Surely if an ameteur is signiong for something which is saftey critical, then isnt it a question of Education? We all never no anything and if we are unsure we always check with someone or some one with a bit more savy.

[klendo]

Houston,

The trouble mainly to do with MES's is ( By the way people im not and do not have an axe to grind I think this is an interesting thread so im not having a go, the fact that people are willing to be a boiler inspector is great and offers a solution to what can be a laborious task )

That alot of members in a MES have faith in what they know i.e what they were brought up with. Technology passes by and many people do not understand it or its benefits as they have no come across it. Therefore assume becuase its different or not what is the norm then its not correct. SS vacuum vessels have been used for years, traditionally in UHV applications been made from Inconel. So whilst I agree that most MES would refuse an engine to run with a SS boiler. the question is why? Reason because the members do not understand the system. I.e its about education and understanding ones proffesion should one choose to be a boiler inspector.

[steam4ian]

G'day all

I have already in the past aired my views anti the concept of Stainless Steel boilers. Duplex Steels (DS) are a slightly different matter because DS supposedly has a higher resistance to chloride attack.

I have suggested, but with no authority, that in Australia any code for DS boilers be issued with a limited tenure so that operating experience can be gained with the boilers but we are not saddled with them forever. This is hardly going to be good news for somebody considering owning a boiler that has only say a five year life.

I believe there is still a lot to be discovered with respect to welding, material surface contamination during manufacture, water treatment and practices of usage. Typically what treatment chemicals can/should be used? Can tap water be used, or should rain water be used, what is a tolerable level of chlorides? Is the boiler laid up between steamings wet packed or dry, how dry? Any fool can ask question.

One would like to hope that ultimately we can get a DS boiler with the life of copper and sheet thickness similar to copper yet costing significantly less than copper. Even better would be copper tubes and firebox for heat conduction with an outer sheel of DS.

Unless we give it a go we will never know.

Regards
Ian

[alanstepney]

I used to be a boiler inspector.
In addition, I have built many boilers, in copper and steel, and have read extensively on the subject of stainless steel in boilers.
I have spoken to several professional boiler inspectors and read all the reports on the subject that I have been able to find.

(Whilst this does not make me an expert on the subject (and I make no such claims) it probably means that I am as well informed as the average model engineer. )

My conclusion is that, at present, I would not consider a boiler, either duplex or stainless steel.
Were I still testing boilers, I would refuse to test any made of those materials.

I am not averse to change, provided that there is a good reason and that the change has some benefit, with no more risk than what is used at present.
At the present time, I am not convinced that those criteria have been met.

[weary]

French model engineers seem to use stainless steel boilers without problems.
Here is a link to a thread on the forum of the primary French National Model Engineering Society on the topic.
If it only gives the first page a search chaudiere inox within the topics will find some suitable recommendations.
www.cav-escarbille.com/forum.htm

[havoc]

I believe there is still a lot to be discovered with respect to welding, material surface contamination during manufacture, water treatment and practices of usage.

Is there really? I mean, if this type of boiler/pressure vessel is already in use for long years in industry, then what is there to be discovered? I think there is a lot of "we (ME's) are so different from real life that anything not invented here or 100 years ago is suspicious and thus cannot be correct". Welding boilers has been done since before WWII but in ME it is cutting edge technology.

French model engineers seem to use stainless steel boilers without problems.

My impression is that boiler regulations in france are somewhat "loose".

[Laurie_B]

In full sized practice,any new design,new materials or changes to existing designs including construction methods would be first referred to one of the leading insurance companies specialising in pressure systems engineering.Once approval had been granted,it would then possible for the manufacturer to proceed,overseen by regular inspections from the insurance companies' surveyors.

This doesn't happen in the model engineering world.There is no accreditted body to properly evaluate these new materials and methods of construction.And (no criticism intended or implied) some,if not most club boiler inspectors are not really in a position to carry out such evaluations,in fact it might be unfair to expect them to do so.So we have the situation that club boiler inspectors are more likely to reject anything with which they are not familiar.

There may be nothing at all wrong with TIG welded copper boilers or the use of non-traditional materials.But how do we know;if there was ever a serious failure of a pressure vessel,maybe resulting in legal proceedings?

[mutley]

Dec 18, 2009 13:17:08 GMT Laurie_B said:

There may be nothing at all wrong with TIG welded copper boilers or the use of non-traditional materials.But how do we know;if there was ever a serious failure of a pressure vessel,maybe resulting in legal proceedings?

The point I was raising in the coper boiler thread and the reason I am asking the questions. As a club boiler inspector I would not be happy testing one. Silver Soldered copper boilers I understand, steel welded boilers I have some experince with and am I familiar with the issues.

Andy

[havoc]

There is no accreditted body to properly evaluate these new materials and methods of construction.And (no criticism intended or implied) some,if not most club boiler inspectors are not really in a position to carry out such evaluations,in fact it might be unfair to expect them to do so.

OK, let us accept that statement. It seems to be -more or less- the majority viewpoint. Then what to make of this:

You could, of course, get them professionally tested, but many (if not all) MES would probably refuse to let them run on their track.

I read this as the club boiler inspector ("not really in a position to carry out such evaluation" per above statement) that actually says that the work of the professional is not to be trusted.

I would think that if a boiler turns up that is professionally certified, then it should be able to run. I understand that a boiler inspector would say "I don't re-qualify it, go back to the professional service for that" and that would perhaps be the best way. But I cannot see any good reason why a professional tested, certified and insured boiler would be forbidden to run.

Wouldn't it be a better idea to have new designs, materials, construction types professionally tested and if after some period they are deemed usefull then rules for them could be made. Do the rules have to be written by ME's or could they be written by real engineers (even if it is for a price)? I can imagine that one or the other society could have a set of rules put together acceptable to all (clubs, insurers and professional builders).

Likewise I cannot really accept the statement that there is no "accredited body that can properly evaluate these new materials and construction methods". If some accredited body can certify Marco's work to whatever standard needed for nuclear pressure vessels, they can certify a model boiler. The issue is do MES accept the certification by an accredited body? And from the statements so far I think they don't.

From all discussions so far I get more and more convinced that the only way forward is to burn all the ME rules concerning boilers and go for full pressure vessel regulations. No discussions anymore. Plain and simple for everyone. Maybe some discussions with accredited bodies could lead to special pricing for us.

[alanstepney]

The situation regarding UK clubs is that their inspectors MUST follow the rules, as per the Book, or else (1) the insurance wont be valid, and (2) they may be personally liable.

To get any significant change in those rules would mean convincing the Insurance companies (who do employ professional engineers) of the need to change, and no doubt they would form their own opinion regarding the risks involved.

There is nothing to prevent any owner employing one of the recognised professional boiler inspectors and getting their own insurance.
Also, there is nothing in the rules of any club that I am aware of,that would preclude an engine so insured from operating on their premises or track.
Obviously they may wish to check that the actual insurance policy concerned covered as much as the actual club policy.

[russell]

Yes, Havoc, boiler regulations here in France are rather loose. We can test our own boilers with one other CAV member as a witness. However, I have not heard of any boiler accidents resulting from this loose regulation.

Regards,
Russell.

[steam4ian]

G'day

Me-a-gen.

the only way forward is to burn all the ME rules concerning boilers

The risk of this is that ultimately only TIG welded copper, or professionally welded steel, mild or duplex, will be allowed. Any opportunity for current amateur practice may then be disallowed. If you want to burn anything get rid of clauses about "established design"; some of LBSC's design methodologies have been shown wanting within this forum.

Most participating in these discussions are either model engineers or wannabees and not into collecting Ready to Run models or shelf ornaments. As a collective we must promote self effort and do all we can to remove any impedances to it.

Regards
Ian

[isc]

I know nothing about boiler testing,but I thought the whole pressure sysyem from boiler to cylinders would come into the test.How come then are stainless superheaters alowed?isc

[steam4ian]

G'day isc.

Consider a warn can of Coke which has been shaken, then open it; or a pressure cooker with pea soup when the relief valve blows, soup everywhere.

Compressed gas stores only the energy of compression. Liguids under pressure and temperature contain both the potential energy of compression and the latent energy of the latent heat. Release the pressure and the water vaporises using the latent heat stored in it making a much greater volume than that caused simply by the compression.

Traditionally pressure pipework has not been pressure tested as a certified component whereas vessels have. Air and steam lines are not pressure tested but vessels and receivers are. Strangely in steam engineering even blow down receivers which are open to the atmosphere are pressure tested and certified.

Regards
Ian

[houstonceng]

It looks like Alan understood what I was gettng at. Most Club members run their models on the Club track under the club's insurance (often WM's). Even if the owner had an S/S boiler professionally tested, the club would, probably, have to refuse to let it run; because it would not be covered by the club's insurance, if that Insurance required all boilers on locos using club tracks to have been tested under the current "Blue Book Rules".

If the owner arranged for his/her own insurance and indemnified the club, I suppose he/she could then run an S/S boilered Loco on club tracks.

Talk of using S/S in pressure vessels in other applications doesn't, necessarily mean they couold be used as we use boilers - ie coal fired. Many may remember the problems encountered by builder who ued a certain type of brazing alloy (supposedly ideal for copper)on copper boilers, only to find it was attacked by the sulpher fumes from the coal fire.

I'm ll in favour of progress, but until the regulations and testing techniques and/or tools are capable of ensuring that S/S is safe, I'd rather see us sticking to copper. In any case, good S/S was (probably still is) dearer than copper and has a worse thermal conductivity, so why would I use S/S ?