Regulator metal

[Garry ColesParticipant @garrycoles69390]

Hi,

I’m starting to fabricate the steam regulator, which will be located inside of the dome on my loco. But I want to use some brass silver soldered parts in place of bronze to make it up. I have lots brass material and not enough bronze bits. Can anybody please tell me if this is okay to use.

Thanks

Garry

[Andrew TinsleyParticipant @andrewtinsley63637]

I understand that brass can “de-zincify” under conditions met with the inside of a boiler. I definitely would not recommend using brass, unless someone knows better!

Andrew

[noel shelleyParticipant @noelshelley55608]

I would have said use the brass, and having looked at the drawings for my butch 0-6-0 which is about 50 years old all the parts for the regulator are of brass so my opinion for what it’s worth is, – use the brass ! I have seen dezincification in marine use of ordinary 70/30 brass where there is an electrolytic fluid but in steam or rain water – you won’t live long enough for it to be a problem ! Good Luck. Noel.

[Garry ColesParticipant @garrycoles69390]

Thanks for the info. I know that gunmetal or PB must be used for boiler fittings that are part of the pressure chamber but I wasn’t sure about other fittings.

Garry

[Paul LousickParticipant @paullousick59116]

Brass is acceptable for fittings attached to the boiler that are removable. (Valves, water column, etc.) If there is a problem they can easily be replaced. Parts permanently attached may be difficult to replace if the brass dezincifies.

[JasonBModerator @jasonb]

It is not so much the pressure but what the part will come into contact with. It is the impurities in the boiling water that attack the zinc content of the brass so if the item only sees steam there should be little risk as the odd bit of priming is unlikely to affect things.

Both my  the Minnie and Fowler specify brass

[SillyOldDufferModerator @sillyoldduffer]

Rather than taking random internet advice, Gary might attempt a quick risk analysis and decide for himself!  Individual circumstances vary wildly, making it unwise to generalise.   What’s OK in Cornwall might be unacceptable in Somerset; the difference between hard and soft-water.   And if the worst happens, a coroner won’t be impressed by Gary explaining his Design Authority was a bunch of chaps on a Model Engineers forum!    Chaps, whom if called, will be strongly advised by their solicitor to say nothing!

The technicalities of dezincification may not matter because the first risk is that a Boiler Inspector might reject Brass fittings outright.  The Inspector’s word is law if the engine is to be run on a club track.   My guess is that because Inspection is related to insurance, an inspector is likely to take a hard-line on Brass, insisting the boiler construction uses none whatever.   Ask him!

On a private track the owner can do his own thing.   He can choose to tolerate or manage dezincification on a scale from “don’t care” to “paranoid fuss-pot”.   Nothing wrong in this I feel, provided the owner isn’t just hoping for the best, and has thought about it.

On the technical side, much depends on the water.   I recommend Gary reading the Corrosionpedia article on dezincifation to decide how many of the risk-factors apply to him, or not!   Edited highlights:

Conditions favoring dezincification are:

Contact with slightly acid or alkaline water
Water with little aeration
Low flow rates of the circulating liquid
Relatively high tube-wall temperatures
Permeable deposits or coatings over the tube surface

And

Elevated temperature and coupling to a more noble metal can increase the dezincification. If brass bosses are used on copper hot water cylinders, the combined effects of the high water temperature and coupling to a large area of copper can give rise to significant dezincification even in waters that normally would not cause problems.

Also think about what could go wrong if the regulator fails.  An explosion must be very unlikely, but a regulator that fails open when the engine is already travelling at speed is a real worry.

On the other hand, hobby engines aren’t steamed much, so time available for dezincification to occur is low.   Might take decades for the problem to appear.   Only Gary knows how often and for how long his engine will be steamed.

Another consideration is how difficult it is to replace a rotten Brass regulator.   Not a problem it’s easy to retrofit a Bronze replacement, but worth considering going straight to Bronze if the change is a lot of extra work.

Dezincification resistant Brass is used to make modern plumbing fittings, but it’s fairly recent and unlikely to be found in a junkbox in usable form.

Dave

[noel shelleyParticipant @noelshelley55608]

Historic evidence is of value, IF dezincification is / was such a problem why is it specified on numerous drawings by well known designers ? How far do you deviate from published drawings in the context of materials before it is no longer built to design and must therefore be treated as a NEW design ? Dezincification resistant brass is NOT a modern innovation having been used for over 50 years and can be easily recast into usable shapes ! Brass bosses in a hot water cylinder that often boiled was over 40 years old when it was removed only because the plumber tore the copper.  My loco has, as specified, a brass regulator body that is over 50 years old and never given trouble. What is theoretically possible and what in practice works can be worlds apart !

To the OPs question, I say again, use the brass. I will speak up for you ! Noel.

[Clive FosterParticipant @clivefoster55965]

When it comes to using brass the immediate question is “Which one?”.

I’m told there are or have been a hundred or more commercially produced versions with some surprising variations in physical and engineering properties. Brass mostly seems to be assessed largely on things like ability to take a nice polish, reasonable corrosion resistance under ordinary conditions and relative ease of accurate machining rather than specific engineering properties. The obvious big exception being the deep drawing varieties used for shell cases et al.

Generally when you need to engineering things governed by performance specifications the bronzes and gunmetals are preferred. How much of that is due to the reliability of more closely controlled mixes in production components that are expected to work and keep working over long periods is an open question.

I’d be a bit chary of expecting dezincification properties to fully transfer if melting components and re-casting as raw material. Brass is known for a certain sensitivity to this type of operation so the properties of the new melt may not fully match the source. Which generally matters not at all providing the parts made from the new material are of sensible size and proportions.

Historical experience isn’t always a good guide. Back in the day materials were chosen more for ease of working with limited equipment rather than performance under edge conditions. “Worked for me” went to “usually works for everybody” then “not heard of any failures” and finally “well one or two broke but its very rare”.

Given the amount of use most things made by model engineers get (or more likely don’t get) “well one or two broke but its very rare” is perfectly acceptable reliability for an individual. Particularly when the risk factors are known and any responsible model engineer will do what is needful to avoid excessive risk in their particular environment.

That sort of thing is far too wishy washy for an insurance company who will have to pay out if something goes blooie in a big way in public. For obvious reasons both the insurance company and us want the risks to be minimal. The higher the risk the bigger the premium. Two approaches.

Either:-  specify a procedure of working that mitigates any potential problems to minimal levels

Or :- specify that materials that might be prone to dezincification and other slowly developing weaknesses are not to be used.

The second being far easier for all concerned. Shades of Mr Musk and “the most reliable component is no component”.

As it is a surprising amount of model engineering safety is already taken on trust “it’s always worked OK” by the insurance companies. So avoiding brass inside boilers seems a minimal concession. The alternative being ever greater encroachment along the lines of the Australian Boiler Code. Which latter seems to be fairly generally agreed to be over-prescriptive in the name of good intentions.

Clive

 

[duncan webster 1Participant @duncanwebster1]

To get dezincification you need liquid water, so anything above the water line could be ok. However, I’ve no idea how much sloshing about there is inside a model boiler, but using brass for regulators is long established. Just don’t use it for bushes or anything else which is permanently part of the boiler.

I’ve actually read the Australian boiler code. With the exception of its dislike of girder crown stays I find it very reasonable, comparing well with my interpretation of UK national standards for pressure vessels. (interpreted to allow for copper which isn’t mentioned). It also agrees well with the various cooking formulae quoted by writers in ME over the years.

[SillyOldDuffer]

On SillyOldDuffer Said:

Rather than taking random internet advice, Gary might attempt a quick risk analysis and decide for himself!  Individual circumstances vary wildly, making it unwise to generalise.   What’s OK in Cornwall might be unacceptable in Somerset; the difference between hard and soft-water.   And if the worst happens, a coroner won’t be impressed by Gary explaining his Design Authority was a bunch of chaps on a Model Engineers forum!    Chaps, whom if called, will be strongly advised by their solicitor to say nothing!

Despite brass being not an ideal material there were thousands of steam toys commercially produced with brass boilers that have not caused widespread death and destruction.  In order for Gary to assess risk he needs to canvass experience and information a specialised ME forum seems an ideal place to me to ask the question. The final decision as design authority is his alone.

 

The technicalities of dezincification may not matter because the first risk is that a Boiler Inspector might reject Brass fittings outright.  The Inspector’s word is law if the engine is to be run on a club track.   My guess is that because Inspection is related to insurance, an inspector is likely to take a hard-line on Brass, insisting the boiler construction uses none whatever.   Ask him!

I would hope / expect an MES boiler tester to question or reject brass in the construction of a boiler shell, tubes or bushes but if he rejects brass fittings such as gauge glasses, clack valves and blow down valves he will outlaw most of the commercial fittings available for purchase which might invoke a difficult conversation with the supplier.

On a private track the owner can do his own thing.   He can choose to tolerate or manage dezincification on a scale from “don’t care” to “paranoid fuss-pot”.   Nothing wrong in this I feel, provided the owner isn’t just hoping for the best, and has thought about it.

On the technical side, much depends on the water.   I recommend Gary reading the Corrosionpedia article on dezincifation to decide how many of the risk-factors apply to him, or not!   Edited highlights:

Conditions favoring dezincification are:

Contact with slightly acid or alkaline water
Water with little aeration
Low flow rates of the circulating liquid
Relatively high tube-wall temperatures
Permeable deposits or coatings over the tube surface

And

Elevated temperature and coupling to a more noble metal can increase the dezincification. If brass bosses are used on copper hot water cylinders, the combined effects of the high water temperature and coupling to a large area of copper can give rise to significant dezincification even in waters that normally would not cause problems.

That article is hardly a credible technical reference, what is the magnitude of elevated or high temperature?  I very much doubt the man in the wig will be impressed if you cited that article as the basis for your material choice alone.

Also think about what could go wrong if the regulator fails.  An explosion must be very unlikely, but a regulator that fails open when the engine is already travelling at speed is a real worry.

Why is that a real worry?  You have a reverser, use it.  Traction engines had no real form of useable brakes, they had a reverser, very effective at holding an engine back down hill when used properly with both pins in.

On the other hand, hobby engines aren’t steamed much, so time available for dezincification to occur is low.   Might take decades for the problem to appear.   Only Gary knows how often and for how long his engine will be steamed.

Only Gary knows also the working pressure (and hence temp), volume etc of his boiler.

Another consideration is how difficult it is to replace a rotten Brass regulator.   Not a problem it’s easy to retrofit a Bronze replacement, but worth considering going straight to Bronze if the change is a lot of extra work.

True, one reason why I made the boiler fittings for my traction engine from bronze, there were over 20 separate parts in the gauge frame alone and I didn’t fancy making them again further down the road – but if I wanted to buy commercial items from the ME suppliers I would have been given brass.  Who knows what grade of brass, they don’t supply material certification when you buy them. Personal informed choice.

Dezincification resistant Brass is used to make modern plumbing fittings, but it’s fairly recent and unlikely to be found in a junkbox in usable form.

Dave

Some reasonable points but very much presented in a sanctimonious, superior and scaremongering manner which I don’t think was particularly helpful.

Paul.

[Paul Kemp]

Paul,

On Paul Kemp Said:

On SillyOldDuffer Said:

Rather than taking random internet advice, Gary might attempt a quick risk analysis and decide for himself!  Individual circumstances vary wildly, making it unwise to generalise. …  And if the worst happens, a coroner won’t be impressed by Gary explaining his Design Authority was a bunch of chaps on a Model Engineers forum!    Chaps, whom if called, will be strongly advised by their solicitor to say nothing!

Despite brass being not an ideal material there were thousands of steam toys commercially produced with brass boilers that have not caused widespread death and destruction.  

Irrelevant to Gary I feel?  Steam toy boilers are tiny, and are unlikely to cause death and destruction in any circumstance!  And they don’t generally last long – most of ’em scrapped after a few years fun.   Not to be compared with Gary’s much more grown up engine.

 

In order for Gary to assess risk he needs to canvass experience and information a specialised ME forum seems an ideal place to me to ask the question.

Not so sure about that!  I’d say the average Model Engineer is strong on practical workshop skills, but weak on theory.   Model Engineers can’t be expected to know about materials, electricity, electronics, maths, chemistry, money, law, insurance, or CAD, or any of the many other technology branches.  Experience is good, but only if up-to-date and relevant.  When someone claims experience, double check!

 

The final decision as design authority is his alone.

Agreed, or it should be!  That’s why I’m advising Gary to do his own risk assessment.  But we have an example in this very topic where a member muddles the boundary,  He asserts ‘I say again, use the brass. I will speak up for you !’  This he will do in a coroners court, presumably not realising that by doing so he is accepting responsibility!   Gary’s defence becomes that the member is responsible because Gary only took the member’s guaranteed advice!

The technicalities of dezincification may not matter because the first risk is that a Boiler Inspector might reject Brass fittings outright.  The Inspector’s word is law if the engine is to be run on a club track.  …   Ask him!

I would hope / expect an MES boiler tester to question or reject brass in the construction of a boiler shell, tubes or bushes but if he rejects brass fittings such as gauge glasses, clack valves and blow down valves he will outlaw most of the commercial fittings available for purchase which might invoke a difficult conversation with the supplier.

I suggest the boiler inspector should be asked about the regulator, not about minor fittings, which as far as I know aren’t controversial.  Gary’s risk simply is that an inspector might reject a Brass regulator.  No need to rely on ME forum advice, just ask the Boiler Inspector.   He’s the responsible expert, not the forum!

I recommend Gary reading the Corrosionpedia article on dezincifation to decide how many of the risk-factors apply to him, or not!   Edited highlights:

Conditions favoring dezincification are:

Contact with slightly acid or alkaline water
Water with little aeration
Low flow rates of the circulating liquid
Relatively high tube-wall temperatures
Permeable deposits or coatings over the tube surface

And

Elevated temperature and coupling to a more noble metal can increase the dezincification. If brass bosses are used on copper hot water cylinders, the combined effects of the high water temperature and coupling to a large area of copper can give rise to significant dezincification even in waters that normally would not cause problems.

That article is hardly a credible technical reference, what is the magnitude of elevated or high temperature?  I very much doubt the man in the wig will be impressed if you cited that article as the basis for your material choice alone.

Other way round Paul.   Gary, or anyone else, would be very unwise to use the Corrosionpedia article as a reason for using Brass!  It lists, fairly accurately, the conditions under which dezincification occurs.   The risk is real, which is why Bronze is preferred.   God forbid a Model Engineer ever ends up in court, but it’s the prosecution who will be asking why the Designer chose to use Brass rather than Bronze in a situation where dezincification might occur.

Also think about what could go wrong if the regulator fails.  An explosion must be very unlikely, but a regulator that fails open when the engine is already travelling at speed is a real worry.

Why is that a real worry?  …

Maybe it’s not.  Risk assessment has 3 parts:

1. Identify the risk and how likely it is or not to happen
2. Identify the impact if it does happen
3. Decide what to do about it, if anything.   A risk with low probability and impact can be tolerated.  A high probability risk with high impact requires positive action.   Many in the middle risks can be mitigated or managed.   On a private track, training the driver to use the reverser might well be an acceptable strategy.  More dubious if the engine hauls the public, because the impact of public accident is much higher than a back-garden mishap.

On the other hand, hobby engines aren’t steamed much, so time available for dezincification to occur is low.   Might take decades for the problem to appear.   Only Gary knows how often and for how long his engine will be steamed.

Only Gary knows also the working pressure (and hence temp), volume etc of his boiler.

True, but I don’t believe working pressure alters the risk of dezincification much.  Not compared with how often the engine is steamed.   Having swotted up, I think dezincification is most likely to occur whilst the engine is warming up before a run and again when it cools down after.

…
Dave

Some reasonable points but very much presented in a sanctimonious, superior and scaremongering manner which I don’t think was particularly helpful.

Paul.

Sorry if my written style upsets anyone.

• Sanctimonious:  not guilty!  Nothing I wrote in response to Gary’s question implies I am morally superior to anyone else on the forum.  I provided an engineering answer to an engineering question.
• Superior:  maybe, but only in the sense I’ve suggested an engineering technique not everyone is familiar with. Risk Management is a useful discipline, especially when attempting anything new.  It’s almost universal in design work.
• Scaremongering: not guilty!   Unless suggesting Model Engineers might think a little about risk somehow threatens the foundations.

In my defence, I try to explain suggestions, which makes the posts longer than I like.  I also try to introduce new ideas, some of which challenge sacred cows.  My message isn’t “SOD believes everyone is an ignoramus”, it’s “here’s an idea, might it work for you”.  Is the problem that experienced men dislike learning new tricks?

Dave

[JasonBModerator @jasonb]

Irrelevant to Gary I feel?  Steam toy boilers are tiny, and are unlikely to cause death and destruction in any circumstance!  And they don’t generally last long – most of ’em scrapped after a few years fun.   Not to be compared with Gary’s much more grown up engine.

 

Well I don’t know about lasting a few years, look at all those old Mamod, Wilesco, Bing, Plank, Doll, etc “toys” that are still about after 100yrs

 Experience is good, but only if up-to-date and relevant.  When someone claims experience, double check!

Yes better to listen to those that have experience of making steam engines than those who don’t. Be that the designers of many a model engine or those here that have replied and who make model engines. What do you make Dave?

True, but I don’t believe working pressure alters the risk of dezincification much.  Not compared with how often the engine is steamed.   Having swotted up, I think dezincification is most likely to occur whilst the engine is warming up before a run and again when it cools down after.

If it were going to affect the regulator then I would think totally the opposite. As has been said Dezincification happens when the WATER is in contact with the brass. The only time a regulator will tend to risk coming into contact with a small amount of water is if it primes, this usually happens when it is at full pressure and literally boils over. The steam it sees the rest of the time will not contain the chemicals that were present in the water it wasproduced from so nothing to attack the zinc. Stop reading about household plumbing and get your facts right.

[John HaineParticipant @johnhaine32865]

Garry, how much bronze would you need and what size?  I have a metre-odd of 1″ bronze bar that will never all get used (by me).  PM me if interested.

[SillyOldDuffer]

On SillyOldDuffer Said:

 

On the technical side, much depends on the water.   I recommend Gary reading the Corrosionpedia article on dezincifation to decide how many of the risk-factors apply to him, or not!   Edited highlights:

Conditions favoring dezincification are:

Contact with slightly acid or alkaline water
Water with little aeration
Low flow rates of the circulating liquid
Relatively high tube-wall temperatures
Permeable deposits or coatings over the tube surface

And

Elevated temperature and coupling to a more noble metal can increase the dezincification. If brass bosses are used on copper hot water cylinders, the combined effects of the high water temperature and coupling to a large area of copper can give rise to significant dezincification even in waters that normally would not cause problems.

Why would you suggest he reads that in relation to his regulator?

Conditions favoring dezincification are:

Contact with slightly acid or alkaline water no significant contact with water just steam
Water with little aeration No contact with water aerated or not
Low flow rates of the circulating liquid No liquid circulating
Relatively high tube-wall temperatures No tube involved
Permeable deposits or coatings over the tube surface No tube surfaces

And

Elevated temperature and coupling to a more noble metal can increase the dezincification. If brass bosses are used on copper hot water cylinders, the combined effects of the high water temperature and coupling to a large area of copper can give rise to significant dezincification even in waters that normally would not cause problems. Again not in contact with water. A domestic HWC would be considered quiet  alow temp when compared to a steam boiler

[Paul KempParticipant @paulkemp46892]

Oh dear……. Lots of things wrong with your view Dave but one stand out para that illustrates you don’t follow your own risk assessment advice or have thought about the complete pressure system;

“I suggest the boiler inspector should be asked about the regulator, not about minor fittings, which as far as I know aren’t controversial.  Gary’s risk simply is that an inspector might reject a Brass regulator.  No need to rely on ME forum advice, just ask the Boiler Inspector.   He’s the responsible expert, not the forum!”

As noted by others the fittings at risk are those immersed in the water or with water flowing through them example being the lower leg of the gauge frame, blow down valves, clacks and wash out plugs if fitted (your minor fittings).  In fact the consequences of a failure in these items as they are on the outside of the boiler shell and if they fail will carry some velocity and be capable of inflicting injury similar to a bullet are far higher than the consequences of a failure of the regulator body or components which are inside the boiler.  In addition any release of steam as a result of the regulator passing or failing is contained by the headers and pipes to the steam chest and cylinders and movement controlled by the valve gear.  So the apparently minor fittings you cite which as far as you know are not controversial are actually a lot more important than you give them credit for!  This illustrates a clear gap in your understanding and knowledge and undermines the quality of your advice.

If you need to train someone in the use of the reverser I would submit they are not competent to be driving in the first place.  Anyone driving a loco with superheaters will know the reverser is your last point of control especially in large scale or full size in the event there is water carry over.  In that instance the water flashes to steam in the superheater downstream of the regulator and your only control is the reverser, seen it and done it.

I don’t think it necessary to put a CV with forum posts but among other things I have had many years of lighting up, firing and driving miniature and full size steam both road and rail.  I am also a boiler inspector for a model society and approved by the insurance company to inspect to the full volume of the code.  If I were the person inspecting this boiler the use of brass in the regulator assembly would be a long way down my list of potential reasons to refuse a certificate and if asked to inspect it my risk assessment would be the likelihood of failure is low as it is in the steam space, any failure likely to be slow to manifest and not catastrophic and the consequences of this failure are low due to the mitigation measures provided by the reverser to contain it. So there is one inspectors opinion based on the limited information available and without knowing the volume of the boiler, working pressure or the benefit of actually seeing it.  Other inspectors opinions available.

Plenty of examples in commercial drawings that specify brass for these components and there are actually grades of bronze that are not eminently suitable to this application either.  So the assumption that bronze is automatically a better material is not a given either unless you are sure of the grade!  Maybe stick to plumbing?

End of.

Paul.

[JasonB]

On JasonB Said:

On SillyOldDuffer Said:

 

On the technical side, much depends on the water.   I recommend Gary reading the Corrosionpedia article on dezincifation to decide how many of the risk-factors apply to him, or not!   Edited highlights:

Conditions favoring dezincification are:

Contact with slightly acid or alkaline water
Water with little aeration
Low flow rates of the circulating liquid
Relatively high tube-wall temperatures
Permeable deposits or coatings over the tube surface

And

Elevated temperature and coupling to a more noble metal can increase the dezincification. If brass bosses are used on copper hot water cylinders, the combined effects of the high water temperature and coupling to a large area of copper can give rise to significant dezincification even in waters that normally would not cause problems.

Why would you suggest he reads that in relation to his regulator?

Conditions favoring dezincification are:

Contact with slightly acid or alkaline water no significant contact with water just steam
Water with little aeration No contact with water aerated or not
Low flow rates of the circulating liquid No liquid circulating
Relatively high tube-wall temperatures No tube involved
Permeable deposits or coatings over the tube surface No tube surfaces

And

Elevated temperature and coupling to a more noble metal can increase the dezincification. If brass bosses are used on copper hot water cylinders, the combined effects of the high water temperature and coupling to a large area of copper can give rise to significant dezincification even in waters that normally would not cause problems. Again not in contact with water. A domestic HWC would be considered quiet  alow temp when compared to a steam boiler

Sigh, I must be the most misunderstood poster on the forum.  Probably my fault.   It’s risk management that I’m highlighting, not specific guidance on regulators.  Everybody please write 100 times “SOD is talking about Risk, not Regulators”.

As Gary’s concern is dezincification, I suggested he read the CorrosionPedia article on the subject.   The article is information, not my answer. It allows Gary to do exactly what Jason has done, that is to run down the list of risk factors and decide whether they apply to his build or not.   Then Gary decides.  Simple as that.

We are in agreement about contact with water and much else.  I said, ‘I think dezincification is most likely to occur whilst the engine is warming up before a run and again when it cools down after.’  To amplify that, when the boiler is up to pressure,  the steam will discourage dezincification as per CorrosionPedia. But, in terms of risk, this happy state exists only when the engine is hot to trot.  At other times the regulator will be wet due to condensation, hence it could lose Zinc.  Read carefully:  I’m not saying that means the regulator must be Bronze.  I’m only saying the designer should consider the risk if it’s Brass!   What he decides to do about the risk is down to him.

At no point have I said Gary should not use Brass, nor have I suggested he de-risk by using Bronze.  A few members have jumped to that conclusion, but they are mistaken.  I repeat, my posts are about risk assessment applied to choosing a regulator material, not me laying down the law on regulator construction.

The principle is that one identifies the risk and decides what to do about it.   Does anyone not understand that the easiest way of derisking the possibility that the Boiler Inspector might reject a Brass regulator is to ask him?   If he’s happy with Brass, Gary is good to go.  The expert has spoken!

By the by, anyone noticed risk assessment allows other materials to be considered?  It’s one of the advantages.  I’m not claiming PEEK or PTFE would do the job, but could be worth considering.  And ball-valves…

Dave

[JasonBModerator @jasonb]

But give him the right info to make is risk assesment

We are in agreement about contact with water.  I said, ‘I think dezincification is most likely to occur whilst the engine is warming up before a run and again when it cools down after.’

Your link says it is more likely at higher temps, so why do you think it is more likely when cooling down or raising steam?

To amplify that, when the boiler is up to pressure,  the steam will discourage dezincification as per CorrosionPedia. But, in terms of risk, this happy state exists only when the engine is hot to trot.

At other times the regulator will be wet due to condensation, hence it could lose Zinc.

Condensate will be cleaner and purer than tap water or acid rain that the boiler has been filled with so won’t be a problem.

Read carefully:  I’m not saying that means the regulator must be Bronze.  I’m only saying the designer should consider the risk if it’s Brass!   What he decides to do about the risk is down to him.

 

[Paul KempParticipant @paulkemp46892]

Dave,

Fine, I get it, you had a well intentioned aim to promote risk assessment.

Fellow asks a question, rightly so because he is aware of potential issues with brass and boilers.  He gets a few reasoned responses that should reassure him the material being discussed for this application should be fine.

Then you pile in with your risk assessment crusade.  You use words like coroner, design authority and potential failure when this material decision has already been risk assessed many times before with a reasoned (and proven) result.  Then you go on to challenge the competence of those that have replied, the problem is your own perception of risk of the situation is flawed.

Now in your last contribution you are suggesting other materials might be considered including ball valves.  Yes ball valves have been used, yes they work but what are they made of?  Where do you obtain one of a suitable material and of a suitable size?  No need to reinvent the wheel, fellow just wants reassurance on his material choice which was provided by several people with experience which you choose to dismiss as potentially invalid!

If you were flagging a valid risk that gives rise to a dangerous situation I would be the first to support you (if I saw it).  Fact is this is a non issue.  If you want to champion risk assessments then start a new thread and let the fellow get on with building his engine without trying to worry him the death!

Paul.

[Nigel Graham 2Participant @nigelgraham2]

.Condensate will be cleaner and purer than tap water or acid rain that the boiler has been filled with so won’t be a problem.

 

Condensate? Well, as the boiler cools, but in operation the regulator is surrounded by steam, but that itself will be pure water.

Tap water? That can contain dissolved calcium carbonate and/or other rock minerals, but those are generally left behind by the steam rising from the water. They stick to the submerged tubes and shell surfaces, instead.

Acid rain? Rain water is naturally slightly acid, by dissolving carbon-dioxide from the atmosphere. It is this that dissolves limestone or chalk (same mineral) to give hard water. Standing in a water-butt though, subject to changing temperatures, some of that gas may come out solution and disperse back into the air. Inside a boiler, it will come out of solution but whether it is enough to attack any metal is a moot point. Personally, I’d be surprised if it can.

The sort of acid rain that Britain once unwittingly exported to Scandinavia was weak sulphuric acid from coal fumes… but as another thread on this esteemed forum has explored, we have largely given that up. The rain we have is distilled Atlantic Ocean so highly unlikely to be sulphurous to any significant degree. Descaling our boilers uses “heavier” stuff than that.

.

Commercial ball-valves have found popularity as regulators, especially on hefty narrow-gauge outline locomotives with room to fit them on the backhead or in a large dome without unduly harming the looks of the machine.

Be careful though: many of those sold for domestic plumbing are not only excellent flow-restrictors (aperture area about 1/4 that of the pipe) but more seriously their three O-rings are not necessarily suitable for steam at around 200ºC.

(There is an O-ring on each side of the ball, and one sealing the spindle.)

What would happen if those fail? Probably, just result in a leaky regulator, but not ever so dangerously. They are good though, as water-valves for injectors.

[duncan webster 1Participant @duncanwebster1]

The acid rain we created didn’t all go to Scandinavia, the peat lands of the Pennines have been badly affected by acid rain from Lancashire. Efforts are underway to restore them by spreading lime and putting dams in the little water run offs to try to stop the peat washing away. I know peat is acid but you can have too much of a good thing, at least according to a programme I saw some time ago

[Nigel Graham 2Participant @nigelgraham2]

I’m not sure that much more damage was done to the peat moors by “gripping”.

That was a scheme “not invented here” to dry the moors by digging ditches – the “grips” – to streams on lower levels, and on the limestone areas of the NW Pennines, to sinks, to try to encourage the growth of wild grasses more delicious for sheep.

It didn’t work (there’s a surprise) – so lots of new subsidies were paid to reverse the damage by partially refilling the grips, by those dams, leaving small intervening ponds to encourage wildlife such as dragonflies.

However, there is far less artificially acid rain now simply because there are no large-scale industrial coal-fired power-stations left.

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Even when there was more sulphurous-acid rain I cannot say if if it would have been enough to harm a model boiler. Unlike trees and masonry, exposed to any all weather, we don’t use our models every day, and when we do steam them, it is not normally for more than a few hours, using a fairly small volume of water.

I think scale, in hard-water areas, would be the greater threat to the boiler.

Nevertheless, it would still seem wiser to use bronze or gun-metal for the regulator and other non-structural fittings, though has brass for external parts ever really been a problem?

Regarding what club boiler inspectors might say, there are anecdotes of some nervously “gold-plating” the MELG requirements and refusing to accept boilers for the wrong reasons. The Good Book (orange and white edition) confines itself to the materials welded or silver-soldered together to form the boiler structure, and not to the nth degree, either; not the fittings’ materials, and it says nowt about items like the grate and ashpan design.

 

[Oddly, the original PER document, the UK Law version of the EU Directive, waffles on in legalese only about two pressure-vessel materials: aluminium (!) and the stainless-steel our lot will not investigate seriously. Not copper and its alloys, including appropriate grades of silicon-bronze, nor mild-steel.]

 

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