Take a look?

[David JuppParticipant @davidjupp51506]

Posted by Neil Wyatt on 30/12/2016 12:52:44:

Well here's another interesting snippet. – CE marks are no required for one offs.

So anyone can make and supply a single boiler without a CE mark, as long as they don't make and sell that design again.

Neil

Neil – could you please tell us where that information was sourced? I'd be interested in the context.

[mark costello 1Participant @markcostello1]

Michael-w, are You saying "they only want You for Your mind?"

[Andy AshParticipant @andyash24902]

The thing that interests me about this thread is the interpretation of the Category 1 vs "Sound Engineering Practice" group of boilers.

By the letter of the directive, the Juliet boiler should not fall into the Category 1 class. I did not accurately calculate the volume of the boiler, but I did look at the drawing. Doing the sums the boiler has a volume around 1 litre which is well less than the 2 litre limit for sound engineering practice.

Though I've not done the sums, I'm expecting that a 5"G 4-6-0 would be more than the 2 litre limit, and if not that a large 5"G pacific would certainly be so. Obviously these fall into Category 1.

All of the above would be within the scope of an average model engineer. The question is "Should the Juliet boiler be CE marked". Strictly, it should not.

The thing with this is that across the hobby there is uncertainty about the meaning of the CE mark. If the hobby were bigger or more valuable the regulatory authorities would be worried about that. The idea that a broad category of "products" should have ambiguity is not a good thing for the CE marking its self. Certainly, pressure vessels used in specific applications are regulated within those applications for exactly those reasons. The trouble is that it is not worth having a classification solely for model steam locomotive boilers. We as hobbyists get a general framework and it does not fit very well. No-one really cares about the boilermakers. As far as the authorities are concerned, the CE mark is for the hobbyists, not the boilermakers.

My opinion is twofold.

Firstly, setting aside the practical implications, there is no harm in attempting to certify a boiler in a more stringent category. Broadly common sense dictates that as the pressure volume product (bar-litres) increase, the consequence of a boiler failure increases.

In practice, the directive cites different approaches for SEP and Cat 1 boilers, and to me there are elements of both which would be best practice in either other. There are actually no limits, bar the application of the CE mark, to a boilermaker using best practice from one in the other. Equally, there is no mandate for it, so it should not be expected.

In my opinion, this is the wrongness of claiming the "CE mark high ground". What should matter is that it is a good boiler, not that it is CE marked. Perhaps some of the lesson that the directive presents, is that it might be better to buy a boiler without a CE mark if you actually know better.

The second element of my opinion relates to the reasons behind the 0.5 bar and 2 litre limits for safety and SEP. I think that the 0.5 bar limit is fairly obvious. The way I see it is that if the vessel only has 7 (ish) psi inside, it cant do much harm, even if it is made of cheese. Indeed all mice know of the dangers of squashed Emmental. (It's not the exploding bubbles in the cheese that get you!)

I don't know for sure, but I think that the volume limit of 2 litres, has been arrived at to allow for monotube (flash) steam raisers. These are reasonably common in consumer grade products, and are normally seen as safe from explosion. The thing with flash boilers, is that they have no significant volume of liquid water above the boiling point. If a breach were to occur, there is no significant volume of water that would flash to steam.

Obviously the authorities would have the difficulty of onerous regulation over products like flash boilers that do not warrant concern. These authorities must have to draw the line somewhere. In the end I guess they say that 2 litres of water at any temperature cannot cause harm. This is clearly not the case, because in my mind even the Juliet boiler is going to be a little nasty if it actually does go pop.

If you wanted to bend the rules to be as dangerous as possible whilst still being compliant then this would be one loophole to exploit. You can build a 1.99 litre vessel and run it at 100,000 psi, but you don't need a CE marking, even if it is made of Emmental.

Realistically, the Juliet boiler is only a mild form of these boundary cases since it probably only works at 90psi which is around 6 of the potential 25 bars available to boilers of the same size, in Cat 1.

To me, not CE marking a Juliet boiler is classifying it as a flash boiler, which it is not.

Is it wrong to CE mark a Juliet boiler? I don't think so.

Is it wrong to claim the CE mark high ground? Probably.

It's just my opinion.

[AjohnwParticipant @ajohnw51620]

There is another area that very probably comes into this. It took around 10 secs to find this just searching pressure vessels. There may well be others.

**LINK**

I've no idea if what ever there is about needs to apply.

These may include design aspect as that is probably the most important aspect of the lot. I know of some in other areas that even include the sums needed to ensure that everybody uses the same ones.

Taking Andy's example 1.99L 100,000 psi – nothing wrong with that if it is designed correctly to work like that.

It all comes down to design in the end. Design needs facts not opinions. If those facts aren't available they have to be determined. It seems that the facts in this case are sort of available but some what I usually refer to as a committee decides that aspect isn't relevant to what they have decided off the cuff to do.

John

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[richardandtracyParticipant @richardandtracy]

There is (well in 2002 and it may have changed since) a limit of 2 Bar.Litres, so if 5 litres and 0.49 Bar, then still needs the CE mark because 5 x 0.49 = 2.45 Bar.Litres, and is greater than the limit of 2 Bar.Litres. I too thought that if below .5 Bar or 2 litres it was exempt, but in my 3 month study could find no regulatory basis for this belief, the one statement in its favour was contradicted in numerous other places.

The whole thing is such a minefield you begin to think it must be deliberate to give the regulators something to justify their existence.

Regards

Richard.

 

Edited By richardandtracy on 30/12/2016 16:53:30

Edited By richardandtracy on 30/12/2016 16:57:03

[Michael GilliganParticipant @michaelgilligan61133]

By no stretch of the imagination am I qualified to comment on this subject, but: My first point of reference [if I had the need to know] would be this: **LINK**

http://www.hse.gov.uk/pressure-systems/law.htm

A quick skim reveals two immediately interesting points:

[quote_1]

Simple Pressure Vessels (Safety) Regulations 1991 (SPV)

Simple pressure vessels have the following characteristics or limitations:

1. intended to contain air or nitrogen at a gauge pressure >0.5 bar but less than or equal to 30 bar
2. not intended to be exposed to flame

[quote_2]

A relevant fluid is:

• steam at any pressure

[AjohnwParticipant @ajohnw51620]

I'm not convinced that any one is Michael. It's probably not a good idea to start looking at the standards side of things.

It is interesting to compare here with there though. Oz for instance – rather interesting as it gives an indication of what they have done there – 2 official certs for download.

**LINK**

It's what's needed really but I would hope that the rules do allow variations providing the strength requirements are met. Eg my embryonic boiler would probably have an excess of tubes passing through it which could mean that there was no need for stays. Maybe not thicker end plates as well.

Not much elsewhere. Panics about state boiler regs in the USA.

Looking at Oz they have turned it into a bit of a money go round. Nice round prices for booklets but not TOTT. On the other hand I am not sure what the exchange rate is now. What they have done though is attempted to preserve the hobby. They have also taken on a certain amount of liability.

John

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[AjohnwParticipant @ajohnw51620]

The link to Oz leaves me wondering what % silver people use ?

John

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