The Bar-Litre Rule

[Richard SimpsonParticipant @richardsimpson88330]

A few years ago I did an article in Boiler Room explaining the Bar-Litre Rule.  As it frequently seems to create conversation I thought I would trim the text down, edit it and put it on here for reference.  Any questions feel free to ask.  Maybe Colin would consider an archive section where such documents could reside as a resource for future reference.

 

The bar-litre Rule.

One thing that seems to cause more confusion than anything else amongst model steam enthusiasts is the bar-litre requirement of the rules. Consequently I think it is worth looking at in a bit more detail and examining a few examples to help you get a better idea of where your own boiler might sit as regards this requirement.

 

Definition

So what does bar-litre mean?  Basically it is nothing more than a product, i.e. multiplied together, of two numbers which represent two size related aspects of a boiler.  One is its capacity, or the internal volume, and the other is its working pressure.  Looking at those two aspects a bit closer, the capacity is the total internal volume available for holding water.  The easiest way of determining this is to fill it completely with water then pour it out into a measuring jug.  The internal volume must be completely filled, with no air, and right to the top of the shell.  This is then effectively the most accurate method of determining the internal volume as it automatically takes into account cross tubes and braces etc.  For the sake of the bar-litre number this volume must, not really surprisingly, be quoted in litres.  Consequently a boiler that holds 500ml of water has a capacity of 0.5 litres and a boiler that holds 750 ml has a capacity of 0.75 litres.  If you want to work in traditional units and only have an imperial measuring jug then a boiler than holds ¾ of a pint would be a 0.43 litre capacity boiler.

A manufactured boiler should be supplied with a certificate that should state an identification number and the working pressure on it, and this should be produced for the examiner who is checking the boiler.  Any home made boiler will also need to have a working pressure, which will be determined from the physical dimensions, with a suitable factor of safety applied and the owners preference if he wants to operate the boiler at a lower pressure.  If a boiler has been made from a published plan the plan should also state a maximum working pressure.

Working pressure must be quoted in ‘bar’, which is the SI unit of pressure and the only unit that can be used to determine the bar-litre number.  So if now we have a boiler with a quoted working pressure we can determine the bar-litre number.  For the ‘traditional’ fans 14.7 psi is the same as 1 bar so you would have to convert a working pressure quoted in psi to bar.  For example a working pressure of 45 psi would equate to:

45 / 14.7 = 3.06 bar.

For most purposes using 15 rather than 14.7 is close enough so in the above example you have a 3 bar boiler.

 

The Product

So now we have two numbers, the capacity in litres and the working pressure in bar, all we do is multiply them together.  A boiler of 0.5 litres capacity with a working pressure of 4.0 bar would be:

0.5 x 4.0 = 2.0

or a 2 bar-litre boiler.

Similarly a boiler of capacity 0.75 litres and a working pressure of 5.2 bar would be:

0.75 x 5.2 = 3.9

or a 3.9 bar-litre boiler.

From this you can see that the first boiler is lower than 3 so it is covered by the rules applying to “Boilers under 3 bar-litres”. Whereas the second boiler is above 3 bar-litres and is therefore covered by the rules applying to “Boilers 3 bar-litres to 1100 bar-litres”.

 

Examples

Let’s now have a look at what that means to us as marine steam modelers and how this relates to some common boiler configurations we can purchase.

2.5 inch boiler

Typically this size boiler has a capacity of around 0.29 litres and a stated working pressure of 4.0 bar:

0.29 x 4.0 = 1.16 bar-litres

This is below three so consequently this boiler is a below 3 bar-litre boiler.

3.5 inch boiler

Typically this size boiler has a capacity of around 0.75 litres and a stated working pressure of 4.0 bar:

0.75 x 4.0 = 3 bar-litres

This is right on the nose of the limit and, as the rules states that boilers are either below 3 bar-litres or they are from 3 bar-litres up to 1100 bar-litres, this boiler comes under the latter category.

6.0 inch boiler

Probably the biggest boiler you are likely to find in a model boat this boiler typically has a capacity of around 2.5 litres and a stated working pressure of 5.5 bar:

2.5 x 5.5 = 13.75 bar-litres

Not surprisingly this is well above the 3 bar-litre limit.

Just to compare with another couple of commonly found boilers

 

Hemmens Ribbersdale Horizontal Boiler

This boiler has a capacity of 0.5 litres and a working pressure of 5.3 bar:

0.5 x 5.3 = 2.65 bar-litres

This boiler therefore falls below the 3 bar-litre limit.

 

Finally the 3.0 inch boiler from Miniature Steam that is supplied with the Clyde engine.

The boiler has a capacity of 0.55 litres and a stated working pressure of 4.0 bar:

0.55 x 4.0 = 2.2 bar-litres

Again well below the limit.

 

 

 

[Len Morris 2Participant @lenmorris2]

Hi Richard,

Thanks for that.  We live with derived units all day long.  Miles per hour for speed and foot pounds for torque are just quick examples.

What we need is a clear plain speak explanation of the implications of the “Bar/Litre Rule”.

How does the “Rule” apply to model boilers?

Is the “Rule” a legal requirement or just best practice guidance for model clubs and insurance companies?

I think this information would be really helpful.

Len

[Len Morris 2]

On Len Morris 2 Said:

What we need is a clear plain speak explanation of the implications of the “Bar/Litre Rule”.

How does the “Rule” apply to model boilers?

Is the “Rule” a legal requirement or just best practice guidance for model clubs and insurance companies?

I think this information would be really helpful.

 

When you say “what we need…..”, the easy response would be to let you have the dates of the numerous editions of the magazine that I have explained precisely those points in over the years and let you get hold of the back issues.

However I will use one as a foundation, edit and trim it down, and put something on here, sometime after Christmas.

[Richard SimpsonParticipant @richardsimpson88330]

Further to the comment above I have taken one of the magazine articles and hacked it down a little to make it a bit less bulky for the forum.  Hopefully it will clarify just how the Bar-Litre rule fits into the grand scheme of things.

 

A Little Background to the Current Rules and Regulations

Firstly why Have Them?

So what drives the need for the rules in the first place?  The way I see it is that modern society seems to contain more and more people willing to consider making money from opportunistic means.  Today’s laws seem to allow legal action to be taken more and more easily by people who see any instance where they perceive any failing in a large organisation as an opportunity to pursue compensation. High profile cases whereby customers have sued fast food outlets in the United States when they burned themselves on a cup of coffee only support this business and lead to an ever increasing number of law firms willing to take on cases on a ‘No Win No Fee’ basis.  All businesses and organisations such as councils and clubs therefore need to protect themselves from such actions and consequently turn to insurance companies where they can purchase protection from the costs of such possible legal proceedings.  I therefore think it is reasonable to consider Insurance Companies as offering us this protection at a price which we pay for in the premiums we, as model boat clubs, pay them.  Interestingly in the case of my own model boat club the local council require us to be insured for third party liability to a particular level for them to allow us to use the facility of the local park thereby protecting themselves as well.  Not surprisingly the insurance companies then have the right to dictate certain conditions under which they are prepared to insure us, in pretty much the same way as your house insurance would be invalid for theft if your front door was left open at the time of any robbery you might want to claim for or your car MOT was out of date at the time of a collision.  In the case of operating model steam plant in our boats the insurance companies require us to comply with a specific set of rules, which will then satisfy them that we are operating in a safe and responsible manner.

What Are They?

Prior to January 1st 2006 all relevant bodies concerned with model boat steam plants such as insurance companies, clubs, societies, local councils and even the Health and Safety Executive had their own sets of rules.  This was obviously very difficult to understand and comply with and put a lot of people off this area of the hobby completely.  Another side effect of this was that there were many modelers who simply ignored the rules in the knowledge that no-one else knew what was going on either and so no one could really hold them accountable.  Consequently, as of the 1st January 2006 these organizations all got their heads together and published a set of rules and regulations for the safe construction and operation of model steam plant.

These rules have been accepted by the Health and Safety Executive, most of the big insurance providers and most modeling organizations and societies and make it now far easier for everyone to know just what the rules are and therefore who is not complying with them.  These rules were compiled into a single book, in the past being known as the ‘Blue Book’ and then the ‘Green Book’, however the current version being the ‘Orange Book’ which was accepted and adopted by all organisations concerned.  Consequently, if your club wishes to operate steam models, your club’s insurer will usually require your club to adhere to the ‘Orange Book’ set of rules.  The current set of rules, the ‘Orange Book’ is split into three volumes. Volume 3 covers gas tanks under 250 ml and Volumes 1 and 2 cover two different size ranges of boilers.  This size is determined by the 3 bar-litre rule thereby classifying boilers as either Boilers 3 bar-litres to 1100 bar-litres, covered by the rules in Volume 1 or Boilers under 3 bar-litres, covered by the rules in Volume 2.  The majority of boilers found in model boats are covered by the rules in Volume 2.

So What Does This Mean For Me?

The classic attitude towards today’s rules and regulations usually seems to be generated by the older members of the clubs and organisations who have lived through a period where Health and Safety was rarely considered and all were pretty much free to do as they pleased.  There are those who then see that as learning things the hard way, i.e. via the school of hard knocks, and there are some of those around who still bear the scars of those lessons.

As my own club wishes to operate steam models and we are required by the council to have insurance cover to protect us against the costs of public liability actions, the club’s insurers require the club to operate under the ‘Orange Book’ set of rules.  What I think is a great shame is the fact that the ‘Orange Book’, which has taken input from a huge number of very qualified and skilled model engineers to put together and which has evolved over the years to what it is nowadays, is still looked at with a degree of skepticism and negativity.

Because this particular set of rules has been put together by model engineers for model engineers the process has been used to create a set of rules that are actually very useful to us as steam modellers.  They contain guidance as regards what testing will be required for your particular model as well as guidance notes for the boiler inspector so you can even be ready for what he may want to look at during his testing and certificating process.  The book, along with its associated certification system has actually developed into a very useful handbook for steam modellers as regards the safe operation and testing of their models as well as general advice and I would encourage everyone who owns and operates steam plant in their models to get hold of a copy and read it through.  I really think they would find it at least interesting and informative and may well be very helpful.  Obviously the rules are written to apply to a wider audience than just the model boat people so you have to skim over the parts that do not apply to you and focus on the parts that do but, when you have got to the relevant bits it is surprising at just how much useful guidance there is.

So basically, if we wish to operate our steam powered model boats in a public place, we have to make a decision.  If we operate them entirely at our own responsibility, we have to accept that, should any litigation be aimed in our direction, it will be entirely at our expense.  Say your at the pondside, raising steam, your back is turned and a child decides to put their hand into the model and burns themselves.  You would quickly find a civil suit aimed in your direction from the parents and you would have to deal with it legally on your own and at your own expense.  If, however you wish to be covered by an insurance policy to protect yourself from the costs of such an action you will need to be a member of a club whose insurance policy covers them for the operation of steam models.  For that to be valid the model must be manufactured, tested and operated according to the requirements of the current rules.

Having said that I also try to promote the rules as a useful handbook for anyone wanting to operate a steam powered model to help guide them towards a safe set of operating practices and procedures.

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