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[Underpressure]

Hi, newbie here.

I have been out of the loop for a number of years, but at one point I was a very active model steam boat builder / sailor.

I have a number of models which I would like to put back on the water, and wonder what the current regulations are regarding the pressure testing of boilers, safety valves and gas tanks.

Any help / pointers would be much appreciated.

Neil

[Colin Bishop]

Have a look on the Model Boats magazine site which carries the MPBA requirements on steam testing.

http://www.modelboats.co.uk/editorial/page.asp?p=271

Colin

[HS93 (RIP)]

Neil in case you get the wrong idea after reading the MPBA rules on boiler tests they are just THERE rules that are very over the top and only apply to there members , why they insist on them I dont know but the actual rules can be found by following the link the MPBA is only a shadow of the size it was, and not helped by things like this

http://www.nadmes.org.uk/pages/resources/boiler_testing.aspx

Peter

[gondolier88]

Hi Underpressure,

There are categories of boiler size that determine what testing procedure must be used-

- Under 1 BarLitre by volume- exempt from testing by EU reg.s, however as mthis covers just about all model boat steam boilers many model engineering societies/ model boat clubs etc will have their own testing protocol as will your insurance company- public liability insurance that will be requirement by all public groups- model boat clubs etc.

- Over 1 BarLitre upto 25 BarLitre by volume- of course way over at 25 Barlitre anything that a model boat will have- however a large boiler can easily have 1 BarLitre- a model 7 1/4" loco for example will more often than not be around 2-4 BarLitres. This category requires a 5 yearly pressure test of 1.5 times working pressure- of course one at it's point of manufacture too. An inspection under steam at working pressure is required after a satisfactory pressure test- a safety valve test will also be undercarried- testing that it opens at the correct pressure and won't let the pressure go above 10% more than working pressure at full tilt.

- Over 25 BarLitre- the same as above but more in depth inspection- though if your fitting a boiler of this size in your launches then i'd be rather surprised.

Find your local model engineering society for guidance on your particular boiler's need.

Greg

[Bunkerbarge]

Greg,  Most interested parties, apart from the MPBA who seem to insist on upsetting the apple cart and going against just about every one else, have now adopted the 3 bar-litre rule for model boats.

Thereby technically most model steam boats are exempt from the requirement to test the boilers, however the regulations also state a requirement for sound maintenance, which is open to interpretation to say the least, as well as recommending that the safety valve is tested annually.  For me that should be a requirement and not a recommendation but you can't have everything.

So, if you are within the 3 bar litre rule you don't need to test the boiler unless you are at a MPBA sponsored event.  Don't forget as well that some clubs and even councils put thier own requirements on top of the regulations so it is still not as simple as it should be.

[Underpressure]

Thanks everyone.

The club I was involved in were affiliated to NAME (I think they still are) as at the time they were the only society that even recognised both marine boilers and more importantly gas tanks.

Whilst on the subject, what about gas tanks?

Neil

[Circlip]

Due to the "serious" consequences of an accident happening in a public place, I'm surprised that Safety valves aren't tested as a matter of course at the organising club premises IMMEDIATLY BEFORE allowing anyone to steam up at an organised event. It shouldn't be too difficult to design and manufacture a "Standard" pressure testing rig with instructions that everyone attending should ensure they have an adaptor to suit the test gears standard thread. On the toy train sites boiler test certs have to be furnished by visitors and yes, Loco's are in a closer proximity to the public, but why not act BEFORE owt goes spheroids up??

   Regards   Ian.

[gondolier88]

Hi Circlip,

You can't just hook up a boiler to a pressure tester and say everything is alright-

1- It is also a visual inspection so all the lagging must be out of the way and every joint must be visible- on a model loco this is hours of work of scratching of paintwork!
2- It is a pressure VESSEL test so all the ancilliary valves must be taken off and the connections blanked off- water gauges, feed check valves, any pipework, blowdown valve etc.
3- Under a pressure test the boiler is left at 1.5 times working pressure for 3 hours- meaning that if two people have steam models that would require testing then you'd have to wait 6 hours before you could steam up!!!!
4- Unless you know the boiler has succombed to damage, and if it is copper, you can be pretty sure that it's safety is still ok.


Greg

[flashtwo]

Hi,

Build a flash / monotube boiler and avoid all the above problems!

Ian G.

[Bunkerbarge]

What most people seem to miss is the fact that safety valves cannot be tested off the boiler.  Getting them to lift is only half the issue.  They also have to relieve the pressure fast enough to ensure that is cannot rise even with the burner on full.

Just imagine someone has fitted a huge burner to provide enough steam for a hungry engine.  Something goes wrong and the pressure builds up to the point where the safety valve lifts.  However the burner is capable of providing enough heat to generate steam faster than the safety valve can relieve it.  Consequently the pressure still rises in the boiler.

This is actually unlikely in a model boiler but it is possible and so it is a much better test to see the safety lift on the boiler with the main stop shut and the burner on full.

[gondolier88]

  Go Ian G!!!

[flashtwo]

Ah Bunkerbarge,

....the fun days of the accumulation tests - not to be missed!

Ian G.

[Circlip]

Greg, no matter how many times I read wot \I rote does it say "Hook a boiler to a test rig" and sorry BB, are you seriously saying that a safety valve when set to release pressure at 30psi doesn't??

  Unscrew the safety valve from the boiler and test separately. We are talking pressure relief and NOT the ability to cope with a total CSA capability.

  Alternative??? Is summat better than the nowt you have a present ??? At least the organisers have SOME control.

  Regards  Ian

[Bunkerbarge]

BB, are you seriously saying that a safety valve when set to release pressure at 30psi doesn't??

  Unscrew the safety valve from the boiler and test separately. We are talking pressure relief and NOT the ability to cope with a total CSA capability.

   

No read what I said.  It will release pressure but it may not release enough to bring the boiler pressure down if the burner is generating steam at a greater rate.  I can assure you Lloyds do not accept hydrostatic testing of boiler safety valves, they have to be under operating conditions with the burner on full and the main steam stop closed.  Exactly the same principle is used with exhaust gas boilers which have to be tested with the engine on full load and the steam stop valve closed.

Anyone who tests a safety valve off the boiler is seriously misunderstanding the purpose of the device, which is most definately not to simply lift at a given pressure.

[Circlip]

When a safety valve lifts there is forced to be a reduction in pressure, whether it has the ability to release at a rate fast enough to make the boiler safe is down to the suitability of the CSA of the valve outlet??  Since my source of referance is Harris and such which are obviously out of date, can you point me to the new regs for toy boilers and how to set and size a safety valve?? Hydrostatic boiler tests don't seem to have changed much, but obviously, we seem to be at the point where, without a set of signed and sealed certs, I for one will steer well clear of Batley Road.

  Regards   Ian.

[Bunkerbarge]

That's a relief.

[Circlip]

Good to see the spirit of boaties is as good as ever

[boatmadman]

Just to add a bit...

I work in a combine cycle power station. When work is done on the safeties, or they need to be tested for insurance,the gas turbine is fired up, boiler pressure raised and with the steam turbine shut down, steam bypass control valves forced shut to raise drum pressure the safeties are lifted and adjusted to the correct pressure. Pressure is raised through simmer to full bore lift and then re seat. If an adjustment has been made, they are lifted again to prove!

This is the ONLY way acceptable to prove they can cope with the heat input and prevent the boiler pressure rising out of control.

Testing and floating safety valves this way is the only way I have done it in over 30 years - at sea, in chemical factories and in power stations. I would not accept any other method.

For our model boilers, it is sometimes difficult to differentiate between simmer and full bore lift, but the real critical factor is as BB says, they MUST be able to cope with the maximum steam raising capability of the burner(s) without the boiler pressure going out of control.

How do we check it? Easy, shut the steam stop and turn the burner on full burn, if the steam pressure does not continue to rise after the safety lifts - you got the right size valve!

Ian

[gondolier88]

Hi Circlip,

I must apologise, I misread your post.

However, as Bunkerbarge says, a safety valve cannot be tested on a rig hydrostatically-

1- Safety valves are a pressure relief valve, not a temperature/pressure release valve- as such they handle only gasses and are not reated to expel liquids- meaning a hyrdostatic test is obsolete.

2- A off-the-boiler test on a rig can also not be accepted- a simple example-

A watertube boiler with an output of say 100lbs/hr output @ a working pressure of 200psi. It is fired with liquid fuel with two burners with a common control- both burners work together- they are working fine one minute, but the next they are jammed on full power.

Now of course any normal person would shut the oil off etc. However, the DoT assumes that it is the most stupid person running the plant- as such the plant needs to cope with the problem by itself.

As I said it has an output of 100lbs/hr, and as I pointed out in my first reply the safety valve/s cannot let the pressure rise above 10% working pressure, so with a safety factor added in it/they must release 120lbs/hr, or 2lbs/min of steam.

Now your proposal is to stick it on a rig- it would have to have a working pressure of 200psi to match the boiler- thats acheiveable, however it would also require an output of 100lbs/hr- but what if the rig could only muster 90lbs/hr, this would of course not be a true test under working conditions.

The requirements to test the safety valves on a full size passenger ship are as follows- this is the testing procedure on Sy Gondola-

There are two safety valves on Gondola, both with an output of (around!) 150lbs/hr, they both have a locked cap to prevent tampering- however both can be manually held open using a hand wheel on the forward bulkhead of the engineroom which is connected by a steel cable to both arms of the safetys. In this manner the DoT inspector will time the safetys for 10mins and see if the pressure rises more than 10% with a roaring furnace- of course it doesn't, otherwise we wouldn't be able to steam.

Now imagine we took one of our safetys and stuck it on your test rig of 90lbs/hr- ask yourself, would they have the same test conditions on that rig as on Gondola's boiler?

Greg

[Circlip]

Whoa, First Greg, have another re-read, Hydrostatic testing safety valve????? No I didn't. And both your reveared selves (Greg and Ian-boatmad) I fully accept the requirements of full size practice for Lloyds certification etc. and without wishing to say that unsafe standards should be applied to TOY sizes, we really should take a practical look at the basic problem of having a quick acceptable test, as obviously Joe public can't be trusted to play fair.

  As an aside Greg I remember reading the report of the accident taking the life of one of the gang of Lakeland members who was VERY experienced in the ways of full size and KNEW what he was doing, Sh*t does happen and no matter how careful we are, something is always ready to bite yer bum.

   Years ago, due to the arrogance and stupidity of the C/B brigade in forcing their case by operating illegal "Rigs" thus causing a fufore in the ranks of the Radio control fraternity to have to adopt a "Defensive Flying" operation by clubs and event organisers having available a scanner to operate over our frequencies. Funnyly enough, one of the conversions to a scanner used an illegal set as the basis and some who worked in the electronics industries made portable Spectrum analysers available - rather overkill but nevertheless the thought of a killer toy injuring not only fellow competitors but ALSO the anti - Boys Toys brigade.

  OK., back to normality, ALL I suggested was a pond side device working purely on AIR pressure, NO Hydro whatevers, to give event organisers SOME sort of indication that the alleged "Safety Valve" was actually working or not and SOME indication of a release pressure.

  Now if you want to hold a boiler testing and certification  session at the pond side with qualified boiler inspectors, So Be It, but that was not the original intention.

  Toy boats work in 2 dimensions (OK 3 for Subs) so part of the problem is is null and void, BUT boiler bangs work in 3 dimensions (Don't matter much for a submerged K-Class) and given that "Where there's blame there's a claim" fraternity is firmly ensconced, some effort to protect ourselves must be good???

   I'll try the question I asked,  How do you test a (TOY) Safety valve???

  Regards  Ian.

[gondolier88]

To test a 'scale' safety valve run the boiler upto full pressure with burner on full, steam stop valve shut. When the safety opens, watch the pressure- it will rise even though the safety is blowing off- but make sure that it doesn't rise 10% (or more!!!!) over working pressure- for example the working pressure of the plant I just installed is max 70psi- so with safetys blowing it would not be ALLOWED to rise above 77psi.

Also check to see if it reseats or not- a good indication of the condition of the seat of the valve.

Greg

(edit) Also interested in the account of a steam accident in the Lakes taking a life- the last marine steam accident in the SBA was in the 1970's, when the boiler mudhole door on SY Carola had corroded on it's collar and blew under full pressure- the resultant explosion killed the engineer and seriously injured the second engineer.

All the steamboats in the Lakes are part of the SBA and I know of no accidents- not to say there hasn't been any- as I said i'm very interested to hear details.

However on the subject of safety valves- there has NEVER been an accident involving safety valves where the valves have failed on their own, they have ALWAYS been tampered with- holding them down to eak that bit more from the boiler to give that few more RPM to get that .5 mph quicker to get that bonus etc. Only an idiot would stop the one means that differentiates between a steam plant and a bomb. Ever since the evolution of high pressure steam, from just after Richard Trevithick's day, safety valves have been one of the most accurately designed, maintained and relied upon pieces of equipment on a boiler. There have been hundreds of steam accidents since then, many fatal, but all have something in common- poor maintainence and/or neglegance on the part of the engineer not realising there was a problem and the boiler's inherent weaknesses being found by said problem.

Just out of interest- the engineer on SY Carola was found guilty of criminal neglegence.

Greg

[Circlip]

OK, it lifts/blows at 70 psi and DOES exceed 10%,  then what??

[gondolier88]

Either reduce the working pressure, or swap the safety valve for one with a higher output.

[Bunkerbarge]

....or don't allow it to steam.

Testing safeties in this way is far easier than taking the things off and messing around with rigs and compressed air supplies and tests the device properly in it's working environment.  I can't see why we would want to make things more complicated and less effective in the process.

[Circlip]

Higher output Greg? One with a larger free "Open" area ?  The pond side is not the place for boiler design and that's what I'm not trying to do. All I am trying to show is that for a commercial plant OR home made one that will/should have been tested properly has the ability to release pressure at a pre determined point.

   Yes, the incident I remember was the one you note.

  Come on BB, "Compressed air supplies"?  Never heard of a bike pump? and don't forget, Blowlamps and Roarer burner tanks have/used to have a "Compressed air supply generator" built in. It could also be said that with a suitable tank and a length of rubber tubing a PUMP isn't neccessary.

  Rocket science is NOT required, a bit of PCB with a few components can effectively do a load test on a receiver battery ---  Sorry, bad similie, we USED to do this, point taken.

  Regards   Ian.