Is my safety valve functioning correctly?

DannyTheElfman said:
Hey everyone. Just a quick update. I heeded your warnings and took the engine to a a friend who works with compressors so I could figure out exactly what was going on. Several important discoveries were made.

First discovery: The big one. The pressure gauge is totally incorrect. At 55psi the gauge on the loco reads 45psi. The gauge appears to be pretty unreliable throughout the entire pressure range. Not good. This will be replaced.

Second discovery: Safety valve. As it turns out, this doesn't appear to be a problem at all. It starts to release a little trickle of air at 40psi and is fully open at 55psi. The "early release" problems I was describing earlier seem to have come from the faulty pressure gauge. The safety valve is functioning as intended, but I'm still going to send it away to have it looked at, just in case!

Last discovery: Barring the two previous issues, everything else seems to be in good condition. No leaks were found and the loco will hold pressure nicely. Pleased with that one!

I'll hold off steaming the engine until the two items above are rectified. Many thanks for your suggestions!
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Pleased you headed the advice :)
 
tac foley said:
Has ANYBODY here, EVER witnessed a boiler in our area of model steam locomotion that actually 'burst'?

In over 45 years, I've never even heard of it happening.
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As an impetuous teenager, I once blew the end off a Mamod boiler. I can't remember how I did it, but a bicycle pump was involved. I may have screwed it into the safety valve bush...
In my defence, there was evidence of wasting on the area of the boiler where the end cap detached itself...
 
JimmyB said:
Yes, I know a story about a Nimrod, minor fuel leak not an issue - until it was. Every big disaster wasn't an issue, till it was, hindsight and all of that stuff.
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Just wait till AI takes over, we are sleepwalking into catastrophy.
 
Regarding the Accucraft "safety valve" I have several and they are rather poor devices IMHO. Leak and sputter at half the desired pressure. Notorious for that. Here in the US, I have replaced every one of my stock Accucraft pop valves with one from Jim Weebee. Beautiful precise things. Just what you described in your first post. a robust pop at pressure. They are distributed here by the train department. You will also probably need an adapter to fit the thread on your boiler. Highly recommended if you can obtain some.

thetraindepartment.com

WeeBee Safety Valves and Adapters

Working pop safety valves handmade and tuned for accurate pop and reset pressures. For Accucraft and Roundhouse you will need the appropriate adapter which is not included with the valve purchase. M10 adapters for most Accucraft models, many 1/32 and newer models will thread a M5 valve directly...
thetraindepartment.com

Jerry
 
GERARD (JERRY) BOHLANDER said:
Regarding the Accucraft "safety valve" I have several and they are rather poor devices IMHO. Leak and sputter at half the desired pressure. Notorious for that. Here in the US, I have replaced every one of my stock Accucraft pop valves with one from Jim Weebee. Beautiful precise things. Just what you described in your first post. a robust pop at pressure. They are distributed here by the train department. You will also probably need an adapter to fit the thread on your boiler. Highly recommended if you can obtain some.

thetraindepartment.com

WeeBee Safety Valves and Adapters

Working pop safety valves handmade and tuned for accurate pop and reset pressures. For Accucraft and Roundhouse you will need the appropriate adapter which is not included with the valve purchase. M10 adapters for most Accucraft models, many 1/32 and newer models will thread a M5 valve directly...
thetraindepartment.com

Jerry
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Here in UK we can get Jim Saunder's Wee-Bee brand SVs from Simon Whenworth of 'Anything Narrow Gauge' - and fine adjustment gas valves and throttles - specific to your model.
 
I am not sure why people worry so much about commercially made silver soldered copper boilers from the likes of Roundhouse and Accucraft operating at 40/60 psi (0.7bar/litre) I have seen a water gauge glass break and the resultant release of steam is not very impressive or dangerous. The volume is just too small.

The aerosol type of can I use for the Butane gas is made of flimsy aluminium with a crimped end as is full of highly inflammable gas. When full, it is around 140 psi with a volume of 0.27 litre (2.6 bar/litre) Testing these to destruction, they typically fail at around 350 psi when the crimped end fails, but no-one seems to worry about these.
 
JimmyB said:
Bar/litre, no such animal.
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For anyone wanting to know more about 'bar litre', a quite good explanation is in the
which can be found (along with other places) on the 16mm association web site, under resources, then pressure testing.

The 'bar litre' is used as one would expect, to work out volume times pressure, and therefore, how strenuous the testing of a pressure vessel needs to have been carried out. Boilers over the 3 bar litre category which relates to garden railways etc., should be tested more regularly, but as boilers under 3 bar litre is the standard that we as garden railway folk should to conform to.

It was as I recall, formulated with co operation from,

10¼” Gauge Railway Society, 7¼” Gauge Society, Association of 16mm Narrow Gauge Modellers, Gauge 1 Model Railway Association, Midland Federation of Model Engineers, Model Power Boat Association, Northern Association of Model Engineers, Southern Federation of Model Engineering Societies, and Walker Midgley Insurance Brokers.

The G gauge society were not involved at the time, (I think they were going through their split at the time, so had other things on their minds, resulting in half the local group I was in suddenly not receiving emails/meet up notifications etc.). Thankfully they seem to have got over that now, and all seems well again. However even though they did not officially take part in the formulation of the regulations, some members were involved as they were also members of the other societies, and it is now the standard that we all should work to when building or running our live steam trains etc.

There are other parts which relate to gas tanks, and larger boilers which were formulated and approved at the same same time, should that be your area of interest.

I hope that helps to clarify matters re this.

David
 
RDFMTS2 said:
For anyone wanting to know more about 'bar litre', a quite good explanation is in the
which can be found (along with other places) on the 16mm association web site, under resources, then pressure testing.

The 'bar litre' is used as one would expect, to work out volume times pressure, and therefore, how strenuous the testing of a pressure vessel needs to have been carried out. Boilers over the 3 bar litre category which relates to garden railways etc., should be tested more regularly, but as boilers under 3 bar litre is the standard that we as garden railway folk should to conform to.

It was as I recall, formulated with co operation from,

10¼” Gauge Railway Society, 7¼” Gauge Society, Association of 16mm Narrow Gauge Modellers, Gauge 1 Model Railway Association, Midland Federation of Model Engineers, Model Power Boat Association, Northern Association of Model Engineers, Southern Federation of Model Engineering Societies, and Walker Midgley Insurance Brokers.

The G gauge society were not involved at the time, (I think they were going through their split at the time, so had other things on their minds, resulting in half the local group I was in suddenly not receiving emails/meet up notifications etc.). Thankfully they seem to have got over that now, and all seems well again. However even though they did not officially take part in the formulation of the regulations, some members were involved as they were also members of the other societies, and it is now the standard that we all should work to when building or running our live steam trains etc.

There are other parts which relate to gas tanks, and larger boilers which were formulated and approved at the same same time, should that be your area of interest.

I hope that helps to clarify matters re this.

David
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I was a BS registered inspector under PSSR 2000, and used to work on vessels up to 6,000 psi. In the document the term Bar Litre is only used twice, on the front cover and in para 1.2, not having any definition, and is just used a term to describe small boilers. Under PSSR 2000 the term is not used at all.
 
JimmyB said:
I was a BS registered inspector under PSSR 2000, and used to work on vessels up to 6,000 psi. In the document the term Bar Litre is only used twice, on the front cover and in para 1.2, not having any definition, and is just used a term to describe small boilers. Under PSSR 2000 the term is not used at all.
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Fair enough Jimmy, I was just saying how it relates to our small steam locos. David
 
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