Is my safety valve functioning correctly?

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DannyTheElfman

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Hello again!

My apologies for starting another thread just a couple of days after my previous topic, I'm new to live steam so I have quite a few questions.

This one is regarding the safety valve and it's operation in my Accucraft Edrig. Basically, I was expecting for the boiler to reach 55-60psi and the safety valve to sort of "pop" open. But this doesn't really happen. Instead, At about 25psi the safety valve starts to release just a little of steam, at 30psi a little more steam leaks out, and at 35psi a little more, and so on and so forth until about 60psi. So instead of that single pop I was expecting, it's a gradual increase between 25 and 60psi. I could not identify a one single moment when the valve went from closed to open.

Is this correct operation? It does it's job, the pressure never goes over 60psi. But it seems like this wastes a lot of steam when it doesn't need to be?

Many thanks
Dan
 
Short and sweet, I like it! So what can I do to fix it? I've replaced the O-ring already (with these to be precise). It looked clean inside the barrel, no debris or anything. Maybe just tighten it down a little more?
 
In the 12" to the foot world...
You would 'tap it gently' :giggle: with a spanner..
It would then either seal, or blow-off enthusiastically! :blush:

If it was mine, I would flush the boiler out. Perhaps blow-through the safety valve with a foot-pump?
But not 'tighten' or mess with the adjustment.

I would then test again, and if no improvement, wander to a local group / model engineers, and get the hive-mind to give it a hard looking at.

But let's see what someone who knows what they are on about, says first..

PhilP.
 
I do not know this one specific, but basically there are two type of safety pressure valve, one like you mention that just pops off, drops the pressure to a percentage below the rated value, then seals again (pop valve). The other types starts to lift just before the safety pressure, becoming more open as the pressure rises, and then continuous to release pressure (seeps) until below the safety pressure.
 
I would seriously think about what Rhos and Philp say. Go to your nearest 16mm Association meet or your local model engineering society and get advice from there. You will get far more enjoyment out of your loco when running with other like minded folk. Where abouts are you in the UK?
 
Is it the internal O-ring you have replaced? If so the warnings about dismantling and adjusting might be a bit late! There is a tiny tiny O-ring inside and that will almost certainly be causing the problem. The ring goes hard with age and ceases to function correctly. Edrig is not a new model (introduced 2010 I think) so age may well be the causal factor. I used to have correct size replacement rings but they are long gone, so I cannot help you. One of the Accucraft repair agents (Repairs & Services | Accucraft UK Ltd) will be able to help, I am sure.
 
Rhos Helyg Loco Works said:
Is it the internal O-ring you have replaced? If so the warnings about dismantling and adjusting might be a bit late! There is a tiny tiny O-ring inside and that will almost certainly be causing the problem. The ring goes hard with age and ceases to function correctly. Edrig is not a new model (introduced 2010 I think) so age may well be the causal factor. I used to have correct size replacement rings but they are long gone, so I cannot help you. One of the Accucraft repair agents (Repairs & Services | Accucraft UK Ltd) will be able to help, I am sure.
Click to expand...

Dave Mees of Abbeybach Engineering Services Ltd is your man - one of the Accucraft service agents. He'll pre-test the replacement the replacement to the pressure as defined in the manual of the loco concerned.

Or you can buy a Wee-Bee safety valve from Simon Wentworth [anything Narrow Gauge] for about thirty English flarps. If you go the Mees route, tell him I sent you - we go back a long way.
 
That's why you have a pressure gauge, as well..

But our little-dragon's, will tend to go psssssssssst! If something untoward happens, and not BANG! as in the 12" to the foot, world.

PhilP.
 
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