[modeleng] Re: FW: Rail Accident Investigation alert: RAIB investigation - Kirklees

G'Day Barrie,

Once the decompression starts, the water expands as it gasses off, and 
floods the crown. It then gasses of again, but it only turns to very wet 
steam. If the flow is good enough, then it will wet the fire. If not, then 
it will, as you say, starve the fire of oxygen by giving it steam instead. 
It's a really interesting process. As long as the pressure wave isn't tooooo 
great, the normally safe boiler won't fail. And to failure from a fusible 
plug going is almost too rare to think about.... Plus, the boiler needs to 
be on it's way out due to thinning of the plates.......
But there is normally some water carry over unless the wrong alloy has been 
used.......

The alloy is supposed to melt at only 21 - 66°C above the wet steam temp' of 
the max pressure of the boiler...... It shouldn't take much to melt 
it....... But in our models, the turndown rate is so high, we should stick 
to using pure tin.


Cheers,

Phill.

--------------------------------------------------
From: "Barrie Purslow" <bpduo@xxxxxxxxxxxxx>
Sent: Friday, July 29, 2011 11:20 PM
To: <modeleng@xxxxxxxxxxxxx>
Subject: [modeleng] Re: FW: Rail Accident Investigation alert: RAIB 
investigation - Kirklees

> Hello Phill,
>
>> and if correctly fitted will also dump lots
>> of water onto the fire.....
>
>
> I don't think it will - it will almost certainly have failed because there
> ain't no water above it!
>
> Even if here was water above the plug it would immediately flash into 
> steam
> as it entered the firebox - as it does when a boiler is blown down.
>
> Regards,
>
> Barrie
>
>
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