[modeleng] Re: FW: Rail Accident Investigation alert: RAIB investigation - Kirklees
- From: "R.L. Roebuck" <rlr20@xxxxxxxxxxxxxxxx>
- To: modeleng@xxxxxxxxxxxxx
- Date: Fri, 29 Jul 2011 16:03:49 +0100 (BST)
Hi there Phill,
Interesting - does it make any particular noice as it leaves the
internally shaped plug (ie could you or would you shape it to make an
audible noise)?
Or would you normally expect the noise of the fire being put out by steam
to be enough (no water above the crown, which is why the plug melts)?
Also, is there any spec on rate of decrease of boiler pressure (ie safety
valves are specified to not allow more than a 10% rise in boiler pressure
with it generating steam at full 'wack', presumably where you have
boiler plates sagging you might want to say: must half boiler pressure
in X seconds)?
Yours,
Rich.
On Fri, 29 Jul 2011, Phill Smith wrote:
> G'Day Rich,
>
> I don't know if you have ever seen a plug go, because while the steam is in
> the firebox, it's invisible. Due to the heat it is still in a purely gaseous
> form. It's not until it hits the relatively cold air outside the firebox and
> chimney, that it condenses enough to be seen as that lovely white cloud of
> water droplets, that we call steam.
>
> So in defence of that lazy bloody train crew (including the trolley lady and
> the guard) it would have been impossible to see the steam issuing from the
> fusible plug had it let go. Also, it could also have been a very UNSAFE act
> to have to firebox door open during such an event, as burning coals could
> easily have been blown out of the open door and onto a person..... The steam
> leaving fusible plug is normally doing so at 300 m/s for the pressures that
> we work at in the boiler...... That's assuming that the plug has the correct
> internal shape, as per AS1732, and if correctly fitted will also dump lots
> of water onto the fire.....
>
> If anyone wants a copy of it, let me know.
>
>
> Cheers,
>
> Phill.
>
> --------------------------------------------------
> From: "R.L. Roebuck" <rlr20@xxxxxxxxxxxxxxxx>
> Sent: Friday, July 29, 2011 5:57 PM
> To: <modeleng@xxxxxxxxxxxxx>
> Subject: [modeleng] Re: FW: Rail Accident Investigation alert: RAIB
> investigation - Kirklees
>
>> On Fri, 29 Jul 2011, Phill Smith wrote:
>>
>>> Not being able to notice the fusible plug letting go
>>> is the most serious thing.
>>
>> Actually now that you say that, I'm looking at the report again, because
>> it doesn't actually say that, it says (and I may be being pedantic here):
>>
>> "The melting of the fusible plug in the firebox was not noticed by the
>> train crew."
>>
>> ...I think we know what they mean, but actually you don't as a driver or
>> fireman see the process of melting taking place...you see the subsequent
>> escape of steam...it could be that it had begun to melt at its
>> extremeties, but not in the middle, and no steam had been released yet, in
>> which case I wouldn't expect them to know.
>>
>> (As otherwise it would imply it was inadequate.)
>>
>> Also locomotive crew should notice, but the train crew...the gaurd, the
>> lady that serves tea in the buffet car, the toilet attendent.
>>
>> Not that I'm any kind of language expert (and my spelling and grammar are
>> attrocious) but I do wonder who wrote this report - there is certainly no
>> name put to it, and the accuracy of the words used don't seem that
>> technically correct...certainly not correct enough that I would be damming
>> this person just yet (innocent until proven guilty...then a kick in the
>> pants!)
>>
>> Yours,
>>
>>
>> Rich.
>> MODEL ENGINEERING DISCUSSION LIST.
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