captive gauge glass valves

This topic has 8 replies, 5 voices, and was last updated 22 April 2015 at 21:03 by julian atkins.

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19 April 2015 at 12:55 #186958
Metatsteam1
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@metatsteam1
Can anyone help with links to drawings for modifying published gauge glass/ blower valve design's to the type that cannot be screwed out when in steam. I have thought of a couple of ways to modify them but would like to see if there is a standerd way that is acceptable to the boiler inspector.

Matthew
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19 April 2015 at 12:55 #7579
Metatsteam1
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@metatsteam1
20 April 2015 at 07:26 #187030
julian atkins
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@julianatkins58923
hi matthew,

ive sent you a PM.

cheers,

julian
21 April 2015 at 19:34 #187275
duncan webster 1
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@duncanwebster1
If your inspector is failing a boiler because it doesn't have captive valves he is exceeding his authority. This was discussed in ME some time ago.
21 April 2015 at 20:15 #187283
Metatsteam1
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@metatsteam1
Hello Julian

Sorry but I'm not sure what you mean by PM

Hello Duncan

Thanks for that. I was under the impression that they were a requirement now. I have not had chance to speak to whoever will test my boiler yet but I intend to fit captive valves as I think they are a good idea.

Matthew
21 April 2015 at 20:17 #187284
JasonB
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@jasonb
Matthew, if you look along the top of the page in the green bar you will see "inbox" click that and you will see any Private mesages. There will also be a flashing envelop in the top right under my friends which will also open your messages

Edited By JasonB on 21/04/2015 20:17:51
22 April 2015 at 18:18 #187418
Metatsteam1
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@metatsteam1
Thank you Jason . I hadn't noticed the bar at top of the page.

Hello Julian

Thank you for the link to your photos. My idea is to increase the thread size then reduce the spindle diameter and fit a gland nut that will prevent the valve screwing out. This looks ok when drawn, I` ll have to make one to see if it looks right.

Regards

Matthew
22 April 2015 at 19:21 #187421
Neil Wyatt
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@neilwyatt
Just a random thought. Should the gland nut have a finer thread than the valve spindle, to stop them unscrewing together?

Neil
22 April 2015 at 21:03 #187425
julian atkins
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@julianatkins58923
hi matthew,

what you propose is as neil suggests not a good design. you need instead a double ended female connector that restricts the spindle from being unwound and into which the spindle is screwed.

both my last 2 locos have all captive fittings as per the 'advised' section of the boiler regs. the regs are a bit silly as 'advised' for backhead fittings, but ive made the boiler blowdown valves all captive as well though on one loco the boiler blowdown is on the backhead and on the other on the sides of the boiler.

captive valves require a bit of extra work as the 'squre' for the fitting of the handles must of necessity be smaller so this involves a bit of fine work and close tolerances, and the concentricity of the parts is crucial to good and reliable operation.

however i have also seen idiots unscrew blower valves completely with dramatic results, so well worth the extra effort IMHO.

cheers,

julian
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