Fusible Plugs

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Fusible Plugs

This topic has 20 replies, 10 voices, and was last updated 30 December 2015 at 19:05 by Mark P..

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29 December 2015 at 09:58 #218233
Deltic007
Participant
@deltic007
Got to make one of these for my next project,is normal soft solder Ok or am i better with white metal or lead?
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29 December 2015 at 09:58 #7936
Deltic007
Participant
@deltic007
29 December 2015 at 10:01 #218235
JasonB
Moderator
@jasonb
Use lead
29 December 2015 at 10:03 #218236
Deltic007
Participant
@deltic007
Any reason Jason
29 December 2015 at 10:47 #218248
Martin Connelly
Participant
@martinconnelly55370
Lead has a higher melting point than eutectic solder (60 40 mix) so may be a consideration.

Martin
29 December 2015 at 14:21 #218293
mark costello 1
Participant
@markcostello1
If there is a specific temperature You need to protect against the alloy might have to be chosen a little more carefully. If the results are generic then the material could also be generic.
29 December 2015 at 17:02 #218315
JasonB
Moderator
@jasonb
Actually will depend a bit on the working pressure of the boiler, tin can be used and is prefered in the Australian code for boilers under 150psi with lead for ones above that. There is a possibility of the tin crystalizing so should be replaced anually. Pure lead is also easier to get hold of than tin. As in all cases boiler related talk with whoever will be testing the boiler.
29 December 2015 at 19:14 #218337
the artfull-codger
Participant
@theartfull-codger
I allways remove my fusible plug each yr & it there's any sign of movement I re-metal it with either high melting point soft solder or melted sheet lead [4" foster steel boiler.]
29 December 2015 at 19:17 #218338
Bob Youldon
Participant
@bobyouldon45599
Hello,

As someone has mentioned it is essential to use a material suitable for use at your desired working pressure plus a suitable additional additional excess. I would discuss the design and materials with your boiler inspector prior to making the thing. Should it be for a pressure vessel in the UK I'd suggest a look at the green book on the subject of fusible plugs. Ideally plugs should be removed for examination each year, primarily to ensure the waterside hasn't become encrusted with scale as this will act as an insulator and the fill material hasn't started to sink through the plug. I understand following the dropping of a plug the boiler should be subjected to hydraulic test.

All in all, I consider them a damm nuisance in model use but that's only my opinion.

Regards,

Bob
29 December 2015 at 22:26 #218364
stan pearson 1
Participant
@stanpearson1
I played safe and bought one from Steam Fittings as there is so much to consider when making one

Stan
30 December 2015 at 10:46 #218417
nigel jones 5
Participant
@nigeljones5
Question – has anyone actually seen first hand a plug be used for its intended purpose i.e. melting to save boiler/explosion risk?
30 December 2015 at 15:10 #218500
the artfull-codger
Participant
@theartfull-codger
Everyone who owns an engine should have seen one, I re-leaded one for a friend who had a full size aveling roller, as said previously I remove mine every yr & if there's a sign of a slight melt then I re-do it & I allways carry a spare to any rallys,[never needed it btw!!] made both mine out of a bronze chisel as used in the oilworks up here & I check the threads in the boss oif the boiler as well.
30 December 2015 at 17:17 #218523
Neil Wyatt
Moderator
@neilwyatt
Posted by fizzy on 30/12/2015 10:46:14:

Question – has anyone actually seen first hand a plug be used for its intended purpose i.e. melting to save boiler/explosion risk?

The consequences of a dry top to the firebox are disastrous in full size.

I have heard of the plug going on a low boiler but never seen it happen.

Neil
30 December 2015 at 17:33 #218525
the artfull-codger
Participant
@theartfull-codger
Fizzy,I misread your post I thought you meant has anyone seen a fusible plug!!, I've seen a couple go at rallys,when going down a steep hill is the worsed, as all the waters down the front end so it must be well full, uphills ok as it's all over the crown, don't know about damage I suppose it all depends how quick you can drop the fire & how long it's been exposed, one of the ones I saw just replaced the plug with a replacement perhaps one of the boiler inspectors on here might care to comment, adverts long ago for drivers used to say"plug droppers need nor apply"
30 December 2015 at 17:59 #218534
Mark P.
Participant
@markp
When I worked for a model engineering company we would generally replace the fusable plug on railway locos with a solid bronze plug.
Mark P.
30 December 2015 at 18:18 #218540
Deltic007
Participant
@deltic007
Why would you do that Mark?
30 December 2015 at 18:23 #218543
Mark P.
Participant
@markp
According to the boss”if one happens to fail you have to remove the boiler to replace it” those were his words! Personally I would fit one.
Mark P.
30 December 2015 at 18:24 #218544
Deltic007
Participant
@deltic007
The reason i originally posted was because i am building a New Zealand designed loco and it has one fitted.I will have to consult our boiler inspector to see if it is OK to omit it.
30 December 2015 at 18:33 #218545
Mark P.
Participant
@markp
I suppose that if you can access it easily through the firebox and grate, if you have a removable grate I would fit one. But see what the boiler inspector says.
Mark P.
30 December 2015 at 18:54 #218549
Deltic007
Participant
@deltic007
What material would you recommend? Drawing actually says soft solder.
30 December 2015 at 19:05 #218552
Mark P.
Participant
@markp
As Jason says use lead,or speak to the boiler inspector.
Mark P.
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