Correct way to read the sight glass

[JimmyB]

There are in our scale boilers and boilers. Generally it is considered that boilers built for normal 40psi (3 bar) running and tested at double that pressure tend to not blow up. Greater caution is taken with boilers that operate above that and the warnings are very appropriate. In fact annual boiler testing is required as mandated in the 16mm society Boiler Testing Notes. Closer attention is now also given with gas tanks than was the case when I used to carry out Boiler Testing with my local 16mm group prior to year 2000. The notes linked below are well worth a read if you have a live steam locomotive.

https://www.16mm.org.uk/?s=Boiler+testing

Having been a pressure vessel inspector and tester with BSI authority for vessels up to 6000 psi, though good practice as detailed in the article, it can hardly be called pressure vessel testing, it is just a safety device test.

 

[David Price]

Good set of notes - only thing missing is how the pressure gauge is determined as accurate.

The 7/8" Decauville I purchased had an obvious fault when it arrived (the gauge was stuck on 100psi) but others may not be as obvious.

I check my gauges by connecting a compressed air supply to the boiler which has an accurate gauge on the regulator - I can also test safety valves this way before a steam test (ie: set the air supply to 45psi and see if the safety lifts) - however this does not replace a steam test as detailed in the 16mm Society's notes!

A compressed air connection is also useful for setting valve timing!

And not all small boilers operate at 40psi - my Bowande Falk No.1's boiler is certified for 80psi (safety lifts at 70psi).







(Just spent almost a week sorting out its valve timing - it now runs properly in both directions).


Cheers,

 

[Rhos Helyg Loco Works]

... as mandated in the 16mm society Boiler Testing Notes. ...

We could get in to a whole swamp of discussing 16mm COMPANY (it has not been a society for many years) boiler testing, including competency of testers, but I'll take issue with "mandated", sorry. In the code, the word discretionary word "should" is used FAR too often for my liking, such as "The gauge range should be approximately 1.5 x the pressure of the test,", "Any faults detected should be rectified before increasing the pressure." and "Anything but the slightest movement or distortion observed should be viewed with great suspicion". There are loads of them, and it even says (P2) "‘Shall’ is mandatory, ‘should’ is advisory.". There are many things I should do (eat better, get more exercise, lose weight, etc.) that never happen because nobody has told me - yet - that I MUST.

The Accucraft factory boiler test certificate for my NGG16 says: Working pressure 180psi, Test pressure: 60psi. Not worth the paper...

Thanks to all for the boiler failure stuff.

 

[David Price]

Set your safety for 180psi Tony - light up the engine and stand a long way away......................

This locomotive (T251 - Walkers #276 of 1917) runs a boiler pressure of only 175psi - and is inspected every 12 months by a qualified Government boiler inspector.



And it runs a calibrated pressure gauge serviced by an instrument company qualified to certify the accuracy (I have a full size gauge that is certified and can be used with my pump for hydro-static testing of boilers including a boiler like that in T251).

The only advantage of a manufacturer's boiler ticket would be in the case of an insurance claim!

 

[dunnyrail]

Good set of notes - only thing missing is how the pressure gauge is determined as accurate.

The 7/8" Decauville I purchased had an obvious fault when it arrived (the gauge was stuck on 100psi) but others may not be as obvious.

I check my gauges by connecting a compressed air supply to the boiler which has an accurate gauge on the regulator - I can also test safety valves this way before a steam test (ie: set the air supply to 45psi and see if the safety lifts) - however this does not replace a steam test as detailed in the 16mm Society's notes!

A compressed air connection is also useful for setting valve timing!

And not all small boilers operate at 40psi - my Bowande Falk No.1's boiler is certified for 80psi (safety lifts at 70psi).





View attachment 344580

(Just spent almost a week sorting out its valve timing - it now runs properly in both directions).


Cheers,

We had a calibrated pressure gauge that was tested each year and the loco gauge confirmed to that at hydrolic pressure. No doubt someone will say that water test is not the same but there it is. This could arguably be one of the failures of the current “self testing regime” and I would not disagree with that view. Pressure gauge was tested to ensure that blow off appeared at test pressure 40psi for Roundhouse thus ensuring both were similar. But both can go out of synce over time. Thus a proper test advisable. Whether your view if the 16mm or miniature engineers society falls in line with the listed stuff is up to you, but IMHO is better than nothing.

 

[dunnyrail]

We could get in to a whole swamp of discussing 16mm COMPANY (it has not been a society for many years) boiler testing, including competency of testers, but I'll take issue with "mandated", sorry. In the code, the word discretionary word "should" is used FAR too often for my liking, such as "The gauge range should be approximately 1.5 x the pressure of the test,", "Any faults detected should be rectified before increasing the pressure." and "Anything but the slightest movement or distortion observed should be viewed with great suspicion". There are loads of them, and it even says (P2) "‘Shall’ is mandatory, ‘should’ is advisory.". There are many things I should do (eat better, get more exercise, lose weight, etc.) that never happen because nobody has told me - yet - that I MUST.

The Accucraft factory boiler test certificate for my NGG16 says: Working pressure 180psi, Test pressure: 60psi. Not worth the paper...

Thanks to all for the boiler failure stuff.

So what do you do for your NGG16?

 

[Rhos Helyg Loco Works]

So what do you do for your NGG16?

Not sure what you mean... what "should" I do, other than use it?