Making Safety Valves.

[goldstar31]

Jennifer

Whilst looking for 'Flash steeam' information, I ran across D.M Hughes of his very simple tailstock turret.

Model Engineer July2 1953-- if you must

Interested??

Norm

 

[tomfilery]

Hi Tony,
Could you please say a little about the ball seating jig you show in post#14. I expect it's use is fairly self evident, however, what wasn't clear to me was how you determine the "maximum clearance" - by the angle of the valve stem, by measurement with feeler gauges, or something else and what the 2.9 stamped on the jig referring to?
I ask the questions because I understand that the clearance (i.e. how far the ball protrudes from it's carrier) is critical to the correct operation of this type of safety valve.
Nice work and an educational post, as ever.
Regards Tom

 

[Tony Bird]

Hi Tom,

Sorry for the delay in replying to your query but only got back to the UK early this morning and for some reason didn't get a notification of your post while away.

Could you please say a little about the ball seating jig you show in post#14. I expect it's use is fairly self evident, however, what wasn't clear to me was how you determine the "maximum clearance" - by the angle of the valve stem, by measurement with feeler gauges, or something else and what the 2.9 stamped on the jig referring to?
I ask the questions because I understand that the clearance (i.e. how far the ball protrudes from it's carrier) is critical to the correct operation of this type of safety valve.

The 2.9 on the jig refers to the size of the hole that the ball sits in. The size hole means that a 5/32" (4 mm ish) ball will be resting in it on its radius. This measurement is arrived at by dividing the balls diameter 3,969 mm by 1.41 which gives 2.815 mm and I usually use the next drill size up. I have always done this when making safety valves, I must have read it in the ME in the dim and distant, it seems to work. The clearance of the cup needs to be very little about 10/15 degree lean or as little as can be managed and the ball still seats. I seem to remember that the article I read about making them suggested 5 to 10 thou clearance possibly to allow for wear?

I hope this helps.

Regards Tony.

 

[tomfilery]

Tony,

Many thanks for the response - crystal clear, thank you.

I'd picked up from the Ceramic Burner thread that you were in Madeira, so wasn't expecting an immediate answer.

Regards Tom

 

[Lois Flakes]

Yeah!! These are the impressive boilers.

 

[Steamchick]

Just picked-up on this thread - a subject "of great interest" to me:
Here are Gordon Smiths designs of Safety Pressure Relief valves for STEAM boilers: (I hope the pdf works for you?).
Also, I have a copy of Live Steam and outdoor railroading - Jan-Feb 2007 back-issue, with an article by Kozo Hiraoka and his designs of Pop-type Safety Relief valves. (As you can buy this from the publishers I cannot reproduce it here - Copyright stuff!).
I have recently converted Simplex loco boiler Safety Relief valves from the original design (Open from 60psi to maintain <88psi with full fire steaming - Re-closing somewhere around 55psi!) to a design replicating Gordon Smith's SV#3 so it now operates at about 81psi and maintains pressure below 88psi, closing again around 79~80 psi.
I opened-out the top cap vents to match G.S.'s. Also made a shroud valve and stem to make the annulus around the ball valve the same as G.S.'s. (0.264"OD). Then tuned the spring compression to set it at the pressure for "full-blow" at 87psi. (Just less than the required 80psi + 10% = 88psi). Happy!

Enjoy.
K2

 

[Steamchick]

A late addendum: re: Safety Pressure relief valves.
To record my efforts, I have written a screed (for my later reference when I forget it all?) about the Simplex loco valve mods.
See attached.
If anyone enjoys this, it simply shows I am not the only odd-ball here!
K2