Saftey valves

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Saftey valves

Post  northburrell on Fri 05 Feb 2010, 4:28 am

Hi everyone,

Did anyone take there safty valves apart to paint? by this I mean unscrew the spring?

I painted mine at the weekend but was stupid enough to loose count of the turns as I was taking the nut off the bottom.. Sleep I was half asleep!

Does anyone know ruffly how many turns it was set at? I was going to set it up on the enigne in steam but it's a bit of a pain to do as the engine will need to put in steam then drop the fire, change setting, steam, change, steam, and so on...

Dean is there an easy way for me to get a rough settng on the bench? did you have a set number of turns you would set them to and then fine tune? I'm not too fussed if the engine blows off too low like 80-90psi but I dont want it to be blowing off at over 100psi.

Any info greatfull.

Thanks

Jo

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Re: Saftey valves

Post  LilyJack on Fri 05 Feb 2010, 9:57 am

Hiya Northburrell,

Just a thought but, if you've got a compressor or know someone who has one, can you not rig the valve up to the airline, set the air at 80-100psi and then adjust using air pressure to save you sodding about with steaming then dropping the fire out etc etc?

LilyJack Cool

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Re: Saftey valves

Post  hughb on Fri 05 Feb 2010, 11:53 am

HI JO

When I was at STW Ian was testing the 4" safty vavles .Thay are screwed on to a plate that lets the air in it is done on the mig as the compresser is working to cncs .
Here are two pics for you I have left them big so you can see what is going on .I hope that this will help.



In the first one you can see the plate that has the air going in.
Hugh

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Re: Saftey valves

Post  northburrell on Wed 10 Feb 2010, 8:29 am

Hi Hugh, Hi lillyjack,

Thanks for you comments there both good ones.. I dont have a compressor but I have a friend that does but i'm not sure where it would conect to as the saftey valves will be on the top of the cylinder where the plate that STW gave us for air running would be.. hmmm I can set then with water too by hydraulicing the boiler again and wait for water to spray out the saftey valves.. or I might be able to set the engine in full forward and run the crank backwards to what it should run, this should pump air from the piston into the boiler as does with my loco and my minnie but this is very dangerous as you need the reg open for this to work!!

Thanks for the advice guys.

Jo

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Re: Saftey valves

Post  LilyJack on Wed 10 Feb 2010, 9:04 am

Hmmm, sorry about that NorthBurrell, Having not seen the safeties I've wrongly assumed that they were independant of the base, having looked at HughB's picture, I can see that they're obviously not. Well, if you know anyone with a calibrated pressure gauge, you can always wind the springs out (assuming then that this will mean they blow off at a lower pressure), run up steam in the boiler then turn them in a bit at a time until 100 psi blow off is achieved?
Looks like STW have a setting jig that the whole unit bolts onto huh!.

Actually, thinking about it, it'd be a damn sight safer to connect the boiler up to ya mates compressor wouldn't it, then wind the springs out to blow at the set pressure in situ?

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Re: Saftey valves

Post  northburrell on Wed 10 Feb 2010, 11:21 am

The STW method of setting up the springs is very good as you can get to the nut at the bottom of the saftey valves.. I wont be able to get to this nut when it's on the engine as it gets covered up..

I'll get it sorted one way or the other It was just to see if anyone had a rough number of turns to put on the nut so it's kinda near the right setting..

I have gone from a few pictures of the saftey valves in other threads on here as I could see how much of the bolt bit that holds the spring at the base sticks out the top of the flange that holds the safteys on. I then turned it back half a turn just to make sure it blows off under 100psi..

I watched the vid of Big al's engine in steam at STW and it looks like it was blowing off under 100psi (if I was seeing the gauge correct!) It's just a pain to have to set them up the long way round but I guess thats how most scratch built models have to be setup...

Ta

Jo

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