THE TEST RESULTS ARE IN
- Trainman4602
- Posts: 3482
- Joined: Sat Oct 16, 2004 9:26 pm
- Location: New Jersey
THE TEST RESULTS ARE IN
I was finally able to test the safety valves mounted to a tee using one outlet in the boiler.
The question in my mind was. Will both pop off while mounted in the same outlet using a tee setup.
Well here are the results.
http://www.youtube.com/watch?v=YuNSU5wyVtE
The question in my mind was. Will both pop off while mounted in the same outlet using a tee setup.
Well here are the results.
http://www.youtube.com/watch?v=YuNSU5wyVtE
ALLWAYS OPERATING MY TRAIN IN A SAFE MANNER USING AUTOMATIC AIR BRAKES
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Re: THE TEST RESULTS ARE IN
Good to know!
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Re: THE TEST RESULTS ARE IN
Thanks, Dave for taking the time to research this question.
Ralph
Ralph
Ralph M. Reese
St. Augustine, FL
Under Construction
LE Pacific
Allen 10 Wheeler
St. Augustine, FL
Under Construction
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Allen 10 Wheeler
Re: THE TEST RESULTS ARE IN
Well, without watching the video, I would think that if the safeties are set at different pressures, they would NOT go off at the same time.
Now, to go watch how Dave's video to see the answer
Now, to go watch how Dave's video to see the answer
Re: THE TEST RESULTS ARE IN
Great demo Dave. I am just wondering though, when the first safety goes off, can the drop in pressure in the pipe affect the other safety? I guess I am using a water line as comparison. If you have two faucets on a say 1/2" water line, you open one and have great pressure, but if you open the 2nd, the water pressure drop at the first faucet opened. I know I am probably missing a pertinate piece info in the equation.
Fred
Fred
Re: THE TEST RESULTS ARE IN
I think the key points are that the viscosity of water is larger than that of steam, so there is more drag on the water flow, and mostly that the length of pipe is much greater in the water supply case. A longer pipe run, upstream of where the two lines to the faucets split off, means a large pressure drop.FredR wrote:Great demo Dave. I am just wondering though, when the first safety goes off, can the drop in pressure in the pipe affect the other safety? I guess I am using a water line as comparison. If you have two faucets on a say 1/2" water line, you open one and have great pressure, but if you open the 2nd, the water pressure drop at the first faucet opened. I know I am probably missing a pertinate piece info in the equation.
Fred
- Bill Frensley
Re: THE TEST RESULTS ARE IN
...I would think as long as the cross-sectional area of the pipe tap off the top of the steam dome is sufficiently larger than the total relief area of the (2) safety valves, there wouldn't be any problem. As long as the piping arrangement with the (2) properly sized safety valves lifted does NOT allow the boiler pressure to continue to climb...it would appear that piping concept provides a workable "system".
Safely conducted experimentation is always a good way to prove (or disprove) a theory or concept. Thanks for sharing. Carl B.
Safely conducted experimentation is always a good way to prove (or disprove) a theory or concept. Thanks for sharing. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
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I don't walk on water...I just learned where some of the stepping stones are!
I love mankind...it's some of the people I can't stand!
Re: THE TEST RESULTS ARE IN
Dave,
In the video You said one safety is 120 the other is 125, yet with both safeties lifted you had 130 in the boiler, that means the two safeties don't have enough volume for the steaming capacity of your boiler. Which can be why the second safety is able to lift with the first one open.
David Rohrer
In the video You said one safety is 120 the other is 125, yet with both safeties lifted you had 130 in the boiler, that means the two safeties don't have enough volume for the steaming capacity of your boiler. Which can be why the second safety is able to lift with the first one open.
David Rohrer
We the willing, led by the unknowing, have been doing so much with so little for so long that we are now qualified to do anything with nothing.
Re: THE TEST RESULTS ARE IN
I considered that as well, but I'm of the opinion that the problem isn't the safeties, but the limit created by the use of the 1/8" supply. A test with the 1/4", were it possible, would either dispel or reinforce that notion.srrl5 wrote:Dave,
In the video You said one safety is 120 the other is 125, yet with both safeties lifted you had 130 in the boiler, that means the two safeties don't have enough volume for the steaming capacity of your boiler. Which can be why the second safety is able to lift with the first one open.
David Rohrer
The test behaved exactly as I expected it would.
http://www.chaski.org/homemachinist/vie ... =8&t=95846
(2nd post in the thread)
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
- Trainman4602
- Posts: 3482
- Joined: Sat Oct 16, 2004 9:26 pm
- Location: New Jersey
Re: THE TEST RESULTS ARE IN
I do agree with that. When I have the two safety valves in saparate outlets it easily handles the boiler output. The fact that they are trying to relieve the boiler thru one common outlet of the same size is why the boiler was able to bulid pressure even thou both safeties popped.
I wish I could have tested them using a 1/4 inch pipe.
I wish I could have tested them using a 1/4 inch pipe.
ALLWAYS OPERATING MY TRAIN IN A SAFE MANNER USING AUTOMATIC AIR BRAKES
Re: THE TEST RESULTS ARE IN
The critical point here is that by adding a T and a second safety, one may not achieve the protection desired. Said another way, if the supply is just 1/8" pipe, it most likely is not a good idea to Tee to provide a second safety. I expect that would not be the case with a 1/4" or larger supply (for 1½" scale boilers).
Harold
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
- Trainman4602
- Posts: 3482
- Joined: Sat Oct 16, 2004 9:26 pm
- Location: New Jersey
Re: THE TEST RESULTS ARE IN
That is correct.
The conclusion is that mounting two safeties in the same outlet in the boiler will work providing that the outlet and all the piping is larger than the size of the outlet hole in the safety valves.
This is exactly why during the test the secondary valve (125lbs) popped because the pop off pressure was reached. The boiler continued to build pressure because the piping could not handle the volume of steam being generated.
It worked as intended when I mounted the safety in the proper outlet.
The experiment proved my theory that mounting two safeties on a tee when the piping is all the same size will not reduce the pressure as intended for the secondary valve to do. The pressure will continue to build.
The tee arrangement only provides a secondary fail safe incase the first(lower pressure) valve fails.
The conclusion is that mounting two safeties in the same outlet in the boiler will work providing that the outlet and all the piping is larger than the size of the outlet hole in the safety valves.
This is exactly why during the test the secondary valve (125lbs) popped because the pop off pressure was reached. The boiler continued to build pressure because the piping could not handle the volume of steam being generated.
It worked as intended when I mounted the safety in the proper outlet.
The experiment proved my theory that mounting two safeties on a tee when the piping is all the same size will not reduce the pressure as intended for the secondary valve to do. The pressure will continue to build.
The tee arrangement only provides a secondary fail safe incase the first(lower pressure) valve fails.
ALLWAYS OPERATING MY TRAIN IN A SAFE MANNER USING AUTOMATIC AIR BRAKES