What are the concerns/safety of an unfired >100C vessel

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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DetroiTug
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Re: What are the concerns/safety of an unfired >100C vessel

Post by DetroiTug » Sun Oct 29, 2017 3:38 pm

I never said he was wrong, what I think he is saying without writing it, your experiment is going to result in a receiver tank that is going to have a much lower pressure after the transfer. Just in case doesn't, have a relief valve to pop off during transfer. The whole thing is a bad idea in my opinion.

Also ratings on pipe are typically far below their actual capability. The reason I say the steam car world and the steamboat world are far different in practice in regard to material type and specification, I've seen things that would make a steamboaters hair curl. Schedule 40 pipe on 600 psi steam, Copper tubing in the fire running at 700 psi, just to name a few...

Build it, hydro it to double your intended MAWP and go from there - proper protocol, hide behind a tree the first few times it's used etc. All this hand-wringing over a relief valve is silly.

-Ron
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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Sun Oct 29, 2017 3:44 pm

I'm not comfortable making those jumps. A hydro does not address the temperature rating.

-CB
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Re: What are the concerns/safety of an unfired >100C vessel

Post by DetroiTug » Sun Oct 29, 2017 3:57 pm

Google "Steam tables". Steam pressure has everything to do with steam temperature. If the pressure is known, so is the temperature - without a temperature gauge, the pressure dictates the temperature and vice versa. That is why you rarely to never see a temperature gauge on a boiler.

Temperature rating for mild steel? Well according to some recent research, it's strongest at around 400 degrees F.
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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Sun Oct 29, 2017 4:06 pm

I understand steam tables. And I know that things are rated far less then the burst pressure.

But we are talking a PV here, and I'm not comfortable making jumps myself, So I'm stuck with a safety.

If the boiler gauge says 150PSI, but the water I draw from the water legs is a higher temperature then the safety valve is what is addressing the temperature.

-CB

P.S. The elbow is NOT mild steel, it is cast and the size is huge. I'm only comfortable using it as rated.
Last edited by cyberbadger on Sun Oct 29, 2017 4:24 pm, edited 1 time in total.
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Re: What are the concerns/safety of an unfired >100C vessel

Post by DetroiTug » Sun Oct 29, 2017 4:22 pm

Quote: "If the boiler gauge says 150PSI, but the water I draw from the water legs is a higher temperature"

Quote: "I understand steam tables."

Sorry, but you don't. If the water in the water leg is higher temperature than the corresponding pressure, it will quickly expand to steam and equalize to the correct corresponding pressure per the "Steam tables". It can't be one or the other, think of pressure and temperature as two meshed gears with equal numbers of teeth, whatever one does, the other does the same. Steam can be superheated, and be a higher temperature than the water, but that really has nothing to do with expanding water to steam at temperature in the boiler.

This is what happens in "carry over" events. When the pressure is drawn quickly below the corresponding temperature, the water immediately boils violently to equalize. This violent boiling - bubbles in the water raise the overall water level to the steam outlet and water goes to the appliance.

Quote: "I'm not comfortable making jumps myself"

No offense, then you shouldn't be trying it.

-Ron
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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Sun Oct 29, 2017 4:30 pm

The heat soak process will equalize the temperature. Then I will discard the contents of the PV and fill it again.

The second time the safety is what handles the temperature.

-CB
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Re: What are the concerns/safety of an unfired >100C vessel

Post by Oilking » Sun Oct 29, 2017 4:49 pm

Ron beat me to it.
The water and steam in the boiler will be the same temperature (366deg F @ 150 PSI). If there is a part of the heated surface that receives more energy than others it won't make the water hotter, it makes it produce more steam.

FYI: Google Steam catapult accumulators, they preform a function not unlike what your trying to do, but there is a huge scaling factor to consider.

Good luck

Dave
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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Sun Oct 29, 2017 4:55 pm

Oilking wrote:Ron beat me to it.
The water and steam in the boiler will be the same temperature (366deg F @ 150 PSI)
There is no forced circulation in my boiler, so you can't make that assumption.

-CB
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Re: What are the concerns/safety of an unfired >100C vessel

Post by Oilking » Sun Oct 29, 2017 5:20 pm

In short yes I can. If the pressure in the water leg is the same as that of the steam the temperature will not be greater than that of the steam.

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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Sun Oct 29, 2017 5:38 pm

Ok guys, I'm tapping out for a while.

I'm sticking with a safety valve because I'm trying to follow his guidance...

Unless I hear from Fred I'm building to what he said 1/4" restriction, Swagelock connection, safety valve less then or equal to 150PSI, tricock, big boiler MAWP rating on incoming valve.

-CB
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