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

Post by barts » Sun Oct 29, 2017 5:54 pm

In order to safely put any liquid into the storage tank, it must be reduced in temperature & pressure such that it is at or below the temperature of saturated steam at the pressure rating of the safety on the receiving vessel.

You would then introduce the liquid at the bottom of the tank and vent off sufficient steam from the top to allow the liquid to flow, just as what happens when one has a propane tank refilled w/ liquid.

During the filling process, the pressure of the receiver is just a little bit below the pressure from the source.

The right way to make this work is to have the same pressure rating on both vessels; you can of course put a lower pressure safety on Nitra for experimental purposes
if that lets you test the idea w/ available tanks, etc.

Attempts to transfer water from Nytra's boiler to a lower pressure vessel is fraught w/ hazards - don't. For example, your safety is rating at 790 lbs/hr. This is ~100 gallons water/hr, or 1.7 gallons/min. You MUST insure that any water transfer is less than this w/ a fixed orifice as was suggested, otherwise you'll exceed the pressure rating of the receiving vessel since the safety won't be able to keep up.

Here's another method you may wish to consider. Rather than attempting to transfer liquid, how about placing some room temp. water into the receiver and then heat it by introducing steam directly into the liquid via a steam line from Nytra. This line could be sized to limit the amount of steam transferred to what the safety on the receiver can handle. This would also reduce the effect on Nytra's water chemistry, but it would definitely be slower - not necessarily a bad thing. This does make this a 'fired' vessel, but I think it would be innately safer due to both reduced energy input and obviously single phase transfer. The kayak becomes a giant Windermere kettle, in other words.

- Bart
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Bart Smaalders http://smaalders.net/barts Menlo Park, CA
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Re: What are the concerns/safety of an unfired >100C vessel

Post by DetroiTug » Sun Oct 29, 2017 7:00 pm

Quote: "introduce the liquid at the bottom of the tank and vent off sufficient steam from the top to allow the liquid to flow, just as what happens when one has a propane tank refilled w/ liquid."

It's nitpicking, but that is really only a recent thing with small cylinders as they are most all equipped with an 80% bleeder tubes now, they weren't before and were simply filled by weight. What happened with older cylinders and still does with large residential tanks, the delivery pump overcomes the pressure in regard to temperature and condenses the gas above the liquid back to liquid, the opposite end of what we're discussing here. The Windermere principle for transferring the heat is a better idea, than trying to transfer all the liquid over, just move the heat. Keep the big boiler fired and recharge it over and over. Then it would need a feed pump too.

For his projected steam needs with that small engine a small propane fire boiler that could fit in a coffee can could be made and forgo all this. That PV is going to be very heavy to be lugging around..


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

Post by Oilking » Sun Oct 29, 2017 7:11 pm

Bart
What you suggest is very similar to what happens with a wet accumulator on a steam catapult. Older cats used dry receivers that were nothing more than unfired steam drums. These had to be refilled after each launch, and did not maintain a constant pressure during the launch. One or two boilers were usually dedicated to cat duty. BT friends that stood watch on cat boilers hated it since they were constantly going from high load while filling the receivers to nothing all day long. Thus the advent of the wet accumulator that was smaller and able to deliver a constant pressure to the cats during a launch. They are vessels half full of water that have a perforated manifold submerged in the water where steam is introduced to maintain the temp/pressure and water level, while not putting the surging demand on the steam system that the dry receivers did. A blow down and feed system is provided to maintain water levels within hi/lo set points.

Maybe to much info but what the heck.

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

Post by cyberbadger » Sun Oct 29, 2017 11:45 pm

Fred,

Please comment on this picture.

The cross is Class 3000 Forged.

Pipe after Red PV is schedule seamless 80 pipe to the first Valve and Class 300/3000 to the first Valve.

I tried to use MAWP 200 except for: Lockable 3/8" 150SWP Valve after 200SWP Apollo ball valve. (I can take it out, but I wanted the
-CB
[Attachment Redacted,: Physical Layout Changed See Newer Post.]I tried to use MAWP 200 except for: Lockable 3/8" 150SWP Valve after PV valve.
Last edited by cyberbadger on Mon Oct 30, 2017 5:06 am, edited 1 time in total.
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Re: What are the concerns/safety of an unfired >100C vessel

Post by fredrosse » Mon Oct 30, 2017 3:29 am

CBs Kayak Pressure Vessel (KPV), a few clarifications are needed here. It may seem that I am being too specific in my descriptions here, but I have experienced on many occasions that what is obvious to me, or seemingly obvious to experienced steam men, gets installed backward with misunderstood instructions. So, my apologies for being too long-winded here, but I must try to make sure my statements are not taken incorrectly. Being a registered professional engineer, I will only provide comments on fluid system designs which meet the rules according to ASME and ASTM codes. Yes, in many instances these rules are very conservative, and many people can get satisfactory performance while violating the intent of these rules, but better safe than sorry.

CB: "Later you said 1/4" for the aquatrol.

Is just not appropriate for this PV? Or just restrict it to 1/4"?"


ANS: The line carrying the saturated steam or saturated water used to fill the KPV needs to be small enough such that the KPV relief valve can always pass more flow than the line is capable of passing, considering maximum pressure/temperature of the connected energy source, the big boiler. That is the philosophy that should be met.

The relief valve has a 1/2 inch NPT connection, and there can be no smaller piping between the KPV and this relief valve. The piping between the KPV and the relief valve should be straight, and as short as possible. Relief valve discharge piping should also be short, with minimum fittings, directed to a safe location. That is code rules to assure relieving capacity equal to the flow stamped on the safety valve, 790 PPH.

Approximate calculations for a 1/2 inch diameter line from the big boiler to the KPV show the potential for passing more than 790 PPH steam flow, although a thorough calculation considering all the fittings, valves, hose length, etc. could probably show less than 790 PPH, but why take chances on this when a smaller line can easily do the job?

I think a 1/4 inch ID line would charge the KPV very adequately, taking a short time to charge the KPV, so that would be my choice here.

CB "So I am taking a non reply to this to mean that I should reduce this Aquatrol to 1/4" inlet per your quote from Fred."

ANS: This statement is confusing to me, "….reduce this Aquatrol to 1/4" inlet…" But just to be perfectly clear here, the rules do not allow the inlet to the relief valve to be any smaller than 1/2 " pipe size. A short connection directly from the KPV to the relief valve, 1/2 ' pipe, or larger, is required. The charging line, big boiler to KPV is limited in size, use 1/4" ID to assure never overloading the relief valve.
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Re: What are the concerns/safety of an unfired >100C vessel

Post by fredrosse » Mon Oct 30, 2017 3:52 am

The configuration CB has for the KPV has a difficulty, since the KPV relief valve is rated at 790 PPH. This flow rate is roughly ten times the nominal steaming capacity of a typical steamboat, a big steam flow for a small boat.

When the KPV is charged with 125 PSIG/353F conditions, say 80% full of saturated water, steam 20%, and continued flow from the big boiler then causes the safety valve to lift, all hell will break lose. The immediate flow path thru the rather large relief valve will pass so much flow (790PPH) that the entire KPV will flash into a homogenous mixture of steam and water, all at 353F. This occurs because the steam release surface (steam bubbles traveling to the water level surface for release) is far too small in the KPV for such a large steam flow. A very reasonable analogy here is the bottle of carbonated cola. Open it normally, and the bubbles rise to the liquid surface and are released without disturbing the coke level too much. Drop the coke bottle on the floor, then open the bottle, and so much gas is released that the liquid level immediately rises to the full bottle volume, a big two-phase mess, and 3/4 of the liquid coke is driven out of the bottle. This is what will happen with the setup on the KPV, and this is not good.

That is why I recommended that the KPV have a design pressure above the MAWP of the big boiler.
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Re: What are the concerns/safety of an unfired >100C vessel

Post by fredrosse » Mon Oct 30, 2017 4:05 am

From Bart: "Here's another method you may wish to consider. Rather than attempting to transfer liquid, how about placing some room temp. water into the receiver and then heat it by introducing steam directly into the liquid via a steam line from Nytra. "

ANS: That is the way I would do it, room temp water initially, or hot water later. Steam admitted at the lowest level in the KPV, small venting flow at the liquid level cock during charging.

"This line could be sized to limit the amount of steam transferred to what the safety on the receiver can handle. "

ANS: Yes that is a requirement for the charging line, either liquid or steam.

"This would also reduce the effect on Nytra's water chemistry,"

ANS: Good point, much less mass transfer, steam carries far more energy per pound than the saturated water.

" but it would definitely be slower - not necessarily a bad thing. "

ANS: Not necessarily slower than introducing "botton blow" water from the big boiler, certainly comparable energy transfer rates with either method.

"This does make this a 'fired' vessel, "

ANS: The KPV is not a "fired vessel" according to code rules, it is simply an unfired pressure vessel, if built to code, ASME VIII, Unfired Pressure Vessels.

" but I think it would be innately safer.......obviously single phase transfer. "

ANS: I agree, two phase flashing mixtures are often troublesome.
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Re: What are the concerns/safety of an unfired >100C vessel

Post by fredrosse » Mon Oct 30, 2017 4:29 am

From CB "Fred, Please comment on this picture....."

I see code violations here, and questionable functionality. More tomorrow, need sleep, I have to drive to NYC at 430 AM
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Re: What are the concerns/safety of an unfired >100C vessel

Post by cyberbadger » Mon Oct 30, 2017 7:10 am

Redacted first picture, mis understood about the piping orrifice restriction.
pvtop.jpg
PV Top Rev2
pvtop.jpg (121.48 KiB) Viewed 1573 times
* No Restriction from ASME Safety to 4" pipe
* 1/4" NPT SCH80 Restriction on incoming lines

Then the other end will just have a double valve for condensate and drain.

Thinking about just one of the 4" diam 36" piece for first test.

Not sure I understand 100% on which (if any) of the valves can be at the lower MAWP.

The yellow handled shutoff on the pressure gauge and the blue handled ball valve are only rated 150SWP.

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

Post by cyberbadger » Fri Nov 03, 2017 7:31 am

So I need to get a bigger pipe wrench or cobble together a strap wrench because part of the 4" pipe is being difficult and just my hands isn't enough.

I was then going to hydro it, but I wanted Fred to let me know if he saw any code violations on the last image. :-P

-CB
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