Flash boiler safety?

A flash boiler seems like a game changer. I'm very intrigued and would like to build one myself.

I'm referring to the numerous posts by kladue, Brewpastor, FSR402, ScubaSteve, WortMonger, (others?).

My concern is safety. I've been reading about flash boilers the last several days, and I've seen it referred to as one of the safest boilers. But how safe is it for a DIY'er without some sort of steam safety certification?

I don't worry about explosions from the counterflow wort chiller I hacked together. I am concerned about superheated steam.

After reading this post, Steam Injection, I could declare a flash boiler to be an uncontained system and therefore absolutely safe. But in reality, I don't truly know what I'm talking about when it comes to steam safety. I therefore turn to those with more experience and wisdom than I.

Are there any safety precautions I should be taking, such as adding a pressure relief valve, just in case? It seems obvious that I should avoid accidentally making a contained system. Are there any gotchas I should be on the lookout for? What about the dangers of a steam burn? What practical lessons have you learned from your experience with these systems?

Thanks!

Although uncontained, my understanding is there is a spike of pressure any time the steam condenses inside the tubing and momentarily blocks the output. This can be heard and sounds like popping or hammering. It appears that some users have reduced these episodes by installing a screen on the end of the steam tube which breaks up the steam into smaller more manageable bubbles. Unless the end of the tube becomes blocked you should not be able to build up enough pressure for the system to become dangerous weather you use copper or SS. Most systems use SS for saftey but copper provides better heat transfer and more effeiency.
Steam burns are by far worse than water burns. Steam is hotter than boiling water thus can cause more damage more quickly. You should exercise caution weather dealing with boiling water or steam.

The flash boiler systems I have built flow through the wort mixer tee to the sparge ring in the mash tun without any valving. The boiler output temperature is controlled by the amount of gas sent to the burner with a constant water flow rate. Before sharing the idea of the flash boiler I have tried to purposly blow it up by dry firing the tubing coils to orange hot and applying cold water at the strike water rate, it created an impressive blast of steam from the sparge ring but that was over in about 10 seconds as the tubing thermal mass is low, and the unit did not develop any leaks from the experiment. Since the boiler output is always sent to mash tun for strike, wort heating, and sparge there is no need for connection changes or flow redirection during the brewing cycle. Water flow is regulated before it enters the boiler to prevent pressure buildup which would happen if you tried to regulate outlet flow. The nice feature of the flash boiler is that the new boiler in the phase 2 system can hit boiler outlet temperature setpoint in under 60 seconds from a cold start at .5GPM flow, and hold that temeprature as long as water and gas flows are maintained, no pressure/temperature drop during operation like the pressure cooker steam designs. I am going to build a copper coil flash boiler from hardware store parts and then torture it to make sure it is safe before sharing the design and parts list.

kladue said:

Water flow is regulated before it enters the boiler to prevent pressure buildup which would happen if you tried to regulate outlet flow. .

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this is the most important point here. always regulate water flow from upstream of the boiler to prevent pressure buildups. also is safer to start water flow before firing burner to prevent a flash to steam event and possible scalding for someone not aware of and in the proverbial wrong spot wrong time.

Thank you all for your responses. The more I think about your responses (and the concept in general), the more comfortable I feel with its safety.

kladue said:

Since the boiler output is always sent to mash tun for strike, wort heating, and sparge there is no need for connection changes or flow redirection during the brewing cycle.

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Ah, this was key for me. I had seen WortMonger's Darth Vapor and that's why I asked about a pressure relief valve. I didn't understand how you had avoided the need for a pressure relief valve, but now your response makes that clear.

Well, this will be fun to build over the summer. I wasn't happy with the performance of the pressure-cooker-based steam injection system I'd built based off plans in this forum (though I might not have built it correctly). A sufficiently large flash boiler seems like it will be much more powerful.

If you would like to see and operate a flash boiler SIRIM system before you build one we could fire up the old brew system during my next R&R run at the end of june. Here is a couple photo's of the old systemPicasa Web Albums - Kevin - Old Brewing S..., it can be broken down and hung on the garage wall in about 10 minutes using a 6" crescent or 11/16" end wrench.

kladue said:

Here is a couple photo's of the old systemPicasa Web Albums - Kevin - Old Brewing S..., it can be broken down and hung on the garage wall in about 10 minutes using a 6" crescent or 11/16" end wrench.

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Oh, I've been well acquainted with the photos of your rig for some time now. It is a thing of beauty.

kladue said:

If you would like to see and operate a flash boiler SIRIM system before you build one we could fire up the old brew system during my next R&R run at the end of june.

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I would *love* that. Looks like we're about an hour apart from one another. Unfortunately, the second half of June I'll be everywhere but Oregon, except Weds 6/17 and Weds 6/24. Also, getting married end of July. Busy summer! =)

Are you headed through Eugene for your R&R? Alternatively, I could head up there. I really would love to see your FB in person.

Looks like next R&R trip will be from July 2nd - 6th and from July 30-Aug.2, until then I get to enjoy another arizona summer in chandler.

kladue said:

Looks like next R&R trip will be from July 2nd - 6th and from July 30-Aug.2, until then I get to enjoy another arizona summer in chandler.

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Excellent, I'll be in town then! If you're coming through Eugene, we'd be delighted to have you over. I'll PM you my contact info.

Coincidentally, my friend has a 18-22 gal setup, and he was just contemplating use of steam to speed boiling and heating in general when I showed him your setup. You now have an audience of at least two.

When I have finished building and testing a copper coil flash boiler you should be able to copy the design and be able to heat water and do steam injection RIMS heating for step mashing.