Desuperheater question

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: Desuperheater question

Post by barts » Sun Apr 14, 2019 7:33 pm

Thanks Fred, I completely forgot to mention the isolation valve.... I have one on all boiler connections (save the safety, of course!) on both boats. If my economizer fails (e.g. leaks) , I'll bypass it and leave it open - it's not going to get any more damaged :). I used a copper economizer for years on Otter, but keeping that tubing from getting damaged due to vibration (prob. during trailering) is tricky. I've not fitted an economizer to Rainbow's boiler yet - that will likely happen when Rainbow and us are living in the same state - but that one will be steel to be more self-supporting.

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Re: Desuperheater question

Post by TriangleTom » Mon Apr 15, 2019 12:46 am

fredrosse wrote:
Sun Apr 14, 2019 3:21 am
Adding a couple of points to Bart's list, needed to comply with the ASME Boiler and Pressure Vessel Code:

No. 6 Boiler check valve, followed by an Isolation Valve

If the economizer can be isolated and bypassed, then the economizer itself requires pressure relief protection because it then becomes a "fired pressure vessel" independent of the boiler proper.
Out of curiosity, where can you access a copy of the ASME BPVC? I've been looking on and off for a while and my search so far has been unsuccessful.
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Re: Desuperheater question

Post by fredrosse » Wed Apr 17, 2019 3:23 am

Bart, I had exactly the same problem of vibration causing a leak in a copper economizer, the cause of one of the forced outages encountered during a four year run of the Domestic Heat-Power Module. Burning Anthracite coal, there is virtually no smoke, and no white plume during winter as there is no hydrogen in this fuel.
Burning fuels with significant hydrogen content results in H2O in the flue gas, and this steam condenses on leaving the stack, giving a white exhaust plume.

While operating this machine, I decided to pour engine drain oil over the feed coal, to burn it up and recover some extra heat, and drain oil has a significant component of hydrogen, hence the opportunity to see some white cloud in the exhaust. Cruising along, I was noticing white exhaust, and foolishly thought this was the oil being burned. Actually it was a small hole being developed where the copper economizer coil was rubbing against a steel tube support in the stack. Next day, the white plume looks as if I am running on natural gas fuel (CH4), which gives off a large white plume. Next day the exhaust stack looks like the one you see on a steam locomotive, and I begin to question the excessive amount of white plume. Soon afterwards, the boiler shuts down on low water level, as the economizer leak has become so large that there was not enough feedwater to keep up the boiler water level.


Tom, "Out of curiosity, where can you access a copy of the ASME BPVC" You can buy it from the ASME, I think for a couple of thousand dollars for the whole set. The engineering firm I worked for (45 years so far) is certified to make unfired pressure vessels and boilers, and thus has full sets of ASME Code books. However reading these documents, even to get a very limited proficiency at boiler construction rules, will require several hundred hours work, with an engineering degree as a prerequisite. Interesting reading usually only for nerds like me.
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Re: Desuperheater question

Post by TriangleTom » Wed Apr 17, 2019 4:52 am

fredrosse wrote:
Wed Apr 17, 2019 3:23 am
Tom, "Out of curiosity, where can you access a copy of the ASME BPVC" You can buy it from the ASME, I think for a couple of thousand dollars for the whole set. The engineering firm I worked for (45 years so far) is certified to make unfired pressure vessels and boilers, and thus has full sets of ASME Code books. However reading these documents, even to get a very limited proficiency at boiler construction rules, will require several hundred hours work, with an engineering degree as a prerequisite. Interesting reading usually only for nerds like me.
Fred,

Thanks for the information! Fortunately, I recently got the engineering degree, however I unfortunately feel that purchasing the full set would not be the best use of $17,000. I do live in a university town, so I'll see if I can access it through their library. Either way, this is more for my personal enjoyment as I'm planning to use a John King design.

Tom
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Re: Desuperheater question

Post by barts » Wed Apr 17, 2019 5:29 am

I used an old copy of John Perry's Chemical Engineering Handbook (4th edition) I got for free while I was doing a lot of design stuff; they had pressure vessel details, piping design, joint design details, etc from ASME standards, and the price was right - free. They're available on Ebay for $30 or so. Yes, it's not the same thing, but I really didn't have time or need to go through the entire code when designing Otter's simple boiler. That said, it's pretty impenetrable w/o an engineering background.

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Re: Desuperheater question

Post by TriangleTom » Wed Apr 17, 2019 7:25 am

Thanks Bart! Just placed an order!

Tom
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