Economizer tube material

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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cyberbadger
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Economizer tube material

Post by cyberbadger » Wed Dec 06, 2017 1:02 am

Can this be copper to be suitable for use with ASME code?
Does it need to be seamless if stainless?
Is there a way to size how many feet would be good, or the more the merrier?

What material/size/spec have you used?

I'm looking at trying a coil in the bonnet of my VFT after an injector and before one of the boiler water inlets?

-CB
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Re: Economizer tube material

Post by barts » Wed Dec 06, 2017 4:16 am

I've used copper to good effect, but I pump water all the time. During steamup steam will form here if you fire hard, which is not a good thing; copper loses much of it's strength at higher temps. Always have a means (valve or plumbing made up) to bypass a copper economizer because of this. Otherwise, some steel tubing or pipe will work just fine.

Note that if your feedpump tends to hammer, the economizer will tend to rattle; it should be well secured to avoid vibration damage from rubbing on the top tube plate or other supporting pieces. Otter's copper tubing was abraded significantly and the copper tubing showed signs of overheating after 15 years.

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Lopez Mike
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Re: Economizer tube material

Post by Lopez Mike » Wed Dec 06, 2017 1:44 pm

It would be nice to use copper/nickel condenser tubing for its high temperature characteristics but I suspect you would end up spending big money for it.

Thinking about it, the same issues apply here in some respects as for flue tubing. The conductivity of water is so low compared to any metal that any increase in heat flow going from steel to copper would seem to be not really worth the trouble, expense and poor heat strength of common copper tubing. One serious overheat and poof! It will just bulge out and split and you will bypass it and go home with a thoughtful look on your face.

On another subject, I have a low opinion of injectors in marine service. I've used them in locomotives where the load is wildly variable and being able to cool the boiler down is important when stopping the train. But in relatively steady state launch service I don't see the advantage of dumping cold water in there.

As far as having an economizer after an injector, my experience has been that the performance of an injector is sensitive to flow restrictions. I have accidentally left the isolation valve between the injector and the boiler about three quarters of the way open and the beast would barely start and performed poorly. I wouldn't give one space in my boat.

A reliable mechanical pump with a backup hand pump and you can stop fussing with the power plant and enjoy boating. Unless, of course, your reason for boating is to fuss with your power plant. In which case, enjoy yourself! (Not being sarcastic. I mean it.)
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Re: Economizer tube material

Post by Mike Cole » Wed Dec 06, 2017 5:09 pm

Sorry I can not help with your question but it was good to see that you got a full page in the current issue of 'Funnel' all to yourself 8-)
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Re: Economizer tube material

Post by cyberbadger » Wed Dec 06, 2017 5:15 pm

Mike Cole wrote:Sorry I can not help with your question but it was good to see that you got a full page in the current issue of 'Funnel' all to yourself 8-)
I was very excited.

I think it worked out well, my little report was a nice segway into several interesting articles about paddlewheelers.

-CB
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Re: Economizer tube material

Post by cyberbadger » Wed Dec 06, 2017 5:49 pm

Lopez Mike wrote: On another subject, I have a low opinion of injectors in marine service. I've used them in locomotives where the load is wildly variable and being able to cool the boiler down is important when stopping the train. But in relatively steady state launch service I don't see the advantage of dumping cold water in there.

As far as having an economizer after an injector, my experience has been that the performance of an injector is sensitive to flow restrictions. I have accidentally left the isolation valve between the injector and the boiler about three quarters of the way open and the beast would barely start and performed poorly. I wouldn't give one space in my boat.

A reliable mechanical pump with a backup hand pump and you can stop fussing with the power plant and enjoy boating. Unless, of course, your reason for boating is to fuss with your power plant. In which case, enjoy yourself! (Not being sarcastic. I mean it.)
I respect your opinion. I think it's more of an American? West coast? viewpoint. Really my two injectors have provided very trouble free service. I have an inline mesh filter for the steam int, and cold water suction for each injector. Keep one of the injector checklists onboard for bad days. Have two injectors, and pick two that are from different manufacturers.

The way Nyitra is setup as I intended, it's a good to operate with two (a fireman and an engineer/skipper). However with just me it is doable but a handful and I can't really keep up flat out.

But yes, some level of futzing is good. Not just for me, I have actually had a comment from an observer on shore that indicated they could see the work involved to operate her and were impressed. :) What they saw was me getting up to walk over to the boiler to add fuel and water every couple of minutes.

Regardless even if I were to switch completely to an engine driven pump or steam pump, I still want to try an economizer.

-CB
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Re: Economizer tube material

Post by barts » Wed Dec 06, 2017 6:19 pm

Cupro-nickle tubing (90/10) still has 50% of its room temp strength (48 ksi) at 932 F, so that makes really nice economizer tubing. This stuff is popular (and readily available) as brake and fuel/transmission line tubing. For 3/8" tubing a 25' roll ranges in price from $130 (Cunifer imported good British stuff, .028 wall) to about $60 (likely Chinese import via Amazon or Summit Racing).

Note that to get maximum benefit you'll want to use a float in your hotwell so the flow is continuous (or just crack the bypass valve so flow is continuous), and you should size the tubing so that turbulent flow conditions (Reynolds number over 4000) exist; this well may require smaller tubing. Boats exhausting up the stack should see more benefit for a given size of economizer since exhaust gases will be higher.

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Re: Economizer tube material

Post by Lopez Mike » Wed Dec 06, 2017 6:25 pm

You techies are all the same. Wish I even had a real hardware store around. Pretty much all the stuff on my boat is fixable with access to a rock, a cold chisel and a True Value hardware store wannabe.

Cool that you found decent sized CU/NI tubing. All I have seen is .25 brake lines. Too small for me.
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Re: Economizer tube material

Post by barts » Wed Dec 06, 2017 6:40 pm

Lopez Mike wrote:You techies are all the same. Wish I even had a real hardware store around. Pretty much all the stuff on my boat is fixable with access to a rock, a cold chisel and a True Value hardware store wannabe.

Cool that you found decent sized CU/NI tubing. All I have seen is .25 brake lines. Too small for me.
Last time I checked, even the hinterlands, such as the south end of Lopez Island, gets UPS deliveries :).

When I first got Otter in the water I used to shop locally for everything... this was the late 80s, and only the cool kids had Mcmaster-Carr catalogs. Now I can order stuff on line from a whole bunch of sources, and I no longer need to spend my time fighting the insane SF Bay area traffic. My local hardware store doesn't carry schedule 80 steel nipples for a boiler - but they're here in one or two days from Los Angles.* It's really a lot easier than it used to be.

In any case, I'll agree that the real value of the Cu/Ni tubing is that it's much easier to install than 1/4" steel pipe; the heat transfer differences are minor in practice, given the low air flow velocities around the economizer.

- Bart

* Yes, there are industrial plumbing places here, but they're unaccustomed to doing retail; most expect purchase orders and open accounts.
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Re: Economizer tube material

Post by Lopez Mike » Wed Dec 06, 2017 7:13 pm

Yeah. Web buying and delivery to my door is becoming inescapable. Worse than that is getting electronics stuff. I used to get odds and ends from Radio Shack but they have closed all of the stores in my area. And the one industrial outlet went out of business. They cried a bit about competition from the web but the real reason was that no one fixes things any more. When I'm looking at a power supply that cost me $25 delivered to my door and I will spend an hour and $10 bucks to fix it, why bother?

At least it's worth my while to put valve in my feed water pump. Steam launches are far away for being a mass market toy. Isn't that a nightmare to go to sleep on???
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