Author Topic: Developing a Small Steam Plant  (Read 14077 times)

Offline MJM460

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Re: Developing a Small Steam Plant
« Reply #45 on: November 04, 2019, 04:39:29 AM »
Looking good Gary.  Great to see progress already after returning from your travels.

One thing to note, that combination of metals will over time give you corrosion problems if it ever gets wet, which it almost certainly will.  The Aluminium tube will do a great job of protecting the stainless screws and the brass by sacrificing itself.

Fortunately there is a simple solution.  You might know that most yacht fittings are stainless steel, while masts and booms are mostly aluminium.  Any yacht chandler will have a small tube of paste to use as an insulating barrier.  It works well even in salt water environments.

So when you get to your near final assembly, put a smear around the top of the aluminium stand and a dob on each screw before you insert it.  It works very well, and will avoid unsightly corrosion, and ensure that you can always pull it apart if necessary.  The one I use is green, just wipe off the excess with a paper tissue or rag, but other brands may be a different colour.

Looking forward to the next steps.

MJM460

The more I learn, the more I find that I still have to learn!

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #46 on: November 04, 2019, 09:02:21 AM »
Hi MJM, and thanks for your input once again.

My knowledge of the dark metallurgical arts only extends so far as knowing that 'some metals in contact with each other can cause corrosion', but without any real clue about what metals will do that. Your advice, therefore, is very helpful. There are a couple of yachting chandlers near where I live so it should be easy enough for me to get some of the goo you recommend.

Cheers...

 :ThumbsUp:

Offline Bluechip

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Re: Developing a Small Steam Plant
« Reply #47 on: November 04, 2019, 09:56:26 AM »

 'some metals in contact with each other can cause corrosion', but without any real clue about what metals will do that.


Electrode potentials.

The greater the potential, the greater the risk of corrosion. There does need to be an electrolyte ( usually water ) present.

http://www.efunda.com/materials/corrosion/electrochem_list.cfm?sort=com

From the table copper is about +0.5v and zinc - 0.75v so if you poke a bit of each in a orange / potato / whatever you'll land up with a 1.25V - ish battery.  :)
No great current draw possible but it will drive a red LED, or sometimes a very small  motor

From memory the copper will eventually disappear hence the expression 'sacrificial anode'.

There is a fair bit more to it but I've long since forgotten ....  :old:

Oops .. starts here:

http://www.efunda.com/materials/corrosion/corrosion_basics.cfm

Dave
« Last Edit: November 04, 2019, 10:00:08 AM by Bluechip »

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #48 on: November 04, 2019, 09:28:57 PM »
Thanks Dave.

I have no doubt that this information will be useful in many other projects too.

gary

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #49 on: November 10, 2019, 10:53:07 PM »
I had to redo the soft soldering of the steam outlet pipe because I got all the angles wrong first time round. This was a messy and time consuming business but I got there. I then water tested the connections on the coil at the top of the separator and they appeared to be watertight. So, the way forward was clear...

The top and bottom halves of the main vessel were pushed together and the join covered with self-amalgamating tape. But for MJM 460 I wouldn't know this stuff existed, but it seems ideal for the job in hand, bearing in mind that this is not a pressure vessel:



Next, the separator was lagged in ceramic fibre insulation material secured with fine copper wire:



And, bar a few lotions and potions, that's pretty much it. I'll call it done for now:



Given that all of the main components are now done, the next step is to think about the layout of the plant as a whole and consider what material I'm going to use as a base board.

Will be interested to know what other people would use!

gary

Offline MJM460

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Re: Developing a Small Steam Plant
« Reply #50 on: November 11, 2019, 08:54:56 AM »
Hi Gary, that’s a fine looking separator.  Now to see how it performs. 

I am not sure that I would have used the self amalgamating tape for that purpose, but it is very useful for a layer of insulation on the steam pipes.  However, as you say, it is not a pressure vessel.  Now that you have started soft soldering, you will have difficulty doing any further silver soldering, but again, it is not a pressure vessel.  I think I would have put a few rivets in, even if only loose, just to hold things in place and then soft soldered the seam.  Perhaps next time.  But there are many lessons in the journey to a handsome feature of your steam plant.

I just use a piece of chipboard for a base board, either melamine covered as in typical kitchen shelving to keep it waterproof, or just a few coats of polyurethane, again to make it waterproof.  Otherwise it tends to swell and disintegrate due to the inevitable water spills.  Ideally, eventually, I would like to tidy them up by adding brick like trim or more paint to make it look like brick or concrete, but perhaps that will wait until my model making skills are more advanced.

It is interesting that you chose to insulate the separator vessel inside the aluminium stand.  You are using the exhaust heat for boiler feed water in the coil, so don’t want to loose it unnecessarily, but then you are discharging the exhaust, so the more that condenses, the less moisture into the shed, assuming you are in a shed.  Perhaps another area for some experiments, by trying a few runs with that insulation removed once you see what it does with the insulation.

MJM460

The more I learn, the more I find that I still have to learn!

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #51 on: November 11, 2019, 09:12:56 AM »
Thank you MJM. Glad you like the look.

Apologies - I should have made it clear that your recommendation of the self-amalgamating tape was related to something else, not this. However, I have a feeling it will be ok in this application as the two sections of pipe that comprise the vessel make a really tight push fit. It can be quite hard to pull them apart by hand so unless that changes under heat, the tape is really just to close off any odd gaps round the perimeter.

I also thought about the dilemma of the insulation, and opted for your first point, i.e. to maximise the heat going into the feed water by preventing it from escaping through the walls of the vessel. But yes, as you say the condensing effect on the exhaust will be compromised. I guess it's a case of 'suck it and see' and trying it with and without the lagging.

Regarding the base board, my ideal would be a piece of the kind of smooth black slate that is often used to make fireplace hearths. That would look great, but it would be (a) expensive, (b) heavy and (c) unforgiving of any drilling errors.

I might prefer plywood to chipboard, possibly with a dark stain to camouflage any scorch marks. Or a slab of aluminium perhaps...

All ideas welcome!

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #52 on: November 20, 2019, 10:35:47 PM »
I decided on a piece of plywood 20 mm or so thick for the baseboard. It will be varnished in a dark mahogany colour when it's done. The basic layout is below. I intend to put a displacement lubricator between the separator/preheater boiler and the engine - I'll probably just buy it rather than make one. I also have a tiny electric motor which will hopefully work as an engine-driven generator powering a small led lamp - these will be placed at the front of the board (the bottom in the picture). Some components will be screwed to the board from above with wood screws; others will be fixed from below with machine screws, in which case the holes will be countersunk and/or counterbored on the underside of the board. Counterbored holes will be reinforced with washers epoxied in. I think that this will suffice rather than making threaded inserts. As a final touch, some kind of angle bead will be fixed round the outer edges of the board.



Starting to take shape but there's still plenty of plumbing and other stuff to do yet...

gary

Offline MJM460

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Re: Developing a Small Steam Plant
« Reply #53 on: November 20, 2019, 11:49:34 PM »
Hi Gary, looking good. 

You can see that the complexity builds quite quickly when you set out to make a complete steam plant.  It would be worth making a sketch schematic ( I.e not to scale) to show where all your piping must go to get all the components in the right order.   Piping runs will determine (along with access) the orientation of components.   Piping runs can be much simpler and tidier if the location of components is carefully chosen.

Remember the lubricator must go in the steam line between the boiler and engine, preferably close to the engine and with its outlet equal or higher than the engine steam inlet.  You don’t want oil in the boiler.

Thirty eight already here and it’s only 10:30 am and only November.  Not even summer yet.  Hardly need a preheater for the boiler.  But we are expecting a cool change later in the afternoon which should drop the temperature to a more comfortable level quite quickly.

MJM460
The more I learn, the more I find that I still have to learn!

Offline crueby

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Re: Developing a Small Steam Plant
« Reply #54 on: November 20, 2019, 11:53:30 PM »
Good tips on the piping from MJM, be bad to get most of the way through and have two pipes or fittings inrterfere. There is the high-tech route with drawings in 3D, down to the old school (and sometimes fun-ner) way of mocking it up with something like pipe cleaners. I remember mocking up sailboat cockpits with boards, crates, and extension cords.

Offline MJM460

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Re: Developing a Small Steam Plant
« Reply #55 on: November 21, 2019, 12:01:58 AM »
Don’t mock the pipe cleaners, Chris.  We used to build whole refineries with plastic tube and moulded fittings, and made up pressure vessels all to perfect scale.  Then attached labels with the dimensions and went direct from that to isometric drawings of individual pipes with material lists for the welders.  No layout drawings.

Main problem was the plastic tended to melt if we tried to fire it up to see if it would run.  Also turbines were lacking in internal detail!

That was real 3-D modelling, way before all this virtual stuff.

MJM460
The more I learn, the more I find that I still have to learn!

Offline crueby

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Re: Developing a Small Steam Plant
« Reply #56 on: November 21, 2019, 12:17:17 AM »
Don’t mock the pipe cleaners, Chris.  We used to build whole refineries with plastic tube and moulded fittings, and made up pressure vessels all to perfect scale.  Then attached labels with the dimensions and went direct from that to isometric drawings of individual pipes with material lists for the welders.  No layout drawings.

Main problem was the plastic tended to melt if we tried to fire it up to see if it would run.  Also turbines were lacking in internal detail!

That was real 3-D modelling, way before all this virtual stuff.

MJM460
I am not mocking them, I am serious about using them! In a mock-up. I would mock trying to put steam through them!

Offline MJM460

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Re: Developing a Small Steam Plant
« Reply #57 on: November 21, 2019, 12:30:33 AM »
Yeah, pipe cleaners would not even handle low pressure air.  Come to think of it while our plastic tubes would have been ok for low pressure air, the elbow and tee fittings, valves etc were all solid.  Fortunately we had other methods to check that things were likely to work. 

MJM460
The more I learn, the more I find that I still have to learn!

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #58 on: November 21, 2019, 07:34:20 AM »
Hi guys -

My temporary lapse of thinking regarding the position of the displacement lubricator (now corrected above) notwithstanding, I believe I have a reasonably clear image in my head of the piping. However, the pipe cleaners mockup is a great idea. Don't think I have seen a pipe cleaner for decades but they are no doubt still out there (after all, what else would people clean their pipes with? While I suspect that pipe-smoking has gone into decline as vaping has ascended, surely it cannot be extinct!). Amazon is my friend...

Intriguing, MJM, that you would build small scale models of whole refineries using Blue Peter methods and materials.     :)

Hot in Australia, cold here in Britain. I tend to prefer the cold but a happy medium would be good...

Thanks both for your input.

gary

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #59 on: November 21, 2019, 08:11:20 AM »
Pipe cleaners ordered!

 

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